Supplemental Prospectus - Form 424B5

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-282260

PROSPECTUS SUPPLEMENT

(To prospectus dated October 2, 2024)

18,356,173 Shares of Common Stock

Pre-Funded Warrants to Purchase up to 4,931,507 Shares of Common Stock

We are offering 18,356,173 shares of our common stock, $0.001 par value per share, and, in lieu of shares of our common stock to certain investors that so choose, pre-funded warrants to purchase 4,931,507 shares of our common stock. The purchase price of each pre-funded warrant is the price per share at which shares of common stock are being sold in this offering, minus $0.001, and the exercise price of each pre-funded warrant is $0.001 per share of common stock. This prospectus supplement also relates to the offering of the shares of common stock issuable upon the exercise of such pre-funded warrants.

Our common stock is listed on The Nasdaq Capital Market under the symbol "ELDN." On October 28, 2024, the last reported sale price of our common stock was $3.37 per share. There is no established public trading market for the pre-funded warrants, and we do not expect a market to develop. In addition, we do not intend to apply for a listing of the pre-funded warrants on The Nasdaq Capital Market, any other national securities exchange or any other nationally recognized trading system.

Investing in our common stock involves a high degree of risk. Please read the "Risk Factors" beginning on page S-9 of this prospectus supplement and the risk factors included in the documents incorporated by reference into this prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus supplement. Any representation to the contrary is a criminal offense.

Delivery of the shares of common stock and pre-funded warrants is expected to be made on or about October 30, 2024.

Sole Bookrunning Manager

Leerink Partners

The date of this prospectus supplement is October 29, 2024

TABLE OF CONTENTS

In making your investment decision, you should rely only on the information contained in or incorporated by reference into this prospectus supplement, the accompanying prospectus or in any free writing prospectus prepared by or on behalf of us. Neither we nor the underwriters have authorized anyone to provide any information or to make any representations other than those contained or incorporated by reference into this prospectus supplement, the accompanying prospectus or in any free writing prospectus prepared by or on behalf of us. If anyone provides you with different or inconsistent information, you should not rely on it. Neither we nor the underwriters take responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you.

This prospectus supplement is an offer to sell only the securities offered hereby, but only under the circumstances and in the jurisdictions where it is lawful to do so. We are not, and the underwriters are not, making an offer to sell the securities described in this prospectus supplement in any jurisdiction in which an offer or solicitation is not authorized or in which the person making such offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make an offer or solicitation. Neither this prospectus supplement nor the accompanying prospectus constitutes an offer, or an invitation on our behalf or on behalf of the underwriters, to subscribe for and purchase any of the securities and may not be used for or in connection with any offer or solicitation by anyone, in any jurisdiction in which such an offer or solicitation is not authorized or to any person to whom it is unlawful to make such an offer or solicitation.

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The information contained in or incorporated by reference into this prospectus supplement, the accompanying prospectus or in any free writing prospectus prepared by or on behalf of us is current only as of the date of the applicable document, regardless of its time of delivery or any sale of shares of our common stock or pre-funded warrants. Our business, financial condition, results of operations and prospects may have changed since those dates.

For investors outside the United States: Neither we nor the underwriters have done anything that would permit this offering or possession or distribution of this prospectus supplement or the accompanying prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus supplement or the accompanying prospectus must inform themselves, and observe any restrictions relating to, the offering of the shares of common stock and pre-funded warrants and the distribution of this prospectus supplement and the accompanying prospectus outside the United States.

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ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offering and important business information about us, and also adds to and updates information contained in the accompanying prospectus dated October 2, 2024, which forms part of the registration statement on Form S-3, and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus. The second part, the accompanying prospectus, including the documents incorporated by reference, provides more general information some of which may not apply to this offering, and which contains and incorporates by reference important business and financial information about us and other information about this offering. This prospectus supplement and the accompanying prospectus are part of the registration statement on Form S-3 that we filed with the Securities and Exchange Commission (the "SEC"). Generally, when we refer to this prospectus supplement, we are referring to both parts of this document combined. Before you invest, you should carefully read this prospectus supplement, the accompanying prospectus, all information incorporated by reference herein and therein, as well as the additional information described under "Where You Can Find More Information" on page S-28 of this prospectus supplement. These documents contain information that you should consider when making your investment decision. To the extent that any statement that we make in this prospectus supplement is inconsistent with statements made in the accompanying prospectus or any documents incorporated by reference therein, the statements made in this prospectus supplement will be deemed to modify or supersede those made in the accompanying prospectus and such documents incorporated by reference therein.

Neither we nor the underwriters have authorized anyone to provide you with information that is different from that contained in this prospectus supplement or in any free writing prospectus we may authorize to be delivered or made available to you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We are offering to sell, and seeking offers to buy, shares of our common stock and pre-funded warrants only in jurisdictions where offers and sales are permitted. The distribution of this prospectus supplement and the offering of the common stock and pre-funded warrants in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus supplement must inform themselves about, and observe any restrictions relating to, the offering of the common stock and pre-funded warrants and the distribution of this prospectus supplement outside the United States. This prospectus supplement does not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus supplement by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

In this prospectus supplement, the terms "Eledon," "Company," "we," "us," "our" and similar terms refer to Eledon Pharmaceuticals, Inc. (formerly Novus Therapeutics, Inc.), a Delaware corporation, and its subsidiaries, unless the context otherwise requires. We use "ELDN" and other marks as trademarks within the United States and other countries. This prospectus supplement, the accompanying prospectus and the documents incorporated by reference contain references to our trademarks as well as third-party trademarks. Solely for convenience, trademarks and trade names, including logos, artwork and other visual displays, may appear without the ^® or TM symbols, but such references are not intended to indicate in any way that we will not assert, to the fullest extent under applicable law, our rights or the rights of the applicable licensor to these trademarks and trade names. We do not intend our use of third-party trade names or trademarks to imply a relationship with, or endorsement or sponsorship of us by, any other entity.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement and the information incorporated by reference in this prospectus supplement contains "forward-looking statements" as defined by the Private Securities Litigation Reform Act of 1995, which statements involve substantial risks and uncertainties. Any statements other than statements of historical or current fact in this prospectus supplement are forward looking statements. In some instances, you can identify forward-looking statements by the use of words such as "believes," "anticipates," "plans," "expects," "estimates," "intends," "predicts," "projects," "targets," "could," "may," "will," and other similar expressions, although not all forward-looking statements include such identifying words. Forward-looking statements include, but are not limited to statements about our future expectations, plans and prospects, including the development of product candidates, expected timing for initiation of future clinical trials, expected timing for receipt of data from clinical trials, expected or future results of tegoprubart trials, our capital resources and ability to finance planned clinical trials.

Forward-looking statements are inherently uncertain, and actual results may differ materially from those indicated by such forward-looking statements as a result of various factors, including: risks related to the sufficiency of our capital resources and ability to raise additional capital to finance our operations; including to fund planned clinical trials; our product development plans; uncertainties about the ability of tegoprubart to prevent rejection in connection with islet cell transplantation or kidney transplantation; expectations for and the timing of commencement, enrollment, completion, data, and release of results of clinical trials for our product candidates; our strategies with respect to our preclinical and clinical development programs, including our expectations regarding the production of clinical quantities of our product candidates; our plans, strategy and timing to obtain and maintain regulatory approvals of our product candidates; our expectations regarding competitive conditions for our product candidates; our review of strategic alternatives and the outcome of such review; our expectations about our future financial performance or condition; risks relating to the safety and efficacy of our drug candidates; risks relating to clinical development timelines, including interactions with regulators and clinical sides, as well as patient enrollment; risks relating to costs of clinical trials; risks of significant dilution to our stockholders as a results of issuances of our common stock, including common stock that may be issuable pursuant to outstanding warrants or other convertible securities; and other risks and uncertainties discussed in our most recent Annual Report on Form 10-K, as revised or supplemented by our subsequent Quarterly Reports on Form 10-Q, and other subsequent filings with the SEC, which can be found at www.sec.gov. Any forward-looking statements contained in this prospectus supplement speak only as of the date hereof and not as of any future date, and the Company expressly disclaims any intent to update any forward-looking statements, whether as a result of new information, future events or otherwise.

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RISK FACTORS

Investors should carefully consider the risks described on page 5 of the accompanying prospectus, as well as those risks described below and those included in the filings incorporated by reference before deciding whether to invest in our securities. The occurrence of any of these risks could harm our business, financial condition, results of operations and/or growth prospects or cause our actual results to differ materially from those contained in forward-looking statements we have made in this prospectus supplement, including the documents incorporated by reference, and those we may make from time to time. You should consider all of the risk factors described in our public filings when evaluating our business.

Risks Related to this Offering

We will have broad discretion over the use of the net proceeds from this offering and may apply such proceeds to uses that do not improve our operating results or the value of your securities.

We will have broad discretion to use the net proceeds to us from this offering, and investors will be relying solely on the judgment of our board of directors and management regarding the application of these proceeds. Although we expect to use the net proceeds from this offering to advance our pipeline and for working capital and general corporate purposes, we have not allocated these net proceeds for specific purposes. See "Use of Proceeds" for additional information. Investors will not have the opportunity, as part of their investment decision, to assess whether the proceeds are being used appropriately. Our use of the proceeds may not improve our operating results or increase the value of the securities being offered hereby.

You may experience immediate and substantial dilution in the pro forma net tangible book value of the common stock and/or the value of our pre-funded warrants you purchase in this offering. In addition, we may issue additional equity or convertible debt securities in the future, which may result in additional dilution to investors.

Since the price per share of our common stock and the value of our pre-funded warrants being offered in this offering is substantially higher than the pro forma net tangible book value per share of our outstanding common stock, you will suffer substantial dilution with respect to the net tangible book value of the common stock and/or the pre-funded warrants you purchase in this offering. Based on the public offering price of $3.65 per share, and after giving effect to the second and third closings under the Securities Purchase Agreement (as defined in the section titled "Dilution"), which occurred on July 8, 2024 and September 30 to October 1, 2024, respectively, and expiration of the Subsequent Closing Warrant (as defined in the section titled "Dilution") liabilities, if you purchase shares of our common stock and/or pre-funded warrants in this offering, you will experience immediate dilution of $1.50 per share with respect to the pro forma as adjusted net tangible book value of the common stock and/or the pre-funded warrants you purchased. See the section titled "Dilution" for a more detailed discussion of the dilution you will incur if you purchase common stock or pre-funded warrants in this offering. To the extent outstanding warrants and stock options are exercised, there will be further dilution to new investors. In addition, to the extent we need to raise additional capital in the future and we issue additional shares of common stock or securities convertible or exchangeable for our common stock, our then existing stockholders may experience dilution and the new securities may have rights senior to those of our common stock offered in this offering.

Our stock price is and may continue to be volatile and you may not be able to resell our securities at or above the price you paid.

The market price of our common stock could be subject to significant fluctuations. Market prices for securities of early-stage pharmaceutical, biopharmaceutical, and other life sciences companies have historically been particularly volatile. Some of the factors that may cause the market price of our common stock to fluctuate include: uncertainties regarding our financial condition and our ability to raise sufficient capital to fund our ongoing operations; our ability to obtain regulatory approvals for our product candidates or other product candidates, and delays or failures to obtain such approvals; failure of any of our product candidates, if approved, to achieve commercial success; issues in manufacturing our approved products, if any, or product candidates; the

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results of our current and any future clinical trials of our product candidates; uncertainties about the ability of tegoprubart to prevent rejection in connection with islet cell transplantation or kidney transplantation; the entry into, or termination of, key agreements, including key commercial partner agreements; the initiation of, material developments in, or conclusion of litigation to enforce or defend any of our intellectual property rights or defend against the intellectual property rights of others; announcements by commercial partners or competitors of new commercial products, clinical progress, or the lack thereof, significant contracts, commercial relationships, or capital commitments; the introduction of technological innovations or new therapies that compete with our potential products; the loss of key employees; changes in estimates or recommendations by securities analysts, if any, who cover our common stock; general and industry-specific economic conditions that may affect our research and development expenditures; changes in the structure of healthcare payment systems; period-to-period fluctuations in our financial results; and future issuances of shares of common stock. Moreover, the stock markets in general have experienced substantial volatility that has often been unrelated to the operating performance of individual companies. These broad market fluctuations may also adversely affect the trading price of our common stock. Each of these factors, among others, could harm your investment in our common stock and could result in your being unable to resell the common stock that you purchase at a price equal to or above the price you paid.

There is no public market for the pre-funded warrants being offered in this offering.

There is no public trading market for the pre-funded warrants being offered in this offering, and we do not expect a market to develop. In addition, we do not intend to list the pre-funded warrants on The Nasdaq Capital Market or any other national securities exchange or nationally recognized trading system. Without an active trading market, the liquidity of the pre-funded warrants will be limited. See the section titled "Description of Pre-Funded Warrants."

We will not receive any meaningful amount of additional funds upon the exercise of the pre-funded warrants.

Each pre-funded warrant will be exercisable until it is fully exercised and by means of payment of the nominal cash purchase price upon exercise or by means of a "cashless exercise" according to a formula set forth in the pre-funded warrant. Accordingly, we will not receive any meaningful additional funds upon the exercise of the pre-funded warrants.

Holders of the pre-funded warrants will have no rights as common stockholders until such holders exercise their pre-funded warrants and acquire shares of our common stock.

Until holders of the pre-funded warrants exercise their pre-funded warrants and acquire shares of our common stock, such holders will have no rights with respect to the shares of our common stock underlying such pre-funded warrants. Upon exercise of the pre-funded warrants, the holders will be entitled to exercise the rights of a common stockholder only as to matters for which the record date occurs after the exercise date.

Significant holders or beneficial holders of shares of our common stock may not be permitted to exercise the pre-funded warrants that they hold.

A holder of the pre-funded warrants will not be entitled to exercise any portion of any pre-funded warrant to the extent that, after giving effect to such exercise, the holder (together with the holder's affiliates, and any other persons acting as a group together with the holder or any of the holder's affiliates) would beneficially own in excess of 4.99% (or, at the holder's option upon issuance, 9.99%) of the number of shares of our common stock outstanding immediately after giving effect to the issuance of shares of common stock issuable upon exercise of such warrant, which percentage may be increased or decreased upon 61 days' prior notice (subject to a limit of 19.99% to the extent required under Nasdaq Marketplace Rules). As a result, you may not be able to exercise your pre-funded warrants for shares of our common stock at a time when it would be financially beneficial for you to do so. In such a circumstance, you could seek to sell your pre-funded warrants to realize value, but you may be unable to do so in the absence of an established trading market and due to applicable transfer restrictions. See the section titled "Description of Pre-Funded Warrants."

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USE OF PROCEEDS

We estimate that we will receive net proceeds of approximately $80 million, based on the public offering price of $3.65 per share and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us. We will receive nominal proceeds, if any, from the exercise of the pre-funded warrants.

We currently plan to use the net proceeds from this offering to advance our pipeline and for working capital and general corporate purposes. Our management will have broad discretion over the actual amounts and timing of the expenditure of the net proceeds from this offering within those categories, and accordingly, investors in this offering will need to rely upon the judgment of our management with respect to the use of proceeds.

Our expected use of proceeds from the sale of the securities offered hereby represents our current intentions based on our present plans and business condition. As of the date of this prospectus supplement, we cannot predict with certainty all of the particular uses for the proceeds to be received from the sale of the securities offered hereby or the amounts that we will actually spend on the uses set forth above.

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DILUTION

Purchasers of securities offered by this prospectus supplement and the accompanying prospectus will suffer immediate and substantial dilution to the extent of the difference between the public offering price per share and the pro forma as adjusted net tangible book value per share of our common stock immediately after this offering.

Our historical net tangible book value (deficit) as of June 30, 2024 was approximately ($40.9) million, or approximately ($1.06) per share of common stock. Net tangible book value (deficit) per share represents the amount of total tangible assets, excluding goodwill and intangible assets, less total liabilities, divided by the number of shares of our common stock, in each case as of the specified date. Net tangible book value (deficit) per share as of June 30, 2024 includes $120.8 million of liabilities associated with (i) certain common stock warrants (the "Common Warrants") issued by us in May 2023 pursuant to a Securities Purchase Agreement dated as of April 28, 2023 by and among us and certain institutional and accredited investors (the "Securities Purchase Agreement"), and (ii) the issuance of pre-funded warrants in lieu of additional shares of common stock (the "Subsequent Closing Warrants") which were issuable by us in a second closing and a third closing under the Securities Purchase Agreement. We record the Common Warrants and the Subsequent Closing Warrants as liabilities on our consolidated balance sheet at their fair value and remeasure the fair value for each on a quarterly basis. Liabilities related to the Subsequent Closing Warrants expired following the second and third closings under the Securities Purchase Agreement.

Our pro forma net tangible book value as of June 30, 2024 was approximately $59.7 million, or approximately $1.44 per share of common stock. Pro forma net tangible book value represents the amount of our total tangible assets, excluding goodwill and intangible assets, less our total liabilities and the effect of the second and third closings under the Securities Purchase Agreement, which occurred on July 8, 2024 and September 30 to October 1, 2024, respectively, and expiration of the Subsequent Closing Warrant liabilities. In connection with the second and third closings under the Securities Purchase Agreement, we did not issue any additional Subsequent Closing Warrants and, accordingly, our pro forma net tangible book value is presented without giving effect to $94.8 million of liabilities associated with the Subsequent Closing Warrants as of June 30, 2024, which expired in the third and fourth quarters of 2024.

After giving effect to the sale of shares of our common stock in this offering, at the public offering price of $3.65 per share of common stock, after deducting the underwriting discounts and commissions and other estimated offering expenses payable by us, and excluding shares of common stock issued and any proceeds received upon the exercise of the pre-funded warrants or any resulting accounting associated with the pre-funded warrants, our pro forma as adjusted net tangible book value as of June 30, 2024 would have been $139.3 million or $2.15 per share of common stock. This represents an immediate increase in pro forma as adjusted net tangible book value to existing stockholders of $0.71 per share of common stock and immediate dilution in pro forma as adjusted net tangible book value to investors purchasing common stock in this offering of $1.50 per share of common stock. Dilution per share to investors purchasing common stock in this offering is determined by subtracting pro forma as adjusted net tangible book value per share after this offering from the public offering price per share paid by those investors.

The following table illustrates this dilution on a per share basis:

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The above discussion and table are based on (i) with respect to the historical net tangible book value (deficit), 38,506,614 shares of our common stock outstanding as of June 30, 2024, and (ii) with respect to the pro forma as adjusted net tangible book value, 38,506,614 shares of our common stock outstanding as of June 30, 2024 plus 2,636,488 shares of common stock issued to purchasers in the second and third closings under the Securities Purchase Agreement and 240,000 shares of common stock issued upon exercise of pre-funded warrants (with total net proceeds of $5,784,105), and excludes as of June 30, 2024:

In addition, the number of shares outstanding immediately after this offering does not include shares of common stock that we may offer and sell from time to time pursuant to the Sales Agreement. After the expiration or waiver of the lock-up period applicable to us and described under the section of this prospectus supplement entitled "Underwriting," we may offer and sell shares of our common stock having an aggregate offering price of up to $75.0 million from time to time in "at-the-market" offerings pursuant to the Sales Agreement.

To the extent that any options are exercised, warrants are exercised, new options are issued under the 2020 Plan, additional shares of common stock are sold under the ESPP or we otherwise issue additional shares of common stock or convertible stock in the future, there will be further dilution to investors participating in this offering.

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DESCRIPTION OF PRE-FUNDED WARRANTS

The following is a brief summary of certain terms and conditions of the pre-funded warrants being offered in this offering. The following description is subject in all respects to the provisions contained in the pre-funded warrants.

Form

The pre-funded warrants will be issued as individual warrant agreements to the purchasers. The form of pre-funded warrant will be filed as an exhibit to a Current Report on Form 8-K that we will file with the SEC.

Term

The pre-funded warrants will not expire until they are fully exercised.

Exercisability

The pre-funded warrants are exercisable at any time after its original issuance. The pre-funded warrants will be exercisable, at the option of the holder, in whole or in part by delivering to us a duly executed exercise notice and by payment in full of the exercise price in immediately available funds for the number of shares of common stock purchased upon such exercise. As an alternative to payment in immediately available funds, the holder may, in its sole discretion, elect to exercise the pre-funded warrants through a cashless exercise, in which case the holder would receive upon such exercise the net number of shares of our common stock determined according to the formula set forth in the pre-funded warrants. No fractional shares of our common stock will be issued in connection with the exercise of a pre-funded warrants. In lieu of fractional shares, we will, at our election, either pay a cash adjustment in respect of such final fraction in an amount equal to such fraction multiplied by the Exercise Price (as defined in the pre-funded warrant) or round up to the next whole share.

Exercise Limitations

We may not effect the exercise of any pre-funded warrant, and a holder will not be entitled to exercise any portion of any pre-funded warrant to the extent that after giving effect to such exercise, the holder (together with the holder's affiliates, and any other persons acting as a group together with the holder or any of the holder's affiliates) would beneficially own in excess of 4.99% (or, at the holder's option upon issuance, 9.99%) of the number of shares of our common stock outstanding immediately after giving effect to the issuance of shares of common stock issuable upon exercise of such warrant). A holder, upon notice to the Company, may increase or decrease the beneficial ownership limitation under the pre-funded warrant, provided that to the extent required under Nasdaq Marketplace Rules, it in no event exceeds 19.99% of the number of shares of our common stock outstanding immediately after giving effect to the issuance of shares of common stock upon exercise of the warrant. Any such increase in the percentage will not be effective until the 61^st day after such notice is delivered to the Company.

Exercise Price

The exercise price of our shares of common stock purchasable upon the exercise of the pre-funded warrants is $0.001 per share. The exercise price of the pre-funded warrants and the number of shares of common stock issuable upon exercise of the pre-funded warrants is subject to appropriate adjustment in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting our shares of common stock.

Adjustments

In addition to the adjustments described under "Exercise Price" above, if we grant, issue or sell any common stock equivalents or rights to purchase stock, warrants, securities or other property pro rata to all record holders

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of any class of shares of our common stock or declare or make any dividend or other distribution of our assets (or rights to acquire our assets) to holders of shares of common stock, by way of return of capital or otherwise, then, in each case, each pre-funded warrant holder will be entitled to acquire such rights or participate in such distribution, on the same terms as the holder could have acquired or participated if the holder held the number of shares of common stock acquirable upon complete exercise of the pre-funded warrant without regard to any exercise limitations, subject to certain exceptions to the extent participation would result in the holder exceeding its beneficial ownership limitation under the pre-funded warrant.

Transferability

Subject to applicable laws, the pre-funded warrants may be offered for transferred or assigned without our consent, in accordance with the terms of the pre-funded warrants.

Exchange Listing

We do not intend to list the pre-funded warrants on The Nasdaq Capital Market, any other national securities exchange or any other nationally recognized trading system.

Fundamental Transactions

Upon the consummation of a fundamental transaction (as described in the pre-funded warrants, and generally including any merger or consolidation, any sale, lease, license, assignment, transfer conveyance or other disposition of all or substantially all of our assets, any purchase offer, tender offer or exchange offer accepted by the holders of 50% or more of the outstanding common stock, any reclassification, reorganization or recapitalization of the common stock or any compulsory share exchange, any stock or share purchase agreement or other business combination whereby another person or group acquires more than 50% of the outstanding shares of common stock), the holders of the pre-funded warrants will be entitled to receive, upon exercise of the pre-funded warrants, the kind and amount of securities, cash or other property that such holders would have received had they exercised the pre-funded warrants immediately prior to such fundamental transaction, without regard to any limitations on exercise contained in the pre-funded warrants.

No Rights as a Stockholder

Except by virtue of such holder's ownership of shares of our common stock, the holder of a pre-funded warrant does not have the rights or privileges of a holder of shares of our common stock, including any voting rights, until such holder exercises the pre-funded warrant.

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MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS

The following is a discussion of certain material U.S. federal income tax consequences of the acquisition, ownership and disposition of shares of common stock and pre-funded warrants issued pursuant to this offering. This discussion is limited to beneficial owners of the common stock or pre-funded warrants who hold the common stock or pre-funded warrants as a capital asset within the meaning of Section 1221 of the Internal Revenue Code of 1986, as amended (the "Code").

This summary is based upon U.S. federal income tax laws as of the date of this prospectus, which is subject to change or differing interpretations, possibly with retroactive effect. This discussion is a summary only and does not describe all of the tax consequences that may be relevant to you in light of your particular circumstances, including but not limited to the alternative minimum tax, the Medicare tax on certain net investment income and the different consequences that may apply if you are subject to special rules that apply to certain types of investors, including but not limited to:

If a partnership (including an entity or arrangement treated as a partnership or other pass-thru entity for U.S. federal income tax purposes) holds our common stock or pre-funded warrants, the tax treatment of a partner, member or other beneficial owner in such partnership will generally depend upon the status of the partner, member or other beneficial owner, the activities of the partnership and certain determinations made at the partner, member or other beneficial owner level. If you are a partner, member or other beneficial owner of a partnership holding our common stock or pre-funded warrants, you are urged to consult your tax advisor regarding the tax consequences to them.

This discussion is based on the Code, and administrative pronouncements, judicial decisions and final, temporary and proposed Treasury regulations as of the date of this offering, which are subject to change, possibly on a

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retroactive basis, and changes to any of which subsequent to the date of this prospectus may affect the tax consequences described herein. This discussion does not address any aspect of state, local or non-U.S. taxation, or any U.S. federal taxes other than income taxes (such as gift and estate taxes).

We have not sought, and do not expect to seek, a ruling from the U.S. Internal Revenue Service (the "IRS") as to any U.S. federal income tax consequence described herein. The IRS may disagree with the discussion herein, and its determination may be upheld by a court. Moreover, there can be no assurance that future legislation, regulations, administrative rulings or court decisions will not adversely affect the accuracy of the statements in this discussion. You are urged to consult your tax advisor with respect to the application of U.S. federal tax laws to your particular situation, as well as any tax consequences arising under the laws of any state, local or foreign jurisdiction.

THIS DISCUSSION IS ONLY A SUMMARY OF CERTAIN U.S. FEDERAL INCOME TAX CONSIDERATIONS ASSOCIATED WITH THE ACQUISITION, OWNERSHIP AND DISPOSITION OF OUR COMMON STOCK OR PRE-FUNDED WARRANTS. EACH PROSPECTIVE INVESTOR IN OUR COMMON STOCK OR PRE-FUNDED WARRANTS IS URGED TO CONSULT ITS OWN TAX ADVISOR WITH RESPECT TO THE PARTICULAR TAX CONSEQUENCES TO SUCH INVESTOR OF THE ACQUISITION, OWNERSHIP AND DISPOSITION OF OUR COMMON STOCK OR PRE-FUNDED WARRANTS, INCLUDING THE APPLICABILITY AND EFFECT OF ANY U.S. FEDERAL NON-INCOME, STATE, LOCAL, AND NON-U.S. TAX LAWS.

For purposes of this discussion, a "U.S. Holder" means a beneficial owner of our common stock or pre-funded warrants that is, for U.S. federal income tax purposes, any of the following:

For purposes of this discussion, a "Non-U.S. Holder" is a beneficial owner of our common stock or pre-funded warrants that is neither a U.S. Holder nor an entity treated as a partnership for U.S. federal income tax purposes.

General Treatment of Pre-Funded Warrants

Although the law in this area is not completely settled, the pre-funded warrants are generally expected to be treated as shares of our common stock for U.S. federal income tax purposes and a holder of pre-funded warrants should generally be taxed in the same manner as a holder of common stock as described below. You should discuss with your tax advisor the consequences of the purchase, ownership and disposition of the pre-funded warrants, as well as the exercise of, certain adjustments to, and any payments in respect of the pre-funded warrants (including potential alternative characterizations). The balance of this discussion generally assumes that the characterization described above is respected for U.S. federal income tax purposes.

Tax Considerations Applicable to U.S. Holders

Distributions

In general, any distributions we make to a U.S. Holder of shares of our common stock, to the extent paid out of our current or accumulated earnings and profits (as determined under U.S. federal income tax principles), will

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constitute dividends for U.S. federal income tax purposes. To the extent those distributions exceed both our current and our accumulated earnings and profits, the excess will constitute a return of capital and will first reduce a U.S. Holder's basis in our common stock, but not below zero, and then will be treated as gain from the sale of stock as described below under "Tax Considerations Applicable to U.S. Holders-Gain on Disposition of Our Common Stock or Pre-Funded Warrants." A preferential U.S. federal income tax rate may apply to any dividends paid to noncorporate U.S. Holders meeting certain holding period requirements.

The taxation of a distribution received with respect to a pre-funded warrant is unclear. It is possible such a distribution would be treated as a distribution on common stock as described in this section, although other treatments may also be possible. Prospective investors should consult their tax advisors regarding the proper treatment of any payments in respect of the prefunded warrants.

Gain on Disposition of Our Common Stock or Pre-Funded Warrants

Upon a sale or other taxable disposition of our common stock or pre-funded warrants, a U.S. Holder generally will recognize capital gain or loss in an amount equal to the difference between the amount realized and the U.S. Holder's adjusted tax basis in the common stock or pre-funded warrant. Capital gain or loss will constitute long-term capital gain or loss if such U.S. Holder's holding period for the common stock or pre-funded warrant exceeds one year. The deductibility of capital losses is subject to certain limitations. U.S. Holders who recognize losses with respect to a disposition of our common stock or prefunded warrants should consult their own tax advisors regarding the tax treatment of such losses.

Exercise of Pre-Funded Warrants

As discussed under the section titled "Description of Pre-Funded Warrants-Exercisability," a U.S. Holder may exercise the pre-funded warrant by payment of exercise price or through a cashless exercise. The U.S. federal income tax treatment of a cashless exercise of pre-funded warrants into our common stock is unclear, and a U.S. Holder should consult their own tax advisors regarding the U.S. federal income tax consequences of a cashless exercise of pre-funded warrants. In general, however, a U.S. Holder should not recognize gain or loss for U.S. federal income tax purposes upon exercise of a prefunded warrant pursuant to either method, except to the extent such U.S. Holder receives a cash payment for a fractional share that would otherwise have been issuable upon exercise of the pre- funded warrant, which will be treated as a sale subject to the rules described above under "Tax Considerations Applicable to U.S. Holders-Gain on Disposition of Our Common Stock or Pre-Funded Warrants." A U.S. Holder's initial tax basis in the share of common stock received upon exercise of the prefunded warrant generally should be equal to the sum of (i) such U.S. Holder's tax basis in the pre-funded warrant and (ii) the exercise price paid or treated as paid by such U.S. Holder on the exercise of the pre-funded warrant. A U.S. Holder's holding period in the common stock received upon exercise generally should include such U.S. Holder's holding period in the prefunded warrants exchanged therefor.

Certain Adjustments to the Pre-Funded Warrants

Under Section 305 of the Code, an adjustment to the number of shares of common stock that will be issued on the exercise of the pre-funded warrants, or an adjustment to the exercise price of the pre-funded warrants, may be treated as a constructive distribution to a U.S. Holder of the pre-funded warrants if, and to the extent that, such adjustment has the effect of increasing your proportionate interest in our earnings and profits or assets, depending on the circumstances of such adjustment (for example, if such adjustment is to compensate for a distribution of cash or other property to our shareholders). Any such adjustment that is treated as a constructive distribution would be treated as a dividend to the extent described above under "Tax Considerations Applicable to U.S. Holders-Distributions." U.S. Holders should consult their tax advisor regarding the proper tax treatment of any such adjustment.

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Lapse of Pre-Funded Warrants

If a U.S. Holder allows a pre-funded warrant to expire unexercised, such U.S. Holder will recognize a capital loss in an amount equal to such U.S. Holder's tax basis in pre-funded warrant. Any such loss generally will be a long-term capital loss if the pre-funded warrant is held for more than one year. The deductibility of capital losses is subject to certain limitations.

Information Reporting and Backup Withholding

Information reporting requirements generally will apply to payments of dividends (including constructive dividends) on the common stock or pre-funded warrants and to the proceeds of a sale or other disposition of common stock or prefunded warrants paid by us to you unless you are an exempt recipient, such as certain corporations. Backup withholding (currently at a rate of 24%) will apply to those payments if a U.S. Holder fails to provide their taxpayer identification number, or certification of exempt status, or if a U.S. Holder otherwise fails to comply with applicable requirements to establish an exemption.

Backup withholding is not an additional tax. Rather, any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against a U.S. Holder's U.S. federal income tax liability, if any, provided the required information is timely furnished to the IRS. Prospective investors should consult their own tax advisors regarding their qualification for exemption from information reporting and backup withholding and the procedure for obtaining such exemption.

Tax Considerations Applicable to Non-U.S. Holders

Distributions

In general, any distributions we make to a Non-U.S. Holder of shares of our common stock, to the extent paid out of our current or accumulated earnings and profits (as determined under U.S. federal income tax principles), will constitute dividends for U.S. federal income tax purposes and, provided such dividends are not effectively connected with the Non-U.S. Holder's conduct of a trade or business within the United States, we will be required to withhold tax from the gross amount of the dividend at a rate of 30%, unless such Non-U.S. Holder is eligible for a reduced rate of withholding tax under an applicable income tax treaty and provides proper certification of its eligibility for such reduced rate (usually on an IRS Form W-8BEN or W-8BEN-E). Any distribution not constituting a dividend will be treated first as reducing (but not below zero) the Non-U.S. Holder's adjusted tax basis in its shares of our common stock and, to the extent such distribution exceeds the Non-U.S. Holder's adjusted tax basis, as gain realized from the sale or other disposition of the common stock, which will be treated as described under "Tax Considerations Applicable to Non-U.S. Holders-Gain on Disposition of Our Common Stock or Pre-Funded Warrants" below. In addition, if we determine that we are likely to be classified as a "United States real property holding corporation" (a "USRPHC") (as described below), we generally will withhold 15% of any distribution that exceeds our current and accumulated earnings and profits.

The withholding tax generally does not apply to dividends paid to a Non-U.S. Holder who provides a Form W-8ECI, certifying that the dividends are effectively connected with the Non-U.S. Holder's conduct of a trade or business within the United States. Instead, the effectively connected dividends will be subject to regular U.S. federal income tax as if the Non-U.S. Holder were a U.S. resident, subject to an applicable income tax treaty providing otherwise. A corporate Non-U.S. Holder receiving effectively connected dividends may also be subject to an additional "branch profits tax" imposed at a rate of 30% (or a lower applicable treaty rate).

The taxation of a distribution received with respect to a pre-funded warrant is unclear. It is possible such a distribution would be treated as a distribution as described in this section, although other treatments may also be possible. Prospective investors should consult their tax advisors regarding the proper treatment of any payments in respect of the pre-funded warrants.

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Gain on Disposition of Our Common Stock or Pre-Funded Warrants

Subject to the discussions below on backup withholding and FATCA, a Non-U.S. Holder will not be subject to U.S. federal income tax on any gain realized upon the sale or other disposition of our common stock or pre-funded warrants unless:

Gain described in the first bullet point above will generally be subject to U.S. federal income tax on a net income basis at the regular graduated U.S. federal income tax rates. A Non-U.S. Holder that is a foreign corporation also may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on such effectively connected gain, as adjusted for certain items.

A Non-U.S. Holder described in the second bullet point above will be subject to U.S. federal income tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on any gain derived from the disposition, which may be offset by certain U.S. source capital losses of the Non-U.S. Holder (even though the individual is not considered a resident of the U.S.) provided the Non-U.S. Holder has timely filed U.S. federal income tax returns with respect to such losses.

With respect to the third bullet point above, we believe we are not currently and do not anticipate becoming a USRPHC. Because the determination of whether we are a USRPHC depends on the fair market value of our USRPIs relative to the fair market value of our other business assets and our non-U.S. real property interests, however, there can be no assurance we are not a USRPHC or will not become one in the future. Even if we are or were to become a USRPHC, gain arising from the sale or other taxable disposition by a Non-U.S. Holder of our common stock will not be subject to U.S. federal income tax if our common stock is "regularly traded," as defined by applicable Treasury Regulations, on an established securities market such as the Nasdaq Global Select Market, and such Non-U.S. Holder owned, actually and constructively, 5% or less of our common stock throughout the shorter of the five-year period ending on the date of the sale or other taxable disposition or the Non-U.S. Holder's holding period. Special rules may apply to Non-U.S. Holders of pre-funded warrants, who should consult their tax advisors.

Non-U.S. Holders should consult their tax advisors regarding potentially applicable income tax treaties that may provide for different rules.

Exercise of Pre-Funded Warrants

As discussed under the section titled "Description of Pre-Funded Warrants-Exercisability," a Non-U.S. holder may exercise the pre-funded warrant by payment of the exercise price or through a cashless exercise. The U.S. federal income tax treatment of a cashless exercise of pre-funded warrants into our common stock is unclear, and Non-U.S. holder's should consult their own tax advisors regarding the U.S. federal income tax consequences of a cashless exercise of pre-funded warrants. In general, however, a Non-U.S. holder should not recognize gain or loss for U.S. federal income tax purposes upon exercise of a pre-funded warrant pursuant to either method, except to the extent such Non-U.S. holder receives a cash payment for a fractional share that would otherwise have been issuable upon exercise of the pre-funded warrant, which will be treated as a sale subject to the rules described above under "Tax Considerations Applicable to Non-U.S. Holders-Gain on Disposition of Our Common Stock or Pre-Funded Warrants."

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Certain Adjustments to the Pre-Funded Warrants

Under Section 305 of the Code, an adjustment to the number of shares of common stock that will be issued on the exercise of the pre-funded warrants, or an adjustment to the exercise price of the pre-funded warrants, may be treated as a constructive distribution to a Non-U.S. Holder of the pre-funded warrants if, and to the extent that, such adjustment has the effect of increasing such Non-U.S. Holder's proportionate interest in our "earnings and profits" or assets, depending on the circumstances of such adjustment (for example, if such adjustment is to compensate for a distribution of cash or other property to our shareholders). Any such adjustment that is treated as a constructive distribution would be treated as a dividend, subject to withholding, to the extent described above under "Tax Considerations Applicable to Non-U.S. Holders-Distributions." Non-U.S. Holders should consult their tax advisor regarding the proper tax treatment of any such adjustment.

Information Reporting and Backup Withholding

Subject to the discussion below on FATCA, a Non-U.S. Holder will not be subject to backup withholding with respect to distributions we make on our common stock or pre-funded warrants to the Non-U.S. Holder, provided the applicable withholding agent does not have actual knowledge or reason to know such holder is a U.S. person and the holder certifies its non-U.S. status, such as by providing a valid IRS Form W-8BEN,W-8BEN-E or W-8ECI, or other applicable certification. However, information returns generally will be filed with the IRS in connection with any distributions (including deemed distributions) made on our common stock or pre-funded warrants to the Non-U.S. Holder, regardless of whether any tax was actually withheld. Copies of these information returns may also be made available under the provisions of a specific treaty or agreement to the tax authorities of the country in which the Non-U.S. Holder resides or is established.

Information reporting and backup withholding (currently at a rate of 24%) may apply to the proceeds of a sale or other taxable disposition of our common stock or pre-funded warrants within the U.S., and information reporting may (although backup withholding generally will not) apply to the proceeds of a sale or other taxable disposition of our common stock or pre-funded warrants outside the U.S. conducted through certain U.S.-related financial intermediaries, in each case, unless the beneficial owner certifies under penalty of perjury that it is a Non-U.S. Holder on IRS Form W-8BEN or W-8BEN-E, or other applicable form (and the payor does not have actual knowledge or reason to know that the beneficial owner is a U.S. person) or such owner otherwise establishes an exemption. Proceeds of a disposition of our common stock or pre-funded warrants conducted through a non-U.S. office of a non-U.S. broker generally will not be subject to backup withholding or information reporting.

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against a Non-U.S. Holder's U.S. federal income tax liability, provided the required information is timely furnished to the IRS.

FATCA Withholding Taxes

Provisions commonly referred to as "FATCA" impose withholding of 30% on payments of dividends on our common stock or pre-funded warrants to "foreign financial institutions" (which is broadly defined for this purpose and in general includes investment vehicles) and certain other non-U.S. entities unless various U.S. information reporting and due diligence requirements (generally relating to ownership by United States persons of interests in or accounts with those entities) have been satisfied by, or an exemption applies to, the payee (typically certified as to by the delivery of a properly completed IRS Form W-8BEN-E). Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the United States governing FATCA may be subject to different rules. Under certain circumstances, a Non-U.S. Holder might be eligible for refunds or credits of such withholding taxes, and a Non-U.S. Holder might be required to file a U.S. federal income tax return to claim such refunds or credits. Thirty percent withholding under FATCA was scheduled to apply to payments of gross proceeds from the sale or other disposition of property that produces U.S.-source interest or dividends beginning on January 1, 2019, but on December 13, 2018, the IRS released proposed

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regulations that, if finalized in their proposed form, would eliminate the obligation to withhold on gross proceeds. Such proposed regulations also delayed withholding on certain other payments received from other foreign financial institutions that are allocable, as provided for under final Treasury regulations, to payments of U.S.-source dividends, and other fixed or determinable annual or periodic income. Although these proposed Treasury regulations are not final, taxpayers generally may rely on them until final Treasury regulations are issued. Prospective investors should consult their tax advisors regarding the effects of FATCA on their investment in our common stock or pre-funded warrants.

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UNDERWRITING

Leerink Partners LLC is acting as representative of each of the underwriters named below and as sole bookrunning manager for this offering. Subject to the terms and conditions set forth in the underwriting agreement among us and the underwriters, we have agreed to sell to the underwriters, and each of the underwriters has agreed, severally and not jointly, to purchase from us, the number of shares of common stock and pre-funded set forth opposite its name below.

Subject to the terms and conditions set forth in the underwriting agreement, the underwriters have agreed, severally and not jointly, to purchase all of the shares of common stock and pre-funded warrants sold under the underwriting agreement if any of the shares of common stock or pre-funded warrants are purchased. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the non-defaulting underwriters may be increased or the underwriting agreement may be terminated.

We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriters may be required to make in respect of those liabilities.

The underwriters are offering the shares of common stock and pre-funded warrants, subject to prior sale, when, as and if issued to and accepted by them, subject to approval of legal matters by their counsel, including the validity of the shares of common stock and pre-funded warrants, and subject to other conditions contained in the underwriting agreement, such as the receipt by the underwriters of officers' certificates and legal opinions. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part.

Discounts and Commissions

The representative has advised us that the underwriters propose to initially offer the shares of common stock and pre-funded warrants to the public at the initial public offering price set forth on the cover page of this prospectus supplement and to dealers at that price less a concession not in excess of $0.1314 per share. After the initial offering of the shares of common stock and pre-funded warrants, the public offering price, concession or any other term of the offering may be changed by the representative.

The following table shows the initial public offering price, underwriting discounts and commissions and proceeds, before expenses, to us.

We estimate expenses payable by us in connection with this offering, other than the underwriting discounts and commissions referred to above, will be approximately $355,000. We also have agreed to reimburse the underwriters for up to $10,000 for their FINRA counsel fee. In accordance with FINRA Rule 5110, this reimbursed fee is deemed underwriting compensation for this offering.

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In addition, Noble Capital Markets, Inc. and Ceros Financial Services, Inc. provided us financial advisory services in connection with this offering and received an advisory fee as compensation for such services.

No Sales of Similar Securities

We, our executive officers and directors have agreed not to sell or transfer any common stock or securities convertible into or exchangeable or exercisable for common stock, for 90 days after the date of this prospectus supplement without first obtaining the written consent of Leerink Partners LLC on behalf of the underwriters. Specifically, we and these other persons have agreed, with certain limited exceptions, not to directly or indirectly:

The lock-up provisions apply to common stock and to securities convertible into or exchangeable or exercisable for common stock. They also apply to common stock owned now or acquired later by the person executing the lock-up agreement or for which the person executing the lock-up agreement later acquires the power of disposition.

Nasdaq Capital Market Listing

Our common stock is listed on The Nasdaq Capital Market under the symbol "ELDN."

Price Stabilization, Short Positions and Penalty Bids

Until the distribution of the securities is completed, SEC rules may limit underwriters and selling group members from bidding for and purchasing our common stock. However, the representative may engage in transactions that stabilize the price of the common stock, such as bids or purchases to peg, fix or maintain that price.

In connection with this offering, the underwriters may purchase and sell our common stock in the open market. These transactions may include short sales, purchases on the open market to cover positions created by short sales and stabilizing transactions. Short sales involve the sale by the underwriters of a greater number of shares than they are required to purchase in this offering. Because we have not granted the underwriters an option to purchase additional ordinary shares, the underwriters must close out any short positions by purchasing ordinary shares in the open market. The underwriters must close out any naked short position by purchasing shares in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of our common stock in the open market after pricing that could adversely affect investors who purchase in this offering. Stabilizing transactions consist of various bids for or purchases of shares of common stock made by the underwriters in the open market prior to the closing of this offering.

The underwriters may also impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discount received by it because the representative has repurchased shares sold by or for the account of such underwriter in stabilizing or short covering transactions.

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Similar to other purchase transactions, the underwriters' purchases to cover the syndicate short sales may have the effect of raising or maintaining the market price of our common stock or preventing or retarding a decline in the market price of our common stock. As a result, the price of our common stock may be higher than the price that might otherwise exist in the open market. The underwriters may conduct these transactions on The Nasdaq Capital Market, in the over-the-counter market or otherwise.

Neither we nor any of the underwriters make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of our common stock. In addition, neither we nor any of the underwriters make any representation that the representative will engage in these transactions or that these transactions, once commenced, will not be discontinued without notice. The underwriters may also engage in passive market making transactions in our common stock on The Nasdaq Capital Market in accordance with Rule 103 of Regulation M during a period before the commencement of offers or sales of securities in this offering and extending through the completion of distribution. A passive market maker must display its bid at a price not in excess of the highest independent bid of that security. However, if all independent bids are lowered below the passive market maker's bid, that bid must then be lowered when specified purchase limits are exceeded.

Electronic Distribution

In connection with this offering, certain of the underwriters or securities dealers may distribute prospectuses by electronic means, such as e-mail.

Other Relationships

The underwriters and certain of their affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. Some of the underwriters and certain of their affiliates may in the future engage in investment banking and other commercial dealings in the ordinary course of business with us and our affiliates, for which they may in the future receive customary fees, commissions and expenses.

In addition, in the ordinary course of their business activities, the underwriters and their affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

Selling Restrictions

Notice to Prospective Investors in the European Economic Area

In relation to each Member State of the European Economic Area (each, a "Relevant State"), no securities have been offered or will be offered pursuant to the offering to the public in that Relevant State prior to the publication of a prospectus in relation to the securities which has been approved by the competent authority in that Relevant State or, where appropriate, approved in another Relevant State and notified to the competent authority in that Relevant State, all in accordance with the Prospectus Regulation, except that securities may be offered to the public in that Relevant State at any time:

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provided that no such offer of securities shall require us or any of the representatives to publish a prospectus pursuant to Article 3 of the Prospectus Regulation or supplement a prospectus pursuant to Article 23 of the Prospectus Regulation.

For the purposes of this provision, the expression an "offer to the public" in relation to any securities in any Relevant State means the communication in any form and by any means of sufficient information on the terms of the offer and any securities to be offered so as to enable an investor to decide to purchase or subscribe for any securities, and the expression "Prospectus Regulation" means Regulation (EU) 2017/1129, as amended.

Notice to Prospective Investors in the United Kingdom

No securities have been offered or will be offered pursuant to the offering to the public in the United Kingdom prior to the publication of a prospectus in relation to the securities which has been approved by the Financial Conduct Authority, except that the securities may be offered to the public in the United Kingdom at any time:

provided that no such offer of the securities shall require us or any representative to publish a prospectus pursuant to Section 85 of the FSMA or supplement a prospectus pursuant to Article 23 of the UK Prospectus Regulation. For the purposes of this provision, the expression an "offer to the public" in relation to the securities in the United Kingdom means the communication in any form and by any means of sufficient information on the terms of the offer and any securities to be offered so as to enable an investor to decide to purchase or subscribe for any securities and the expression "UK Prospectus Regulation" means Regulation (EU) 2017/1129 as it forms part of domestic law by virtue of the European Union (Withdrawal) Act 2018.

Notice to Prospective Investors in Canada

The securities may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the securities must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser's province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser's province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

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LEGAL MATTERS

The validity of the securities offered hereby will be passed upon for us by O'Melveny & Myers LLP, Newport Beach, California. Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., Boston, Massachusetts, is acting as counsel for the underwriters in connection with this offering.

EXPERTS

KMJ Corbin & Company LLP, an independent registered public accounting firm, has audited our consolidated financial statements as of December 31, 2023 and 2022, and for each of the two years in the period ended December 31, 2023, included in Amendment No. 2 to the Annual Report on Form 10-K/A for the year ended December 31, 2023, as set forth in their report, which is incorporated by reference in this prospectus. Our consolidated financial statements are incorporated by reference in reliance on KMJ Corbin & Company LLP's report, given on their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and special reports, proxy statements and other information with the SEC, and we have filed with the SEC a registration statement on Form S-3 under the Securities Act with respect to the securities offered by this prospectus. This prospectus supplement, which forms part of the registration statement, does not contain all of the information included in the registration statement, including its exhibits and schedules. For further information about us and the securities described in this prospectus supplement, you should refer to the registration statement, its exhibits and schedules and our reports, proxies, information statements and other information filed with the SEC.

Our filings are available to the public on the Internet, through a database maintained by the SEC at www.sec.gov. We also maintain a website at www.eledon.com. We have included our website address for the information of prospective investors and do not intend it to be an active link to our website. Information contained on our website does not constitute a part of this prospectus supplement, the accompanying prospectus, or any applicable prospectus supplement (or any document incorporated by reference herein or therein).

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to "incorporate by reference" into this prospectus supplement the information we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this prospectus supplement, and information that we file later with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below, except for any document or portion thereof deemed to be "furnished" and not filed in accordance with SEC rules:

In addition, any future filings made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act subsequent to the date of the registration statement of which this prospectus forms a part and prior to its effectiveness and following its effectiveness until the end of the offering of the securities offered hereby, except for any document or portion thereof deemed to be "furnished" and not filed in accordance with SEC rules, shall be deemed to be incorporated by reference into this prospectus supplement.

You should rely only on the information incorporated by reference or provided in this prospectus supplement or the accompanying prospectus. We have not authorized anyone else to provide you with different information. You should not assume that the information in this prospectus supplement or the accompanying prospectus is accurate as of any date other than the date on the front page of those documents.

We will provide to each person, including any beneficial owner, to whom a prospectus supplement or accompanying prospectus is delivered, a copy of any or all of the information that is incorporated by reference in the prospectus supplement and accompanying prospectus, including exhibits to these documents. You may request a copy of these filings, at no cost, by contacting us, either orally or in writing, at Eledon Pharmaceuticals, Inc., 19800 MacArthur Boulevard, Suite 250, Irvine, California, (949) 238-8090.

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PROSPECTUS

$250,000,000

Common Stock

Preferred Stock

Debt Securities

Warrants

Units

From time to time, we may issue, in one or more offerings, up to $250,000,000 in aggregate principal amount of our common stock, preferred stock, debt securities, warrants and/or units, at prices and on terms that we will determine at the time of the offering.

This prospectus provides you with a general description of the securities we may offer. Each time we offer securities, we will provide specific terms of the securities offered in a supplement to this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. The prospectus supplement and any related free-writing prospectus may also add, update or change information contained in this prospectus. We may not sell any securities under this prospectus without delivery of the applicable prospectus supplement. If information in any prospectus supplement is inconsistent with the information in this prospectus, then the information in such prospectus supplement will apply and will supersede the information in this prospectus.

You should read this prospectus, the applicable prospectus supplement and any related free-writing prospectus carefully, as well as any documents incorporated by reference, before you invest in any of the securities being offered.

Our shares of common stock are listed on The Nasdaq Capital Market under the symbol "ELDN". The last reported sale price of our common stock on September 19, 2024 was $2.48 per share.

Investing in our securities involves a high degree of risk. Please read the information contained in and incorporated by referenced under the heading "Risk Factors" beginning on page 5 of this prospectus, and any applicable prospectus supplement, and under similar headings in the other documents that are incorporated by reference into this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Prospectus dated October 2, 2024

Table of Contents

i

ABOUT THIS PROSPECTUS

This prospectus is a part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission (the "SEC") utilizing a "shelf" registration process. Under this shelf registration process, we may sell any combination of the securities described in this prospectus in one or more offerings up to a total dollar amount of $250,000,000. This prospectus provides you with a general description of the securities we may offer.

Each time we sell securities under this prospectus, we will provide a prospectus supplement that will contain specific information about the terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. The prospectus supplement and any related free writing prospectus that we may authorize to be provided to you may also add, update or change information contained in this prospectus or in any documents that we have incorporated by reference into this prospectus. You should carefully read both this prospectus and any prospectus supplement together with additional information under the headings "Where You Can Find More Information" and "Incorporation of Certain Information by Reference."

We have not authorized anyone to provide you with any information other than that contained or incorporated by reference in this prospectus and any applicable prospectus supplement, along with the information contained in any free writing prospectuses we have authorized for use in connection with a specific offering. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. This prospectus is an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. This prospectus, any applicable supplement to this prospectus or any related free writing prospectus do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the registered securities to which they relate, nor do this prospectus, any applicable supplement to this prospectus or any related free writing prospectus constitute an offer to sell or the solicitation of an offer to buy securities in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction.

You should not assume that the information contained in this prospectus, any applicable prospectus supplement or any related free writing prospectus is accurate on any date subsequent to the date set forth on the front of the document or that any information we have incorporated by reference is correct on any date subsequent to the date of the document incorporated by reference, even though this prospectus, any applicable prospectus supplement or any related free writing prospectus is delivered, or securities are sold, on a later date.

Unless the context otherwise requires, we use the terms "Eledon," "company," "we," "us," and "our" in this prospectus to refer to Eledon Pharmaceuticals, Inc. and, where appropriate, our subsidiaries.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and the information incorporated by reference in this prospectus contains "forward-looking statements" as defined by the Private Securities Litigation Reform Act of 1995, which statements involve substantial risks and uncertainties. Any statements other than statements of historical or current fact in this prospectus are forward looking statements. In some instances, you can identify forward-looking statements by the use of words such as "believes," "anticipates," "plans," "expects," "estimates," "intends," "predicts," "projects," "targets," "could," "may," "will," and other similar expressions, although not all forward-looking statements include such identifying words. Forward-looking statements include, but are not limited to, statements about our future expectations, plans and prospects, including statements about planned clinical trials, the development of product candidates, expected timing for initiation of future clinical trials, expected timing for receipt of data from clinical trials, our capital resources and ability to finance planned clinical trials.

Forward-looking statements are inherently uncertain, and actual results may differ materially from those indicated by such forward-looking statements as a result of various factors, including: risks related to the sufficiency of our capital resources and ability to raise additional capital to finance our operations; including to fund planned clinical trials; our product development plans; expectations for and the timing of commencement, enrollment, completion, data, and release of results of clinical trials for our product candidates; our strategies with respect to our preclinical and clinical development programs, including our expectations regarding the production of clinical quantities of our product candidates; our plans, strategy and timing to obtain and maintain regulatory approvals of our product candidates; our expectations regarding competitive conditions for our product candidates; our review of strategic alternatives and the outcome of such review; our expectations about our future financial performance or condition; risks relating to the safety and efficacy of our drug candidates; risks relating to clinical development timelines, including interactions with regulators and clinical sides, as well as patient enrollment; risks relating to costs of clinical trials; risks of significant dilution to our stockholders as a results of issuances of our common stock, including common stock that may be issuable pursuant to outstanding warrants or other convertible securities; and other risks and uncertainties discussed in our most recent Annual Report on Form 10-K, as revised or supplemented by our subsequent Quarterly Reports on Form 10-Q, and other subsequent filings with the SEC, which can be found at www.sec.gov. Any forward-looking statements contained in this prospectus speak only as of the date hereof and not as of any future date, and the Company expressly disclaims any intent to update any forward-looking statements, whether as a result of new information, future events or otherwise.

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THE COMPANY

Eledon Pharmaceuticals, Inc. ("Eledon" or the "Company") is a clinical stage biopharmaceutical company using its immunology expertise in targeting the CD40 Ligand (CD40L, also called CD154) pathway to develop therapies to protect transplanted organs and prevent rejection, and to treat amyotrophic lateral sclerosis ("ALS"). Our lead compound in development is tegoprubart, an IgG1, anti-CD40L antibody with high affinity for CD40 Ligand, a well-validated biological target that we believe has broad therapeutic potential.

Tegoprubart is engineered to potentially both improve safety and provide pharmacokinetic, pharmacodynamic, and dosing advantages compared to other anti-CD40 approaches. The CD40L/CD40 pathway is recognized for its prominent role in immune regulation. CD40L is primarily expressed on activated CD4+ T cells, platelets and endothelial cells while the CD40 receptor is constitutively expressed on antigen presenting cells such as macrophages and dendritic cells, as well as B cells. By blocking CD40L and not the CD40 receptor, tegoprubart inhibits both the CD40 and CD11 costimulatory signaling pathways, providing the potential for improved efficacy compared to anti-CD40 receptor approaches. Blocking CD40L also increases polarization of CD4+ lymphocytes to Tregs, a specialized subpopulation of T cells that act to suppress an immune response, thus creating a more tolerogenic environment, which may play a therapeutic role in autoimmune diseases and in the prevention of allograft rejection after solid organ transplantation.

Tegoprubart is designed to negate the risk of thrombolytic events seen in the first generation of anti-CD40L antibodies by introducing structural modifications that have been shown in preclinical models to eliminate binding to the Fcg receptors associated with platelet activation without altering the binding of tegoprubart to CD40L. In non-human primate studies, dosing of tegoprubart up to 200 mg/kg per week for 26 weeks, demonstrated no adverse events regarding coagulation, platelet activation or thromboembolism.

Our business strategy is to optimize the clinical and commercial value of tegoprubart and become a global biopharmaceutical company with a focused immunology franchise. Our strategy is to develop tegoprubart for the prevention of allograft and xenograft rejection, and for the treatment of autoimmune diseases such as ALS. We selected our indications based on preclinical and clinical data that was generated with either tegoprubart or historical anti-CD40L molecules. In January 2023, we announced our decision to prioritize resources on our kidney transplantation programs, and discontinue funding of the islet cell transplantation program and the IgAN program. We remain committed to further progressing ALS clinical development and are working with key stakeholders on potential next steps to do so.

While inhibition of CD40L has shown it may play an important role in immunosuppression in allograft kidney transplantation, this mechanism of action has also demonstrated that it may be a promising option in xenotransplantation (i.e., transplanting an organ from an animal to a human). In January 2023, we entered into a non-exclusive collaborative research agreement with eGenesis, Inc. ("eGenesis"), under which eGenesis gained access to tegoprubart for preclinical and clinical xenotransplantation studies in support of eGenesis' kidney, heart and islet xenotransplantation programs.

Corporate Information

Otic Pharma, Ltd. ("Otic") was founded in the State of Israel in 2008. In 2015, Otic established U.S. operations and moved its corporate headquarters to Irvine, California. In 2017, Otic consummated a reverse merger with Tokai Pharmaceuticals, Inc. ("Tokai"), a Delaware corporation that was incorporated on March 26, 2004, pursuant to which, among other things, Tokai purchased from Otic and its stockholders all of the outstanding common and preferred shares of Otic in exchange for the issuance of a certain number of shares of common stock of Tokai (the "Reverse Merger"). Following the Reverse Merger, Tokai changed its name to Novus Therapeutics, Inc. On September 14, 2020, we acquired Anelixis Therapeutics, Inc. ("Anelixis"), a Delaware corporation, after which Anelixis became a wholly owned subsidiary of the Company. On January 4, 2021, we changed our name from Novus Therapeutics, Inc. to Eledon Pharmaceuticals, Inc.

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Our executive offices are located at 19800 MacArthur Boulevard, Suite 250, Irvine, California 92612. We also have a research and development office in Burlington, Massachusetts. Our telephone number is (949) 238-8090 and our website is www.eledon.com. We do not incorporate the information on or accessible through our website into this prospectus or the accompanying prospectus supplement, and you should not consider any information on, or that can be accessed through, our website as part of this prospectus or the accompanying prospectus supplement.

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RISK FACTORS

Investing in our securities involves risks. You should carefully consider the risks, uncertainties and other factors described in our most recent Annual Report on Form 10-K and subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, and in other documents which are incorporated by reference into this prospectus, as well as the risk factors and other information contained in or incorporated by reference into any accompanying prospectus supplement before investing in any of our securities. Our business, financial condition, results of operations, cash flows or prospects could be materially and adversely affected by any of these risks. The risks and uncertainties described in the documents incorporated by reference herein are not the only risks and uncertainties that you may face.

For more information about our SEC filings, please see the sections entitled "Where You Can Find More Information" and "Incorporation of Certain Information by Reference" below.

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USE OF PROCEEDS

We will retain broad discretion over the use of the net proceeds from the sale of the securities offered hereby. Unless otherwise specified in a prospectus supplement accompanying this prospectus, the net proceeds from the sale by us of the securities to which this prospectus relates will be used for working capital and general corporate purposes. Our expected use of proceeds from the sale of the securities offered hereby represents our current intentions based on our present plans and business condition. As of the date of this prospectus, we cannot predict with certainty all of the particular uses for the proceeds to be received from the sale of the securities offered hereby or the amounts that we will actually spend on the uses set forth above.

When we offer and sell the securities to which this prospectus relates, the prospectus supplement related to such offering will set forth our intended use of the proceeds, if any, received from the sale of such securities.

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DESCRIPTION OF CAPITAL STOCK

The following description of our capital stock is intended as a summary only and therefore is not a complete description of our capital stock. This description is based upon, and is qualified by reference to, our restated certificate of incorporation, as amended ("certificate of incorporation"), our amended and restated by-laws("by-laws") and applicable provisions of Delaware corporate law. You should read our certificate of incorporation and by-laws, which are filed as exhibits to our Annual Report on Form 10-K, and incorporated herein by reference.

Our authorized capital stock consists of 200,000,000 shares of common stock and 5,000,000 shares of preferred stock. The following series of preferred stock are currently designated:

Common Stock

Annual Meeting. Annual meetings of our stockholders are held on the date designated in accordance with our by-laws. Written notice must be mailed to each stockholder entitled to vote not less than ten nor more than 60 days before the date of the meeting. The presence in person or by proxy of the holders of record of a majority of our issued and outstanding shares entitled to vote at such meeting constitutes a quorum for the transaction of business at meetings of the stockholders. Special meetings of the stockholders may be called for any purpose only by the board of directors, and business transacted at any special meetings of stockholders shall be limited to matters relating to the purpose or purposes stated in the notice of such meeting. Except as may be otherwise provided by applicable law, our certificate of incorporation or our by-laws, all elections shall be decided by a plurality, and all other questions shall be decided by a majority, of the votes cast by stockholders entitled to vote thereon at a duly held meeting of stockholders at which a quorum is present.

Voting Rights. Each holder of common stock is entitled to one vote for each share held on all matters to be voted upon by stockholders.

Dividends. The holders of common stock, after any preferences of holders of any preferred stock, are entitled to receive dividends when and if declared by the board of directors out of legally available funds.

Liquidation and Dissolution. If we are liquidated or dissolved, the holders of the common stock will be entitled to share in our assets available for distribution to stockholders in proportion to the amount of common stock they own. The amount available for common stockholders is calculated after payment of liabilities. Holders of any preferred stock may be entitled to receive a preferential share of our assets before the holders of the common stock receive any assets.

Other Rights. Holders of the common stock have no right to:

The common stock does not have cumulative voting rights. Holders of shares of the common stock are not required to make additional capital contributions.

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Transfer Agent and Registrar. Continental Stock Transfer & Trust Company is transfer agent and registrar for the common stock.

Preferred Stock

We are authorized to issue "blank check" preferred stock, which may be issued in one or more series upon authorization of our board of directors. Our board of directors is authorized to fix the designation of the series, the number of authorized shares of the series, dividend rights and terms, conversion rights, voting rights, redemption rights and terms, liquidation preferences and any other rights, powers, preferences and limitations applicable to each series of preferred stock. The authorized shares of our preferred stock are available for issuance without further action by our stockholders, unless such action is required by applicable law or the rules of any stock exchange on which our securities may be listed. If the approval of our stockholders is not required for the issuance of shares of our preferred stock, our board may determine not to seek stockholder approval.

A series of our preferred stock could, depending on the terms of such series, impede the completion of a merger, tender offer or other takeover attempt. Our board of directors will make any determination to issue preferred shares based upon its judgment as to the best interests of our stockholders. Our board of directors, in so acting, could issue preferred stock having terms that could discourage an acquisition attempt through which an acquirer may be able to change the composition of our board of directors, including a tender offer or other transaction that some, or a majority, of our stockholders might believe to be in their best interests or in which stockholders might receive a premium for their stock over the then-current market price of the stock.

Series X and Series X1 Preferred Stock

Each share of Series X Preferred Stock and Series X1 Preferred Stock (collectively, the "Convertible Preferred Stock") is convertible into 55.5556 shares of our common stock at the option of the holder at any time; subject to certain limitations, including, that the holder will be prohibited from converting the ConvertiblePreferred Stock into common stock if, as a result of such conversion, the holder, together with its affiliates, would beneficially own a number of shares of common stock above a conversion blocker, which is initially set at 9.99% or 9.9% of the total common stock then issued and outstanding immediately following the conversion of such shares of Series X Preferred Stock or Series X1Preferred Stock, respectively. In the event of the Company's liquidation, dissolution or winding up, holders of the ConvertiblePreferred Stock will participate pari passu with any distribution of proceeds to holders of common stock. Holders of the Convertible Preferred Stock are entitled to receive dividends on shares of the Convertible Preferred Stock, on an as-if-converted-to-common-stock basis (without regard to any beneficial ownership limitations), and in the same form as dividends actually paid on shares of the common stock. Shares of the ConvertiblePreferred Stock generally have no voting rights, except as required by law and except that the consent of a majority of the holders of either series of outstanding Convertible Preferred Stock will be required to amend the terms of such series.

As long as any shares of the Convertible Preferred Stock are outstanding, we will not, without the affirmative vote of the holders of a majority of the then outstanding shares of either series of the Convertible Preferred Stock, as applicable, (a) alter or change adversely the powers, preferences or rights given to either series of the Convertible Preferred Stock, (b) alter or amend the Certificate of Designation for either series of the Convertible Preferred Stock, (c) amend our certificate of incorporation or other charter documents in any manner that adversely affects any rights of the holders of either series of the Convertible Preferred Stock, (d) increase the number of authorized shares of either series of the Convertible Preferred Stock, or (e) enter into any agreement with respect to any of the foregoing. The Convertible Preferred Stock does not have a preference upon any liquidation, dissolution or winding-up of the Company.

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Provisions of Our Certificate of Incorporation and By-laws and Delaware Law That May Have Anti-Takeover Effects

Staggered Board; Removal of Directors

Our certificate of incorporation and by-laws divide our board of directors into three classes with staggered three-year terms. In addition, a director is only able to be removed for cause and only by the affirmative vote of the holders of at least 75% of the votes that all of our stockholders would be entitled to cast in an annual election of

our board of directors. Any vacancy in our board of directors, including a vacancy resulting from an enlargement of our board of directors, may only be filled by vote of a majority of our directors then in office. The classification of our board of directors and the limitations on the removal of directors and filling of vacancies could make it more difficult for a third party to acquire, or discourage a third party from seeking to acquire, control of our company.

Stockholder Action by Written Consent; Special Meetings

Our certificate of incorporation provides that any action required or permitted to be taken by our stockholders must be effected at a duly called annual or special meeting of such holders and may not be effected by any consent in writing by such holders. Our certificate of incorporation and by-laws also provide that, except as otherwise required by law, special meetings of our stockholders can only be called by our board of directors.

Advance Notice Requirements for Stockholder Proposals

Our by-laws establish an advance notice procedure for stockholder proposals to be brought before an annual meeting of stockholders, including proposed nominations of persons for election to our board of directors. Stockholders at an annual meeting may only consider proposals or nominations specified in the notice of meeting or brought before the meeting by or at the direction of our board of directors or by a stockholder of record on the record date for the meeting who is entitled to vote at the meeting and who has delivered timely written notice in proper form to our secretary of the stockholder's intention to bring such business before the meeting. These provisions could have the effect of delaying until the next stockholder meeting stockholder actions that are favored by the holders of a majority of our outstanding voting securities.

Delaware Business Combination Statute

We are subject to Section 203 of the Delaware General Corporation Law. Subject to certain exceptions, Section 203 prevents a publicly-held Delaware corporation from engaging in a "business combination" with any "interested stockholder" for three years following the date that the person became an interested stockholder, unless the interested stockholder attained such status with the approval of our board of directors or unless the business combination is approved in a prescribed manner. A "business combination" includes, among other things, a merger or consolidation involving us and the "interested stockholder" and the sale of more than 10% of our assets. In general, an "interested stockholder" is any entity or person beneficially owning 15% or more of our outstanding voting stock and any entity or person affiliated with or controlling or controlled by such entity or person.

Amendment of Certificate of Incorporation and By-laws

The Delaware General Corporation Law provides generally that the affirmative vote of a majority of the shares entitled to vote on any matter is required to amend a corporation's certificate of incorporation or by-laws, unless a corporation's certificate of incorporation or by-laws, as the case may be, requires a greater percentage. Our by-laws may be amended or repealed by a majority vote of our board of directors or by the affirmative vote of the holders of at least 75% of the votes that all of our stockholders would be entitled to cast in any annual election of directors. In addition, the affirmative vote of the holders of at least 75% of the votes that all of our stockholders would be entitled to cast in any annual election of directors is required to amend or repeal or to adopt any provisions inconsistent with any of the provisions of our certificate of incorporation described above under "-Staggered Board; Removal of Directors" and "-Stockholder Action by Written Consent; Special Meetings."

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DESCRIPTION OF DEBT SECURITIES

We may offer debt securities that may be senior or subordinated. We refer to the senior debt securities and the subordinated debt securities collectively as debt securities. The following description summarizes the general terms and provisions of the debt securities. We will describe the specific terms of the debt securities and the extent, if any, to which the general provisions summarized below apply to any series of debt securities in the prospectus supplement relating to the series and any applicable free writing prospectus that we authorize to be delivered.

We may issue senior debt securities from time to time, in one or more series under a senior indenture to be entered into between us and a senior trustee to be named in a prospectus supplement, which we refer to as the senior trustee. We may issue subordinated debt securities from time to time, in one or more series under a subordinated indenture to be entered into between us and a subordinated trustee to be named in a prospectus supplement, which we refer to as the subordinated trustee. The forms of senior indenture and subordinated indenture are filed as exhibits to the registration statement of which this prospectus forms a part. Together, the senior indenture and the subordinated indenture are referred to as the indentures and, together, the senior trustee and the subordinated trustee are referred to as the trustees. This prospectus briefly outlines some of the provisions of the indentures. The following summary of the material provisions of the indentures is qualified in its entirety by the provisions of the indentures, including definitions of certain terms used in the indentures. Wherever we refer to particular sections or defined terms of the indentures, those sections or defined terms are incorporated by reference in this prospectus or the applicable prospectus supplement. You should review the indentures that are filed as exhibits to the registration statement of which this prospectus forms a part for additional information.

None of the indentures will limit the amount of debt securities that we may issue. The applicable indenture will provide that debt securities may be issued up to an aggregate principal amount authorized from time to time by us and may be payable in any currency or currency unit designated by us or in amounts determined by reference to an index.

General

The senior debt securities will constitute our unsecured and unsubordinated general obligations and will rank pari passu with our other unsecured and unsubordinated obligations. The subordinated debt securities will constitute our unsecured and subordinated general obligations and will be junior in right of payment to our senior indebtedness (including senior debt securities), as described under the heading "-Certain Terms of the Subordinated Debt Securities-Subordination."

The debt securities will be our unsecured obligations. Any secured debt or other secured obligations will be effectively senior to the debt securities to the extent of the value of the assets securing such debt or other obligations.

The applicable prospectus supplement and/or free writing prospectus will include any additional or different terms of the debt securities of any series being offered, including the following terms:

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When we refer to "principal" in this section with reference to the debt securities, we are also referring to "premium, if any."

We may from time to time, without notice to or the consent of the holders of any series of debt securities, create and issue further debt securities of any such series ranking equally with the debt securities of such series in all respects (or in all respects other than (1) the payment of interest accruing prior to the issue date of such further debt securities or (2) the first payment of interest following the issue date of such further debt securities). Such further debt securities may be consolidated and form a single series with the debt securities of such series and have the same terms as to status, redemption or otherwise as the debt securities of such series.

You may present debt securities for exchange and you may present debt securities for transfer in the manner, at the places and subject to the restrictions set forth in the debt securities and the applicable prospectus supplement. We will provide you those services without charge, although you may have to pay any tax or other governmental charge payable in connection with any exchange or transfer, as set forth in the indenture.

Debt securities may bear interest at a fixed rate or a floating rate. Debt securities bearing no interest or interest at a rate that at the time of issuance is below the prevailing market rate (original issue discount securities) may be sold at a discount below their stated principal amount. U.S. federal income tax considerations applicable to any such discounted debt securities or to certain debt securities issued at par which are treated as having been issued at a discount for U.S. federal income tax purposes will be described in the applicable prospectus supplement.

We may issue debt securities with the principal amount payable on any principal payment date, or the amount of interest payable on any interest payment date, to be determined by reference to one or more currency exchange rates, securities or baskets of securities, commodity prices or indices. You may receive a payment of principal on any principal payment date, or a payment of interest on any interest payment date, that is greater than or less than the amount of principal or interest otherwise payable on such dates, depending on the value on such dates of the

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applicable currency, security or basket of securities, commodity or index. Information as to the methods for determining the amount of principal or interest payable on any date, the currencies, securities or baskets of securities, commodities or indices to which the amount payable on such date is linked and certain related tax considerations will be set forth in the applicable prospectus supplement.

Certain Terms of the Senior Debt Securities

Covenants. Unless we indicate otherwise in a prospectus supplement, the senior debt securities will not contain any financial or restrictive covenants, including covenants restricting us from incurring, issuing, assuming or guaranteeing any indebtedness secured by a lien on any of our property or capital stock, or restricting us from entering into sale and leaseback transactions.

Consolidation, Merger and Sale of Assets. Unless we indicate otherwise in a prospectus supplement, we may not consolidate with or merge into any other person, in a transaction in which we are not the surviving corporation, or convey, transfer or lease our properties and assets substantially as an entirety to any person, in either case, unless:

No Protection in the Event of a Change in Control. Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the senior debt securities will not contain any provisions that may afford holders of the senior debt securities protection in the event we have a change in control or in the event of a highly leveraged transaction (whether or not such transaction results in a change in control).

Events of Default. Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the following are events of default under the senior indenture for any series of senior debt securities:

The default by us under any other debt, including any other series of debt securities, is not a default under the senior indenture.

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If an event of default other than an event of default specified in the fourth bullet point above occurs with respect to a series of senior debt securities and is continuing under the senior indenture, then, and in each such case, either the trustee or the holders of not less than 25% in aggregate principal amount of such series then outstanding under the senior indenture (each such series voting as a separate class) by written notice to us and to the trustee, if such notice is given by the holders, may, and the trustee at the request of such holders shall, declare the principal amount of and accrued interest on such series of senior debt securities to be immediately due and payable, and upon this declaration, the same shall become immediately due and payable.

If an event of default specified in the fourth bullet point above occurs and is continuing, the entire principal amount of and accrued interest on each series of senior debt securities then outstanding shall become immediately due and payable.

Unless otherwise specified in the prospectus supplement relating to a series of senior debt securities originally issued at a discount, the amount due upon acceleration shall include only the original issue price of the senior debt securities, the amount of original issue discount accrued to the date of acceleration and accrued interest, if any.

Upon certain conditions, declarations of acceleration may be rescinded and annulled and past defaults may be waived by the holders of a majority in aggregate principal amount of all the senior debt securities of such series affected by the default, each series voting as a separate class. Furthermore, subject to various provisions in the senior indenture, the holders of a majority in aggregate principal amount of a series of senior debt securities, by notice to the trustee, may waive an existing default or event of default with respect to such senior debt securities and its consequences, except a default in the payment of principal of or interest on such senior debt securities or in respect of a covenant or provision of the senior indenture which cannot be modified or amended without the consent of the holders of each such senior debt security. Upon any such waiver, such default shall cease to exist, and any event of default with respect to such senior debt securities shall be deemed to have been cured, for every purpose of the senior indenture; but no such waiver shall extend to any subsequent or other default or event of default or impair any right consequent thereto.

The holders of a majority in aggregate principal amount of a series of senior debt securities may direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any trust or power conferred on the trustee with respect to such senior debt securities. However, the trustee may refuse to follow any direction that conflicts with law or the senior indenture, that may involve the trustee in personal liability or that the trustee determines in good faith may be unduly prejudicial to the rights of holders of such series of senior debt securities not joining in the giving of such direction and may take any other action it deems proper that is not inconsistent with any such direction received from holders of such series of senior debt securities. A holder may not pursue any remedy with respect to the senior indenture or any series of senior debt securities unless:

These limitations, however, do not apply to the right of any holder of a senior debt security to receive payment of the principal of and interest on such senior debt security in accordance with the terms of such debt security, or to

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bring suit for the enforcement of any such payment in accordance with the terms of such debt security, on or after the due date for the senior debt securities, which right shall not be impaired or affected without the consent of the holder.

The senior indenture requires certain of our officers to certify, on or before a fixed date in each year in which any senior debt security is outstanding, as to their knowledge of our compliance with all covenants, agreements and conditions under the senior indenture.

Satisfaction and Discharge. We can satisfy and discharge our obligations to holders of any series of debt securities if:

Under current U.S. federal income tax law, the deposit and our legal release from the debt securities would be treated as though we took back your debt securities and gave you your share of the cash and debt securities or bonds deposited in trust. In that event, you could recognize gain or loss on the debt securities you give back to us. Purchasers of the debt securities should consult their own advisers with respect to the tax consequences to them of such deposit and discharge, including the applicability and effect of tax laws other than the U.S. federal income tax law.

Defeasance. Unless the applicable prospectus supplement provides otherwise, the following discussion of legal defeasance and discharge and covenant defeasance will apply to any series of debt securities issued under the indentures.

Legal Defeasance. We can legally release ourselves from any payment or other obligations on the debt securities of any series (called "legal defeasance") if certain conditions are met, including the following:

If we accomplish legal defeasance, as described above, you would have to rely solely on the trust deposit for repayment of the debt securities. You could not look to us for repayment in the event of any shortfall.

Covenant Defeasance. Without any change of current U.S. federal tax law, we can make the same type of deposit described above and be released from some of the covenants in the debt securities (called "covenant defeasance").

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In that event, you would lose the protection of those covenants but would gain the protection of having money and securities set aside in trust to repay the debt securities. In order to achieve covenant defeasance, we must do the following (among other things):

If we accomplish covenant defeasance, you could still look to us for repayment of the debt securities if there were a shortfall in the trust deposit. In fact, if one of the events of default occurred (such as our bankruptcy) and the debt securities become immediately due and payable, there may be such a shortfall. Depending on the events causing the default, you may not be able to obtain payment of the shortfall.

Modification and Waiver. We and the trustee may amend or supplement the senior indenture or the senior debt securities without the consent of any holder:

Other amendments and modifications of the senior indenture or the senior debt securities issued may be made, and our compliance with any provision of the senior indenture with respect to any series of senior debt securities

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may be waived, with the consent of the holders of a majority of the aggregate principal amount of the outstanding senior debt securities of all series affected by the amendment or modification (voting together as a single class); provided, however, that each affected holder must consent to any modification, amendment or waiver that:

It shall not be necessary for the holders to approve the particular form of any proposed amendment, supplement or waiver, but it shall be sufficient if the holders' consent approves the substance thereof. After an amendment, supplement or waiver of the senior indenture in accordance with the provisions described in this section becomes effective, the trustee must give to the holders affected thereby certain notice briefly describing the amendment, supplement or waiver. Any failure by the trustee to give such notice, or any defect therein, shall not, however, in any way impair or affect the validity of any such amendment, supplemental indenture or waiver.

No Personal Liability of Incorporators, Stockholders, Officers, Directors. The senior indenture provides that no recourse shall be had under any obligation, covenant or agreement of ours in the senior indenture or any supplemental indenture, or in any of the senior debt securities or because of the creation of any indebtedness represented thereby, against any of our incorporators, stockholders, officers or directors, past, present or future, or of any predecessor or successor entity thereof under any law, statute or constitutional provision or by the enforcement of any assessment or by any legal or equitable proceeding or otherwise. Each holder, by accepting the senior debt securities, waives and releases all such liability.

Concerning the Trustee. The senior indenture provides that, except during the continuance of an event of default, the trustee will not be liable except for the performance of such duties as are specifically set forth in the senior indenture. If an event of default has occurred and is continuing, the trustee will exercise such rights and powers vested in it under the senior indenture and will use the same degree of care and skill in its exercise as a prudent person would exercise under the circumstances in the conduct of such person's own affairs.

The senior indenture and the provisions of the Trust Indenture Act incorporated by reference therein contain limitations on the rights of the trustee thereunder, should it become a creditor of ours, to obtain payment of claims in certain cases or to realize on certain property received by it in respect of any such claims, as security or otherwise. The trustee is permitted to engage in other transactions, provided that if it acquires any conflicting interest (as defined in the Trust Indenture Act), it must eliminate such conflict or resign.

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We may have normal banking relationships with the senior trustee in the ordinary course of business.

Unclaimed Funds. All funds deposited with the trustee or any paying agent for the payment of principal, premium, interest or additional amounts in respect of the senior debt securities that remain unclaimed for two years after the date upon which such principal, premium or interest became due and payable will be repaid to us. Thereafter, any right of any holder of senior debt securities to such funds shall be enforceable only against us, and the trustee and paying agents will have no liability therefor.

Governing Law. The senior indenture and the senior debt securities will be governed by, and construed in accordance with, the internal laws of the State of New York.

Certain Terms of the Subordinated Debt Securities

Other than the terms of the subordinated indenture and subordinated debt securities relating to subordination or otherwise as described in the prospectus supplement relating to a particular series of subordinated debt securities, the terms of the subordinated indenture and subordinated debt securities are identical in all material respects to the terms of the senior indenture and senior debt securities.

Additional or different subordination terms may be specified in the prospectus supplement applicable to a particular series.

Subordination. The indebtedness evidenced by the subordinated debt securities is subordinate to the prior payment in full of all of our senior indebtedness, as defined in the subordinated indenture. During the continuance beyond any applicable grace period of any default in the payment of principal, premium, interest or any other payment due on any of our senior indebtedness, we may not make any payment of principal of or interest on the subordinated debt securities (except for certain sinking fund payments). In addition, upon any payment or distribution of our assets upon any dissolution, winding-up, liquidation or reorganization, the payment of the principal of and interest on the subordinated debt securities will be subordinated to the extent provided in the subordinated indenture in right of payment to the prior payment in full of all our senior indebtedness. Because of this subordination, if we dissolve or otherwise liquidate, holders of our subordinated debt securities may receive less, ratably, than holders of our senior indebtedness. The subordination provisions do not prevent the occurrence of an event of default under the subordinated indenture.

The term "senior indebtedness" of a person means with respect to such person the principal of, premium, if any, interest on, and any other payment due pursuant to any of the following, whether outstanding on the date of the subordinated indenture or incurred by that person in the future:

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DESCRIPTION OF WARRANTS

We may issue warrants to purchase common stock, preferred stock or debt securities. We may offer warrants separately or together with one or more additional warrants, common stock, preferred stock or debt securities, or any combination of those securities in the form of units, as described in the applicable prospectus supplement. If we issue warrants as part of a unit, the accompanying prospectus supplement will specify whether those warrants may be separated from the other securities in the unit prior to the expiration date of the warrants. The applicable prospectus supplement will also describe the following terms of any warrants:

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DESCRIPTION OF UNITS

As specified in the applicable prospectus supplement, we may issue units consisting of one or more shares of common stock, shares of preferred stock, debt securities, warrants or any combination of such securities.

The applicable prospectus supplement will specify the following terms of any units in respect of which this prospectus is being delivered:

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PLAN OF DISTRIBUTION

We may sell the securities from time to time pursuant to underwritten public offerings, negotiated transactions, block trades or a combination of these methods. We may sell the securities to or through underwriters, brokers or dealers, through agents, directly to one or more purchasers, or a combination of these methods. We may distribute securities from time to time in one or more transactions:

We may also sell equity securities covered by this registration statement in an "at the market offering" as defined in Rule 415 under the Securities Act of 1933, as amended (the "Securities Act"). Such offering may be made into an existing trading market for such securities in transactions at other than a fixed price, either:

Such at the market offerings, if any, may be conducted by underwriters acting as principal or agent.

A prospectus supplement or supplements (and any related free writing prospectus that we may authorize to be provided to you) will describe the terms of the offering of the securities, including, to the extent applicable:

Only underwriters named in the prospectus supplement are underwriters of the securities offered by the prospectus supplement.

If underwriters are used in the sale, they will acquire the securities for their own account and may resell the securities from time to time in one or more transactions at a fixed public offering price or at varying prices determined at the time of sale. The obligations of the underwriters to purchase the securities will be subject to the conditions set forth in the applicable underwriting agreement. We may offer the securities to the public through underwriting syndicates represented by managing underwriters or by underwriters without a syndicate. Subject to certain conditions, the underwriters will be obligated to purchase all of the securities offered by the prospectus supplement. Any public offering price and any discounts or concessions allowed or re-allowed or paid to dealers may change from time to time. We may use underwriters with whom we have a material relationship. We will describe in the prospectus supplement, naming the underwriter, the nature of any such relationship.

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We may sell securities directly or through agents we designate from time to time. We will name any agent involved in the offering and sale of securities, and we will describe any commissions we will pay the agent in the prospectus supplement. Unless the prospectus supplement states otherwise, our agent will act on a best-efforts basis for the period of its appointment.

We may authorize agents or underwriters to solicit offers by certain types of institutional investors to purchase securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. We will describe the conditions to these contracts and the commissions we must pay for solicitation of these contracts in the prospectus supplement.

We may provide agents and underwriters with indemnification against civil liabilities related to offerings pursuant to this prospectus, including liabilities under the Securities Act, or contribution with respect to payments that the agents or underwriters may make with respect to these liabilities. Agents and underwriters may engage in transactions with, or perform services for, us in the ordinary course of business.

All securities we offer, other than our shares of common stock, will be new issues of securities with no established trading market. Any underwriters may make a market in these securities, but will not be obligated to do so and may discontinue any market making at any time without notice. We cannot guarantee the liquidity of the trading markets for any securities.

Any underwriter may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Overallotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum. Short covering transactions involve purchases of the securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a stabilizing or covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time. These transactions may be effected on any exchange or over-the-counter market or otherwise.

Any underwriters who are qualified market makers on The Nasdaq Capital Market may engage in passive market making transactions in the securities on The Nasdaq Capital Market in accordance with Rule 103 of Regulation M, during the business day prior to the pricing of the offering, before the commencement of offers or sales of the securities. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security; if all independent bids are lowered below the passive market maker's bid, however, the passive market maker's bid must then be lowered when certain purchase limits are exceeded. Passive market making may stabilize the market price of the securities at a level above that which might otherwise prevail in the open market and, if commenced, may be discontinued at any time.

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LEGAL MATTERS

The validity of the securities in respect of which this prospectus is being delivered will be passed upon for us by O'Melveny & Myers LLP, Newport Beach, California. Additional legal matters may be passed upon for us or any underwriters, dealers or agents, by counsel that we may name in the applicable prospectus supplement.

EXPERTS

KMJ Corbin & Company LLP, an independent registered public accounting firm, has audited our consolidated financial statements as of December 31, 2023 and 2022, and for each of the two years in the period ended December 31, 2023, included in Amendment No. 2 to the Annual Report on Form 10-K/A for the year ended December 31, 2023, as set forth in their report, which is incorporated by reference in this prospectus. Our consolidated financial statements are incorporated by reference in reliance on KMJ Corbin & Company LLP's report, given on their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC, and we have filed with the SEC a registration statement on Form S-3 under the Securities Act with respect to the securities offered by this prospectus. This prospectus, which forms part of the registration statement, does not contain all of the information included in the registration statement, including its exhibits and schedules. For further information about us and the securities described in this prospectus, you should refer to the registration statement, its exhibits and schedules and our reports, proxies, information statements and other information filed with the SEC.

Our filings are available to the public on the Internet, through a database maintained by the SEC at www.sec.gov. We also maintain a website at www.eledon.com. We have included our website address for the information of prospective investors and do not intend it to be an active link to our website. Information contained on our website does not constitute a part of this prospectus or any applicable prospectus supplement (or any document incorporated by reference herein or therein).

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to "incorporate by reference" into this prospectus the information we file with the SEC, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this prospectus, and information that we file later with the SEC that is incorporated herein will automatically update and supersede this information. We incorporate by reference the documents listed below, except for any document or portion thereof deemed to be "furnished" and not filed in accordance with SEC rules:

In addition, any future filings made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act subsequent to the date of the registration statement of which this prospectus forms a part and prior to its effectiveness and following its effectiveness until the end of any offerings under this prospectus, except for any document or portion thereof deemed to be "furnished" and not filed in accordance with SEC rules, shall be deemed to be incorporated by reference into this prospectus.

You should rely only on the information incorporated by reference or provided in this prospectus or any prospectus supplement. We have not authorized anyone else to provide you with different information. You should not assume that the information in this prospectus or any prospectus supplement is accurate as of any date other than the date on the front page of those documents.

We will provide to each person, including any beneficial owner, to whom a prospectus is delivered, a copy of any or all of the information that is incorporated by reference in the prospectus, including exhibits to these documents. You may request a copy of these filings, at no cost, by contacting us, either orally or in writing, at the following:

Eledon Pharmaceuticals, Inc.

19800 MacArthur Boulevard, Suite 250

Irvine, California

(949) 238-8090

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18,356,173 Shares of Common Stock

Pre-Funded Warrants to Purchase 4,931,507 Shares of Common Stock

PROSPECTUS SUPPLEMENT

Sole Bookrunning Manager

Leerink Partners

October 29, 2024