Supplemental Prospectus - Form 424B3

Filed Pursuant to Rule 424(b)(3)

Registration No. 333-282934

PROSPECTUS

Up to 4,874,550 Shares of Common Stock

This prospectus relates to the resale, from time to time, by the selling stockholder named in this prospectus, or the Selling Stockholder, or any of their pledgees, donees, assignees and successors-in-interest, or collectively, the permitted transferees, of shares of our common stock that were issued to a certain investor pursuant to the terms of the Stock Purchase Agreement, dated as of May 29, 2023, to which we, Betta Pharmaceuticals Co., Ltd. and the Selling Stockholder are parties. This prospectus also covers any additional securities that may become issuable by reason of share splits, share dividends or other similar transactions.

We will not receive any proceeds from the sale of shares of common stock by the Selling Stockholder pursuant to this prospectus. However, we will pay the expenses, other than underwriting discounts and commissions and certain expenses incurred by the Selling Stockholder in disposing of the shares of common stock, associated with the sale of the shares of common stock pursuant to this prospectus.

We are registering the resale of the shares of common stock to satisfy certain registration rights we have granted to the Selling Stockholder. Our registration of the shares of common stock covered by this prospectus does not mean that the Selling Stockholder will offer or sell any of the shares of common stock. The Selling Stockholder and any of its permitted transferees may offer and sell the shares of common stock covered by this prospectus in a number of different ways and at varying prices. Additional information on the Selling Stockholder, and the times and manner in which it may offer and sell the shares of common stock under this prospectus, is provided under "Selling Stockholder" and "Plan of Distribution" in this prospectus.

You should read this prospectus and any prospectus supplement or amendment carefully before you invest in our securities.

Our common stock is listed on The Nasdaq Global Select Market under the symbol "CCCC." On November 12, 2024, the closing price for our common stock, as reported on The Nasdaq Global Select Market, was $5.51 per share. Our principal executive office is located at 490 Arsenal Way, Suite 120, Watertown, Massachusetts 02472.

Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertainties referenced under the heading "Risk Factors" contained in this prospectus beginning on page 7 and any applicable prospectus supplement, and under similar headings in the other documents that are incorporated by reference into this prospectus. You should read the entire prospectus carefully before you make your investment decision.

Neither the U.S. 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.

The date of this Prospectus is November 13, 2024.

TABLE OF CONTENTS

Page
About This Prospectus	1
Cautionary Statement Regarding Forward-Looking Statements	2
The Company	4
The Offering	6
Risk Factors	7
Market and Industry Data and Forecasts	8
Use of Proceeds	8
Selling Stockholder	9
Plan of Distribution	11
Description of Capital Stock	15
Legal Matters	19
Experts	19
Where You Can Find More Information	19
Incorporation by Reference	20

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement on Form S-3 that we filed with the SEC using a "shelf" registration process. Under this shelf registration process, the Selling Stockholder and its permitted transferees may, from time to time, offer and sell the shares of common stock described in this prospectus in one or more offerings through any means described in the section entitled "Plan of Distribution." More specific terms of any shares of common stock that the Selling Stockholder and its permitted transferees offer and sell may be provided in a prospectus supplement that describes, among other things, the specific amounts and prices of the common stock being offered and the terms of the offering.

A prospectus supplement may also add, update or change information included in this prospectus. Any statement contained in this prospectus will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in such prospectus supplement modifies or supersedes such statement. Any statement so modified will be deemed to constitute a part of this prospectus only as so modified, and any statement so superseded will be deemed not to constitute a part of this prospectus.

You should rely only on the information contained in, or incorporated by reference into, this prospectus and any applicable prospectus supplement. Neither we nor the Selling Stockholder have authorized anyone to provide you with different or additional information. We and the Selling Stockholder 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 and only under circumstances and in jurisdictions where it is lawful to do so. You should assume that the information appearing in this prospectus or any prospectus supplement is accurate only as of the date on the front of those documents and any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus or any applicable prospectus supplement, or any sale of a security. 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 Selling Stockholder have done anything that would permit this offering or possession or distribution of this 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 must inform themselves about, and observe any restrictions relating to, the offering of our securities and the distribution of this prospectus outside the United States.

This prospectus contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of some of the documents referred to herein have been filed, will be filed or will be incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you may obtain copies of those documents as described below under the section titled "Where You Can Find More Information."

Unless the context otherwise requires, references to "C4T," the "company," "we," "us" and "our" refer to C4 Therapeutics, Inc., and its wholly owned, consolidated subsidiaries, or either or all of them as the context may require. We use various trademarks and trade names in our business, including without limitation our corporate name and logo. All other trademarks or trade names referred to in this prospectus are the property of their respective owners. This prospectus, any applicable prospectus supplement and the information incorporated herein or therein by reference may also contain trademarks and trade names of third parties, which are the property of their respective owners. Solely for convenience, the trademarks and trade names referred to or incorporated by reference in this prospectus, any applicable prospectus supplement or any free writing prospectus may be referred to without the ® and ™ symbols, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, any applicable prospectus supplement, any related free writing prospectus and the documents that we incorporate by reference herein or therein contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. Any statements about our expectations, beliefs, plans, objectives, assumptions or future events or performance are not historical facts and may be forward-looking. These statements are often, but are not always, made through the use of words or phrases such as "may," "will," "could," "should," "expects," "intends," "plans," "anticipates," "believes," "estimates," "predicts," "projects," "potential," "continue," and similar expressions, or the negative of these terms, or similar expressions. Accordingly, these statements involve estimates, assumptions, risks and uncertainties that could cause actual results to differ materially from those expressed in them. Any forward-looking statements are qualified in their entirety by reference to the factors discussed throughout this prospectus, and in particular those factors referenced in the section "Risk Factors."

This prospectus contains forward-looking statements that are based on our management's belief and assumptions and on information currently available to our management. These statements relate to future events or our future financial performance, and involve known and unknown risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to be materially different from any future results, levels of activity, performance or achievements expressed or implied by these forward-looking statements. Forward-looking statements include, but are not limited to, express or implied statements about:

•the initiation, timing, progress, results, safety and efficacy, and cost of our research and development programs and our current and future preclinical studies and clinical trials, including statements regarding the timing of initiation and completion of studies or trials, the period during which the results of the trials will become available, and our research and development programs;

•our ability to obtain funding for our operations necessary to complete further development, manufacturing and commercialization of our product candidates;

•our ability to obtain and maintain regulatory approval for any of our current or future product candidates;

•the period of time over which we anticipate our existing cash and cash equivalents, and marketable securities will be sufficient to fund our operating expenses and capital expenditure requirements;

•our ability to identify and develop product candidates for treatment of additional disease indications;

•the potential attributes and benefits of our product candidates;

•the rate and degree of market acceptance and clinical utility for any product candidates we may develop;

•the pricing and reimbursement of our product candidates, if approved, including the possibility for reduced pricing of our products, once approved, if they are later subject to mandatory price negotiation with the Centers for Medicare and Medicaid Services under the Inflation Reduction Act of 2022 or other applicable laws;

•the effects of competition with respect to any of our current or future product candidates, as well as innovations by current and future competitors in our industry;

•the implementation of our strategic plans for our business, any product candidates we may develop, and our TORPEDO® (Target ORiented ProtEin Degrader Optimizer) platform;

•the ability and willingness of our third-party strategic collaborators to continue research, development, and manufacturing activities relating to our product candidates, including our ability to advance programs under our existing collaboration agreements with F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc., or Roche, Betta Pharmaceuticals, Co., Ltd., or Betta Pharma, Merck Sharp & Dohme, LLC, or Merck, and Merck KGaA, Darmstadt, Germany, or MKDG, or other new collaboration agreements;

•the scope of protection we are able to establish and maintain for intellectual property rights covering our product candidates;

•estimates of our future expenses, revenues, capital requirements, and our needs for additional financing;

•future agreements with third parties in connection with the manufacturing and commercialization of our product candidates, if approved;

•the size and growth potential of the markets for our product candidates and our ability to serve those markets;

•our financial performance;

•regulatory developments in the United States and foreign countries;

•our ability to contract with third-party suppliers and manufacturers and their ability to perform adequately;

•the success of competing therapies that are or may become available;

•our ability to attract and retain key scientific or management personnel;

•developments relating to our competitors and our industry; and

•other risks and uncertainties, including those listed under the caption "Risk Factors" in our Annual Report on Form 10-K, for the year ended December 31, 2023 and in Part II, Item 1A - Risk Factors in our Form 10-Q for the quarters ended March 31, 2024, June 30, 2024, and September 30, 2024.

These forward-looking statements are neither promises nor guarantees of future performance due to a variety of risks and uncertainties, many of which are beyond our control, which could cause actual results to differ materially from those indicated by these forward-looking statements, including, without limitation the risk factors and cautionary statements described in other documents that we file from time to time with the SEC, specifically under "Item 1A: Risk Factors" and elsewhere in our most recent Annual Report on Form 10-K for the year ended December 31, 2023 and any other Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, and Current Reports on Form 8-K that are incorporated herein by reference, and the section of any accompanying prospectus supplement entitled "Risk Factors."

You should read this prospectus and the documents that we incorporate by reference in this prospectus completely and with the understanding that our actual future results may be materially different from what we expect. The forward-looking statements in this prospectus and the documents incorporated by reference represent our views as of their respective dates. We anticipate that subsequent events and developments will cause our views to change.

However, while we may elect to update these forward-looking statements at some point in the future, we assume no obligation to update or revise any forward-looking statements except to the extent required by applicable law. You should, therefore, not rely on these forward-looking statements as representing our views as of any date subsequent to the dates on which they were made.

This prospectus and the documents incorporated by reference also contain estimates, projections and other information concerning our industry, our business, and the markets for certain diseases, including data regarding the estimated size of those markets, and the incidence and prevalence of certain medical conditions. Information that is based on estimates, forecasts, projections, market research or similar methodologies is inherently subject to uncertainties and actual events or circumstances may differ materially from events and circumstances reflected in this information. Unless otherwise expressly stated, we obtained this industry, business, market and other data from reports, research surveys, studies and similar data prepared by market research firms and other third parties, industry, medical and general publications, government data and similar sources.

THE COMPANY

We are a clinical-stage biopharmaceutical company dedicated to delivering on the promise of targeted protein degradation, or TPD, science to create a new generation of small-molecule medicines that transforms patients' lives. By leveraging our proprietary TORPEDO platform, we have the capability to efficiently design and optimize small molecule protein degraders that are highly active against their desired targets by harnessing the body's natural process for destroying unwanted proteins. We believe our novel oral product candidates have the potential to overcome drug resistance often seen with inhibitors, target currently "undruggable" targets and improve patient outcomes. To date, we have successfully designed and advanced several protein degraders into the clinic across a range of target classes and, based on data from our clinical trials, our product candidates have demonstrated robust target degradation.

One of our most advanced product candidates, cemsidomide (CFT7455), is an orally bioavailable MonoDAC degrader of protein targets called IKZF1 and IKZF3, currently in clinical development for multiple myeloma, or MM, and non-Hodgkin lymphomas, or NHLs. The United States Food and Drug Administration, or FDA, has granted orphan drug designation to cemsidomide (CFT7455) for the treatment of MM. In December 2023, we presented positive clinical data from the dose escalation portion of the cemsidomide (CFT7455) Phase 1/2 trial as a monotherapy and in combination with dexamethasone in MM. We continue to progress the ongoing Phase 1/2 clinical trial of cemsidomide in MM and NHL.

Our other most advanced product candidate, CFT1946, is an orally bioavailable BiDAC degrader designed to be potent and selective against BRAF V600X mutant targets to treat melanoma, non-small cell lung cancer, or NSCLC, colorectal cancer, or CRC, and other malignancies that harbor this mutation. In January 2023, we initiated a first-in-human Phase 1/2 clinical trial of CFT1946 for the treatment of BRAF V600X mutant solid tumors including NSCLC, colorectal cancer and melanoma. In September 2024, we presented initial monotherapy CFT1946 data demonstrating proof of mechanism and early evidence of proof of concept in BRAF V600 mutant solid tumors at the European Society for Medical Oncology (ESMO) Congress 2024. We continue to progress the ongoing Phase 1/2 clinical trial of CFT1946.

Additionally, we are developing CFT8919, an orally bioavailable, allosteric, mutant-selective BiDAC degrader of epidermal growth factor receptor, or EGFR, with an L858R mutation in NSCLC. In May 2023, we entered into an exclusive licensing agreement for the manufacturing, development and commercialization of CFT8919 in Greater China, including Hong Kong SAR, Macau SAR and Taiwan, with Betta Pharmaceuticals, Co., Ltd, or Betta Pharma. Additionally, the FDA cleared the investigational new drug, or IND, application for CFT8919 and Betta Pharma received clinical trial application clearance for CFT8919 from China's National Medical Product Administration. We expect to initiate clinical trial activities outside Greater China following the completion of Betta Pharma's Phase 1 dose escalation trial in Greater China.

Beyond these initial product candidates, we are further diversifying our pipeline by developing new degraders against both clinically validated and currently undruggable targets for our own proprietary programs, as well as for programs we are developing in collaboration with MKDG, Merck, and Roche.

Corporate History

We were incorporated under the laws of Delaware in October 2015. Our principal executive offices are located at 490 Arsenal Way, Suite 120, Watertown, MA 02472 and our telephone number is (617) 231-0700. Our website address is www.c4therapeutics.com. We do not incorporate the information on or accessible through our website into this prospectus, and you should not consider any information on, or that can be accessed through, our website to be part of this prospectus. We have included our website address in this prospectus solely as an inactive textual reference.

We own or have rights to various trademarks, service marks and trade names that are used in connection with the operation of our business, including our company name, C4 Therapeutics, our logo, the name of our TORPEDO technology platform and the names of our BIDAC and MONODAC protein degrader product candidates. This prospectus may also contain trademarks, service marks and trade names of third parties, which are the property of their respective owners. Our use or display of third parties' trademarks, service marks, trade names or products in this prospectus is not intended to and does not imply a relationship with, or endorsement or sponsorship by us. Solely for convenience, the trademarks, service marks and trade names referred to in this prospectus may appear

without the ®, TM or SM symbols, but the omission of such references is not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights or the right of the applicable owner of these trademarks, service marks and trade names.

THE OFFERING

We are registering the resale by the selling stockholder or their permitted transferees of up to 4,874,550 shares of our common stock.

Resale of common stock

Common stock that may be sold by the Selling Stockholder named herein:	Up to an aggregate of 4,874,550 shares of our common stock.
Common Stock Outstanding:	70,562,901 shares as of September 30, 2024.
Use of Proceeds:	All of the shares of common stock offered by the selling stockholder pursuant to this prospectus will be sold by the Selling Stockholder for their respective accounts. We will not receive any of the proceeds from these sales.
Risk Factors:	Any investment in the common stock offered hereby is speculative and involves a high degree of risk. You should carefully consider the information set forth under "Risk Factors" elsewhere in this prospectus.
Offering Price:	The selling stockholder will offer the shares of common stock offered by this prospectus at the prevailing market prices or a privately negotiated price.
Nasdaq Global Select Market symbol:	"CCCC"

RISK FACTORS

An investment in our securities involves risks and uncertainties. You should carefully consider the risk factors incorporated by reference to our most recent Annual Report on Form 10-K, any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K, and all other information contained or incorporated by reference into this prospectus, as updated by our subsequent filings under the Exchange Act, and the risk factors and other information contained in any applicable prospectus supplement before making an investment decision. The risks described in these documents are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently deem immaterial also may impair our business operations. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow could be materially adversely affected. This could cause the trading price of our securities to decline, resulting in a loss of all or part of your investment. Please also carefully read the section titled "Cautionary Note Regarding Forward-Looking Statements."

MARKET AND INDUSTRY DATA AND FORECASTS

We obtained the industry, market and competitive position data used throughout this prospectus and the documents incorporated by reference into this prospectus from our own internal estimates and research, as well as from independent market research, industry and general publications and surveys, governmental agencies and publicly available information in addition to research, surveys and studies conducted by third parties. Internal estimates are derived from publicly available information released by industry analysts and third-party sources, our internal research and our industry experience, and are based on assumptions made by us based on such data and our knowledge of our industry and market, which we believe to be reasonable. In some cases, we do not expressly refer to the sources from which this data is derived. In addition, while we believe the industry, market and competitive position data included in or incorporated by reference into this prospectus is reliable and based on reasonable assumptions, such data involve risks and uncertainties and are subject to change based on various factors, including those referenced in the section entitled "Risk Factors" in this prospectus and under similar headings in the documents incorporated by reference into this prospectus. These and other factors could cause results to differ materially from those expressed in the estimates made by the independent parties or by us.

USE OF PROCEEDS

All of the shares of common stock offered by the Selling Stockholder pursuant to this prospectus will be sold by the Selling Stockholder for its respective accounts. We will not receive any of the proceeds from these sales.

The Selling Stockholder will pay any underwriting discounts and commissions and expenses incurred by the selling stockholder for brokerage, accounting, tax or legal services or any other expenses incurred by the selling stockholder in disposing of the shares of common stock covered by this prospectus. We will bear all other costs, fees and expenses incurred in effecting the registration of the shares covered by this prospectus, including, without limitation, all registration and filing fees, Nasdaq listing fees and fees and expenses of our counsel and our accountants.

SELLING STOCKHOLDER

This prospectus covers the resale or other disposition, from time to time, by the Selling Stockholder identified in the table below or its pledgees, donees, transferees or other successors in interest, of up to an aggregate of 4,874,550 shares of our common stock issued and sold to Betta Investment (Hong Kong) Limited ("Betta Investment") in connection with the Betta Stock Purchase Agreement (as defined below).

On May 29, 2023 and in connection with the execution of the License and Collaboration Agreement with Betta Pharma, we, Betta Pharma, and Betta Investment, an affiliate of Betta Pharma, entered into a Stock Purchase Agreement (the "Betta Stock Purchase Agreement"), pursuant to which Betta Investment agreed to purchase 5,567,928 shares of our common stock for an aggregate purchase price of approximately $25.0 million, or $4.49 per share. The closing of the investment occurred on January 4, 2024. Of such shares, Betta Investment currently holds 4,874,550 shares, which remain subject a lock-up under the Betta Stock Purchase Agreement until the first anniversary of the closing, which lock-up may be released by us in our sole discretion.

This prospectus covers the resale or other disposition by the Selling Stockholder or its transferees of up to 4,874,550 shares of our common stock issued to the Selling Stockholder pursuant to the Betta Stock Purchase Agreement. Throughout this prospectus, when we refer to the Selling Stockholder, we are referring to Betta Investment, the purchaser under the Betta Stock Purchase Agreement.

The Selling Stockholder may from time to time offer and sell any or all of the shares of common stock registered hereunder pursuant to this prospectus and any accompanying prospectus supplement. When we refer to the "Selling Stockholder" in this prospectus, we mean the person listed in the table below, its permitted transferees and others who later come to hold any of the Selling Stockholder's interest in the shares of common stock other than through a public sale.

Except as otherwise disclosed in this prospectus, the Selling Stockholder does not have, and within the past three years has not had, any position, office or other material relationship with us.

The following table has been prepared based on information provided to us by the Selling Stockholder. It sets forth the names and addresses of the Selling Stockholder, the aggregate number of shares of common stock that the Selling Stockholder may offer pursuant to this prospectus, and the beneficial ownership of the Selling Stockholder both before and after the offering. We have based percentage ownership prior to this offering on 70,562,901 shares of common stock outstanding as of September 30, 2024. We cannot advise you as to whether the Selling Stockholder will in fact sell any or all of such shares of common stock. In addition, the Selling Stockholder may sell, transfer or otherwise dispose of, at any time and from time to time, the shares of common stock in transactions exempt from the registration requirements of the Securities Act, after the date of this prospectus. For purposes of this table, we have assumed that the Selling Stockholder will have sold all of the shares of common stock covered by this prospectus upon the completion of the offering.

We have determined beneficial ownership in accordance with the rules of the SEC and the information is not necessarily indicative of beneficial ownership for any other purpose. Unless otherwise indicated below, to our knowledge, the persons and entities named in the tables have sole voting and sole investment power with respect to all securities shown as beneficially owned by them, subject to community property laws where applicable. Except as otherwise set forth below, the address of the beneficial owner is c/o C4 Therapeutics, Inc., 490 Arsenal Way, Suite 120, Watertown, Massachusetts 02472.

Selling Stockholder information for each additional Selling Stockholder, if any, will be set forth by prospectus supplement to the extent required prior to the time of any offer or sale of such Selling Stockholder's securities pursuant to this prospectus. Any prospectus supplement may add, update, substitute, or change the information contained in this prospectus, including the identity of each Selling Stockholder and the number of securities registered on its behalf. See "Plan of Distribution" for additional information.

		Shares of Common Stock Beneficially Owned Prior to Offering		Shares of Common Stock Offered		Shares of Common Stock Beneficially Owned after the Offered Shares are Sold
Selling Stockholder		Number		Percent			Number		Percent
Betta Investment (Hong Kong) Limited (1)		4,874,550		6.91 %		4,874,550		-		- %

(1) The address for Betta Investments is Unit 1002 10/F, Perfect Commercial Building, 20 Austin Ave, Tsim Sha Tsui, Kowloon, Hong Kong, China.

Registration Rights

Pursuant to the terms of the Betta Stock Purchase Agreement, we agreed to prepare and file a registration statement with the SEC for purposes of registering the resale of shares of common stock held by the Selling Stockholder.

Subject to certain exceptions, we agreed to use our reasonable best efforts to cause this registration statement to be declared effective by the SEC as soon as practicable and, subject to certain exceptions, use commercially reasonable efforts to keep the registration statement of which this prospectus forms a part effective under the Securities Act until all shares covered by this Registration Statement have been sold or may be sold without volume restrictions pursuant to Rule 144.

PLAN OF DISTRIBUTION

We are registering the resale by the Selling Stockholder or their permitted transferees of up to 4,874,550 shares of our common stock that were issued to the Selling Stockholder pursuant to the Betta Stock Purchase Agreement.

We will not receive any proceeds from the sale of shares of common stock by the Selling Stockholder pursuant to this prospectus. The Selling Stockholder will pay any underwriting discounts and commissions and expenses incurred by the Selling Stockholder in disposing of the shares of common stock. We will bear all other costs, fees and expenses incurred in effecting the registration of the shares of common stock covered by this prospectus, including, without limitation, all registration and filing fees, Nasdaq listing fees and fees and expenses of our counsel and our independent registered public accountants.

The shares of common stock being registered hereunder may be offered and sold from time to time by the Selling Stockholder. The term "Selling Stockholder" includes donees, pledgees, transferees or other successors-in-interest selling securities received after the date of this prospectus from a Selling Stockholder as a gift, pledge, partnership distribution or other transfer. The Selling Stockholder will act independently of us in making decisions with respect to the timing, manner and size of each sale. Such sales may be made on one or more exchanges or in the over-the-counter market or otherwise, at prices and under terms then prevailing or at prices related to the then current market price or in negotiated transactions. The Selling Stockholder reserves the right to accept and, together with its respective agents, to reject, any proposed purchase of securities to be made directly or through agents. The Selling Stockholder and any of their permitted transferees may sell their securities offered by this prospectus on any securities exchange, market or trading facility on which the securities are traded or in private transactions. If underwriters are used in the sale, such underwriters will acquire the shares for their own account. These sales may be at a fixed price or varying prices, which may be changed, or at market prices prevailing at the time of sale, at prices relating to prevailing market prices or at negotiated prices. The securities may be offered to the public through underwriting syndicates represented by managing underwriters or by underwriters without a syndicate. The obligations of the underwriters to purchase the securities will be subject to certain conditions. The underwriters will be obligated to purchase all the securities offered if any of the securities are purchased.

Subject to the limitations set forth in any applicable registration rights agreement, the Selling Stockholder may use any one or more of the following methods when selling the securities offered by this prospectus:

•purchases by a broker-dealer as principal and resale by such broker-dealer for its own account pursuant to this prospectus;

•ordinary brokerage transactions and transactions in which the broker solicits purchasers;

•block trades in which the broker-dealer so engaged will attempt to sell the securities as agent but may position and resell a portion of the block as principal to facilitate the transaction;

•an over-the-counter distribution in accordance with the rules of Nasdaq;

•through trading plans entered into by a Selling Stockholder pursuant to Rule 10b5-1 under the Exchange Act that are in place at the time of an offering pursuant to this prospectus and any applicable prospectus supplement hereto that provide for periodic sales of their securities on the basis of parameters described in such trading plans;

•through one or more underwritten offerings on a firm commitment or best efforts basis;

•settlement of short sales entered into after the date of this prospectus;

•agreements with broker-dealers to sell a specified number of the securities at a stipulated price per share;

•in "at the market offerings," as defined in Rule 415 under the Securities Act, at negotiated prices, at prices prevailing at the time of sale or at prices related to such prevailing market prices, including sales made directly on a national securities exchange or sales made through a market maker other than on an exchange or other similar offerings through sales agents;

•directly to purchasers, including through a specific bidding, auction or other process or in privately negotiated transactions;

•through the writing or settlement of options or other hedging transactions, whether through an options exchange or otherwise;

•through a combination of any of the above methods of sale; or

•any other method permitted pursuant to applicable law.

In addition, a Selling Stockholder that is an entity may elect to make a pro rata in-kind distribution of securities to its members, partners or stockholders pursuant to the registration statement of which this prospectus is a part by delivering a prospectus with a plan of distribution. Such members, partners or stockholders would thereby receive freely tradeable securities pursuant to the distribution through a registration statement. To the extent a distributee is an affiliate of ours (or to the extent otherwise required by law), we may file a prospectus supplement in order to permit the distributees to use the prospectus to resell the securities acquired in the distribution.

There can be no assurance that the Selling Stockholder will sell all or any of the shares of common stock offered by this prospectus. In addition, the Selling Stockholder may also sell shares of common stock under Rule 144 under the Securities Act, if available, or in other transactions exempt from registration, rather than under this prospectus. The Selling Stockholder have the sole and absolute discretion not to accept any purchase offer or make any sale of shares of common stock if they deem the purchase price to be unsatisfactory at any particular time.

The Selling Stockholder also may transfer the shares of common stock in other circumstances, in which case the transferees, pledgees or other successors-in-interest will be the selling beneficial owners for purposes of this prospectus. Upon being notified by a Selling Stockholder that a donee, pledgee, transferee, other successor-in-interest intends to sell our securities, we will, to the extent required, promptly file a supplement to this prospectus to name specifically such person as a selling stockholder.

With respect to a particular offering of the shares of common stock held by the Selling Stockholder, to the extent required, an accompanying prospectus supplement or, if appropriate, a post-effective amendment to the registration statement of which this prospectus is part, will be prepared and will set forth the following information:

•the specific securities to be offered and sold;

•the names of the selling stockholder;

•the respective purchase prices and public offering prices, the proceeds to be received from the sale, if any, and other material terms of the offering;

•settlement of short sales entered into after the date of this prospectus;

•the names of any participating agents, broker-dealers or underwriters; and

•any applicable commissions, discounts, concessions and other items constituting compensation from the selling stockholder.

In connection with distributions of the securities or otherwise, the Selling Stockholder may enter into hedging transactions with broker-dealers or other financial institutions. In connection with such transactions, broker-dealers or other financial institutions may engage in short sales of the securities in the course of hedging the positions they assume with Selling Stockholder. The Selling Stockholder may also sell the securities short and redeliver the securities to close out such short positions. The Selling Stockholder may also enter into option or other transactions with broker-dealers or other financial institutions which require the delivery to such broker-dealer or other financial institution of securities offered by this prospectus, which securities such broker-dealer or other financial institution may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction). The Selling Stockholder may also pledge securities to a broker-dealer or other financial institution, and, upon a default, such broker-dealer or other financial institution, may effect sales of the pledged securities pursuant to this prospectus (as supplemented or amended to reflect such transaction).

In order to facilitate the offering of the securities, any underwriters or agents, as the case may be, involved in the offering of such securities may engage in transactions that stabilize, maintain or otherwise affect the price of our securities. Specifically, the underwriters or agents, as the case may be, may over-allot in connection with the

offering, creating a short position in our securities for their own account. In addition, to cover overallotments or to stabilize the price of our securities, the underwriters or agents, as the case may be, may bid for, and purchase, such securities in the open market. Finally, in any offering of securities through a syndicate of underwriters, the underwriting syndicate may reclaim selling concessions allotted to an underwriter or a broker-dealer for distributing such securities in the offering if the syndicate repurchases previously distributed securities in transactions to cover syndicate short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of the securities above independent market levels. The underwriters or agents, as the case may be, are not required to engage in these activities, and may end any of these activities at any time.

The Selling Stockholder may solicit offers to purchase the securities directly from, and they may sell such securities directly to, institutional investors or others. In this case, no underwriters or agents would be involved. The terms of any of those sales, including the terms of any bidding or auction process, if utilized, will be described in the applicable prospectus supplement.

Our common stock is listed on The Nasdaq Global Select Market under the symbol "CCCC."

The Selling Stockholder may authorize underwriters, broker-dealers or agents to solicit offers by certain purchasers to purchase the securities 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. The contracts will be subject only to those conditions set forth in the prospectus supplement, and the prospectus supplement will set forth any commissions we or the Selling Stockholder pay for solicitation of these contracts.

A Selling Stockholder may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement indicates, in connection with those derivatives, the third parties may sell securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by any Selling Stockholder or borrowed from any Selling Stockholder or others to settle those sales or to close out any related open borrowings of stock, and may use securities received from any Selling Stockholder in settlement of those derivatives to close out any related open borrowings of stock. The third party in such sale transactions will be an underwriter and will be identified in the applicable prospectus supplement (or a post-effective amendment). In addition, the Selling Stockholder may otherwise loan or pledge securities to a financial institution or other third party that in turn may sell the securities short using this prospectus. Such financial institution or other third party may transfer its economic short position to investors in our securities or in connection with a concurrent offering of other securities.

In effecting sales, broker-dealers or agents engaged by the Selling Stockholder may arrange for other broker-dealers to participate. Broker-dealers or agents may receive commissions, discounts or concessions from the Selling Stockholder in amounts to be negotiated immediately prior to the sale.

In compliance with the guidelines of the Financial Industry Regulatory Authority, or FINRA, the aggregate maximum discount, commission, fees or other items constituting underwriting compensation to be received by any FINRA member or independent broker-dealer will not exceed 8% of the gross proceeds of any offering pursuant to this prospectus and any applicable prospectus supplement.

If at the time of any offering made under this prospectus a member of FINRA participating in the offering has a "conflict of interest" as defined in FINRA Rule 5121, or Rule 5121, that offering will be conducted in accordance with the relevant provisions of Rule 5121.

To our knowledge, there are currently no plans, arrangements or understandings between the Selling Stockholder and any broker-dealer or agent regarding the sale of the securities by the Selling Stockholder. Upon our notification by a Selling Stockholder that any material arrangement has been entered into with an underwriter or broker-dealer for the sale of securities through a block trade, special offering, exchange distribution, secondary distribution or a purchase by an underwriter or broker-dealer, we will file, if required by applicable law or regulation, a supplement to this prospectus pursuant to Rule 424(b) under the Securities Act disclosing certain material information relating to such underwriter or broker-dealer and such offering.

Underwriters, broker-dealers or agents may facilitate the marketing of an offering online directly or through one of their affiliates. In those cases, prospective investors may view offering terms and a prospectus online and, depending upon the particular underwriter, broker-dealer or agent, place orders online or through their financial advisors.

In offering the securities covered by this prospectus, the Selling Stockholder and any underwriters, broker-dealers or agents who execute sales for the Selling Stockholder may be deemed to be "underwriters" within the meaning of the Securities Act in connection with such sales. Any discounts, commissions, concessions or profit they earn on any resale of those securities may be underwriting discounts and commissions under the Securities Act.

The underwriters, broker-dealers and agents may engage in transactions with us or the Selling Stockholder, or perform services for us or the Selling Stockholder, in the ordinary course of business.

In order to comply with the securities laws of certain states, if applicable, the securities must be sold in such jurisdictions only through registered or licensed brokers or dealers. In addition, in certain states the securities may not be sold unless they have been registered or qualified for sale in the applicable state or an exemption from the registration or qualification requirement is available and is complied with.

The Selling Stockholder and any other persons participating in the sale or distribution of the securities will be subject to applicable provisions of the Securities Act and the Exchange Act, and the rules and regulations thereunder, including, without limitation, Regulation M. These provisions may restrict certain activities of, and limit the timing of purchases and sales of any of the securities by, the Selling Stockholder or any other person, which limitations may affect the marketability of the shares of the securities.

We will make copies of this prospectus available to the Selling Stockholder for the purpose of satisfying the prospectus delivery requirements of the Securities Act. The Selling Stockholder may indemnify any agent, broker-dealer or underwriter that participates in transactions involving the sale of the securities against certain liabilities, including liabilities arising under the Securities Act.

We have agreed to indemnify the Selling Stockholder against certain liabilities, including certain liabilities under the Securities Act, the Exchange Act or other federal or state law. Agents, broker-dealers and underwriters may be entitled to indemnification by us and the Selling Stockholder against certain civil liabilities, including liabilities under the Securities Act, or to contribution with respect to payments which the agents, broker-dealers or underwriters may be required to make in respect thereof.

DESCRIPTION OF CAPITAL STOCK

The following description of our common stock and preferred stock, together with the additional information we include in any applicable prospectus supplements, summarizes the material terms and provisions of the common stock and preferred stock that we may offer under this prospectus. The following description of our capital stock does not purport to be complete and is subject to, and qualified in its entirety by, our certificate of incorporation and bylaws, which are exhibits to the registration statement of which this prospectus forms a part, and by applicable law. The terms of our common stock and preferred stock may also be affected by Delaware law.

General

Our authorized capital stock consists of one hundred fifty million (150,000,000) shares of common stock, par value $0.0001 per share, and ten million (10,000,000) shares of undesignated preferred stock, par value $0.0001 per share.

Common Stock

The holders of our common stock are entitled to one vote for each share held on all matters submitted to a vote of the stockholders. The holders of our common stock do not have any cumulative voting rights. Holders of our common stock are entitled to receive ratably any dividends declared by our board of directors out of funds legally available for that purpose, subject to any preferential dividend rights of any outstanding preferred stock. Our common stock has no preemptive rights, conversion rights or other subscription rights or redemption or sinking fund provisions.

In the event of our liquidation, dissolution or winding up, holders of our common stock will be entitled to share ratably in all assets remaining after payment of all debts and other liabilities and any liquidation preference of any outstanding preferred stock.

Our Common Stock is listed on The Nasdaq Global Select Market under the trading symbol "CCCC."

The transfer agent and registrar for our Common Stock is Computershare Trust Company, N.A.

Preferred Stock

Our board of directors has the authority, without further action by our stockholders, to issue up to 10,000,000 shares of preferred stock in one or more series and to fix the rights, preferences, privileges and restrictions thereof. These rights, preferences and privileges could include dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting, or the designation of, such series, any or all of which may be greater than the rights of common stock. The issuance of our preferred stock could adversely affect the voting power of holders of common stock and the likelihood that such holders will receive dividend payments and payments upon our liquidation. In addition, the issuance of preferred stock could have the effect of delaying, deferring or preventing a change in control of our company or other corporate action. No shares of preferred stock are currently outstanding, and we have no present plan to issue any shares of preferred stock.

Options

As of September 30, 2024, options to purchase 11,555,851 shares of common stock at a weighted-average exercise price of $12.19 per share were outstanding under our 2015 Stock Option and Grant Plan and our 2020 Stock Option and Incentive Plan and options to purchase 644,760 shares of common stock at a weighted-average exercise price of $4.64 per share issued pursuant to the employment inducement award exemption provided by Nasdaq Listing Rule 5635(c)(4).

Anti-Takeover Effects of Delaware Law and Certain Provisions of our Certificate of Incorporation and Amended and Restated By-laws

Our certificate of incorporation and by-laws include a number of provisions that may have the effect of delaying, deferring or preventing another party from acquiring control of us and encouraging persons considering unsolicited tender offers or other unilateral takeover proposals to negotiate with our board of directors rather than pursue non-negotiated takeover attempts. These provisions include the items described below.

Classified Board

Our certificate of incorporation provides for the division of our board of directors into three classes serving staggered three-year terms, with one class being elected each year. Our certificate of incorporation also provides that directors may be removed only for cause and then only by the affirmative vote of the holders of two-thirds or more of the shares then entitled to vote at an election of directors. Furthermore, any vacancy on our board of directors, however occurring, including a vacancy resulting from an increase in the size of our board, may only be filled by the affirmative vote of a majority of our directors then in office even if less than a quorum. The classification of directors, together with the limitations on removal of directors and treatment of vacancies, has the effect of making it more difficult for stockholders to change the composition of our board of directors.

No Written Consent of Stockholders

Our certificate of incorporation provides that all stockholder actions are required to be taken by a vote of the stockholders at an annual or special meeting and that stockholders may not take any action by written consent in lieu of a meeting. This limit may lengthen the amount of time required to take stockholder actions and would prevent the amendment of our by-laws or removal of directors by our stockholders without holding a meeting of stockholders.

Meetings of Stockholders

Our certificate of incorporation and by-laws provide that only a majority of the members of our board of directors then in office may call special meetings of stockholders and only those matters set forth in the notice of the special meeting may be considered or acted upon at a special meeting of stockholders. Our by-laws limit the business that may be conducted at an annual meeting of stockholders to those matters properly brought before the meeting.

Advance Notice Requirements

Our by-laws establish advance notice procedures with regard to stockholder proposals relating to the nomination of candidates for election as directors or new business to be brought before meetings of our stockholders. These procedures provide that notice of stockholder proposals must be timely given in writing to our corporate secretary prior to the meeting at which the action is to be taken. Generally, to be timely, notice must be received at our principal executive offices not less than 90 days nor more than 120 days prior to the first anniversary date of the annual meeting for the preceding year. Our by-laws specify the requirements as to form and content of all stockholders' notices. These requirements may preclude stockholders from bringing matters before the stockholders at an annual or special meeting.

Amendment to Certificate of Incorporation and By-laws

Any amendment of our certificate of incorporation must first be approved by a majority of our board of directors and, if required by law or our certificate of incorporation, must thereafter be approved by a majority of the outstanding shares entitled to vote on the amendment and a majority of the outstanding shares of each class entitled to vote thereon as a class, except that the amendment of the provisions relating to stockholder action, board composition, limitation of liability and the amendment of our by-laws and certificate of incorporation must be approved by not less than two-thirds of the outstanding shares entitled to vote on the amendment and not less than two-thirds of the outstanding shares of each class entitled to vote thereon as a class. Our by-laws may be amended by the affirmative vote of a majority of the directors then in office, subject to any limitations set forth in the by-laws; and may also be amended by the affirmative vote of at least two-thirds of the outstanding shares entitled to vote on the amendment or, if our board of directors recommends that the stockholders approve the amendment, by the affirmative vote of the majority of the outstanding shares entitled to vote on the amendment, in each case voting together as a single class.

Undesignated Preferred Stock

Our certificate of incorporation provides for 10,000,000 authorized shares of preferred stock. The existence of authorized but unissued shares of preferred stock may enable our board of directors to discourage an attempt to obtain control of us by means of a merger, tender offer, proxy contest or otherwise. For example, if in the due exercise of its fiduciary obligations, our board of directors were to determine that a takeover proposal is not in the best interests of our stockholders, our board of directors could cause shares of preferred stock to be issued without stockholder approval in one or more private offerings or other transactions that might dilute the voting or other

rights of the proposed acquirer or insurgent stockholder or stockholder group. In this regard, our certificate of incorporation grants our board of directors broad power to establish the rights and preferences of authorized and unissued shares of preferred stock. The issuance of shares of preferred stock could decrease the amount of earnings and assets available for distribution to holders of shares of common stock. The issuance may also adversely affect the rights and powers, including voting rights, of these holders and may have the effect of delaying, deterring or preventing a change in control of us.

Delaware Anti-Takeover Statute

We are subject to the provisions of Section 203 of the Delaware General Corporation Law. In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a "business combination" with an "interested stockholder" for a three-year period following the time that this stockholder becomes an interested stockholder, unless the business combination is approved in a prescribed manner. Under Section 203, a business combination between a corporation and an interested stockholder is prohibited unless it satisfies one of the following conditions:

•before the stockholder became interested, our board of directors approved either the business combination or the transaction that resulted in the stockholder becoming an interested stockholder;

•upon consummation of the transaction that resulted in the stockholder becoming an interested stockholder, the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the voting stock outstanding, shares owned by persons who are directors and also officers, and employee stock plans, in some instances, but not the outstanding voting stock owned by the interested stockholder; or

•at or after the time the stockholder became interested, the business combination was approved by our board of directors and authorized at an annual or special meeting of the stockholders by the affirmative vote of at least two-thirds of the outstanding voting stock that is not owned by the interested stockholder.

Section 203 defines a business combination to include:

•any merger or consolidation involving the corporation and the interested stockholder;

•any sale, transfer, lease, pledge, exchange, mortgage or other disposition involving the interested stockholder of 10% or more of the assets of the corporation;

•subject to exceptions, any transaction that results in the issuance or transfer by the corporation of any stock of the corporation to the interested stockholder;

•subject to exceptions, any transaction involving the corporation that has the effect of increasing the proportionate share of the stock of any class or series of the corporation beneficially owned by the interested stockholder; and

•the receipt by the interested stockholder of the benefit of any loans, advances, guarantees, pledges or other financial benefits provided by or through the corporation.

In general, Section 203 defines an interested stockholder as any entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation and any entity or person affiliated with or controlling or controlled by the entity or person.

Choice of Forum

Our by-laws provide that, unless we consent in writing to the selection of an alternative form, the Court of Chancery of the State of Delaware will be the sole and exclusive forum for state law claims for (i) any derivative action or proceeding brought on our behalf; (ii) any action asserting a claim of breach of a fiduciary duty or other wrongdoing by any of our directors, officers, employees or agents to us or our stockholders; (iii) any action asserting a claim arising out of or pursuant to any provision of the General Corporation Law of the State of Delaware or our certificate of incorporation or by-laws; and (iv) any action asserting a claim governed by the internal affairs doctrine; provided, however, that this choice of forum provision does not apply to any causes of action arising under the Securities Act of 1933, as amended (the "Securities Act") or the Exchange Act of 1934, as amended. Our by-laws further provide that, unless we consent in writing to an alternative forum, the United States District Court for the District of Massachusetts will be the exclusive forum for resolving any complaint asserting a cause of action arising under the

Securities Act. Our by-laws also provide that any person or entity purchasing or otherwise acquiring any interest in shares of our capital stock will be deemed to have notice of and to have consented to this choice of forum provision. We recognize that the forum selection clause in our by-laws may impose additional litigation costs on stockholders in pursuing any such claims, particularly if the stockholders do not reside in or near the State of Delaware or the Commonwealth of Massachusetts, as applicable. Additionally, the forum selection clause in our by-laws may limit our stockholders' ability to bring a claim in a forum that they find favorable for disputes with us or our directors, officers or employees, which may discourage such lawsuits against us and our directors, officers and employees even though an action, if successful, might benefit our stockholders. The Court of Chancery of the State of Delaware or the United States District Court for the District of Massachusetts may also reach different judgments or results than would other courts, including courts where a stockholder considering an action may be located or would otherwise choose to bring the action, and such judgments may be more or less favorable to us than our stockholders.

LEGAL MATTERS

The validity of the shares of our common stock covered by this prospectus will be passed upon for us by Goodwin Procter LLP.

EXPERTS

The consolidated financial statements of C4 Therapeutics, Inc. and subsidiary as of December 31, 2023 and 2022, and for each of the years in the two-year period ended December 31, 2023, have been incorporated by reference herein and in the registration statement in reliance upon the report of KPMG LLP, independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

This prospectus is part of a registration statement on Form S-3 we filed with the SEC under the Securities Act and does not contain all the information set forth or incorporated by reference in the registration statement. Whenever a reference is made in this prospectus to any of our contracts, agreements or other documents, the reference may not be complete and you should refer to the exhibits that are a part of the registration statement or the exhibits to the reports or other documents incorporated by reference into this prospectus for a copy of such contract, agreement or other document. You may obtain copies of the registration statement and its exhibits via the SEC's EDGAR database.

We file annual, quarterly and current reports, proxy statements and other information with the SEC under the Exchange Act. The SEC maintains a website that contains reports, proxy and information statements and other information regarding issuers, including us, that file electronically with the SEC. You may obtain documents that we file with the SEC at www.sec.gov.

Our website address is www.c4therapeutics.com. We do not incorporate the information on or accessible through our website into this prospectus, and you should not consider any information on, or that can be accessed through, our website as part of this prospectus. Our website address is included in this prospectus as an inactive textual reference only.

INCORPORATION BY REFERENCE

The SEC allows us to incorporate by reference the information and reports we file with it, which means that we can disclose important information to you by referring you to these documents. The information incorporated by reference is considered to be a part of this prospectus, and the information that we file later with the SEC will automatically update and, where applicable, supersede the information already incorporated by reference. We are incorporating by reference the documents listed below, which have already been filed with the SEC (SEC File No. 001-39567), and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, including all filings made after the date of the filing of this registration statement, except as to any portions of any future report or document that is not deemed filed under such provisions until we sell all of the securities:

•our Annual Report on Form 10-K for the year ended December 31, 2023, filed with the SEC on February 22, 2024;

•the information specifically incorporated by reference into our Annual Report on Form 10-K for the year ended December 31, 2023 from our definitive proxy statement on Schedule 14A (other than the information furnished rather than filed), which was filed with the SEC on April 29, 2024; and

•our Quarterly Reports on Form 10-Q filed with the SEC for the quarters ended March 31, 2024, June 30, 2024 and September 30, 2024, filed with the SEC on May 8, 2024, August 1, 2024, and October 31, 2024, respectively;

•our Current Reports on Form 8-K filed with the SEC on January 9, 2024, March 4, 2024, March 8, 2024, June 10, 2024, June 21, 2024, September 3, 2024, October 11, 2024, October 15, 2024, and October 16, 2024; and

•the description of our common stock contained in our Registration Statement on Form 8-A (File No. 001-39567) as filed with the SEC on September 28, 2020, including any amendments or reports filed for the purpose of updating this description, including Exhibit 4.4 to our Annual Report on Form 10-K for the year ended December 31, 2020, as filed with the SEC on March 11, 2021.

Upon request and without charge, we will provide to each person, including any beneficial owner, to whom a copy of this prospectus is delivered, a copy of the documents incorporated by reference into this prospectus but not delivered with the prospectus. You may request a copy of these filings, and any exhibits we have specifically incorporated by reference as an exhibit in this prospectus, at no cost by writing or telephoning us at the following address: C4 Therapeutics, Inc., 490 Arsenal Way, Suite 120, Watertown, Massachusetts 02472, telephone: (617) 231-0700.

You may also access these documents, free of charge on the SEC's website at www.sec.gov or on our website at www.c4therapeutics.com. Information contained on our website is not incorporated by reference into this prospectus, and you should not consider any information on, or that can be accessed from, our website as part of this prospectus or any accompanying prospectus supplement.

Notwithstanding the foregoing, unless specifically stated to the contrary, information that we furnish (and that is not deemed "filed" with the SEC) under Items 2.02 and 7.01 of any Current Report on Form 8-K, including the related exhibits under Item 9.01, is not incorporated by reference into this prospectus or the registration statement of which this prospectus is a part.

This prospectus is part of a registration statement we filed with the SEC. We have incorporated exhibits into this registration statement. You should read the exhibits carefully for provisions that may be important to you.

You should rely only on the information incorporated by reference or provided in this prospectus or any prospectus supplement. We have not authorized anyone to provide you with different information. We are not making an offer of these securities in any state where the offer is not permitted. You should not assume that the information in this prospectus or in the documents incorporated by reference is accurate as of any date other than the date on the front of this prospectus or those documents.

Up to 4,874,550 Shares of Common Stock

PROSPECTUS

November 13, 2024