Regulation FD Disclosure - Form 425

On September 30, 2024, Byline Bancorp, Inc., a Delaware corporation ("Byline"), issued a press release announcing the execution of an Agreement and Plan of Merger in connection with its proposed acquisition of First Security Bancorp, Inc., a Delaware corporation ("First Security Bancorp"), and First Security Bancorp's wholly owned bank subsidiary, First Security Trust and Savings Bank, an Illinois chartered bank. Byline has also provided supplemental information regarding the proposed transaction. A copy of the press release is attached to this report as Exhibit 99.1 and a copy of the supplemental materials is attached as Exhibit 99.2, both of which are incorporated herein by reference.

The information furnished pursuant to Item 7.01 of this Current Report on Form 8-K (including Exhibit 99.1 and Exhibit 99.2 hereto) is being furnished and shall not be deemed "filed" under the Securities Exchange Act of 1934, as amended (the " Exchange Act "), nor shall it be incorporated by reference into future filings by Byline under the Securities Act of 1933, as amended (the " Securities Act "), or under the Exchange Act, except as expressly set forth by specific reference in such a filing. The furnishing of information pursuant to this Item 7.01 will not be deemed an admission as to the materiality of any information in this Current Report on Form 8-K that is required to be disclosed solely by Regulation FD.