UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): April 20, 2025

ACELYRIN, INC.

(Exact name of registrant as specified in its charter)


Delaware	001-41696	85-2406735
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification No.)

4149 Liberty Canyon Road

Agoura Hills, California

91301

(Address of Principal Executive Offices)

(Zip Code)

Registrant’s telephone number, including area code: (805) 456-4393

N/A

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☒	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading
Symbol(s)

Name of each exchange

on which registered

Common Stock, par value $0.00001 per share

SLRN

Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.01

Entry Into a Material Definitive Agreement.

Merger Agreement

As previously disclosed, on February 6, 2025, ACELYRIN, INC., a Delaware corporation (“ACELYRIN”), entered into an agreement and Plan of Merger (the “Merger Agreement”) with Alumis Inc., a Delaware corporation (“Alumis”), and Arrow Merger Sub, Inc., a Delaware corporation and a direct wholly owned subsidiary of Alumis (“Merger Sub”). Pursuant to the Merger Agreement, Merger Sub will merge with and into ACELYRIN and ACELYRIN will continue as the surviving corporation and a direct wholly owned subsidiary of Alumis (the “Merger”).

On April 20, 2025, ACELYRIN, Alumis and Merger Sub entered into that certain Amendment to the Agreement and Plan of Merger (the “Amendment”), which amends the Merger Agreement (the Merger Agreement as amended by the Amendment, the “Amended Agreement”) to, among other things, reflect that the issued and outstanding shares of common stock of ACELYRIN, par value $0.00001 per share (the “Shares”), will be cancelled and converted into the right to receive 0.4814 shares of voting common stock of Alumis, par value $0.0001 per share (“Alumis Common Stock”), without interest (the number of shares of Alumis Common Stock in exchange for each Share, the “Exchange Ratio”) and, if applicable, cash in lieu of fractional shares, without interest, subject to any applicable withholding. At the effective time of the Merger, Alumis’s stockholders will own approximately 52%, and ACELYRIN’s stockholders will own approximately 48%, of the outstanding shares of common stock of the combined company on a fully diluted basis.

Other than as expressly modified by the Amendment, the Merger Agreement, which was filed as Exhibit 2.1 to the Current Report on Form 8-K filed by ACELYRIN with the Securities and Exchange Commission (the “SEC”) on February 6, 2025, remains in full force and effect. The foregoing description of the Amendment does not purport to be complete and is subject to, and qualified in its entirety by reference to, the full text of the Amendment, which is attached as Exhibit 2.1 hereto and incorporated herein by reference.

Approval & Recommendation

Based on the unanimous recommendation of a transaction committee of the board of directors of ACELYRIN (the “ACELYRIN Board”), consisting solely of independent and disinterested directors of ACELYRIN, to which the ACELYRIN Board had delegated exclusive authority to consider, negotiate and evaluate the Amended Agreement and the transactions contemplated thereby, the ACELYRIN Board (i) determined that the Amended Agreement and the transactions contemplated by the Amended Agreement, are advisable, fair to and in the best interest of ACELYRIN and its stockholders, (ii) approved the execution, delivery and performance by ACELYRIN of the Amendment and the consummation by ACELYRIN of the transactions contemplated by the Amended Agreement, including the Merger and (iii) declared advisable and resolved to recommend that ACELYRIN’s stockholders adopt the Amended Agreement.

Based on the unanimous recommendation of a special committee of the board of directors of Alumis (the “Alumis Board”), consisting solely of independent and disinterested directors of Alumis, to which the Alumis Board has delegated exclusive authority to consider, negotiate and evaluate the Amended Agreement to the transactions contemplated thereby, the Alumis Board (i) determined that the Amendment and the transactions contemplated by the Amended agreement, including the Merger and the issuance of Alumis Common Stock pursuant to the Amended Agreement (the “Alumis Share Issuance”) are advisable, fair to and in the best interests of Alumis and its stockholders, (ii) approved the Amendment and the transactions contemplated by the Amended Agreement, including the Merger and the Alumis Share Issuance, and (iii) resolved to submit and recommend the approval of the Alumis Share Issuance to Alumis’s stockholders.

Item 7.01

Regulation FD Disclosure.

Members of ACELYRIN management and of the transaction committee of the ACELYRIN Board may hold meetings with certain investors, analysts and proxy advisory firms in connection with the upcoming special meeting of ACELYRIN stockholders (the “Special Meeting”) to consider and vote upon a proposal to adopt the Amended Agreement. The Special Meeting is scheduled to be held on May 19, 2025. A copy of the presentation materials to be provided during the meetings is furnished as Exhibit 99.1 to this Current Report on Form 8-K.

On April 21, 2025, ACELYRIN and Alumis issued a joint press release announcing the entrance into the Amended Agreement described in Item 1.01 of this Current Report on Form 8-K, a copy of which is furnished as Exhibit 99.2 hereto.

The information contained in this Item 7.01, including Exhibit 99.1 and Exhibit 99.2, is being furnished to the SEC and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or incorporated by reference in any filing under the Securities Act of 1933, as amended (the “Securities Act”), except as shall be expressly set forth by specific reference in such filing.

Item 9.01

Financial Statements and Exhibits.

(d) Exhibits.


Exhibit Number		Description

2.1		Amendment to the Agreement and Plan of Merger, dated as of April 20, 2025.

99.1		Investor Presentation, dated as of April 21, 2025.

99.2		Joint Press Release, dated as of April 21, 2025.

104		Cover Page Interactive Data File (embedded within the Inline XBRL document).

Forward-Looking Statements

This communication contains forward-looking statements within the meaning of federal securities laws, including the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995. Such statements are based upon current plans, estimates and expectations of management of Alumis Inc. (“Alumis”) and ACELYRIN, Inc. (“ACELYRIN”) in light of historical results and trends, current conditions and potential future developments, and are subject to various risks and uncertainties that could cause actual results to differ materially from such statements. The inclusion of forward-looking statements should not be regarded as a representation that such plans, estimates and expectations will be achieved. Words such as “anticipate,” “expect,” “project,” “intend,” “believe,” “may,” “will,” “should,” “plan,” “could,” “continue,” “target,” “contemplate,” “estimate,” “forecast,” “guidance,” “predict,” “possible,” “potential,” “pursue,” “likely,” and words and terms of similar substance used in connection with any discussion of future plans, actions or events identify forward-looking statements. All statements, other than statements of historical facts, including express or implied statements regarding the proposed transaction; the conversion of equity interests contemplated by the agreement and plan of merger, dated as of February 6, 2025, as amended on April 20, 2025, by and among the parties (as amended, the “merger agreement”); the issuance of common stock of Alumis contemplated by the merger agreement; the expected filing by Alumis with the Securities and Exchanges Commission (the “SEC”) of a registration statement on Form S-4 (the “registration statement”) and a joint proxy statement/prospectus of Alumis and ACELYRIN to be included therein (the “joint proxy statement/prospectus”); the expected timing of the closing of the proposed transaction; the ability of the parties to complete the proposed transaction considering the various closing conditions; the expected benefits of the proposed transaction; the sufficiency of the combined company’s capital resources; the combined company’s cash runway, which is preliminary, unaudited and subject to change; the competitive ability and position of the combined company; the clinical pipeline of the combined company; and any assumptions underlying any of the foregoing, are forward-looking statements.

Risks and uncertainties include, among other things, (i) the risk that the proposed transaction may not be completed in a timely basis or at all, which may adversely affect Alumis’ and ACELYRIN’s businesses and the price of their respective securities; (ii) the potential failure to receive, on a timely basis or otherwise, the required approvals of the proposed transaction, including stockholder approvals by both Alumis’ stockholders and ACELYRIN’S stockholders, and the potential failure to satisfy the other conditions to the consummation of the transaction; (iii) the effect of the announcement, pendency or completion of the proposed transaction on each of Alumis’ or ACELYRIN’s ability to attract, motivate, retain and hire key personnel and maintain relationships with partners, suppliers and others with whom Alumis or ACELYRIN does business, or on Alumis’ or ACELYRIN’s operating results and business generally; (iv) that the proposed transaction may divert management’s attention from each of Alumis’ and ACELYRIN’s ongoing business operations; (v) the risk of any legal proceedings related to the proposed transaction or otherwise, or the impact of the proposed transaction thereupon, including resulting expense or delay; (vi) that Alumis or ACELYRIN may be adversely affected by other economic, business and/or competitive factors; (vii) the occurrence of any event, change or other circumstance that could give rise to the termination of the merger agreement , including in circumstances which would require Alumis or ACELYRIN to pay a termination fee; (viii) the risk that restrictions during the pendency of the proposed transaction may impact Alumis’ or ACELYRIN’s ability to pursue certain business opportunities or strategic transactions; (ix) the risk that the anticipated benefits and synergies of the proposed transaction may not be fully realized or may take longer to realize than expected; (x) the impact of legislative, regulatory, economic, competitive and technological changes; (xi) risks relating to the value of Alumis securities to be issued in the proposed transaction; (xii) the risk that integration of the proposed transaction post-closing may not occur as anticipated or the combined company may not be able to achieve the growth prospects expected from the transaction; (xiii) the effect of the announcement, pendency or completion of the proposed transaction on the market price of the common stock of each of Alumis and ACELYRIN; (xiv) the implementation of each of Alumis’ and ACELYRIN’s business model and strategic plans for product candidates and pipeline, and challenges inherent in developing, commercializing, manufacturing, launching, marketing and selling potential existing and new products and product candidates; (xv) the scope, progress, results and costs of developing Alumis’ and ACELYRIN’s product candidates and any future product candidates, including conducting preclinical studies and clinical trials, and otherwise related to the research and development of Alumis’ and ACELYRIN’s pipeline; (xvi) the timing and costs involved in obtaining and maintaining regulatory approval for Alumis’ and ACELYRIN’s current or future product candidates, and any related restrictions, limitations and/or warnings in the label of any approved product; (xvii) the market for, adoption (including rate and degree of market acceptance) and pricing and reimbursement of Alumis’ and ACELYRIN’s product candidates, if approved, and their respective abilities to compete with therapies and procedures that are rapidly growing and evolving; (xviii) uncertainties in

contractual relationships, including collaborations, partnerships, licensing or other arrangements and the performance of third-party suppliers and manufacturers; (xix) the ability of each of Alumis and ACELYRIN to establish and maintain intellectual property protection for products or avoid or defend claims of infringement; (xx) Alumis’ ability to successfully integrate ACELYRIN’s operations and personnel; and (xxi) potential delays in initiating, enrolling or completing preclinical studies and clinical trials.

These risks, as well as other risks related to the proposed transaction, will be described in the registration statement and the joint proxy statement/prospectus that will be filed with the SEC in connection with the proposed transaction. While the list of factors presented here and the list of factors to be presented in the registration statement are considered representative, no such list should be considered to be a complete statement of all potential risks and uncertainties. For additional information about other factors that could cause actual results to differ materially from those described in the forward-looking statements, please refer to Alumis’ and ACELYRIN’s respective periodic reports and other filings with the SEC, including the risk factors identified in Alumis’ and ACELYRIN’s most recent Annual Reports on Form 10-K. The risks and uncertainties described above and in the SEC filings cited above are not exclusive and further information concerning Alumis and ACELYRIN and their respective businesses, including factors that potentially could materially affect their respective businesses, financial conditions or operating results, may emerge from time to time. Readers are urged to consider these factors carefully in evaluating these forward-looking statements, and not to place undue reliance on any forward-looking statements, which speak only as of the date hereof. Readers should also carefully review the risk factors described in other documents Alumis and ACELYRIN file from time to time with the SEC.

The forward-looking statements included in this communication are made only as of the date hereof. ACELYRIN assumes no obligation and does not intend to update these forward-looking statements, even if new information becomes available in the future, except as required by law.

Additional Information and Where to Find It

In connection with the proposed merger, Alumis intends to file with the SEC the registration statement, which will include the joint proxy statement/prospectus. After the registration statement has been declared effective by the SEC, the joint proxy statement/prospectus will be delivered to stockholders of Alumis and ACELYRIN. BEFORE MAKING ANY VOTING OR INVESTMENT DECISION, SECURITY HOLDERS OF ALUMIS AND ACELYRIN ARE URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS (INCLUDING ALL AMENDMENTS AND SUPPLEMENTS THERETO) AND OTHER DOCUMENTS RELATING TO THE MERGER THAT WILL BE FILED WITH THE SEC WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED MERGER. Investors and security holders will be able to obtain copies of the joint proxy statement/prospectus (when available) and other documents filed by Alumis and ACELYRIN with the SEC, without charge, through the website maintained by the SEC at www.sec.gov. Copies of the documents filed with the SEC by Alumis will be available free of charge under the SEC Filings heading of the Investor Relations section of Alumis’ website at https://investors.alumis.com/. Copies of the documents filed with the SEC by ACELYRIN will be available free of charge under the Financials & Filings heading of the Investor Relations section of ACELYRIN’s website at https://investors.acelyrin.com/.

Participants in the Solicitation

Alumis and ACELYRIN and their respective directors and executive officers may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about Alumis’ directors and executive officers is set forth in the registration statement, which includes the joint proxy statement/prospectus. Information about ACELYRIN’s directors and executive officers is set forth in ACELYRIN’s Annual Report on Form 10-K, which was filed with the SEC on March 19, 2025. Stockholders may obtain additional information regarding the interests of such participants by reading the registration statement and the joint proxy statement/prospectus and other relevant materials filed with the SEC regarding the proposed merger when they become available. Investors should read the joint proxy statement/prospectus carefully before making any voting or investment decisions.

No Offer or Solicitation

This communication shall not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.


	ACELYRIN, INC.
Date: April 21, 2025

	By:	/s/ Amar Murugan
	Name:	Amar Murugan
	Title:	Chief Legal Officer

ACELYRIN, Inc. 8-K