Full Press Release Details
Disclaimer 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. Alumis 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 of 1933, as amended. 2
Executive Summary The Alumis Merger Provides Significant Potential
Upside For ACELYRIN Stockholders The combination provides the opportunity to participate in the potential upside from Phase 3 data for Alumis' lead program expected in 1Q26 and a combined pipeline with multiple upcoming milestones
expected, with ACELYRIN stockholders retaining significant (~48%) ownership of the combined company, on a fully diluted basis The pro forma discounted cash flow analysis reviewed by the ACELYRIN board implies a range of illustrative pro
forma equity values per share of ACELYRIN common stock of $6.90 to $8.96 1 (inclusive of realized net synergies) based on the Pro Forma DCF analysis reviewed in the February 6, 2025 Presentation and adjusted for the improved 4/21 terms Prior
to the announcement of the strategic merger with Alumis, the market valued ACELYRIN at less than cash value despite Lonigutamab's potential to be a differentiated medicine in a large and growing market The ACELYRIN board believes that
the combination with Alumis will be significantly value accretive to ACELYRIN stockholders as a result of synergies and scale to be achieved through the proposed merger as well as reduced execution risk versus a standalone path as a single asset
company Combination Creates a Leading Clinical-Stage Immunology Company with a Diversified Portfolio of Product Candidates Combination with Alumis is the best path forward to unlock Lonigutamab's value and the combined company is
well-capitalized with runway through impactful catalysts into 2027 Combined company's management team is well-positioned to execute and create value, including by unlocking the value of Lonigutamab. Alumis has meaningful ophthalmology
expertise-its Chief Medical Officer was the CMO and co-founder of Viela Bio and its Chief Commercial Officer ran the TEPEZZA franchise at Amgen / Horizon Members of ACELYRIN's Lonigutamab team are expected to join Alumis
(clinical, CMC and regulatory) Combined company is well-positioned relative to publicly traded clinical-stage immunology peers, with the potential for significant upside Independent Board Committee Ran a Thorough Process to Review Multiple
Alternatives and Optimize Terms From Alumis The transaction process was spearheaded by an independent and highly accomplished Transaction Committee with extensive financial and biopharmaceutical company experience The Transaction
Committee secured multiple improvements in deal terms, including increasing ownership in the combined company from 40% to 48%, despite a declining ACELYRIN share price This process included interactions with ~25 potential counterparties over
~7 months, the exploration of a wide variety of potential transactions, robust evaluation of additional offers that emerged post signing of the definitive merger agreement, improved deal terms post signing of the 2/6 merger agreement in response to
stockholder feedback and is unanimously recommended and approved by the disinterested and independent directors The ACELYRIN Board is confident the Alumis strategic merger maximizes the potential value for ACELYRIN stockholders 1. The Joint
Proxy/Prospectus contains a detailed summary of the financial analyses performed by Guggenheim Securities, LLC ("Guggenheim Securities") in connection with its February 6, 2025 presentation to the ACELYRIN board (the "February 6,
2025 Presentation"). Guggenheim Securities' analyses were subject to the assumptions made, procedures followed, matters considered and limitations, qualifications and other conditions contained in the February 6, 2025 Presentation and
related fairness opinion and were necessarily based on economic, business, capital markets and other conditions, and the information made available to Guggenheim Securities, as of the date of such presentation and fairness opinion. Range of
illustrative pro forma equity values per share of ACELYRIN common stock reflects the revised exchange ratio of 0.4814x (the Improved Exchange Ratio ) in lieu of the original exchange ratio of 0.4274x (the Original Exchange Ratio ) used in the
February 6, 2025 Presentation. 3
The Alumis Merger Provides Significant Potential Upside For ACELYRIN
At Time of IPO, Investors Expected to Benefit from a Robust Pipeline but
Several Clinical Setbacks and Management Departures Have Impacted Growth Prospects Overview Limited Pipeline Remaining From Time of IPO Stage at IPO ACELYRIN IPO'd in May 2023 based on Phase 2b/3 Part A data for PC Ph1 Ph2 Ph3 Current
Status Izokibep ("Izo") in Hidradenitis Suppurativa ("HS") Izokibep (anti-IL-17A) HS Hidradenitis Suppurativa Sept-23: Failed Ph2b/3 Part B Izo is a next generation anti-IL-17A mAb Psoriatic Arthritis PsA Mar-24: Data
not competitive At the time of IPO, IL-17 was already a commercially validated target Ax Axial Spondylarthritis Aug-24: Suspended development based on Novartis' Cosentyx ($4.8B FY22) and Lilly's Taltz ($2.5B FY22) Spa UV Uveitis
Dec-24: Failed Ph2b/3 Humira was the only biologic approved for HS at that time with Lonigutamab (anti-IGF-1R) Cosentyx approved for HS shortly after SLRN's IPO in Oct-23 TED Thyroid Eye Disease Development plan to be finalized
Izo was designed, based on 4 major hypotheses, to overcome SLRN-517 (anti-c-KIT) limitations of prior generation IL-17s CSU Chronic Urticaria Jan-24: Divested 1. Higher affinity to IL-17A could translate to higher potency vs. Cosentyx Limited Senior
Management Remaining From Time of IPO 2. Smaller molecular size could allow for better tissue penetration 3. Targeting IL-17A vs. IL-17F could lower rates of candidiasis and toxicity Name Position at IPO Current Position 4. Albumin binding could
support longer half life vs. Cosentyx Shao-Lee Lin, M.D., Ph.D. Founder, CEO May-24: Departed Izo ultimately suffered clinical setbacks which led to discontinuation Mardi Dier CFO & CBO Aug-23: Departed of further development by ACELYRIN
Melanie Gloria COO Oct-24: Departed Sept-23: Failed to achieve stat. sig. in Part B of the HS Ph2b/3 study Mina Kim CLO CEO Mar-24: Achieved stat. sig. in Psoriatic Arthritis ("PsA") but not Ron Oyston CPO Aug-24:
Departed competitive vs. UCB's bimekizumab Paul Peloso, M.D. CMO Dec-23: Departed Dec-24: Failed to achieve stat. sig. in Uveitis Ph2b/3 study Remaining Programs / Personnel Source: Public company filings and Wall Street Equity
ACELYRIN Shares Have Been Under Significant Pressure Since Phase 2b/3
Part B Izokibep Data in Hidradenitis Suppurativa ("HS") in September 2023 After additional readouts, Izokibep was deprioritized and ACELYRIN is focused on Lonigutamab Lonigutamab has the potential to be a best-in-class
next-generation subcutaneous anti-IGF-1R therapy in Thyroid Eye Disease ("TED") Capitalization ($ in Millions Except Per Share Values) Unaffected Share Price (2/6/25) $1.90 9/11/23: Izokibep $30.00 Performance from IPO (89%) failed to
meet Equity Value $199 primary endpoint in 1 (448) Less: 4Q24 Cash and Cash Equivalents Part B of the Ph2b/3 Enterprise Value ($249) study in HS 11% $20.00 1/6/25: Additional Ph1b/2 data 11/27/23: Announced and Ph3 development plan for CRO
programming Lonigutamab announced error in Izokibep Ph2b/3 5/4/23: IPO trial in PsA 12/10/24: Data from 2/6/25: 5/9/24: Prior CEO exited & priced at Ph2b/3 study of $10.00 Alumis strategic Mina Kim appointed CEO $18/share Izokibep in Uveitis
merger announcement ACELYRIN 3/11/24: Data from Ph2b/3 $1.90 trial of Izokibep in PsA and XBI long-term HS data (89%) $0.00 May-23 Jul-23 Oct-23 Dec-23 Mar-24 Jun-24 Aug-24 Nov-24 Feb-25 Source: Public company filings and FactSet as of 2/6/25.
Strategic Alternatives Process 1. Cash, cash equivalents and marketable securities. 6
ACELYRIN's Board Believes Lonigutamab has the Potential to be a
Differentiated Medicine in a Large and Growing Market Product Profile Market Opportunity Efficacy in-line with IV anti-IGF-1R agents Minimally penetrated U.S. market Proptosis response in line with others, within the limitations of a small
dose Estimated penetration of today's standard of care <10% of patients but still escalation study 1 ~$2B annual sales Novel MoA and optimized PK support safety differentiation Potential lower risks of hearing impairment, menstrual
disorders and hyperglycemia Current standard of care has serious side effects Demonstrated adverse reactions occurring in 5% of treated patients include muscle spasms, nausea, alopecia, hearing impairment and hyperglycemia Delivered via a
low-volume auto-injector for at home 2 and menstrual disorders were reported in ~23% of menstruating women administration In distinction to the higher volume Amgen subcutaneous (SC) product Development plan may create additional flexibility for
Market is growing and large enough to support multiple prescribers medicines Potential to be used chronically and/or episodically, inclusive of patients with Limited availability of a biologic option for ~80K patients based on today's
age-appropriate hearing loss, pre-diabetic and diabetic patients and women 3 standard of care of childbearing potential Lonigutamab delivers efficacy like others in its class, with the potential to be safer and may be developed in a way that
differentiates 4 it and expands the market 1. ACELYRIN transcript from January 6, 2025 Special Call and Amgen SEC filings. 3. ACELYRIN January 6, 2025 presentation. 2. Tepezza prescribing information. 4. This claim is not based on head-to-head or
comparator studies. Differences exist between study designs and subject characteristics, and caution should be exercised when comparing data across studies. 7
And that the Market Was Not Reflecting the Potential Upside for
ACELYRIN 1 ACELYRIN Equity Value / Equity Value Per Share Post-Ph3 TED Trading Comp $2.3B / $20.00 2 $1.9B $1.2B Enterprise Value $602M / $5.68 $448M / $4.28 $481M / $4.59 $199M / $1.90 $314M / $3.00 Implied Per Share Price Reflected in 2/6
Unaffected Analyst Price Targets 3 4Q24 Cash ACELYRIN Standalone DCF Analysis in 5 Trading Price as of 2/6 as of 2/6 4 the February 6, 2025 Presentation 1. Viridian's lead asset Veligrotug, is a derisked anti-IGF-1R for TED with Phase 3
topline data and BLA submission expected in the second half of 2025. 2. Market capitalization inclusive of full conversion of outstanding Series A and Series B Preferred Stock to common stock. 3. Illustrative ACELYRIN valuation where market cap is
equivalent to the 4Q24 cash, cash equivalents and marketable securities on the balance sheet, implying $0 enterprise value, or in other words, no assigned value for Lonigutamab. 4. The Joint Proxy/Prospectus contains a detailed summary of the