ACELYRIN, INC. Announces Lonigutamab Phase 1/2 Proof-Of-Concept Data to be Shared During Late-Breaking Oral Presentation at ENDO 2024

ACELYRIN, INC. (Nasdaq: SLRN), a late-stage clinical biopharma company focused on accelerating the development and delivery of transformative medicines in immunology, today announced that positive proof-of-concept data from an ongoing Phase 1/2 trial of lonigutamab in thyroid eye disease (TED) will be shared as a late breaking oral presentation at the Endocrine Society’s Annual Meeting (ENDO 2024), taking place from June 1-4 in Boston, MA. Lonigutamab is a subcutaneously (SC) delivered humanized IgG1 monoclonal antibody targeting the insulin-like growth factor-1 receptor (IGF-1R). Inhibition of IGF-1R is the only FDA-approved mechanism of action for the treatment of TED.

Presentation details are as follows:

Title: Preliminary Safety And Efficacy Of Subcutaneous Lonigutamab (anti-IGF-1R) From A Phase 1/2 Proof Of Concept Study In Patients With Thyroid Eye DiseaseDate/Time: Monday, June 3; 2:00pm - 2:15pm ETPresenter: Dr. Shoaib Ugradar, Department of Orbital and Oculoplastic Surgery, Private Practice; The Jules Stein Eye Institute, University of California

About the Phase 1/2 TrialThe Phase 1/2 clinical trial (NCT05683496) is a multi-center trial evaluating the safety and efficacy of lonigutamab dosed subcutaneously in three cohorts of patients with active thyroid eye disease (TED). Cohort 1 is placebo-controlled testing lonigutamab 40mg every three weeks (Q3W) through six weeks, cohort 2 is open label testing a 50mg loading dose followed by 25mg every week (QW), and cohort 3 is open label testing every four weeks (Q4W) dosing.

For more information about the Phase 1/2 trial, please visit www.clinicaltrials.gov.

About Thyroid Eye DiseaseThyroid Eye Disease (TED) is a vision-threatening autoimmune disease in which there is both inflammation and expansion of the tissues behind the eye, resulting in eye bulging – known as proptosis – that may result in the subsequent inability to close the eyelids. Double vision, or diplopia, can occur, as well as the potential for compression of the retinal nerve, which can lead to blindness. Thus, TED is a progressive, chronic inflammatory disease where longer-term treatment has the potential to improve depth and durability of response. More than 100,000 people in the United States are estimated to suffer from TED.

About Lonigutamab (anti-IGF-1R)Lonigutamab is a humanized IgG1 monoclonal antibody targeting the IGF-1 receptor and is delivered subcutaneously. Relative to standard of care, lonigutamab binds to a distinct epitope, which results in internalization of the receptor within minutes, and in preclinical binding and functional laboratory assays, it has been shown to be 75-fold more potent. The characteristics of lonigutamab that enable subcutaneous delivery may also enable the potential for longer-term dosing, which we believe may improve depth and durability of clinical response. Based on our preclinical and pharmacodynamic data from our completed single ascending dose study with lonigutamab, we can potentially optimize the therapeutic window utilizing the SC route of administration.

About ACELYRIN, INC.ACELYRIN, INC. (Nasdaq: SLRN) is a Los Angeles area-based late-stage clinical biopharma company – with additional operations in the San Francisco Bay area – focused on providing patients life-changing new treatment options by identifying, acquiring, and accelerating the development and commercialization of transformative medicines. ACELYRIN has two programs in late-stage clinical development. Lonigutamab is a subcutaneously delivered monoclonal antibody targeting IGF-1R advancing into Phase 2b/3 development for the treatment of thyroid eye disease. Izokibep is a next generation inhibitor of IL-17A in Phase 2b/3 development for the treatment of psoriatic arthritis, hidradenitis suppurativa and uveitis.

For more information about ACELYRIN, visit us at www.acelyrin.com or follow us on LinkedIn and X.

Forward Looking Statements This press release contains forward-looking statements including, but not limited to, statements related to ACELYRIN’s expectations regarding its cash runway and sufficiency of its cash resources; ACELYRIN’s plan to take lonigutamab through late-stage development milestones; the potential future success of ACELYRIN’s izokibep program; anticipated development activities including the planned initiation and timing of clinical trials, and/or the availability of clinical data; the therapeutic potential of ACELYRIN’s product candidates; and other statements that are not historical fact. These forward-looking statements are based on ACELYRIN’s current plans, objectives and projections, and are inherently subject to risks and uncertainties that may cause ACELYRIN’s actual results to materially differ from those anticipated in such forward-looking statements. Such risks and uncertainties include, without limitation, those associated with the successful completion of development and regulatory activities with respect to ACELYRIN’s product candidates; the timing and results of ACELYRIN’s clinical trials, including the risk that future clinical trial results could differ materially and adversely from prior clinical trial results or data; maintaining and defending intellectual property protection; delays or failures to secure adequate supply of its product candidates; ACELYRIN’s failure to realize the expected benefits of its acquisition of additional programs; legal proceedings and other risks and uncertainties affecting ACELYRIN including those described from time to time under the caption “Risk Factors” and elsewhere in ACELYRIN’s current and future reports filed with the Securities and Exchange Commission, including its Annual Report on Form 10-K for the year ended December 31, 2023. Forward-looking statements contained in this press release are made as of this date, and ACELYRIN undertakes no duty to update such information except as required under applicable law.

ACELYRIN Contacts:Tyler MarciniakVice President of Investor Relations,Communications and [e-mail] [e-mail]