FOP is an ultra-rare genetic disorder characterized by abnormal bone formation that infiltrates muscles, tendons, ligaments and other connective tissues, resulting in significant disability 

If approved, garetosmab would be the first and only available treatment shown to reduce the number and volume of new heterotopic bone lesions in adults with FOP

TARRYTOWN, N.Y., Feb. 19, 2026 (GLOBE NEWSWIRE) -- Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) today announced that the U.S. Food and Drug Administration (FDA) has accepted for Priority Review the Biologics License Application (BLA) for garetosmab for the treatment of adults with fibrodysplasia ossificans progressiva (FOP). Garetosmab is a monoclonal antibody that blocks Activin A, a protein that Regeneron scientists discovered to be critical in the development of heterotopic ossification (HO) lesions in people with FOP. The target action date for the FDA decision is August 2026.

FOP is a relentless, ultra-rare genetic disorder in which muscles, tendons, ligaments and other connective tissues are progressively infiltrated by abnormal bone formation, a process known as HO, which results in significant disfunction of these structures and skeletal deformity. HO of the jaw, spine, hip and rib cage can make it difficult to speak, eat, walk or breathe, leading to weight loss and escalating loss of mobility. Most people with FOP are wheelchair bound by 30 years old, and the median age of survival is approximately 56 years. Approximately 900 people are diagnosed with FOP worldwide, with many others thought to remain undiagnosed or misdiagnosed.

The BLA is supported by efficacy and safety data from the positive Phase 3 OPTIMA trial evaluating garetosmab in adults with FOP. Both garetosmab doses (3 mg/kg and 10 mg/kg) evaluated in the trial were highly efficacious in reducing the total number and volume of new HO lesions at 56 weeks, compared to placebo. Regarding the primary endpoint analysis of reduction in total number of new HO lesions compared to placebo (n=21), those receiving the 3 mg/kg dose (n=19) experienced a 94% reduction (1 lesion vs. 19 lesions; p=0.0274), while those receiving the 10 mg/kg dose (n=23) experienced a 90% reduction (2 lesions vs. 19 lesions; p=0.0260). A post-hoc analysis also found both doses of garetosmab demonstrated a greater than 99% reduction in mean total volume (cm³) of new HO lesions compared to placebo (3 mg/kg: 0.01 cm³ vs. 10.45 cm³; nominal p=0.0013; 10 mg/kg: 0.02 cm³ vs. 10.45 cm³; nominal p=.0005).

At 56 weeks, among all 63 people with FOP aged 18 years and older who participated in the OPTIMA trial, serious treatment-emergent adverse events occurred in 1 patient treated with 3 mg/kg garetosmab, 2 patients treated with 10 mg/kg garetosmab and 2 patients treated with placebo. The most common adverse reactions (incidence ≥30%) are epistaxis, increased hair growth, abscess and acne.

Priority Review is granted to regulatory applications seeking approval for therapies that have the potential to provide significant improvements in the treatment, diagnosis or prevention of serious conditions. The FDA previously granted Fast Track designation and Orphan Drug Designation for garetosmab for the prevention of HO in patients with FOP. Garetosmab has also been granted Orphan Designation in the European Union, and additional garetosmab regulatory submissions are planned in countries around the world.

The safety and efficacy of garetosmab, as well as its potential use for the treatment of FOP, are investigational and have not been fully evaluated or approved by any regulatory authority.

About the OPTIMA Clinical Trial
OPTIMA is a Phase 3, multi-center, multinational trial to assess the efficacy of garetosmab on the reduction of heterotopic bone formation, as well as its safety, tolerability, and pharmacokinetics, in patients with active FOP.

The trial enrolled 63 participants aged 18 years and older who have any FOP-causing variant of type I Activin A receptor (ACVR1), exhibited FOP disease activity or progression of HO lesions, and had a cumulative analogue joint involvement scale (CAJIS) score at screening of ≤19. CAJIS is a clinician-assessed tool, with higher scores representing greater disease severity (scale: 0 to 30). Eligible participants were randomized to intravenously receive 3 mg/kg garetosmab, 10 mg/kg garetosmab, or placebo once every four weeks for 56 weeks. Following this, participants could elect to extend their treatment for at least 84 weeks or discontinue treatment and enter an observation-only arm.

During the treatment period, efficacy was evaluated through whole body computed tomography (CT) scans for HO lesions; physician and patient assessment of flare-ups; utilization of CAJIS to rate joint functionality; and observances of change in disease severity. Safety assessment includes reports of adverse events, measurement of vital signs, physical examination, and coagulation testing.

A Phase 3 trial of garetosmab in adolescents and children with FOP, OPTIMA 2, is planned to begin later this year. For more information, visit the Regeneron clinical trials website, contact clinicaltrials@regeneron.com, or call +1 844-734-6643.

About Garetosmab
Regeneron has been engaged in FOP research for decades and helped to provide fundamental insights into the biology and natural history of the disease. Regeneron scientists discovered that Activin A plays a key role in FOP by driving HO, the main pathology of FOP. Garetosmab is a VelocImmune-derived, fully-human monoclonal antibody that binds and neutralizes Activin A, which is involved in the development of heterotopic bone in people with FOP.

About Regeneron’s VelocImmune Technology
Regeneron's VelocImmune technology utilizes a proprietary genetically engineered mouse platform endowed with a genetically humanized immune system to produce fully optimized human antibodies. When Regeneron's Co-Founder, President and Chief Scientific Officer George D. Yancopoulos was a graduate student with his mentor Frederick W. Alt in 1985, they were the first to envision making such a genetically humanized mouse, and Regeneron has spent decades inventing and developing VelocImmune and related VelociSuite^® technologies. Dr. Yancopoulos and his team have used VelocImmune technology to create a substantial proportion of all original, FDA-approved fully human monoclonal antibodies. This includes Dupixent^® (dupilumab), Libtayo^® (cemiplimab-rwlc), Praluent^® (alirocumab), Kevzara^® (sarilumab), Evkeeza^® (evinacumab-dgnb), Inmazeb^® (atoltivimab, maftivimab and odesivimab-ebgn) and Veopoz^® (pozelimab-bbfg). In addition, REGEN-COV^® (casirivimab and imdevimab) had been authorized by the FDA during the COVID-19 pandemic until 2024. Garetosmab was also created using Regeneron's VelocImmune technology.

About Regeneron
Regeneron (NASDAQ: REGN) is a leading biotechnology company that invents, develops and commercializes life-transforming medicines for people with serious diseases. Founded and led by physician-scientists, our unique ability to repeatedly and consistently translate science into medicine has led to numerous approved treatments and product candidates in development, most of which were homegrown in our laboratories. Our medicines and pipeline are designed to help patients with eye diseases, allergic and inflammatory diseases, cancer, cardiovascular and metabolic diseases, neurological diseases, hematologic conditions, infectious diseases, and rare diseases.

Regeneron pushes the boundaries of scientific discovery and accelerates drug development using our proprietary technologies, such as VelociSuite, which produces optimized fully human antibodies and new classes of bispecific antibodies. We are shaping the next frontier of medicine with data-powered insights from the Regeneron Genetics Center^® and pioneering genetic medicine platforms, enabling us to identify innovative targets and complementary approaches to potentially treat or cure diseases.

For more information, please visit www.Regeneron.com or follow Regeneron on LinkedIn, Instagram, Facebook or X.

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