— Unprecedented data from FORTITUDE™ dose escalation cohorts for del-brax treated participants, compared to placebo, demonstrate improvement in function, strength and PROs as well as rapid and significant reduction in biomarkers —
— Data support planned accelerated approval BLA submission in H2 2026 —
— Data being presented at the 32nd Annual FSHD Society International Research Congress (IRC); Investor and analyst webcast event today, Monday, June 9 at 8:00 a.m. ET —
Avidity Biosciences, Inc. (Nasdaq: RNA), a biopharmaceutical company committed to delivering a new class of RNA therapeutics called Antibody Oligonucleotide Conjugates (AOCs™) to profoundly improve people’s lives, today announced positive topline data from the dose escalation cohorts of the delpacibart braxlosiran (del-brax) Phase 1/2 FORTITUDE™ program in Facioscapulohumeral Muscular Dystrophy (FSHD). These data as well as research supporting KHDC1L as a novel DUX4 regulated circulating biomarker will be presented in oral and poster presentations at the 32nd Annual FSHD Society International Research Congress (IRC), being held June 12-13, 2025, in Amsterdam, the Netherlands.
Del-brax is the first investigational therapy designed to treat the underlying cause of FSHD by directly targeting the disease-causing gene, double homeobox 4 (DUX4). Currently, there are no approved therapies for the treatment of FSHD, a rare, hereditary disorder marked by life-long, relentless loss of muscle strength and function, significant pain, fatigue, and progressive disability. FSHD affects approximately 45,000 to 87,000 people in the United States and Europe.
“The positive topline del-brax results from FORTITUDE being presented at FSHD IRC this week are remarkable and consistent across multiple functional measures as well as biomarkers,” said Sarah Boyce, president and chief executive officer at Avidity. “Based on these unprecedented data, we are rapidly advancing del-brax as we pursue accelerated approval and prepare to submit a BLA in the second half of 2026. We are incredibly grateful for the continued trust and support from study participants, their caregivers, investigators and their staff, which are paramount to the success of this program.”
Avidity today also announced that the accelerated approval regulatory pathway in the U.S. is open for del-brax and that the company has initiated the global, confirmatory Phase 3 FORWARD™ study in FSHD.
“Del-brax data from the FORTITUDE study continue to demonstrate consistent reductions in a novel circulating biomarker across two cohorts at 12 months. I am particularly encouraged that del-brax shows favorable safety and tolerability with early and consistent trends towards benefit with del-brax compared to placebo across multiple functional and participant-reported outcome measures,” said Jeffrey M. Statland, M.D., Professor of Neurology, University of Kansas Medical Center, and FORTITUDE trial investigator. “These data indicate that by directly targeting DUX4, del-brax may be able to improve the lives of patients with FSHD and potentially meaningfully control their disease. I look forward to continued evaluation of del-brax in the FORWARD Phase 3 study and remain hopeful that it is on track to become the potentially first approved drug for FSHD.”
Topline Data from the Phase 1/2 FORTITUDE™ Dose Escalation Cohorts
The FORTITUDE™ clinical development program includes a randomized, placebo-controlled, double-blind, Phase 1/2 clinical trial designed to evaluate multiple doses of del-brax in participants with FSHD as well as an open-label extension study. The two dose escalation cohorts evaluated 39 participants on either 2 mg/kg or 4 mg/kg of del-brax versus placebo over a period of 12 months. In these cohorts, del-brax was given every six weeks for the first three months and then every 13 weeks thereafter.
Topline data from these cohorts for del-brax treated participants, compared to placebo, demonstrated:
- Consistent improvement of functional mobility and muscle strength as measured by 10-Meter Walk-Run test (10MWRT), Timed Up and Go (TUG) and quantitative muscle testing (QMT) as compared to placebo;
- Consistent improvement in multiple measures of quality of life as measured by patient reported outcomes and compared to placebo;
- Rapid and significant reductions in levels of KHDC1L and creatine kinase, a biomarker of muscle damage; and
- Favorable long-term safety and tolerability with most adverse events (AEs) mild or moderate, with no related serious or severe adverse events and no discontinuations.
Topline data from the ongoing, fully enrolled del-brax Phase 1/2 FORTITUDE biomarker cohort are anticipated in Q2 2026. The primary endpoint of the FORTITUDE biomarker cohort is reduction of KHDC1L, a novel DUX4-regulated circulating biomarker. Avidity collaborated with Stephen Tapscott, M.D., Ph.D., Professor of Human Biology and Clinical Research at the Fred Hutchinson Cancer Center around the identification of the KHDC1L circulating biomarker in people living with FSHD.
Video Webcast Information
The Company is hosting an investor and analyst event today, June 9, 2025 at 8:00 a.m. ET. Avidity management will be joined by Jeffrey M. Statland, M.D., Professor of Neurology, University of Kansas Medical Center, and FORTITUDE™ trial investigator, to discuss these updates relating to del-brax in FSHD. The virtual event will be available via a live video webcast and can be accessed here or from the “Events and Presentations” page in the “Investors” section of Avidity’s website. A replay of the webcast will be archived on Avidity’s website following the event.
