Avidity Biosciences Announces the Accelerated Approval Regulatory Pathway in the U.S. is Open for Del-Brax and Initiates the Global, Confirmatory Phase 3 FORWARD™ Study in FSHD

Avidity Biosciences announced plans to submit a Biologics License Application (BLA) in the second half of 2026 for accelerated approval of delpacibart braxlosiran (del-brax) for facioscapulohumeral muscular dystrophy (FSHD), following topline data from the FORTITUDE™ biomarker cohort expected in Q2 2026. The FDA has provided guidance on validating a surrogate biomarker for accelerated approval, as there are currently no approved treatments for FSHD, a rare genetic disorder causing progressive muscle loss. Avidity has also initiated a global, confirmatory Phase 3 FORWARD™ study to evaluate del-brax 2mg/kg every six weeks, aiming for full approval.

Analysis

Avidity Biosciences (RNA) has outlined a clear regulatory and clinical pathway for delpacibart braxlosiran (del-brax), its investigational Antibody Oligonucleotide Conjugate (AOC™) therapy for Facioscapulohumeral Muscular Dystrophy (FSHD). The company intends to submit a Biologics License Application (BLA) for accelerated approval in the second half of 2026, contingent upon positive topline data from the FORTITUDE™ biomarker cohort, anticipated in Q2 2026. This is a significant step as del-brax is designed to target the underlying genetic cause of FSHD (DUX4 gene expression) and there are currently no approved treatments for this rare disease, which affects an estimated 45,000 to 87,000 individuals. The U.S. Food and Drug Administration (FDA) has provided specific guidance regarding the validation of the surrogate biomarker, KHDC1L, for this accelerated approval pathway, which allows for earlier drug approval based on markers predictive of clinical benefit. To support eventual full approval, Avidity has initiated the global, confirmatory Phase 3 FORWARD™ study, an 18-month, randomized, placebo-controlled trial designed to evaluate del-brax at a 2mg/kg dose every six weeks in approximately 200 patients. The progression of del-brax, which has received Orphan Drug and Fast Track designations, underscores Avidity's focus on rare neuromuscular diseases and its pioneering work with AOC™ technology for targeted RNA delivery.

Key Decisions for Investors

• Investors should closely monitor the Q2 2026 topline data from the FORTITUDE™ biomarker cohort, as this will be a pivotal catalyst for Avidity's planned H2 2026 BLA submission for del-brax under the accelerated approval pathway.
• The dual strategy of pursuing accelerated approval based on surrogate biomarker data while concurrently running the Phase 3 FORWARD™ confirmatory trial presents both an opportunity for earlier market entry and a longer-term validation pathway; the success of both will be crucial for del-brax's ultimate commercial potential in addressing the significant unmet need in FSHD.
• While the FDA guidance on the surrogate biomarker is a positive development, continued diligence is required regarding the inherent risks of clinical trials, the robustness of the biomarker in predicting clinical benefit, and the successful execution and outcome of the confirmatory Phase 3 study.