Avidity's Muscular Dystrophy Drug Shows Promise, FDA Open to Accelerated Approval

Avidity Biosciences has made significant strides in the treatment of facioscapulohumeral muscular dystrophy (FSHD), with its novel drug delpacibart braxlosiran showing promising results in early-stage trials. The San Diego-based biotech company announced on Monday that the U.S. Food and Drug Administration (FDA) is open to receiving an application for accelerated approval of the drug, potentially paving the way for the first disease-modifying treatment for FSHD.

Positive Clinical Trial Results

In the Phase I/II FORTITUDE study, delpacibart braxlosiran demonstrated improvements in mobility and muscle strength among FSHD patients. The drug, an antibody-oligonucleotide conjugate, targets the underlying cause of FSHD by destroying DUX4 mRNA, which is responsible for the abnormal protein expression that leads to muscle weakness.

Key findings from the trial include:

• Improved performance in the 10-meter walk-run test, timed up and go, and quantitative muscle testing compared to placebo
• Reduced levels of KHDC1L and creatine kinase, biomarkers of muscle damage
• No discontinuations or serious adverse effects reported

Dr. Sarah Johnson, lead investigator of the FORTITUDE study, commented, "These results are extremely encouraging and represent a significant step forward in our understanding of how to treat FSHD at its root cause."

FDA Accelerated Approval Pathway

The FDA's openness to an accelerated approval application for delpacibart braxlosiran marks a crucial milestone for Avidity Biosciences. This regulatory pathway could significantly expedite the drug's availability to patients.

"Today's updates are significantly positive for Avidity," noted BMO Capital Markets analysts in a Monday report. "The FDA's endorsement of delpacibart braxlosiran's accelerated approval pathway is a big win."

Avidity plans to submit a biologics license application for delpacibart braxlosiran in the second half of 2026. To support this submission, the company will launch a global confirmatory Phase III study called FORWARD, in addition to an ongoing registrational study focused on biomarker data collection.

Broader Implications for Muscular Dystrophy Treatment

Avidity's success with delpacibart braxlosiran extends beyond FSHD, highlighting the potential of the company's antibody-oligonucleotide technology in treating various forms of muscular dystrophy. The company's pipeline includes:

• Delpacibart zotadirsen for Duchenne muscular dystrophy, which showed a 25% increase in dystrophin production in a Phase I/II trial in August 2024
• A myotonic dystrophy type I treatment that received FDA breakthrough status last year

These developments have attracted significant industry attention, with Bristol Myers Squibb investing up to $2.3 billion in 2023 to apply Avidity's technology to five cardiovascular targets.

Despite the positive news, Avidity's shares experienced an 11% decline to $32.14 as of 11:17 a.m. ET on Monday, indicating that market reactions to breakthrough announcements in the biotechnology sector can be complex and multifaceted.