BB-301 for oculopharyngeal muscular dystrophy

Last updated Aug. 8, 2025, by Marisa Wexler, MS
Fact-checked by José Lopes, PhD

What is BB-301 for oculopharyngeal muscular dystrophy?

BB-301 is an experimental gene therapy designed to ease dysphagia, or difficulty swallowing, in people with oculopharyngeal muscular dystrophy (OPMD). The treatment is being developed by Benitec Biopharma, and is administered by injection into throat muscles during a one-time surgical procedure.

OPMD is a rare type of muscular dystrophy marked by muscle weakness mainly in the upper eyelids and throat. It is caused by a mutation in the PABPN1 gene.

BB-301 is designed to use what is known as a silence-and-replace strategy, where it delivers a healthy copy of the PABPN1 gene to muscle cells while simultaneously using a strategy known as RNA interference that will target for destruction messenger RNA molecules made from the mutated PABPN1 gene. Messenger RNA is an intermediary molecule that is used as a template to make a protein.

The therapy delivers its genetic payload using a virus, called adeno-associated virus serotype 9 (AAV9), that’s been engineered to deliver therapeutic genes instead of causing infection.

Therapy snapshot

How will BB-301 be administered?

In an early clinical trial in OPMD patients, BB-301 is being administered by multiple injections directly into two throat muscles, the middle pharyngeal constrictor and the inferior pharyngeal constrictor. This one-time administration is done via an open surgical procedure conducted under general anesthesia.

BB-301 in clinical trials

Benitec is currently conducting a Phase 1b/2a clinical trial (NCT06185673) to test BB-301 in people with OPMD, who are 65 years or younger, with moderate swallowing issues. To be eligible for the trial, patients must first complete at least six months of follow-up in a separate natural history study, where disease progression is being monitored in the absence of treatment.

The study’s Phase 1b part is designed to test up to three different doses of BB-301 in up to 18 participants, and the Phase 2a part will assess the optimal dose in up to 12 additional patients.

Interim data from the first three participants indicated BB-301 treatment led to improvements in swallowing ability. Interim safety data from the first five patients given a low dose have been generally favorable, with no severe side effects reported.

BB-301 side effects

Since BB-301 is still in early stages of development, its side effect profile is still largely unknown. One of the first OPMD patients given the therapy in a trial experienced moderate gastroesophageal reflux disease (commonly called acid reflux or heartburn) that went away with time.

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