Treatment with the experimental gene therapy BB-301 was found to improve swallowing ability for every person with a rare type of muscular dystrophy (MD) that mainly affects the throat and eyes who are taking part in a first-in-human clinical trial.
That’s according to new interim data announced by Benitec Biopharma, a U.S.-based company developing BB-301 for people with oculopharyngeal muscular dystrophy (OPMD), a form of MD marked by muscle weakness that mainly affects muscles around the eyes and in the throat. Benitec presented the findings at the Annual Congress of the European Society of Gene and Cell Therapy (ESGCT), held Oct. 27-30 in Hamburg, Germany.
“The progress we continue to see regarding both the safety and efficacy of BB-301 reinforces our conviction in the program and the potential to establish a new treatment paradigm for Patients suffering from OPMD-related dysphagia [swallowing problems],” Jerel A. Banks, MD, PhD, executive chairman and CEO of Benitec, said in a company press release announcing the positive data.
Dysphagia, or difficulty swallowing, is a hallmark symptom of this MD type — one that worsens over time. However, to date, no treatments to improve swallowing ability have won regulatory approval.
“Progressive loss of swallowing function has a devastating impact on OPMD Patients, yet there are no approved therapies to address this critical unmet medical need,” Banks said.
The CEO is one of the authors of the company’s ESGCT poster, which was titled “Durable Responses to Low-Dose Investigational Gene Therapy BB-301 in Patients with Oculopharyngeal Muscular Dystrophy (OPMD) with Dysphagia and Summary of Interim Clinical Results for High-Dose BB-301.”
OPMD is caused by mutations in the PABPN1 gene, which acts much like a quality-control manager and shipping coordinator for a cell’s genetic instructions.
BB-301 is a gene therapy that uses a strategy called silence-and-replace: Essentially, the treatment candidate aims to inactivate the mutated PABPN1 gene while simultaneously delivering a working copy of the gene to muscle cells. The therapy is designed to be given directly into throat muscles, with the aim of reducing dysphagia.
Developer planning pivotal trial of BB-301 gene therapy
To test the treatment, Benitec is sponsoring a Phase 1b/2a trial (NCT06185673) of BB-301 in people ages 65 and younger with OPMD. Enrollment is ongoing at a single study site in New York City.
Previously reported early data from the study had indicated the therapy was generally safe and improved swallowing ability in the first few patients tested.
The new update covers data from a total of nine patients treated with BB-301: Six given a low dose have now been followed for at least one year since treatment, and three given a higher dose have been tracked for at least three months. Updated safety data are still positive, according to the developer; no serious side effects have been documented in the study.
These data also show that all nine patients are formal responders to treatment — in other words, they all showed improvements in measures of swallowing ability as of the latest follow-up.
BB-301 is the first and only clinical stage gene therapy which has demonstrated durable, clinically meaningful improvements for OPMD-related dysphagia.
Specifically, the data show that, within three months of receiving BB-301 at either dose, all nine showed significant improvements on the Sydney Swallow Questionnaire (SSQ), a patient-reported measure of swallowing ability. At the same time, two-thirds of patients on either dose showed improvements in throat-closing ability, as measured using video-based assessments.
Video-based measures also showed that all three participants given the higher dose of BB-301 had better throat-emptying ability three months after treatment, and two of three had significant improvements on a test that measures swallowing ability by timing how long it takes to drink a specific amount of cold water.
Improvements in these measures were notably less common in the low-dose group, the data show. The researchers noted that two-thirds of patients — four of six — had improvements in throat emptying, and one improved in the cold water drink test.
According to the researchers, “BB-301 is the first and only clinical stage gene therapy which has demonstrated durable, clinically meaningful improvements for OPMD-related dysphagia.”
The ongoing study, slated to run through 2030, will continue to track long-term outcomes and test BB-301 in more patients. Meanwhile, Benitec is making plans for a pivotal clinical trial — a study designed such that positive results could support applications for regulatory approval. The company hopes to launch that trial next year.
“As we advance toward our pivotal study in mid-2027, we remain focused on the promise of delivering a potentially transformative therapy to the OPMD community,” Banks said.
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