PepGen Reports Encouraging Phase II FREEDOM2 DM1 Data at 5 mg/kg; 10 mg/kg Cohort Underway

Biotech company sees positive safety, splicing, and functional trends in lowest-dose cohort of myotonic dystrophy type 1 trial.

Apr. 3, 2026 at 10:10am

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A translucent, ghostly X-ray photograph revealing the intricate structure of human muscle fibers and sinews, conveying the biological complexity of the condition targeted by PepGen's investigational therapy.A revealing X-ray view of the muscular system, highlighting the biological intricacies impacted by the rare genetic disorder myotonic dystrophy type 1.San Diego Today

PepGen, a clinical-stage biotech company, reported top-line results from the 5 mg/kg cohort of its Phase II FREEDOM2 study evaluating PGN-EDO-DM1 in myotonic dystrophy type 1 (DM1). The data showed encouraging safety, splicing, and functional trends, with the company now enrolling the 10 mg/kg cohort and planning to move to a 12.5 mg/kg cohort in 2027.

Why it matters

Myotonic dystrophy type 1 is a rare and debilitating genetic disorder that causes progressive muscle wasting and weakness. PepGen's investigational therapy PGN-EDO-DM1 aims to address the underlying genetic cause of the disease, providing hope for patients and families affected by this condition.

The details

In the 5 mg/kg cohort, PepGen reported no serious adverse events, no treatment-related kidney issues, and no cumulative dose toxicity. The most common adverse event was nausea, which did not worsen with multiple doses. Renal monitoring showed no significant changes, and transient albuminuria was observed in two subjects. On splicing correction, the treatment group showed a 7.3% improvement versus 6.8% in placebo, with one notable outlier showing a 70.8% worsening. Excluding that outlier, the mean splicing correction increased to 22.9% in the treatment group. The company also reported improvements in the vHOT measure of myotonia, though both placebo and treatment groups trended back toward baseline by the end of the study period.

  • PepGen has started dosing the 10 mg/kg cohort, with results expected in the second half of 2026.
  • The company plans to move to a 12.5 mg/kg cohort, with results expected in 2027.

The players

PepGen, Inc.

A clinical-stage biotechnology company headquartered in San Diego, California, developing precision gene editing therapies to address rare genetic diseases.

Paul Streck

Executive vice president and head of research and development at PepGen.

James McArthur

President and CEO of PepGen.

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What they’re saying

“All adverse events were mild or moderate with no serious adverse events, no treatment-related adverse events related to the kidney, and no cumulative dose toxicity through the four doses.”

— James McArthur, President and CEO, PepGen

“Nausea was the most common adverse event and 'did not get worse with multiple doses.' He also said there were no signs of hypersensitivity following administration.”

— Paul Streck, Executive Vice President and Head of Research and Development, PepGen

What’s next

PepGen has started dosing the 10 mg/kg cohort and expects to report clinical data from this next cohort in the second half of 2026. The company also plans to move to a third cohort at 12.5 mg/kg, with results from that cohort expected in 2027.

The takeaway

PepGen's encouraging data from the 5 mg/kg cohort of its Phase II FREEDOM2 study for PGN-EDO-DM1 in myotonic dystrophy type 1 provides hope for patients and families affected by this debilitating genetic disorder. The company's progress in advancing to higher dose levels and its plans for further clinical development demonstrate its commitment to addressing this unmet medical need.