Satellos Bioscience (MSCL) Study update summary

Study design and patient population

• TRAILHEAD is an open-label Phase 2 study in adults with Duchenne muscular dystrophy (DMD), aiming to enroll up to 30 participants, with current six-month interim results from four adults aged 21–28, all previously enrolled in the CL-101 study.

• Participants received 60 mg SAT-3247 orally, five days on, two days off, for up to 12 months, with primary endpoints of safety, tolerability, and biceps brachii fat fraction by MRI.

• Secondary and additional endpoints included muscle composition, strength, function, spirometry, quality of life, health economic impact, and biomarkers.

• Six-month data reflect 186 days mean drug exposure with 100% compliance.

• The study is ongoing, with 12-month data expected in Q4 2026.

Efficacy and safety outcomes

• Mean biceps brachii fat fraction improved by 3.7 percentage points over six months, contrary to expected natural history worsening.

• All participants showed increased upper limb effort (TE99C), with a mean improvement of 34%.

• Muscle strength remained stable, maintaining prior handgrip gains despite a treatment gap.

• Creatine kinase levels declined by 38%, indicating reduced muscle damage.

• All adverse events were mild or moderate, with no serious events, withdrawals, or discontinuations, and 100% treatment compliance.

Functional and patient-reported outcomes

• Performance of the upper limb (PUL/PUL2.0) scores were stable or improved in all participants, with no declines observed.

• Patient-reported fatigue (PedsQL-MFS) improved by nearly 7 points, suggesting better quality of life.

• Real-world activity, as measured by wearable sensors, showed consistent improvement.

• Upper extremity strength remained stable across all measures, including handgrip and dynamometry.

• Consistent improvements across imaging, biomarkers, effort, strength, and function reinforce the biologic activity of SAT-3247.