Beam Therapeutics announces ‘positive’ data from study of BEAM-302

Beam Therapeutics (BEAM) announced initial safety and efficacy data from its Phase 1/2 trial of BEAM-302, establishing clinical proof-of-concept as a potential treatment for alpha-1 antitrypsin deficiency and for in vivo base editing. Preliminary results from the first three single-ascending dose cohorts demonstrated that BEAM-302 was well tolerated, with single doses of BEAM-302 leading to durable dose-dependent correction of the disease-causing mutation. Treatment with BEAM-302 was well tolerated with an acceptable safety profile at all dose levels explored to date. All adverse events were mild to moderate, with no serious AEs reported and no dose-limiting toxicities as of the data cutoff. Grade 1 asymptomatic alanine transaminase and aspartate aminotransferase elevations and transient Grade 1 infusion-related reactions were observed in some patients and did not require treatment. Following a single infusion of BEAM-302, rapid, durable, and dose-dependent increases in total AAT, new production of corrected M-AAT, and decreases in mutant Z-AAT were observed in circulation. Changes in total AAT were observed by turbidimetry assays as early as Day 7, plateaued around Day 21 and were maintained for the duration of follow-up. Increased total AAT was functional as determined by both neutrophil elastase inhibition and neutrophil elastase binding assays.