Beam cut mutant Z-AAT by 84% in alpha-1 patients

Beam Therapeutics presented updated results from the Phase 1/2 trial of BEAM-302 in a late-breaking oral session at the European Respiratory Society Congress in Barcelona on 8 September 2026. BEAM-302 is a base editor delivered in a lipid nanoparticle to the liver, where it rewrites the PiZ point mutation in SERPINA1 that causes alpha-1 antitrypsin deficiency.

The presentation covered 29 patients from the dose-escalation portion, with follow-up of up to 18 months. In the 60 mg cohorts, circulating mutant Z-AAT fell by 84% in both Part A and Part B. Total circulating alpha-1 antitrypsin at steady state reached a mean of 14.4 micromolar in Part A, against a baseline of 5.0 micromolar, and 13.5 micromolar in Part B against a baseline of 4.7. As of 17 August 2026, 38 patients had been dosed across both parts.

Infusion-related reactions, mild to moderate, occurred in 41% of patients. One patient had transient Grade 3 liver enzyme elevations.

Beam has selected 60 mg for a global pivotal cohort that began dosing in July 2026 and expects to enroll roughly 50 more patients, seeking accelerated approval on a 12-month biomarker endpoint.