Announcement • Sep 08

Beam Therapeutics Presents Updated Clinical Data from the Phase 1/2 Trial of Beam-302 in Alpha-1 Antitrypsin Deficiency

Beam Therapeutics announced updated clinical data from the Phase 1/2 trial evaluating BEAM-302 for alpha-1 antitrypsin deficiency (AATD). BEAM-302 is Beam’s lead liver-targeted genetic disease program and a potentially best- and first-in-class therapy designed to directly correct the root cause of AATD and address both liver and lung manifestations of disease. BEAM-302 is being evaluated in a Phase 1/2, open-label, dose exploration and dose expansion clinical trial to investigate its safety, tolerability, pharmacodynamics, pharmacokinetics and efficacy. Part A is designed to evaluate patients with AATD-associated lung disease, and Part B evaluates patients with mild to severe liver disease, with or without lung disease. As of August 17, 2026, 38 patients have been dosed with BEAM-302 across Part A and Part B. The presentation at ERS included data from 29 patients treated with a single dose of BEAM-302 in the dose-escalation portion of the study: Part A (15 mg, n=3; 30 mg, n=3; 60 mg, n=6; 75 mg, n=9) and Part B (30 mg, n=3; 60 mg, n=5). Data from patients in the multi-dose cohort (n=3) and the Part A expansion cohort (n=6) were not included. As of the June 24, 2026, data cutoff date, treatment with single-dose BEAM-302 was well tolerated with an acceptable safety profile in both Part A and Part B cohorts. Mild-to-moderate infusion-related reactions (IRRs) were the most common drug-related treatment-emergent adverse events (TEAEs), occurring in 41% of all patients. Transient and predominantly Grade 1 alanine transaminase (ALT) and/or aspartate aminotransferase (AST) elevations were also observed. One Part B patient with underlying AATD-related liver disease treated with 60 mg BEAM-302 experienced transient Grade 3 ALT/AST elevations that were not accompanied by bilirubin increases and did not require treatment. Treatment with BEAM-302 led to rapid and durable increases of total and functional AAT, decreases in mutant Z-AAT and toxic Z-polymers, and new production of corrected M-AAT. Key findings from 29 efficacy-evaluable patients as of the June 24, 2026, data cutoff date include: A single dose of BEAM-302 of 60 mg led to sustained increases in total AAT above the 11 µM protective threshold. After treatment with a single dose of 60 mg BEAM-302 in Part A, the steady-state circulating total AAT mean and median were 14.4 µM and 15.2 µM, respectively, compared to 5.0 µM at baseline. In the Part B 60 mg cohort, the post-treatment steady-state circulating total AAT mean and median were 13.5 µM and 13.8 µM, respectively, compared to 4.7 µM at baseline. Increased total AAT in circulation was functional. Functional AAT levels increased in a dose-dependent manner up to 60 mg and were durable through follow-up. Human neutrophil elastase (HNE) activity levels, another measure of AAT function, decreased in a dose proportionate manner with BEAM-302 treatment, with >80% of patients in the Part A 60 mg cohort having at least one HNE activity measurement below the lower limit of quantification. Mutant Z-AAT was significantly and durably reduced after treatment with BEAM-302, with an 84% reduction in circulating Z-AAT in both Part A and Part B 60 mg cohorts. BEAM-302 also led to a significant decrease in circulating Z-AAT protein aggregates, referred to as Z-polymers, from baseline in the 60 mg cohort. Circulating Z-polymers have been shown to correlate with liver disease severity and to amplify lung inflammation by inducing neutrophil recruitment. Evidence of AAT protein production under normal physiologic control was observed during an upper respiratory tract infection in a patient in the Part A 60 mg cohort. Following treatment with BEAM-302, newly produced corrected M-AAT comprised the majority of AAT in circulation. The proportion of M-AAT at steady state was 93% following treatment with 60 mg in both Part A and Part B, exceeding the approximately 80% M-AAT proportion associated with the MZ genotype. Based on feedback from the U.S. Food and Drug Administration (FDA), Beam intends to pursue an accelerated approval pathway for BEAM-302 based on a primary endpoint of AAT biomarkers evaluated over 12 months, with 60 mg as the selected dose. To support a future biologics license application (BLA) submission, the company anticipates enrolling approximately 50 additional patients with AATD-associated lung disease, with or without liver disease, in an expansion of the ongoing open-label Phase 1/2 trial. In July, Beam dosed the first patient in this global pivotal cohort. BEAM-302 is a liver-targeting lipid-nanoparticle (LNP) formulation of base editing reagents designed to correct the PiZ mutation. Patients homozygous for this mutation (PiZZ) represent the majority of patients living with severe AATD disease. A one-time A-to-G correction of the PiZ mutation with Beam’s adenine base editor has the potential to simultaneously reduce the aggregation of mutant, misfolded AAT protein that causes toxicity to the liver (Z-AAT), generate therapeutic levels of corrected protein (M-AAT), and increase total and functional AAT in circulation, thereby addressing the underlying pathophysiology of both the liver and lung disease. In addition, the reduction in circulating PiZ has the potential to further minimize lung inflammation and dysfunction. Importantly, because BEAM-302 corrects the native AAT gene in its normal genetic location, AAT levels have been observed to increase physiologically in response to infection and inflammation in treated patients. This is a critical aspect of AAT’s normal function to regulate the body’s inflammatory response, which does not occur with currently approved protein replacement therapies. Correction of the PiZ mutation has been durable to date in patients treated in Beam's clinical trial.

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