Beam Therapeutics Announces Initial Data From Its Ongoing Phase 1/2 Clinical Trial Evaluating BEAM-301 For Treatment Of Glycogen Storage Disease Type Ia; In The 40 Mg Cohort, Two Patients Achieved 15 Hours Of Controlled Fasting; Safety Profile Of BEAM-301 Consistent With LNP-Based Therapies

The data will be presented during a poster session at the 33rd Annual Congress of the European Society of Gene and Cell Therapy (ESGCT) in Hamburg, Germany. BEAM-301 is an investigational liver-targeting lipid-nanoparticle (LNP) formulation of base editing reagents designed to correct the R83C mutation, one of the most prevalent disease-causing mutations in GSDIa and one that is associated with the most severe form of the disease.arch requirements provide encouraging evidence of BEAM-301’s potential to deliver meaningful and lasting benefits for patients."

BEAM-301 Phase 1/2 Clinical Trial Data Update

BEAM-301 is being evaluated in an open-label Phase 1/2 dose-exploration trial to investigate its safety, tolerability, pharmacodynamics, pharmacokinetics and efficacy in patients with GSDIa who are homozygous or compound heterozygous for the R83C variant. As of the August 17, 2026, data cutoff, six patients had received a single intravenous infusion of BEAM-301, including three patients treated with 20 mg and three patients treated with 40 mg. Median follow-up across both cohorts was 7.6 months (range: 1.9–16.6 months).

Key highlights include:

Safety Profile Consistent with LNP-Based Therapies: BEAM-301 demonstrated an acceptable safety profile consistent with LNP-based therapies, with no dose-limiting toxicities, Grade 4 or 5 treatment-emergent adverse events (TEAEs), or treatment discontinuations due to TEAEs reported. All patients experienced at least one TEAE considered related to BEAM-301. Four of six patients experienced serious TEAEs considered related to BEAM-301, including three Grade 3 infusion-related reactions (IRRs). Premedication with shorter-acting steroids, which are typically used in this patient population, may have contributed to the Grade 3 IRRs observed. The steroid premedication and infusion rate regimens have since been modified. Two other serious TEAEs of diarrhea and rhabdomyolysis occurred in two patients; both have resolved. With the exception of a single Grade 2 elevation in aspartate aminotransferase (AST), all transaminase elevations were Grade 1. All liver enzyme elevations resolved without treatment, and total bilirubin remained within normal limits.
Restoration of Endogenous Glucose Production Following a Single Treatment: BEAM-301 demonstrated dose-dependent improvements in time to fasting hypoglycemia (TTH), a key measure of glucose regulation in patients with GSDIa. Median TTH increased from 2.9 hours at baseline to 4.3 hours at Day 36 in the 20 mg cohort, and from 2.5 hours at baseline to 15.0 hours at Day 36 in the 40 mg cohort. Two of three patients in the 40 mg cohort achieved the protocol-defined maximum controlled fasting duration of 15 hours, consistent with restored endogenous glucose production. During the 15-hour fasting challenges, blood glucose levels were generally maintained within the euglycemic range. One patient in the 40 mg cohort did not show an increase in TTH at the first post-dose assessment; several factors may have contributed, including elevated body mass index (BMI) and heterozygosity for the R83C mutation.
100% Reduction in Daily Starch Supplementation Observed in Two Patients: Daily starch intake and daily number of starch doses generally decreased following treatment with BEAM-301 (baseline: 6–7 and 5–6 doses/day in the 20 mg and 40 mg cohorts, respectively), with two of three patients in the 40 mg cohort achieving a 100% reduction in daily starch requirements and no longer requiring starch supplementation at their latest reported assessments.
Improvements in Glucose Control Despite Reduced Starch Intake: Continuous glucose monitoring demonstrated increased time spent in the euglycemic range and decreased time in the hyperglycemic range following treatment with BEAM-301, despite reductions in daily starch intake. Patients generally did not experience an increase in time spent in hypoglycemia. Triglyceride levels were generally comparable to baseline at the latest evaluable time point.
Based on the safety and clinical findings observed to date, Beam is advancing BEAM-301 into the 60 mg dose-escalation cohort, with enrollment currently underway. Beam also plans to engage with the U.S. Food and Drug Administration (FDA) regarding a potential path to approval.