Beam Therapeutics Receives FDA Clearance for BEAM-304, a First-in-Class In Vivo Base Editing Therapy for Phenylketonuria
Key Insights
Beam Therapeutics announced FDA clearance of its IND application for BEAM-304 (search), an in vivo base-editing therapy targeting the PAH gene mutations that cause phenylketonuria (search) (PKU).
BEAM-304 (search) uses lipid nanoparticle delivery and is designed as a platform-based approach to develop multiple mutation-specific base editors within a single clinical program.
The planned Phase 1/2 trial will initially evaluate safety, tolerability, and Phe reduction in PKU patients with the R408W mutation, followed by a second mutation-specific editor.
Beam Therapeutics Inc. (Nasdaq: BEAM) announced on June 18, 2026 that the U.S. Food and Drug Administration has cleared its Investigational New Drug (IND) application for BEAM-304 (search), an in vivo base-editing therapy designed to correct mutations in the phenylalanine hydroxylase (search) (PAH) gene that cause phenylketonuria (search) (PKU). The clearance positions the Cambridge, Massachusetts-based biotechnology company to initiate a Phase 1/2 clinical trial, marking a significant step toward what could become the first curative treatment for this rare inherited metabolic disorder.
"PKU affects approximately 20,000 people in the U.S., with significant unmet need for therapies that address the underlying cause of disease," said Giuseppe Ciaramella, Ph.D., president of Beam. "FDA clearance of our IND for BEAM-304 (search) supports our novel approach of developing multiple mutation-specific base editors through a single clinical platform program, leveraging emerging FDA guidance intended to accelerate development of base editing therapeutics."
A Platform Approach to Genetic Correction
BEAM-304 (search) leverages Beam's proprietary base editing technology, which enables precise, predictable single-base changes at targeted genomic sequences without making double-stranded breaks in DNA. The therapy employs a liver-targeting lipid nanoparticle (LNP) formulation to deliver base editing reagents directly to hepatocytes, where the PAH enzyme is normally produced.
The development strategy reflects an innovative platform-based approach aligned with the FDA's recent draft guidance aimed at accelerating cell and gene therapy development. Rather than pursuing separate clinical programs for each disease-causing mutation, Beam is developing multiple mutation-specific base editors efficiently within a single clinical program using the same underlying base editing technology, LNP delivery system, and manufacturing approach.
"Many PKU-causing mutations are single-base changes, making the disease particularly well suited for correction through base editing," said Gopi Shanker, Ph.D., chief scientific officer of Beam. "By leveraging the same underlying base editing technology, LNP delivery system, and manufacturing approach across multiple mutation-specific editors, we believe we can establish a scalable development pathway that expands access to potentially transformative therapies for people living with PKU and may serve as a model for addressing other genetically diverse liver diseases in the future."
Preclinical Evidence and Trial Design
Preclinical data demonstrated that BEAM-304 (search) normalized plasma phenylalanine (Phe) levels in PKU mouse models at clinically relevant doses, with robust on-target editing observed in the liver. Updated preclinical data will be presented at the Federation of American Societies for Experimental Biology (FASEB) Genome Engineering: Research and Applications Conference, taking place July 6-9, 2026, in Porto, Portugal.
The planned Phase 1/2 trial is an open-label, dose exploration and dose expansion study that will investigate safety, tolerability, pharmacodynamics, pharmacokinetics, and efficacy in PKU patients. Initial clinical development will focus on base editors addressing the two most prevalent variants found in nearly half of patients with PKU in the U.S., beginning with the R408W mutation. A second base editor targeting another prevalent mutation will follow, with the goal of establishing clinical proof of concept for base editing in PKU. BEAM-304 (search) is administered via intravenous infusion.
Addressing a Persistent Unmet Need
PKU is caused by pathogenic variants in the PAH gene that result in the inability to properly metabolize phenylalanine, an essential amino acid. Elevated blood Phe levels can lead to serious and irreversible brain damage and neurological complications, including cognitive impairment, developmental delays, and psychiatric symptoms, if not adequately controlled. The condition is typically diagnosed in infancy through newborn screening.
There are currently no approved curative treatments for PKU. Current management options require lifelong dietary restriction and chronic disease management, and many patients continue to experience significant unmet medical need. By correcting mutations in the PAH gene, BEAM-304 (search) aims to restore PAH enzyme activity, reduce toxic Phe to recommended guideline levels of ≤360 µmol/L, and enable diet normalization and freedom from medical food.
Beam's expanding clinical-stage pipeline now includes this PKU program alongside other gene-editing candidates targeting various hematologic and metabolic conditions. Following the announcement, Beam Therapeutics shares traded at $24.15.