BioMarin Halts Development of Pre-Clinical PKU Drug Amid Competitive Pressures

BioMarin Discontinues BMN 390 Program

BioMarin Pharmaceutical has announced the discontinuation of its pre-clinical candidate BMN 390, which was being developed for the treatment of phenylketonuria (PKU). The decision comes as a result of the drug failing to meet the company's target immunogenicity threshold for advancement. This development marks a setback in BioMarin's efforts to expand its PKU portfolio and potentially replace its current therapy, Palynziq.

The company stated in its second-quarter earnings release that employees working on the BMN 390 program have been redeployed to other roles within the organization. BioMarin had initially planned to file an Investigational New Drug application for BMN 390 in the latter half of this year, positioning it as a potential successor to Palynziq with improved safety and efficacy profiles.

Competitive Landscape Shifts in PKU Treatment

The termination of the BMN 390 program comes at a critical time for BioMarin, as the PKU treatment landscape faces significant changes. PTC Therapeutics recently received FDA approval for Sephience, a new PKU therapy indicated for both adults and children. Sephience's broad label, which includes treatment for patients as young as one month old, poses a direct challenge to BioMarin's existing PKU franchise.

Truist analysts have expressed concern about the future of BioMarin's PKU business, noting that the termination of BMN 390 and the imminent launch of Sephience in the U.S. could put pressure on Palynziq's market position. Phase III data for Sephience demonstrated a 63% reduction in phenylalanine levels in treated patients, highlighting its potential efficacy in managing PKU.

BioMarin's Q2 Financial Performance

Despite the setback in its PKU pipeline, BioMarin reported strong financial results for the second quarter of 2025. The company recorded revenues of $825 million, representing a 17% year-on-year growth and surpassing the consensus estimate of $760 million. This performance was driven by robust sales across BioMarin's enzyme product portfolio.

Notably, Voxzogo, BioMarin's therapy for achondroplasia, saw a 20% year-on-year increase, generating $221 million in Q2. Vimizim, indicated for mucopolysaccharidosis type IVA, also contributed significantly to the topline beat with a 21% year-on-year growth, bringing in $215 million in sales. Palynziq, despite facing potential future challenges, made $106 million in the quarter, marking a 20% increase from the same period last year.