BioMarin Drops Preclinical PKU Drug Once Seen as Potential Palynziq Successor

BioMarin Pharmaceutical has discontinued the development of its preclinical PKU drug BMN 390, which was previously considered a potential successor to its approved therapy Palynziq1.

BMN 390 was planned to enter human trials in 2025, with hopes of improving upon the efficacy and safety (notably immunogenicity) profile of Palynziq1.

The decision to end the BMN 390 program was based on the drug not meeting its target immunogenicity threshold for further advancement, as noted in BioMarin's second-quarter 2025 earnings release1.

Employees working on BMN 390 have been redeployed within BioMarin, and the company states it remains committed to developing new PKU therapies1.

Palynziq, approved for adults with PKU in the U.S. since 2018, generated $106 million in second-quarter 2025 sales—a 20% year-over-year increase1.

Sources:

1. https://www.fiercebiotech.com/biotech/biomarin-drops-preclinical-pku-drug-once-seen-potential-palynziq-successor