BioMarin Pharmaceutical (Nasdaq: BMRN) reported that its Phase III ENERGY 3 trial evaluating BMN 401 in children aged 1 to 12 with ENPP1 deficiency met only one of two co-primary endpoints, raising questions about the program's regulatory path despite a clear pharmacological signal. BMN 401 (formerly INZ-701) is a potential first-in-class, subcutaneous enzyme replacement therapy for the treatment of ENPP1 deficiency which entered BioMarin's pipeline via the June 2025 acquisition of Inozyme Pharma, Inc.
The ENERGY 3 study is a Phase III multicenter, randomized (2:1), controlled, open-label trial that enrolled 27 pediatric participants with ENPP1 deficiency, with enrollment completed in January 2025.
BMN 401 produced statistically significant increases in plasma inorganic pyrophosphate (PPi) through week 52 compared to the conventional therapy control arm, satisfying the first co-primary endpoint. However, the trial failed to demonstrate any corresponding improvement in Radiographic Global Impression of Change (RGI-C) scores at week 52 — the second co-primary endpoint, added following discussions with health authorities specifically to capture clinically meaningful changes in rickets severity. No positive trends were observed across secondary endpoints, including Rickets Severity Score (RSS) and growth Z-score for height, body length, and weight. BMN 401 was generally well-tolerated, with no new safety signals reported. Specific numerical values were not disclosed; detailed results are to be presented at an upcoming medical meeting.
The disconnect between biomarker and clinical outcomes
The ENERGY 3 trial results expose a problem that has recurred across rare disease development: a pharmacodynamic signal that does not translate into measurable clinical benefit. BMN 401 is a subcutaneous enzyme replacement therapy designed to restore deficient ENPP1 enzymatic activity. ENPP1 encodes an ectonucleotidase that hydrolyzes extracellular ATP to generate pyrophosphate, a key regulator of mineralization. In ENPP1 deficiency, reduced PPi levels drive pathological calcification of blood vessels and soft tissues in infancy, and a form of rickets — autosomal-recessive hypophosphatemic rickets type 2 (ARHR2) — in childhood.
The rationale for targeting PPi restoration is mechanistically coherent: correcting the upstream enzymatic deficit should, in principle, normalize the downstream mineralization dysregulation that causes rickets. The ENERGY 3 data confirm that BMN 401 does raise PPi levels to a statistically significant degree. What the data do not show is that this biochemical correction translates into radiographic improvement in bone disease over 52 weeks in this age group.
The ENPP1 deficiency rare genetic disorder therapy landscape is narrow. No therapy is currently approved specifically for ENPP1 deficiency. The condition's most severe presentation — generalized arterial calcification of infancy (GACI) Type 1 — carries a mortality rate of approximately 50% within the first six months of life, underscoring the clinical urgency that BioMarin's chief research and development officer Greg Friberg cited in the company's statement.