BioMarin Spent $270M on a Drug That Works in the Blood but Not in the Bones

For European regulators, the situation is even clearer. RGI-C was a co-primary endpoint, meaning the trial needed to hit both targets. It only hit one. That's a miss.

Stifel analysts called it bluntly: the result "removes an upside driver" and creates "significant risk to approval." Leerink echoed caution on the regulatory path forward.

The $270M Question

BioMarin paid $4.00 per share for Inozyme, a roughly 180% premium over the stock's $1.42 closing price before the deal was announced. The transaction was all cash, no milestones, no earn-outs, no contingent payments. BioMarin bet the full $270 million up front.

That bet made strategic sense at the time. BioMarin positions itself as the rare-disease company: genetically defined conditions, small patient populations, premium pricing, orphan drug exclusivity. ENPP1 deficiency (estimated prevalence: about 1 in 64,000 pregnancies worldwide) fit perfectly into that playbook.

But the ultra-rare strategy comes with ultra-rare risk. When your pivotal trial enrolls dozens of patients instead of thousands, statistical noise is amplified. A rare-disease development review found that 81% of screened rare-disease patients weren't even eligible for enrollment, compared to 57% in non-rare diseases. Everything is harder: finding patients, keeping them enrolled, measuring outcomes that regulators will accept.

A Glimmer Buried in the Data

There's one interesting wrinkle. Separate data from infants and very young children with ENPP1 deficiency told a different story. In that group, 80% survived beyond the first year (versus about 50% historically), arterial calcifications stabilized or improved, and none of the at-risk infants showed rickets after age 1.

The implication is uncomfortable but logical: maybe the drug works if you give it early enough, before skeletal damage is established. Reversing bone disease in older children might be a fundamentally harder problem than preventing it in infants. That's a scientific insight, but it doesn't save the Phase 3 program BioMarin just bought.

BioMarin's Bigger Picture

This isn't the only iron in BioMarin's fire. The company has Voxzogo (for achondroplasia) expanding into hypochondroplasia with Phase 3 data expected soon. Palynziq has an adolescent label expansion with a February 2026 PDUFA date. And its $4.8 billion Amicus acquisition adds two commercial rare-disease drugs.

But the Inozyme stumble stings for two reasons. First, it's a $270 million write-down risk with no milestone structure to soften the blow. Second, analysts have trimmed long-term revenue growth assumptions from 3.95% down to 2.46%.

BioMarin's M&A history doesn't inspire confidence here either. Its 2009 deal with La Jolla (lupus drug Riquent) failed. Its Prosensa acquisition for drisapersen in Duchenne muscular dystrophy also never reached the market. The Inozyme bet was supposed to represent a new, more disciplined era of deal-making.

The Uncomfortable Lesson

Rare-disease acquisitions look elegant on a slide deck. Small populations, huge unmet need, premium pricing, regulatory fast-tracks. But when your entire investment thesis rests on one pivotal trial with a few dozen patients, you're playing a game where one data readout can erase hundreds of millions in value overnight.

BioMarin learned that lesson when the ENERGY-3 results came in. The question now is whether the infant data offers a path forward, or whether BMN 401 joins the long list of drugs that corrected the right biomarker but couldn't fix the actual disease.

A Lesson About Antibodies and Eyeballs

Immunovant's FcRn inhibitor failed two Phase 3 trials in thyroid eye disease, costing $39 million to shut down. The failure isn't just one company's problem; it's exposing the limits of an entire drug class that Wall Street thought could conquer all of autoimmunity.