Mirum Pharmaceuticals, Inc. (MIRM) Posts Positive Pediatric FOP Cohort 2 Results

What happened

Mirum said ATEBRIOZ (zilurgisertib) reduced mean HO volume by 8.09 cm³ versus a 9.14 cm³ increase on placebo at Week 24 in children aged 6 to under 12 with FOP, with no new HO lesions on drug. A supplemental filing for this age group is planned in the first half of 2027.

Confirmed

Global impact / market context

Positive results in younger patients could support expanding the drug's approved age range, opening more patients to treatment and broadening future revenue. If regulators accept the filing and review favorably, the addressable market grows beyond the currently approved 12-and-older group.

Analyst inference

The readout extends earlier data behind the 12-and-older approval, so investors may treat it as evidence the drug works across ages. Because final revenue depends on regulatory review and a separate younger cohort still enrolling, the path to a bigger market remains conditional.

Analyst inference

What to watch

1. Mirum plans a supplemental new drug application for ages 6 to under 12 in the first half of 2027, which is the filing that would seek to extend the U.S. label. Confirmed
2. Cohort 3, covering ages 2 to under 12, is still enrolling; success there could widen the patient group eligible for treatment and extend the revenue opportunity. Confirmed
3. Watch the FDA's decision on the planned filing and the safety and efficacy results from Cohort 3, since either could change how widely the drug is prescribed and how much revenue it generates. Analyst inference

Evidence

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