Mirum Pharmaceuticals wins FDA approval for Atebrioz in FOP patients 12 and older
Mirum expects U.S. availability in October after a 63-patient study; its prespecified new-lesion incidence endpoint missed the conventional threshold.
Adrian Kessler
An October U.S. launch is now expected for Mirum Pharmaceuticals, Inc. NASDAQMIRM after the FDA approved Atebrioz on Friday for patients aged 12 and older with fibrodysplasia ossificans progressiva. Mirum estimates about 300 people in the United States have the rare bone disorder and plans to offer the drug through its patient support program.
The Sept. 25 joint release with Incyte Corporation NASDAQINCY sets the starting dose at 100 milligrams once daily. Incyte developed the drug and licensed worldwide development and commercialization rights to Mirum, while the FDA granted Incyte a rare pediatric disease priority review voucher with the approval.
Mirum is a Foster City, California, rare-disease drugmaker whose existing portfolio includes treatments for inherited liver and genetic conditions. Atebrioz is its first approved treatment for the progressive bone formation that defines FOP.
Mirum shares closed at US$89.70 on Nasdaq as of 4:00:01 p.m. EDT Friday, according to the NASDAQMIRM quote. Incyte shares closed at US$123.89 on Nasdaq as of 4:00:01 p.m. EDT Friday, according to the NASDAQINCY quote. The FDA published its Sept. 25 approval notice before both closes; the companies' joint release followed at 7 p.m. EDT.
FDA Based Approval on Lesion Volume
The FDA's Sept. 25 notice says a randomized, double-blind study assigned 63 patients to Atebrioz or placebo for 24 weeks. Whole-body CT scans showed mean total new bone-lesion volume fell by 3.2 cubic centimetres in the treated group while rising by 24.6 cubic centimetres on placebo. The approved indication is reduction of that volume in patients aged 12 and older.
The June 14 company readout identified a different prespecified primary endpoint: the share of patients with new lesions by Week 24. One of 32 treated patients developed a new lesion, against five of 31 on placebo, with a p value of 0.0986. That missed the conventional 0.05 threshold; the readout separately reported a nominal p value of 0.004 for change in total lesion volume.
The FDA warns that Atebrioz can cause fetal harm and advises contraception and immediate discontinuation if pregnancy occurs. Headache, joint pain, upper respiratory infection, nosebleeds and nausea were the most common adverse reactions. Mirum said no adverse event caused a patient to stop or reduce treatment during the blinded study period.
"Having another treatment option is meaningful in a progressive disease like FOP, particularly for adolescents who may be earlier in the course of their disease," PROGRESS lead investigator Robert Pignolo said in the Sept. 25 release.
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A Third U.S. FOP Treatment Enters the Market
The FDA called Atebrioz the third treatment approved for FOP on Sept. 25. Ipsen S.A. EPAIPN OTCMKTSIPSEY won U.S. approval for Sohonos in August 2023, with a label covering girls from age eight and boys from age ten. The age ranges overlap, but the companies' studies do not establish a head-to-head efficacy comparison.
Mirum's Sept. 25 release says eligible patients may pay as little as US$0 a month through its access program, which helps with insurance coverage and financial assistance. That copay offer is distinct from a list price, which the release did not disclose. An EU marketing application remains under review, and Mirum has completed enrollment in one younger pediatric cohort while recruiting another.
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Mirum expects Atebrioz to become available in the United States in October, when patients aged 12 and older would gain another treatment option.
