FDA Rejects Disc Medicine's Bitopertin for Rare Blood Disorder EPP Despite Commissioner's Priority Voucher

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The FDA issued a Complete Response Letter (CRL) on February 13, 2026, rejecting Disc Medicine's bitopertin for erythropoietic protoporphyria (EPP), a rare blood disorder causing sunlight sensitivity.237

Despite granting bitopertin a Commissioner's National Priority Voucher (CNPV) in October 2025 for expedited review, the FDA cited uncertainties in whether reductions in protoporphyrin IX (PPIX) levels predict clinical benefits like improved sun tolerance.1245

The FDA acknowledged the phase 2 trial met its primary surrogate endpoint but required a study with clinical endpoints, such as sun exposure outcomes.246

Disc Medicine plans to address concerns using data from the ongoing phase 3 APOLLO trial, expecting top-line results in Q4 2026, potentially leading to resubmission and approval by mid-2027.245

The rejection caused Disc's shares to drop 31% to $49, highlighting scrutiny of the opaque CNPV program and a pattern of recent FDA rejections in rare diseases.235

Sources:

1. https://www.biospace.com/fda/discs-regulatory-comeback-plan-for-rejected-drug-relies-on-old-fda-leadership

2. https://www.fiercebiotech.com/biotech/fda-rejects-discs-rare-disease-drug-despite-commissioners-voucher

3. https://www.statnews.com/2026/02/13/disc-medicine-fda-decision/

4. https://www.biospace.com/fda/fda-rejects-discs-rare-blood-disease-drug-amid-reports-of-prasads-skepticism

5. https://medcitynews.com/2026/02/disc-medicine-fda-rejection-bitopertin-blood-disorder-porphyria-rare-disease-cnpv-iron/

6. https://cen.acs.org/pharmaceuticals/rare-disease/FDA-rejects-drug-rare-blood/104/web/2026/02

7. https://ir.discmedicine.com/news-releases/news-release-details/disc-medicine-receives-complete-response-letter-fda-bitopertin