Fortress Biotech Inc (NASDAQ:FBIO) saw its stock collapse 33.7% on Wednesday after the company announced that the U.S. Food and Drug Administration (FDA) issued a Complete Response Letter (CRL) for its Menkes disease therapy.
The FDA declined the New Drug Application for CUTX-101 (copper histidinate), citing deficiencies in current Good Manufacturing Practice (cGMP) at the production facility. The regulatory setback affects the pediatric treatment for Menkes disease, a rare genetic disorder.
Fortress Biotech emphasized that the CRL did not raise any concerns regarding the drug’s efficacy or safety. The manufacturing site has already responded to the FDA following a re-inspection in September 2025. Sentynl Therapeutics, which took over development of CUTX-101 in December 2023, intends to request a meeting with the FDA to discuss resubmission.
CUTX-101 had previously been granted Priority Review status. Clinical studies had shown notable improvements in overall survival among Menkes disease patients receiving early treatment with the drug.
Under the agreement with Sentynl, Cyprium Therapeutics, a majority-owned Fortress subsidiary, remains eligible for a Rare Pediatric Disease Priority Review Voucher if the therapy gains approval. Additionally, Cyprium could earn royalties on net sales and up to $129 million in development and sales milestones.
Menkes disease is a rare genetic condition affecting copper metabolism, often leading to severe neurological symptoms and early mortality in affected children.
This content is for informational purposes only and does not constitute financial, investment, or other professional advice. It should not be considered a recommendation to buy or sell any securities or financial instruments. All investments involve risk, including the potential loss of principal. Past performance is not indicative of future results. You should conduct your own research and consult with a qualified financial advisor before making any investment decisions.