Fortress Biotech, Inc. (FBIO) and its majority‑owned subsidiary Cyprium Therapeutics announced that the U.S. Food and Drug Administration approved ZYCUBO, a copper histidinate injectable, for the treatment of Menkes disease on January 13 2026. ZYCUBO is the first and only FDA‑approved therapy for this X‑linked, fatal pediatric disorder, which affects roughly one in 35,000 male births in the United States.
The approval was backed by a pivotal clinical program that showed an almost 80 % reduction in mortality risk for patients who received early treatment compared with an untreated external control cohort. Median overall survival was 177.1 months for the early‑treatment cohort versus 17.6 months for the control group, underscoring the life‑saving potential of the drug and the urgency of early intervention.
ZYCUBO received Breakthrough Therapy, Fast Track, Rare Pediatric Disease, and Orphan Drug Designations, and Fortress secured a Rare Pediatric Disease Priority Review Voucher that will be transferred to Cyprium. In December 2023, Sentynl Therapeutics, a subsidiary of Zydus Lifesciences, assumed full responsibility for the development and commercialization of ZYCUBO. The partnership unlocks up to $129 million in aggregate development and sales milestones for Cyprium, while the voucher could be sold for a comparable amount, adding significant upside to Fortress’s portfolio.
Fortress’s approval adds a high‑margin orphan‑drug asset to a business model that has struggled with profitability. The company’s revenue has declined 39.7 % over three years and its operating margin is negative, yet the ZYCUBO milestone potential and the voucher value provide a new revenue stream that could offset ongoing cash‑flow pressures. Management views the approval as a strategic win that validates its incubation strategy and opens a new rare‑disease pipeline.
Chief Executive Officer Lindsay A. Rosenwald said, “The approval of ZYCUBO is a pivotal milestone for our company and patients suffering from Menkes Disease. It confirms the effectiveness of our platform and positions Fortress to capture a critical unmet need.” He added that the company’s recent trio of FDA approvals in 15 months demonstrates a growing track record of regulatory success.
Market reaction to the announcement was mixed. While pre‑market activity reflected enthusiasm for the first treatment of a fatal rare disease, the stock later fell as investors weighed Fortress’s weak cash flow, ongoing operating losses, and the fact that commercialization is handled by Sentynl rather than Fortress itself. Heavy trading volume and a near two‑week low indicated that the positive news was tempered by broader financial concerns.
The approval positions Fortress to tap into a niche but potentially lucrative market. Menkes disease, though rare, carries a high unmet need and a limited patient population, which can command premium pricing. However, the company must navigate the challenges of scaling a rare‑disease product, securing reimbursement, and managing the partnership with Sentynl. The milestone upside and voucher value provide a compelling upside, but the financial headwinds and reliance on a third‑party commercial partner underscore the need for disciplined cash‑flow management and continued regulatory success.
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