Historic FDA Green Light: Why ZYCUBO's Approval Marks a Turning Point for Menkes Disease Patients

For decades, families facing a Menkes disease diagnosis confronted an impossible reality—a rare genetic disorder that devastates infant neurological development with virtually no medical recourse. That landscape shifted dramatically with the FDA’s clearance of ZYCUBO, marking the agency’s first-ever approval of a therapeutic option specifically designed to address this X-linked copper transport disorder.

The Clinical Evidence That Changed the Game

The approval wasn’t handed out lightly. Clinical trial data revealed a striking 80% reduction in mortality risk among patients receiving early ZYCUBO intervention compared to historical untreated cases. The survival gap tells the real story: patients treated with this copper histidinate formulation achieved a median lifespan of 177.1 months, fundamentally reshaping outcomes in a condition where the untreated median survival clocked in at just 17.6 months. That’s not just statistical improvement—it’s a transformation in what’s possible for Menkes disease management.

Understanding the Science Behind the Breakthrough

Menkes disease stems from mutations in the ATP7A gene, crippling the body’s ability to properly absorb and transport copper. The cascade of damage is severe: neurological deterioration, connective tissue breakdown, and historically, death before age three in most cases. ZYCUBO, a subcutaneous copper histidinate injection, essentially restores the copper balance the body cannot achieve on its own, effectively rewiring the treatment paradigm.

A Milestone Layered with Multiple Wins

Fortress Biotech and its subsidiary Cyprium Therapeutics didn’t just secure a single approval—the regulatory path delivered stacked advantages. ZYCUBO earned Breakthrough Therapy, Fast Track, Rare Pediatric Disease, and Orphan Drug designations. The FDA also transferred a Rare Pediatric Disease Priority Review Voucher to Cyprium, sweetening the deal. Additionally, Cyprium stands to pocket tiered royalties and up to $129 million in development and sales milestones from Sentynl Therapeutics, the company that took over development and commercialization responsibilities in 2023.

Momentum Building Across Fortress’s Portfolio

This ZYCUBO clearance represents the third FDA approval for Fortress Biotech within a 15-month window, following recent greenights for Emrosi (inflammatory rosacea lesions) and UNLOXCYT (advanced cutaneous squamous cell carcinoma). The company’s portfolio-building strategy is visibly paying dividends in the regulatory arena.