The U.S. Food and Drug Administration approved Zycubo (copper histidinate, CUTX‑101) as the first approved treatment for Menkes disease, a rare pediatric disorder of copper absorption. Sentynl Therapeutics, which acquired development and commercialization rights, secured approval two days before a PDUFA deadline after resolving prior manufacturing issues. The approval earned a rare pediatric disease priority review voucher (PRV) for the NDA sponsor; under prior agreements the PRV will transfer to Cyprium with potential milestone and royalty arrangements. The decision follows clinical data supporting safety and effect on systemic copper levels in affected infants. This regulatory win creates an immediate commercial pathway for a fatal, previously untreated condition and highlights the ongoing role of small specialty developers in rare‑disease approvals.