Emiltatug ledadotin (Emi-Le)

Emiltatug ledadotin (Emi-Le, XMT-1660) is investigational and has no marketing approval in any jurisdiction. It is being studied in NCT05377996, a phase 1/2 first-in-human trial with dose escalation, dose expansion, and a phase 2 part (EMBLEM-1) in aggressive adenoid cystic carcinoma (ACC); the registry record was last updated in June 2026 with status recruiting, an estimated enrollment of 360 participants, and an estimated primary completion date of February 2027. The FDA granted Breakthrough Therapy designation on or before 12 May 2026 for locally advanced, recurrent or metastatic ACC with solid histology or high-grade transformation. Earlier FDA Fast Track designations cover advanced or metastatic triple-negative breast cancer and HER2-low or HER2-negative breast cancer after a topoisomerase-1 inhibitor ADC. EMBLEM-1 is testing 80 mg/m2 every 4 weeks (capped at 160 mg) with objective response rate as the primary endpoint, and the sponsor described it as a “pivotal Phase 2 study”. In its February 2026 annual report, Day One stated that it “may seek” orphan drug designation for Emi-Le; no orphan drug designation, biologics license application, or regulatory submission outside the United States was identified. Under the acquisition agreement, contingent payments are tied to first dosing in a registrational ACC-1 trial by 31 December 2027 and FDA approval in ACC-1 by 31 December 2030.