VX-680 (Tozasertib, MK-0457) VX-680 (Tozasertib, MK-0457) Synonyms: N-[4-[[4-(4-Methyl-1-piperazinyl)-6-[(5-methyl-1H-pyrazol-3-yl)amino]-2-pyrimidinyl]thio]phenyl]cyclopropanecarboxamide; MK 0457; VX 680 CAS NO.: 639089-54-6 Formula: C23H28N8Os Weight: 464.59