D8-MMAF hydrochloride is a deuterated form of MMAF hydrochloride, which is a microtubule destroyer.

MMAF showed cytotoxicity in vitro against a group of cell lines. Karpas 299, H3396, 786-O and Caki-1 have IC50 values of 119, 105, 257 and 200 nM, respectively. Targeted MMAF is more effective than free drug, and the cAC10 conjugate of MMAF shows significant activity. On a molar basis, cAC10-L1-MMAF4 is on average more than 2200 times more potent than free MMAF and is active in all CD30-positive cell lines tested.

The maximum tolerated dose of MMAF (> 16 mg / kg) mice is much higher than that of MMAE (1 mg / kg). The MTD of cAC10-L1-MMAF4 is 50 mg / kg in mice and 15 mg / kg in rats. The corresponding cAC10-L4-MMAF4 ADC is much less toxic, with MTDs greater than 150 mg / kg and 90 mg / kg in mice and rats, respectively.