Tissue factor (TF) is aberrantly expressed in solid
cancers and is thought to contribute to
disease progression through its procoagulant activity and its capacity to induce intracellular signaling in complex with
factor VIIa (FVIIa). To explore the possibility of using
tissue factor as a target for an
antibody-drug conjugate (ADC), a panel of human
tissue factor-specific
antibodies (TF HuMab) was generated. Three
tissue factor HuMab, that induced efficient inhibition of TF:FVIIa-dependent intracellular signaling, antibody-dependent cell-mediated cytotoxicity, and rapid target internalization, but had minimal impact on
tissue factor procoagulant activity in vitro, were conjugated with the
cytotoxic agents monomethyl auristatin E (MMAE) or
monomethyl auristatin F (MMAF).
Tissue factor-specific ADCs showed potent cytotoxicity in vitro and in vivo, which was dependent on
tissue factor expression. TF-011-MMAE (HuMax-TF-ADC) was the most potent ADC, and the dominant mechanism of action in vivo was
auristatin-mediated
tumor cell killing. Importantly, TF-011-MMAE showed excellent antitumor activity in patient-derived xenograft (PDX) models with variable levels of
tissue factor expression, derived from seven different solid
cancers. Complete
tumor regression was observed in all PDX models, including models that showed
tissue factor expression in only 25% to 50% of the
tumor cells. In conclusion, TF-011-MMAE is a promising novel
antitumor agent with potent activity in xenograft models that represent the heterogeneity of human
tumors, including heterogeneous target expression.