Peptide–drug conjugates bearing an antimitotic Ahx-DA1 payload achieve potent antitumor activity in Her2-amplified and EGFR-positive KRAS-mutant cancers in vivo

Peptide–drug conjugates (PDCs) represent a targeted cancer therapy strategy that combines tumor-homing peptides with potent cytotoxic payloads, offering a promising alternative to antibody–drug conjugates (ADCs) through improved tissue penetration, synthetic accessibility, and tumor selectivity. Auristatins (MMAE, MMAF, etc.), which are synthetic analogues of antimitotic dolastatin 10 (Dol-10), are widely used as ADC payloads; however, their systematic evaluation in PDC formats remains limited. In this study, we investigated Ahx-DA1, an enzymatically stable derivative of microtubule inhibitor DA1, a previously reported dolastatin-10 analogue, as a payload for PDCs. Two receptor-specific peptides, HER2-targeting peptide A9 and EGFR-binding peptide P6, were conjugated to a Ahx-DA1 and evaluated in the HER2-overexpressing breast cancer BT-474 model and the EGFR-overexpressing KRAS-mutated colorectal (HCT116) and pancreatic (PANC1) models, respectively. A cell-based study of DA1-bearing PDCs revealed specific and potent cytotoxicity in cancer cell lines, with the corresponding overexpressed receptors demonstrating high target specificity. The DA1-based PDCs exhibited high stability and favorable tolerability profiles across all the tested xenograft models. In vivo studies demonstrated pronounced tumor growth inhibition by A9-DA1 in HER2+ xenograft and P6-DA1 in EGFR+ KRAS mutated colorectal and pancreatic xenograft models. Overall, our findings suggest that Ahx-DA1 is a highly effective auristatin-class payload for the development of DA1 based anticancer PDCs.