Characterisation of mAb104 Antibody-Drug Conjugates Targeting a Tumour-Selective HER2 Epitope

The novel anti-HER2 antibody 104 (mAb104) targets a unique tumour-specific epitope, lacks normal tissue binding and can internalise into tumour cells, thus supporting its development into antibody drug conjugates (ADCs).

We now describe the binding properties and preclinical activity of mAb104-ADCs developed through the conjugation of mAb104 via linkers to the anti-microtubule drug maytansoinoid ematansine (DM1-SMCC; DM1), topoisomerase I inhibitor, exatecan derivative (MC-GGFG-DX8951; DX8951) or microtubule disruptor monomethyl auristatin E (MC-vc-PAB-MMAE; MMAE).

Mab104-ADCs demonstrate dose-dependent cytotoxicity in vitro. The safety of single-dose mAb104-DX8951 was demonstrated in vivo at doses up to 10 mg/kg. MAb104-ADCs also demonstrated potent and prolonged anti-tumour activity in a range of tumour types with variable HER2 expression. Mab104-DX8951 showed significant responses in trastuzumab-resistant HER2-positive breast cancer, low HER2-expressing cancers, as well as HER2-overexpressing cancers.

These findings indicate the potential for tumour-specific targeting of HER2-expressing tumours with mAb104-ADCs.