An Innovative Site-Specific Anti-HER2 Antibody-Drug Conjugate with High Homogeneity and Improved Therapeutic Index

Purpose: Antibody-drug conjugates (ADCs) have emerged as a potent Cancer therapeutic option in recent years. DP303c is a HER2-targeting ADC with a cleavable linker-MMAE payload. The current study aimed to evaluate the therapeutic potentials of DP303c in vitro as well as in vivo.

Materials and methods: Size exclusion chromatography (SEC), reverse-phase high-performance liquid chromatography (RP-HPLC), and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to analyze the physicochemical characterization of DP303c. An enzyme-linked immunosorbent assay (ELISA), a cell-based assay, and bio-layer interferometry (BLI) were used to evaluate DP303c's affinity with HER2 and Fc Receptors. A confocal laser scanning microscopy was used to observe the internalization of DP303c. Antibody-dependent cell-mediated cytotoxicity (ADCC) and cytotoxicity assays were used to investigate the activity of DP303c in vitro. The antitumor activity of DP303c was assessed in vivo in the HER2-positive cell-derived xenograft model.

Results: DP303c was a site-specific anti-HER2 antibody-drug conjugate with a monomethyl Auristatin E (MMAE) with an average drug-to-antibody ratio (DAR) of 2.0. DP303c showed a high affinity with HER2 and could be effectively internalized. In vitro and in vivo, DP303c showed stronger antitumor activity as compared to trastuzumab-DM1 (T-DM1) in a series of HER2-positive Cancer cells and cell-derived xenograft (CDX) models, especially in the lower HER2-expressing cells. DP303c also exhibited high serum stability and a good PK profile.

Conclusion: DP303c was a steady and homogenous DAR 2 ADC that was predicted to deliver MMAE inhibitor to tumor cells. DP303c demonstrated remarkable Anticancer efficacy against T-DM1 in xenograft models. DP303c was a strong candidate for the treatment of patients with HER2-positive Cancer.

ADCs; antibody-drug conjugates; engineered microbial transglutaminase; monomethyl auristatin E; site-specific conjugation.