DP303c + simmitinib

**DP303c + simmitinib** is a combination regimen investigated in clinical trials for the treatment of HER2-positive gastric adenocarcinoma or gastroesophageal junction adenocarcinoma that has progressed after at least one line of systemic therapy. **DP303c** is an antibody-drug conjugate (ADC) consisting of an anti-HER2 monoclonal antibody linked to the cytotoxic payload monomethyl auristatin E (MMAE), employing an enzyme-specific cleavable linker. DP303c inhibits HER2 signaling, induces antibody-dependent cellular cytotoxicity (ADCC), and delivers the microtubule-disrupting MMAE to HER2-expressing tumor cells. **Simmitinib** is a small molecule tyrosine kinase inhibitor; while its precise kinase target profile is not explicitly stated in trial documentation, it suggests activity relevant to synergize with HER2-targeted therapy. The combination is being studied for its safety and antitumor efficacy in patients resistant to previous systemic chemotherapy, including platinum- and fluorouracil-based regimens.