ESG401 TROP2-Directed ADC Hits 83% ORR First-Line TNBC, ~35% in Heavily Pretreated Breast Cancers

ESG401, an ADC consisting of humanized anti-TROP2 IgG1 conjugated to SN-38. ESG401 was evaluated in the phase 1 ESG401-101 study in China (NCT04892342) across 156 patients with metastatic breast and other solid tumors. Late-line HR+/HER2- Breast Cancer (n = 58) showed ORR 34.5%, DCR 77.6%, mPFS 7.4 mo, mDOR 6.6 mo. Late-line Triple Negative Breast Cancer (TNBC) (n = 47) logged ORR 35.1%, mPFS 3.7 mo. First-line TNBC (n = 35) achieved ORR 83% with mPFS not yet reached. Grade ≥3 neutropenia and leukopenia were the main TRAEs; only 2.6% discontinued for toxicity (dose delays 39%, reductions 7%). Compared with sacituzumab govitecan’s 35% ORR and 5.6 mo PFS in late-line TNBC and datopotamab DXd’s ~27% ORR in advanced HR+/HER2- Breast Cancer, ESG401 looks competitively active, especially the striking first-line TNBC responses.