China's National Medical Products Administration (NMPA) has cleared CStone Pharmaceuticals (HKEX: 2616) to begin clinical trials of CS5007, an EGFR/HER3 bispecific antibody-drug conjugate (ADC), in patients with advanced solid tumors. The investigational new drug (IND) application was processed in 23 working days under China's innovative drug clinical trial pathway, allowing CStone to expand its global Phase I program into China after enrolling the first patient in Australia in June 2026.
CS5007 was developed using CStone's proprietary ADC platform and combines CS2011, an EGFR/HER3-targeting human IgG1 bispecific antibody, with the company's hydrophilic CSL20 linker and the topoisomerase I inhibitor exatecan as its cytotoxic payload. The dual-targeting design is intended to increase activity across tumors with heterogeneous EGFR and HER3 expression and potentially address HER3-mediated resistance to EGFR-directed therapy.
The global Phase I first-in-human study is evaluating CS5007 monotherapy in patients with advanced solid tumors that have progressed following, or are ineligible for, standard treatment. The dose-escalation and expansion study will assess safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity, while establishing a recommended Phase II dose. Approximately 310 patients are expected to enroll across Australia and China.
CS5007 enters a field in which an EGFR/HER3 bispecific ADC has already reached the market. Izalontamab brengitecan (iza-bren), developed by SystImmune and licensed to Bristol Myers Squibb, received NMPA approval for nasopharyngeal carcinoma and has since expanded into esophageal cancer, while also reporting positive Phase III results in triple-negative breast cancer. Like CS5007, iza-bren combines an EGFR/HER3 bispecific antibody with an exatecan-based topoisomerase I inhibitor payload, making it a close structural and mechanistic comparator.