China approves CSPC’s HER2 BsAb Ennituo for gastric cancer post-Herceptin

China’s National Medical Products Administration has granted marketing authorization to Ennituo (anbenitamab; SYS6092; KN026 ), a recombinant humanised bispecific antibody co-developed by Shanghai JMT-BIO Technology — a subsidiary of CSPC Pharmaceutical Group and Jiangsu Alphamab Biopharmaceuticals, for the treatment of adults with locally advanced or metastatic HER2-positive gastric or gastroesophageal junction (GEJ) adenocarcinoma who have previously received trastuzumab-containing therapy.

The approval marks anbenitamab’s first cleared indication approval globally, and positions CSPC in a competitive second-line gastric cancer space increasingly defined by HER2-directed precision strategies.

Ennituo is approved for use in combination with chemotherapy in this trastuzumab-pretreated population. Anbenitamab is an IgG1-type bispecific antibody that simultaneously engages two distinct, non-overlapping epitopes on HER2, a design intended to achieve more complete receptor blockade and enhanced internalization compared with conventional monospecific anti-HER2 agents. The molecule was originally developed by Alphamab Oncology using its proprietary CRIB heterodimer bispecific platform, with CSPC’s JMT-BIO subsidiary acquiring exclusive development and commercialisation rights for mainland China through a licensing agreement in August 2021.

The approval rests primarily on data from KC-WISE, a pivotal Phase II/III trial enrolling patients with HER2-positive gastric or GEJ adenocarcinoma who had failed at least one prior line of therapy. Against standard chemotherapy alone, anbenitamab plus chemotherapy produced a progression-free survival of 7.1 months versus 2.7 months — a hazard ratio of 0.25, corresponding to a 75% reduction in the risk of disease progression or death. Overall survival reached 19.6 months in the combination arm compared with 11.5 months in the control arm (HR 0.25), a 71% reduction in mortality risk. Improvements in objective response rate and duration of response were also reported, with a safety profile described as favourable.

The magnitude of the survival benefit observed in KC-WISE is notable in a disease setting where second-line options have historically offered modest gains. Anbenitamab’s dual-epitope engagement of HER2 is designed to prevent receptor re-expression and signalling through mechanisms that single-domain antibodies may not fully suppress, providing a mechanistic rationale for activity in patients who have already progressed on trastuzumab-based regimens.

The most direct comparator in this space is fam-trastuzumab deruxtecan (Enhertu, T-DXd), the HER2-directed antibody-drug conjugate developed by Daiichi Sankyo and AstraZeneca, which carries FDA approval for HER2-positive gastric and GEJ adenocarcinoma in the post-trastuzumab setting based on the DESTINY-Gastric programme. Ramucirumab plus paclitaxel, approved for second-line gastric cancer regardless of HER2 status, remains a standard backbone against which novel agents in this line are benchmarked. Anbenitamab’s bispecific mechanism distinguishes it from both, though head-to-head data against these agents are not available from the source material.

CSPC has also indicated that anbenitamab is under evaluation in HER2-positive breast cancer. A Phase III neoadjuvant study combining anbenitamab with HB1801 — the company’s proprietary albumin-bound docetaxel formulation — met its primary endpoint of total pathological complete response rate in March 2026. Registrational first-line breast cancer data from a separate Phase III study are expected later this year, suggesting the gastric approval may serve as a regulatory foundation for a broader oncology programme.