ESMO Congress 2026

Anbenitamab (Ennituo®) is a HER2 bispecific IgG monoclonal antibody developed by Alphamab Oncology, a biparatopic molecule that induces profound receptor clustering ^[3][4]. As a class, bispecific antibodies have entered their harvest period: among the 21 antibody therapeutics approved in 2024, several were bispecifics ^[1]. For this asset specifically, the evidence base is established: the randomized, double-blind phase III KC-WISE trial enrolled 188 patients with trastuzumab-pretreated HER2-positive gastric/gastroesophageal junction (GEJ) adenocarcinoma across 51 sites in China, randomized 1:1 to anbenitamab 30 mg/kg every 3 weeks or placebo, combined with taxane or irinotecan chemotherapy, with independent review committee-assessed PFS and OS as primary endpoints ^[2]. On this basis, anbenitamab plus chemotherapy was approved in China on 27 May 2026 for adults with locally advanced or metastatic HER2-positive gastric/GEJ adenocarcinoma who had previously received at least one trastuzumab-containing regimen ^[3]. In breast cancer, a neoadjuvant phase III trial of anbenitamab plus the solvent-free albumin-bound docetaxel HB1801 versus trastuzumab + pertuzumab + docetaxel (± carboplatin) has also been conducted across 61 hospitals in China ^[4].

At ESMO26, anbenitamab delivered two readouts. First, the updated OS analysis of KC-WISE in previously treated HER2-positive GC/GEJC: ORR 56% vs 13%, median OS 19.6 vs 9.7 months, and no unexpected safety signal; the post noted the results support sequential HER2 targeting after trastuzumab. Second, a phase III in first-line HER2-positive mBC: anbenitamab + nab-paclitaxel versus THP, with PFS not reached vs 14.3 months (HR 0.46), ORR 87.6% vs 73.4%, and OS still immature; the same post cautioned that the two arms used different chemotherapy regimens, making it difficult to determine anbenitamab's independent contribution.

The advances fall on two tracks. In gastric cancer, KC-WISE already had PFS and OS as co-primary endpoints ^[2]; this update further widens the median OS gap (19.6 vs 9.7 months), adding survival evidence for the approved pretreated indication ^[3] and reinforcing the strategy of continued HER2 blockade after prior trastuzumab. In breast cancer, the readout moves the asset from the early neoadjuvant setting ^[4] into first-line metastatic disease head-to-head with THP; if the HR 0.46 PFS benefit translates into mature OS, this bispecific could carve out a front-line chemo-combination position within a landscape dominated by ADCs such as trastuzumab deruxtecan that treat HER2 as a biological continuum ^[5].

The limitations are equally clear: the breast cancer trial used different chemotherapy backbones in the two arms, so the efficacy difference cannot be fully attributed to anbenitamab, and OS remains immature; KC-WISE was conducted only in China with 188 patients ^[2], and the OS figures presented are conference-level numbers, with fuller data pending confirmation.