On October 18, 2025 Alphamab Oncology (Stock Code: 9966.HK) reported that the first interim analysis results of a phase III clinical trial of anbenitamab injection (KN026), independently developed by the Company and co-developed with JMT-Bio Technology Co., Ltd., a wholly-owned subsidiary of CSPC Pharmaceutical Group Co., Ltd. (stock code: 1093.HK), in combination with chemotherapy as second-line or above treatment of HER2-positive gastric cancer (GC) (including gastroesophageal junction cancer (GEJ)) (Study ID: KN026-001, also known as KC-WISE), have been presented at the 2025 European Society for Medical Oncology Congress (ESMO Congress 2025) Late-Breaking Abstract (LBA) Oral Presentation Session.

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LBA Oral Presentation Session is a highly anticipated global highlight of the ESMO (Free ESMO Whitepaper) Congress. The research presented in this category is both highly topical and of significant clinical value. Their findings often herald potential impacts on current clinical practice and can even guide the future direction of entire therapeutic fields.

Title：KN026 in combination with chemotherapy for previously treated HER2-positive gastric or gastroesophageal carcinomas (GC/GEJC): Interim analysis of KC-WISE

Number: LBA 78

Speaker: Jianming Xu, Chinese PLA General Hospital

Date：Friday, 17 October 2025

METHODS

Enrolled patients in study KN026-001 (KC-WISE) with HER2-positive GC/GEJ who had disease progression after trastuzumab-based therapy were randomized to receive either anbenitamab (KN026) in combination with chemotherapy (the "Anbenitamab Group") or chemotherapy with placebo (the "Control Group"). The patients were stratified based on (i) type of chemotherapy, (ii) HER2 expression level, and (iii) number of prior lines of treatments.

RESULTS

At baseline, patient characteristics were generally well balanced between the two groups. The median age was approximately 64 in the Anbenitamab Group and 61 in the Control Group. In both groups, over 80% of patients had an ECOG PS of 1, and nearly all patients were diagnosed with stage IVB disease at enrollment. All patients had previously received chemotherapy, most commonly taxanes (over 70%), with the remainder receiving irinotecan-based regimens.

As of April 3, 2025, the median follow-up duration was 9.7 months (95% CI, 7.2 to 11.9 months) in the Anbenitamab Group and 9.8 months (95% CI, 7.4 to 12.9 months) in the Control Group.

Efficacy as assessed by the Independent Review Committee (IRC):

● The median treatment-related adverse event (PFS) for the Anbenitamab Group was 7.1 months, compared with 2.7 months in the Control Group. The hazard ratio (HR) is 0.25 (P value is 5.44 × 10⁻¹²), corresponding to a 75% reduction in the risk of disease progression or death.

● The median overall survival (OS) for the Anbenitamab Group was 19.6 months (not mature), compared with 11.5 months in the Control Group. The HR is 0.29, representing a 71% reduction in the risk of death, and P value is 1.56 × 10⁻6, which is well below the prespecified extremely stringent alpha threshold of 0.00001.

● The objective response rate (ORR) was 55.8% in the Anbenitamab Group versus 10.8% in the Control Group, while the disease control rate (DCR) was 80.0% and 41.9%, respectively. The median duration of response (DoR) was 8.2 months and 2.9 months, respectively.

Safety:

● The median treatment duration was 6.5 cycles in the Anbenitamab Group and 3.0 cycles in the Control Group.

● The incidence of Grade 3 treatment-emergent adverse events (TEAEs) or above was 60.6% in the Anbenitamab Group and 51.6% in the Control Group, while the incidence of serious adverse events (SAEs) was 31.9% and 33.3%, respectively.

● The most frequently observed Grade 3 treatment-related adverse events (TRAEs) or above in the Anbenitamab Group included neutropenia (29.8%), leukopenia (21.3%), anemia (18.1%), diarrhea (8.5%) and asthenia (8.5%), while the most frequently observed Grade 3 TRAEs or above in the Control Group included leukopenia (24.7%), neutropenia (21.5%), anemia (10.8%), diarrhea (7.5%) and thrombocytopenia (5.4%). The incidence of cardiotoxicity in both groups were both 3.2%, indicating fewer cardiac concerns.

CONCLUSIONS

The interim analysis demonstrated that anbenitamab achieved superior efficacy in second-line or third-line HER2-positive gastric cancer patients who had been previously treated with trastuzumab. The study met both its primary endpoints of PFS and OS with statistically significant and clinically meaningful improvements, indicating its potential to change clinical practice guidelines for the treatment of second-line or above gastric cancer. Compared with the recently published DESTINY-Gastric04 results of DS-8201 in second-line gastric cancer, anbenitamab demonstrates potential advantages in both efficacy and safety.

Prompted by these encouraging results of anbenitamab, we are preparing to expand clinical development into first-line and perioperative gastric cancer through new registrational trials, aiming to extend benefits to more patients. Meanwhile, JSKN003, an ADC built upon KN026, has demonstrated high-security profile and distinctive advantages. With multiple registrational studies currently advancing as planned, we anticipate even more outstanding performance from JSKN003 in the future.

About Anbenitamab (KN026)

Anbenitamab (KN026) is an anti-HER2 bispecific antibody independently developed by Alphamab Oncology using the proprietary Fc-based heterodimer bispecific platform technology called CRIB (Charge Repulsion Induced Bispecific). KN026 can simultaneously bind two non-overlapping epitopes of HER2, resulting in HER2 signal blockade.

Results from multiple clinical studies showed that KN026 has promising efficacy for the treatment of HER2-positive solid tumors, both in the first-line and in patients previously treated with trastuzumab. Currently, several pivotal trials of KN026 for second-line or above HER2-positive GC/gastroesophageal junction cancer (GEJ), first-line HER2-positive BC, neoadjuvant treatment of HER2-positive BC are being conducted. KN026 for the treatment of patients with HER2-positive GC who have failed first-line standard treatment was granted breakthrough therapy designation by the Center for Drug Evaluation (CDE) of the National Medical Products Administration of China (NMPA). KN026 for the treatment of HER2-positive or low expressing GC was granted Orphan Drug Designation (ODD) by the U.S. Food and Drug Administration (FDA). In September 2025, the first New Drug Application (NDA) for anbenitamab injection has been accepted by the NMPA for use in combination with chemotherapy in patients with HER2-positive locally advanced, recurrent, or metastatic GC/GEJ who have failed at least one prior systemic therapy (which must include trastuzumab in combination with chemotherapy).

In August 2021, the Company entered an agreement with JMT-Bio Technology Co., Ltd. ("JMT-Bio"), a wholly-owned subsidiary of CSPC Pharmaceutical Group Co., Ltd. ("CSPC") (stock code: 1093.HK), for the development and commercialization of KN026 in Mainland China. JMT-Bio was granted exclusive license rights of KN026 for the development and commercialization in the indications of BC an GC/GEJ in Mainland China (excluding Hong Kong, Macau and Taiwan).

(Press release, Alphamab, OCT 18, 2025, View Source [SID1234656997])