At the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, Abbisko Therapeutics presented preliminary results from a Phase II clinical study evaluating its independently developed first-in-class oral highly selective FGFR2/3 inhibitor, ABSK061, in combination with the oral PD-L1 inhibitor ABSK043, with or without CAPOX (oxaliplatin plus capecitabine), in patients with FGFR2-positive advanced gastric cancer and gastroesophageal junction cancer (GC/GEJC). The study demonstrated a favorable safety profile and promising anti-tumor activity of ABSK061 plus ABSK043, with or without CAPOX, in patients with FGFR2-positive advanced GC/GEJC, highlighting the potential of this targeted and immunotherapy combination as a promising new treatment option for this patient population.

Gastric cancer and gastroesophageal junction cancer are among the most common and deadly malignancies worldwide, with poor overall prognosis in patients with advanced disease. Aberrant FGFR2 signaling has been identified as an important molecular driver of GC/GEJC development and progression. FGFR2b overexpression is observed in approximately 16%–30% of patients in this tumor type, while FGFR2 gene amplification occurs in about 5%–10% of gastric cancer cases. Although FGFR2 has emerged as an important therapeutic target in GC/GEJC, there remains a significant unmet need for oral treatment options that combine efficacy, tolerability, and convenience.

The study was designed to evaluate the safety and preliminary efficacy of the targeted-immunotherapy combination of ABSK061 and ABSK043, with or without CAPOX, in patients with FGFR2-positive GC/GEJC. As of January 2026, a total of 37 patients had been enrolled, including 24 previously treated (2L+) patients and 13 treatment-naïve (1L) patients. No dose-limiting toxicities (DLTs) were observed during the study.

In terms of safety, the combination regimen demonstrated an overall manageable safety profile. All FGFR-related adverse events (AEs) were infrequent and were effectively managed through dose modifications, with no permanent treatment discontinuations reported. These events included ocular events (Grade 3, 2.7%), stomatitis (Grade 3, 2.7%), and nail disorders (all Grade 1–2).

In terms of efficacy, among 10 treatment-naïve FGFR2-positive GC/GEJC patients who completed at least 1 treatment cycle, all patients showed target-lesion shrinkage, and 9 achieved partial response (PR) per RECIST v1.1, yielding an objective response rate (ORR) of 90%. Among 16 evaluable pretreated patients, 5 achieved PR, corresponding to an ORR of 31.3%, with the longest treatment duration reaching 7.6 months.

These findings demonstrate that ABSK061 in combination with ABSK043, with or without CAPOX, exhibits a favorable safety profile and promising anti-tumor activity in both treatment-naïve and pretreated patients with FGFR2-positive advanced GC/GEJC. The results support further clinical development of both the doublet and quadruplet regimens in this patient population.

Reference

1. J Clin Oncol 44, 2026 (suppl 16; abstr e16036)

About ABSK043

ABSK043 is a novel, orally bioavailable, highly selective small molecule PD-L1 inhibitor wholly owned by Abbisko Therapeutics. Tumor cells can exploit immune checkpoints such as PD-1 and its ligand PD-L1 to evade immune detection and clearance, thereby suppressing or limiting T-cell responses. ABSK043 selectively binds to the PD-L1 receptor and induces its internalization from the cell surface, effectively inhibiting the PD-1/PD-L1 interaction and alleviating PD-L1-mediated suppression of T-cell activation. In preclinical models, ABSK043 has demonstrated anti-tumor efficacy comparable to approved PD-L1 antibodies. While several PD-1/PD-L1 monoclonal antibodies have been approved worldwide, there are currently no approved orally bioavailable PD-1/PD-L1 small molecule drugs. ABSK043 is currently being explored in an ongoing Phase I clinical trial for advanced solid tumors in Australia and China.

About ABSK061

ABSK061 is a novel, orally bioavailable, highly potent and selective small molecule inhibitor of FGFR2 and FGFR3 independently discovered and wholly-owned by Abbisko Therapeutics. It is the first FGFR2/3 inhibitor to enter clinical trials globally. First-generation pan-FGFR inhibitors demonstrated clinical efficacy in multiple tumors carrying FGFR2/3 variants and have steadily gained regulatory approval globally. However, the therapeutic window of pan-FGFRs and their clinical efficacy have been limited by side effects associated with FGFR1 inhibition. By reducing FGFR1 activity while maintaining potency against FGFR2 and FGFR3, ABSK061 is expected to achieve a wider therapeutic window with improved clinical efficacy as a new-generation of FGFR inhibitors. ABSK061 for the treatment of achondroplasia has received both Rare Pediatric Disease Designation (RPDD) and Orphan Drug Designation (ODD) from the U.S. Food and Drug Administration (FDA), and its Phase II clinical trial is currently ongoing.

About Abbisko Therapeutics

Founded in April 2016, Abbisko Therapeutics Co., Ltd. (HKEX: 02256.HK), is an oncology-focused biopharmaceutical company based in Shanghai that is dedicated to the discovery and development of innovative medicines to treat unmet medical needs in China and globally. Abbisko was established by a group of seasoned drug hunters with rich research & development and managerial expertise from top multinational pharmaceutical companies. Since its founding, Abbisko Therapeutics has built an extensive pipeline of innovative programs focused on precision oncology and immuno-oncology.

Please visit www.abbisko.com for more information.