Kelun-Biotech SKB500 shows 65% response rate in SCLC at ASCO 2026

Kelun-Biotech's novel B7-H3 ADC SKB500 posted a 65% objective response rate in small cell lung cancer patients in a Phase I study presented at the ASCO 2026 annual meeting.

"These positive results not only preliminarily confirm SKB500's favorable efficacy and manageable safety profile but also suggest its therapeutic potential in multiple solid tumors, offering particular hope for SCLC," Professor Liu Haifeng, Principal Investigator from Jilin Provincial Cancer Hospital, said.

Among 124 patients treated at 12 mg/kg with at least six weeks of follow-up, the objective response rate was 42.7% and the disease control rate was 83.9%. In SCLC patients specifically, median progression-free survival reached 7.2 months and the disease control rate was 95%. In esophageal squamous cell carcinoma, the response rate was 54.1%.

The study enrolled 192 patients across dose escalation, dose expansion and indication expansion stages, including those with SCLC, ESCC, head and neck squamous cell carcinoma, colorectal cancer and neuroendocrine carcinoma. Doses ranged from 2 to 18 mg/kg every three weeks, with expansion cohorts at 12 mg/kg and 16 mg/kg.

SKB500 uses a high-affinity antibody with enhanced endocytosis and silenced Fc effector function, conjugated to a topoisomerase I inhibitor payload via a cleavable hydrophilic AAA linker. The drug-to-antibody ratio is approximately 8. The molecule was developed on Kelun-Biotech's OptiDC platform.

At the 12 mg/kg dose, the incidence of grade three or higher treatment-related adverse events was 32.3%, most commonly hematologic events. No treatment-related deaths occurred and the rate of permanent discontinuation was low. The 12 mg/kg dose showed a more favorable safety profile compared with the 16 mg/kg group.

Despite the positive data, Kelun-Biotech shares fell 8.2% after the ASCO presentation, reflecting potential profit-taking or expectations of even stronger results. The data positions SKB500 as a potential later-line option for SCLC, a highly aggressive cancer with limited treatment options after frontline therapy. A Phase II exploratory study combining SKB500 with immunotherapy, with or without chemotherapy, as first-line treatment for extensive-stage SCLC is already underway in China.

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