CHENGDU, China, June 3, 2026 /PRNewswire/ -- Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. ("Kelun-Biotech" or the "Company", 6990.HK) announced that at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting held in Chicago, USA, the first-in-human study results of the novel B7-H3 ADC SKB500 in patients with advanced solid tumors were presented as a rapid oral report by Professor Liu Haifeng from Jilin Provincial Cancer Hospital (Abstract #3011|Molecularly Targeted Agents and Tumor Biology).

SKB500 utilizes an antibody with high affinity, high hydrophilicity, and enhanced endocytosis, and has been engineered to silence Fc effector function in the constant region. Moreover, the antibody is conjugated to a payload with moderate toxicity via a cleavable hydrophilic AAA linker, with a drug-to-antibody ratio (DAR) of approximately 8.

The study was divided into three stages: dose escalation, dose expansion, and indication expansion, enrolling a total of 192 patients, including those with small cell lung cancer (SCLC), esophageal squamous cell carcinoma (ESCC), head and neck squamous cell carcinoma (HNSCC), colorectal cancer (CRC), neuroendocrine carcinoma (NEC), and other tumors. Patients received SKB500 at doses ranging from 2 to 18 mg/kg every three weeks (Q3W), with dose expansion and indication expansion conducted at 12 mg/kg and 16 mg/kg.

As of March 31, 2026, efficacy data showed:

• Antitumor activities were observed across multiple solid tumor types, including SCLC, ESCC, HNSCC, pancreatic ductal adenocarcinoma (PDAC), non-small cell lung cancer (NSCLC), and nasopharyngeal carcinoma (NPC). Among 124 patients treated at 12 mg/kg with at least 6 weeks of follow-up, the objective response rate (ORR) was 42.7%, and the disease control rate (DCR) was 83.9%.
• Among the treated SCLC patients (n=40), the ORR was 65.0% (95% CI: 48.3, 79.4), median progression-free survival (mPFS) was 7.2 months (95% CI: 4.3, NE), DCR was 95.0%, and mDOR was 5.8 months.
• Among the treated ESCC patients (n=37), the ORR was 54.1%.

In terms of safety, compared to the 16 mg/kg group, the 12 mg/kg group demonstrated a more favorable safety profile, characterized by a lower incidence of grade ≥3 treatment-related adverse events (TRAEs) and treatment-related serious adverse events (TRSAEs), as well as a low rate of permanent discontinuation. In the 12 mg/kg group, the incidence of grade ≥3 TRAEs was 32.3%, most commonly hematologic events.

The study demonstrates that SKB500 exhibits broad-spectrum antitumor activity, with responses observed in multiple treated advanced solid tumors including SCLC, ESCC, HNSCC, and PDAC, with notable efficacy in SCLC patients. At the 12 mg/kg group, SKB500 showed a favorable safety profile, where there was a low incidence of permanent discontinuation and no treatment-related deaths.

Professor Liu Haifeng, Principal Investigator from Jilin Provincial Cancer Hospital, said: "The positive results from this first-in-human study of SKB500 not only preliminarily confirm its favorable efficacy and manageable safety profile as a novel B7-H3 ADC, but also suggest its therapeutic potential in multiple solid tumors—offering particular hope for SCLC, a disease that is highly aggressive and has limited later-line treatment options. These findings lay a solid foundation for further clinical development. We look forward to further validating its clinical value in subsequent trials."

About SKB500

SKB500 is a novel B7-H3-targeted ADC independently developed by the company using its OptiDC™ platform technology, featuring a site-specific cleavable linker and a potent topoisomerase I inhibitor. In the Phase I clinical study, SKB500 demonstrated robust efficacy and manageable safety profiles across multiple advanced solid tumors. Currently, a Phase II exploratory study of SKB500 in combination with immunotherapy with or without chemotherapy as first-line treatment for extensive-stage small cell lung cancer (ES-SCLC) is ongoing in China.

About Kelun-Biotech

Kelun-Biotech (6990.HK) is a holding subsidiary of Kelun Pharmaceutical, which focuses on the R&D, manufacturing, commercialization and global collaboration of innovative biological drugs and small molecule drugs. Kelun-Biotech focuses on major disease areas such as solid tumors, autoimmune, and metabolic diseases, and in establishing a globalized drug development and industrialization platform to address the unmet medical needs in China and the rest of world. Kelun-Biotech is committed to becoming a leading global enterprise in the field of innovative drugs. At present, Kelun-Biotech has more than 30 ongoing key innovative drug projects, of which 4 projects with 8 indications have been approved for marketing, 1 project is in the NDA stage and more than 10 projects are in the clinical stage. Kelun-Biotech has established one of the world's leading proprietary ADC and novel DC platforms, OptiDC™, and has 2 ADC projects with 5 indications approved for marketing, and multiple ADC and novel DC assets in clinical or preclinical research stage. For more information, please visit https://en.kelun-biotech.com/.

Source: Kelun-Biotech Related Stocks: HK:6990 HongKong:6990