Dual-Payload ADC Enters the Clinic: Kelun’s SKB565 Cleared for Trials Targeting Advanced Solid Tumors

Antibody-drug conjugates (ADCs) typically use an antibody as a guide to deliver cytotoxic drugs into tumors. Sichuan Kelun-Biotech Biopharmaceutical is now seeking to add another layer of functionality to this framework: its SKB565 carries both a toxin and an immunomodulator and has received implied permission for a clinical trial from the Center for Drug Evaluation of China’s National Medical Products Administration, with development targeting advanced solid tumors.

This permission means that SKB565 may legally proceed to human studies; it does not mean that the trial has begun enrolling patients, nor does it constitute approval of efficacy or marketing authorization. An official announcement from Kelun Pharmaceutical, information released by Kelun-Biotech, and a report by Yicai all confirm that SKB565 is the company’s first dual-payload ADC to enter clinical development.

SKB565 originated from Kelun-Biotech’s OptiDC platform. According to the company, the two types of payload are designed to exert complementary effects after reaching tumor tissue: the toxin directly kills cancer cells, while the immunomodulator alters the tumor microenvironment and triggers an antitumor immune response. This differs from most conventional ADCs, which carry only cytotoxic drugs, and also reflects how ADC development is shifting from delivering a single drug toward integrating multiple therapeutic mechanisms into one molecule.

However, currently available public information has not disclosed the tumor antigen recognized by SKB565, the specific identities of the two payloads, the drug-to-antibody ratio, or how the linker controls payload release. These factors will directly affect whether the drug can concentrate in tumors, whether it produces a bystander effect, and the extent of normal-tissue exposure and systemic toxicity. They are also critical to assessing whether the dual-payload design can translate into a clinical advantage.

Kelun-Biotech said that SKB565 demonstrated antitumor activity and safety in preclinical studies, but it did not simultaneously disclose the models, comparator groups, dose ranges, or complete toxicology data. At this stage, these findings can therefore only be regarded as company data supporting progression into human trials and cannot yet be used to determine whether it is more effective than single-payload ADCs, immunotherapy combination regimens, or other next-generation conjugates.

The upcoming early-stage clinical studies will first need to address questions including the tolerated dose, dose-limiting toxicities, and pharmacokinetics, while also confirming whether the two payloads can maintain their expected synergistic effect in humans. A dual-payload approach may broaden the mechanism of action, but it also makes manufacturing consistency, molecular stability, and attribution of toxicity more difficult. The real test will be whether this design can convert its added complexity into measurable and durable clinical benefits.