Kelun-Biotech to test B7-H3 ADC plus PD-1 blocker in esophageal cancer
The Phase 2 combination trial adds a sixth industry program to a B7-H3 field in esophageal squamous cell carcinoma with no completed or terminated precedent yet.
Executive Summary
- A Chinese biopharmaceutical company has registered a mid-stage combination trial pairing its B7-H3-targeted antibody-drug conjugate with a PD-1 blocker in a squamous cancer of the esophagus, testing the regimen in patients who have not previously received either drug class.
- The trial builds in a safety run-in before expanding to randomized enrollment, an approach that establishes tolerability before committing a larger population to the combination.
- The combination enters a target-indication pairing where several industry sponsors are active but none has yet completed or terminated a program, leaving no track record either supporting or cautioning against the mechanism in this disease.
- With enrollment not yet open and a primary completion date years out, the near-term signal to watch is whether the safety run-in clears cleanly and the trial transitions into its randomized phase on schedule.
The trial
NCT07700667 is a Phase 2 study of SKB500 combined with a PD-1 blocker in patients with unresectable locally advanced, recurrent, or metastatic esophageal squamous cell carcinoma who are ineligible for curative-intent therapy. The trial targets 120 patients across sites in China, with a start date of July 30, 2026, and a primary completion date of December 31, 2028. It is registered as non-registrational, meaning it is not designed to directly support marketing approval. The primary outcome is the incidence and severity of adverse events and serious adverse events graded by CTCAE v6.0, positioning this as a safety- and tolerability-focused readout rather than an efficacy-driven one, alongside a co-primary objective response rate endpoint assessed by RECIST v1.1. NCT07700667SKB500 Combinations in Patients With Esophageal Squamous Cell CarcinomaNCT07700667
The design
The trial structure moves through a safety run-in across four cohorts before a randomized enrollment phase and a cohort expansion phase. Eligibility excludes any patient previously treated with a B7-H3-targeted agent, including antibody, antibody-drug conjugate, or other modality, and excludes prior treatment with any ADC built on a topoisomerase I inhibitor payload. That exclusion isolates the combination's effect in a population naive to both the target and the payload class, rather than testing SKB500 as a rescue option after those mechanisms have already failed. Secondary endpoints include disease control rate, duration of response, progression-free survival, overall survival, and biomarker correlation with PD-L1, B7-H3, and SLFN11 expression in tumor tissue. NCT07700667SKB500 Combinations in Patients With Esophageal Squamous Cell CarcinomaNCT07700667
The field
Six industry trials are active studying B7-H3 in esophageal squamous cell carcinoma, spanning six sponsors with a maximum phase of Phase 3, and none has completed or been terminated. The closest direct comparator by target is BioNTech's BNT324, a B7-H3-directed antibody-drug conjugate now in Phase 3 testing for prostate cancer, a different indication. Merck's ifinatamab deruxtecan, also B7-H3-directed, is in Phase 1/2 testing across tumors. Within esophageal squamous cell carcinoma specifically, the nearest mechanism neighbor is pembrolizumab, a PD-1 blocker sharing the same immune-checkpoint target as SKB500's combination partner, currently in Phase 1/2 testing under Merck's KEYMAKER-U06 umbrella study. Median trial duration for B7-H3 x esophageal squamous cell carcinoma programs runs 858 days, with a range of 803 to 1,215 days across five trials.
Sponsor track record
Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. has completed 6 of 8 prior trials globally, a 75% completion rate, with 2 terminated. The company's broader pipeline spans 51 trials, with 21 recruiting, 13 active and not recruiting, and 9 not yet recruiting including this one. SKB500 has no other trials in the company's asset portfolio beyond this program, making this the drug's sole active clinical study.
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