Coherus Reports 75% Response Rate with Tagmokitug in First-Line ESCC

Coherus Oncology has reported interim results from its Phase 1b TREGCHECK 102 study evaluating tagmokitug, an investigational cytolytic anti-CCR8 antibody, with the PD-1 inhibitor toripalimab, with or without chemotherapy. In previously untreated advanced or metastatic esophageal squamous cell carcinoma (ESCC), the combination of tagmokitug, toripalimab, 5-fluorouracil and cisplatin produced a confirmed overall response rate (cORR) of 75% at the October 14, 2026, data cutoff. The findings are preliminary, enrollment continues, and safety is the primary endpoint.

First-Line ESCC: Encouraging Responses in a Small Cohort

In Cohort C, 10 patients were safety-evaluable and eight were efficacy-evaluable at the cutoff. Six of eight patients had confirmed responses, including one complete response, yielding a cORR of 75%.

After the cutoff, a previously unconfirmed partial response was confirmed and one newly evaluable patient had a confirmed partial response. The updated analysis reported eight responses among nine evaluable patients, increasing the cORR to 89%. This post-cutoff result should remain distinct from the original analysis because it reflects a later evaluable dataset.

Coherus also reported a 100% cORR among PD-L1-positive patients, but the announcement did not disclose the subgroup denominator. The company cited a 44%–59% response-rate benchmark for PD-1 inhibitor plus chemotherapy in PD-L1-positive ESCC. This cross-trial comparison cannot establish superiority because differences in patient characteristics, follow-up and study design may affect response rates. The company also noted that PD-1 inhibitors are not approved for PD-L1-negative ESCC in the United States. The interim results do not establish tagmokitug’s benefit in this subgroup.

Second-Line ESCC: PFS Needs Comparative Evidence

Cohort B enrolled patients with recurrent or metastatic ESCC after first-line systemic chemotherapy, with or without a PD-1 inhibitor. Patients were randomized 1:1 to tagmokitug 300 mg or 700 mg plus toripalimab. At cutoff, 17 patients were safety-evaluable, but only eight were efficacy-evaluable: two in the 300 mg arm and six in the 700 mg arm.

In the 700 mg group, cORR was 16.7% (1/6), clinical benefit rate was 33.3% (2/6), and median progression-free survival (PFS) was 5.5 months. The company cited approximately 3.4 months as a US chemotherapy benchmark. The numerical difference does not demonstrate improved PFS because the comparison was not randomized against chemotherapy and the efficacy dataset contained only six patients. The company also reported an unconfirmed partial response in this group, which should not be counted toward cORR.

Findings Across Other Tumours Remain Exploratory

In second-line HPV-positive head and neck squamous cell carcinoma, the combined-dose analysis showed a cORR of 13.0% (3/23) and clinical benefit rate of 26.1% (6/23). Patients positive for the exploratory Tumour Immune Regulatory Index (TIRI) had a 45% clinical benefit rate (6/11). This subgroup finding does not validate TIRI as a predictive biomarker.

In upper gastrointestinal cancers, four confirmed partial responses among 17 efficacy-evaluable patients receiving the 700 mg dose corresponded to a cORR of 23.5%. Across both dose groups, 40 patients had been treated and 33 were efficacy-evaluable. In heavily pretreated, non-liver-metastatic microsatellite-stable colorectal cancer, cORR was 5.9% and clinical benefit rate was 11.8% among 17 efficacy-evaluable patients. These uncontrolled findings are hypothesis-generating and do not establish reversal of PD-1 resistance.

Safety: No New Signal, but Monitoring Remains Important

Among 33 patients receiving tagmokitug monotherapy, no dose-limiting toxicities were reported through 1,200 mg every three weeks. Across 120 patients receiving tagmokitug plus toripalimab, immune-related adverse events occurred in 40%, with Grade 3–5 events in 20%. Common treatment-related adverse events included infusion-related reactions (25.0%), fatigue (19.2%) and rash (15.8%). No Grade 5 treatment-related adverse events were reported across the combination safety population.

In the first-line ESCC cohort, the company reported no new safety signals or Grade 5 treatment-emergent adverse events among 10 patients. These observations are preliminary, and the small cohort cannot characterise uncommon or delayed toxicities.

Clinical Interpretation

The first-line ESCC response signal supports further investigation, not established clinical benefit. Safety remains the primary endpoint, while response durability, mature PFS, baseline characteristics and biomarker findings require further evaluation. Coherus plans to expand enrollment in both first-line and second-line ESCC and continue assessing outcomes as data mature. The company is also planning a study combining tagmokitug with a T-cell engager in metastatic castration-resistant prostate cancer.

Tagmokitug remains investigational and has not been approved by the FDA or any other regulatory authority. Its safety and efficacy have not been established.

Reference

Coherus Oncology Announces Compelling Tagmokitug Interim Clinical Data in Esophageal Cancer and Path to Advance Development, Coherus Oncology, October 28, 2026.

A Study of CHS-114 (Tagmokitug) in Combination with Toripalimab and/​or Other Treatments in Participants with Advanced Solid Tumors, ClinicalTrials.gov ID NCT06657144