Pembrolizumab melanoma trial posts near pCR rates up to 19.2%

ClinicalTrials.gov posted results on 27 August 2026 for a completed pembrolizumab substudy in participants with stage III melanoma who were candidates for neoadjuvant therapy. Among the reported treatment groups, the near pathologic complete response rate ranged from 0.0% with pembrolizumab plus all-trans retinoic acid to 19.2% with favezelimab plus pembrolizumab.

Background

Substudy 02C evaluated pembrolizumab alone and in combination with investigational agents in participants with stage III melanoma. The study was part of the KEYMAKER-U02 umbrella research program and was designed to assess safety and efficacy while identifying investigational combinations that could be superior to current treatment options or a historical control.

Trial design

This was a Phase 1/Phase 2 study that enrolled 146 participants with melanoma and was listed as completed. The registered treatment groups included pembrolizumab plus vibostolimab, pembrolizumab plus gebasaxturev, pembrolizumab alone, pembrolizumab plus MK-4830, favezelimab plus pembrolizumab, and pembrolizumab plus all-trans retinoic acid.

The supplied record did not include primary outcome entries. It did report near pathologic complete response rates with 90% and 95% confidence-interval labels for the treatment groups, but no confidence-interval values were provided.

Key results

The reported near pCR rates were 11.5% for pembrolizumab plus vibostolimab, 12.0% for pembrolizumab plus gebasaxturev, 6.7% for pembrolizumab alone, and 4.0% for pembrolizumab plus MK-4830.

Favezelimab plus pembrolizumab had the highest reported rate at 19.2%. Pembrolizumab plus all-trans retinoic acid had a reported rate of 0.0%. The same numerical rates were listed under both the 90% and 95% confidence-interval outcome labels. No p-values, interval estimates, comparative analyses, or adverse-event summary were supplied.

What this means

The registry results provide a descriptive comparison of near pCR rates across pembrolizumab-containing treatment groups in this completed stage III melanoma substudy. The reported values identify favezelimab plus pembrolizumab as having the highest observed rate among the listed groups, while the pembrolizumab-plus-ATRA group had no reported near pCR events.

Because the supplied data do not include confidence-interval values, statistical tests, primary outcomes, or adverse-event findings, they do not establish whether any combination was superior or safer than another. The results also do not indicate a new approval or a change to pembrolizumab’s clinical use.

Source

Source: ClinicalTrials.gov, registry record for Substudy 02C, NCT04303169, with trial results posted on 27 August 2026. The record is available at clinicaltrials.gov/study/NCT04303169.