Dostarlimab monotherapy as a first-line treatment produced a confirmed objective response rate of 27% in patients with PD-L1–positive recurrent or metastatic head and neck squamous cell carcinoma, according to updated data from the phase 2 GALAXIES H&N-202 trial presented at the 2026 ASCO Annual Meeting. Researchers reported that efficacy varied significantly by PD-L1 expression levels, with higher combined positive scores yielding a 42% response rate alongside manageable toxicity profiles.
GALAXIES H&N-202 Trial Design and Patient Demographics
The GALAXIES H&N-202 trial evaluated dostarlimab as monotherapy or in combination with investigational immune checkpoint inhibitors, according to study protocols on ClinicalTrials.gov. Investigators randomized previously untreated patients to receive dostarlimab monotherapy at 500 mg or one of four combination sub-studies. Dr. Robert Haddad and fellow researchers presented the monotherapy findings at the ASCO meeting.
At the July 14, 2025, data cutoff, 66 patients were enrolled in the monotherapy arm and 65 received treatment, with a minimum follow-up of 4.5 months. Median patient age was 66 years, and 80% of participants were male. Disease presentation included de novo metastatic disease in 20% of patients, locoregional recurrence in 29%, and distant metastatic recurrence in 52%. Primary tumors were non-oropharyngeal in 61% of patients and oropharyngeal in 39%.
Efficacy and Subgroup Findings Based on PD-L1 Expression
Response rates in the trial tracked closely with PD-L1 expression levels, according to presentation data. Patients with a CPS of 20 or higher achieved a confirmed objective response rate of 42%, compared with 12% in those with a CPS between 1 and 19. Median progression-free survival reached 4 months in the overall population, but extended to 8 months in the CPS ≥20 subgroup.
Per RECIST v1.1 criteria, best overall responses included complete responses in 2% of patients and partial responses in 26%. In the high-expression CPS ≥20 subgroup, investigators observed complete responses in 3% of patients and partial responses in 39%. Conversely, the CPS 1-19 subgroup recorded no complete responses and a 12% partial response rate, backed by waterfall analysis showing deeper target lesion reductions in the high-CPS cohort.
Safety Profile and Treatment-Related Adverse Events
Treatment-emergent adverse effects of any grade occurred in 91% of treated patients, with grade 3 or higher events reported in 32%, according to trial safety analyses. Five percent of patients discontinued treatment due to adverse effects. Treatment-related adverse events occurred in 51% of patients, with grade 3 or higher treatment-related toxicities confined to 5% of the cohort.
Investigators noted that immune-mediated treatment-related adverse effects remained generally mild and consistent with known profiles of PD-1 inhibitors. Serious adverse effects occurred in 26% of patients, while treatment-related serious adverse effects were documented in 5% of participants, including single cases of diarrhea, immune-mediated lung disease, and cytokine release syndrome. Fatal serious adverse effects occurred in 11% of patients, though investigators confirmed none were treatment-related.
The safety and efficacy data support continued clinical investigation of dostarlimab in head and neck squamous cell carcinoma, according to the study authors. Ongoing evaluation includes the phase 3 JADE trial, which is testing sequential dostarlimab following chemoradiotherapy in patients with locally advanced, unresected PD-L1–positive disease. Overall survival follow-up for the GALAXIES H&N-202 trial remains ongoing.
Did You Know? The phase 3 JADE trial is actively investigating whether sequential dostarlimab can improve outcomes for patients with locally advanced, unresected head and neck cancer following standard chemoradiotherapy.
Frequently Asked Questions
What was the overall response rate for dostarlimab monotherapy in the trial?
The investigator-assessed confirmed objective response rate was 27% in the overall population, according to trial data presented at the ASCO Annual Meeting.
How did PD-L1 expression affect patient outcomes?
Patients with a PD-L1 combined positive score of 20 or higher experienced a 42% response rate and an 8-month median progression-free survival, compared to a 12% response rate and 3-month progression-free survival in patients with a CPS of 1 to 19.
What are the next steps for testing dostarlimab in head and neck cancer?
Researchers are currently evaluating dostarlimab in the phase 3 JADE trial as a sequential treatment following chemoradiotherapy for locally advanced, unresected disease.
Want to stay updated on the latest oncology clinical trials and immunotherapy breakthroughs? Subscribe to our weekly newsletter or share your thoughts in the comments below.
Keep reading