O002

Thursday, November 13th, 2025 17:00 – 17:10
Speaker Paolo Bossi

Dostarlimab monotherapy as first-line treatment in PD-L1–positive recurrent/metastatic head and neck squamous cell carcinoma: safety and efficacy from the GALAXIES H&N-202 interim analysis

Objectives: Immune checkpoint inhibitors have improved outcomes for patients with recurrent or metastatic HNSCC [1–3]; however, overall survival for recurrent/metastatic disease remains poor. GALAXIES H&N-202 (NCT06062420) is a Phase 2 platform study evaluating the safety and efficacy of novel immunotherapy combinations versus dostarlimab monotherapy as first-line treatment in patients with recurrent/metastatic PD-L1-positive HNSCC. Here, we report the first interim results for patients who were randomised to the dostarlimab monotherapy arm.

Methods: GALAXIES H&N-202 is an open-label, Phase 2 platform study evaluating novel immunotherapy combinations in patients with PD-L1-positive (combined positive score [CPS] ≥1) recurrent/metastatic HNSCC previously untreated in this setting. Patients randomised to the dostarlimab monotherapy arm received dostarlimab 500 mg every 3 weeks until progression, unacceptable toxicity, death or withdrawal. The primary endpoint was investigator-confirmed objective response rate (ORR) per Response Evaluation Criteria in Solid Tumours (RECIST) version 1.1. Safety was a secondary endpoint.

Results: At data cutoff (20 March 2025), 161 patients had been enrolled into the trial and had at least 4.5 months of follow-up data from first dose. Among this cohort, 41 patients were randomised to the dostarlimab monotherapy arm (mean age 65.7 years; 71% male). After a median (range) of 18.0 (354) weeks of treatment, ORR in this cohort of patients was 26.8% (95% confidence interval [CI]: 14.2, 42.9) (Table 1). Treatment-emergent adverse events (TEAEs) were reported in 90% (n=37) of patients, with 54% (n=22) of patients reported to have treatment-related adverse events (TRAEs; Table 2). Grade 3+ TEAEs occurred in 34% (n=14) of patients, with 5% (n=2) of patients reported to have Grade 3+ TRAEs. Overall, 5% (n=2) of patients experienced treatment-related serious adverse events (SAEs), and 5% (n=2) of patients discontinued treatment due to TEAEs. There were 5 fatal SAEs, none of which were treatment related.

Conclusion: In this interim analysis, dostarlimab monotherapy showed anti-tumour activity in HNSCC with a safety profile similar to that observed for other immune checkpoint inhibitors used in HNSCC [1–3]. Results for additional substudy arms and from additional patients in the dostarlimab monotherapy arm will be reported in future.

References:
1. Ferris RL, et al. N Engl J Med 2016;375(19):1856–67.
2. Cohen EEW, et al. Lancet 2019;393(10167):156–67.
3. Burtness B, et al. Lancet 2019;394(10212):1915–28.

Funding: This study (NCT06062420; GSK Study 219885) was funded by GSK. Medical writing support was provided by Avalere Health, funded by GSK.