Two-cohort Study of Niraparib and Dostarlimab Plus (Chemo)RadIotherapy in Locally-Advanced Head and Neck Squamous Cell Carcinoma

Multi-center, open-label, non-randomized, non-comparative two-cohort study for patients with locally-advanced squamous cell carcinoma arising from the larynx, hypopharynx, oropharynx (Stage III, IVA and IVB according to 8th TNM/AJCC ed.) and oral cavity (unresectable, stage IVB according to 8th TNM/ American Joint Committee on Cancer (AJCC) ed.) who are candidates for definitive radiotherapy plus cisplatin (Cohort A) or as single-modality (in cisplatin unfit patient population) (Cohort B) and will receive dostarlimab and niraparib in combination pre-, during and post- radiation. Study has three parts: 1. Neoadjuvant phase (immune-conditioning phase): patients will receive 1 dose of dostarlimab + niraparib from day -14 prior to radiotherapy (up to 48h prior to radiotherapy (RT) in Cohort A and until RT in Cohort B). 2. Concurrent phase (radiosensitization): patients will receive definitive radiotherapy (70Gy in 35 fractions) with concurrent cisplatin (Cohort A) or with concurrent niraparib (Cohort B). 3. Maintenance: Following radiotherapy, patients will receive adjuvant dostarlimab plus niraparib until week 48 (37 cycles) in both cohorts.