A Randomized, Double-Blind Placebo-Controlled, Phase 3 Study of Debio 1143 in Combination With Platinum-Based Chemotherapy and Standard Fractionation Intensity-Modulated Radiotherapy in Patients With Locally Advanced Squamous Cell Carcinoma of the Head and Neck, Suitable for Definitive Chemoradiotherapy (TrilynX)

Primary Outcome Measures  :

1. Event-Free Survival (EFS) [ Time Frame: Up to 5 years ]EFS is the time from the date of randomization to the date of first record of disease progression or death.
   

Secondary Outcome Measures  :

1. Progression-Free Survival (PFS) [ Time Frame: Up to 5 years ]PFS is the time from randomization to the earliest between PFS event or End of Study (EOS)
   
2. Overall survival (OS) [ Time Frame: Up to 5 years ]OS is the time from randomization to death due to any cause.
   
3. Locoregional Control (LRC) [ Time Frame: From randomization to the earliest between PFS event (progression at the site of the primary tumor or the locoregional lymph nodes) or EOS (Up to 5 years) ]
   
4. Safety and Tolerability as assessed by incidence and severity of Adverse Events (AEs), Serious Adverse Events (SAEs), AEs of Special Interest (AESIs), Changes in Laboratory Values, Vital Signs, Electrocardiogram (ECGs) and Extent of Exposure [ Time Frame: From signed informed consent to EOS (within 6.8 years) ]
   
5. Changes from Baseline in Global Health Status/Quality of Life (GHS/QoL) and Fatigue Symptom [ Time Frame: Prior to the first dose of study treatment (Baseline) and at the time of last follow-up (Up to 5 years) ]Change from baseline in GHS/QoL and Fatigue Symptom using the European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Core Questionnaire (EORTC QLQ-C30)
   
6. Changes from Baseline in Swallowing and Pain Symptoms [ Time Frame: Prior to the first dose of study treatment (Baseline) and at the time of last follow-up (Up to 5 years) ]Change from baseline in swallowing, and pain symptoms using the EORTC Head and Neck Questionnaire (EORTC QLQ-H&N35)

Inclusion Criteria:

• Eastern Cooperative Oncology Group performance status (ECOG PS) 0 or 1
• Histologically confirmed diagnosis in previously untreated Locally Advanced Squamous Cell Carcinoma of the Head and Neck (LA-SCCHN) participant (stage III, IVa or IVb according to the American Joint Committee on Cancer(AJCC))/Classification of malignant tumors: T=size of the primary tumor, N=regional lymph node involvement, M=distant metastasis (TNM) Staging System, 8th Edition.) suitable for definitive ChemoRadiotherapy (CRT), of at least one of the following sites: oropharynx, hypopharynx and larynx
• For OroPharyngeal Cancer (OPC) participants, primary tumors must be human papillomavirus (HPV)-negative as determined by p16 expression using immunohistochemistry
• Evaluable tumor burden (measurable and/or non-measurable tumor lesions) assessed by computed tomography scan (CT-scan) or magnetic resonance imaging (MRI), based on Response evaluation criteria in solid tumors (RECIST) version 1.1
• Peripheral neuropathy less than or equal to (<=) grade 2
• Adequate hematologic, renal and hepatic function
• Other protocol defined inclusion criteria may apply

Exclusion Criteria:

• Primary tumor of nasopharyngeal, paranasal sinuses, nasal or oral cavity, salivary, thyroid or parathyroid gland pathologies, skin or unknown primary site
• Metastatic disease (stage IVc as per AJCC/TNM, 8th Ed.)
• Prior definitive or adjuvant Radiotherapy (RT) and/or radical surgery to the head and neck region which may jeopardize the primary tumor irradiation plan, or any other prior SCCHN systemic treatment, including investigational agents
• Documented weight loss of >10% during the last 4 weeks prior to randomization (unless adequate measures are undertaken for nutritional support), OR plasmatic albumin < 3.0 g/dL. No albumin transfusions are allowed within 2 weeks before randomization
• Known allergy to Debio 1143, cisplatin, carboplatin, other platinum-based agent or any excipient known to be present in any of these products or in the placebo formulation
• other protocol defined exclusion criteria may apply