Immunotherapy-specialist Hookipa Pharma (NSDQ:HOOK) has announced a clinical collaboration and supply agreement with Merck (NYSE:MRK). Hookipa will test its immunotherapeutic HB-200 in conjunction with Merck’s blockbuster anti-PD-1 therapy, Keytruda (pembrolizumab), as first-line treatment for patients with advanced head and neck squamous cell carcinoma (HNSCC). Last year, Merck raked in $14.5 billion in sales revenue from Keytruda.…