MCLA-158-CL03: A phase III randomized, open label study to evaluate the efficacy and safety of Petosemtamab plus Pembrolizumab vs. Pembrolizumab in head and neck squamous cell carcinoma in the first line treatment of PD-L1+ (CPS?1) metastatic/recurrent disease without curative therapy available

The purposes of this Study are to find out the possible side effects of the Study Drug, when used in combination with another, already approved, drug named pembrolizumab; if the Study Drug can or cannot stop the progression of your head and neck squamous cell cancer in your body, if it can or cannot improve the possibilities of survival, how the Study Drug plus pembrolizumab versus pembrolizumab alone is processed by your body, if it can improve or not your quality of life related with your disease, and how certain biomarkers or small substances in your body change in response to the Study Drug in combination with pembrolizumab vs. when pembrolizumab is taken alone.