MCLA-158-CL02

This study aims to compare the ability of petosemtamab to destroy tumors or prevent their growth (anticancer activity), as well as its safety profile, compared to the standard medical treatment (standard treatment), in order to determine which is more effective for treating head and neck cancer.;3. Primary and Secondary Endpoints of the Trial;The primary endpoints of the study (the indicators that will be measured to assess whether the main objectives of the study have been achieved) are as follows:;The percentage of participants whose tumor decreases or disappears (referred to as the Objective Response Rate or ORR) after treatment with petosemtamab, compared to the ORR after treatment with standard treatment.;The duration for which participants remain alive from the start of treatment with petosemtamab (referred to as Overall Survival or OS) compared to OS in participants receiving standard treatment.;The secondary endpoints are as follows:;The anticancer activity of petosemtamab, measured as follows:;The ORR in participants receiving petosemtamab.;Duration of Response (DoR): the time from the start of participation until disease progression or death in participants who achieve a complete response (no signs of cancer on imaging or tests) or a partial response (the tumor has decreased by at least one-third [30%] and there is no sign that the cancer has spread elsewhere in the body) after receiving petosemtamab.;Time to Response (TTR): the time from the start of treatment until the first response (reduction in tumor size, or extent of cancer in the body).;Clinical Benefit Rate (CBR): the percentage of participants whose cancer has regressed or has not worsened for at least 6 months after receiving petosemtamab.;The occurrence of adverse events that were not present before treatment with petosemtamab, or an event that was already present whose intensity or frequency worsened following treatment with petosemtamab (also called Treatment Emergent Adverse Events or TEAEs).;The quality of life of participants, measured by changes in their responses to two questionnaires called EORTC QLQ-C30 and QLQ-H&N43, before and after receiving petosemtamab.;The amounts of petosemtamab in participants' blood.;The quantity of antibodies against petosemtamab in participants' blood.