Trial to Assess the Safety and Preliminary Efficacy of GEN1055 on Malignant Solid Tumors as Monotherapy and as Combination Therapy

Protocol summary

The goal of this trial is to learn about the antibody GEN1055 when it is used alone and when it is used together with another antibody cancer drug, pembrolizumab (with or without chemotherapy), for treatment of participants with certain types of cancer. Participants will receive either GEN1055 alone, GEN1055 with pembrolizumab, or GEN1055 with pembrolizumab and chemotherapy. All participants will receive active drug; no one will receive placebo. This trial has 2 parts. The purpose of the first part is to find out if GEN1055 is safe and to find out the doses of GEN1055 to use alone and to use with pembrolizumab. The purpose of the second part is to give GEN1055 to more participants to see how well the doses of GEN1055 that were selected in the first part work against cancer alone and how well they work with pembrolizumab (with or without other chemotherapy). A participant will receive trial treatment up to a maximum of 24 months for pembrolizumab-containing regimens, or until: * the cancer progresses. * there are side effects requiring that treatment be stopped. * the participant decides to not participate further in this trial. * the doctor believes it is in the participant's best interest to stop treatment. Participation in the trial will require visits to the site. For the first 12 weeks there will be weekly visits and after that, visits will be every 3 weeks. At site visits, there will be various tests (such as blood draws) and procedures (such as recording of heart activity, computed tomography (CT) scans) to monitor whether the treatment is safe and effective. The trial duration (including screening, treatment, and follow-up) for each participant will be about 39 months.