Trial to Assess the Safety and Antitumor Activity of GEN1057 in Malignant Solid Tumors

Key Inclusion Criteria: * Advanced and/or metastatic malignant solid tumors, who have progressed on standard of care therapy for whom there is no available standard therapy likely to provide clinical benefit, or who are not candidates for available therapy, and for whom experimental therapy with GEN1057 may be beneficial, in the opinion of the investigator. * Be at least 18 (or the legal age of consent in the jurisdiction in which the trial is taking place) years of age. * Have measurable disease according to RECIST v1.1. * Have Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 to 1 at screening and on C1D1 pretreatment. Note: If screening ECOG PS is assessed within 3 days prior to C1D1, ECOG PS does not need to be reassessed at C1D1. * Have a life expectancy of ≥3 months. Key Exclusion Criteria: * Has been exposed to any of the following prior therapies/treatments within the specified timeframes: * Treatment with an investigational anticancer agent within 28 days or for systemic therapies within 5 half-lives of the drug, whichever is shorter, prior to trial treatment administration. * Treatment with an investigational drug, including investigational vaccines within 28 days before the planned first dose of trial treatment. * Prior treatment with live, attenuated vaccines within 28 days prior to initiation of GEN1057. Examples of live vaccines include, but are not limited to, the following: measles, mumps, rubella, varicella/zoster (chicken pox), yellow fever, rabies, Bacillus Calmette-Guérin, and typhoid vaccine. Seasonal influenza vaccines for injection are generally killed virus vaccines and are allowed; however, intranasal influenza vaccines (eg, FluMist®) are live, attenuated vaccines and are not allowed. Experimental and/or nonauthorized severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccinations are not allowed. * Used an invasive investigational medical device within 28 days before the planned first dose of trial treatment. * Has clinically significant toxicities from previous anticancer therapies that have not resolved to baseline levels or to grade 1, except for anorexia, hyperthyroidism, hypothyroidism, and peripheral neuropathy, which must have recovered to ≤ grade 2. There is no limitation for alopecia and hearing impairment from previous therapies. * Has known, symptomatic brain metastases. Asymptomatic brain metastases are allowed provided that they have been treated, have been stable for \>28 days as documented by radiographic imaging, and do not require prolonged (\>14 days) systemic corticosteroid therapy. * Has a past or current malignancy other than inclusion diagnosis. Note: Other protocol-defined inclusion and exclusion criteria may apply.