Key Inclusion Criteria:  Dose escalation part:  • Participants must have histologically or cytologically confirmed solid tumor(s) in any of the following selected indications for which there is no further available standard therapy likely to confer clinical benefit (or participant is not a candidate or has previously refused such earlier available therapy), and for whom, in the opinion of the investigator, experimental therapy with GEN1047 may be beneficial (breast cancer, uterine cancer, ovarian cancer, NSCLC, cervical cancer, HNSCC except for nasopharyngeal carcinoma, urothelial cancer, CCA).  Expansion part:  • Participant must have an advanced or metastatic, pathologically confirmed diagnosis of one of the following tumors for which there is no further available standard therapy likely to confer clinical benefit (or participant is not a candidate or has previously refused such available therapy), and for whom, in the opinion of the investigator, experimental therapy with GEN1047 may be beneficial (breast cancer, uterine cancer, ovarian cancer, NSCLC, cervical cancer, HNSCC except for nasopharyngeal carcinoma, urothelial cancer, CCA). For all indications: Participants may have received up to 4 prior systemic treatment regimens for advanced/metastatic disease (maintenance treatment is considered being part of 1 treatment line).  Both, dose escalation and expansion part:  Participant must sign and ICF, prior to any screening procedures  Participants with ovarian cancer:  Must have documented progressive disease. CA-125 positivity according to the Gynecologic Cancer Intergroup Guideline (GCIG) with a pretreatment sample that is at least twice the upper limit of the reference range. Either recurrence after, or progression on or lack of response to established standard of care (SOC) anticancer therapies; or are deemed intolerant to or ineligible for, standard curative therapy in the recurrent setting. At least 1 measurable lesion per RECIST v1.1. The measurable lesion(s) must be outside the field of radiation therapy (RT) if there was prior treatment with RT. Eastern Cooperative Oncology Group performance status (ECOG-PS) score of 0 to 1 Should provide a tumor tissue sample during the Screening period and prior to C1D1. Must have acceptable laboratory parameters as specified in the protocol  Key Exclusion Criteria (dose escalation and expansion part):  Exclusions related to cardiovascular disease  Symptomatic congestive heart failure (grade III or IV as classified by the New York Heart Association), unstable angina pectoris or cardiac arrhythmia. History of myocardial infarction within 6 months prior to planned start of GEN1047. Uncontrolled hypertension defined as systolic blood pressure ≥160 mmHg and/or diastolic blood pressure ≥100 mmHg, despite optimal medical management. Prolonged QTc interval >480 milliseconds using Fridericia's QT correction formula. Any other cardiac disease(s) not listed that, in the opinion of the investigator, is/are clinically significant and/or unacceptable.  Exclusions related to the central nervous system  Participant has any history of intracerebral arteriovenous malformation, cerebral aneurysm, new (within the last 6 months) or symptomatic brain metastases, spinal cord compression (from disease), or stroke. (Transient ischemic attack >1 month prior to Screening is allowed.) Participants with known unstable CNS metastases and any active or history of carcinomatous meningitis will be excluded. Participants with previously treated brain metastases may participate provided they are radiologically stable (ie, without evidence of progression) for at least 28 days by repeat imaging prior to C1D1. Participants should be clinically stable and should not be undergoing steroid taper or have received stereotactic radiation or whole-brain radiation within 14 days prior to C1D1. Chronic steroid therapy is acceptable provided that the dose is stable for the last 14 days prior to C1D1 (≤10 mg prednisone daily or equivalent, corresponding to a maximum administration exposure of ≤140 mg within 14 days). A participant with new or progressive brain metastases. Spinal cord metastasis is acceptable. However, participants with spinal cord compression should be excluded.  Participant has been exposed to any of the following prior therapies within the specified timeframes:  Radiotherapy: Radiotherapy within 14 days prior to first GEN1047 administration. Palliative radiotherapy will be allowed. The use of RANK-L inhibitors and bisphosphonates (if on stable dose for at least 4 weeks) is permitted while participating in this trial. However, the initiation of growth factors and bisphosphonates is not allowed during the first 4 weeks of GEN1047 administration, unless agreed upon by the investigator and sponsor medical monitor. Treatment with any investigational or non-investigational anticancer agent (including investigational vaccines) or used an invasive investigational medical device within 28 days or 5 half-lives, whichever is shorter, before the planned first dose of GEN1047 or is currently enrolled in an interventional trial. Prophylaxis with live, attenuated vaccines within 28 days prior to first dose of GEN1047; or prophylaxis with the first and/or subsequent injection(s) of SARS-CoV-2 nucleic acid vaccine within 28 days prior to first dose of GEN1047. Chronic systemic immunosuppressive corticosteroid doses, ie, prednisone >10 mg daily (or equivalent) or a cumulative dose >140 mg prednisone within 14 days (or equivalent) before the first GEN1047 administration. Replacement therapy (eg, thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency) is not considered a form of systemic treatment and is permitted. Has received granulocyte colony-stimulating factor (G-CSF) or granulocyte/macrophage colony stimulating factor support within 2 weeks prior to the first GEN1047 administration or being chronically transfusion dependent. Any prior therapy with an antibody targeting CD3 or other T cell activating surface marker. Toxicities from previous anticancer therapies that have not resolved to baseline levels or to ≤ grade 1, except for alopecia, anorexia, vitiligo, fatigue, hyperthyroidism, hypothyroidism, and peripheral neuropathy. Anorexia, hyperthyroidism, hypothyroidism, and peripheral neuropathy must have recovered to ≤ grade 2. Has ongoing or active infection requiring IV treatment with anti-infective therapy that has been administered <2 weeks prior to first dose. Has a history of non-infectious pneumonitis that has required steroids, or currently has any grade of pneumonitis. Has a serious, non-healing wound, or skin ulcer (of any grade). Has a history of organ allograft (except for corneal transplant) Autologous or allogeneic bone marrow transplant, or stem cell rescue within 3 months prior to the first GEN1047 administration. Chimeric antigen receptor (CAR)-T cell therapy within 30 days prior to first GEN1047 administration.  Has a known past or current malignancy other than inclusion diagnosis, except for:  Cervical carcinoma of Stage 1B or less. Non-invasive basal cell or squamous cell skin carcinoma. Non-invasive, superficial bladder cancer. Prostate cancer with a current PSA level <0.1 ng/mL. Any curable cancer with a complete response of >2 years duration. A history of ≥ grade 3 allergic reactions to antibody therapy or has known allergies, hypersensitivity, or intolerance to GEN1047 or its excipients. A history of ≥ grade 3 cytokine release syndrome or ≥ grade 3 immune effector cell-associated neurotoxicity syndrome to antibody therapy, CAR-T cell therapy, or other immune effector cell therapy  NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.