A Study of PF-08046049/SGN-BB228 in Advanced Melanoma and Other Solid Tumors

This study will test the safety of a drug called PF-08046049/SGN-BB228 in participants with melanoma and other solid tumors that are hard to treat or have spread through the body. It will also study the side effects of this drug. A side effect is anything a drug does to the body besides treating the disease. This study will have 3 parts. Parts A and B of the study will find out how much PF-08046049/SGN-BB228 should be given to participants. Part C will use the information from Parts A and B to see if PF-08046049/SGN-BB228 is safe and if it works to treat solid tumor cancers.

Inclusion Criteria: * All Parts: Participants must have disease that is relapsed, refractory, or intolerant to standard of care. Participants must have histologically or cytologically confirmed metastatic malignancy. * Participants must have one of the following tumor types: * Parts A and B: Participants must have metastatic or unresectable cutaneous melanoma. * Part C: Participants must have one of the following tumor types: * Cutaneous Melanoma * Non-small Cell Lung Cancer (NSCLC) * Colorectal Cancer (CRC) * Pancreatic Cancer * Mesothelioma * A pre-treatment biopsy or submission of archival tissue is required * For participants with cutaneous melanoma * Must have been previously treated with an anti-programmed death-1 (anti-PD-1) or anti-programmed death ligand-1 (anti-PD-L1) agent given alone or with other therapies. * Participants with a targetable BRAF mutation must have been treated with, been intolerant of, or been deemed ineligible to receive treatment with BRAF/MEK targeted therapy prior to study entry. * Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0 or 1 * Measurable disease per RECIST v1.1 at baseline Exclusion Criteria: * History of another malignancy within 3 years before the first dose of study drug, or any evidence of residual disease from a previously diagnosed malignancy. Exceptions are malignancies with a negligible risk of metastasis or death. * Active central nervous system metastases or leptomeningeal disease. Participants with previously treated brain metastases may participate provided they are: * clinically stable for at least 4 weeks prior to study entry after brain metastasis treatment, * they have no new or enlarging brain metastases, * and are off of corticosteroids prescribed for symptoms associated with brain metastases for at least 7 days prior to the first dose of study drug. * Prior therapies cannot include any drugs targeting CD228 or 4-1BB * Immunotherapy, biologics, and/or other approved or investigational antitumor treatment that is not completed 4 weeks prior to first dose of study drug, or within 2 weeks prior to the first dose of study drug if the underlying disease has progressed on treatment * Melanoma subtypes including acral, uveal, and mucosal are excluded