A Study of SEA-CD40 Given With Other Drugs in Cancers

Inclusion Criteria: * Histologically or cytologically confirmed unresectable malignancy defined as one of the following: * Cohort 1: Relapsed and/or refractory metastatic melanoma * Uveal/ocular melanoma is excluded * Must have progressed on treatment with an anti-PD-(L)1 mAb. PD-(L)1 treatment progression is defined as meeting all of the following criteria: * Has received at least 2 doses of an approved anti-PD-(L)1 mAb * Has demonstrated disease progression after PD-(L)1 as defined by RECIST v1.1. * Progressive disease has been documented within 12 weeks from the last dose of anti- PD-(L)1 mAb * Last dose of anti-PD-(L)1 must have been within 90 days prior to enrollment * Participants with a targetable BRAF mutation must have been treated with, been intolerant of, or declined treatment with BRAF/MEK targeted therapy prior to study entry * Cohort 2: Metastatic uveal melanoma * Must not have received prior treatment for advanced or metastatic disease except for prior adjuvant/neoadjuvant immunotherapy * No prior liver-directed therapy * Cohort 3: Metastatic PD-(L)1-naive melanoma * Uveal/ocular melanoma is excluded * Must not have received prior treatment for advanced or metastatic disease except for prior adjuvant/neoadjuvant immunotherapy. * For participants with a targetable BRAF mutation, prior BRAF/MEK targeted therapy is allowed if completed 4 weeks prior to first dose of study treatment. * Cohorts 4 and 5: Non-squamous NSCLC * Participants must have stage IV disease per AJCC 8th edition * No known driver mutations/alterations mutation for which targeted therapy is available * Must have non-squamous histology. * No prior therapy for metastatic disease * No prior treatment with anti-PD-(L)1 or PD-L2 agent or an antibody targeting other immuno-regulatory receptors or mechanisms * Able to provide archival tumor tissue from locations not radiated prior to biopsy. If archival tumor sample is not available a fresh baseline biopsy is required. * 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 of first dose of study drug * Active central nervous system (CNS) metastases and/or carcinomatous meningitis. * Previous exposure to CD40-targeted therapy * Currently on chronic systemic steroids in excess of physiologic replacement * Has had an allogeneic tissue/solid organ transplant. * History of autoimmune disease that has required systemic treatment in the past 2 years