A Study of AB801 Monotherapy and Combination Therapy in Participants With Advanced Malignancies

Key Inclusion Criteria: * Monotherapy-specific criteria for dose escalation cohorts: * Participants may have cytologically or pathologically confirmed non-small cell lung carcinoma (NSCLC), colorectal carcinoma (CRC), breast, ovarian, renal cell carcinoma (RCC), head and neck squamous cell carcinoma (HNSCC), or bladder (including urothelial malignancies of the renal pelvis and ureter) carcinoma that has progressed or was non-responsive to available therapies with no standard of care (SOC) options, or for whom standard therapy has proven ineffective, intolerable, or considered inappropriate; or for whom a clinical study of an investigational agent is a recognized SOC. * Disease-specific criteria for dose-expansion (NSCLC): * Cytologically or pathologically confirmed locally advanced unresectable or metastatic (Stage IIIB-IV per American Joint Committee on Cancer version 8) non-squamous NSCLC negative for actionable mutations in EGFR, ALK, ROS1, NTRK, C-MET, or RET. Mixed SCLC and squamous NSCLC histology is not permitted. * Previously treated in the unresectable locally advanced or metastatic setting with a platinum-containing chemotherapy and PD-(L)-1inhibitor. * Must have at least 1 measurable lesion per Response Evaluation Criteria in Solid Tumors (RECIST) guidance (Version 1.1) (Section 1.1). The measurable lesion must be outside of a radiation field if the participant received prior radiation unless discussed and approved by the study physician. * Eastern Coopera…