Selected Inclusion Criteria  In dose-escalation (Phase 1a), patients must have selected tumor types and must have progressed after standard of care treatment, or be intolerant to treatment, or refused standard treatment Available archived tumor tissue sample. In the setting where archival material is unavailable or unsuitable for use, the patient must consent and undergo fresh tumor biopsy. In some patients, a new pre-treatment and on-treatment tumor biopsy may be required. Patients with central nervous system (CNS) metastases must have been treated and be asymptomatic.  Selected Exclusion Criteria:  Received systemic anti-cancer therapy within 3 weeks of the first dose of study treatment or small molecule kinase inhibitors within 6 elimination half-lives of the first dose of study treatment. Received definitive radiotherapy within 2 weeks of the first dose of study treatment; or palliative radiotherapy (< 2 weeks of radiotherapy to non-central nervous system [CNS] disease) within 1 week of the first dose of study treatment. Received prior IL-2-based or IL-15-based cytokine therapy