INCLUSION CRITERIA - For Parts 1-4:

* Histologically confirmed diagnosis of a locally advanced (not amenable to curative therapy such as surgical resection) or metastatic solid tumors
* Life expectancy > 12 weeks
* Patients must not have received prior interleukin-2 (IL-2) therapy
* Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1
* Measurable disease per RECIST 1.1
* Patients with stable brain metastases under certain criteria
* Fresh and archival tumor tissue available Tumor specific inclusion criteria may apply.

EXCLUSION CRITERIA - For Parts 1-4:

* Use of an investigational agent or an investigational device within 28 days before administration of first dose of NKTR--214
* Females who are pregnant or breastfeeding
* Participants who have an active autoimmune disease requiring systemic treatment within the past 3 months or have a documented history of clinically severe autoimmune disease that requires systemic steroids or immunosuppressive agents
* History of organ transplant that requires use of immune suppressive agents
* Active malignancy not related to the current diagnosed malignancy
* Evidence of clinically significant interstitial lung disease or active, noninfectious pneumonitis
* Participants who have had < 28 days since the last chemotherapy, biological therapy, or < 14 days from approved tyrosine kinase inhibitor (TKI) therapy, or systemic or inhaled steroid therapy at doses greater than 10mg of prednisone Tumor specific exclusion criteria may apply.

Other protocol defined inclusion/exclusion criteria may apply