A Study Investigating agenT-797 in Participants With Relapsed/Refractory Solid Tumors

Inclusion Criteria: * Histological or cytological evidence of relapsed or refractory solid tumor malignancy for which no standard therapy is available or standard therapy has failed * Measurable disease per RECIST 1.1 as assessed by local site Investigator/radiology. Lesions situated in a previously irradiated area are considered measurable if progression has been demonstrated in such lesions * Part 2 only, participants must have progressed per Investigator assessment on pembrolizumab or nivolumab, and agree and are able to continue on the inhibitor(s) while on study * No other medical, surgical, or psychiatric condition (including active substance abuse) that would interfere with compliance to the protocol, as determined by the Principal Investigator Exclusion Criteria: * Concurrent invasive malignancy * Brain and/or leptomeningeal metastases that are untreated or require current therapy * Prior radiotherapy within 2 weeks of start of study treatment