Safety and Activity Study of HER2-Targeted Dual Switch CAR-T Cells (BPX-603) in Subjects With HER2-Positive Solid Tumors

Inclusion Criteria: * Documented evidence of HER2 amplification/overexpression by local testing. * Histologically or cytologically confirmed diagnosis of a locally advanced unresectable or metastatic HER2+ solid tumor malignancy for which standard treatment is no longer effective, does not exist, or subject is ineligible. * Subjects with a solid tumor malignancy for which HER2-targeted therapy is approved as a standard treatment (e.g., breast, gastric cancers) must have received prior treatment with approved HER2-directed therapy. * Measurable disease (at least one target lesion) per RECIST v1.1. * Life expectancy \> 12 weeks. * ECOG 0-1. * Adequate organ function. Exclusion Criteria: * Symptomatic, untreated, or actively progressing central nervous system metastases. * Prior CAR T cell or other genetically-modified T cell therapy. * Impaired cardiac function or clinically significant cardiac disease. * Symptomatic intrinsic lung disease or those with extensive tumor involvement of the lungs. * Severe intercurrent infection. * Pregnant or breastfeeding. * Known HIV positivity.