CAR-macrophages for the Treatment of HER2 Overexpressing Solid Tumors

Inclusion Criteria: * HER2-positive recurrent or metastatic solid tumors for which there are no available curative treatment options. * Breast cancer and gastric/gastroesophageal junction cancers must have failed approved HER2-targeted agents. * Other HER2-positive tumor types must have failed standard of care therapies, while prior therapy with anti-HER2 drugs is not required. * Subject must be willing and able to undergo tumor tissue biopsy procedures * Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1 * Subject has adequate bone marrow and organ function Exclusion Criteria: * HIV, active hepatitis B or hepatitis C infection. * Diagnosis of immunodeficiency or chronic exposure to systemic corticosteroid therapy or any other form of immunosuppressive therapy * Untreated or symptomatic central nervous system (CNS) metastases or cytology proven carcinomatous meningitis. o Subjects with small, asymptomatic CNS metastases that do not require treatment are permitted to enroll. * Left ventricular ejection fraction (LVEF) \<50% as determined by ECHO or multiple gated acquisition scan (MUGA) Other protocol-defined Inclusion/Exclusion may apply. CT-0508 in Combination with Pembrolizumab Substudy Only: Exclusion Criteria: * Subjects with severe hypersensitivity (≥Grade 3) to pembrolizumab and/or any of its excipients * Subjects with an active autoimmune disease that has required systemic treatment in past 2 years (i.e., with use of disease modifying agents, corticosteroids or immunosuppressive drugs). * Subjects who have a history of (non-infectious) pneumonitis/interstitial lung disease that required steroids or has current pneumonitis/interstitial lung disease * Subjects who have had an allogeneic tissue/solid organ transplant