Evaluation of Safety, Tolerability, PK & PD of Intravenous VX15/2503 in Patients With Advanced Solid Tumors

Main Inclusion Criteria: * Patients 18 yrs or older with confirmed histological or cytological advanced solid tumors, relapsed or refractory to standard treatment for which no curative therapy is available; patients must demonstrate progressive disease prior to entry * Has measurable disease as defined by RECIST1.1 * Life expectancy of at least 3 months (per investigator assessment) * ECOG performance status of 0-2 * Adequate bone marrow, renal and liver function * Recovered from any significant prior toxicity of previous anti-neoplastic therapy * For patients of reproductive potential, is willing to use a medically acceptable form of contraception throughout the study period and for at least 4 weeks after the last dose of VX15/2503 * Expansion cohort - patients in this cohort must have one of the following characteristics: * A diagnosis of a pancreatic neuroendocrine tumor OR * A diagnosis of a soft tissue sarcoma OR * A diagnosis of a bone metastasis OR * A diagnosis of advanced solid tumor AND a T cell count of at least 1500 cells/uL OR a B cell count of at least 250 cells/uL at screening Main Exclusion Criteria: * Treatment with anti-neoplastic agents (chemotherapy, immunotherapy, radiotherapy or endocrine therapy) within 3 weeks prior to start of study treatment * Treatment with an investigational agent within 4 weeks prior to start of study treatment * Is on concurrent anti-neoplastic therapy with the exception of continuing luteinizing hormone-releasing hormone agonist/antagonist therapy for patients with castrate-resistant prostate cancer * Treatment with oral or parenteral corticosteroids in excess of 10mg/day of prednisolone or equivalent for more than 5 days within 4 weeks prior to start of study treatment or a requirement for systemic immunosuppressive therapy for any reason * Untreated brain Mets or CNS tumor involvement * Any other intercurrent illness or condition which could impact patient compliance or ability to complete the study * Sensitivity to VX15/2503 or the ingredients or excipients of VX15/2503 * Pregnant or breast-feeding women (women of child-bearing potential must have negative serum pregnancy test within 3 days prior to receiving the first dose of VX15/2503)