AMP-224, a PD-1 Inhibitor, With Stereotactic Body Radiation Therapy in Metastatic Colorectal Cancer

Background: * Colorectal cancer remains the second leading cause of cancer death in western countries with a median survival of approximately 24 months despite recent advances in systemic treatment. * Several preclinical studies have documented an increase in peripheral antitumor immunity following radiation, a phenomenon known as the abscopal effect. Tumor PDL1 expression has also been shown to be induced by radiation, which can suppress the anti-tumor immune response. Inhibition of programmed cell death-1 (PD-1)/programmed death ligand-1(PDL-1) axis has been shown to improve anti-tumor immunity by blocking the tumor-mediated suppression of cytotoxic T cells. * AMP-224, a B7-DC Fc fusion protein, binds to PD-1, an inhibitory receptor that is present on the cell surface of exhausted, activated, effector, and memory T cells. AMP- 224 has a unique mechanism of action in that it binds specifically to PD-1HI T cells (chronically stimulated / exhausted T cells) but not to PD-1LO cells which represent the normal activated T cells population * The aim of the study is to evaluate whether the anti-tumor immunity of anti-PD1 therapy (with AMP-224) can be enhanced by radiation therapy. Objectives: \- To assess safety, tolerability and feasibility of AMP-224 in combination with stereotactic body radiation therapy (SBRT) in patients with metastatic colorectal cancer. Eligibility: * Histologically confirmed metastatic colorectal cancer. * Patient must have progressed on or been intolerant of prior oxaliplatin- and irinotecan containing regimen and have metastatic lesions that are not amenable to curative resection. * Patient must have one focus of metastatic disease in the liver that is amenable to SBRT. * Patient must have at least one measurable metastatic lesion by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria outside the radiation field. * Patients must be willing to undergo mandatory pre and post treatment tumor biopsy. Design: * This is a pilot study whereby all patients will receive SBRT to one liver lesion and concomitant AMP-224. A single treatment of low dose/cyclophosphamide will be administered in conjunction with the SBRT therapy prior to the first AMP-224 treatment. * Hypofractionated radiation will be administered to a metastatic disease site at a dose and schedule of 8Gy for 1 or 3 days in dose levels (DL)1 or 2 respectively. The day of first administration of AMP-224 will be designated as Day 1. In DL1 the SBRT will be administered on Day 0. In DL2 the SBRT will be administered from D-2 to D0. The study will begin with DL1 and escalate to DL2 once all subjects enrolled at DL1 have remained on study for 4 weeks, which is the DLT period. * AMP-224 therapy will be given as an intravenous infusion beginning on Day 1 and then every 14 days for a total of 6 treatments only. Optional continuation of treatment q2- weekly until progressive disease (PD) will be considered in responding patients. * Cyclophosphamide 200 mg/m(2) intravenous will be given on Day 0, prior to the first dose of AMP-224. * Correlative studies: Peripheral blood will be collected (pre-dose) on days 1, 29, 57 and 93 for immune studies (including immunogenicity, circulating PD plasma samples, immune monitoring for phenotyping and peripheral blood mononuclear cells (PBMC) for T-cell activation). Tumor biopsies (formalin-fixed paraffin-embedded (FFPE) + Frozen) of an irradiated and non-irradiated liver lesion will be collected on day 1 and day 29, which will be analyzed by immunohistochemistry for tumor-infiltrating lymphocytes in addition to ribonucleic acid (RNA) analysis. * Pharmacokinetic (PK) samples will be collected on Days 1, 15, 29, 43, 57, 71 in addition to up to 5 post treatment dates (if feasible).