Combined AlloStim+Anti-PD-L1 in 4L MSS Metastatic Colorectal Cancer

The protocol provides fourth-line experimental treatment for subjects with microsatellite stable (MSS)/ proficient mismatch repair (pMMR) metastatic colorectal cancer. These patients do not respond to checkpoint inhibitors. This study will investigate whether AlloStim® administered weekly in two-21 day cycles with each cycle consisting of 3 weekly intradermal (ID) doses followed the last week with an intravenous (IV) dose (3 cycles =Days 0 through 49) can prime patients to become responsive to checkpoint inhibition immunotherapy. A restaging computed tomography (CT) scan is conducted on day 56 after the priming and will be compared to the baseline CT scan by Response Evaluation Criteria in Solid Tumors (RECIST 1.1). Scans at day 56 are expected to be read as radiological progression upon restaging after AlloStim® priming, possibly due to immunological swelling, known as "pseudoprogression", consistent with the presumed inflammatory mechanism of action of AlloStim®. This mechanism may convert "cold" tumors to "hot" tumors. The immune cell infiltrates of tumors after AlloStim® include T-helper cell type 1 (Th1) memory cells which produce interferon-gamma. Interferon-gamma is known to increase expression of anti-programmed death ligand 1 (PD-L1) checkpoint molecules in the tumor microenvironment. Higher PD-L1 expression may convert checkpoint inhibitor unresponsive tumors to become checkpoint inhibitor responsive. After two 21-day cycles of AlloStim® priming, a combination of AlloStim® IV boosters and anti-PD-L1 checkpoint therapy (with avelumab 800 mg q/2 weeks) is scheduled between days 63 to day 98, A restaging CT scan at day 112 is then compared to day 56 and baseline to determine if the tumor target lesions\' size has changed. An expansion phase providing another cycle of combined AlloStim® and avelumab is provided for stable patients from days 119-154. A final restaging CT scan is conducted on Day 168 for all subjects.