In Vivo: Oral administration of RGX-104 (100 mg/kg, daily) to animals bearing palpable tumors significantly suppresses the growth of multiple cancer types. Co-administration of RGX-104 with anti-PD-1 is superior to administration of either RGX-104 or anti-PD-1 alone. Importantly, co-administration of RGX-104 with anti-PD-1 therapy is well tolerated by mice, with no overt signs of toxicity.