A first in class VIP receptor antagonist as an immunotherapeutic for acute myeloid leukemia

Current immune checkpoint therapies targeting PD-1 and PD-L1 are ineffective in treating Acute Myeloid Leukemia (AML). Vasoactive Intestinal Peptide (VIP) is an immunosuppressive 28-amino acid neuropeptide overexpressed in nearly 30% AML patients, suggesting that some AML tumors may be using VIP expression as a mechanism to evade immune surveillance. We hypothesize that AML cells secrete VIP which signals through the VIP-R (receptor) on T cells to limit anti-cancer immunity. Therefore, targeting the VIP signaling with a VIP-R antagonist can reverse immunosuppression and potentiate anti-cancer immunity. Using in silico modeling, in vitro screening for potentiation of T cell activation, and proof-of-principle screening in mouse leukemia models, we identified a novel VIP-R antagonist, ANT308. ANT308 shows stronger binding affinity to VIP-R as compared to VIP and potentiates activation of human and mouse T cells with an EC 50 in the range of 200-400 nM. Immunofluorescence assays show that ANT308 colocalizes with the VIP receptor, VPAC1. Co-IP and flow cytometry confirmed ANT308 binding to VPAC1. In addition, ANT308 treatment of leukemic mice induced strong T cell-mediated anti-leukemic activity. To improve the pharmacokinetics of ANT308, we have developed a novel fusion peptide combining ANT308 and Fc fragment of IgG4 named CAMV-01. In a Jurkat T-cell activation assay, CAMV-01 has an EC 50 of 100-200 nM and reduces T cell exhaustion. Furthermore, CAMV-01 significantly improved survival in multiple murine leukemia models, including those that secrete VIP (C1498) and the VIP negative cell line P815. In vitro stability studies show that CAMV-01 remains stable in plasma for > 4 days, whereas the ANT308 peptide is stable for only 15 minutes. PK studies with intravenous (i.v.) or subcutaneous (s.c.) injection of 15mg/kg CAMV-01 show a half-life of 2 weeks in mice, compared to 15 minutes for the ANT308 peptide. Using Sprague-Dawley rats receiving a single i.v. or s.c injection of 5mg/kg CAMV-01, the C max and t 1/2 were estimated to be 82 nM and 165 hours (i.v.) respectively and 0.7 nM and 235 hours (s.c.) respectively. In a P815 mouse model, s.c. administration of CAMV-01 induced a stronger tetramer-positive CD8+ T-cell response compared to ANT308. In conclusion, CAMV-01 is a novel, first-in-class immunotherapeutic targeting the VIP immune checkpoint, with a robust pharmacokinetic and pharmacodynamic profile and promising potential for the treatment of AML.