Abstract 4229: An innovative human platform for targeted delivery of bispecific interleukins to tumors

Combination approaches using stimulatory cytokines, checkpoint inhibitors, chemotherapy and/or radiation therapy are known to improve overall survival of cancer patients. Recombinant interleukins (IL) have had limited clinical success due to short pharmacokinetics, inefficient tumor targeting and more frequent dosing, leading to toxicities. To address these issues, we have developed a novel platform that delivers immunomodulators in either a mono- or bispecific format. The platform consists of a fully human, albumin-binding scFv domain (FHAB) that provides an improved pharmacokinetic profile, enhanced tumor targeting by binding over-expressed FcRn, GP60 and SPARC, a dose-sparing effect that further decreases the toxicity risk, and a broader therapeutic index. Interleukin-12, IL-15, and IL-18 are among the most potent inducers of anti-tumor activity and have been evaluated in numerous clinical studies. Sonnet's bispecific drug candidates are constructed with IL-12 on the FHAB platform, and include IL12-FHAB-IL15, GMcsf-FHAB-IL12, and IL18-FHAB-IL12. These bispecific molecules span a broad range of mechanisms of action that bridge innate and adaptive tumor immunity. They are produced in Chinese Hamster Ovary cells using an intensified perfusion manufacturing process that allows for rapid scale-up for commercial manufacturing. The “cold” immunosuppressive B16-F10 melanoma tumor model was used for comparing the efficacy of the bispecific candidates administered in a single i.v. dose. All three constructs showed statistically significant tumor size reduction compared to placebo or native interleukin at a 5µg dose: 67% for IL12-FHAB-IL15, 37% for GMcsf-FHAB-IL12 and 76% for IL18-FHAB-IL12. At lower dose levels with nearly equivalent efficacy, mice showed no body weight loss and exhibited reduced toxicity with transient adverse reactions that resolved by Day 8. Optimal synergistic efficacy occurred with the IL18-FHAB-IL12 bispecific. Interestingly, IL-18 upregulates the IL-12 receptor and vice versa. Further, IL-18 also increased levels of chemokines CXCL9 and CXCL10, which in turn resulted in significant increases in activated NK, NKT, Th1, and cytotoxic CD8 T cells, as well as an increase in M1 and decrease in M2 cells in the tumor vs. the spleen. This data points to the potential for changing immunologically “cold” tumors to clinically responsive “hot” ones. In conclusion, these studies demonstrated that while the powerful anti-tumor effects of IL-12 are evide