GSK2245035, a TLR7 agonist, Does Not Increase Pregnancy Loss in Cynomolgus Monkeys.

GSK2245035, a small molecule Toll-like Receptor 7 (TLR7) agonist developed for immunomodulatory treatment for allergic airways disease, aimed to reduce Th2 and enhance Th1/Treg responses to aeroallergens via the local induction of type I interferons (IFNs). GSK2245035 demonstrated selectivity for potent release of type I IFNs compared to TNF-α and IL-6, with dose dependent increases in the interferon inducible chemokine, IP-10, in the nasal compartment. Implantation and parturition require pro-inflammatory processes including IFNs, Interferon Stimulated Genes, TNFα and IP-10 while pregnancy requires immune regulation to maintain maternal fetal immune tolerance, and recombinant type I IFNs induced abortions in monkeys. Due to its mechanism of action, GSK2245035 was studied at pharmacologically and clinically relevant doses in a monkey pregnancy model. Monkeys received 0, 3 or 30 ng/kg/week GSK2245035 intranasally once weekly, from Day 20 postcoitum through Day 63 postpartum. Although systemic IFN-α and IP-10 levels were approximately 14.8 or 40 -fold (respectively) above predose levels at 3 or 30 ng/kg/week, respectively, there were no effects on pregnancy and infant outcome. Non-adverse effects included increased incidence of nasal discharge, increased maternal body temperature at 30 ng/kg/week and dose-dependent increases in maternal IP-10 and IFN-α and decreased infant anti-KLH IgM and IgG titers following KLH immunization at ≥3 ng/kg/week, relative to controls. Potentially, lower IFN-α and IP-10 levels as well as once-weekly intranasal dosing vs daily subcutaneous or intramuscular dosing with recombinant type I IFNs could explain the lack of pregnancy effects; however, there was an undesired impact on offspring immune function.