Vaccine adjuvant activity of 3M-052: an imidazoquinoline designed for local activity without systemic cytokine induction.

The human Toll-like receptors (TLRs) are a family of receptors, which sense the presence of various structural elements of pathogens and damaged or effete components in the host. As they do so, they activate two critical arms of host defense, the rapid innate immune response and an adaptive immune response. The innate immune response is typified by the generation of Th1 cytokines, chemokines and type 1 interferons. As such, agonists for the TLRs have potential as antiviral and anticancer therapeutics. They are also well suited to function as vaccine adjuvants. 3M imidazoquinoline (IRM) molecules were the first synthetic small molecules identified as TLR agonists and can affect their biological activities through TLR7, TLR8, or both. The breadth of therapeutic opportunities for this family of molecules can require formulations tailored to the specific application. One consideration is specific formulations to avoid a systemic distribution of these TLR agonists and resulting cytokine storm-like effects on the host. 3M-052 is an IRM bearing a C18 lipid moiety and designed for slow dissemination from the site of application. In the present study 3M-052 has been evaluated for its in vitro TLR activity and for its efficacy as a vaccine adjuvant using a recombinant hemagglutinin from H1N1 A/Puerto Rico/8/34. Given subcutaneously, 3M-052 drives a strong Th1 response to hemagglutinin and serum neutralization of viable H1N1 A/Puerto Rico/8/34 virus in the absence of circulating TNFα or the induction of Th1 cytokines.