Precision Targeting of CD1-Restricted iNKT Cells for Cancer Immunotherapy

The invariant Natural Killer T cells (iNKT cells) comprise a well-defined subset of unconventional, innate-like lymphocytes that are important effector and regulatory cells in both humans and mouse models. Unlike conventional T cells, iNKT cells express T cell antigen receptors of limited diversity and respond mainly to foreign and self-glycolipid antigens presented by the MHC class I-like CD1d protein. Activities of iNKT cells include tumor immunosurveillance and induction of tumor regression, strongly implying the potential for iNKT cell-directed therapies for cancer. Synthetic glycolipid antigens that potently activate iNKT cells, such as synthetic α-galactosyl ceramides, have attracted considerable attention as potential anti-tumor agents. However, progress in development of effective iNKT cell directed therapies has been hindered by issues related to toxicities and off-target effects, and is complicated by the fact that glycolipids are taken up and presented by a variety of different cell types to generate complex and unpredictable outcomes. Furthermore, the development of long-term unresponsiveness (anergy) and depletion of iNKT cells by multiple exposures to strong activators like α-galactosyl ceramides makes repeated administration ineffective. Approaches to activating iNKT cells that circumvent these obstacles are needed to exploit the potential of these cells for cancer immunotherapy. The goal of the current proposal is to address these key issues and accelerate the movement of iNKT cell-directed immunotherapy for cancer towards clinical translation. Three specific aims are proposed that will build on our extensive background work that has identified covalently stabilized soluble αGalCer-CD1d conjugates as iNKT cell activators for generating targeted anti-tumor effects without causing iNKT cell anergy or off target toxicity. This approach will be combined with other modalities to improve the anti-tumor effects of iNKT cell activators, including the incorporation of costimulatory signals and combination with inhibitory immune checkpoint blockade. An extensive body of preliminary work supports our approaches, which will be tested in vivo in relevant mouse models of cancer. The project will benefit enormously from close interactive working relationships with a superb group of collaborators with expertise in synthetic chemistry, protein engineering and the biology of immune checkpoint molecules. The current proposal has direct relevance for clinical translation of basic iNKT cell biology into immunotherapeutics, and will accelerate development of iNKT cell directed therapies for cancers that are unresponsive to currently available treatment.