Targeting CD137L to MC1R-Expressing Melanoma Cells and Tumors.

DESCRIPTION provided by applicant There are specific high affinity ligands for receptors found on many cancers that have been investigated as imaging probes and we believe that we should try to enhance immunotherapy by using these ligands to deliver immune effectors to the cancer microenvironment Melanoma is among the most immunogenic tumors known and so that disease is an excellent test bed for this new strategy The melanocortin receptor ligand MC RL is a sub nM Ki binder of the melanocortin receptor that is found at high levels on the surface of melanoma cells and tumors Herein we propose to make MC RL conjugates with CD L an important T cell costimulator to determine if the conjugate will home to the melanoma microenvironment and enhance the immune response Our Specific Aims are Aim a Synthesize the MC R specific ligand MC RL connected via a trifunctional linker to IRDye and to an amine reactive site for coupling with primary amines on the surface of the commercially available murine recombinant CD L We will characterize the precursors and the final conjugates using LC MS and MALDI TOF MS experiments The binding and the timing of uptake of the MC RL conjugated to IRDye with and without the CD L conjugate with MC R positive murine B F and MC R siRNA knock down B F cells using in vitro fluorescence microscopy studies will verify MC RL binding affinity and specificity Those same cell lines will be used for in vitro immune activation assays Aim b Perform PK studies to determine the half life of optimized conjugates from Aim a in non tumor and tumor bearing in C BL mice It is important to have these studies performed to help determine optimal dose time intervals If we overdose due to all of the available MC R being nearly saturated we will probably increase the chances of systemic toxicity Aim c Show targeted tumor uptake and retention of the MC RL IRDye CD L developed in Aim a in C BL mice bearing B F melanoma xenograft tumors and measure the tumor uptake and systemic clearance rates of these conjugates to predict the overall exposure of the tumor bearing animals Aim d Measure the in vivo activity of MC RL IRDye CD L in the animal models used above to obtain a statistically significant tumor growth reduction relative to untreated animals and determine if doses are tolerated and remain efficacy in immune competent murine models PUBLIC HEALTH RELEVANCE This application will develop an invention for targeting immunotherapy to the surface of melanoma cells and tumors that display a peptide receptor on the surface of melanoma cells Immunotherapy can cure melanoma in a small number of metastatic melanoma patients and we believe that by targeting the immunotherapy to the melanoma rather treating systematically will decrease adverse immune reactions outside of tumor and allow more patients to be cured