Talactoferrin alfa is an anti-cancer agent with activity in renal cell cancer (RCC) patients and a novel immunomodulatory mechanism of action

Abstract

14648 Background: Talactoferrin alfa (talactoferrin) is a novel, orally administered immunomodulatory protein with demonstrated anti-cancer activity in preclinical experiments. Methods: Talactoferrin’s safety and efficacy in cancer patients was evaluated in a Phase I/II trial. Patients with metastatic disease who had failed standard therapy were treated with single-agent oral talactoferrin. Tumors were measured by CT scan using RECIST criteria. Talactoferrin’s mechanism of action was evaluated in preclinical experiments in tumor-bearing immunocompetent BALB/c and knockout mice. Cytokine levels were measured by ELISA. Cellular changes were measured by FACS analysis and immunofluorescence. Results: Seven patients with metastatic RCC who had failed previous systemic therapy were treated with oral, single-agent talactoferrin. Talactoferrin was safe and very well tolerated without a single drug-related SAE. All seven patients achieved at least Stable Disease, with one patient showing a deep and sustained partial response (71% shrinkage by RECIST two years after start of therapy). There was an apparent increase in median PFS to 7.3 months, with two patients still progression free after two years. Median OS has not yet been reached. In experiments conducted to define its anti-cancer mechanism, orally administered talactoferrin was found to act at the gut and the Gut Associated Lymphoid Tissue (GALT). Talactoferrin induced the chemotaxis of immune cells to intestinal Peyer’s Patches in mice, initiating an immunostimulatory cascade in the GALT and activating both innate and adaptive immunity. We observed significantly increased numbers of Dendritic Cells, NK-T cells and CD8+ T-lymphocytes in small intestinal Peyer’s patches, a systemic increase in Natural Killer (NK) and Cytotoxic T-lymphocyte (CTL) activity, activation of tumor draining lymph nodes, and cellular infiltration of distant tumors. The critical role of NK-T and CD8+ cells was demonstrated in knockout and depletion experiments. Conclusions: Talactoferrin, a first-in-class molecule with apparent clinical anti-cancer activity in RCC, acts through a novel immunomodulatory mechanism of action. [Table: see text]