Vasculox, Inc. is developing a humanized anti-CD47 mAb for reducing ischemia-reperfusion injury (IRI) in organ transplantation. In spite of improvements in surgical technique, organ preservation and immunosuppression, IRI remains a serious limitation and is responsible for delayed graft function, initial graft failure and contribtes to poor long-term graft survival, thus representing an area of significant unmet medical need. Increasing nitric oxide (NO) signaling can provide a substantial therapeutic benefit in reducing IRI. The founders of Vasculox discovered that thrombospondin-1 (TSP1) binding to its receptor, CD47, limits NO signaling in all vascular tissues. Blocking TSP-1 binding with an anti-CD47 monoclonal antibody (anti-CD47 mAb) relieves this inhibition of NO signaling and improves outcomes in several animal models of IRI. We have recently demonstrated efficacy of an anti-CD47 mAb to improve liver function in an ex vivo perfusion model and in a rat liver transplant model. Vasculox has characterized a panel of 9 mouse monoclonal mAbs (400 series mAbs) that are unique in reacting broadly across species with human, rodent, dog and pig providing a significant advantage for clinical development. Three of these mAbs reverse the TSP1-CD47 mediated inhibition of NO-stimulated cGMP formation in cultured cells and one of these will be taken forward for humanization. In this Phase II SBIR grant the specific aims are: Aim 1. Humanize the lead CD47 mAb candidate, produce research grade material for preclinical studies. Aim 2A. Establish optimal conditions for efficacy of CD47 mAb in a rat syngeneic liver transplant model including administration and dosing modality (pre-treat organ alone, treat recipient alone or treat both) and adjuvant treatments to enhance the NO signaling pathway (arginase inhibitors and/or L-arginine) Aim 2B. Demonstrate efficacy of the humanized mAb in a large animal (porcine) model of transplant using the optimized treatment modality as determined in Aim 2A. Aim 3. Carry out non-GLP (preliminary) pharmacokinetic and safety studies in the rat and non-human primate using the CD47 humanized mAb to prepare for GLP IND-enabling studies. This phase II proposal addresses several critical path milestones for Vasculox that will allow us to address transplant IRI as well as additional indications for anti-CD47 therapy including IRI arising from surgical procedures, trauma, sickle cell crisis and pulmonary hypertension.