Forty Seven, Inc. announced preclinical proof-of-concept data for its novel all antibody conditioning regimen, comprised of FSI-174, its anti-cKIT antibody, and magrolimab, its anti-CD47 antibody. Preclinical studies in a non-human primate (NHP) model showed that the combination of FSI-174 and magrolimab significantly depleted hematopoietic stem cells (HSCs) from the bone marrow, with no dose limiting toxicities. The data will be presented in a poster session at the 61st American Society of Hematology (ASH) Annual Meeting in Orlando, Florida. Forty Seven's novel all antibody condition regimen seeks to address the limitations of current stem cell transplantation (SCT) conditioning regimens, which utilize chemotherapy and/or radiation to kill HSCs and make space for transplanted cells. These regimens are highly toxic, induce immune suppression and may require hospitalization. Numerous comorbidities are often observed, including severe infections, impaired brain development, infertility, endocrine dysfunction, secondary malignancies and organ damage. As a result, many patients are ineligible for, or choose not to undergo, SCT. In the preclinical data presented at ASH, FSI-174 demonstrated binding affinity to both human and NHP cKIT receptors, and induced phagocytosis as well as antibody-dependent cell-mediated cytotoxicity (ADCC) in a dose-dependent manner. Additionally, FSI-174 was well-tolerated when administered to NHPs as a single agent, with no dose-limiting toxicities. The no-observed-adverse-effect level (NoAEL) was established at 50 mg/kg, the highest dose tested. When administered together, FSI-174 and magrolimab demonstrated a synergistic benefit, promoting the highest level of phagocytosis of cKIT expressing target cells and inducing significant HSC depletion nine days after infusion compared to placebo. As expected, there were no changes in blood cell counts over the course of the study, with no cytopenias observed with either monotherapy or combination treatment. These pharmacodynamic and NHP data demonstrate the specificity and safety of FSI-174 and magrolimab, and reveal a window for SCT where the cKIT antibody is washed out, but the depletion of HSCs is sustained long enough to enable the transplantation of donor HSCs. Forty Seven expects to complete investigational new drug (IND)-enabling studies by the end of 2019, and subject To Approve the IND by the U.S. Food and Drug Administration, plans to initiate a Phase 1 clinical trial evaluating FSI-174 in healthy volunteers in the first quarter of 2020.