• All three sickle cell disease participants treated with briquilimab successfully engrafted with neutrophil engraftment within 12-16 days
  • First two participants with peripheral blood chimerism at 60 days after allogeneic stem cell transplant achieved 100% donor myeloid chimerism
  • First participant treated has a total hemoglobin level of 13.3 g/dL at five months follow up, increased from 8-9 g/dL at baseline

REDWOOD CITY, CA, USA I January 03, 2023 I Jasper Therapeutics, Inc. (NASDAQ: JSPR), a biotechnology company focused on transforming the field of hematopoietic stem cell therapies, today announced positive clinical data from the first three participants in an investigator-initiated Phase 1/2 clinical trial (NCT05357482) evaluating the addition of briquilimab (formerly known as JSP191), Jasper’s anti-c-KIT monoclonal antibody, to an existing bone marrow transplantation regimen (NCT00061568) in individuals with sickle cell disease (SCD) and beta thalassemia considered at high risk for complications from or ineligible for standard myeloablative hematopoietic stem cell transplant. The addition of briquilimab is being studied as a potential way to achieve a higher percentage of healthy donor stem cell engraftment (donor chimerism) without increased toxicity. The Phase 1/2 clinical study is led by Dr. John F. Tisdale, Director of the Cellular and Molecular Therapeutics Laboratory, NHLBI.

“While stem cell infusion with healthy donor stem cells or gene-corrected cells are potentially curative options for SCD and beta thalassemia, they are both limited by the toxicity of current conditioning regimens using busulfan or melphalan, which are often cited as the most concerning safety risks for transplant patients and physicians,” said Ronald Martell, President and CEO of Jasper Therapeutics. “With briquilimab, we hope to offer a highly targeted conditioning regimen to directly address conditioning toxicity as a barrier limiting the ability of patients to access curative hematopoietic stem cell therapies.”

For SCD and beta-thalassemia, transplantation of healthy donor stem cells is a multi-step process. After donor cells are collected, a human subject’s existing stem cells must be cleared from the bone marrow to make space for the transplanted cells, which is known as bone marrow conditioning. Next, the newly transplanted cells must survive and replicate within the bone marrow, which is known as bone marrow engraftment. The extent of engraftment is measured by the proportion of the donor cells and the human subject’s own cells, which is known as donor chimerism. As has been shown, improving chimerism is crucial to lead to a sufficient proportion of healthy donor stem cells that produce healthy red blood cells and reverse the sickle phenotype after the stem cell transplant.

The primary objective of the study is to determine if the addition of briquilimab would increase the proportion of patients with donor myeloid chimerism ≥98% at 1-year post-transplant. Briquilimab has the potential to improve disease-free survival in combination with low-dose irradiation as part of a transplant conditioning regimen. The study is currently actively enrolling at NHLBI.

In this study, briquilimab was added to the regimen used at NHLBI consisting of alemtuzumab, low-dose irradiation, and sirolimus prior to infusion of mobilized peripheral blood cells from human leukocyte-antigen matched related donors. All three sickle cell study participants treated with briquilimab have successfully engrafted with no briquilimab-related severe adverse events observed. Participant 1 achieved neutrophil engraftment at 12 days after transplant and platelet engraftment at 17 days after transplant. Participant 2 achieved neutrophil engraftment at 12 days and platelet engraftment at 10 days. Participant 3 achieved neutrophil engraftment at 16 days and platelet engraftment at 8 days. Both of the first two participants with peripheral blood chimerism achieved 100% donor myeloid chimerism at 60 days post-transplant. At five months post-transplant, the first participant treated with briquilimab has a total hemoglobin of 13.3 g/dL, increased from 8-9 g/dL at baseline.

About Briquilimab (formerly known as JSP191)

Briquilimab is a targeted, monoclonal antibody that inhibits the cell-surface receptor c-KIT, also known as CD117. It is currently being evaluated as a conditioning agent for cell and gene therapies, as well as a standalone therapy. To date, briquilimab has a demonstrated efficacy and safety profile in 130 dosed subjects and healthy volunteers, with clinical outcomes as a conditioning agent in severe combined immunodeficiency (SCID), acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), Fanconi anemia (FA), and sickle cell disease (SCD). In addition, briquilimab is being advanced as a transformational non-genotoxic conditioning agent for gene therapy and as a primary therapeutic in low-risk MDS patients. Clinical studies also suggest briquilimab can be used as a primary therapeutic to treat mast cell diseases such as chronic spontaneous urticaria (CSU), chronic inducible urticaria (CIndU), and allergic asthma.

About Jasper Therapeutics

Jasper Therapeutics is a clinical-stage biotechnology company focused on unlocking access to curative therapies by targeting and eliminating diseased stem cells. Jasper’s lead program is briquilimab, a first-in-class monoclonal antibody targeting c-KIT (CD117), an important receptor found on stem cells and mast cells. In parallel, Jasper is advancing its mRNA cellular programming platform which is designed to overcome key limitations of allogeneic and autologous gene-edited stem cell grafts by transiently modifying stem cells with mRNA, augmenting them to treat several diseases of the blood and bone marrow. Both innovative programs have the potential to enable curative therapies to a greater number of patients with life-threatening cancers, genetic disorders, and inflammatory diseases. For more information, please visit us at jaspertherapeutics.com.

SOURCE: Jasper Therapeutics