JSP191 is a targeted, humanized monoclonal antibody in clinical development as a conditioning agent to clear hematopoietic stem cells from bone marrow prior to transplant.

JSP191 is designed to address the limitations of current conditioning by replacing chemotherapy/radiation in patients undergoing curative hematopoietic stem cell transplants and gene therapies.

Mechanism Of Action

A unique compound, JSP191 binds to human CD117, a receptor for stem cell factor (SCF) that is expressed on the surface of hematopoietic stem and progenitor cells. The interaction of SCF and CD117 is required for stem cells to survive. JSP191 blocks SCF from binding to CD117 and disrupts critical survival signals, causing the stem cells to undergo cell death. This creates an empty space in the bone marrow for donor or gene-corrected transplanted cells to engraft. Because JSP191 does not carry a toxic payload or recruit immune cells to induce an immune response, the likelihood of off-target toxicities is significantly reduced.


Preclinical Study Results

Preclinical studies have shown:

  • JSP191 as a single agent safely depletes hematopoietic stem cells in animal transplant models of SCID, sickle cell disease and myelodysplastic syndromes (MDS).
  • JSP191 directly depletes diseased MDS cells.
  • Treatment with JSP191 creates the space needed for transplanted normal donor or gene-corrected hematopoietic stem cells to successfully engraft in the host bone marrow.

Clinical Development

To date, JSP191 has been evaluated in more than 120 healthy volunteers and patients. This humanized antibody is currently being studied in Jasper-sponsored clinical trials in hematopoietic stem cell transplantation.

  • SCID: Phase 1/2 dose-escalation and expansion trial is evaluating JSP191 as a sole conditioning agent to achieve donor stem cell engraftment in patients undergoing hematopoietic stem cell transplantation for SCID, which is potentially curable only by this type of treatment. (NCT02963064)
  • AML/MDS: A Phase 1 trial is evaluating JSP191 in combination with another low-intensity conditioning regimen in patients with myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML) undergoing hematopoietic stem cell transplantation. (NCT04429191)

Initial results from JSP191 clinical studies have been presented at the American Society of Hematology (ASH) 2021 annual meeting for SCID and at the Transplant and Cellular Therapy (TCT) 2022 conference for AML/MDS.

Additional studies will advance JSP191 as a conditioning agent for patients with other genetic disorders (Fanconi’s Anemia, Sickle Cell Disease, X-linked SCID) and autoimmune diseases (lupus, multiple sclerosis, scleroderma).

See our expanding pipeline here.