Briquilimab (Formerly JSP191)

Briquilimab (JSP191) is an unconjugated, aglycosylated, anti-c-Kit antibody that functionally blocks the interaction of the c-Kit receptor from its ligand, stem cell factor (SCF). The interaction of SCF and c-Kit is required for mast and stem cells to survive. By blocking SCF from binding to c-Kit and disrupting the critical survival signal, briquilimab causes mast and stem cells to undergo cell death. For mast cell-driven diseases such as chronic urticaria, this removes the underlying source of the inflammatory response. For stem cell transplant, briquilimab clears the niche in the bone marrow for donor or gene-corrected hematopoietic stem cells to engraft. Briquilimab leverages its ability to potently target the SCF/c-Kit signaling pathway and does not carry a toxic payload or recruit immune cells to induce an immune response.

Mechanism Of Action

Briquilimab in Mast Cell-Driven Diseases

Briquilimab Effect on Diseased Stem Cells


Diseased Mast Cell


Mast Cell Treated with Briquilimab


Diseased Stem Cell Conditioned with Briquilimab

Preclinical Study Results

Preclinical studies have shown:

  • Briquilimab potently depletes mast cells in the skin and lungs.
  • Briquilimab as a single agent safely depletes hematopoietic stem cells in animal transplant models of SCID, sickle cell disease and myelodysplastic syndromes (MDS).
  • Briquilimab directly depletes diseased MDS cells.
  • Treatment with briquilimab 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, briquilimab has been evaluated in more than 130 healthy volunteers and patients. This humanized antibody is being studied in Jasper-sponsored clinical trials in multiple diseases.

  • SCID Transplant (ongoing): Phase 1/2 dose-escalation and expansion trial is evaluating briquilimab 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 transplant (ongoing): A Phase 1 trial is evaluating Briquilimab 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)
  • Low to Intermediate Risk MDS (upcoming): A clinical study to evaluate briquilimab as a chronic therapeutic for transfusion dependent low to intermediate risk MDS patients.
  • Chronic Urticaria (upcoming): A clinical study to evaluate briquilimab as a chronic therapeutic for patients with Chronic Urticaria.

See our expanding pipeline here.