Data related to the Phase 1 study development of briquilimab in combination with fludarabine and low-dose irradiation (Flu/TBI) in older adults (62 to 79 years) with AML, undergoing allogeneic hematopoietic cell transplant (HCT), has been presented by Jasper Therapeutics at the 2023 Transplantation & Cellular Therapy Meetings of ASTCT and CIBMTR.

Briquilimab has shown it is a safe and well-tolerated conditioning agent for older patients (average age, 70 years) who are receiving an allogeneic hematopoietic cell transplantation, lower than expected rates of severe acute and chronic graft-vs-host disease and “durable remissions achieved in 8 of the first 12 AML patients treated at one-year follow up.”

Briquilimab (formerly known as JSP191) is a monoclonal antibody (a type of a protein that is created in a lab that can bind to certain antigens on the surface of a cancer cell) that inhibits the cell surface receptor, c-Kit (also known as CD117). “CD117 is the receptor for Stem Cell Factor on blood forming cells. CD117 binding to Stem Cell Factor is critical for survival and maintenance of blood forming stem cells. (NCT04429191).”

Blood stem cell transplants offer the only curative chance for overall survival (OS) in patients with AML. Thus, “The binding of briquilimab to CD117 blocks CD117 from binding to Stem Cell Factor on blood forming stem cells. In the absence of CD117/Stem Cell Factor binding, hematopoietic stem cells that are currently occupying the bone marrow niches in MDS/AML patients are depleted.”

This is a Phase 1a/b interventional study on the safety and tolerability of briquilimab combined with fludarabine and low-dose radiation.

Study Details

• 40 participants
• AML must be in complete remission (CR)
• Phase 1a will offer a 3 dose option: 0.3mg/ 0.6mg/ 1.0 mg
• Only a single dose of briquilimab will be given
• Once the antibody has cleared to a certain level, the patient will then receive a stem cell transplant
• The phase 1b portion of the study will add more patients and study each dose and its safety and feasibility

Key findings from the 2023 Tandem Meetings: Transplantation & Cellular Therapy Meetings of ASTCT and CIBMTR:

• The 1 year follow-up of 12 AML patients who received the Phase 1a treatment showed that the 0.6 dose was well tolerated with no infusion reactions
• “8 out of 12 (67%) of the evaluated AML patients were determined to be free from morphological relapse and 6 out of 9 (67%) of the patients who received a transplant with detectable AML have no measurable residual disease at last follow-up.”
• All patients achieved engraftment with neutrophil recovery (sustained sequenced days of maintaining the appropriate blood neutrophil count) between 13 and 24 days.
• The 11 evaluable subjects at day 90 achieved full donor myeloid chimerism (graft vs. host balance)
• 3 patients have relapsed after transplant. 1 at 2 months. 2 at 6 months