FDA Grants Orphan Drug Designation to KRP203 Following allo-HSCT in Patients with Hematologic Malignancies


This is KRP203’s second Orphan Drug Designation and it is the only S1P receptor modulator being developed as an adjunctive and maintenance treatment for blood cancers.

The FDA has granted Orphan Drug designation (ODD) to KRP203 (mocravimod; Priothera Ltd.), a sphingosine-1-phosphate (S1P) receptor modulator, for the treatment to improve outcomes following hematopoietic stem cell transplantation in hematologic malignancies. The treatment aims to increase leukemia-free survival by improving graft-versus-leukemia (GvL) response in patients.

“We are very pleased that the FDA granted [KRP203] this ODD. This designation emphasizes the importance of developing novel therapeutic options to improve the outcome and success of maintenance therapy following allogeneic hematopoietic stem cell transplant (allo-HSCT) in [patients with blood cancer],” said Florent Gros, MBA, co-founder and CEO of Priothera, in a press release.

Concept of FDA Food and Drug Administration

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KRP203 is a S1P receptor modulator that is being investigated in the pivotal global phase 3 study, MO-TRANS (NCT05429632). The study will evaluate the efficacy and safety of KRP203 as an adjunctive and maintenance therapy to allo-HSCT in 250 adult patients with acute myeloid leukemia. KRP203’s intended dual mode of action is to maintain the beneficial GvL activity while simultaneously reducing tissue damage that results from GvHD, both consequences of allo-HSCT. This novel treatment approach tackles a high unmet need and aims to improve the quality of life in patients.

Further, KRP203 was previously tested in multiple autoimmune indications and is expected to enhance the curative potential of allo-HSCT. This expectation comes from a clinically meaningful outcome in a phase 1b/2a study in patients with hematologic malignancies undergoing allo-HSCT.

KRP203 was initially granted ODD for the prevention of graft-versus-host disease (GvHD). The ODD is reserved for medicines treating rare, life-threatening, or chronically debilitating diseases.

“The 2 ODDs highlight [KRP203’s] dual mode of action which for the first time is being leveraged to improve the allo-HSCT treatment outcomes in hematological malignancies to potentially increase the leukemia-free survival—GvL response—while reducing tissue damage resulting from the GvHD,” Gros said in the press release. “This is an important milestone as this ODD complements the first ODD granted for prevention of GvHD."


BioSpace. Priothera – US FDA grants Orphan Drug Designation to mocravimod to improve the outcome of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with hematologic malignancies. News release. November 27, 2023. Accessed November 28, 2023. https://www.biospace.com/article/releases/priothera-us-fda-grants-orphan-drug-designation-to-mocravimod-to-improve-the-outcome-of-allogeneic-hematopoietic-stem-cell-transplantation-allo-hsct-in-patients-with-hematologic-malignancies

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