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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

Mocravimod is the only S1P receptor modulator being developed as an adjunctive and maintenance treatment for blood cancers

Mocravimod is being investigated in a global registration-enabling Phase 3 trial

This is the second Orphan Drug designation for mocravimod

Dublin, Ireland – 27 November 2023 – Priothera Ltd., a Phase 3 clinical stage biotechnology company pioneering the development of its S1P receptor modulator compound mocravimod, today announced that the US Food and Drug Administration (FDA) has granted Orphan Drug designation (ODD) to mocravimod for the “treatment to improve outcome following hematopoietic stem cell transplantation in hematologic malignancies”. This ODD aims to potentially increase leukemia-free survival by triggering a ‘graft-versus-leukemia’ (GvL) response.

Florent Gros, Co-Founder and CEO of Priothera, commented: “We are very pleased that the US FDA granted mocravimod this Orphan Drug designation. This designation emphasizes the importance of developing novel therapeutic options to improve the outcome and success of maintenance therapy following allo-HSCT in blood cancer patients. This is an important milestone as this ODD complements the first ODD granted for prevention of ‘graft-versus-host disease’.  

“The two ODDs highlight mocravimod’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 – ‘graft-versus-leukemia’ response – while reducing tissue damage resulting from the ‘graft-versus-host disease’.”

The first ODD granted for mocravimod by the US FDA was for the “prevention of graft-versus-host disease (GvHD)” – see press release here.

Mocravimod, a sphingosine-1-phosphate (S1P) receptor modulator, is being investigated in a pivotal global Phase 3 study – MO-TRANS (NCT05429632) – evaluating the efficacy and safety of mocravimod as an adjunctive and maintenance therapy to allo-HSCT.  The study which is enrolling approximately 250 adult Acute Myeloid Leukemia (AML) patients, is ongoing in the US, Europe, Southeast Asia and Latin America.

Mocravimod, which has been previously tested in multiple autoimmune indications, is being developed to enhance the curative potential of allo-HSCT. Moreover, it has shown a clinically meaningful outcome in a Phase 1b/2a study[1] in patients with hematologic malignancies undergoing allo-HSCT.

The Orphan Drug designation is reserved for medicines treating rare, life-threatening or chronically debilitating diseases.

[1]*Ref: Dertschnig et al, 2023

About mocravimod

Mocravimod (also known as KRP203) is a synthetic, S1P receptor modulator. This novel investigational drug has been assessed in Phase 1 and Phase 2 trials for safety and tolerability, as well as for efficacy in several autoimmune indications. Promising data from a Phase 1b/2a clinical study in patients with hematological malignancies led Priothera to further develop mocravimod for the treatment of blood cancers and the improvement of CAR-T cell therapy.

Mocravimod is currently being investigated as an adjunctive and maintenance treatment in a Phase 3 study for patients with AML receiving allogeneic HSCT. Allogeneic HSCT is the only potentially curative approach for AML patients, but current treatments have unacceptably high mortality and morbidity rates.

Priothera leverages mocravimod’s dual mode of action to maintain the beneficial graft-versus-leukemia/lymphoma (GvL) activity, while reducing tissue damage resulting from graft-versus-host disease (GvHD), both a consequence of allo-HSCT. This novel treatment approach – mocravimod being the only S1P receptor modulator treating blood cancers – tackles a high unmet medical need and aims to improve patients’ quality of life.

About Priothera

Priothera is leading the way in developing orally applied S1P receptor modulators for the treatment of hematological malignancies and for the improvement of CAR-T cell therapies. S1P receptor modulators are known to largely reduce egress of T cells from lymphatic tissues. Unlike immunosuppressive drugs, mocravimod does not suppress the GvL benefits in patients receiving allogeneic HSCT while inhibiting GvHD.

Priothera was founded in 2020 by an experienced team of drug development experts and is headquartered in Dublin, Ireland, and with a subsidiary in Saint-Louis, France. The Company is backed by international founding investors Fountain Healthcare Partners (Dublin, Ireland), funds managed by Tekla Capital Management, LLC (Boston, Massachusetts), HealthCap (Stockholm, Sweden), EarlyBird Venture Capital (Berlin, Germany), as well as non-dilutive financing in the form of loans from the European Investment Bank under its Venture Debt Instrument and Bpifrance (Grand Est Bpifrance) in the form of a R&D innovation loan.

For more information please visit or follow Priothera on LinkedIn


Florent Gros, CEO

MEDiSTRAVA Consulting
Sylvie Berrebi, Sandi Greenwood, Frazer Hall
T: +44 (0) 203 928 6900

Source: Priothera