Grafapex Approved for Reduced-Intensity Stem Cell Transplants in AML and MDS Patients

Canadian company Medexus Pharmaceuticals recently announced the FDA approval of Grafapex (treosulfan) as part of a conditioning regimen for allogeneic hematopoietic stem cell transplantation.

The chemotherapy drug was approved for use in combination with fludarabine in adults and children one year and older with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS).

AML is a rare blood cancer that begins in the bone marrow. In 2025, about 22,000 people in the United States will be diagnosed with AML and about 11,000 Americans will die from the disease, according to the American Cancer Society.

MDS occurs when some of the cells in the bone marrow become abnormal and crowd out healthy cells, leading to amenia. MDS is uncommon before age 50; t is most commonly diagnosed in people in their 70s. According to the American Cancer Society, the number of people diagnosed is not known, but some estimates have placed it about 10,000 people diagnosed in the United States.

Treosulfan was approved in Canada in June 2021 for the same use and is marketed under the brand name Trecondyv.

Stem cell transplantation is considered the only curative treatment for patients with AML or MDS. Before receiving donor stem cells, patients receive a conditioning regimen designed to destroy existing bone marrow cells. These regimens typically consist of high-dose radiation or chemotherapy treatment and, due to associated toxicities, are often reserved for younger patients without comorbidities.

Reduced-intensity conditioning regimens have been developed for use in older patients or those who are otherwise ineligible for the more aggressive treatment. However, these reduced-dose treatments have been associated with higher rates of disease recurrence after transplantation.

A pivotal phase 3 trial compared treosulfan with fludarabine to the conventional reduced-intensity regimen busulfan with fludarabine as a stem cell transplant preparative treatment. The study included 570 patients with AML or MDS who were considered ineligible for high-intensity regimens due to age (between 50 and 70 years) or the presence of comorbidities.

Results showed that more participants receiving treosulfan with fludarabine had event-free survival three years after treatment compared with patients who received the conventional regimen (60% versus 50%). Three-year overall survival rates were also higher in the treosulfan group versus the busulfan group (67% versus 53%). The most common adverse effects included musculoskeletal pain, fever, stomatitis, nausea, vomiting, edema, and infection.

Medexus plans to release Grafapex in the U.S. market during the first half of 2025. The treatment has the potential to generate over $100 million in annual revenue within five years of launching, according to Richard Labelle, chief operating officer at Medexus. The product’s Orphan Drug designation confers up to seven years of marketing exclusivity.