Rilzabrutinib. an oral, reversible covalent Bruton tyrosine kinase inhibitor, has shown promise in treating immune thrombocytopenia (ITP), according to investigators at Massachusetts General Hospital (MGH).

In Phase 1-2 trial, the drug has generated promising safety and efficacy results, which could pave the way for more advanced clinical trials.

The trial findings were published in the New England Journal of Medicine. Sanofi, which develops rilzabrutinib, supported the trial.

ITP is a condition in which the body produces destructive antibodies against platelets in the blood, increasing the risk of bruising, bleeding, hospitalization, fatigue, death, and affecting the quality of life.

Studies have shown that macrophages are responsible for destroying antibody-coated platelets in ITP, and the enzyme Bruton kinase is critical to their function.

Rilzabrutinib was developed as an oral Bruton kinase inhibitor that reduces macrophage activity and the production of anti-platelet antibodies. However, it does not affect the function of platelets.

Lead author of the trial Dr. David Kuter said, “We hypothesized that rilzabrutinib would be effective in both reducing the antibody attacking the platelets as well as minimizing the rate of platelet destruction by the macrophages.”

In the trial, all treatment-related adverse events were minor and transient. The patients involved in the trial had already tried multiple therapies, with their disease being considered highly refractory to treatment.

The researchers have started the process of a major phase 3 clinical trial at many sites in order to test the efficacy of rilzabrutinib in patients with ITP.

Dr. Kuter said, “If the findings of our study are borne out in other studies, rilzabrutinib may provide a rapid rise in platelet count and a sustained increase to a safe platelet count number, which could thereby minimize bleeding, and the drug could conceivably make the antibody causing the disease to disappear.”

“What is impressive is that this drug lacks major negative effects that have been historically associated with this class of medications,” he added. “We saw no increased risk of bleeding, infection, liver dysfunction, or intolerance by patients.”