S*BIO Pte Ltd announced that results from a Phase 2 study demonstrated that its JAK2 inhibitor pacritinib (SB1518) effectively reduced splenomegaly in myelofibrosis (MF) patients, with minimal impact on existing cytopenias providing an important therapeutic niche in the treatment of MF.
“Pacritinib is an active drug for the treatment of splenomegaly in patients with primary myelofibrosis, post-polycythemia vera-myelofibrosis and post-essential thrombocythemia-myelofibrosis regardless of baseline thrombocytopenia,” said Rami S. Komrokji, M.D., principal author of the oral presentation. “The once daily dose of pacritinib was well tolerated with manageable gastrointestinal toxicity as the main side effect. The minimal impact on existing cytopenias in MF patients provides an important therapeutic outcome for pacritinib in the treatment of this patient population. The results support the rapid advancement of pacritinib into Phase 3 clinical trials to further support its safety and efficacy.”
The primary endpoint of pacritinib’s Phase 2 study was to assess the spleen response rate, defined as a ?35% reduction in MRI-measured spleen volume between baseline and week 24. Thirty-four MF patients were enrolled in the study. The most common treatment-related adverse events were gastrointestinal, which were generally low grade and easily managed. Pacritinib was equally well tolerated by patients with normal platelet counts and those with thrombocytopenia and anemia. Thirty patients (88%) showed reduction in palpable splenomegaly, 14 (41%) showed decreases of ?50% and five (15%) achieved clinical resolution of splenomegaly. Eight patients (24%) had decreases in spleen volume by > 35%. Spleen response rates were equivalent among patients with low baseline platelet counts and those with normal baseline counts. At the six-month visit, a significant reduction (>2 point improvement in mean symptom score) was observed for MF-associated symptoms, including abdominal pain, bone pain, early satiety, worst fatigue, inactivity, night sweats and pruritus.
“There is a significant medical need in the treatment of myelofibrosis and the results from pacritinib’s clinical trials encourage us to quickly move forward with a global Phase 3 study to further demonstrate pacritinib’s clinical benefits and consequently capture an important niche market in the treatment of MF,” said Tamar Howson, interim CEO and board member of S*BIO.
Pacritinib is a small molecule JAK2-selective kinase inhibitor, which has demonstrated high potency in preclinical models against both the wild type JAK2 kinase and the JAK2 kinase with the V617F mutation. The V617F mutation is found in high frequencies in myeloproliferative disorders such as MF. It is estimated that approximately 50% of patients with MF possess the JAK2 mutation.
Date: December 12, 2011
Source: S*BIO Pte Ltd