In the second quarter of 2021, the FDA granted priority review for CTI’s NDA for patients with myelofibrosis with a PDUFA date of November 30, 2021. In the course of product labeling discussions, the FDA requested additional clinical data, which was submitted to the agency on November 24, 2021. Earlier today, the FDA informed the Company that it considers the data submission to constitute a “major amendment” to the NDA and therefore the PDUFA date has been extended by three months to provide additional time for a full review of the submission. At the current time, CTI is not aware of any major deficiencies in the application.
Pacritinib is a novel oral kinase inhibitor with specificity for JAK2, IRAK1 and CSF1R, without inhibiting JAK1. The NDA was accepted based on the data from the Phase 3 PERSIST-2 and PERSIST-1 and the Phase 2 PAC203 clinical trials, with a focus on the severely thrombocytopenic (platelet counts less than 50 x 109/L) patients enrolled in these studies who received pacritinib 200 mg twice a day, including both frontline treatment-naive patients and patients with prior exposure to JAK2 inhibitors. In the PERSIST-2 study, in patients with severe thrombocytopenia who were treated with pacritinib 200 mg twice a day, 29% of patients had a reduction in spleen volume of at least 35%, compared to 3% of patients receiving the best available therapy, which included ruxolitinib; 23% of patients had a reduction in total symptom scores of at least 50%, compared to 13% of patients receiving the best available therapy. In the same population of patients treated with pacritinib, adverse events were generally low grade, manageable with supportive care, and rarely led to discontinuation. Platelet counts and hemoglobin levels were also stabilized.
Myelofibrosis is bone marrow cancer that results in formation of fibrous scar tissue and can lead to thrombocytopenia and anemia, weakness, fatigue and an enlarged spleen and liver. Within the U.S. there are approximately 21,000 patients with myelofibrosis, 7,000 of which have severe thrombocytopenia (defined as blood platelet counts of less than 50 x109/L). Severe thrombocytopenia is associated with poor survival and high symptom burden and can occur as a result of disease progression or from drug toxicity with other JAK2 inhibitors such as JAKAFI and INREBIC.