CTI BioPharma Corp., a biopharmaceutical company, announced the initiation of its rolling new drug application (NDA) to the US Food and Drug Administration (FDA) for pacritinib, an investigational oral kinase inhibitor with specificity for JAK2, FLT3, IRAK1 and CSF1R. As part of the application, CTI BioPharma and its partner, Baxalta Incorporated (Baxalta), are seeking accelerated approval and priority review for pacritinib for the treatment of patients with intermediate and high-risk myelofibrosis with low platelet counts of less than 50,000 per microliter (<50,000/uL).

If approved for the requested indication, pacritinib would be the first JAK2 inhibitor approved for the treatment of patients with myelofibrosis with platelet counts of less than 50,000/uL – a specific patient population for which there are currently no approved drugs. The rolling NDA allows completed portions of an NDA to be submitted and reviewed by the FDA on an ongoing basis. CTI BioPharma and Baxalta plan to complete the submission before the end of 2015.

Myelofibrosis (a type of myeloproliferative neoplasm) is a rare, but serious and life-threatening chronic bone marrow disorder caused by the accumulation of malignant bone marrow cells that triggers an inflammatory response and scars the bone marrow. Myelofibrosis is associated with significantly reduced quality of life and shortened survival, can affect patients of all ages (with a median affected age being 65 years) and an estimated prevalence in the United States of approximately 18,000 patients.

"We believe the initiation of the rolling NDA submission represents a major step forward toward potentially offering pacritinib as a next generation JAK2/FLT3 inhibitor to patients with this rare and chronic type of blood cancer," said James A. Bianco, M.D., president and CEO of CTI BioPharma.

"We are excited to have achieved this milestone and look forward to working with the FDA during the review process, with the goal of bringing this important treatment to market – which we hope will fill an unmet need for many patients whose lives are profoundly impacted by myelofibrosis."

The submission includes data from the PERSIST-1 phase 3 trial – as well as data from phase 1 and 2 studies of pacritinib. Submission of an NDA after a single phase 3 trial under accelerated approval, instead of waiting to complete two phase 3 trials, could potentially reduce time to market by up to 14 months. In August 2014, pacritinib was granted Fast Track designation by the FDA for the treatment of intermediate and high-risk myelofibrosis including, but not limited to, patients with disease-related thrombocytopenia (low platelet counts); patients experiencing treatment emergent thrombocytopenia on another JAK2 therapy; or patients who are intolerant to or whose symptoms are not well controlled (or sub-optimally managed) on another JAK2 therapy.

Myelofibrosis is a one of three main types of myeloproliferative neoplasms (MPN), which are a closely related group of hematological blood cancers. The three main types of MPNs are myelofibrosis, polycethemia vera, and essential thrombocythemia. Myelofibrosis is a serious and life-threatening chronic bone marrow disorder caused by the accumulation of malignant bone marrow cells that triggers an inflammatory response and scars the bone marrow. The replacement of bone marrow with scar tissue limits its ability to produce red blood cells, prompting the spleen and liver to take over this function. Symptoms that arise from this disease include enlargement of the spleen, anemia, extreme fatigue, and pain.

The estimated prevalence of MPNs suggest there are approximately 300,000 people living with the disease in the US of which myelofibrosis accounts for approximately 18,000 patients. In Europe, there is a wide variation of prevalence observed across data sources. Myelofibrosis has a median age of 64 at the time of diagnosis and is a progressive disease with approximately 20 per cent of patients eventually developing acute myeloid leukemia. The median survival for high-risk patients is less than one and a half years; median survival for myelofibrosis patients overall is approximately six years.

Pacritinib is an investigational oral kinase inhibitor with specificity for JAK2, FLT3, IRAK1 and CSF1R. In August 2014, pacritinib was granted Fast Track designation by the FDA for the treatment of intermediate and high risk myelofibrosis, including but not limited to patients with disease-related thrombocytopenia, patients experiencing treatment-emergent thrombocytopenia on other JAK2 inhibitor therapy, or patients who are intolerant of, or whose symptoms are sub-optimally managed on other JAK2 inhibitor therapy. The FDA's Fast Track process is designed to facilitate the development and expedite the review of drugs to treat serious conditions and fill an unmet medical need. Pacritinib does not have regulatory approval and is not commercially available.

CTI BioPharma and Baxalta are parties to a worldwide license agreement to develop and commercialise pacritinib. CTI BioPharma and Baxalta will jointly commercialise pacritinib in the US while Baxalta has exclusive commercialisation rights for all indications outside the US.