FDA Extends Review for Pacritinib for Treatment of Myelofibrosis With Severe Thrombocytopenia

CTI BioPharma's New Drug Application had previously been granted Priority Review. The PDUFA date was November 30.

On November 30, FDA extended the review period for pacritinib, a novel therapy to treat adult patients with intermediate- or high-risk primary or secondary myelofibrosis with severe thrombocytopenia. The Prescription Drug User Fee Act (PDUFA) action date was extended by 3 months to February 28, 2022, according to a statement from CTI Biopharma Corp.1

FDA had previously granted Priority Review for the new drug application (NDA) for patients with myelofibrosis, with a PDUFA date of November 30. During discussions for the drug’s label, the agency requested additional data, which CTI BioPharma’s statement said was submitted on November 24. According to CTI BioPharma, FDA stated that the submission constituted a “major amendment,” triggering the extension to allow for additional review. In its statement, CTI said the company was not aware of any major deficiencies in the application.

“CTI is continuing to engage collaboratively and constructively with the FDA during review of our NDA," Adam R. Craig, MD, PhD, president and CEO of CTI BioPharma, said in the statement. "We are committed to providing patients suffering from cytopenic myelofibrosis with a new treatment option as soon as possible and are confident in pacritinib's potential to establish a new standard of care."

Pacritinib, an oral kinase inhibitor with specificity for JAK2, IRAK1, and CSF1R, had been given Priority Review based on results from a pair of phase 3 trials, PERSIST-2 (NCT02055781) and PERSIST-1 (NCT01773187), as well as an earlier study that examined the effectiveness of pacritinib in patients with severe thrombocytopenia.2

PERSIST-2 involved 311 patients and showed that pacritinib 200 mg taken twice daily was significantly more effective than the best available therapies, including ruxolitinib. Of note, a reduction in spleen volume of at least 35% was seen in 29% of those taking pacritinib compared with just 3% of those taking the best available therapy.3

In PERSIST-1, investigators found that pacritinib was well tolerated; patients taking it experienced significant spleen volume reduction and reduced myelofibrosis symptoms. The most common grade 3/4 adverse effects through week 24 of pacritinib treatment were anemia (17%), thrombocytopenia (12%), and diarrhea (5%).4

The company plans several presentations at the upcoming meeting of the American Society of Hematology in Atlanta, set for December 10-14.


  1. CTI BioPharma announces extension of FDA review period for pacritinib in myelofibrosis with severe thrombocytopenia. News release. CTI BioPharma. Accessed November 30, 2021. https://bit.ly/3G2XO3m
  2. CTI BioPharma announces acceptance of NDA granted with Priority Review of pacritinib for treatment of patients with myelofibrosis. News release. CTI BioPharma. June 1, 2021. Accessed November 27, 2021. https://bit.ly/3cQZGj4
  3. Mascarenhas J, Hoffman R, Talpaz M, et al. Pacritinib vs best available therapy, including ruxolitinib, in patients with myelofibrosis. JAMA Oncol. 2018;4(5):652-659. doi:10.1001/jamaoncol.2017.5818
  4. Mesa RA, Vannucchi AM, Mead A, et al. Pacritinib versus best available therapy for the treatment of myelofibrosis irrespective of baseline cytopenias (PERSIST-1): an international, randomised, phase 3 trial. Lancet Haematol. 2017;4(5):e225-e236. doi:10.1016/S2352-3026(17)30027-3