Safety and efficacy of INCB018424, a JAK1 and JAK2 inhibitor, in myelofibrosis.

Abstract

BACKGROUND:

Myelofibrosis is a Philadelphia chromosome–negative myeloproliferative neoplasm associated with cytopenias, splenomegaly, poor quality of life, and shortened survival. About half of patients with myelofibrosis carry a gain-of-function mutation in the Janus kinase 2 gene (JAK2 V617F) that contributes to the pathophysiology of the disease. INCB018424 is a potent and selective Janus kinase 1 (JAK1) and JAK2 inhibitor.

METHODS:

We conducted a phase 1−2 trial of INCB018424 in patients with JAK2 V617F−positive or JAK2 V617F−negative primary myelofibrosis, post–essential thrombocythemia myelofibrosis, or post–polycythemia vera myelofibrosis.

RESULTS:

A total of 153 patients received INCB018424 for a median duration of more than 14.7 months. The initial dose-escalation phase established 25 mg twice daily or 100 mg once daily as maximum tolerated doses, on the basis of reversible thrombocytopenia. A dose-dependent suppression of phosphorylated signal transducer and activator of transcription 3 (STAT3), a marker of JAK signaling, was demonstrated in patients with wild-type JAK2 and in patients with the JAK2 V617F mutation. We studied additional doses and established that a 15-mg twice-daily starting dose, followed by individualized dose titration, was the most effective and safest dosing regimen. At this dose, 17 of 33 patients (52%) had a rapid objective response (≥50% reduction of splenomegaly) lasting for 12 months or more, and this therapy was associated with grade 3 or grade 4 adverse events (mainly myelosuppression) in less than 10% of patients. Patients with debilitating symptoms, including weight loss, fatigue, night sweats, and pruritus, had rapid improvement. Clinical benefits were associated with a marked diminution of levels of circulating inflammatory cytokines that are commonly elevated in myelofibrosis.

CONCLUSIONS:

INCB018424 was associated with marked and durable clinical benefits in patients with myelofibrosis for whom no approved therapies existed. (Funded by Incyte; ClinicalTrials.gov number, NCT00509899.)

• Authors: Srdan Verstovsek, Hagop Kantarjian, Ruben A Mesa, Animesh D Pardanani, Jorge Cortes-Franco, Deborah A Thomas, Zeev Estrov, Jordan S Fridman, Edward C Bradley, Susan Erickson-Viitanen, Kris Vaddi, Richard Levy, Ayalew Tefferi
• Journal: The New England journal of medicine (N Engl J Med) Vol. 363 Issue 12 Pg. 1117-27 (Sep 16 2010) ISSN: 1533-4406 [Electronic] United States
• PMID: 20843246 (Publication Type: Clinical Trial, Phase I, Clinical Trial, Phase II, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Biomarkers
• Cytokines
• Nitriles
• Pyrazoles
• Pyrimidines
• STAT3 Transcription Factor
• STAT3 protein, human
• ruxolitinib
• Janus Kinase 1
• Janus Kinase 2

Topics

• Adult
• Aged
• Aged, 80 and over
• Anemia (drug therapy, etiology)
• Biomarkers (blood)
• Cytokines (blood)
• Dose-Response Relationship, Drug
• Female
• Hepatomegaly (drug therapy, etiology)
• Humans
• Janus Kinase 1 (antagonists & inhibitors)
• Janus Kinase 2 (antagonists & inhibitors, genetics)
• Male
• Middle Aged
• Mutation
• Nitriles
• Primary Myelofibrosis (blood, complications, drug therapy, genetics)
• Pyrazoles (administration & dosage, adverse effects)
• Pyrimidines
• STAT3 Transcription Factor (drug effects, metabolism)
• Spleen (drug effects, pathology)