A study found that “pacritinib may offer a unique survival advantage” for patients with myelofibrosis (MF) and thrombocytopenia who achieve any spleen volume reduction (SVR).
The study was led by Helen Ajufo, MD, of Washington University School of Medicine in St. Louis, Missouri, and published in the European Journal of Haematology.
Previous retrospective analyses have tied SVR to improved overall survival (OS) in patients treated with ruxolitinib with platelets >100 × 109/L. This post-hoc landmark analysis sought to assess the connection between SVR and pacritinib versus best available therapy (BAT), including ruxolitinib, in patients with MF with platelets ≤100 × 109/L.
The researchers utilized a cohort from the randomized, controlled, multicenter, phase 3 PERSIST-2 study. Included patients received pacritinib 200 mg twice daily (n=89) or BAT (n=84; 39 received ruxolitinib). The following SVR thresholds were used to define responders and nonresponders:
• ≥35%
• ≥20%
• ≥10%
• >0%
Most patients (n=65; 73%) in the pacritinib arm achieved SVR ≥10%, which demonstrated the greatest separation in OS curves between responders and nonresponders (HR, 0.00; 95% CI, 0.00-0.14; P<0.01). SVR ≥0% and ≥20% were also associated with improved OS in the pacritinib cohort.
By week 12, SVR was not associated with survival regardless of the threshold in the BAT cohort. Just 33% (n=28) of BAT-treated patients achieved SVR ≥10%, most of whom (n=23; 82%) were on ruxolitinib.
The authors noted that the study is limited by the clinical hold imposed during the PERSIST-2 study, which required all patients to immediately discontinue study treatment and limited the duration of follow-up and time on treatment.
“This analysis shows that achieving an SVR with pacritinib, but not BAT, including ruxolitinib, is associated with an OS benefit in patients with MF and thrombocytopenia,” the authors concluded.
The study was funded by CTI Biopharma Corp., a Sobi Company.
Reference
Ajufo H, Bewersdorf JP, Harrison C, et al. Pacritinib response is associated with overall survival in myelofibrosis: PERSIST-2 landmark analysis of survival. Eur J Haematol. 2025;114(2):238-247. doi:10.111/ejh.14321
