At the 2022 American Society of Hematology Annual Meeting, researchers presented long-term follow-up results of a phase II study of ruxolitinib in patients with myeloproliferative neoplasms (MPNs). The analysis focused on splanchnic vein thrombosis (SVT), which is frequently associated with MPN. The researchers found that many patients were still on treatment at a median follow-up of 8.6 years. The drug still had significant effects on symptoms and splenomegaly with no recurrent thrombosis or gastrointestinal bleeding.
The original study included 21 patients with MPN-associated SVT, and it found that ruxolitinib was safe and effective in reducing spleen volume at 24 weeks. Patients who tolerated the drug well (n=18) entered an extension of the study for long-term follow-up of about 72 weeks, or until the drug was no longer effective or toxicity occurred.
As of June 30, 2022, 15 (71%) of those patients were still receiving ruxolitinib. Of those, 11 (73%) maintained their spleen response, and the rest maintained stable spleen volume without any splenomegaly progression. Five of the patients (33%) were still experiencing clinical complete response, and 12 (80%) were still having hematologic complete response. All patients were free of any disease-related symptoms, and no one experienced gastrointestinal or other bleeding or thrombotic events.
The researchers also reported safety data at long-term follow-up. Serious adverse events included second cancer (n=2), pneumonia (n=1), pleural effusion (n=1), encephalopathy (n=1), inguinal hernia (n=1), abdominal pain (n=1), sepsis (n=1), and increased international normalized ratio (n= ). Grade 3 adverse events were limited to thrombocytopenia (n=2) and an increase in creatine phosphokinase (n=1). All other adverse events were grade ≤2, with the most common being anemia (56%), thrombocytopenia (44%), leukopenia (39%), and herpes zoster reactivation (26%).
The researchers also explored molecular response via serial measurements of JAK2V617F variant allele frequency: Five patients had no response, four achieved partial molecular response, and one patient had a deep molecular response. Molecular responses were associated with hematologic and clinical improvements, noted the authors, led by Chiara Paoli, PhD, of the Center of Research and Innovation of Myeloproliferative Neoplasms at the University of Florence in Italy.
Reference
Paoli C, Guglielmelli P, Mannelli F, et al. Long term follow-up of an investigator-initiated phase 2 study of ruxolitinib in MPN-associated splanchnic vein thrombosis (SVT-RUXO). Abstract #3042. Presented at the 64th American Society of Hematology Annual Meeting, December 10-13, 2022; New Orleans, Louisiana.