12/16/2024
According to data from an ongoing multicenter, open-label phase 1/2a trial, the addition of the pan-lysyl oxidase inhibitor PXS-5505 to standard Janus kinase (JAK) inhibitor therapy demonstrated safety and potential efficacy for patients with intermediate or high-risk myelofibrosis (MF).
Peter T Tan, MBSS, One Clinical Research Pty Ltd, Nedlands, Australia presented these findings at the 2024 American Society of Hematology (ASH) Annual Meeting & Exposition in San Diego, California.
Previous dose escalation and cohort expansion of PXS-5505 trial phases have established safety and tolerability of a monotherapy dose of 200 mg BID over 24 weeks in patients with MF. Researchers evaluated the safety and efficacy of a 200 mg BID dose of PXS-5505 as an add-on to standard JAK2 inhibitor, ruxolitinib (RUX), therapy among patients with MF.
Enrolled in the study were patients with MF with a Dynamic International Prognostic Scoring System (DIPPS) score of intermediate-2/high risk disease. Before initial PXS-5505 administration, patients had been under current RUX treatment for 12 or more weeks, with a stable dose for at least 8 weeks. A bone marrow biopsy was completed within 3 months of start date for all patients. Patients received PXS-5505 for 52 weeks or until progressive disease, dose limiting toxicity, or unacceptable toxicity. Dosage of PXS-5505 remained consistent at 200 mg BID, however patients were entitled to change RUX dose or discontinue RUX therapy while continuing to receive PXS-5505.
In this add-on phase of the trial, 15 patients were included, of which 6 had primary MF, 2 had post-ET MF, 7 patients had post-PV MF, 3 patients were considered high risk, and all other patients were Int-2. Among patients, the median duration of RUX treatment was 26 months (range, 3.5-74) and a median of 58 months (range 6.5-120) since time of MF diagnosis. The median myeloproliferative neoplasms symptom asssessment form total symptom score (PMN-SAF TSS) was 22.5. The median baseline spleen volume was 1353 cm3 (n=14) and medial baseline hemoglobin was 94 g/dL.
Additionally, 11 patients had hemoglobin levels over 100 g/dL at baseline and almost half had platelet levels below 100×109/L, 2 of which were transfusion-dependent at the start of the study. Baseline mutation profiles for 11 patients revealed a JAK2 V617F mutation among 7 patients and 6 patients with more than 1 high risk mutation.
“The results from this trial using a novel combination of PXS-5505 and RUX will add to the existing safety profile of PXS-5505 and provide preliminary indicators of efficacy to help inform future investigations of PXS-5505 in patients with MF,” the researchers concluded.