PXS-5505 in advanced MF: Results of a phase I/IIa trial

Results from a multicenter, phase I/IIa trial (NCT04676529) evaluating PXS-5505, a novel pan-lysyl oxidase inhibitor, in patients with primary, post-polycythemia vera or post-essential thrombocythemia myelofibrosis (MF) who had relapsed on, were refractory to, or were ineligible for Janus kinase inhibitor treatment (N = 27), were recently published in Haematologica by Vachhani et al. 

Key data: In the dose-escalation phase, PXS-5505 200 mg twice daily achieved robust systemic reduction of lysyl oxidase activity and the majority of adverse events were Grade 1–2; therefore, this dose was selected for the cohort-expansion phase (CEP). In the CEP, 92% of treatment-emergent adverse events were not related to PXS-5505 treatment and most were mild. PXS-5505 reached steady-state concentrations by Day 28 and demonstrated preliminary indications of clinical efficacy, including a reduction in bone marrow collagen. 

Key learning: PXS-5505 demonstrated favorable safety and pharmacokinetic properties, with preliminary indications of clinical efficacy, supporting continued investigation of PXS-5505 for patients with advanced MF.