Phase I evaluation of XL019, an oral, potent, and selective JAK2 inhibitor

Area of Science:

• Oncology
• Pharmacology
• Neuroscience

Background:

• Myelofibrosis is a serious bone marrow disorder.
• JAK2 inhibitors are a therapeutic target for myelofibrosis.
• Understanding the safety and efficacy profile of novel JAK2 inhibitors is crucial.

Purpose of the Study:

• To evaluate the safety and tolerability of XL019, a selective JAK2 inhibitor.
• To assess the pharmacokinetic profile of XL019.
• To explore preliminary efficacy signals in patients with myelofibrosis.

Main Methods:

• Phase I clinical trial design.
• Dose escalation cohorts (100, 200, 300 mg) of XL019 administered orally.
• Monitoring for adverse events, particularly neurotoxicity.
• Pharmacokinetic assessments including terminal half-life and time to steady state.
• Evaluation of International Working Group defined responses.

Main Results:

• All 30 patients with myelofibrosis experienced central and/or peripheral neurotoxicity.
• Neurotoxicity necessitated dose reduction and ultimately led to study termination.
• Peripheral neuropathy resolved in 50% of patients; central neurotoxicity resolved in all patients post-therapy.
• Minimal myelosuppression was observed.
• XL019 demonstrated a terminal half-life of approximately 21 hours.
• Three patients (10%) achieved International Working Group defined responses.

Conclusions:

• XL019 exhibits significant neurotoxicity in myelofibrosis patients, limiting its therapeutic potential.
• Despite neurotoxicity, XL019 showed minimal myelosuppression and some efficacy.
• Further investigation into managing or mitigating XL019-induced neurotoxicity is warranted.