A Phase 1 Study of Pacritinib in Vacuoles, E1 Ubiqutin-activating Enzyme, X-linked, Autoinflammatory, Somatic (VEXAS) Syndrome

VEXAS (vacuoles, E1 ubiqutin-activating enzyme, X-linked, autoinflammatory, somatic syndrome) is a recently described disorder with severe hematologic and rheumatologic manifestations caused by somatic variants in the ubiquitin- activating enzyme gene, UBA1, that is acquired in hematopoietic progenitor cells. Patients are often debilitated by autoinflammatory symptoms and there is currently no standard of care available. There is a clinically unmet need for better therapies in VEXAS Syndrome. There have been no prospective clinical trials of JAK-I in VEXAS syndrome. The investigators hypothesize that pacritinib, as a JAK2/IRAK1 inhibitor with a manageable safety profile in myelofibrosis patients with thrombocytopenia, will improve the autoinflammatory and hematologic manifestations of VEXAS syndrome with a tolerable toxicity profile.

The investigators propose a single arm, pilot Phase 1 study evaluating the safety and tolerability of pacritinib in patients with VEXAS syndrome with an initial safety run-in phase of 6 patients treated with pacritinib 200mg twice daily (BID) on days 1-28 of a continuous 28 day cycle. If no more than 1 patient experiences a dose-limiting toxicity (DLT), the investigators will enroll an expansion cohort to gain additional toxicity and efficacy data, for a total enrollment of 15 patients. If more than 1 patient experiences a DLT during the safety run-in phase, the investigators will decrease the dose to 100 mg BID, and if no more than 1 of 6 patients experiences a DLT, the investigators will complete the expansion cohort as above for up to a total enrollment of 15 patients. If more than 1 patient experiences a DLT at 100 mg BID, the investigators will discontinue the study. Patients will be treated for up to 12 cycles.

Drug: Pacritinib