# Pacritinib

Source: https://onco.cc/drugs/pacritinib/  
OnCo record `pacritinib` (Treatment). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The JAK inhibitor for myelofibrosis patients whose platelet counts are too low for ruxolitinib.

## Summary

Pacritinib inhibits JAK2 and FLT3 while sparing JAK1, and also blocks IRAK1 and ACVR1, the receptor that drives hepcidin production; because it spares JAK1 it causes less myelosuppression and can be used when platelet counts are too low for ruxolitinib. In PERSIST-2 it produced spleen and symptom responses in myelofibrosis patients with platelets below 100 x 10^9/L, including those below 50, and it received accelerated approval in 2022 for intermediate or high-risk myelofibrosis with platelets below 50 x 10^9/L. ACVR1 inhibition lowers hepcidin and may improve anaemia. Diarrhoea is the main adverse event. PACIFICA is the confirmatory trial needed to convert accelerated approval into full approval, and its role in patients with higher platelet counts is unsettled. For a newcomer: the myelofibrosis JAK inhibitor for people whose platelets are dangerously low.

## Fields

- Kind: Treatment
- Status: approved
- Last checked: 2026-09-08
- Tags: gap-fill
- Brand: Vonjo
- Modality: Small-molecule JAK2/IRAK1/ACVR1 inhibitor
- Mechanism: Inhibits JAK2 and FLT3 while sparing JAK1, plus IRAK1 and ACVR1 (hepcidin pathway), allowing use with very low platelets.
- Approvals: US 2022: Intermediate/high-risk myelofibrosis with platelets <50×10⁹/L

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Pacritinib
- Label (DailyMed): https://dailymed.nlm.nih.gov/dailymed/search.cfm?labeltype=all&query=pacritinib

## Connected records

- cancers: [Myeloproliferative neoplasms (PV, ET, myelofibrosis)](https://onco.cc/cancers/myeloproliferative-neoplasms/), [Primary myelofibrosis](https://onco.cc/cancers/primary-myelofibrosis/)
- technologies: [Small-molecule kinase inhibitors](https://onco.cc/technologies/kinase-inhibitors/)
- targets: [ACVR1 (ALK2)](https://onco.cc/targets/acvr1/), [FLT3](https://onco.cc/targets/flt3/), [IRAK1](https://onco.cc/targets/irak1/), [JAK1](https://onco.cc/targets/jak1/), [JAK2](https://onco.cc/targets/jak2/)
- companies: [Sobi (Swedish Orphan Biovitrum)](https://onco.cc/companies/sobi/)
- trials: [Pacritinib vs. Hydroxyurea in Advanced Proliferative Chronic Myelomonocytic Leukemia](https://onco.cc/trials/nct07033598/)
- key papers: [COMFORT-I: ruxolitinib, the first JAK inhibitor, versus placebo for myelofibrosis](https://onco.cc/key-papers/paper-comfort-1-ruxolitinib-myelofibrosis-nejm-2012/), [MOMENTUM: momelotinib versus danazol for myelofibrosis patients with anaemia after a prior JAK inhibitor](https://onco.cc/key-papers/paper-momentum-momelotinib-lancet-2023/)
- terms: [DIPSS, DIPSS-plus and MIPSS70 (myelofibrosis risk scores)](https://onco.cc/terms/dipss-mipss70/)

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