Ruxolitinib (Jakafi) — Clinical FAQs

Q: What are the most common side effects of Ruxolitinib?

The most commonly reported side effects of Ruxolitinib (≥10% incidence) include: Thrombocytopenia (≥70% in MF), Anemia (≥80% in MF), Neutropenia, Bruising / ecchymosis, Dizziness and others (12 total). Consult your oncologist for complete prescribing information.

Q: Does Ruxolitinib have a black box warning?

Yes. Ruxolitinib carries FDA black box warning(s) regarding: 1. Serious infections including bacterial, mycobacterial (TB), fungal, and viral infections (HBV reactivation, PML caused by JC virus) — screen for TB and hepatitis B before initiating; monitor for signs of infection throughout therapy

Q: Is Ruxolitinib safe during pregnancy?

Ruxolitinib pregnancy safety: Category D equivalent (Pregnancy Category not formally assigned post-2015 labeling). Animal studies demonstrate embryo-fetal toxicity. Women of reproductive potential should use effective contraception during therapy. Breastfeeding is not recommended.. Oncologists should review the complete prescribing information and discuss reproductive risks with patients before initiating therapy.

Question 1

What is Ruxolitinib FDA-approved to treat?

Accepted Answer

Ruxolitinib is FDA-approved for the following oncology indications: 1. Intermediate or high-risk myelofibrosis (primary, post-PV, or post-ET MF) — approved Nov 2011 (COMFORT-I and COMFORT-II trials) 2. Polycythemia vera in patients with inadequate response or intolerance to hydroxyurea — approved Dec 2014 (RESPONSE trial) 3. Acute graft-versus-host disease (aGVHD) in patients ≥12 years refractory to steroids — approved May 2019 (REACH2 trial) 4. Chronic graft-versus-host disease (cGVHD) after failure of ≥1 prior line — approved Sep 2021 (REACH3 trial).

Question 2

How does Ruxolitinib work (mechanism of action)?

Accepted Answer

Ruxolitinib is a potent, selective inhibitor of Janus kinase 1 (JAK1) and JAK2 that competitively blocks ATP binding at the kinase active site. Inhibition of JAK1/JAK2 disrupts downstream STAT3 and STAT5 phosphorylation, suppressing cytokine-driven myeloproliferation and inflammatory signaling. This results in reduction of splenomegaly, constitutional symptoms, and aberrant hematopoietic progenitor proliferation characteristic of myeloproliferative neoplasms.

Question 3

How is Ruxolitinib administered?

Accepted Answer

Ruxolitinib is administered Oral (PO). For myelofibrosis: starting dose 20 mg PO BID (platelets >200×10⁹/L), 15 mg BID (platelets 100–200×10⁹/L), or 5 mg BID (platelets 50–<100×10⁹/L); titrate based on response and tolerability.

Question 4

What are the most common side effects of Ruxolitinib?

Accepted Answer

The most commonly reported side effects of Ruxolitinib (≥10% incidence) include: Thrombocytopenia (≥70% in MF), Anemia (≥80% in MF), Neutropenia, Bruising / ecchymosis, Dizziness and others (12 total). Consult your oncologist for complete prescribing information.

Question 5

Does Ruxolitinib have a black box warning?

Accepted Answer

Yes. Ruxolitinib carries FDA black box warning(s) regarding: 1. Serious infections including bacterial, mycobacterial (TB), fungal, and viral infections (HBV reactivation, PML caused by JC virus) — screen for TB and hepatitis B before initiating; monitor for signs of infection throughout therapy

Question 6

Is Ruxolitinib safe during pregnancy?

Accepted Answer

Ruxolitinib pregnancy safety: Category D equivalent (Pregnancy Category not formally assigned post-2015 labeling). Animal studies demonstrate embryo-fetal toxicity. Women of reproductive potential should use effective contraception during therapy. Breastfeeding is not recommended.. Oncologists should review the complete prescribing information and discuss reproductive risks with patients before initiating therapy.

Ruxolitinib — Drug Monograph

Mechanism of Action

FDA Indications

Common Side Effects

Clinical Pearl

Related Therapies & Mechanisms