Inrebic (Fedratinib)

Inrebic targets the JAK‑STAT signaling pathway that drives myeloproliferative neoplasms. It is approved for the following conditions:

• Primary myelofibrosis: reduces spleen size and alleviates disease‑related symptoms.
• Post‑polycythemia vera myelofibrosis: improves hematologic parameters and quality of life.
• Post‑essential thrombocythemia myelofibrosis: decreases splenomegaly and symptom burden.

• Fedratinib selectively inhibits Janus kinase 2 (JAK2), a key enzyme in cytokine signaling pathways that regulate hematopoiesis. By blocking JAK2 activity, the drug diminishes downstream STAT activation, leading to reduced proliferation of malignant myeloid cells and decreased inflammatory cytokine production associated with myelofibrosis.

Adverse reactions to Inrebic may vary in frequency and severity.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Diarrhea: watery stools, often self‑limiting.
• Fatigue: persistent tiredness affecting daily activities.
• Anemia: reduced red blood cell count.
• Thrombocytopenia: lowered platelet levels.
• Vomiting: occasional episodes after dosing.

Serious or Rare Side Effects

• Wernicke encephalopathy: neurological syndrome requiring immediate attention.
• Severe infections: heightened risk due to immunosuppression.
• Hepatic toxicity: elevated liver enzymes or liver injury.
• Cardiac failure: signs of reduced cardiac function.
• Tumor lysis syndrome: metabolic disturbances in high‑risk patients.
• Severe neutropenia: markedly low neutrophil count increasing infection risk.

Before initiating Inrebic, clinicians should consider several safety measures.

• Monitor blood counts: perform regular CBC to detect anemia, thrombocytopenia, or neutropenia.
• Assess liver function: periodic LFTs are recommended.
• Evaluate neurological status: watch for early signs of Wernicke encephalopathy.
• Avoid in patients with known hypersensitivity to fedratinib or its excipients.
• Store at ambient temperature: keep in the original container, protect from moisture and light.

Fedratinib may interact with other medicines, requiring careful management.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): can markedly increase fedratinib exposure.
• Concomitant use with other JAK inhibitors: may cause additive myelosuppression.
• Live vaccines: increased risk of infection due to immunosuppression.

Moderate Interactions (Monitor Closely)

• Moderate CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce fedratinib plasma levels.
• Anticoagulants (e.g., warfarin): monitor for altered bleeding risk.
• Antifungal azoles (e.g., fluconazole): may modestly raise fedratinib concentrations.