Momelotinib Dosing and Monitoring in Renal Impairment
No dose adjustment is required for momelotinib in patients with any degree of renal impairment, including severe renal dysfunction, as pharmacokinetic studies demonstrate no clinically significant changes in drug exposure across the full spectrum of kidney function. 1
Dosing Recommendations by Renal Function
Mild to Severe Renal Impairment (eGFR ≥15 mL/min/1.73 m²)
- Standard dose of 200 mg orally once daily should be used without modification 1
- Pharmacokinetic analysis showed no clinically significant differences in momelotinib or M21 metabolite exposure across eGFR values ranging from 16.4 mL/min/1.73 m² to above 120 mL/min/1.73 m² 1
- This finding was confirmed in a dedicated phase 1 study where subjects with moderate or severe renal impairment showed comparable plasma exposures to healthy controls 2
End-Stage Renal Disease on Dialysis
- The effect of dialysis on momelotinib pharmacokinetics is unknown 1
- Given that only <1% of unchanged momelotinib is excreted in urine (with 69% excreted in feces), and the drug is 91% protein-bound with a large volume of distribution (984 L), hemodialysis is not expected to enhance elimination 1
- In the absence of specific data, initiate at standard 200 mg once daily with close monitoring for adverse events, particularly peripheral neuropathy, dizziness, and cytopenias 1
Monitoring Parameters in Renal Impairment
Baseline Assessment
- Calculate creatinine clearance using Cockcroft-Gault formula rather than relying on serum creatinine alone, as serum creatinine is insufficient for evaluating renal function, particularly in elderly patients 3
- For patients with chronic kidney disease, eGFR estimation may be more accurate, though Cockcroft-Gault remains practical for drug dosing calculations 3
- Assess baseline complete blood count, as momelotinib can cause thrombocytopenia and neutropenia 1
Ongoing Monitoring
- Monitor renal function regularly, particularly in elderly patients who represent 75% of the myelofibrosis population treated with momelotinib 1
- Avoid coadministration of nephrotoxic drugs such as NSAIDs or COX-2 inhibitors, which can precipitate acute kidney injury in patients with baseline renal compromise 3
- Monitor for treatment-emergent adverse events, as the safety profile in renal impairment studies was similar to healthy controls 2
Key Pharmacokinetic Considerations
Metabolism and Excretion
- Momelotinib undergoes extensive hepatic metabolism via multiple CYP enzymes (CYP3A4 36%, CYP2C8 19%, CYP2C9 17%, CYP2C19 19%, CYP1A2 9%) 1
- Only 28% of radioactivity is excreted in urine (<1% as unchanged drug), with the majority (69%) excreted in feces 1
- The M21 metabolite, which has approximately 40% of parent drug activity, is excreted 12% in urine 1
- This predominantly hepatic clearance explains why renal impairment does not significantly affect drug exposure 2
Active Metabolite (M21)
- The M21 metabolite-to-parent AUC ratio ranges from 1.4 to 2.1, meaning metabolite exposure exceeds parent drug 1, 4
- Both momelotinib and M21 showed no clinically significant pharmacokinetic differences in renal impairment 1, 2
Clinical Pitfalls and Caveats
Do not reduce the dose based solely on renal function, as this may compromise efficacy in addressing splenomegaly, constitutional symptoms, and anemia—the three key therapeutic targets in myelofibrosis 4
Distinguish renal impairment from hepatic impairment: Unlike renal dysfunction, severe hepatic impairment (Child-Pugh C) requires dose reduction to 150 mg once daily due to a 97% increase in momelotinib AUC 1, 2
In elderly patients with renal impairment, no additional dose modifications beyond standard recommendations are needed, as age (range 28-92 years) did not affect pharmacokinetics 1
Monitor for drug interactions that may affect renal function indirectly: momelotinib inhibits BCRP, increasing rosuvastatin exposure by 170%, which could theoretically increase rhabdomyolysis risk in patients with renal impairment 1