# Folinic Acid Prophylaxis and Dose Adjustments Enable Safe Treatment with Pemetrexed in Patients with Renal Impairment

## TL;DR

Pemetrexed can be safely used in patients with kidney problems when given with folinic acid and adjusted doses, offering effective cancer treatment to those previously excluded.

## Contribution

A safe dosing strategy for pemetrexed in patients with renal impairment using folinic acid prophylaxis and dose adjustments.

## Key findings

- Pemetrexed was safely administered to patients with renal impairment using dose adjustments and folinic acid.
- Adverse events were comparable to those in patients with normal kidney function.
- Treatment resulted in responses including complete and partial remissions in some patients.

## Abstract

Pemetrexed is a cornerstone in chemo(immunotherapy) of non‐small cell lung cancer and mesothelioma; however, it is contraindicated in patients with renal impairment due to severe toxicity concerns. Therefore, a large proportion of patients is withheld from effective chemo(immunotherapy). We performed an intra‐patient 3 + 3 dose escalation renal impairment study (eGFR < 45 mL/min). The pemetrexed dose was calculated based on renal function to reach a target AUC, and patients received oral folinic acid prophylaxis 45 mg four times daily on Days 2–15 of each cycle. Endpoints included safety (incidence of hematological and non‐hematological toxicity, treatment delays) and pharmacokinetics in line with regulatory guidance for renal impairment trials. Six patients with an estimated glomerular filtration rate (eGFR) between 26 and 41 mL/min were included. All patients were successfully escalated to the full dose. Adverse event patterns and pharmacokinetics were comparable to those in patients with normal renal function. Grade I/II anemia occurred in five patients (already present at baseline). One occurrence of grade IV neutropenia was observed, which resolved without intervention. Moreover, in three patients, a 1‐week treatment delay occurred. Treatment resulted in a response in four patients (n = 1 complete response, n = 2 partial response, n = 1 stable disease). Pemetrexed can be safely administered in patients with impaired renal function when the dose is calculated based on renal function and folinic acid prophylaxis is administered, thereby enabling an effective treatment modality for patients that, thus far, could not be treated.