Development and validation of a method for the analytical control of letermovir by high performance liquid chromatography coupled with UV-visible (HPLC-UV) within a chemotherapy preparation unit (UPC)

Introduction
Letermovir is an antiviral drug indicated for the prophylaxis of cytomegalovirus (CMV) reactivation and CMV disease in adult CMV-seropositive with allogeneic hematopoietic stem cell transplantion, at standard doses of 480 mg (without co- ciclosporin prescription) or 240 mg (with ciclosporin co-prescription).
In order to secure its preparation within the UPC, a qualitative and quantitative analytical release control of letermovir is implemented by HPLC coupled with a UV-visible detector.

Material and method
Letermovir is a ready-to-use solution of 20 mg/ml, to be diluted in a 0.9% NaCl bag of 250 ml, that is two possible concentrations (taking into account an overfilling of 18 ml of bags): 0.9 mg/ml and 1.8 mg/ml.
The analytical control of letermovir is set up on HPLC-UV by FIA (Flow Injection Analysis) direct injection. The analysis conditions are: a wavelength λ at 260 nm, a 50% water / 50% acetonitrile mobile phase, and a flow rate of 1.5 ml/min for an injection volume of 30 µL. The analysis time is 0.3 min and the temperature is 20°C.
A calibration range of 5 points (0.6; 1.0; 1.4; 1.8; 2.0 mg/ml) is carried out on 3 different days and associated with four quality control points (0.6 0.9; 1.2; 1.6 mg/ml) repeated 3 times. The validation of the method is carried out in accordance with the international guideline International Council for Harmonization (ICH) Q2 (R1) using the following criteria: linearity, accuracy, repeatability (intra-assay precision) and intermediate precision (between -day precision).

Results
The analytical method is linear for a range of concentrations from 0.6 to 2.0 mg/L, with a correlation coefficient greater than 0.95 (R² = 0.9995). It is also precise, with coefficients of variation obtained during repeatability and intermediate precision studies of less than 5% and 8%: 1.3% and 2.0% respectively. Finally, the method is accurate with a recovery rate between 97.0% and 99.9% (>90%).

Discussion and conclusion
The method has been validated according to the criteria of the international guideline ICH Q2 (R1). It is linear, precise and accurate. The analytical control of letermovir could thus be deployed routinely within our UPC in order to secure the drug circuit. The development and validation of the analytical control method by UV-Raman spectrometry (QCRx^®) has also been set up.

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