# Transfer of amenamevir into breast milk in breastfeeding patients with recurrent herpes simplex: study protocol for a single-arm, open-label study

## TL;DR

This study will measure how much of the drug amenamevir passes into breast milk to assess its safety for infants during breastfeeding.

## Contribution

The study introduces a protocol to evaluate amenamevir's transfer into breast milk during patient-initiated therapy for RHS.

## Key findings

- The study will determine amenamevir concentrations in breast milk using liquid chromatography-mass spectrometry.
- The primary outcome will be the relative infant dose calculated from drug concentration data.
- If the relative infant dose is under 10%, amenamevir may become a standard therapy for breastfeeding patients with RHS.

## Abstract

Recurrent herpes simplex (RHS) is a disease caused by reactivation of the herpes simplex virus. Patients with RHS are treated with anti-herpes virus medication. Amenamevir is one such medication used for RHS in Japan and is administered as patient-initiated therapy (PIT); this involves initiation at the discretion of the patient, based on early symptoms. However, there are insufficient data on the transfer of amenamevir into breast milk among breastfeeding patients with RHS.

This study aims to assess the transfer of amenamevir into breast milk and evaluate the infant's risk of drug exposure.

This study is a single-arm, open-label, interventional multicenter study. Patients who experience RHS during breastfeeding will be recruited and treated with amenamevir. The concentration of amenamevir in breast milk will be determined by liquid chromatography-mass spectrometry. The primary outcome is relative infant dose (RID) calculated by Cave[AUC(0–24 h)]. The secondary outcome is RID calculated by Cmax and Cave[AUC(0–48 h)].

This study will provide evidence of the transfer profile of amenamevir into breast milk during PIT. If the RID of amenamevir is less than 10%, such therapy is generally considered to be safe, and use of PIT with amenamevir may consequently lead to a new standard therapy for breastfeeding patients.