Development and validation of ion-pairing HPLC-CAD chromatography for measurement of Islatravir’s phosphorylated intermediates

Biocatalytic processes have become more prevalent in the pharmaceutical industry, leading to analytical challenges not faced when characterizing more traditional synthetic routes. A novel one-pot biocatalytic process has been established for Islatravir, an HIV reverse transcriptase translocation inhibitor for the treatment and prevention of HIV-1. As a one-pot reaction, the Islatravir chemistry contains multiple intermediates that are not isolated. Additionally, these unisolated intermediates have no chromophores, making traditional LC-UV techniques ineffective for characterization. A hydrophilic interaction chromatography (HILIC) method with a charged aerosol detector (CAD) was initially developed, however numerous inorganic species present in the one-pot reaction were retained; this led to co-elution of compounds and poor peak shapes. An innovative ion-pairing LC method was developed in order to resolve inorganic species, intermediates, and the API, for use during in-process control of the Islatravir biocatalytic reaction. Aided by a volatile ion-pairing reagent compatible with the CAD, this method successfully retains and resolves the highly polar intermediates of interest and Islatravir API. This novel method was successfully validated and has allowed the Islatravir biocatalytic process to be fully characterized from the early intermediates through the final API within the one-pot reaction without the need for isolations. This novel ion-pairing HPLC-CAD technique lays the groundwork for method development on current and future biocatalytic-produced drug substances.