Chiral Chromatographic Isolation on Milligram Scale of the Human African Trypanosomiasis Treatment d- and l-Eflornithine.

Mikael Boberg,Rasmus Jansson-Löfmark,Anna C Jonson,Michael Ashton,Hanna Leek

doi:10.1021/acsomega.0c03121

Mikael Boberg, Rasmus Jansson-Löfmark + Show 3 more

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https://doi.org/10.1021/acsomega.0c03121

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Journal: ACS omega	Publication Date: Sep 11, 2020
Citations: 7	License type: cc-by

Affiliation: University of Gothenburg, AstraZeneca (Sweden)

Abstract

Eflornithine is a recommended treatment against the otherwise fatal parasitic disease late stage human African trypanosomiasis (HAT), also known as Gambian sleeping sickness. It is administered repeatedly as a racemic mixture intravenously (IV) together with oral nifurtimox. Racemic eflornithine has been investigated in clinical trials for oral dosing. However, due to low systemic exposures at a maximum tolerated oral dose, the drug is continued to be administered IV. The eflornithine enantiomers, d- and l-eflornithine, have different affinities to the target enzyme ornithine decarboxylase, suggesting that the pharmacodynamics of the enantiomers may differ. The aim of this study was to develop a method for isolation of d- and l-eflornithine from a racemic mixture. Several chiral stationary phases (CSPs) were evaluated for enantioselectivity using supercritical fluid chromatography (SFC) or high-performance liquid chromatography (HPLC). None of the tested CSPs rendered separation of the enantiomers in SFC mode. Separation of the enantiomers with SFC on the CSP Chiralpak IG was only achieved on an analytical scale after derivatization with ortho-phthalaldehyde (OPA). This was the first reported enantioselective SFC method for an eflornithine derivate. However, due to poor stability, the eflornithine-OPA derivates degraded and no chemically pure enantiomers were obtained. The CSP that showed enantioselectivity in HPLC mode was Chirobiotic R, which resulted in a successful isolation on a semipreparative milligram scale. The isolated eflornithine enantiomers will be tested in nonclinical in vitro and in vivo studies to support and assess the feasibility of a future clinical program with an oral HAT treatment.

Highlights

The neglected tropical disease human African trypanosomiasis (HAT), known as sleeping sickness, threatens millions of people in sub-Saharan Africa.[1]
The nifurtimox−eflornithine combination therapy has been reported to be superior to other drugs against HAT as well as to eflornithine or nifurtimox monotherapy.[9−11] Eflornithine inhibits the enzyme ornithine decarboxylase (ODC) that is important for polyamine biosynthesis.[12,13]
A wide variety of chiral stationary phases (CSPs) and modifier combinations were evaluated in supercritical fluid chromatography (SFC) mode, none of them showed enantioselectivity for D- and L-eflornithine (Supplementary Table S1)

Summary

Introduction

The neglected tropical disease human African trypanosomiasis (HAT), known as sleeping sickness, threatens millions of people in sub-Saharan Africa.[1]. The active pharmaceutical ingredient eflornithine (Ornidyl), known as DL-α-difluoromethylornithine, is a recommended treatment in combination with nifurtimox (Lampit) for patients infected with T.b. gambiense that have reached the late stage of the disease. Both drugs are included in the WHO model list of essential medicines. Racemic eflornithine for oral dosing has been investigated in clinical trials.[14−28] due to poor systemic exposure at a maximum tolerated oral dose, the drug is continued to be administered IV. With an oral drug formulation of the potentially more potent L-eflornithine, it is conceivable that a therapeutic systemic exposure could be obtained at doses below the maximum tolerated oral dose of racemic eflornithine

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