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On the Single-Crystal Structure of Tenofovir Alafenamide Mono-Fumarate: A Metastable Phase Featuring a Mixture of Co-Crystal and Salt

Authors :
Jian-Wei Wang
Lu Liu
Ka-Xi Yu
Hong-Zhen Bai
Jun Zhou
Wen-Hua Zhang
Xiurong Hu
Guping Tang
Source :
International Journal of Molecular Sciences, Vol 21, Iss 23, p 9213 (2020)
Publication Year :
2020
Publisher :
MDPI AG, 2020.

Abstract

Tenofovir alafenamide (TAF) is a prodrug of tenofovir as a potent nucleotide reverse transcriptase inhibitor. It serves as the key component of Genvoya® for the first-line treatment of human immunodeficiency virus infection (HIV) and is the active component of Vemlidy® for the treatment of chronic hepatitis B. Vemlidy® is also a monotherapeutic regimen formulated as TAF hemifumarate (1; TAF:fumarate = 2:1). In this work, we report for the first time the single-crystal structure of TAF fumarate hemihydrate (2, TAF:fumarate:H2O = 2:2:1). Compound 2 is initially documented as a salt in which one proton of the fumaric acid migrates to the amine group of the adenine moiety in TAF. It was recently proposed that ca. 20–30% proton is transferred to the N atom on the aromatic adenine backbone. We herein provide definitive single-crystal X-ray diffraction results to confirm that 2, though phase pure, is formed as a mixture of co-crystal (75%) and salt (25%). It features two pairs of TAF fumarates, wherein one of the four H atoms on the fumaric acid is transferred to the N atom of the adjacent adenine moiety while the other three carboxylates remain in their intrinsic acid form. Compound 2 is a metastable phase during the preparation of 1 and can be isolated by halting the reaction during the refluxing of TAF and fumaric acid in acetonitrile (MeCN). Our report complements the previous characterizations of TAF monofumarate, and its elusive structural patterns are finally deciphered.

Details

Language :
English
ISSN :
14220067 and 16616596
Volume :
21
Issue :
23
Database :
Directory of Open Access Journals
Journal :
International Journal of Molecular Sciences
Publication Type :
Academic Journal
Accession number :
edsdoj.9d141e49f6034bc5aad49a22954b3c53
Document Type :
article
Full Text :
https://doi.org/10.3390/ijms21239213