Design, Synthesis and Trypanocidal Activity of Cruzain Reversible-Covalent Inhibitors

Author(s)

Lorenzo Cianni

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2019-11-22

Examining board members

Carlos Alberto Montanari; Michael Gütschow; Luiz Juliano Neto; Maria Luiza Vilela Oliva

• Advisor: Carlos Alberto Montanari

Abstract

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, remains a serious health problem due to inadequate therapy and lack of an effective vaccine. New drugs that are safe and efficient are therefore critically needed. Cruzain (Cz), the main T. cruzi cysteine protease (CP), is an essential enzyme for the life cycle of the parasite and has been used as a viable target for the search and identification of new chemical entities (NCE) acting as trypanocidal agents. Recent literature results demonstrate that reversible covalent Cz inhibitors can block the cell differentiation steps in the parasite and kill it.To this end, by applying a knowledge-based design approach, we have designed and synthesized a new series of dipeptidyl nitrile inhibitors of Cz aimed at leveraging the S3/P3 interactions, understand the role of the cyclopropyl in the bimolecular recognition process and map the S1/S1´ to enhance affinity and selectivity over other CPs. Herein, we report three new Cz inhibitors (Neq0940, Neq0938 and Neq0877)being equipotent with Benznidazole (the only current drug used to treat Chagas disease in Brazil) with SI (selective index) ratio over 20 (respect to the host cell) and therefore making them attractive synthetic targets for further in vivo testing against the acute form of Chagas disease. Dipeptidyl nitrile bioisostere inhibitors are under preclinical investigation as trypanocidal agents. Therefore, we performed the synthesis and structure-activity relationship (SAR) investigation of nitrile-based Cz inhibitors incorporating a trifluoroethylamine moiety as P3/P2 amide replacement. Results display three new one-digit (Neq0642, Neq0643, and Neq0659) nanomolar Cz inhibitors with high selectivity over CatL. Also, this works reveals that the effects of configuration at the P3/P2 amide replacement and different substitution in P1 lead to strong nonadditivity outcome. The bioisosteric exchange by a sulfonamide moiety on P3/P2 resulted in a new series of inhibitors that was evaluated on a panel of infectious and human CPs. Data displays an interesting flat SAR for Cz while disclosing strong CatS inhibition with high selectivity for other mammalian CPs (CatB, CatK, and CatL). SAR investigation also includes the effects of the nitrile electrophilic group by including alternative warheads. Inhibition constants represented by aldehydes and nitrile azadipeptides are two orders of magnitude larger for the best Cz inhibitors. Besides, the nitrile azadipeptide Cz inhibitor (Neq0690) was used in the first generation of Leishmania mexicana CPB (LmCPB) high-resolution x-Ray crystal structure. (AU)

• FAPESP's process: 16/07946-5 - Synthesis and evaluation of trypanocidal activity of potential reversible covalent inhibitors of cruzain enzyme
• Grantee: Lorenzo Cianni
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)