Evaluation of phthalazinone phosphodiesterase inhibitors with improved activity and selectivity against Trypanosoma cruzi

Julianna Siciliano De Araújo, Patrícia Bernardino da Silva, Marcos Meuser Batista, Raiza Brandão Peres, Camila Cardoso-Santos, Titilola D. Kalejaiye, Jane C. Munday, Erik De Heuvel, Geert Jan Sterk, Koen Augustyns, Irene G. Salado, An Matheeussen, Iwan De Esch, Harry P. De Koning, Rob Leurs, Louis Maes, Maria de Nazaré Correia Soeiro

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BACKGROUND: Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi, needs urgent alternative therapeutic options as the treatments currently available display severe limitations, mainly related to efficacy and toxicity. OBJECTIVES: As phosphodiesterases (PDEs) have been claimed as novel targets against T. cruzi, our aim was to evaluate the biological aspects of 12 new phthalazinone PDE inhibitors against different T. cruzi strains and parasite forms relevant for human infection. METHODS: In vitro trypanocidal activity of the inhibitors was assessed alone and in combination with benznidazole. Their effects on parasite ultrastructural and cAMP levels were determined. PDE mRNA levels from the different T. cruzi forms were measured by quantitative reverse transcription PCR. RESULTS: Five TcrPDEs were found to be expressed in all parasite stages. Four compounds displayed strong effects against intracellular amastigotes. Against bloodstream trypomastigotes (BTs), three were at least as potent as benznidazole. In vitro combination therapy with one of the most active inhibitors on both parasite forms (NPD-040) plus benznidazole demonstrated a quite synergistic profile (xΣ FICI = 0.58) against intracellular amastigotes but no interaction (xΣ FICI = 1.27) when BTs were assayed. BTs treated with NPD-040 presented disrupted Golgi apparatus, a swollen flagellar pocket and signs of autophagy. cAMP measurements of untreated parasites showed that amastigotes have higher ability to efflux this second messenger than BTs. NPD-001 and NPD-040 increase the intracellular cAMP content in both BTs and amastigotes, which is also released into the extracellular milieu. CONCLUSIONS: The findings demonstrate the potential of PDE inhibitors as anti-T. cruzi drug candidates.

Original languageEnglish
Pages (from-to)958-967
Number of pages10
JournalJournal of antimicrobial chemotherapy
Issue number4
Early online date20 Dec 2019
Publication statusPublished - Apr 2020


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