Tetrahydrophthalazinone Inhibitor of Phosphodiesterase with In Vitro Activity against Intracellular Trypanosomatids

Abstract

The phosphodiesterase inhibitor tetrahydrophthalazinone NPD-008 was explored by phenotypic in vitro screening, target validation and ultrastructural approaches against Trypanosoma cruzi. NPD-008 displayed activity against different forms and strains of T. cruzi (EC50 = 6.6 – 39.5 μM), increased cAMP levels of T. cruzi and its combination with Bz gave synergistic interaction. It was also moderately active against intracellular amastigotes of Leishmania amazonensis and L. infantum, confirming a potential activity profile as an antitrypanosomatid drug candidate.

Perspectives for a new drug candidate for Chagas disease therapy

“…Against bloodstream trypomastigotes, NPD-008 reached an EC 50 of 6.6 ± 1.1 μM after 24 h incubation, being twice as active than Bz (EC 50 , 12.9 ± 1.9 μM). 43 The combo NPD-008 plus Bz gave a synergistic and no interaction profile for bloodstream and amastigotes with ΣFICI values of 0.51 and 1.19, respectively, as already noticed for other phthalazinone PDE inhibitor such as NPD-040. 42 These data are very promising since combined therapy is a valuable tool in improving treatment efficacy while reducing dose levels and toxicity and preventing the development of drug resistance.…”

“… 46 Ultrastructural analysis of drug-treated bloodstream trypomastigotes showed cellular changes consistent with autophagy and osmotic stress, mechanisms already previously linked to cAMP signaling as also observed for other PDE inhibitors. 42 , 43 , 44 , 45 , 46 Compound 9 raised both cellular and supernatant cAMP levels, confirming inhibition of T. cruzi PDE(s).…”

“… 42 Another phosphodiesterase inhibitor, the tetrahydrophthalazinone named NPD-008 was investigated upon T. cruzi in vitro . 43 NPD-008 was active against different forms and strains of T. cruzi (EC 50 : 6.6 to 39.5 mM) and triggered cAMP levels in treated parasites. Against bloodstream trypomastigotes, NPD-008 reached an EC 50 of 6.6 ± 1.1 μM after 24 h incubation, being twice as active than Bz (EC 50 , 12.9 ± 1.9 μM).…”

“…The bulk of our results support the further investigation of PDE inhibitors as anti- T. cruzi agents as it represents a successful repurposing of research into inhibitors of mammalian PDEs. 42 , 43 , 44 , 45 , 46 …”