Discovery of 4-quinolinone derivatives as candidates for antimalarial development: in vitro, ex vivo and mechanism of action characterization

Author(s)

Juliana Oliveira de Souza

• Document type: Master's Dissertation
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT)
• Defense date: 2019-11-20

Examining board members

Rafael Victório Carvalho Guido; Marcos Leoni Gazarini Dutra; Rubens Lima do Monte Neto

• Advisor: Rafael Victório Carvalho Guido; Anna Caroline Campos Aguiar

Abstract

Malaria is a tropical disease that causes a considerable impact on the health and socioeconomical development of affected populations. The development of resistance to current treatments necessitates the rapid development of effective antimalarial drugs. Quinolinone derivatives with different substituents have shown potent antiplasmodial activity in the past. In this work, our goal was to synthesize and characterize a series of new 4-quinolinone derivatives synthesized in collaboration with Prof. Arlene Correa (UFSCar) and determine their potential as lead candidates for the development of new antimalarials. From 22 compounds tested, we found 9 active compounds (IC50 values between 0,15 and 8 μM). All active compounds demonstrated good safety profile when tested for hemolytic activity and against HepG2 cells in the MTT assay. Compounds 4, 7 and 22 were the most promising compounds encountered, with submicromolar potency (IC50 values of 0,47, 0,21 and 0,15 μM, respectively) and good tolerability in hepatoma cells (SI of >213, >476 and >667, respectively). The three compounds were assayed against a panel of resistant P. falciparum strains, and none showed any indication of cross resistance. We then investigated the susceptibility of P. falciparum and P. vivax clinical isolates obtained in the Amazon Region (Porto Velho, RO) against the inhibitors. Both compounds were active against P. falciparum in the submicromolar range (median IC50: 4, 0,58 μM; and 7, 0,49 μM). P. vivax isolates showed higher IC50 values than those observed against P. falciparum isolates (median IC50: 4, 3,3 μM; and 7, 1,5 μM).Using speed and stage of action evaluation, we demonstrated that these compounds have a slow mode of action that affects mainly the trophozoite stage of life of asexual development of the parasite. To evaluate the mechanism of action underlying this series, we tested the inhibitory activity of 4 and 7 against P. falciparum cytochrome bc1. We obtained IC50 values of 7,2 [5,1 - 8,0] μM and 0,5 [0,45 - 0,57] μM for these compounds (respective IS values of 0,92 and >120 relative to the bovine bc1).Compound 4 also demonstrated inhibitory activity against sexual parasite stages in the ookinete conversion inhibition assay (IC50 = 0,67 [0,59 - 0,75] μM). Combination assays performed with conventional antimalarials showed that compounds 4 and 7 had antagonistic combination profile when combined with cycloguanil, additive profile in combination with artesunate and atovaquone, and demonstrated synergistic combination with proguanil. Our results indicate that compound 7 is the most promising 4-quinolinone derivative of the series, with adequate parasitological profile for the discovery of a candidate for antiplasmodial lead compounds. (AU)

• FAPESP's process: 17/26679-0 - 4-Quinolone derivatives as antimalarial drug candidates: Antiplasmodial activity characterization in vitro, in vivo and of the mode of action
• Grantee: Juliana Oliveira de Souza
• Support Opportunities: Scholarships in Brazil - Master