Title : Identification of multitargeting compounds against Plasmodium falciparum kinases: An approach to overcoming drug resistance in malaria therapy
The continuous drug resistance in parasites against the majority of the front-line antimalarials has resulted in countless deaths in malaria-endemic countries, with an estimated 619,000 deaths in 2021. Notably, the recent malaria outbreak during 2020–21 at Attapeu (Laos) can primarily be attributed to the rise of drug resistance. Hence, there is a pressing urgency for new strategies in the current antimalarial drug development process to overcome the rapidly emerging drug resistance problem. Among the various approaches, the multitargeting drug discovery approach may seem promising to address drug resistance issues with benefits like increased efficacy, improved safety profile, and the requirement of fewer pills compared to traditional single and combinational drugs. Studies indicated that the possibility of evolving mutations in multiple targets simultaneously is extremely low as it would significantly compromise the parasite's fitness cost. Interestingly, among the 361 FDA-approved new molecular entities from both 2000- 15 and 2015-17, multitargeting drugs accounted for approximately 55-60% and 21%, respectively. The past decade has witnessed a substantial rise in publications on multitargeting drugs, revealing a rising interest and recognition of multitarget drug discovery and development. Among the various drug targets, kinases are an essential druggable class of enzymes, playing a key role in multiple parasite life cycle stages. The 35- 60% sequence identity between malaria kinases and their mammalian counterparts suggests the potential for selective inhibition. In our study, we used the structure-based drug designing approach to predict multitarget inhibitors against six chemically validated Plasmodium falciparum kinases, including GMP- Dependent Protein Kinase (PfPKG), Calcium-dependent protein kinase 4 (PfCDPK4), Mitogen-Activated Protein Kinase 2 (PfMAP2), protein kinase 5 (PfPK5), thymidylate kinase (PfTMK), and phosphatidyl inositol 4- kinase (PfPI4K), which resulted in 21 multitargeting hits. The molecular dynamic simulation of the top six complexes (Quercetin-CDPK4, Myricetin-MAP2, Quercetin-PKG, Salidroside-PI4K, Myricetin-TMK, and Salidroside-PK5) showed stable microscopic interactions. Moreover, hierarchical clustering revealed the structural divergence of the 21 compounds from the existing antimalarials, indicating less chance of cross- resistance. Additionally, the top three hits were validated through parasite growth inhibition assays, with quercetin and myricetin exhibiting an IC50 value of 1.84 µM and 3.93 µM, respectively.