| dc.description.abstract | The World Health Organization (WHO) documents malaria as one of the leading causes of high
morbidity and mortality worldwide. The disease affects millions and kills thousands of people
annually. Efforts to reduce the global burden of malaria have prompted WHO to recommend
prevention strategies like using anti-malarial drugs and malaria vaccines. However, these strategies
have been ineffective because of anti-malarial drug resistance and the inefficacy of malaria
vaccines. The current recommended drug combination is Artemisinin-based Combination Therapy
(ACT). However, the extended ACTs clearance times, linked to the emergence of artemisinin
monotherapy resistance recorded most recently in Africa and the Great Mekong region, pose a
danger to its efficacy. Similarly, the RTS,S/AS01 (Mosquirix) vaccine’s modest effectiveness
against malaria at 36% among kids aged 5 to 17 months who need four doses, fails to aid malaria
eradication. To address the limitations of current anti-malarial therapies and vaccines, this study
aimed to: (1) identify novel PfHsp90 and PfCSP inhibitors with pharmacological activity against
Plasmodium malaria through hierarchical virtual screening (HVS) using geldanamycin and
monoclonal antibody L9 as reference ligands, respectively; (2) assess the stability of protein
inhibitor complexes via molecular dynamics simulations (MDS); and (3) validate the inhibitory
efficacy of selected compounds through in vitro assays. Since P. falciparum heat shock protein 90
(PfHsp90) and P. falciparum circumsporozoite surface protein (PfCSP) are well-characterized
malaria drugs and vaccines targets, respectively, this study sought to use them in discovering better
efficacious malaria drug and vaccine candidates. Geldanamycin (GDM), a potent Hsp90 inhibitor
with well-characterized binding to ATP-binding domain, was used to identify PfHsp90 inhibitors
by screening it against the ZINC20 database via the ZINCPHARMER web server. This virtual
screening process resulted in 17 hits. Monoclonal antibody (mAb) L9, with its high-affinity
binding to the central NANP repeat region, was used to identify PfCSP inhibitors, yielding 23 hits.
These ZINCPHARMER hits were subjected to drug-likeness and pharmacokinetics properties
analysis in the SwissADME web server, and 18 (9 for PfHsp90 and 9 for PfCSP) of them satisfied
the requirements. The 18 ZINC compounds were docked with PfHsp90 and PfCSP using the PyRx
software to understand their interactions. From the molecular docking results, ZINC09060002 (
8.2 kcal/mol), ZINC72133064 (-7.8 kcal/mol), ZINC72163401 (-7.7 kcal/mol), ZINC72358537 (
8.1 kcal/mol), and ZINC72358557 (-7.6 kcal/mol) had better binding affinities to PfHsp90 than
GDM (-7.5 kcal/mol). Similarly, ZINC25374360 (-8.1 kcal/mol), ZINC40144754 (-8.3 kcal/mol),
and ZINC71996727 (-8.9 kcal/mol) bound strongly to PfCSP with binding affinities of less than
8.0 kcal/mol. The stability of these molecularly docked protein-inhibitor complexes was assessed
through MDS using GROMACS 2022. The PfHsp90 inhibitors (ZINC72163401, ZINC72358537,
and ZINC72358557) and PfCSP inhibitors (ZINC25374360 and ZINC71996727) formed stable
complexes with their respective target proteins. These five compounds were subjected to in vitro
validation using the Sybr Green I fluorescence assay. Cultured P. falciparum parasites were
exposed to serial dilutions of each inhibitor, and parasite viability was quantified based on DNA
binding fluorescence intensity. IC₅₀ values were calculated to determine the inhibitory potency of
each compound. They showed promising inhibition of parasite growth with IC50 values ranging
between 5 – 150 ng/mL. In this regard, the three PfHsp90 inhibitors are anti-malarial candidates
while the two PfCSP inhibitors are potential vaccine adjuvants that might increase the efficacy of
the existing Mosquirix vaccine. However, further structural optimization studies and clinical (in
vivo) tests are necessary to ascertain the antimalarial activity of these compounds in humans. | en_US |
