Background: Drug therapy remains the principal management strategy for malaria but is increasingly challenged by the emergence of drug-resistant malaria parasites. The need for new antimalarial drugs is urgent, yet drug discovery and development are hindered by high costs, long durations, and safety concerns that prevent approval. The current study aimed to determine antiplasmodial activities of approved drugs in combination with artemether (ART) and lumefantrine (LU). Methods: Using the SYBR Green I assay test, this study investigated the efficacy of epirubicin (EPI) and pelitinib (PEL) combined with ART and LU at fixed drug–drug ratios (4:1, 3:1, 1:1, 1:2, 1:3 and 1:4) and volume/volume. These combinations, as well as single drug treatments, were tested against cultured strains of Plasmodium falciparum (W2, DD2, D6, 3D7 and F32-ART) and fresh and cultured clinical isolates. The fifty percent inhibition concentration (IC₅₀) and a mean sum of fifty percent fractional inhibition concentration (FIC₅₀) were determined. Results: Synergism was observed when EPI was combined with both ART and LU across all fixed ratios with a mean of mean FIC₅₀ values of 1) when tested against strains of P. falciparum and clinical isolates. Conclusions: This study underscores the utility of alternative drug discovery and development strategies to bypass cost, time, and safety barriers, thereby enriching the antimalarial drug pipeline and accelerating the transition from lab to market.

Malaria poses a substantial global health challenge, with the majority of instances concentrated in countries within Sub-Saharan Africa. A variety of antimalarial medications have been created to address the widespread occurrence of Plasmodium falciparum malaria. Since 2004, Artemisinin-based Combination Therapy (ACT) has been the primary treatment for uncomplicated malaria in Kenya. Nevertheless, there is a rising concern attributable to the increasing reports of ACT resistance, particularly in Southeast Asia, and its extension into Africa. In particular, mutations in the Kelch propeller domain on chromosome 13 (Pfk13) have been associated with resistance to ACT. However, our comprehension of mutation prevalence in Africa remains mostly unexplored, especially as slow parasite clearance becomes increasingly prevalent. In this study, we assess polymorphisms in the Plasmodium falciparum Kelch13 propeller gene among malaria non-responsive patients who attended selected hospitals in endemic regions of Kisii County, Kenya. The research found out that all participants experiencing delayed parasite clearance had low parasitemia levels (< 500) after completing the full dose of the ACT drug, as opposed to their parasitemia levels before taking the ACT drugs. The parasite density for all participants in the study who experienced delayed parasite clearance on the first day before taking the ACT drug showed a high mean ± SE of 13951.9 ± 3564.72. In contrast, during the third-day visit, the mean was notably lower at 327.90 ± 41.11, coinciding with their claim of not responding to the drug. Upon sequencing the K13-propeller gene of the isolates and conducting a search for synonymous and non-synonymous mutations in the propeller region of K13, no polymorphism was observed. Surprisingly, upon further investigation into the amino acids of the isolated samples, silent mutations were observed. Continued global surveillance of artemisinin resistance remains crucial, and our findings offer insights into the possible dissemination of resistant parasites in East Africa. These findings suggest that the detection of silent mutations particularly those associated with delayed parasite clearance following ACT, may imply a gradual emergence of ACT-resistant parasites. This warrants additional investigation through in-vitro assays to determine the functional significance of these findings.