Drug Resistance in <i>Plasmodium falciparum</i>: Molecular Mechanisms, Adaptive Tolerance, and Implications for Malaria Control

Abstract

Context: Artemisinin-based combination therapies (ACTs) are increasingly threatened by the emergence of Plasmodium falciparum strains that exhibit both genetic resistance and adaptive drug tolerance, thereby undermining global malaria control efforts. Evidence Acquisition: This structured narrative review synthesized studies published between January 2013 and January 2025, identified through PubMed/MEDLINE, Scopus, Web of Science, Embase, and World Health Organization repositories. The final database search was conducted on January 15, 2025. Search strings combined controlled vocabulary (MeSH/Emtree) and free-text terms related to P. falciparum, antimalarial resistance, artemisinin and partner-drug resistance, and key resistance loci. A total of 847 records were identified; after the removal of 203 duplicates, 644 records underwent title and abstract screening, and 126 articles met the eligibility criteria and were included in the synthesis. The manuscript presents 23 representative citations. Historical background and post-search contextual sources were distinguished from the included search corpus. The lead author screened all titles and abstracts, and a secondary reviewer independently assessed a randomly selected 20% subset (κ = 0.89). Eligible studies reported molecular mechanisms, cellular adaptations, clinical resistance markers, or genomic analyses of resistant P. falciparum. Data were synthesized thematically by drug class and mechanistic pathway, with critical appraisal focused on methodological transparency and biological plausibility. Results: Contemporary resistance encompasses mutations in drug transporters (pfcrt, pfmdr1), target-site modifications (dhfr, dhps), and kelch13 propeller variants associated with ring-stage survival. The independent emergence of partial artemisinin resistance in Africa has now been documented, driven by local kelch13 mutations and reinforced by stress-response pathways, including proteostatic buffering and redox adaptation. Susceptibility to the partner drugs lumefantrine, piperaquine, and amodiaquine is concurrently declining, often against a background of entrenched antifolate resistance. Resistance architectures are polygenic and context dependent and are shaped by transmission intensity, host immunity, and unregulated drug use. Conclusions: Single-marker surveillance no longer captures clinically relevant resistance. Integrating genomic monitoring with functional tolerance assays is essential for early detection. Drug development should prioritize compounds that disrupt stress-response and quiescence pathways. Treatment policies would benefit from incorporating molecular early-warning indicators to preserve the efficacy of first-line regimens.