Malaria persists to be a prominent medical concern and poses a profound impact on health and socio-economic well-being across the globe. Particularly prevalent in tropical and subtropical regions, this disease poses a significant threat to millions, causing thousands of deaths each year. The causative agent is the parasite of the genus Plasmodium, transmitted to humans through the bite of infected female Anopheles mosquitoes [1], [2]. Among the species that are known to infect humans, P. falciparum stands out as the most lethal, responsible for the majority of malaria-related fatalities. P. falciparum infections can lead to catastrophic outcomes, with cerebral malaria representing a life-threatening complication, especially among children [3]. Years of tiring efforts have yielded effective interventions, including insecticide-treated bed nets, insecticides sprays and Artemisinin-based combination therapies (ACTs) that have helped reduce the mortality rates in affected populations [4]. Unfortunately, the advent of COVID-19 pandemic, coupled with the emergence and spread of drug-resistant malarial parasites in numerous malaria-endemic regions, has cast a significant shadow over the progress made in combating this deadly infectious disease [2], [5]. Presently, Chloroquine (CQ), the most widely used anti-malarial drug, has become ineffective due to rapid spread of CQ resistant parasite to almost all malaria-endemic countries [6]. In the current scenario, Artemisinin and its derivatives are the most important class of anti-malarial drugs. Unfortunately, the appearance and clonal expansion of Artemisinin resistant parasite in several parts of the world is wreaking havoc on global malaria control program [7], [8], [9], [10], [11], [12], [13]. Another important drug usually used for treating uncomplicated multidrug-resistant P. falciparum and P. vivax infections is mefloquine [14], [15]. It is used not only for treating malaria but also as a chemoprophylactic agent to prevent the onset of this infection [16]. But the usefulness of mefloquine is hindered by the emergence and spread of mefloquine-resistant parasite [15], [17]. Given this alarming scenario, there is an urgent need to explore new avenues for the development of novel anti-malarial compounds or to reformulate the known therapeutic molecules using nanotechnology for enhanced delivery of these compounds to site of infection.

Consequently, encapsulation of drugs in nano-sized delivery vehicles, such as liposomes and nanoparticles is of immense importance for treating intracellular infections. Amidst all lipid based nanocarriers, liposome is preferred due to its biphasic nature that enables them to entrap both lipophilic and hydrophilic compounds and even buffer solutions [18], [19], [20]. Additionally, this approach holds promise in addressing the challenges posed by drug-resistant parasites and ensuring more effective treatment outcomes [21]. Furthermore, liposome based drug delivery vehicles have been shown to overcome drug resistance in case of various cancer types [22]. A recent report suggests that doxorubicin when administered in PEGylated liposomal formulation overcomes drug resistance in mouse model of breast cancer [23]. Similarly, paclitaxel loaded liposome overcomes drug resistance in lung cancer [24]. Moreover, it has also been shown that CQ when given in antibody conjugated targeted liposomes, treats CQ-resistant malaria in murine model [25]. Liposomal CQ has been found to increase the therapeutic and prophylactic potential of CQ in treating murine malaria [26]. PEGylated formulation of Artemisinin also exhibited improved anti-malarial action as compared to free Artemisinin in terms of treating P. berghei infected mice model [27]. Multiple research groups established that cationic liposomes composed of phosphatidylcholine and stearylamine have anti-parasitic activity towards a number of human pathogenic parasites like Trypanosoma [28], [29], [30], Leishmania [31], [32], [33] and human malaria causing parasite Plasmodium falciparum [34]. Liposomal formulation with other cationic lipids has also been found to be efficacious against Leishmania infection [35].

Considering these accumulating evidence, cationic liposomal formulations emerge as a promising avenue for enhancing the therapeutic potential and conquering the resistance. Therefore, in the present study we set out to evaluate the anti-malarial efficacy of various liposomal formulations of mefloquine, in comparison to free mefloquine against P. falciparum in culture and in mice model. Encouragingly, among the tested formulations, a cationic liposomal variant of mefloquine exhibited superior anti-plasmodial effects compared to both free mefloquine and other liposomal formulations. This cationic liposomal formulation of mefloquine was found to clear the parasite load effectively and improve the survival rates in animals afflicted with the lethal strain, P. berghei ANKA. Furthermore, treatment with this liposomal mefloquine formulation prevented the gross pathological alteration of vital organs (liver and spleen) and breakdown of blood brain barrier which are key pathological hallmarks of malaria. Altogether, our findings underscore the potential of nano-encapsulated mefloquine as a promising therapeutic in the treatment of malaria.