Milk has been used as a vehicle for the delivery of antimalarial drugs during clinical trials to test for a food effect and artefenomel (OZ439) showed enhanced oral bioavailability with milk. However, the nature of the interaction between milk and OZ439 in the gastrointestinal tract remains poorly understood. To understand the role of milk digestion on the solubilization of OZ439 and polymorphism, we conducted real-time monitoring of crystalline drug in suspension during in vitro intestinal lipolysis of milk containing OZ439 using synchrotron X-ray scattering. OZ439 formed an unstable solid-state intermediate free base form (OZ439-FB form 1) at intestinal pH and was partially solubilized by milk fat globules prior to lipolysis. Dissolution of the free base form 1 and recrystallization of OZ439 in a more stable polymorphic form (OZ439-FB form 2) occurred during in vitro lipolysis in milk. Simply stirring the milk/drug suspension in the absence of lipase or addition of lipase to OZ439 in a lipid-free buffer did not induce this polymorphic transformation. The formation of OZ439-FB form 2 was therefore accelerated by the solubilization of OZ439-FB form 1 during the digestion of milk. Our findings confirmed that although crystalline precipitates of OZ439-FB form 2 could still be detected after in vitro digestion, milk-based lipid formulations provided a significant reduction in crystalline OZ439 compared to lipid-free formulations, which we attribute to the formation of colloidal structures by the digested milk lipids. Milk may therefore be particularly suited as a form of lipid-based formulation (LBF) for coadministration with OZ439, from which both an enhancement in OZ439 oral bioavailability and the delivery of essential nutrients should result.

Over the last 15 years, the majority of malaria drug discovery and development efforts have focused on new molecules and regimens to treat patients with uncomplicated or severe disease. In addition, a number of new molecular scaffolds have been discovered which block the replication of the parasite in the liver, offering the possibility of new tools for oral prophylaxis or chemoprotection, potentially with once-weekly dosing. However, an intervention which requires less frequent administration than this would be a key tool for the control and elimination of malaria. Recent progress in HIV drug discovery has shown that small molecules can be formulated for injections as native molecules or pro-drugs which provide protection for at least 2 months. Advances in antibody engineering offer an alternative approach whereby a single injection could potentially provide protection for several months. Building on earlier profiles for uncomplicated and severe malaria, a target product profile is proposed here for an injectable medicine providing long-term protection from this disease. As with all of such profiles, factors such as efficacy, cost, safety and tolerability are key, but with the changing disease landscape in Africa, new clinical and regulatory approaches are required to develop prophylactic/chemoprotective medicines. An overall framework for these approaches is suggested here.

Milk is an attractive lipid-based formulation for the delivery of poorly water-soluble drugs to pediatric populations. We recently observed that solubilization of artefenomel (OZ439) during in vitro intestinal lipolysis was driven by digestion of triglycerides in full-cream bovine milk, reflecting the ability of milk to act as an enabling formulation in the clinic. However, when OZ439 was co-administered with a second antimalarial drug, ferroquine (FQ) the exposure of OZ439 was reduced. The current study therefore aimed to understand the impact of the presence of FQ on the solubilization of OZ439 in milk during in vitro intestinal digestion. Synchrotron small-angle X-ray scattering was used for in situ monitoring of drug solubilization (inferred via decreases in the intensity of drug diffraction peaks) and polymorphic transformations that occurred during the course of digestion. Quantification of the amount of each drug solubilized over time and analysis of their distributions across the separated phases of digested milk were determined using high-performance liquid chromatography. The results show that FQ reduced the solubilization of OZ439 during milk digestion, which may be due to competitive binding of FQ to the digested milk products. Interactions between the protonated FQ-H + and ionized liberated free fatty acids resulted in the formation of amorphous salts, which removes the low-energy crystalline state as a barrier to dissolution of FQ, while inhibiting the solubilization of OZ439. We conclude that although milk could enhance the solubilization of poorly water-soluble OZ439 during in vitro digestion principally due to the formation of fatty acids, the solubilization efficiency was reduced by the presence of FQ by competition for the available fatty acids. Assessment of the solubilization of both drugs during digestion of fixed-dose combination lipid formulations (such as milk) is important and may rationalize changes in bioavailability when compared to that of the individual drugs in the same formulation.

We couple Flash NanoPrecipitation and spray drying as a scalable and versatile platform to formulate and recover amorphous nanoparticles for controlled release of hydrophobic drugs.

BackgroundOZ439 is a new chemical entity which is active against drug-resistant malaria and shows potential as a single-dose cure. However, development of an oral formulation with desired exposure has proved problematic, as OZ439 is poorly soluble (BCS Class II drug). In order to be feasible for low and middle income countries (LMICs), any process to create or formulate such a therapeutic must be inexpensive at scale, and the resulting formulation must survive without refrigeration even in hot, humid climates. We here demonstrate the scalability and stability of a nanoparticle (NP) formulation of OZ439. Previously, we applied a combination of hydrophobic ion pairing and Flash NanoPrecipitation (FNP) to formulate OZ439 NPs 150 nm in diameter using the inexpensive stabilizer hydroxypropyl methylcellulose acetate succinate (HPMCAS). Lyophilization was used to process the NPs into a dry form, and the powder’s in vitro solubilization was over tenfold higher than unprocessed OZ439.MethodsIn this study, we optimize our previous formulation using a large-scale multi-inlet vortex mixer (MIVM). Spray drying is a more scalable and less expensive operation than lyophilization and is, therefore, optimized to produce dry powders. The spray dried powders are then subjected to a series of accelerated aging stability trials at high temperature and humidity conditions.ResultsThe spray dried OZ439 powder’s dissolution kinetics are superior to those of lyophilized NPs. The powder’s OZ439 solubilization profile remains constant after 1 month in uncapped vials in an oven at 50 °C and 75% RH, and for 6 months in capped vials at 40 °C and 75% RH. In fasted-state intestinal fluid, spray dried NPs achieved 80–85% OZ439 dissolution, to a concentration of 430 µg/mL, within 3 h. In fed-state intestinal fluid, 95–100% OZ439 dissolution is achieved within 1 h, to a concentration of 535 µg/mL. X-ray powder diffraction and differential scanning calorimetry profiles similarly remain constant over these periods.ConclusionsThe combined nanofabrication and drying process described herein, which utilizes two continuous unit operations that can be operated at scale, is an important step toward an industrially-relevant method of formulating the antimalarial OZ439 into a single-dose oral form with good stability against humidity and temperature.Electronic supplementary materialThe online version of this article (10.1186/s12967-019-1849-8) contains supplementary material, which is available to authorized users.