Artemisinins are known for their low aqueous solubility and resultant poor and erratic absorption upon oral administration. The poor solubility and erratic absorption usually translate, to low bibavailability. Enzymatic degradation and physiological barriers are also amongst the challenges which must be overcome to ensure effective delivery. Artemisininbased monotherapy and combination therapies are essential for the management and treatment of uncomplicated as well as cerebral malaria. Artemisone and artemiside are novel artemisinin derivatives, their antimalarial activity/efficacy was evaluated in vitro and in vivo in the presence and absence of Pheroid™ technology. Pheroid™ technology is a patented drug delivery system which has the ability to capture, transport and deliver pharmacologically active compounds. Pharmacokinetic models were also constructed for artemis one and artemiside, both in the presence and absence of Pheroid™ technology. Results obtained with the jn vitro antimalarial activity evaluation indicated that artemiside was slightly more potent than artemisone and much more potent than artesunate. Artemiside had IC50 values of 0.54 ± 0.03 nM (reference) and 0.10 ± 0.05 nM (Pheroid™) (p = 0.009) while artemisone had values of 0.94 ± 0.04 nM (reference) and 0.21 ± 0.04 nM (Pheroid™) (p = 0.0001). Artesunate had IC50 values of 29.65 ± 0.05 nM (reference) and 10.20 ± 0.04 nM (Pheroid™) (p < 0.0001). Results obtained with the in vivo antimalarial activity evaluation indicated that artemisone led to more favourable treatment outcomes than artemiside. The Peters' 4-day suppressive test was used as a basis model. With artemisone treatment recrudescence occured at 16 days post infection at a dose of 20.0 mg/kg bodyweight and at 12 days post infection at 2.5 mg/kg bodyweight. With artemiside recrudescence occurred at 8 days post infection with both the 10.0 mg/kg and 2.5 mg/kg bodyweight treatment regimens. When comparing the antimalarial effect of the drugs with and without Pheroid™ technology there was no significant difference in terms of parasite reduction or in the achieved treatment outcomes of either compounds. The pharmacokinetic parameters were evaluated in a mouse model where C57 BL6 mice were used. The compounds were administered at a dose of 50.0 mg/kg bodyweight via an oral gavage tube at a volume of 200 µl. Blood samples were collected by means of tail bleeding. Sensitive and selective LC/MS/MS methods were developed to analyze the drug concentrations in the plasma samples. The relative bioavailability of artemisone was RA = 1.0 (reference) and RA = 4.57 (Pheroid™) (p < 0.001). The absolute bioavailability was calculated as F = 0.10 (reference) and F = 0.48(Pheroid™) (p < 0.001). The boiavailability of artemiside was not dramatically enhanced by the Pheroid™ delivery system. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2010.

Artemisinins are known for their low aqueous solubility and resultant poor and erratic absorption upon oral administration. The poor solubility and erratic absorption usually translate, to low bibavailability. Enzymatic degradation and physiological barriers are also amongst the challenges which must be overcome to ensure effective delivery. Artemisininbased monotherapy and combination therapies are essential for the management and treatment of uncomplicated as well as cerebral malaria. Artemisone and artemiside are novel artemisinin derivatives, their antimalarial activity/efficacy was evaluated in vitro and in vivo in the presence and absence of Pheroid™ technology. Pheroid™ technology is a patented drug delivery system which has the ability to capture, transport and deliver pharmacologically active compounds. Pharmacokinetic models were also constructed for artemis one and artemiside, both in the presence and absence of Pheroid™ technology. Results obtained with the jn vitro antimalarial activity evaluation indicated that artemiside was slightly more potent than artemisone and much more potent than artesunate. Artemiside had IC50 values of 0.54 ± 0.03 nM (reference) and 0.10 ± 0.05 nM (Pheroid™) (p = 0.009) while artemisone had values of 0.94 ± 0.04 nM (reference) and 0.21 ± 0.04 nM (Pheroid™) (p = 0.0001). Artesunate had IC50 values of 29.65 ± 0.05 nM (reference) and 10.20 ± 0.04 nM (Pheroid™) (p < 0.0001). Results obtained with the in vivo antimalarial activity evaluation indicated that artemisone led to more favourable treatment outcomes than artemiside. The Peters' 4-day suppressive test was used as a basis model. With artemisone treatment recrudescence occured at 16 days post infection at a dose of 20.0 mg/kg bodyweight and at 12 days post infection at 2.5 mg/kg bodyweight. With artemiside recrudescence occurred at 8 days post infection with both the 10.0 mg/kg and 2.5 mg/kg bodyweight treatment regimens. When comparing the antimalarial effect of the drugs with and without Pheroid™ technology there was no significant difference in terms of parasite reduction or in the achieved treatment outcomes of either compounds. The pharmacokinetic parameters were evaluated in a mouse model where C57 BL6 mice were used. The compounds were administered at a dose of 50.0 mg/kg bodyweight via an oral gavage tube at a volume of 200 µl. Blood samples were collected by means of tail bleeding. Sensitive and selective LC/MS/MS methods were developed to analyze the drug concentrations in the plasma samples. The relative bioavailability of artemisone was RA = 1.0 (reference) and RA = 4.57 (Pheroid™) (p < 0.001). The absolute bioavailability was calculated as F = 0.10 (reference) and F = 0.48(Pheroid™) (p < 0.001). The boiavailability of artemiside was not dramatically enhanced by the Pheroid™ delivery system. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2010.

Malaria is one the world’s most devastating diseases. Several classes of drugs are used to treat malaria. Artemisinin combination therapy is the first line treatment of uncomplicated malaria. The artemisinin derivative, artemisone in conjunction with the Pheroid® drug delivery system, is the focus of this thesis. The impact of the Pheroid® on the bioavailability of artemisone was evaluated in vervet monkeys. The resulting artemisone plasma levels were much lower (Cmax of 47 and 114 ng/mL for reference and Pheroid® test formulations respectively) than expected for the dosages administered (60 mg/kg). The Pheroid® improved the pharmacokinetic profile of artemisone in a clinically significant manner. The metabolism of artemisone was assessed in vitro by using human and monkey liver and intestinal microsomes, and recombinant CYP3A4 enzymes. The Pheroid® inhibits the microsomal metabolism of artemisone. In addition, there is a species difference in artemisone metabolism between man and monkey since the in vitro intrinsic clearance of the reference formulation with monkey liver microsomes is ~8 fold higher in the monkey liver microsomes compared to the human liver microsomes and the estimated in vivo hepatic clearance for the monkey is almost twofold higher than in humans. Artemisone has potent antimalarial activity. Its in vitro efficacy was approximately twofold higher than that of either artesunate or dihydroartemisinin when evaluated against P. falciparum W2, D6, 7G8, TM90-C2B, TM91-C235 and TM93-C1088 parasite strains. The Pheroid® drug delivery system did not improve or inhibit the in vitro efficacy of artemisone or DHA. Artemisone (reference and Pheroid® test formulations) and metabolite M1 abruptly arrested the growth of P. falciparum W2 parasites and induced the formation of dormant ring stages in a manner similar to that of DHA. Interaction of artemisone with the p-glycoprotein (p-gp) efflux transporter was investigated. Artemisone stimulates ATPase activity in a concentration-dependent manner, whereas the Pheroid® inhibited this p-gp ATPase activity. P-gp ATPase activity stimulation was fourfold greater in human than cynomolgus monkey MDR1 expressed insect cell membranes. Artemisone alone and artemisone entrapped in Pheroid® vesicles showed moderate apical to basolateral and high basolateral to apical permeability (Papp) across Caco-2 cells. The Papp efflux ratio of artemisone and artemisone entrapped in Pheroid® vesicles were both >5, and decreased to ~1 when the p-gp inhibitor, verapamil, was added. Therefore, artemisone is a substrate for mammalian p-gp. The cytotoxic properties of Pheroid® on Caco-2 cells were assessed and the pro-Pheroid® seems to be non-toxic at concentrations of 1.25%. Vervet monkey plasma caused antibody-mediated growth inhibition of P. falciparum. Heat inactivated or protein A treatment proved useful in the elimination of the growth-inhibitory activity of the drug-free plasma. Plasma samples containing artemisone could not be analysed by the ex-vivo bioassay method. The dual labelling ROS assay did not prove to be useful in the evaluation of ROS production by artemisone and the Pheroid® delivery system. In conclusion, entrapment of artemisone in the Pheroid® delivery system improves the pharmacokinetic properties of artemisone, but does not improve or inhibit its antimalarial efficacy in vitro. The Pheroid® inhibited both the microsomal metabolism of artemisone and P-gp ATPase activity and was shown to be non-toxic at clinically usable concentrations. / PhD (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

Malaria is one the world’s most devastating diseases. Several classes of drugs are used to treat malaria. Artemisinin combination therapy is the first line treatment of uncomplicated malaria. The artemisinin derivative, artemisone in conjunction with the Pheroid® drug delivery system, is the focus of this thesis. The impact of the Pheroid® on the bioavailability of artemisone was evaluated in vervet monkeys. The resulting artemisone plasma levels were much lower (Cmax of 47 and 114 ng/mL for reference and Pheroid® test formulations respectively) than expected for the dosages administered (60 mg/kg). The Pheroid® improved the pharmacokinetic profile of artemisone in a clinically significant manner. The metabolism of artemisone was assessed in vitro by using human and monkey liver and intestinal microsomes, and recombinant CYP3A4 enzymes. The Pheroid® inhibits the microsomal metabolism of artemisone. In addition, there is a species difference in artemisone metabolism between man and monkey since the in vitro intrinsic clearance of the reference formulation with monkey liver microsomes is ~8 fold higher in the monkey liver microsomes compared to the human liver microsomes and the estimated in vivo hepatic clearance for the monkey is almost twofold higher than in humans. Artemisone has potent antimalarial activity. Its in vitro efficacy was approximately twofold higher than that of either artesunate or dihydroartemisinin when evaluated against P. falciparum W2, D6, 7G8, TM90-C2B, TM91-C235 and TM93-C1088 parasite strains. The Pheroid® drug delivery system did not improve or inhibit the in vitro efficacy of artemisone or DHA. Artemisone (reference and Pheroid® test formulations) and metabolite M1 abruptly arrested the growth of P. falciparum W2 parasites and induced the formation of dormant ring stages in a manner similar to that of DHA. Interaction of artemisone with the p-glycoprotein (p-gp) efflux transporter was investigated. Artemisone stimulates ATPase activity in a concentration-dependent manner, whereas the Pheroid® inhibited this p-gp ATPase activity. P-gp ATPase activity stimulation was fourfold greater in human than cynomolgus monkey MDR1 expressed insect cell membranes. Artemisone alone and artemisone entrapped in Pheroid® vesicles showed moderate apical to basolateral and high basolateral to apical permeability (Papp) across Caco-2 cells. The Papp efflux ratio of artemisone and artemisone entrapped in Pheroid® vesicles were both >5, and decreased to ~1 when the p-gp inhibitor, verapamil, was added. Therefore, artemisone is a substrate for mammalian p-gp. The cytotoxic properties of Pheroid® on Caco-2 cells were assessed and the pro-Pheroid® seems to be non-toxic at concentrations of 1.25%. Vervet monkey plasma caused antibody-mediated growth inhibition of P. falciparum. Heat inactivated or protein A treatment proved useful in the elimination of the growth-inhibitory activity of the drug-free plasma. Plasma samples containing artemisone could not be analysed by the ex-vivo bioassay method. The dual labelling ROS assay did not prove to be useful in the evaluation of ROS production by artemisone and the Pheroid® delivery system. In conclusion, entrapment of artemisone in the Pheroid® delivery system improves the pharmacokinetic properties of artemisone, but does not improve or inhibit its antimalarial efficacy in vitro. The Pheroid® inhibited both the microsomal metabolism of artemisone and P-gp ATPase activity and was shown to be non-toxic at clinically usable concentrations. / PhD (Pharmaceutics), North-West University, Potchefstroom Campus, 2014