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Bonnie A. Avery,Deepthi Pabbisetty,Lie Li,Abhisheak Sharma,Mahesh K. Gundluru,Amar G. Chittiboyina,John S. Williamson,Mitchell A. Avery 한국약제학회 2018 Journal of Pharmaceutical Investigation Vol.48 No.5
The ultimate goal of this study was to identify an orally active, affordable, potent and safe antimalarial drug based on the natural product artemisinin. During these efforts, a series of novel 7β-hydroxyartemisinin analogs were synthesized and characterized in vitro for their antimalarial activity against Plasmodium falciparum. Heterodimerization of 7β-hydroxyartemisinin provided the asymmetrical carbamate (ARB-89) while homodimerization provided the carbonate (ARB-92). These dimers were found to be highly active in vitro with an IC50 ≤ 0.50 nM against P. falciparum infected human red blood cells (RBC). For further development as potential antimalarial agents, a battery of in vitro and in vivo pharmacokinetic experiments was performed to distinguish the fate of the discovery compounds ARB-89 and ARB-92. Two UPLC-MS methods were developed and validated for the analysis of the compounds. Both ARB- 89 and ARB-92 exhibited moderate affinity (51 and 56%, respectively) to parasitized RBC, which is a perquisite for antimalarial activity. Following a single dose oral and intravenous pharmacokinetic study in rats, ARB-89 displayed a high clearance (92.8 ± 5.6 L/h kg), short elimination half-life ( t1/2, 1.2 ± 0.2 h) and moderate oral bioavailability (23.4%). ARB-89 was found to be excreted unchanged in feces, which may be due to its high lipophilicity, molecular weight and low oral exposure. In an attempt to identify a better lead antimalarial compound, ARB-92 was designed to be more water soluble than ARB-89 by incorporating a protonatable tertiary amine as part of the dimerizing ligand for 7β-hydroxyartemisinin. As anticipated, ARB-92 displayed a lower clearance (2.9 ± 0.7 L/h kg) and subsequently a longer t1/ 2 (2.3 ± 0.2 h) compared to ARB-89. The oral bioavailability of ARB-92 was found to be 34% in rats, a value somewhat better than the marketed artemisinin derivatives artenimol (19.3%), artemether (19.7%) or artesunate (29.5%).
Biochemical Properties of a Novel Cysteine Protease of <i>Plasmodium vivax</i> , Vivapain-4
Na, Byoung-Kuk,Bae, Young-An,Zo, Young-Gun,Choe, Youngchool,Kim, Seon-Hee,Desai, Prashant V.,Avery, Mitchell A.,Craik, Charles S.,Kim, Tong-Soo,Rosenthal, Philip J.,Kong, Yoon Public Library of Science 2010 PLoS neglected tropical diseases Vol.4 No.10
<▼1><P><B>Background</B></P><P>Multiple cysteine proteases of malaria parasites are required for maintenance of parasite metabolic homeostasis and egress from the host erythrocyte. In <I>Plasmodium falciparum</I> these proteases appear to mediate the processing of hemoglobin and aspartic proteases (plasmepsins) in the acidic food vacuole and the hydrolysis of erythrocyte structural proteins at neutral pH. Two cysteine proteases, vivapain (VX)-2 and VX-3 have been characterized in <I>P. vivax</I>, but comprehensive studies of <I>P. vivax</I> cysteine proteases remain elusive.</P><P><B>Findings</B></P><P>We characterized a novel cysteine protease of <I>P. vivax</I>, VX-4, of which orthologs appears to have evolved differentially in primate plasmodia with strong cladistic affinity toward those of rodent <I>Plasmodium</I>. Recombinant VX-4 demonstrated dual substrate specificity depending on the surrounding micro-environmental pH. Its hydrolyzing activity against benzyloxycarbonyl-Leu-Arg-4-methyl-coumaryl-7-amide (Z-Leu-Arg-MCA) and Z-Phe-Arg-MCA was highest at acidic pH (5.5), whereas that against Z-Arg-Arg-MCA was maximal at neutral pH (6.5–7.5). VX-4 preferred positively charged amino acids and Gln at the P1 position, with less strict specificity at P3 and P4. P2 preferences depended on pH (Leu at pH 5.5 and Arg at pH 7.5). Three amino acids that delineate the S2 pocket were substituted in VX-4 compared to VX-2 and VX-3 (Ala90, Gly157 and Glu180). Replacement of Glu180 abolished activity against Z-Arg-Arg-MCA at neutral pH, indicating the importance of this amino acid in the pH-dependent substrate preference. VX-4 was localized in the food vacuoles and cytoplasm of the erythrocytic stage of <I>P. vivax</I>. VX-4 showed maximal activity against actin at neutral pH, and that against <I>P. vivax</I> plasmepsin 4 and hemoglobin was detected at neutral/acidic and acidic pH, respectively.</P><P><B>Conclusion</B></P><P>VX-4 demonstrates pH-dependent substrate switching, which might offer an efficient mechanism for the specific cleavage of different substrates in different intracellular environments. VX-4 might function as a hemoglobinase in the acidic parasite food vacuole, a maturase of <I>P. vivax</I> plasmepsin 4 at neutral or acidic pH, and a cytoskeleton-degrading protease in the neutral erythrocyte cytosol.</P></▼1><▼2><P><B>Author Summary</B></P><P><I>Plasmodium vivax</I> affects hundreds of millions each year and results in severe morbidity and mortality. Plasmodial cysteine proteases (CPs) play crucial roles during the progression of malaria since inhibition of these molecules impairs parasite growth. These CPs might be targeted for new antimalarial drugs. We characterized a novel <I>P. vivax</I> CP, vivapain-4 (VX-4), which appeared to evolve differentially among primate <I>Plasmodium</I> species. VX-4 showed highly unique substrate preference depending on surrounding micro-environmental pH. It effectively hydrolyzed benzyloxycarbonyl-Leu-Arg-4-methyl-coumaryl-7-amide (Z-Leu-Arg-MCA) and Z-Phe-Arg-MCA at acidic pH and Z-Arg-Arg-MCA at neutral pH. Three amino acids (Ala90, Gly157 and Glu180) that delineate the S2 pocket were found to be substituted in VX-4. Alteration of Glu180 abolished hydrolytic activity against Z-Arg-Arg-MCA at neutral pH, indicating Glu180 is intimately involved in the pH-dependent substrate preference. VX-4 hydrolyzed actin at neutral pH and hemoglobin at acidic pH, and participated in plasmepsin 4 activation at neutral/acidic pH. VX-4 was localized in the food vacuoles and cytoplasm of the erythrocytic stage of <I>P. vivax</I>. The differential substrate preferences depending on pH suggested a highly efficient mechanism to enlarge biological implications of VX-4, including hemoglobin degradation, maturation of plasmepsin, and remodeling of the parasite architecture during growth and development of <I>P. vivax</I>.</P></▼2>
Oh, Seikwan,Moon, Hyung-In,Jung, Jae-Chul,Avery, Mitchell A. Walter de Gruyter GmbH 2008 Zeitschrift für Naturforschung. B, A journal Vol.63 No.11
<B>Abstract</B><P> A simple synthesis, involving a key coupling reaction, and the biological activity of the title compounds 16 and 17 are described. The key fragments are the amine·HCl salt 6 and the acids 9 and 13, which were smoothly coupled by using ethyl(dimethylaminopropyl)carbodiimide (EDCI) and 1- hydroxybenzotriazole (HOBt) in high yield.We have found that the in vitro growth inhibitory potency of the new compounds 16 and 17 exhibits good histone deacetylase (HDAC) activity.</P>
Lim, Yong,Kim, Tack-Joong,Jin, Yong-Ri,Kim, Dong-Woon,Kwon, Jin-Sook,Son, Ju-Hee,Jung, Jae-Chul,Avery, Mitchell A,Son, Dong Ju,Hong, Jin Tae,Yun, Yeo-Pyo Williams Wilkins 2007 The Journal of Pharmacology and Experimental Thera Vol.321 No.2
<P>The abnormal proliferation of vascular smooth muscle cells (VSMCs) in arterial walls is an important pathogenetic factor of vascular disorders such as atherosclerosis and restenosis after angioplasty. Epothilone B, a novel potential antitumor compound, has a potent effect on preventing postangioplasty restenosis. Therefore, we established an in vivo rat carotid injury model and examined the potential effects of epothilone B on cardiovascular disease. We found that epothilone B potently prevented neointimal formation and in vivo VSMCs proliferation. In addition, we also showed that epothilone B significantly inhibited 5% fetal bovine serum (FBS)- and 50 ng/ml platelet-derived growth factor (PDGF)-BB-induced proliferation and cell cycle progression in rat aortic VSMCs. Furthermore, FBS and PDGF-BB induced the activations of extracellular signal-regulated kinases 1 and 2, Akt, phospholipase C gamma 1, and PDGF-receptor beta chain tyrosine kinase were not changed by epothilone B. However, epothilone B treatment caused a significant decrease in the level of cyclin-dependent protein kinase (CDK) 2, whereas it caused no change in the levels of cyclin E and down-regulated the phosphorylation of retinoblastoma, which plays a critical role in cell cycle regulation. Furthermore, levels of p27, an inhibitor of cyclin E/CDK2 complex, were significantly increased in VSMCs treated with epothilone B, indicating that this might be a major molecular mechanism for the inhibitory effects of epothilone B on the proliferation and cell cycle of VSMCs. These findings suggest that epothilone B can inhibit neointimal formation via the cell cycle arrest by the regulation of the cell cycle-related proteins in VSMCs.</P>