Artemisinin-dipeptidyl vinyl sulfone hybrid molecules: Design, synthesis and preliminary SAR for antiplasmodial activity and falcipain-2 inhibition

Abstract

A series of artemisinin-vinyl sulfone hybrid molecules with the potential to act in the parasite food vacuole via endoperoxide activation and falcipain inhibition was synthesized and screened for antiplasmodial activity and falcipain-2 inhibition. All conjugates were active against the Plasmodium falciparum W2 strain in the low nanomolar range and those containing the Leu-hPhe core inhibited falcipain-2 in low micromolar range. Keywordsantimalarial; artemisinin; FP-2; Vinylsulfone Artemisinin, 1, a sesquiterpene lactone isolated from the Artemisia annua Chinese herb, and its analogues (e.g. artemether, 2, arteether, 3, and artesunate, 4) were a major breakthrough in malaria chemotherapy because they produce a very rapid therapeutic response, particularly against multidrug-resistant Plasmodium falciparum malaria. 1,2 Despite the rapid clearance of parasites, the short half-lives of these compounds lead to many late recrudescences after monotherapy. 3 Thus, artemisinin-based combination therapy (ACT) has now been recommended by the World Health Organisation as standard therapy for falciparum malaria. 4 Cysteine proteases from malaria parasites are of particular interest as therapeutic targets due to their role in parasite development. 5 P. falciparum expresses four cysteine proteases from the papain family known as falcipains, of which falcipain-2 (FP-2) 6,7 and falcipain-3 (FP-3) 7,8 are the most relevant as therapeutic targets. Peptidyl vinyl sulfones, e.g. 5, are potent irreversible inhibitors of falcipains, acting as Michael acceptors of the catalytic cysteine residue. 9 Falcipain inhibitors have been shown to inhibit the development of cultured erythrocytic parasites by blocking the hydrolysis of host hemoglobin and to cure mice infected with lethal malaria infections. 10 *Corresponding authors: Phone: +351217946476; Fax: +35 1217946470; fclopes@ff.ul.pt. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptA concern regarding the use of protease inhibitors as antimalarials is that selection of drugresistant mutants will eventually occur. Indeed, parasites resistant to a dipeptidyl vinyl sulfone have been selected in the laboratory, although this resistance was somewhat unstable. 11 Thus, dipeptidyl vinyl sulfones are obvious candidates for combination antimalarial therapy as a strategy to retard the development of resistance. This information prompted us to design artemisinin-vinyl sulfone hybrid molecules with the potential to help prevent multi-drug resistance in P. falci...

Toward the discovery of inhibitors of babesipain-1, a Babesia bigemina cysteine protease: in vitro evaluation, homology modeling and molecular docking studies

“…In vitro inhibition studies Both HEDICINS 1 and HECINS 2 were evaluated in vitro for inhibition of babesipain-1, using a fluorimetric method [13,14], as described under ''Experimental''. Close inspection of data obtained (Table 1, columns 3 and 7), and comparison with the falcipain inhibitory activities reported in [15] for the same compounds, shows the following:…”

“…might become relevant targets for improving the control of bovine babesiosis. Moreover, babesipain-1 was recently found to be inhibited by artemisinin-vinyl sulfone hybrid molecules, which had been previously reported as inhibitors of Plasmodium falciparum cysteine proteases, falcipains, and to effectively inhibit the growth of P. falciparum cultured parasites [13,14]. This finding paves the way for the rescuing of antimalarial compounds as potential anti-babesiosis agents, thus turning falcipain inhibitors as good starting points for the development of babesipain-1 inhibitors.…”

“…Insoluble inclusion bodies were washed with urea buffer, and the resulting denatured and reduced GSTbabesipain-1 protein was refolded and later acidified to promote auto-activation to an active form. Babesipain-1 activity was assayed by a fluorimetric method as previously described [13,14]. Briefly, assays were carried out in 200 lL assay buffer (10 mM PBS, pH 7.4, 5 mM DTT) containing 20 lL of babesipain-1 activated in assay buffer at 50 lg/mL, and 5 lL of each concentration of the tested inhibitors.…”

<i>In silico</i> Design of Phosphonic Arginine and Hydroxamic Acid Inhibitors of <i>Plasmodium falciparum</i> M17 Leucyl Aminopeptidase with Favorable Pharmacokinetic Profile

“…One alternative to ACT anti pf resistance strategy is the design of hybrid drugs where two antimalarial moieties are linked into a unique molecule, these moieties known for their confirmed antimalarial potency against two different parasite targets and operating according different mechanisms of action [4,5,6].…”

Development of Plasmodium falciparum Protease Inhibitors in the Past Decade (2002–2012)

“…The unmatched relevance of the dipeptidyl vinyl sulfone warhead for FP inhibition has been also recognized in research works where this moiety has been combined with other antimalarial scaffolds, e.g., artemisinin, to produce multi-target antimalarial molecules 29 (Fig. 24) [115]. Fig.…”