Development of the first oral bioprecursors of bis-alkylguanidine antimalarial drugs.

Plasmodium falciparum is responsible of the most severe form of malaria, and new targets and novel chemotherapeutic scaffolds are needed to fight emerging multidrug-resistant strains of this parasite. Bis-alkylguanidines have been designed to mimic choline, resulting in the inhibition of plasmodial de novo phosphatidylcholine biosynthesis. Despite potent in vitro antiplasmodial and in vivo antimalarial activities, a major drawback of these compounds for further clinical development is their low oral bioavailability. To solve this issue, various modulations were performed on bis-alkylguanidines. The introduction of N-disubstituents on the guanidino motif improved both in vitro and in vivo activities. On the other hand, in vivo pharmacological evaluation in a mouse model showed that the N-hydroxylated derivatives constitute the first oral bioprecursors in bis-alkylguanidine series. This study paves the way for bis-alkylguanidine-based oral antimalarial agents targeting plasmodial phospholipid metabolism.

Disulfide prodrugs of albitiazolium (T3/SAR97276): synthesis and biological activities.

We report herein the design, synthesis, and biological screening of a series of 15 disulfide prodrugs as precursors of albitiazolium bromide (T3/SAR97276, compound 1), a choline analogue which is currently being evaluated in clinical trials (phase II) for severe malaria. The corresponding prodrugs are expected to revert back to the active bis-thiazolium salt through an enzymatic reduction of the disulfide bond. To enhance aqueous solubility of these prodrugs, an amino acid residue (valine or lysine) or a phosphate group was introduced on the thiazolium side chain. Most of the novel derivatives exhibited potent in vitro antimalarial activity against P. falciparum. After oral administration, the cyclic disulfide prodrug 8 showed the best improvement of oral efficacy in comparison to the parent drug.

Evaluation of bis-alkylamidoxime O-alkylsulfonates as orally available antimalarials.

The main threat to controlling malaria is the emerging multidrug resistance of Plasmodium sp. parasites. Bis-alkylamidines were developed as a potential new chemotherapy that targets plasmodial phospholipid metabolism. Unfortunately, these compounds are not orally available. To solve this absorption issue, we investigated a prodrug strategy based on sulfonate derivatives of alkylamidoximes. A total of 25 sulfonates were synthesized as prodrug candidates of one bis-N-alkylamidine and of six N-substituted bis-C-alkylamidines. Their antimalarial activities were evaluated in vitro against P. falciparum and in vivo against P. vinckei in mice to define structure-activity relationships. Small alkyl substituents on the sulfonate group of both C-alkyl- and N-alkylamidines led to the best oral antimalarial activities; alkylsulfonate derivatives are chemically transformed into the corresponding alkylamidines.

Reverse-benzamidine antimalarial agents: design, synthesis, and biological evaluation.

In the frame of the development of bis-cationic choline analogs, the RSA of bis-N-alkylamidines were studied and a new series of reverse-benzamidine derivatives was designed. Contrary to the lipophilicity, the basicity of alkylamidine compounds directly influences their antimalarial potencies.

Synthesis and evaluation of bis-thiazolium salts as potential antimalarial drugs.

An innovative therapeutic approach based on the use of dicationic derivatives was previously designed to inhibit the biosynthesis of phosphatidylcholine in Plasmodium spp. Among these, bis-thiazolium salts were shown to block proliferation of the malaria parasite at concentrations in the low nanomolar range. However, due to unsuitable molecular properties such as the presence of the two polar heads and flexibility in the linker, these compounds have low oral bioavailability. To characterize the structural requirements of the linker that lead to more rigid analogues with fewer rotatable bonds but which retain antimalarial activity, a new series of compounds incorporating an aryl moiety and eventually oxygen atoms were prepared, and their biological activity was evaluated. Structure-activity relationships suggest that the optimal linker construct is an aromatic group with two n-butyl chains branched at the para position; two new leads (compounds 39 and 40) were selected for further development.

Control of protein-protein interactions: structure-based discovery of low molecular weight inhibitors of the interactions between Pin1 WW domain and phosphopeptides.

Interactions involving phosphorylated Ser/Thr-Pro motifs in proteins play a key role in numerous regulatory processes in the cell. Here, we investigate potential ligands of the WW binding domain of Pin1 in order to inhibit protein-protein interactions between Pin1 and phosphopeptides. Our structure-based strategy implies the synthesis of analogues of the Ac-Thr(PO(3)H(2))-Pro-NH(2) dipeptide and relies on high resolution NMR spectroscopy to accurately measure the affinity constants even in the high micromolar range.