Development of novel dipeptide-like rhodesain inhibitors containing the 3-bromoisoxazoline warhead in a constrained conformation.

Novel dipeptide-like rhodesain inhibitors containing the 3-bromoisoxazoline warhead in a constrained conformation were developed; some of them possess K(i) values in the micromolar range. We studied the structure-activity relationship of these derivatives and we performed docking studies, which allowed us to find out the key interactions established by the inhibitors with the target enzyme. Biological results indicate that the nature of the P2 and P3 substituents and their binding to the S2/S3 pockets is strictly interdependent.

Synthesis and biological evaluation of papain-family cathepsin†L-like cysteine protease inhibitors containing a 1,4-benzodiazepine scaffold as antiprotozoal agents.

Novel papain-family cathepsin L-like cysteine protease inhibitors endowed with antitrypanosomal and antimalarial activity were developed, through an optimization study of previously developed inhibitors. In the present work, we studied the structure-activity relationships of these derivatives, with the aim to develop new analogues with a simplified and more synthetically accessible structure and with improved antiparasitic activity. The structure of the model compounds was significantly simplified by modifying or even eliminating the side chain appended at the C3 atom of the benzodiazepine scaffold. In addition, a simple methylene spacer of appropriate length was inserted between the benzodiazepine ring and the 3-bromoisoxazoline moiety. Several rhodesain and falcipain-2 inhibitors displaying single-digit micromolar or sub-micromolar antiparasitic activity against one or both parasites were identified, with activities that were one order of magnitude more potent than the model compounds.

Development of rhodesain inhibitors with a 3-bromoisoxazoline warhead.

Novel rhodesain inhibitors were obtained by combining an enantiomerically pure 3-bromoisoxazoline warhead with a specific peptidomimetic recognition moiety. All derivatives behaved as inhibitors of rhodesain, with low micromolar Ki values. Their activity against the enzyme was found to be paralleled by an in vitro antitrypanosomal activity, with IC50 values in the mid-micromolar range. Notably, a preference for parasitic over human proteases, specifically cathepsins B and L, was observed.

Inhibition of rhodesain as a novel therapeutic modality for human African trypanosomiasis.

Rhodesain, a cathepsin L-like cysteine protease of T. brucei rhodesiense, is considered a potential target for the treatment of human African trypanosomiasis. Recent findings have confirmed that rhodesain, a lysosomal protease, is essential for parasite survival. Rhodesain is required by T. brucei to cross the blood-brain barrier, degrade host immunoglobulins, and turn over variant surface coat glycoproteins of T. brucei, which impair effective host immune responses. In this Perspective, we discuss the main classes of rhodesain inhibitors, including peptidic, peptidomimetic, and nonpeptidic structures, emphasizing those that have exhibited an optimal match between enzymatic affinity and trypanocidal profile and those for which preclinical investigations are currently in progress.