Preclinical candidate for the treatment of visceral leishmaniasis that acts through proteasome inhibition

Abstract

Visceral leishmaniasis (VL), caused by the protozoan parasites Leishmania donovani and Leishmania infantum, is one of the major parasitic diseases worldwide. There is an urgent need for new drugs to treat VL, because current therapies are unfit for purpose in a resource-poor setting. Here, we describe the development of a preclinical drug candidate, GSK3494245/DDD01305143/compound 8, with potential to treat this neglected tropical disease. The compound series was discovered by repurposing hits from a screen against the related parasite Trypanosoma cruzi. Subsequent optimization of the chemical series resulted in the development of a potent cidal compound with activity against a range of clinically relevant L. donovani and L. infantum isolates. Compound 8 demonstrates promising pharmacokinetic properties and impressive in vivo efficacy in our mouse model of infection comparable with those of the current oral antileishmanial miltefosine. Detailed mode of action studies confirm that this compound acts principally by inhibition of the chymotrypsin-like activity catalyzed by the β5 subunit of the L. donovani proteasome. High-resolution cryo-EM structures of apo and compound 8-bound Leishmania tarentolae 20S proteasome reveal a previously undiscovered inhibitor site that lies between the β4 and β5 proteasome subunits. This induced pocket exploits β4 residues that are divergent between humans and kinetoplastid parasites and is consistent with all of our experimental and mutagenesis data. As a result of these comprehensive studies and due to a favorable developability and safety profile, compound 8 is being advanced toward human clinical trials.

GemSpot: A Pipeline for Robust Modeling of Ligands into CryoEM Maps

“…Fubinaca/Cannabinoid receptor 1 (PDB:6N4B, EMD:0339) 33 ; GSK 3494245/Leishmania 20S proteasome (PDB:6QM7, EMD:4590) 36 ; Paromomycin/Leishmania ribosome (PDB:6AZ1, EMD:7024) 35 ; Menthol analogue WS-12/Ion channel TRPM8 (PDB:6NR2, EMD:0488) 41 ;…”

COP9 signalosome is an essential and druggable parasite target that regulates protein degradation

“…That said, new therapies are urgently needed given the lack of effective vaccines, drug resistance, limited efficacy and toxicity associated with current treatment (2)(3)(4). Given that the UPS pathway is essential for cell survival, inhibition of the proteasome has emerged as an attractive anti-parasitic target (5)(6)(7)(8)(9). However, the regulation of UPS-mediated protein degradation in clinically important protozoans remains poorly understood.…”

Essential roles for deubiquitination inLeishmanialife cycle progression

“…Recent studies showed the potential for proteasome inhibition as a treatment for three diseases caused by trypanosomatid parasitic protozoa, including leishmaniasis [9,10]. The proteasome is dependent on the ubiquitination pathway to identify substrates for degradation and a search of the Leishmania genome reveals a range of E1, E2 and E3 ligases, as well as a number of DUBs [33].…”

“…Reversible post-translational modification (PTM) of proteins with chemical groups, such as phosphorylation, or other proteins, such as ubiquitination, are likely to be pivotal for successful life cycle progression [3–5] and intracellular parasitism. In addition, irreversible PTM such as proteolytic cleavage is important for the cellular remodeling that occurs during the life cycle of Leishmania and the commitment to differentiation [6–8], as well as in amastigote survival [9,10].…”