Inhibition of Leishmania mexicana Growth by the Tuberculosis Drug SQ109

Abstract

We report that the tuberculosis drug SQ109 [N-adamantan-2-yl-N=-((E)-3,7-dimethyl-octa-2,6-dienyl)-ethane-1,2-diamine] has potent activity against the intracellular amastigote form of Leishmania mexicana (50% inhibitory concentration [IC 50 ], ϳ11 nM), with a good selectivity index (>500). It is also active against promastigotes (IC 50 , ϳ500 nM) and acts as a protonophore uncoupler, in addition to disrupting Ca 2؉ homeostasis by releasing organelle Ca 2؉ into the cytoplasm, and as such, it is an interesting new leishmaniasis drug hit candidate. There is a need for new drugs to treat the neglected tropical diseases, in particular, Chagas disease and leishmaniasis. In previous work (1-5), we discovered that the antiarrhythmia drugs amiodarone (Fig. 1, compound 1) and dronedarone ( Fig. 1, compound 2) had activity against Trypanosoma cruzi as well as Leishmania mexicana, the causative agents of Chagas disease and one form of cutaneous leishmaniasis, respectively. In addition, amiodarone was found to have partial in vivo activity against T. cruzi in mice, which was considerably increased when added in combination with posaconazole (1), and in initial clinical work in humans, it has been used to treat parasitic infections (6, 7). The mechanism of action of compounds 1 and 2 is thought to involve uncoupling activity, with the release of Ca 2ϩ from intracellular organelles (acidocalcisomes and mitochondria), as well as inhibition of oxidosqualene synthase and hence, ergosterol biosynthesis. Interestingly, another type of uncoupler, the nitrothiazole nitazoxanide ( Fig. 1, compound 3), and its active metabolite, tizoxanide ( Fig. 1, compound 4), also have activity against T. cruzi and L. mexicana (8), and compound 4 has been shown to act, at least in part, as an uncoupler, in Mycobacterium tuberculosis (9).Since we and others recently reported (10-13) that another M. tuberculosis drug/drug lead (13-15), SQ109 (Fig. 1, compound 5) [N-adamantan-2-yl-N=-((E)-3,7-dimethyl-octa-2,6-dienyl)-ethane-1,2-diamine], also acted as an uncoupler in Mycobacterium smegmatis, we tested it against T. cruzi, finding 50% inhibitory concentrations (IC 50 s) of ϳ50 nM against trypomastigotes, ϳ5 M against epimastigotes, and ϳ1 M against amastigotes (13). The amastigote result was disappointing, being less effective than that we found with dronedarone (ϳ1 nM); however, since both amiodarone (Cordarone) and dronedarone (Multaq) come with "black box" warnings, we elected to test SQ109 against L. mexicana, since it seemed possible that it might have good activity against this parasitic protozoan, much in the same way as it does against M. tuberculosis (and M. smegmatis).We show in Fig. 2A and B the effects of SQ109 on the viability of L. mexicana promastigotes and intracellular amastigotes (inside J774 macrophages) and on macrophage viability (Fig. 2C and D). As can be seen in Fig. 2A and B, SQ109 inhibits the viability of L. mexicana promastigotes in a dose-dependent manner, and as shown in Fig. 2B, the IC 50 (after 72 h of treatment) is 0....

Identification of new MmpL3 inhibitors by untargeted and targeted mutant screens defines MmpL3 domains with differential resistance

“…While MmpL3 is conserved in mycobacteria, functional orthologs are not found in other bacteria and fungi. Despite this, several proposed MmpL3 inhibitors including BM212, THPP, and SQ109 have been shown to inhibit multiple bacterial and fungal species 8, 33, 34, 35 while other MmpL3 inhibitors including HC2091, AU1235, and indolecarboxamides are specific to mycobacteria. To define the spectrum of activity, the compounds were tested against several diverse species including Staphylococcus aureus, E. coli, Pseudomonas aeruginosa, Proteus vulgaris , and Enterococcus faecalis (Table 2).…”

Promiscuous Targets for Antitubercular Drug Discovery: The Paradigm of DprE1 and MmpL3

“…There has been some controversy as to the direct or indirect inhibition of these compounds against MmpL3, it has been suggested that some compounds may act indirectly on MmpL3 by disrupting the pH gradient and/or membrane potential which will disrupt the proton relay needed by MmpL3 to pump out TMM. Indeed, while SQ109 and BM212 display a broad spectrum of activity and are active against non-replicating Mtb bacilli, some others specifically target mycobacteria and do not kill nonreplicating bacilli [16,103,104]. In order to solve this controversy and to shed more light on the mechanism of action of these inhibitors, Li et al have recently developed assays both in vitro and in whole cells to identify direct inhibitors of MmpL3.…”

Mechanism of Action of Miltefosine on Leishmania donovani Involves the Impairment of Acidocalcisome Function and the Activation of the Sphingosine-Dependent Plasma Membrane Ca 2+ Channel

“…With regard to Ca 2ϩ signaling, it is known that the mechanisms involved in Ca 2ϩ regulation in trypanosomatids constitute a target for chemotherapeutic agents like amiodarone and dronedarone, which disrupt Ca 2ϩ homeostasis in T. cruzi and L. mexicana (21)(22)(23)(24) through their action on two organelles acting as Ca 2ϩ compartments, the mitochondrion and the acidocalcisomes. Moreover, the antituberculosis compound SQ109, which also possesses a very potent trypanocidal effect, was recently found to act on T. cruzi (25) and L. mexicana (26) through the same mechanism of Ca 2ϩ and mitochondrial disruption. Also in concerns to disruption of Ca 2ϩ regulation, it has been reported that many Ca 2ϩ channel antagonists produce a marked effect in several trypanosomatids (27), including L. donovani (28).…”