Synergistic Activity between Statins and Bisphosphonates against Acute Experimental Toxoplasmosis

Abstract

Bisphosphonates are widely used for the treatment of bone disorders. These drugs also inhibit the growth of a variety of protozoan parasites, such as Toxoplasma gondii, the etiologic agent of toxoplasmosis. The target of the most potent bisphosphonates is the isoprenoid biosynthesis pathway enzyme farnesyl diphosphate synthase (FPPS). Based on our previous work on the inhibitory effect of sulfurcontaining linear bisphosphonates against T. gondii, we investigated the potential synergistic interaction between one of these derivatives, 1-[(n-heptylthio)ethyl]-1,1-bisphosphonate (C7S), and statins, which are potent inhibitors of the host 3-hydroxy-3-methyl glutaryl-coenzyme A reductase (3-HMG-CoA reductase). C7S showed high activity against the T. gondii bifunctional farnesyl diphosphate (FPP)/geranylgeranyl diphosphate (GGPP) synthase (TgFPPS), which catalyzes the formation of FPP and GGPP (50% inhibitory concentration [IC 50 ] ϭ 31 Ϯ 0.01 nM [mean Ϯ standard deviation]), and modest effect against the human FPPS (IC 50 ϭ 1.3 Ϯ 0.5 M). We tested combinations of C7S with statins against the in vitro replication of T. gondii. We also treated mice infected with a lethal dose of T. gondii with similar combinations. We found strong synergistic activities when using low doses of C7S, which were stronger in vivo than when tested in vitro. We also investigated the synergism of several commercially available bisphosphonates with statins both in vitro and in vivo. Our results provide evidence that it is possible to develop drug combinations that act synergistically by inhibiting host and parasite enzymes in vitro and in vivo.

The Role of the Phosphorus Atom in Drug Design

“…Moreover, a strong synergistic effect was observed when another sulfur‐containing compound was assayed against T. gondii . In this context, 1‐[( n ‐heptylthio)ethyl]‐1,1‐biphosphonate ( 77 , C7S), when used in combination with atorvastatin (a potent inhibitor of the host 3‐hydroxy‐3‐methylglutaryl‐coenzyme A reductase), was found to have high activity against the hypervirulent RH strain of T. gondii in in vivo assays (Figure ) . This synergistic effect had been observed previously with zoledronic acid ( 61 , see Figure ) …”

Farnesyl pyrophosphate synthase is essential for the promastigote and amastigote stages in Leishmania major

“…A similar observation was made in T. gondii (an apicomplexan), as the intracellular tachyzoites were capable of salvaging isoprenoids to support growth in fibroblasts but not macrophages [26]. Such discoveries have promoted the development of drug combinations that act synergistically by inhibiting both host and parasite isoprenoid synthesis [53].…”

A Metabolic Dependency for Host Isoprenoids in the Obligate Intracellular Pathogen Rickettsia parkeri Underlies a Sensitivity to the Statin Class of Host-Targeted Therapeutics

“…parkeri, the parasite Cryptosporidium parvum lacks the canonical protozoan isoprenoid pathway and has been shown to be sensitive to statins (52). Interestingly, the facultative intracellular protozoan parasite Toxoplasma gondii, which encodes the MEP isoprenoid pathway within a membrane-bound organelle called the apicoplast, has been shown to be sensitive to statins when the parasite is intracellular (53, 54), suggesting that host metabolite scavenging is still advantageous for pathogens with intact pathways. In the future, bioinformatic analyses may identify other intracellular bacteria that have incomplete upstream isoprenoid pathways and intact downstream isoprenoid pathways and thus may also be sensitive to statins.…”