1-hydroxypentane-1-1-bisphosphonate and fosmidomycin

We screened a library of 117 bisphosphonates for antibacterial activity against Escherichia coli. The most potent growth inhibitors where N-[methyl(4-phenylalkyl)]-3-aminopropyl-1-hydroxy-1,1-bisphosphonates, known potent bone resorption inhibitors, and there was a generally good correlation between cell growth inhibition and E. coli farnesyl diphosphate synthase (FPPS) inhibition. However, some potent FPPS inhibitors had no activity in cell growth inhibition, and based on the result of Catalyst pharmacophore modeling, this could be attributed to the requirement of a large hydrophobic feature for cellular activity (due most likely to transport). The activity of the most potent compound, N-[methyl(4-phenylbutyl)]-3-aminopropyl-1-hydroxy-1,1-bisphosphonate (13), was strongly potentiated by the drug fosmidomycin. The transcription profiles for 13 or fosmidomycin alone were different from those found with carbenicillin or ciprofloxacin alone, but there were many similarities between the combination (13-fosmidomycin) and carbenicillin or ciprofloxacin, reflecting the more potent bactericidal activity of the drug combination on bacterial growth.

Topics: Anti-Bacterial Agents; Cluster Analysis; Diphosphonates; Drug Synergism; Escherichia coli K12; Fosfomycin; Gene Expression; Geranyltranstransferase; Models, Molecular; Oligonucleotide Array Sequence Analysis; Quantitative Structure-Activity Relationship; Terpenes

We have investigated the activity of 60 bisphosphonates against the replication of Toxoplasma gondii in vitro and of three of the most active compounds, in vivo. The two most active compounds found were n-alkyl bisphosphonates containing long (n = 9 or 10) hydrocarbon chains, not the nitrogen-containing species used in bone resorption therapy. The target of all of the most active bisphosphonates appears to be the isoprene biosynthesis pathway enzyme farnesyl pyrophosphate synthase (FPPS), as indicated by the correlations between T. gondii growth inhibition and FPPS (human and Leishmania major) enzyme inhibition and by the fact that a T. gondii strain engineered to overexpress FPPS required considerably higher levels of bisphosphonates to achieve 50% growth inhibition, while the IC(50) for atovaquone (which does not inhibit FPPS) remained the same in the overexpressing strain. The phosphonate inhibitor of the non-mevalonate pathway, fosmidomycin, which inhibits the enzyme 1-deoxyxylulose-5-phosphate reductoisomerase, had no effect on T. gondii growth. To investigate structure-activity relationships (SARs) in more detail, we used two three-dimensional quantitative SAR methods: comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA), to investigate all 60 bisphosphonates. Both the CoMFA and CoMSIA models indicated a 60-70% contribution from steric interactions and a 30-40% contribution from electrostatic interactions and using four N = 55 training sets for each method, we found on average between a factor of 2 and 3 error in IC(50) prediction. The three most active compounds found in vitro were tested in vivo in a Smith-Webster mouse model and the two most active bisphosphonates were found to provide up to an 80% protection from death, a considerable improvement over that found previously with nitrogen-containing bisphosphonates. This effect may originate in the much higher therapeutic indices of these alkyl bisphosphonates, as deduced from in vitro assays using LD(50) values for growth inhibition of a human cell line. Overall, these results indicate that alkyl bisphosphonates are promising compounds for further development as agents against Toxoplasma gondii growth, in vivo.

Topics: Aldose-Ketose Isomerases; Alkyl and Aryl Transferases; Animals; Antiprotozoal Agents; Cell Line; Diphosphonates; Fosfomycin; Geranyltranstransferase; Humans; Mice; Models, Molecular; Multienzyme Complexes; Oxidoreductases; Quantitative Structure-Activity Relationship; Toxoplasma; Toxoplasmosis