Diarylquinolines are bactericidal for dormant mycobacteria as a result of disturbed ATP homeostasis

An estimated one-third of the world population is latently infected with Mycobacterium tuberculosis. These nonreplicating, dormant bacilli are tolerant to conventional anti-tuberculosis drugs, such as isoniazid. We recently identified diarylquinoline R207910 (also called TMC207) as an inhibitor of ATP synthase with a remarkable activity against replicating mycobacteria. In the present study, we show that R207910 kills dormant bacilli as effectively as aerobically grown bacilli with the same target specificity. Despite a transcriptional down-regulation of the ATP synthase operon and significantly lower cellular ATP levels, we show that dormant mycobacteria do possess residual ATP synthase enzymatic activity. This activity is blocked by nanomolar concentrations of R207910, thereby further reducing ATP levels and causing a pronounced bactericidal effect. We conclude that this residual ATP synthase activity is indispensable for the survival of dormant mycobacteria, making it a promising drug target to tackle dormant infections. The unique dual bactericidal activity of diarylquinolines on dormant as well as replicating bacterial subpopulations distinguishes them entirely from the current anti-tuberculosis drugs and underlines the potential of R207910 to shorten tuberculosis treatment.

Selection of a respiratory syncytial virus fusion inhibitor clinical candidate, part 1: improving the pharmacokinetic profile using the structure-property relationship

We previously reported the discovery of substituted benzimidazole fusion inhibitors with nanomolar activity against respiratory syncytial virus (Andries, K.; et al. Antiviral Res. 2003, 60, 209-219). A lead compound of the series was selected for preclinical evaluation. This drug candidate, JNJ-2408068 (formerly R170591, 1), showed long tissue retention times in several species (rat, dog, and monkey), creating cause for concern. We herein describe the optimization program to develop compounds with improved properties in terms of tissue retention. We have identified the aminoethyl-piperidine moiety as being responsible for the long tissue retention time of 1. We have investigated the replacement or the modification of this group, and we suggest that the pKa of this part of the molecules influences both the antiviral activity and the pharmacokinetic profile. We were able to identify new respiratory syncytial virus inhibitors with shorter half-lives in lung tissue.

Diarylquinolines target subunit c of mycobacterial ATP synthase

The diarylquinoline R207910 (TMC207) is a promising candidate in clinical development for the treatment of tuberculosis. Though R207910-resistant mycobacteria bear mutations in ATP synthase, the compound's precise target is not known. Here we establish by genetic, biochemical and binding assays that the oligomeric subunit c (AtpE) of ATP synthase is the target of R207910. Thus targeting energy metabolism is a new, promising approach for antibacterial drug discovery.

Substituted benzimidazoles with nanomolar activity against respiratory syncytial virus

A cell-based assay was used to discover compounds inhibiting respiratory syncytial virus (RSV)-induced fusion in HeLa/M cells. A lead compound was identified and subsequent synthesis of >300 analogues led to the identification of JNJ 2408068 (R170591), a low molecular weight (MW 395) benzimidazole derivative with an EC(50) (0.16 nM) against some lab strains almost 100,000 times better than that of ribavirin (15 microM). Antiviral activity was confirmed for subgroup A and B clinical isolates of human RSV and for a bovine RSV isolate. The compound did not inhibit the growth of representative viruses from other Paramyxovirus genera, i.e. HPIV2 and Mumps Virus (genus Rubulavirus), HPIV3 (genus Respirovirus), Measles virus (genus Morbillivirus) and hMPV. Efficacy in cytopathic effect inhibition assays correlated well with efficacy in virus yield reduction assays. A concentration of 10nM reduced RSV production 1000-fold in multi-cycle experiments, irrespective of the multiplicity of infection. Time of addition studies pointed to a dual mode of action: inhibition of virus-cell fusion early in the infection cycle and inhibition of cell-cell fusion at the end of the replication cycle. Two resistant mutants were raised and shown to have single point mutations in the F-gene (S398L and D486N). JNJ 2408068 was also shown to inhibit the release of proinflammatory cytokines IL-6, IL-8 and Rantes from RSV-infected A549 cells.

In vitro activity of pirodavir (R 77975), a substituted phenoxy-pyridazinamine with broad-spectrum antipicornaviral activity

Pirodavir (R 77975) is the prototype of a novel class of broad-spectrum antipicornavirus compounds. Although its predecessor, R 61837, a substituted phenyl-pyridazinamine, was effective in inhibiting 80% of 100 serotypes tested (EC80) at concentrations above 32 micrograms/ml, pirodavir inhibits the same percentage of viruses at 0.064 micrograms/ml. Whereas R 61837 was active almost exclusively against rhinovirus serotypes of antiviral group B, pirodavir is broad spectrum in that it is highly active against both group A and group B rhinovirus serotypes. Pirodavir is also effective in inhibiting 16 enteroviruses, with an EC80 of 1.3 micrograms/ml. Susceptible rhinovirus serotypes were rendered noninfectious by direct contact with the antiviral compound. Their infectivity was not restored by dilution of virus-drug complexes, but was regained by organic solvent extraction of the compound for most serotypes. Neutralized viruses became stabilized to acid and heat, strongly suggesting a direct interaction of the compounds with viral capsid proteins. Mutants resistant to R 61837 (up to 85 times the MIC) were shown to bear some cross-resistance (up to 23 times the MIC) to the new compound, indicating that pirodavir also binds into the hydrophobic pocket beneath the canyon floor of rhinoviruses. Pirodavir acts at an early stage of the viral replication cycle (up to 40 min after infection) and reduces the yield of selected rhinoviruses 1,000- to 100,000-fold in a single round of replication. The mode of action appears to be serotype specific, since pirodavir was able to inhibit the adsorption of human rhinovirus 9 but not that of human rhinovirus 1A. Pirodavir is a novel capsid-binding antipicornavirus agent with potent in vitro activity against both group A and group B rhinovirus serotypes.

A comparative test of fifteen compounds against all known human rhinovirus serotypes as a basis for a more rational screening program

A systematic evaluation of 15 rhinovirus capsid-binding agents against all 100 serotyped human rhinoviruses revealed the existence of two virus groups, based upon differential susceptibility to antiviral compounds. Elongated and short-chained compounds preferentially inhibited groups A and B. The positions of the rhinoviruses within a map derived from a multivariate analysis allow for the selection of a panel of 17 rhinoviruses, for which the median antiviral inhibitory value against them will accurately predict the median value against 100 serotypes. This rationalizes the search for broad-spectrum capsid-binding antirhinovirus drugs, or combinations of drugs with complementary spectra that may be necessary to effectively inhibit both type A and type B viruses.

Erbulozole (P.I.N.N.) (R 55 104) encapsulated into cyclodextrins: has it a combined antitumoral and radioprotective potential?

The clinically applicable formulation of the microtubule inhibitor erbulozole (R 55 104), dissolved into an aqueous hydroxypropyl-beta-cyclodextrin solution (designated as R 55 104-CYCLO), exerts a similar effect on growth delay of subcutaneous MO4 fibrosarcomas in mice, with or without 10 Gy gamma-irradiation given locally to the tumors 2 h later, compared to R 55 104 in water. The drug concentration can be reduced from 80 mg/kg to 5 mg/kg without affecting the activity of this particular drug-radiation combination. Furthermore, 80 mg/kg R 55 104-CYCLO show a radioprotective effect when given 2 h before total body irradiation of non-tumor bearing mice. A radiation dose of 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 Gy respectively was given resulting in a LD50(30) of 5.97 Gy for the irradiated mice and 7.65 Gy for the drug-radiation treated animals (Dose Effect Factor = 0.78). Therapeutic implications of both observations are discussed.

Influence of the synthetic microtubule inhibitor erbulozole (P.I.N.N.) (R 55 104), a new tubulozole congener, and gamma irradiation on murine tumors in vivo

Erbulozole (P.I.N.N.) (R 55 104) is a more water soluble congener of the synthetic microtubule inhibitor tubulozole (R 46 846) exhibiting a reversible antimicrotubular activity in vitro at a dose (1.56 x 10(-8) M) which is at least 10-fold lower. The compound also has an antiinvasive potential and shows antitumoral effects both in vitro and in vivo when administered appropriately. Eighty mg/kg R 55 104, given orally 6 h before or 3 h after radiotherapy, displays a prominent interactive effect with 10 Gy gamma irradiation in subcutaneous murine tumors which is similar to 160 mg/kg tubulozole administered 6 h before 10 Gy. The enhancing effect is also observed in a clinically relevant radiation dose fractionation schedule whereby eight fractions of 2 Gy each were pretreated 2 h before with 40 mg/kg R 55 104. Further study of this radiochemotherapeutic combination may lead to new clinical applications.

Lack of quantitative correlation between inhibition of replication of rhinoviruses by an antiviral drug and their stabilization

R 61,837, a new antirhinovirus compound, was able to protect several susceptible rhinoviruses against inactivation by mild acidification or heat. This observation strengthens the hypothesis that the drug exerts antiviral activity by a direct interaction with the viral protein capsid to stabilize the particle. However, the minimal concentrations necessary to inhibit either acetate or citrate or heat inactivation were different for each of five tested serotypes and we therefore conclude that stabilization and inhibition of replication are not causally linked but parallel events, both independently resulting from the binding of the drug to the viral capsid. Studies using drug resistant mutants of HRV51 and HRV9 confirmed this lack of quantitative correlation. The mutants were also shown to be cross resistant to a panel of seven different reference antirhinoviral drugs including SDS, WIN51711, chalcone, dichloroflavan and MDL20,610. This indicates that all these compounds bind to the same site corresponding to the hydrophobic pocket within the viral protein VP 1 beta-barrel structure of HRV14.

Interaction between the microtubule inhibitor tubulozole and gamma-irradiation in murine tumors in vivo

The combined effect of the microtubule inhibitor tubulozole and gamma-irradiation has been investigated in vivo in subcutaneous MO4 fibrosarcomas and Lewis Lung carcinomas. A marked interactive effect on tumor growth was observed when 160 mg/kg tubulozole was orally administered before the tumors were treated with 10 Gy radiation. Dose dependency and optimal effect were obtained on tumor growth of MO4 tumor bearing animals when the drug treatment was given 6 hr prior to the irradiation. The optimal pretreatment time coincided with the time at which a peak mitotic index in the tumor tissue was observed. An enhancing effect is also noticed at other doses of radiation in MO4 tumors pretreated 6 hr before with 160 mg/kg tubulozole. The interactive effect is maintained in a clinically relevant dose fractionation schedule whereby 8 fractions of 2 Gy each were pretreated 6 hr before with 80 mg/kg tubulozole. Tubulozole-T, the stereo-isomer of tubulozole, neither exhibits any antimicrotubular action nor exerts an antitumoral effect on its own or in combination with gamma-irradiation. The possible mechanisms of interaction between tubulozole and gamma-irradiation in tumor tissue are discussed.

The kidney invasion test: its application to the Lewis lung carcinoma system

Implantation of fragments from subcutaneously grown Lewis lung carcinoma 3LL under the renal capsule of syngeneic mice results in invasion of the kidney parenchyma. The synthetic microtubule inhibitor tubulozole blocks or decreases this malignant invasion in a dose-dependent manner. The inhibition of the invasion rate caused by tubulozole can be macroscopically quantified, and has been confirmed histologically.

Taxol induces the assembly of free microtubules in living cells and blocks the organizing capacity of the centrosomes and kinetochores

Taxol, a potent promoter of microtubule polymerization in vitro, induces massive assembly of free microtubules in cultured cells as visualized by immunocytochemistry and electron microscopy. The centrosomes and kinetochores largely lost their capacity to organize microtubule assembly, as became evident by the disappearance of the cytoplasmic microtubule complex and the mitotic spindle. The taxol-induced microtubules were partially resistant to nocodazole, an inhibitor of tubulin polymerization. Moreover, taxol induced microtubule assembly in cells pretreated with nocodazole. Increasing the ratio of nocodazole to taxol restored the ability of the centrosomes and kinetochores to specifically induce microtubule assembly in their immediate vicinity. The data suggest that taxol lowers the critical tubulin concentration in vivo as well as in vitro and that the organizing capacity of the microtubule-organizing centers depends on the cytoplasmic polymerization threshold.