Treatment of primary herpes simplex virus infection in guinea pigs by imiquimod.

Imiquimod (also known as R-837 and S-26308) is an imidazoquinoline immune response modifier and is available in the US and several other countries for the treatment of external genital warts. Imiquimod has no direct antiviral activity but demonstrates efficacy in several animal models of virus infection. The drug is recognized by antigen presenting cells including monocytes, macrophages, B-cells and dendritic cells and induces these cells to produce cytokines including interferon-alpha (IFN-alpha) and others. Imiquimod's ability to inhibit primary lesion development in the guinea pig model of Herpes simplex virus (HSV) intravaginal infection was studied. Imiquimod given intravaginally reduced primary lesions, reduced virus shedding and reduced virus content of spinal cords from HSV infected guinea pigs. A single drug application of 0.5 mg/kg reduced lesion frequency when given between 24 h before inoculation to 16 h after inoculation. A single drug application of 5 mg/kg reduced lesion frequency and severity when administered between 72 h before inoculation to 24 h after inoculation. The antiviral effect resulting from interferon induction in the animal lasts much longer than the drug itself, thus imiquimod is different than drugs having direct antiviral activity. Twice daily drug application for 4 days was effective when initiated up to 72 h after inoculation, however, once lesions began to appear, imiquimod treatment was not able to stop lesion development. Imiquimod treatment inhibited lesion development and/or virus shedding in guinea pigs inoculated with HSV-1, HSV-2 or virus isolates resistant to acyclovir. Imiquimod is currently in clinical trials for treating human HSV infections.

Imiquimod applied topically: a novel immune response modifier and new class of drug.

Imiquimod (S-26308, R-837) (1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4 amine), an immune response modifier, demonstrates potent antiviral and antitumor activity in animal models (see structure in Fig. 1). The drug exhibits no direct antiviral or antiproliferative activity when tested in a number of cell culture systems. Imiquimod's activity was discovered while screening for anti-herpes virus activity. One of the first analogs in the series, S-25059 was tested in the early 1980's and due to slight toxicity, caused slightly reduced herpes cytopathology in Vero cell cultures. Follow-up testing in herpes infected guinea pigs showed complete protection toward lesion development. Activity of these drugs results primarily from interferon alpha (IFN-alpha) induction and other cytokine induction. At least part of the cytokine induction is mediated through NF-kappaB activation. These cytokines stimulate several other aspects of the innate immune response. In addition, imiquimod stimulates acquired immunity, in particular the cellular arm which is important for control of viral infections and various tumors. This effect is mediated by drug induced IFN-alpha and Interleukin-12 (IL-12) and IFN-gamma induced by these cytokines. Imiquimod is expected to be effective where exogenous IFN-alpha has shown utility and where enhancement of cell-mediated immunity is needed. The following is a brief review of the preclinical pharmacology of imiquimod and the clinical results of genital wart trials. The mechanism of action of topically applied imiquimod will likely lead to benefits in several other chronic virus infections and tumors of the skin. Two other reviews on imiquimod that focus mainly on the clinical results have been published (Beutner & Geisse, 1997; Slade, Owens, Tomai & Miller, 1998).

Immunomodulating and antiviral activities of the imidazoquinoline S-28463.

Recently, a new class of immunomodulating agents, represented by the molecules imiquimod and R-842, has demonstrated potent antiviral and antitumor activities in animal models. In this study, another representative of this class, S-28463 (4-amino-2-ethoxymethyl-alpha,alpha-dimethyl-1H-imidazo[4,5-c]quinoline- 1- ethanol) was evaluated for its immunomodulating and antiviral activities. S-28463 induced IFN and other cytokines in vivo in mice, rats, monkeys and in vitro in human peripheral blood mononuclear cell cultures. S-28463 showed potent antiviral activity against herpes simplex virus-challenged guinea pigs when given subcutaneously, dermally, or intravaginally 24 h before infection. Antiviral activity in guinea pigs correlated with the induction of serum 2',5'-oligoadenylate synthetase activity. Thus, S-28463, like the other imidazoquinolines, demonstrates potent antiviral and immunomodulating effects in a number of models.

Cytokine induction by the immunomodulators imiquimod and S-27609.

Imiquimod (R-837, S-26308) and the analogue S-27609 were evaluated for cytokine induction in human blood cells. Both compounds induced interferon-alpha (IFN), tumor necrosis factor-alpha (TNF), interleukin (IL)-1 beta, and IL-6 with S-27609 being 5 to 10 times more potent. Imiquimod and S-27609 also induced IL-1 alpha, IL-1 receptor antagonist, IL-10, granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte CSF (G-CSF), and macrophage inflammatory protein-1 alpha. The profile of cytokines induced by imiquimod and S-27609 was different from those seen with lipopolysaccharide and polyinosinic-polycytidylic acid. Kinetic studies with both imiquimod and S-27609 revealed induction of cytokines as early as 1-4 h after stimulation. Although most of the cytokines produced by S-27609 were secreted, significant concentrations of IL-1 alpha and IL-1 beta remained intracellular. Monocytes were largely responsible for the cytokines produced. Finally, S-27609-induced mRNA expression for TNF, IFN, and IL-8, and this induction did not require protein synthesis. Taken together, these studies extend previous findings by showing induction of additional cytokines and providing insight into the mechanism of cytokine induction by these molecules.

Synthesis, absolute configuration, and antibacterial activity of 6,7-dihydro-5,8-dimethyl-9-fluoro-1-oxo-1H,5H- benzo[ij]quinolizine-2-carboxylic acid.

The tricyclic quinolone antibacterial agent 6,7-dihydro-5,8-dimethyl-9-fluoro-1-oxo-1H,5H-benzo[ij]quinolizine -2-carboxylic acid has an asymmetric center at position 5 of the molecule. The R and S isomers of the compound have been prepared from the corresponding (R)- and (S)-2,5-dimethyl-6-fluoro-1,2,3,4-tetrahydroquinolines, which were separated via their diastereomeric amides of N-tosyl-(S)-proline. The absolute configuration was established by X-ray analysis of one of the diastereomeric amides. The 5-desmethyl analogue was prepared for antibacterial comparison with the isomers and the racemic mixture. It has now been established that the S isomer is much more active than the R isomer. The 5-desmethyl analogue was found to be more active than the R isomer but not as active as the S isomer or the racemic mixture. The importance of stereochemistry at position 5 in this system has been established.

Disposition of radiolabeled flumequine in rat and dog.

Single doses of 14C-flumequine (a urinary tract antibacterial) were given to rats and dogs. Unchanged drug accounted for more than 80% of the drug in plasma of rats but only 25-50% in plasma of dogs. Although only a small percentage of the dose was excreted in the urine of each species as unchanged drug, a wide differentiation in the urinary metabolite profiles was observed. No significant tissue retention was seen in rats or dogs.

Differentiation of fluorinated quinolone antibacterials with Neisseria gonorrhoeae isolates.

Clinical isolates of Neisseria gonorrhoeae were tested for growth inhibition by various quinolones. One acrosoxacin-resistant isolate was also resistant to several fluorinated quinolones with 7-heterocyclic substitution, but, inhibitory concentrations were not elevated for quinolones substituted with a methyl group in the corresponding position (nalidixic acid:position 7, S-25930:position 8) or unsubstituted (flumequine:position 8). Isolates resistant to flumequine demonstrated elevated inhibitory concentrations for all quinolones examined.