Denavir
Mode of antiviral action of penciclovir in MRC-5 cells infected with herpes simplex virus type 1 (HSV-1), HSV-2, and varicella-zoster virus.

Earnshaw DL, Bacon TH, Darlison SJ, Edmonds K, Perkins RM, Vere Hodge RA.

SmithKline Beecham Pharmaceuticals, Epsom, Surrey, England.

The metabolism and mode of action of penciclovir [9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine; BRL 39123] were studied and compared with those of acyclovir. In uninfected MRC-5 cells, low concentrations of the triphosphates of penciclovir and acyclovir were occasionally just detectable, the limit of detection being about 1 pmol/10(6) cells. In contrast, in cells infected with either herpes simplex virus type 2 (HSV-2) or varicella-zoster virus (VZV), penciclovir was phosphorylated quickly to give high concentrations of the triphosphate ester. Following the removal of penciclovir from the culture medium, penciclovir-triphosphate remained trapped within the cells for a long time (half-lives, 20 and 7 h in HSV-2- and VZV-infected cells, respectively). In HSV-2-infected cells, acyclovir was phosphorylated to a lesser extent and the half-life of the triphosphate ester was only 1 h. We were unable to detect any phosphates of acyclovir in VZV-infected cells. (S)-Penciclovir-triphosphate inhibited HSV-1 and HSV-2 DNA polymerase competitively with dGTP, the Ki values being 8.5 and 5.8 microM, respectively, whereas for acyclovir-triphosphate, the Ki value was 0.07 microM for the two enzymes. Both compounds had relatively low levels of activity against the cellular DNA polymerase alpha, with Ki values of 175 and 3.8 microM, respectively. (S)-Penciclovir-triphosphate did inhibit DNA synthesis by HSV-2 DNA polymerase with a defined template-primer, although it was not an obligate chain terminator like acyclovir-triphosphate. These results provide a biochemical rationale for the highly selective and effective inhibition of HSV-2 and VZV DNA synthesis by penciclovir and for the greater activity of penciclovir than that of acyclovir when HSV-2-infected cells were treated for a short time.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1336346&dopt=Abstract penciclovir Denavir



Denavir
The tolerance to and pharmacokinetics of penciclovir (BRL 39,123A), a novel antiherpes agent, administered by intravenous infusion to healthy subjects.

Fowles SE, Pierce DM, Prince WT, Staniforth D.

Drug Metabolism and Pharmacokinetics Department, SmithKline Beecham Pharmaceuticals, The Frythe, Welwyn, Hertfordshire, UK.

The tolerance to and pharmacokinetics of intravenously administered penciclovir (BRL 39,123A), a novel anti-herpes agent, were investigated in 15 healthy male subjects. The volunteers were divided into three groups, receiving either 10, 15 or 20 mg/kg penciclovir by a 60 min constant-rate infusion. Blood samples were taken sequentially up to 48 h after the start of the infusion and urine collections made at appropriate intervals up to 72 h. After a simple solid phase extraction, concentrations of penciclovir in plasma and urine were determined using HPLC with U.V. detection. Mean values of Cmax, corresponding usually with the end of infusion, and of AUC appeared to increase proportionately with dose. Furthermore, there was no evidence that dose significantly affected any individual pharmacokinetic parameter. Penciclovir was distributed into tissues with an overall mean volume of distribution of approximately 1.5 l.kg-1, i.e. approximately double that of body water. It was rapidly eliminated, with a mean total plasma clearance of 39.3 l.h-1, and a mean terminal-phase half-life of 2.0 h. The majority of the dose, approximately 70%, was excreted unchanged in the urine. Mean renal clearance of BRL 39,123 was 28.1 l.h-1, which exceeds normal glomerular filtration rate and approaches renal plasma flow. At all dose-levels, the infusions of penciclovir were well tolerated, with no evidence of drug-related adverse events.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1336464&dopt=Abstract penciclovir Denavir



Denavir
Profiling penciclovir susceptibility and prevalence of resistance of herpes simplex virus isolates across eleven clinical trials.

Sarisky RT, Bacon TH, Boon RJ, Duffy KE, Esser KM, Leary J, Locke LA, Nguyen TT, Quail MR, Saltzman R.

Virology Department, Metabolic and Viral Diseases Center of Excellence for Drug Discovery, GlaxoSmithKline Pharmaceuticals, Collegeville, Pennsylvania, USA. rsarisky cntus.jnj.com

Asusceptibility testing program was established to determine the prevalence of resistance to penciclovir among herpes simplex virus isolates collected from patients participating in 11 world-wide clinical trials involving penciclovir (topical or intravenous formulations) or famciclovir, the oral prodrug of penciclovir. These trials represented nine randomised double blind, placebo or aciclovir-controlled studies and two open-label studies. Groups surveyed included immunocompetent or immunocompromised patients receiving 2 to 12 months chronic suppressive therapy for genital herpes, immunocompetent patients with recurrent herpes labialis treated for four days, and immunocompromised patients with mucocutaneous herpes simplex virus (HSV). Another subset of patients had been identified as non-responders to aciclovir or to valaciclovir. This program assessed the susceptibility profile for a total of 2145 herpes simplex virus isolates from 913 immunocompetent and 288 immunocompromised patients treated with penciclovir, famciclovir, aciclovir or placebo (depending on trial design). HSV isolates were tested for susceptibility to penciclovir using the plaque reduction assay (PRA) in MRC-5 cells. Resistance was defined as an IC(50)>or=2.0 microg/ml or an IC(50)> 10-fold above the wild type control virus IC(50) within that particular assay. Penciclovir-resistant HSV was isolated from 0.22% immunocompetent patients, and 2.1% of immunocompromised patients overall and therefore the frequency of penciclovir-resistant herpes simplex virus in the immunocompetent population approximates that of aciclovir-resistant herpesvirus reported previously. Penciclovir-resistant HSV isolates were more common in isolates from immunocompromised patients, consistent with aciclovir clinical experience. Treatment with penciclovir (intravenous formulation) was associated with the development of resistant HSV in only one severely immunocompromised patient (day 7 isolate IC(50) = 2.01 microg/ml), although treatment was effective and resulted in the complete clearance of the lesion by day 8. No patients receiving topical penciclovir developed treatment-associated penciclovir-resistant HSV, and a single immunocompromised patient developed resistant HSV upon treatment with oral famiciclovir.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14505088&dopt=Abstract penciclovir Denavir



Denavir
Penciclovir solubility in Eudragit films: a comparison of X-ray, thermal, microscopic and release rate techniques.

Ahmed A, Barry BW, Williams AC, Davis AF.

Drug Delivery Group, School of Pharmacy, University of Bradford, Bradford, West Yorkshire BD7 1DP, UK.

The solubility of penciclovir (C(10)N(5)O(3)H(17)) in a novel film formulation designed for the treatment of cold sores was determined using X-ray, thermal, microscopic and release rate techniques. Solubilities of 0.15-0.23, 0.44, 0.53 and 0.42% (w/w) resulted for each procedure. Linear calibration lines were achieved for experimentally and theoretically determined differential scanning calorimetry (DSC) and X-ray powder diffractometry (XRPD) data. Intra- and inter-batch data precision values were determined; intra values were more precise. Microscopy was additionally useful for examining crystal shape, size distribution and homogeneity of drug distribution within the film. Whereas DSC also determined melting point, XRPD identified polymorphs and release data provided relevant kinetics.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15019028&dopt=Abstract penciclovir Denavir



Denavir
Synthesis and biological evaluation of novel tert-azido or tert-amino substituted penciclovir analogs.

Kim HO, Baek HW, Moon HR, Kim DK, Chun MW, Jeong LS.

Laboratory of Medicinal Chemistry, College of Pharmacy, Ewha Womans University, Seoul 120-750, Korea.

tert-Azido or amino substituted penciclovir analogs, 1-3 were synthesized for the purpose of improving the efficacy and bioavailability of penciclovir and searching for novel antiviral agents. Among several methods attempted to insert an azido group into the alpha,beta-unsaturated ester 6, only Bronsted acid-catalysed 1,4-conjugate addition conditions (NaN3, 75% acetic acid, 80 degrees C) gave the desired tert-azido product 7. The synthesized final penciclovir analogs 1-3 were evaluated in vitro against several viruses such as HIV-1, HSV-1 and 2, poliovirus, VZV, and VSV. Compound 2 only showed weak antiviral activity against HSV-1 without cytotoxicity. Although the synthesized compounds did not exhibit an excellent antiviral activity, the successful method used in introducing the tert-azido group is expected to be generally utilized for the synthesis of nucleoside analogs with a tert-azido substituent.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15064793&dopt=Abstract penciclovir Denavir