The selectivity of action of an antiherpetic agent, 9-(2-hydroxyethoxymethyl) guanine

Elion, Gertrude B.; Furman, Phillip A.; Fyfe, James A.; Miranda, Paulo de; Beauchamp, Lilia M.; Schaeffer, Howard J.

doi:10.1002/(sici)1099-1654(199907/09)9:3<147::aid-rmv255>3.0.co;2-p

Cited by 133 publications

(167 citation statements)

References 13 publications

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“…6 It was reported that, once GCV entered the cells, it is readily phosphorylated by HSVtk, losing its ability to pass through cell membranes. 25,26 Thus, its half-life within the cell is about six-fold longer than that of unmodified GCV. 25,26 Preliminary data of Hematoxylin and eosin staining of 5-day-old LM05e, LM3 and B16 multicellular spheroids sections.…”

Section: Spheroids Displayed a High Fraction Of Quiescent Cellsmentioning

confidence: 99%

“…25,26 Thus, its half-life within the cell is about six-fold longer than that of unmodified GCV. 25,26 Preliminary data of Hematoxylin and eosin staining of 5-day-old LM05e, LM3 and B16 multicellular spheroids sections. Spheroids were collected, embedded in paraffin and cross-sections were stained for BrdU or hematoxylin and eosin as indicated in Materials and methods.…”

Section: Spheroids Displayed a High Fraction Of Quiescent Cellsmentioning

confidence: 99%

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Herpes simplex virus thymidine kinase/ganciclovir system in multicellular tumor spheroids

et al. 2004

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We have developed multicellular spheroids (MCS) established from LM05e and LM3 spontaneous Balb/c-murine mammary adenocarcinoma and B16 C57-murine melanoma derived cell lines as an in vitro model to study the efficacy of the herpes simplex virus thymidine kinase/ganciclovir (HSVtk/GCV) suicide system. We demonstrated for the first time that HSVtk-expressing cells assembled as MCS manifested a GCV resistance phenotype compared to the same cells grown as sparse monolayers. HSVtkexpressing LM05e, LM3 and B16 spheroids were 16-, three-and nine-fold less sensitive to GCV than their respective monolayers, even though they could express transgenes 10-, eight-and five-fold more efficiently. Mixed populations of HSVtkÀ and their respective bgal-expressing cells displayed a cell-type specific bystander effect that was higher in monolayers than in MCS. However, HSVtkÀexpressing cells in two-or three-dimensional cultures were always significantly more sensitive to GCV than the bgal-expressing counterparts, supporting the feasibility of this suicide approach in vivo. We present evidence showing that HSVtkexpressing tumor cells, when transferred from monolayers to MCS, displayed: (i) lower GCV cytotoxic activity and bystander effect; (ii) higher and efficient expression of genes transferred as lipoplexes; (iii) lower cell proliferation rates; and (iv) changes in intracellular Bax/Bcl-xL rheostat of mitochondria-mediated apoptosis. Cancer Gene Therapy ( A ntitumor suicide gene therapy is one of the emerging strategies against cancer. 1 It consists of the introduction into cancer cells of a gene, whose product is capable of converting a nontoxic prodrug into a cytotoxic drug. 2 One of such suicide genes, the thymidine kinase gene from the herpes simplex virus (HSVtk), in combination with the prodrug ganciclovir (GCV), has been extensively and successfully used for the treatment of a variety of cancers in some animal models. HSVtk can efficiently phosphorylate the guanosine analogue GCV and allows its further transformation, after subsequent phosphorylation by cellular kinases, into cytotoxic ganciclovir-triphosphate, which inhibits cellular DNA polymerases. 3 GCV-induced apoptosis is due to incorporation of the drug into DNA resulting in replication-dependent formation of DNA double-strand breaks and, at later stages, S and G 2 /M arrest. 4 As this therapeutic gene cannot be easily introduced into the whole cell population of a tumor, the successful eradication of tumors depends on a phenomenon called the bystander effect, by which the unmodified adjacent tumor cells are also sensitive to the GCV cytotoxic effect. 5,6 This bystander effect permits that the transfection of only a minority of tumor cells may lead to effective tumor regression. 6 Despite extensive preclinical evaluation both in vitro and in vivo in several experimental models, no studies have been undertaken examining a nonviral HSVtk/GCV suicide system in spheroids, a model that mimics the microregions of solid tumors. 7 Multicellular spheroids (MCS) have been us...

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Section: Spheroids Displayed a High Fraction Of Quiescent Cellsmentioning

confidence: 99%

Section: Spheroids Displayed a High Fraction Of Quiescent Cellsmentioning

confidence: 99%

Herpes simplex virus thymidine kinase/ganciclovir system in multicellular tumor spheroids

et al. 2004

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“…One of the most important characteristics of retrovirus is their preferential infection of the dividing cells, hence, the tumor has been primarily considered as a target of retroviralmediated gene therapy. Similar vectors carrying HSV-tk have been described in recent report for treatment of melanoma [14], lymphoma [15] and glioma cells [5].…”

Section: Discussionmentioning

confidence: 93%

“…The supernatant of the transfected cells (PA317-lacZ), with titer consistent to that of PA317tk (1 10 6 cfu/ml), was used to infect BEL-7402 and followed by X-gal staining (Fig 1). Since the essential titer of retrovirus for efficient delivery of gene to target cells was 5 10 5 cfu/ml [12], this titer of 1 10 6 cfu/ml was theoretically adequate to produce satisfied gene transfers. It was obviously seen in Southern blot that a 3.4 kb band was generated when hybridizing genomic DNA of PA317tk and BEL-7402tk with HSV-tk BamH I fragment (Fig 2a).…”

Section: Efficiency Of Gene Transfer and Expression Of Tk Genementioning

confidence: 99%

“…The target cancer cells, after transfected by HSV-tk, can be killed with treatment of ganciclovir drug (GCV). Ganciclovir is nucleotide analog which, upon phosphorylated by HSV-tk, could act as inter-metabolic substance and thereafter terminate DNA chain of the replicating cancer cells [5]. Hence, HSV-tk gene could induce ultimately a direct killing or suicide effect in the transfected cells.…”

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confidence: 99%

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Retrovirus-mediated herpes simplex virus thymidine kinase gene therapy approach for hepatocellular carcinoma

Gao

Dai

1999

Cell Res

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The therapeutic effect of herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system on hepatocellular carcinoma was studied in this experiment. The tk-containing retroviral recombinants were used to infect hepatoma cells (BEL-7402) and the cells were treated with ganciclovir (0-1000 μg/ ml). The results showed that HSV-tk gene could be efficiently transferred in vitro into hepatoma cells and stably expressed. The growth potential of the tk-containing cells was significantly inhibited by GCV (P < 0.01) as compared to the non-tkcontaining cells. The antitumor effect of HSV-tk/GCV system was also produced ex vivo in tk-containing tumor of nude mice as characterized by a marked decrease in tumor growth after GCV treatment contrary to a progressive enlargement of nontk-containing tumors. Although the histological examination demonstrated that the efficiency of the gene transfer was less than 30%, the killing effect of HSV-tk/GCV system on hepatocellular carcinoma was still significantly generated. The proper mechanism of HSV-tk gene therapy on hepatic tumor referred as bystander effect in therapeutic approach has not been found in this study and required to be explored further.

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Effect of Pritelivir Compared With Valacyclovir on Genital HSV-2 Shedding in Patients With Frequent Recurrences

Wald

Timmler

Magaret

et al. 2016

JAMA

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IMPORTANCE Current therapy of herpes infections relies on nucleoside analogues. Pritelivir is a well-tolerated novel herpes simplex virus (HSV) helicase-primase inhibitor that reduced genital shedding and lesions. OBJECTIVE To compare the efficacy of pritelivir with valacyclovir for suppression of genital HSV-2 infection. DESIGN, SETTING, AND PARTICIPANTS A phase 2, randomized, double-blind, crossover clinical trial at clinical research centers in 4 US cities (October 2012-July 2013) compared daily oral doses of 100 mg of pritelivir with 500 mg of valacyclovir. The planned sample size was 98 adults, allowing for detection of a 50% reduction in viral shedding between the study treatments. Healthy adults with 4 to 9 annual genital HSV-2 recurrences were eligible. Ninety-one participants were randomized: 45 to receive pritelivir and 46 to receive valacyclovir first when the US Food and Drug Administration placed the trial on clinical hold based on findings in a concurrent nonclinical toxicity study, and the sponsor terminated the study. INTERVENTIONS Participants took the first drug for 28 days followed by 28 days of washout before taking the second drug for 28 days. Throughout treatment, the participants collected genital swabs 4 times daily for testing by HSV polymerase chain reaction assays. MAIN OUTCOMES AND MEASURES The primary end point was within-participant genital HSV shedding while receiving pritelivir compared with valacyclovir. Secondary end points included the quantity of HSV in positive swabs and the frequency of genital lesions and shedding episodes. RESULTS Of the 91 randomized participants (median age, 48 years; 57 women [63%]), 56 had completed both treatment periods at the time of the study's termination. In intent-to-treat analyses, HSV shedding was detected in 2.4% (173 of 7276) of swabs during pritelivir treatment compared with 5.3% (392 of 7453) during valacyclovir treatment (relative risk [RR], 0.42; 95% CI, 0.21 to 0.82; P = .01). In swabs with HSV, the mean quantity of HSV was 3.2 log 10 copies/mL during pritelivir treatment vs 3.7 log 10 copies/mL during valacyclovir treatment (difference, −0.1; 95% CI, −0.6 to 0.5; P = .83). Genital lesions were present on 1.9% of days in the pritelivir group vs 3.9% in the valacyclovir group (RR, 0.40; 95% CI, 0.17-0.96; P = .04). The frequency of shedding episodes did not differ by group, with 1.3 per person-month for pritelivir and 1.6 per person-month for valacyclovir (RR, 0.80; 95% CI, 0.52 to 1.22; P = .29). Treatment-emergent adverse events occurred in 62.3% of participants in the pritelivir group and 69.2% of participants in the valacyclovir group. CONCLUSIONS AND RELEVANCE Among adults with frequently recurring genital HSV-2, the use of pritelivir compared with valacyclovir resulted in a lower percentage of swabs with HSV detection over 28 days. Further research is needed to assess longer-term efficacy and safety.

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The selectivity of action of an antiherpetic agent, 9-(2-hydroxyethoxymethyl) guanine

Cited by 133 publications

References 13 publications

Herpes simplex virus thymidine kinase/ganciclovir system in multicellular tumor spheroids

Herpes simplex virus thymidine kinase/ganciclovir system in multicellular tumor spheroids

Retrovirus-mediated herpes simplex virus thymidine kinase gene therapy approach for hepatocellular carcinoma

Effect of Pritelivir Compared With Valacyclovir on Genital HSV-2 Shedding in Patients With Frequent Recurrences

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