ANTIVIRAL TREATMENT FOR GENITAL herpes may be provided to patients in 1 of 2 ways: daily suppressive therapy to reduce the frequency of recurrences or episodic treatment of recurrent episodes, treating outbreaks as they arise. Both strategies have benefits for selected patients, based on their individual situation,1 although patients may prefer suppressive therapy in many cases.2 Because the registrational trials of all of the available antiviral drugs approved for suppressive therapy enrolled subjects with established histories of recurrent genital herpes,3–7 many providers who offer suppressive therapy as an option to appropriate patients often do so, based on frequency of recurrences.8 For that reason, such providers may not consider suppression at the time of initial diagnosis, before a recurrence pattern has been established.
Patients with more severe primary infections are more likely to have recurrences and a shorter time to first recurrence than those with mild primary infections.9 Previous studies of persons with initial symptomatic episodes of genital herpes simplex virus type 2 (HSV-2) infections have shown that approximately 90% of these patients have at least 1 outbreak during the first year of follow-up and 20% of these patients have more than 10 outbreaks per year.9,10 In addition, persons with recent genital HSV-2 infection shed virus more frequently (up to 42% of days)11 and are presumed to be at higher risk of transmitting HSV-2 in the first few months after initial infection.9,12,13
A recent double blind, randomized, placebo-controlled trial examined the strategy of placing subjects with newly diagnosed genital herpes on suppressive therapy with valacyclovir.14 Although this study demonstrated reduced recurrences and improved quality of life in the valacyclovir recipients, it was a small pilot study that had a number of limitations. The purpose of the current study was to confirm and expand upon some of the observations made in that pilot study by conducting a larger study with more detailed follow up of study subjects.
Subjects and Methods
The study population consisted of immunocompetent men and women ≥18 years of age who were otherwise healthy, had not received suppressive antiherpetic therapy before enrollment and were clinically symptomatic with a first recognized episode of HSV-2 genital herpes at the time of the screening visit or within 3 months before the screening visit. All study subjects were either HSV-2 antibody positive at screening or had a positive culture or polymerase chain reaction (PCR) test for HSV-2 obtained from a genital lesion. Seventy-five investigators at 74 sites in the United States, Canada, Argentina, Brazil, and Chile participated in the study. Written informed consent was obtained from each subject before the performance of any study-specific procedures using a consent form approved by an appropriate ethical review committee.
This was a randomized, double-blind, parallel, placebo-controlled, multicenter study and was conducted between June 16, 2004 and July 26, 2006. Subjects were randomized to either valacyclovir 1 g once daily or matching placebo once daily (2:1 ratio, respectively). The 1 g dose was chosen to optimize treatment of subjects, 20% of whom would be expected to have 10 or more outbreaks per year.9 Subjects participated in the study for 24 weeks. Eligibility was determined at the screening visit; those meeting entry criteria were subsequently enrolled at the randomization visit (7–14 days following the screening visit). Subjects with lesions at screening were healed before randomization and subjects who received acute antiviral therapy had to have completed treatment at least 72 hours before randomization. Subjects were seen in clinic for 6 study visits, each 28 days apart (±5 days). Genital swabs for baseline HSV-2 culture and PCR were collected from subjects who presented with lesions at screening; genital swabs of lesions for viral culture were collected at every recurrence of genital herpes after entry into the study.
Randomization and Treatment Allocation
Subjects were assigned to valacyclovir or placebo in a 2:1 ratio in randomization blocks of 6, using a central randomization system. Study drug was supplied as film coated caplets containing either 500 mg valacyclovir or matching placebo. During double-blind suppressive therapy, subjects were provided with study drug and instructed to take 2 caplets orally once daily without regard to meals. If a subject experienced a symptomatic recurrence during the study, a visit to the site was required for lesion verification and evaluation. Subjects temporarily discontinued double-blind suppression medication and received open-label episodic treatment with valacyclovir 500 mg twice daily for 3 days if they experienced a genital herpes recurrence (for Argentina, Brazil, and Chile, treatment was for 5 days per local regulatory approval). They resumed double-blind daily study medication following completion of open-label treatment. Subjects whose lesions had not healed following completion of the initial open-label treatment period, were given a second course of open-label valacyclovir before resuming masked study drug, if deemed appropriate by the clinical investigator.
Study Assessments and Endpoints
Baseline assessments included collection of demographic information, laboratory confirmation of the subject's initial HSV-2 genital herpes diagnosis (this could have been at screening or within 3 months of the screening visit), review of current medical conditions and concurrent medications, genital examination (including a vaginal speculum examination for women), urine pregnancy testing, as well as HSV-1 and HSV-2 serology (HerpeSelect, Focus Technologies, Cypress, CA) and clinical chemistry analysis. The HerpeSelect tests were interpreted according to the criteria approved for the test: EIA values <0.9 were negative, values >1.1 were positive, and values between 0.9 and 1.1 were equivocal. No confirmatory testing was done. Subjects with an equivocal serological test were considered negative for any analysis that used serological test results. If a genital lesion was present at the screening visit, a swab sample was collected from the lesion for herpes viral culture (Quest Diagnostics Clinical Trials, Van Nuys, CA) and type-specific HSV-2 PCR analysis (by the University of Washington Virology Research Laboratory, Seattle, WA).15–17 Swab samples were also collected at every genital herpes recurrence visit for herpes culture only. HSV-2 positive isolates from genital specimens obtained at screen or during a recurrence were sent to a designated central laboratory (ViroMed Laboratory, Minneapolis, MN) for acyclovir (ACV) sensitivity testing by plaque reduction assay at the end of the study.18
The primary endpoint of the study was the time of first genital herpes recurrence. Secondary endpoints included the number of genital herpes recurrences within the 24-week study period, and the percent of genital HSV-2 isolates resistant to ACV.
The primary population for assessing efficacy and safety was the Intent-to-Treat (ITT) population, defined as all subjects randomized to treatment who were administered at least 1 dose of investigational product. Statistical comparisons were made between the valacyclovir arm and the placebo arm for efficacy endpoints only. Kaplan-Meier method was used to assess the difference and the associated 95% confidence intervals in survival estimates at 24 weeks on the primary efficacy endpoint between the 2 treatment groups. The time to first genital herpes recurrence was assessed by log-rank test. This parameter was further evaluated by hazard ratios and associated 95% confidence intervals using a Cox proportional hazards model. Both univariate and multivariate Cox regression analyses were performed, although the multivariate analysis was exploratory and was used to further investigate the impact of treatment on time to first recurrence of HSV-2 genital herpes while adjusting for other potentially relevant covariates (race, age, gender, and HSV-2 seronegative status at screening). Wilcoxon rank sum test was used to analyze the number of genital herpes recurrences per month. Demographic and safety data were assessed by summary statistics only. All statistical analyses were performed using SAS software, Version 8.2 (SAS Institute, Cary, NC).
Retention and Demographics of Subjects
Three hundred eighty-four subjects were randomized into this study, 128 to placebo and 256 to daily valacyclovir. Of the 384 subjects randomized, 277 completed the study [93 placebo (73%), 184 valacyclovir (72%)] and 106 prematurely withdrew [35 placebo (27%), 71 valacyclovir (28%)] (Fig. 1). The total of 71 withdrawals in the valacyclovir group does not include 1 subject who withdrew before taking any study medication. The most common reason for premature withdrawal was a protocol violation (e.g., failure to comply with the study visit schedule) by the subject [8 placebo (6%), 23 valacyclovir (9%)].
Demographics features were similar for both treatment groups (Table 1). The study population was predominately women (72% in the placebo group, 69% in the valacyclovir group) and approximately half were white (53% in the placebo group, 49% in the valacyclovir group). The mean time from initial diagnosis of genital herpes to the screening visit was 0.8 months, reflecting the fact that the majority of subjects received their initial diagnosis of HSV-2 genital herpes at the screening visit of this study. Eighty percent of the subjects were HSV-2 seropositive (newly diagnosed but cannot confirm a new infection) and 20% were seronegative (clearly newly infected) at the screening visit. A total of 211 subjects (61.5%) had a positive test for HSV-2 (culture or PCR) from genital lesion material at the time of diagnosis. The proportion of subjects diagnosed with serology or detection of virus in genital lesions was similar in the 2 treatment groups.
Adherence to double-blind study medication was calculated as a percentage of caplets that should have been taken per protocol, based on pill counts assuming that all caplets not returned to the study site were taken as prescribed. We defined adherence as taking at least 80% of the caplets dispensed. Using this definition, 78% (100 of 128) of placebo recipients were adherent whereas 79% (201 of 255) of valacyclovir recipients were adherent.
Primary Efficacy Endpoint
The primary efficacy endpoint was the time to first HSV-2 genital herpes recurrence. Time to first recurrence of genital herpes was significantly shorter in the placebo group compared with the valacyclovir group (P <0.001, Log-rank test) (Fig. 2). Kaplan-Meier analysis demonstrated the estimated recurrence-free rates at 24 weeks were approximately 43% on placebo and 71% on valacyclovir (difference in recurrence-free estimates of 27.3%, 95% CI: 16%–39%). The corresponding median recurrence-free time, that is, the time by which 50% of subjects had their first genital herpes recurrence, was 115 days for the placebo group; a median time for the valacyclovir group could not be calculated because fewer than half of the subjects experienced a recurrence during the 24-week study period. A univariate Cox regression analysis showed that subjects taking valacyclovir were at a significantly reduced risk of a first recurrence of HSV-2 genital herpes compared with those taking placebo [hazard ratio 0.40 (95% CI: 0.28–0.57), P <0.001]. Furthermore, an exploratory multivariate Cox regression analysis also demonstrated that valacyclovir treatment was a significant factor in reducing the risk of a first recurrence of HSV-2 genital herpes with a hazard ratio of 0.35 [95% CI: (0.24–0.5), P <0.001], while adjusting for other covariates in the model (Table 2). Age (per year) was also a significant factor with older subjects being less likely to recur in the multivariate Cox regression model. Race, gender, and being HSV-2 antibody negative at screening were not associated with the likelihood of recurrence. A conservative sensitivity analysis of the primary endpoint whereby any subject who withdrew early from the study was assumed to have a genital herpes recurrence at the time of withdrawal, showed an estimated 32% of subjects recurrence-free on placebo compared with 51% recurrence-free on valacyclovir, a reduction of 37% (P <0.001).
The number of recurrences observed on study is shown in Figure 3. Panel A shows data for the entire ITT population and includes subjects whose number of recurrences was not known because they were discontinued early, but had not yet had a recurrence. The proportion of the population with no recurrences on study was 64.7% for valacyclovir recipients and 46.1% for placebo recipients, a reduction of 29%. Panel B shows data for per protocol population, subjects who completed the 24 week observation period without major protocol violations. In this subset, 72.7% of valacyclovir recipients had no recurrences compared with 42.9% of placebo recipients, a reduction of 41%.
The mean number of genital herpes recurrences per month was 0.48 (SD 1.86) for placebo recipients and 0.11 (SD 0.25) for valacyclovir recipients (P <0.001, Wilcoxon rank sum test). This calculates to an annualized number of recurrences of 5.8 for subjects on placebo and 1.3 for those on valacyclovir.
There were a total of 221 HSV-2 culture samples tested for ACV-susceptibility by the analytical laboratory. Three possible ACV-resistant (ACV-R, 50% inhibitory concentration >2.0 μg/mL) viral isolates were initially reported. By laboratory protocol, these possible ACV-R isolates were retested because the 50% inhibitory concentration for each isolate was within 2 standard deviations of the 2.0 μg/mL cut-off for the plaque reduction assay. The 3 isolates (1.4% of the total number of isolates tested) that were initially reported as resistant were all susceptible to ACV in the repeat assays. One of these questionable isolates was obtained at screening, before administration of study drug. The other 2 isolates were from a single subject and were obtained from recurrence visits for outbreaks while on placebo.
Ninety-eight of 128 (77%) subjects in the placebo group and 185 of 255 (73%) subjects in the valacyclovir group reported at least 1 adverse event during the study. The type, location, and severity of the adverse events reported were similar in the valacyclovir and placebo arms. There were no serious adverse events that were related to study medication.
Previously reported studies using valacyclovir and other agents used for the treatment of recurrent genital herpes have been conducted in patients with a recognized recurrent disease history (e.g., Refs. 3–7 among many others). In contrast, the current study evaluated the use of daily valacyclovir for the suppression of genital herpes recurrences in subjects newly diagnosed with HSV-2 genital herpes, a population that had been little studied previously. Although these subjects would be expected to have recurrences if left untreated, they did not have an established pattern of genital herpes recurrences at the time of enrollment.
The observed effect of valacyclovir compared with placebo on reduction of genital herpes recurrences was consistent with that reported in a smaller pilot study14 and in studies of suppressive therapy in subjects with established recurrence patterns.5 The current study enhances the observations made in the pilot study because the current study was larger and involved more study visits to provide more precise measurements of recurrence frequency and study drug adherence. In addition, the current study enrolled only subjects with documented HSV-2 genital herpes, providing a more uniform study population about HSV type. The pilot study14 raised a note of caution because only 47% of their subjects on valacyclovir were recurrence-free during the study, a number that was somewhat lower than some previous studies of subjects with established recurrence patterns.5,7,19 The current study was more consistent with those previous studies finding 64.7% of the valacyclovir recipients in the ITT population to be recurrence-free at 6 months and 72.7% of the valacyclovir population who were known to complete the study without major protocol violations to be recurrence-free. The reason for the difference between the pilot study and the current study could be due to our larger sample size or because we documented recurrences with clinic visits while the pilot study relied on telephone reporting by the study subject that may have overestimated recurrences. We conclude that recently diagnosed persons with genital HSV-2 infection respond to suppressive valacyclovir therapy in a manner similar to that described for valacyclovir (and other antiviral) recipients with established recurrence patterns. Another important question that the current study did not address is whether suppressive valacyclovir therapy in recently diagnosed persons reduces viral shedding to the same extent as it does in persons with established disease. Preliminary results from a recently completed study suggest that established and recently acquired disease are similar in this respect as well.20
In addition to valacyclovir therapy, the other factor that was associated with a decreased likelihood of recurrence in the multivariate analysis was older age. This association between age and recurrence frequency after an initial episode of genital herpes has been noted in previous studies.9,21 The biologic basis of this observation is uncertain and was not explained in the earlier studies. Our inability to detect any difference in recurrence pattern between subjects with a documented recent infection and those whose duration of infection was unknown could be due to the relatively small proportion of our subjects who had a documented new infection (20%). The pilot study14 had 53% of its subjects with documented new HSV-2 infections. This disparity could account for some of the small differences noted between the 2 studies.
The frequency of isolation of resistant HSV-2 (at most 1.4%) from immunocompetent subjects in this current study is in agreement with that reported in previous studies in similar populations,22–24 even assuming that the 3 borderline isolates in question were ACV resistant. It is important to note that all 3 isolates failed to confirm as resistant in repeat assays, indicating that they are unlikely to be clinically resistant to ACV (and valacyclovir). Because these isolates were obtained from subjects who had not received valacyclovir, they were most likely naturally occurring strains with lower susceptibility to ACV and not resistant strains that emerged under selective pressure from daily valacyclovir, as has been noted in previous studies.25
As originally designed, the protocol called for enrollment of subjects newly infected with HSV-2 as demonstrated by HSV-2 seronegative status combined with positive HSV-2 culture or PCR, or recent documented HSV-2 seroconversion. However, it became apparent that culture and serologic documentation of new infection were extremely difficult to verify in view of inconsistent methods used for diagnosing genital herpes. Therefore, the study was amended to eliminate the requirement for HSV-2 seronegativity at diagnosis and enroll subjects who were newly diagnosed with a first clinically recognized episode of HSV-2, regardless of serologic status. It is acknowledged that first recognized episodes of genital herpes may not represent new infection and that it is possible that previous episodes may have escaped detection. However, the study enrollment criteria reflect the real-world situation faced by a clinician seeing a patient with a first recognized episode of genital herpes. In most cases, laboratory documentation regarding previous infections would not be available and treatment decisions must be made using the information at hand.
One limitation of this study was the relatively high rate of subject attrition for various reasons including protocol violation, lost to follow up, and personal decisions to withdraw. The reasons for the high attrition rate compared with studies of suppression of genital herpes in subjects with established recurrence patterns are unknown. One possible explanation is the fact that most subjects in the current study had not emotionally adjusted to the diagnosis of genital herpes and may have had problems with the frequent reminders of that diagnosis that participation in a study provided. In addition, because the subjects had not experienced frequent recurrences of genital herpes at the time of enrollment, the motivation for staying in the study may have been lower than in studies that enrolled subjects with a history of frequent recurrences. Unlike the previous pilot study,14 the current study did not collect any quality of life or other emotional measures, so we can only speculate on motivations. Despite the relatively high attrition rate, we think that the large sample size and analytical approach make our observations legitimate.
Before this study and the pilot trial,14 there were limited data to guide clinicians in management of patients who had no established recurrence history. Episodic treatment (or no treatment) has often been used until a recurrence pattern is established. In this study valacyclovir was demonstrated to significantly reduce the frequency of herpes recurrences in this population compared with episodic treatment (placebo suppression group) and the pilot study demonstrated that subjects on suppressive therapy had an improvement in quality of life measures. Clinicians should consider suppressive therapy as another treatment option in newly diagnosed patients, especially in adolescents,26 those with difficult psychological adjustments, or those who have an uninfected partner and are concerned about transmission. The latter group is especially important in light of the recent observation that the risk of transmission of HSV-2 to an uninfected partner is unrelated to the frequency of clinical recurrences in the HSV-2-infected partner.27
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