Suppression of frequently recurring genital herpes: acyclovir v inosine pranobex

Inosine Pranobex Deserves Attention as a Potential Immunomodulator to Achieve Early Alteration of the COVID-19 Disease Course

Since its licensing in 1971, the synthetic compound inosine pranobex has been effectively combating viral infections, including herpes zoster, varicella, measles, and infections caused by the herpes simplex virus, human papillomavirus, Epstein-Barr virus, cytomegalovirus, and respiratory viruses. With the emergence of SARS-CoV-2, new and existing drugs have been intensively evaluated for their potential as COVID-19 medication. Due to its potent immunomodulatory properties, inosine pranobex, an orally administered drug with pleiotropic effects, can, during early treatment, alter the course of the disease. We describe the action of inosine pranobex in the body and give an overview of existing evidence collected to support further efforts to study this drug in a rigorous clinical trial setup.

Inosine Pranobex: A Key Player in the Game Against a Wide Range of Viral Infections and Non-Infectious Diseases

Inosine pranobex (IP), commonly known as inosine acedoben dimepranol, isoprinosine and methisoprinol, has been proven to positively impact the host’s immune system, by enhancing T-cell lymphocyte proliferation and activity of natural killer cells, increasing levels of pro-inflammatory cytokines, and thereby restoring deficient responses in immunosuppressed patients. At the same time, it has been shown that it can affect viral RNA levels and hence inhibit growth of several viruses. Due to its immunomodulatory and antiviral properties, and its safety profile, it has been widely used since 1971 against viral infections and diseases, among which subacute sclerosis panencephalitis, herpes simplex virus, human papilloma virus, human immunodeficiency virus, influenza and acute respiratory infections, cytomegalovirus and Epstein–Barr virus infections. Following an analysis of almost five decades of scientific literature since its original approval, we here summarize in vivo and in vitro studies manifesting the means in which IP impacts the host’s immune system. We also provide a synopsis of therapeutic trials in the majority of which IP was found to have a beneficial effect. Lastly, positive results from limited studies, suggesting the putative future use of IP in new therapeutic indications are briefly described. In order to support use of IP against viral infections apart from those already approved, and to establish its use in clinical practice, further well-designed and executed trials are warranted.

Funding: Ewopharma International.

Oral antiviral therapy for prevention of genital herpes outbreaks in immunocompetent and nonpregnant patients

BACKGROUND

Genital herpes is caused by herpes simplex virus 1 (HSV-1) or 2 (HSV-2). Some infected people experience outbreaks of genital herpes, typically, characterized by vesicular and erosive localized painful genital lesions.

OBJECTIVES

To compare the effectiveness and safety of three oral antiviral drugs (acyclovir, famciclovir and valacyclovir) prescribed to suppress genital herpes outbreaks in non-pregnant patients.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the search portal of the World Health Organization International Clinical Trials Registry Platform and pharmaceutical company databases up to February 2014. We also searched US Food and Drug Administration databases and proceedings of seven congresses to a maximum of 10 years. We contacted trial authors and pharmaceutical companies.

SELECTION CRITERIA

We selected parallel-group and cross-over randomized controlled trials including patients with recurrent genital herpes caused by HSV, whatever the type (HSV-1, HSV-2, or undetermined), with at least four recurrences per year (trials concerning human immunodeficiency virus (HIV)-positive patients or pregnant women were not eligible) and comparing suppressive oral antiviral treatment with oral acyclovir, famciclovir, and valacyclovir versus placebo or another suppressive oral antiviral treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected eligible trials and extracted data. The Risk of bias tool was used to assess risk of bias. Treatment effect was measured by the risk ratio (RR) of having at least one genital herpes recurrence. Pooled RRs were derived by conventional pairwise meta-analyses. A network meta-analysis allowed for estimation of all possible two-by-two comparisons between antiviral drugs.

MAIN RESULTS

A total of 26 trials (among which six had a cross-over design) were included. Among the 6950 randomly assigned participants, 54% (range 0 to 100%) were female, mean age was 35 years (range 26 to 45.1), and the mean number of recurrences per year was 11 (range 6.3 to 17.8). Duration of treatment was two to 12 months. Risk of bias was considered high for half of the studies and unclear for the other half. A total of 14 trials compared acyclovir versus placebo, four trials compared valacyclovir versus placebo and 2 trials compared valacyclovir versus no treatment. Three trials compared famciclovir versus placebo. Two trials compared valacyclovir versus famciclovir and one trial compared acyclovir versus valacyclovir versus placebo.We analyzed data from 22 trials for the outcome: risk of having at least one clinical recurrence. We could not obtain the outcome data for four trials. In placebo-controlled trials, there was a low quality evidence that the risk of having at least one clinical recurrence was reduced with acyclovir (nine parallel-group trials, n = 2049; pooled RR 0.48, 95% confidence interval (CI) 0.39 to 0.58), valacyclovir (four trials, n = 1788; pooled RR 0.41, 95% CI 0.24 to 0.69), or famciclovir (two trials, n = 732; pooled RR 0.57, 95% CI 0.50 to 0.64). The six cross-over trials showed larger treatment effects on average than the parallel-group trials. We found evidence of a small-study effect for acyclovir placebo-controlled trials (adjusted pooled RR 0.61, 95% CI 0.49 to 0.75). In analyzing parallel-group trials by daily dose, no clear evidence was found of a dose-response relationship for any drug. In head-to-head trials, the risk of having at least one recurrence was increased with valacyclovir rather than acyclovir (one trial, n = 1345; RR 1.16, 95% CI 1.01 to 1.34) and was not significantly different from that seen with famciclovir as compared with valacyclovir (one trial, n = 320; RR 1.18, 95% CI 0.86 to 1.63).We included 16 parallel-arm trials in a network meta-analysis and we were unable to determine which of the drugs was most effective in reducing the risk of at least one clinical recurrence (after adjustment for small-study effects, pooled RR 0.83, 95% CI 0.61 to 1.11 for valacyclovir vs acyclovir; pooled RR 1.04, 95% CI, 0.71 to 1.49 for famciclovir vs acyclovir; and pooled RR 1.26, 95% CI 0.89 to 1.75 for famciclovir vs valacyclovir). Safety data were sought but were reported as total numbers of adverse events.

AUTHORS' CONCLUSIONS

Owing to risk of bias and inconsistency, there is low quality evidence that suppressive antiviral therapy with acyclovir, valacyclovir or famciclovir in pacients experiencing at least four recurrences of genital herpes per year decreases the number of pacients with at least one recurrence as compared with placebo. Network meta-analysis of the few direct comparisons and the indirect comparisons did not show superiority of one drug over another.

Aciclovir. A reappraisal of its antiviral activity, pharmacokinetic properties and therapeutic efficacy

Aciclovir (acyclovir) is a nucleoside analogue with antiviral activity in vitro against the herpes simplex viruses (HSV), varicella zoster virus (VZV), Epstein-Barr virus (EBV), cytomegalovirus (CMV) and human herpesvirus 6 (HHV-6). Topical, oral or intravenous aciclovir is well established in the treatment of ophthalmic, mucocutaneous and other HSV infections, with intravenous aciclovir the accepted treatment of choice in herpes simplex encephalitis. The efficacy of aciclovir is increased with early (preferably during the prodromal period) initiation of treatment but, despite significant clinical benefit, viral latency is not eradicated, and pretreatment frequencies of recurrence usually continue after episodic acute treatment is completed. Intravenous administration has also shown benefit in the treatment of severe complications of HSV infection in pregnancy, and neonatal HSV infections. Recurrence of HSV has been completely prevented or significantly reduced during suppressive therapy with oral aciclovir in immunocompetent patients. Use of oral aciclovir is effective but controversial in the treatment of otherwise healthy individuals with varicella (chickenpox), and in some countries it has been recommended for use only in cases which may be potentially severe. The development of rash and pain associated with herpes zoster (shingles) is attenuated with oral or intravenous aciclovir therapy, ocular involvement is prevented, and post-herpetic neuralgia appears to be decreased. Similarly, in a few patients with zoster ophthalmicus, oral aciclovir has reduced the frequency and severity of long term ocular complications and post-herpetic neuralgia, and herpes zoster oticus is improved with intravenous aciclovir. Oral aciclovir has prevented recurrence of HSV genital or orofacial infections during suppressive therapy in > 70% of immunocompetent patients in most clinical trials. Suppression of latent HSV, VZV and CMV infections has been achieved in many immunocompromised patients receiving the oral or intravenous formulations. Aciclovir also appears to offer partial protection from invasive CMV disease in CMV-seropositive bone marrow transplant recipients. The few comparative trials published have shown aciclovir to be at least as effective as other investigated antivirals in the treatment of HSV infections in immunocompetent patients, and more effective than inosine pranobex in the prophylaxis of genital herpes. Similarly, in isolated clinical trials, oral aciclovir appears as effective as topical idoxuridine and oral brivudine in some parameters in immunocompetent patients with VZV infections, and the intravenous formulation appears at least as effective as oral brivudine and intravenous vidarabine in treating these infections in immunocompromised patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Acyclovir vs isoprinosine (immunovir) for suppression of recurrent genital herpes simplex infection

OBJECTIVE

To compare the efficacy and safety of oral acyclovir (400 mg twice daily) with oral isoprinosine (500 mg twice daily) in the suppression of recurrent genital herpes.

DESIGN

Double-blind, double-dummy, randomised, controlled, parallel group trial.

SETTING

13 centres in UK, Belgium and Germany.

SUBJECTS

127 immunocompetent patients with frequently recurring genital herpes.

MAIN OUTCOME MEASURES

Proportions of patients reporting recurrences, recurrence frequency, and mean duration of lesions during breakthrough recurrences in each treatment group during a 6 month treatment period; time to first recurrence during treatment and follow-up after treatment cessation.

RESULTS

During treatment, acyclovir recipients showed significant differences (p < 0.05) when compared with isoprinosine recipients in terms of a lower proportion reporting recurrences (31% vs 96%), a reduced mean number of reported recurrences per patient (0.6 vs 3.6), a shorter mean duration of breakthrough lesions (6.4 days vs 8.2 days), and a longer mean time (standard error) to first recurrence (143.7 (9.1) days vs 40.5 (5.4) days. The mean time to first recurrence after treatment cessation did not differ between the two groups. As compared with placebo recipients, isoprinosine treated patients had an increased recurrence frequency (3.6 vs 2.5) during treatment, and a shorter time to first recurrence after treatment cessation. All treatments were well tolerated without serious adverse events or toxicity.

CONCLUSIONS

Acyclovir is very effective in suppressing recurrent genital herpes and is clearly superior to isoprinosine which is not clinically useful in the dosage studied.