Inosine pranobex in the treatment of HIV infection: a review

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.

Multicenter randomized study of inosine pranobex versus acyclovir in the treatment of recurrent herpes labialis and recurrent herpes genitalis in Chinese patients

The objective of the study is to evaluate the efficacy and safety of oral inosine pranobex as compared with acyclovir in the treatment of recurrent herpes labialis (RHL) and recurrent herpes genitalis (RHG). A multicenter double-blind, double-dummy, randomized, controlled, parallel group trial was conducted in 144 patients with RHL and 144 RHG. Patients were assigned to treatment in one of two groups: (i) inosine pranobex group (active inosine pranobex, 1 g four times daily, and acyclovir placebo); or (ii) acyclovir group (active acyclovir, 200 mg five times daily, and inosine pranobex placebo). The total symptom score (TSS) of patients with RHL did not differ in the inosine pranobex and acyclovir group on the 3rd or 7th day of treatment. There was also no difference in the efficacy rates between the two groups. No difference of TSS was observed between patients with RHG taking inosine pranobex and acyclovir on days 3 or 5 of the treatment, respectively. The short-term clinical recurrence rate of RHG at 3-month follow-up was much lower in the inosine pranobex group than acyclovir group. The incidence of hyperuricemia was higher in the inosine pranobex group than acyclovir group. In conclusion, inosine pranobex was as effective as acyclovir in treating RHL and RHG with significantly greater reduction of the short-term recurrence rate of herpes genitalis at 3-month follow up. Long-term recurrence rates at 6 months or longer remain to be determined. Hyperuricemia should be monitored during the treatment.

Pharmacokinetic study of inosiplex tablets in healthy Chinese volunteers by hyphenated HPLC and tandem MS techniques

Inosiplex is a compound formulation composed of inosine and p-acetaminobenzoic acid (PABA) salt of N,N-dimethylamino-2-propanol (DIP). This study was to investigate the clinical plasma pharmacokinetic properties of DIP and PABA after single and multiple oral doses of inosiplex tablets in healthy Chinese volunteers. The established LC/MS/MS method for plasma DIP determination had a linear range of 0.02–10 µg/mL, and the HPLC method for plasma PABA determination had a linear range of 0.05–40 µg/mL. Linear pharmacokinetic characteristics were found with single oral doses of 0.5, 1.0 and 2.0 g. No obvious accumulation effects were observed for DIP and PABA.

Isoprinosine affects serum cytokine levels in healthy adults

Isoprinosine is a synthetic purine derivative with immunomodulatory and antiviral properties, which result from an apparent in vivo enhancement of host immune responses. To evaluate the serum levels of certain cytokines during and after isoprinosine treatment, we assigned 10 healthy volunteers to receive isoprinosine 1 g, 3 times daily, 5 consecutive days weekly. Both treatment and follow-up phase last 3 weeks. Interferon-gamma (IFN-gamma), interleukin-2 (IL-2), IL-10, and tumor necrosis factor-alpha (TNF-alpha) were measured in serum using commercial ELISA kits at baseline, 7th, 10th, 14th, 21st, 28th, 35th, and 42nd day. We observed an increase in serum levels of all measured cytokines at 7th to 10th day. The levels of IL-2 had another raise at 42nd day after drop to initial values (P < 0.05; P < 0.001, respectively). Those of IL-10 held up enhanced from 7th to 28th day of measurement (P < 0.01). There was a nearly flat line of values of TNF-alpha after initial slight increase at 10th day. We found a moderate negative correlation between IFN-gamma and IL-2, IL-10, and TNF-alpha (Spearman's r: -0.63, -0.62, -0.63; P < 0.05, respectively). We have demonstrated the immunomodulating properties of isoprinosine in healthy adults. It suggests resumption of the research with up-to-date methods to elucidate the mechanisms of action of inosine pranobex and maybe the other inosine compounds in different clinical settings.

Immunomodulators in infectious diseases: panoply of possibilites

Infections which caused ravages in the past centuries are again resurgent and newly emerging pathogens capable of human diseases continue to surface. Multidrug antibiotic resistance has turned into a major medical problem. Judicious concepts for combating infections in the 21st century have acquired a new poignancy. Immunomodulators of natural, synthetic, and recombinant origin can stimulate host defense mechanisms for the prophylaxis and treatment of diverse viral, bacterial, parasitic and fungal diseases. Some immunomodulator preparations are already licensed for use in patients and numerous others are being extensively investigated in preclinical and clinical studies. Immunomodulators offer a novel adjunct to established antimicrobial therapies.

Immunomodulatory agents for prophylaxis and therapy of infections

The advent of the antibiotic era ushered in a shift towards non-pathogen-specific therapy of infectious diseases. This led to an overt emphasis on targeting microbial pathogens while strategies directed towards enhancing host immunity were neglected. In an effort to decrease sole reliance on antimicrobials, the time has come for a critical reappraisal of nonantibiotic, albeit immune response-enhancing substances. The diverse array of natural, synthetic, and recombinant immunomodulators discussed in this review succinctly demonstrate the potential of these agents to stimulate host defense mechanisms for prophylaxis and treatment of various microbial infections.

Zidovudine. An update of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy

Zidovudine remains the mainstay in the treatment of patients infected with human immunodeficiency virus (HIV). The drug delays disease progression to acquired immunodeficiency syndrome (AIDS) and to AIDS-related complex (ARC), reduces opportunistic infections, and increases survival in patients with advanced HIV infection. There is evidence to suggest that zidovudine also delays disease progression in patients with mild symptomatic disease. Although one study has shown zidovudine to have no significant beneficial effects on survival or disease progression in patients with asymptomatic HIV infection, several other studies have shown zidovudine to delay disease progression in this patient group. Results from related ongoing studies are awaited with interest. Zidovudine reduces the incidence of AIDS dementia complex (ADC) and appears to prolong survival in these patients, and improves other neurological complications of HIV infection. The drug also appears to enhance the efficacy of interferon-alpha in patients with Kaposi's sarcoma. Although zidovudine is widely used as postexposure prophylaxis following accidental exposure to HIV, its efficacy in preventing seroconversion is unclear. Whether zidovudine prevents vertical transmission also remains to be determined. The overall efficacy of zidovudine in the treatment of children with HIV infection appears similar to that in adults despite more rapid disease progression in younger patients. Zidovudine-resistant isolates can emerge as early as after 2 months' therapy, and primary infection with zidovudine-resistant strains has been documented. Both zidovudine resistance and the syncytium-inducing HIV phenotype appear to be associated with poor clinical outcome. However, zidovudine resistance may revert on drug withdrawal or switching to an alternative therapy. Zidovudine-associated haematotoxicity may be dose-limiting. Nonhaematological adverse events associated with zidovudine therapy are generally mild and usually resolve spontaneously. Dosages of approximately 500 to 600 mg/day appear to be at least as effective as dosages of 1200 to 1500 mg/day and are better tolerated in patients with less advanced disease. However, optimal dosage are unclear. Despite beneficial effects, zidovudine monotherapy is not curative. There is evidence to suggest that the concomitant administration of zidovudine with didanosine or zalcitabine is effective in patients with HIV disease progression despite receiving zidovudine monotherapy, and there is some evidence that concomitant zidovudine plus didanosine therapy is more effective than alternating monotherapy. However, results from studies of combination therapy in asymptomatic patients, and from comparative combination therapy studies are awaited. Cotherapy with agents that augment haematopoiesis allows the continuation of therapeutic zidovudine dosages.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunostimulants

Nonspecific immunostimulation has progressed from crude microbially derived substances to chemically defined drugs with selective effects on different components of the immune system. John Hadden describes how immunopharmacological analyses of structure-activity relationships, pharmacokinetics and immunopharmacodynamics have directed the effective use of these agents in disease models and suggest that they may be of value in combination with other therapies in the treatment of immunodeficiencies, cancer, infections and even autoimmune disorders.

Immunostimulants

Nonspecific immunostimulation has progressed from crude microbially derived substances to chemically defined drugs with selective effects on different components of the immune system. John Hadden describes how immunopharmacological analyses of structure-activity relationships, pharmacokinetics and immunopharmacodynamics have directed the effective use of these agents in disease models and suggest that they may be of value in combination with other therapies in the treatment of immunodeficiencies, cancer, infections and even autoimmune disorders.