Isoprinosine as an immunopotentiator

A Review on Inosine Pranobex Immunotherapy for Cervical HPV-Positive Patients

The purpose of this review was to examine and summarize data for inosine pranobex (IP) immunotherapy in cervical HPV-positive patients. Persistent or recurring cervical human papillomavirus (HPV) infection is a major cause of cervical cancer. Self-clearance and blocking of cervical HPV infection depend on the status of the host immune system. Immunotherapy helps accelerate elimination of the infection. Host immunity is involved in the development of HPV infection. Several mechanisms of interaction between the virus and the immune system have been revealed; however, the mechanisms have not been completely elucidated. A properly functioning immune system impedes HPV progress and helps clear the pathogen from the body. IP has antiviral efficacy because it modulates both cellular and humoral immunities. IP has been on the market since 1971. Nevertheless, it has seldom been administered to treat cervical HPV infections. In this review, Google Scholar, PubMed/MEDLINE, Scopus, Cochrane Library, and Research Gate were searched for the period 1971–2021. Prospective controlled trials, observational and retrospective studies, and meta-analysis and reviews on immunotherapy against HPV cervical infection were explored. Prior studies showed strong clinical efficacy of combined and standalone IP therapy in reversing HPV-induced changes in the cervix, preventing disease progression, and clearing the pathogen. IP treatment enhanced host antiviral activity against HPV, delayed or stopped cervical oncogenesis, and rapidly removed HPV from the body.

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.

Inosine Acedoben Dimepranol promotes an early and sustained increase in the natural killer cell component of circulating lymphocytes: A clinical trial supporting anti-viral indications

Inosine Acedoben Dimepranol (IAD), licensed for the treatment of cell-mediated immune deficiencies associated with viral infections, has been reported to impact a variety of immune parameters both in vitro and in vivo. Here we report the results from a clinical trial where multiple lymphocyte subsets - CD19+ B cells, CD3+ T cells, CD4+ T-helper cells, FoxP3^hi/CD25^hi/CD127^lo regulatory T cells (Tregs), CD3-/CD56+ NK cells, and CD3+/CD56+ NKT cells - were, together with serum immunoglobulins and IgG subclasses, followed during 14days of IAD administration to ten healthy volunteers; these selected from 27 individuals pre-screened in vitro for their capacity to respond to IAD as gauged by increases in the percentage of Treg and/or NKT cells arising in PHA-stimulated cultures. While a transient spike and dip in Treg and T-helper fractions, respectively, was noted, the outstanding consequence of IAD administration (1g po, qds) was an early and durable rise in NK cells. For half the cohort, NK cells increased as a percentage of total peripheral blood lymphocytes within 1.5h of receiving drug. By Day 5, all but one of the volunteers displayed higher NK cell percentages, such elevation - effectively a doubling or greater - being maintained at termination of study. The IAD-induced populations were as replete in Granzyme A and Perforin as basal NK cells. The novel finding of IAD boosting phenotypically competent NK numbers in healthy individuals supports the drug's indicated benefit in conditions associated with viral infection and reinforces the potential for uplift where immune performance may be compromised.

Inosine pranobex in the treatment of HIV infection: a review

Inosine pranobex (InPx) could prove a valuable and innovative approach to the treatment of HIV-infected patients, since InPx administration has been shown in two multicenter trials to effectively delay the progression of HIV infection to overt AIDS. However, further studies are strongly required to optimize both the dosage of inosine pranobex and the administration schedules. Furthermore, clinical trials evaluating combination therapy of HIV infection with both InPx and zidovudine should ultimately provide an important advance in the management of HIV-infected patients. Our finding that concomitantly administered InPx to zidovudine-receiving patients increased the plasma levels of zidovudine as well as prolonged zidovudine mean half-life during InPx treatment suggests several potential advantages of the combination treatment with both InPx and zidovudine, such as a need for lower zidovudine dosage and a longer interval period between administering zidovudine to obtain sustained plasma levels as well as a potential to enhance residue immune function resulting from inosine pranobex treatment.

The cortex regulates the immune system and the activities of a T-cell specific immunopotentiator

Evidence has accumulated to demonstrate important bidirectional communications between the nervous and immune systems. The anatomic pathways of communication include the commitment of different midbrain areas to regulation of immunologic functions. Neuropeptides appear as critical mediators of neuroregulation of function of diverse immunocompetent cells. Biochemicals secreted by immunocompetent cells mediate the effects of the immune system on the nervous system. We provide suggestive evidence that the above summarized effects are under a lateralized control of the neocortex. Furthermore, the neocortex has a lateralized influence on the immunopotentiating effects of sodium diethyl dithiocarbamate (imuthiol), which compound selectively increases T-cell numbers and activities, and acts on cholaminergic pathways. Thus, a major hemispheric asymmetry in the response to a drug is revealed. These results point to an important influence of neocortex on number and function of immunocompetent cells, which role can be modified by pharmacologic agents.

Low molecular weight immunopotentiators

It has long been recognized that modulation of the immune system by various agents may have potential for the management of certain infectious and neoplastic diseases. Both natural products as well as chemically synthesized compounds have been investigated for immunotherapeutic potential. Over the years, conflicting reports on the clinical efficacy of these agents have left the early promise of immunotherapy unfulfilled. However, the manipulation of the immune system to generate a desired effect is becoming feasible as the mechanisms which regulate the immune network are better understood. Much of the early work on immunotherapy concentrated on the development of immunopotentiators, agents which enhance the host's own immune system against cancer cells or infectious pathogens. Furthermore, with the development of subunit and/or synthetic vaccines, which are often weakly immunogenic, the importance of developing agents capable of acting as adjuvants became apparent. As a result, the utility of immunopotentiators has now extended to the area of vaccines. There are a number of reviews available on immunomodulators [see Fenichel, R. L. and Chirigos, M. A. (eds) (1984), Immune Modulation Agents and Their Mechanisms, Marcel Dekker, New York]. The purpose of this article is to provide an update on low molecular weight agents capable of potentiating the immunological network. Attention will be given to those agents which have undergone significant clinical development in the areas of cancer, infectious diseases and vaccination over the past several years. These agents will be categorized as to whether they are naturally occurring or chemically synthesized.

Study of the inhibition of histamine release by inosine pranobex

The effects of Inosine pranobex and its parent compounds inosine and dimethylamino-2-propanol-p-acetamidobenzoic acid (DipPacBa) on the Concanavalin A (ConA)-induced histamine release from human adenoidal mast cells were investigated. Inosine pranobex inhibited the ConA-induced histamine release at concentrations greater than 10(-3) M. Inosine itself (10(-5)-10(-2) M) enhanced the ConA-induced histamine release whereas DipPacBa inhibited the release significantly at concentrations between 10(-6) and 10(-2) M. These results are consistent with the assumption that the effect of Inosine pranobex is due to the DipPacBa moiety.

Isoprinosine restores in vitro T lymphocyte functions of cyclophosphamide immunosuppressed mice

The effect and the mechanism of action of isoprinosine has been investigated in several models of in vitro activation of lymphocytes. Isoprinosine added to spleen cell cultures enhanced lymphocyte proliferation induced by concanavalin A or allogeneic stimulation as well as the generation of allospecific cytotoxic T cells. The effect of isoprinosine on T lymphocyte proliferation in vitro was specially marked when mice were treated with cyclophosphamide (75-200 mg/kg) 16-24 h before the onset of cultures. No effect was observed on B cell proliferation to LPS. Addition of inosine or adenosine also enhanced proliferation of cells from both normal and cyclophosphamide treated mice. Isoprinosine and inosine and, more markedly, adenosine, augmented interleukin-2 activity in concanavalin A supernatants of spleen cells from the same animals.

Inosine pranobex. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy

Inosine pranobex is a synthetic compound formed from the p-acetamido benzoate salt of N-N dimethylamino-2-propanol and inosine in a 3:1 molar ratio. It has been reported to exert antiviral and antitumour activities in vivo which are secondary to an immunomodulating effect, and early results suggest beneficial clinical effects in several diseases and infections including mucocutaneous Herpes simplex infections, subacute sclerosing panencephalitis, genital warts, influenza, zoster, and type B viral hepatitis, as well as in homosexual men with persistent generalised lymphadenopathy. However, many of the studies have been preliminary in nature and deficient in design or in the reporting of their results. One must therefore conclude that while inosine pranobex may prove to be a valuable and innovative therapy for a number of diseases and infections for which no satisfactory therapy exist, further long term well controlled studies in larger numbers of patients are required before definitive conclusions about the efficacy of inosine pranobex in these disorders will be possible.

In vivo effect of isoprinosine on interleukin-2 production, lymphocyte mitogenesis and NK activity in normal and cyclophosphamide immunosuppressed mice

The in vivo effect of isoprinosine on IL-2 production, mitogen-induced proliferation and NK activity of lymphocytes from normal as well as cyclophosphamide (CY) treated mice has been investigated. Isoprinosine was given in a single dose (50 mg/kg or 5 mg/kg) to normal or CY treated mice (250 mg/kg i.p. simultaneously to isoprinosine). An enhancement of T lymphocyte proliferation and IL-2 production was observed in both cases. There was no correlation between the small effect observed in T lymphocyte proliferation and the enhancement of IL-2 levels found in the supernatants of Con A activated spleen cells, specially in normal mice. Administration of isoprinosine every day (50 mg/kg) augmented Con A induced mitogenesis, IL-2 production and NK activity in animals treated with cyclophosphamide, but not in normal mice. Isoprinosine could be of interest in a combined treatment with immunosuppressants for the restoration of certain immune functions. The effect of isoprinosine on immune responses may be mediated in part by changes in IL-2 activity.

Effects of isoprinosine in animal models of depressed T-cell function

Isoprinosine--a new drug possessing immunostimulating properties--was investigated for its ability to influence cell-mediated immune responsiveness in animal models of deficient T-cell function. In vitro isoprinosine strongly increased T-cell mitogenesis in spleen cells from normal rats, with only modest increases in B-cell mitogenesis and no effects on unstimulated cells. In vivo isoprinosine (50 mg kg-1 day-1 orally) had no effects on spleen cell responsiveness when administered to normal rats for 4 or 14 days. However, when the same dose of isoprinosine was administered to rats immunosuppressed with cyclophosphamide (5 mg kg-1 day-1 orally) a partial restoration of T-cell mitogenesis was observed after 14 days of treatment. In rats with adjuvant arthritis treated with isoprinosine for 14 days, depressed T-cell responsiveness was completely restored to the level of the nonarthritic animals. The involvement of different cell types in the observed effects of isoprinosine was further studied in arthritic rats. Removal of monocytes/macrophages from the cell suspensions prior to culture did not affect the increased T-cell response in isoprinosine-treated rats, suggesting a direct stimulatory effect of isoprinosine on T-cell functions. T-suppressor cell function, impaired in arthritic rats, was not restored by treatment with isoprinosine. These results suggest that isoprinosine may exert selective effects on specific T-cell subsets, a finding that may increase the therapeutic interest of the drug.

Modulation of T- and B-lymphocyte functions by isoprinosine in homosexual subjects with prodromata and in patients with acquired immune deficiency syndrome (AIDS)

Male prodromal homosexuals and patients with acquired immune deficiency syndrome (AIDS) exhibited similar immunological abnormalities but by different degrees. A reduction in the number of circulating T lymphocytes bearing the T-4 surface marker led to an altered ratio of Th to Ts subpopulations in both groups of subjects. Total numbers of suppressor cells (Ts) remained virtually similar in both study groups to that of the control subjects. Proliferative responses to T-cell mitogen (PHA) and T cell-dependent B-cell mitogen (PWM) were severely impaired in prodromal subjects and more so in the AIDS group. The response to PWM was unrelated to the total number of suppressor T cells but was associated with a significant decrease in helper T-cell number. The impaired lymphocyte functions of immunosuppressed subjects were potentiated by coincubation with isoprinosine in a selective fashion. While the percentage of upward modulation among homosexuals with normal lymphocyte functions was comparable to that obtained in control subjects, a higher degree of augmentation was achieved in AIDS patients and in prodromal subjects with impaired blastogenic responses. In none of the AIDS patients with severe immunodeficiencies, however, was the lymphocyte functions restored to the normal range established in the heterosexual controls. These results suggest the feasibility of eventual prophylactic utilization of isoprinosine in male homosexuals at high risk of developing AIDS.

Medical registers as historical controls: analysis of an open clinical trial of inosiplex in subacute sclerosing panencephalitis

Clinical trials of treatments for rare or fatal diseases must often use historical rather than randomized concurrent controls. Randomized trials may not be possible if (1) the number of patients available is quite small, (2) ethical considerations discourage the assignment of patients to control treatments known to be ineffective or (3) some evidence suggests that the proposed new treatment is substantially more effective than the control. We suggest that, when randomization is not feasible, adequately maintained medical registers can serve as a source of control patients. Investigators must pay careful attention to prognostic factors that might bias the results. However, statistical techniques for controlling such bias exist and, if these are properly employed, registry-derived historical controls can be used to evaluate the effectiveness of treatment.

Enhancement of the immune response to sheep erythrocytes in mice by phosphodiesterase-inhibiting dipyridamole derivatives

Some potent phosphodiesterase (PDE)-inhibiting dipyridamole derivatives are able to increase the primary immune response in mice immunized with sheep red blood cells (SRBC). 10mg/kg/day of the most potent substance administered in the drinking water increased the number of plaque forming cells (PFC) in spleens of these mice by a factor of about 2 when the treatment was started after immunization. Pretreating the animals did not result in an enhancement of numbers of plaque forming cells. There was no increase in the background number of PFC.

Modulation of human T lymphocyte functions by isoprinosine

Isoprinosine was shown to alter certain T cell functions. In vitro, it has previously been shown to induce suppressor cell activity in both mouse and human lymphocytes. Our in vitro results suggest that Isoprinosine acts on immune balance by increasing the number of non-suppressor T cells and, at least partially blocks Con A induced suppressor activity. In vitro NK activity remained unaltered.

Modulatory effect of isoprinosine on lymphocyte proliferative response under immunodepressive conditions

In the present work the effect of Isoprinosine on the mitogenic responses of T and B lymphocytes has been studied. We have found that Isoprinosine can enhance in vitro the response to Concanavalin A. This enhancement was more apparent in cell cultures showing an initially low blastogenic response. In low responses artificially induced by treatments in vivo with cyclophosphamide, our results indicate that Isoprinosine, administered in vivo, does not enhance the response to Con A of treated mice. However, addition of Isoprinosine (75 micrograms/ml) to cultures of spleen cells from mice previously treated with cyclophosphamide enhanced the suppressed response up to normal levels. Neither in vivo nor in vitro Isoprinosine treatments increased the response of lymphocytes to lipopolysaccharide, but usually inhibited the blastogenesis of B cells.

Inosiplex therapy in subacute sclerosing panencephalitis. A multicentre, non-randomised study in 98 patients

Inosiplex was administered to 98 patients with subacute sclerosing panencephalitis (SSPE) in the United States and Canada for variable periods of time up to 9.5 years. Survival data from these 98 patients were compared by life-table analysis with survival in three SSPE control groups drawn from SSPE patients contracting the disease in Israel, Lebanon, or the United States at about the same time as the inosiplex-treated patients but treated differently or not at all. In the inosiplex-treated patients the actuarial probability of survival at 2, 4, 6, and 8 years from onset of SSPE was 78%, 69%, 65%, and 61%, compared with 38%, 20%, 14%, and 8% in a composite control group (p less than 0.01 for all four comparisons). Statistical adjustments for time-to-treatment bias did not affect this result: a modified logrank procedure demonstrated that the risk of dying in the treatment group was 43% of that in the controls. Inosiplex seems to be able to prolong life in patients with SSPE.

Long-term follow-up of patients with subacute sclerosing panencephalitis treated with inosiplex

During the past five years, 15 patients with subacute sclerosing panencephalitis (SSPE) were treated with inosiplex. Using a disability index specifically designed for the disease, this study monitored the course of SSPE in each patient before and during inosiplex therapy. Posttreatment follow-up ranged from 2 to 144 months. Inosiplex had an apparently beneficial effect on morbidity and mortality in 10 of the 15 patients tested. Eight improved immediately after treatment, 2 had a delayed improvement, and 1 patient stabilized. Four patients followed a typical course for SSPE and died a mean 9 months after onset. Treatment was not associated with adverse reactions. Due to its low risk-benefit ratio, inosiplex is recommended for continuous use in SSPE even after extended remissions.

Effect of levamisole and methisoprinol on in vitro lymphocyte reactivity in chronically irradiated subjects and patients affected by neoplasias

The data of this experiment show that Levamisole moderately stimulates T-lymphocyte proliferation and efficiency in vitro and methisoprinol markedly does so when both drugs act in combination with PHA in subjects with severely impaired cell-mediated responsiveness, whereas they do not exert any effect on lymphocytes in normal subjects. B-lymphocyte in vitro responsiveness does not appear to be affected by the immunomodulators, except for some cases of cancer of the stomach wherein B-lymphocyte responsiveness is stimulated in vitro by Levamisole and more evidently by Methisoprinol. These data support the use of Methisoprinol or Levamisole in therapy, and further investigations regarding the mechanisms whereby they might act and the dose-effect relationship which might show to be important for the type of desired immunomodulation would appear appropriate.