It modulates the immune system by immunostimulation or immunooptimisation of defensive inflammation[2] at the cellular level, e.g. by interfering with energy metabolism, cell signalling and proliferation.
[3] Its administration has been shown both in vivo and in vitro to induce Th1 cell-type response, as evidenced by the increase in pro-inflammatory cytokines (e.g. IL-2, ILN-γ) in mitogen- or antigen-activated cells.
[9] It has also been proven that other cells of the innate immunity are affected,[10] as neutrophil, monocyte and macrophage chemotaxis and phagocytosis were enhanced in cancer patients.
[2] Several hypotheses have been formed over time, but all of them agree that the drug has direct effect on viral RNA synthesis via inhibiting transcription and translation of the genetic code at cellular level.
[13][14] It has been suggested that the drug itself, or any one of its components, directly acts on the ribosomes of infected cells providing an advantage to cellular RNA in competition for synthesis.
Inosine is proven to act on ribosome directly,[16] as such one theory suggests that it inhibits the synthesis of phosphoribosyl pyrophosphate from ribose phosphate, the former being an intermediate in the biosynthesis of purine nucleotides such as adenylate and guanylate.
[3] Macroscopically, antiviral activity has been documented in vivo on several animal models, and experimentally tested on the cytomegalovirus and Influenza disease strains.
Several studies have investigated the benefits of inosine pranobex therapy in frequently ill children[21][22] and returned positive results in both clinical and immunological outcomes.
[27] Several long-term studies have shown efficacy even compared to surgical method at treating oral HPV-positive proliferative verrucous leucoplakia (PVL).
[20] In Influenza and Influenza-like (RSV, adenovirus and parainfluenza virus) infections, inosine pranobex did lower the symptom severity and duration.
[30][3] When the global coronavirus pandemic hit in 2020, inosine pranobex was one of the first medication used experimentally to treat the SARS-CoV-2 induced virosis, mainly due to its remarkably wide area of use and general antiviral properties.
[31][32] In 2022, a large Phase 3 trial concluded that administration of inosine pranobex should start as early as possible with greatly improved outcomes in mild to moderate COVID-19 patients.
[33] In type B hepatitis, inosine pranobex was found ineffective during the acute phase of the infection, though in 28 days lower bilirubin and transaminase levels were detected.
It has been shown that inosine pranobex therapy in combination with ribavirin normalizes alanine aminotransferase levels in patients unresponsive to interferon treatment.
[37] In 2003, the possibility of using inosine pranobex for treating myalgic encephalomyelitis/chronic fatigue syndrome was investigated experimentally and returned promising results,[38] when 6 out of 10 subjects reported noticeable improvement.
[43] Due to the potential risk of hyperuricosuria and the development of urate nephrolithiasis, increased fluid intake and exclusion of acidic foods is recommended during isoprinosine therapy.
[44] Neither long-term damage not death from overdose have been reported in relation to inosine pranobex, doses upward of 1 g/kg of body weight were found to be toxic in rodents.