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Pidotimod

Tier 2 · Preclinical
Also known as PGT/1A · Onicap · Polimod

The strongest evidence present is Tier 1: reviews aggregating human randomized controlled trials reported reduced reinfection rates (OR 0.20), lesser need for antibiotics, and decreased absenteeism versus placebo (src-2, src-27), and pharmacokinetic work included human RCT-graded studies (src-13). However, much of the broader efficacy base across chronic respiratory disease, HIV, COVID-19, bronchiectasis and elderly pneumonia is observational or expert-opinion, and one review (src-21) explicitly states RCTs are still needed to establish real efficacy in preventing acute respiratory tract infections in paediatric age. An animal infection model (src-29) failed to reproduce protective effects. Mechanistic detail draws on in vitro, animal, and human observational sources.

Half-life
~4 h
Routes
Oral
Goals
Immune support · Respiratory infection prevention · Recurrent infection reduction
Cost / mg
Not recorded

How it works

Reviews describe pidotimod as a synthetic dipeptide that acts as an immune-system modulator, working on both innate and adaptive immunity. According to these reviews and human observational sources, it stimulates dendritic cells, boosts toll-like receptor (TLR) expression, and promotes production of signaling molecules such as IL-2 and IFN-gamma, thereby supporting both cell-based and antibody-based immune defenses. In vitro studies report it pushes T lymphocytes toward a Th1 phenotype, raises natural killer cell activity, and increases antibody levels including salivary IgA.

Overview

Overview

Pidotimod (also known as PGT/1A, Onicap, and Polimod; CAS 121808-62-6) is described in reviews as a synthetic dipeptide molecule — 3-L-pyroglutamyl-L-thiazolidine-4-carboxylic acid — with immunomodulatory properties acting on both innate and adaptive immunity (src-1, src-6, src-9, src-20, src-24, src-13). A product listing cites it at 98% purity (src-9).

Reviews describe pidotimod as an immunomodulatory agent that has been in use for over three decades (since the early 1990s) to prevent recurrent respiratory infections, particularly in immunocompromised populations such as children and the elderly (src-4, src-6, src-8, src-10, src-16, src-1, src-20). One review noted that more than a hundred papers have been published about it since the early 1990s (src-7). Reviews state it is indicated for adults and children over 3 years of age with documented cell-mediated immunodepression during respiratory and urinary tract infections (src-1, src-20).

Reported Clinical Findings

A review reported that, compared with placebo, pidotimod significantly reduced reinfection rates (OR 0.20, 95% CI 0.12 to 0.33; p < 0.00001), showed a lesser need for antibiotics (mean difference −2.65, 95% CI −3.68 to −1.62; p < 0.00001), and decreased absenteeism (mean difference −2.99, 95% CI −4.03 to −1.95; p < 0.00001) (src-2, src-27). The same review reported it reduced the number and severity of symptoms associated with respiratory tract infections and decreased disease burden while improving quality of life compared to placebo (src-2).

A review of 32 studies (24 in children, 8 in adults) reported that adding pidotimod to standard of care significantly prevents recurrences and reduces severity and duration of acute episodes in children with recurrent respiratory infections, and reduces pediatric clinic visits and school absenteeism (src-3, src-11, src-17). In adults, the same review reported effectiveness in prevention and treatment of acute infectious exacerbations of chronic bronchitis and COPD, with evaluation also in pneumonia, hand-foot-mouth disease, bronchiectasis, and chronic idiopathic urticaria (src-3, src-11, src-17). A clinical summary reported reduced severity of infectious episodes, rapid recovery, reduced need for antibiotics and symptomatic treatments, decreased school absenteeism and clinic visits, improved lung function and airway epithelial clearance, and reduced acute exacerbations of chronic bronchitis/COPD with improved T-cell function (src-9). Clinical studies reported reduced rates of recurrent upper respiratory and urinary tract infections in children and adults, with effects more evident in immune defects such as senescence, Down's syndrome, and cancer (src-9, src-15).

Reviews report improvement of FEV1 and PEF in asthmatic patients (src-6, src-24), clinical and cellular changes in patients with allergic rhinitis and asthma (src-1, src-20, src-5, src-23, src-18), effects on metabolomic profiles in bronchiectasis, and improved clinical and immunological outcomes in elderly patients with pneumonia (src-1, src-20). A study of 40 HIV-positive individuals (30 supplemented, 10 controls) reported IL-10, IFN-gamma, and IL-4 significantly higher in the pidotimod group with persistence after suspension, reduced pro-inflammatory cytokines, increased salivary IgA during and after supplementation, and decreased Cystatin C and microalbuminuria (src-26); reviews report beneficial effects on cytokines and humoral immunity in HIV patients (src-1, src-20, src-31). The Reappraisal of Pidotimod review (src-1, src-20), the 'From Legacy to Innovation' review (src-4, src-16), and an Italian multidisciplinary Delphi consensus (src-22) report that pidotimod may shorten the duration of COVID-19 (SARS-CoV-2) infection and reduce clinical severity by modulating the immune response. An Italian multidisciplinary Delphi consensus (src-22) states pidotimod can be used in combined therapy with antibiotics for pneumonia and describes it as useful in Down syndrome, COVID-19, PFAPA, wheezing, and urinary infections.

Animal and In Vitro Findings

An animal study reported that pidotimod significantly reduced clinical scores in experimental autoimmune encephalomyelitis (EAE) mice versus vehicle, decreased leukocyte infiltration in spinal cord and brain, and suppressed demyelination, with increases in regulatory T cells and decreases in Th1/Th17/Tc17 cells suggesting neuroprotective effects via regulating splenic lymphocyte balance (src-19, src-34). A zebrafish study reported increased recruitment of neutrophils and macrophages to the wound site and promotion of il1b transcription, while noting the exact mechanism of protection remains ill-defined (src-29).

Context and Limitations

A review cited 2.74 million deaths from lower respiratory infections globally in 2015 and 103 million disability-adjusted life years as context for pidotimod use (src-11), and another reported that immunostimulants reduce the incidence of acute respiratory tract infections by 40% in susceptible children (src-7). Much of the efficacy evidence, however, is observational or expert opinion rather than controlled trials; one review (src-21) explicitly states that further preclinical research and randomised controlled trials will be necessary to clarify its mechanisms and establish its real efficacy in preventing acute respiratory tract infections in paediatric age. Notably, a zebrafish study found no protection of uropathogenic Escherichia coli or Mycobacterium marinum infected larvae following pidotimod treatment (src-29). Separately, one source (src-28) concerns a finasteride conjugate with 'N-polimod' — a distinct chemical entity whose 5α-reductase inhibition and effect on prostate hyperplasia in rats do not describe pidotimod's own activity.

What the research shows

222 findings extracted from the 29 sources cited below, strongest evidence first within each group. Every one links to the source it came from.

What human studies found

Based on 10 human trial findings, 57 human study findings, 5 animal findings, 1 in vitro finding and 10 expert opinion findings.

  • human trialComparison with placebo demonstrated significant advantages for pidotimod in terms of reduced reinfection rates5

  • human trialPidotimod showed a lesser need for antibiotics compared to placebo5

  • human trialPidotimod decreased absenteeism compared to placebo5

  • human trialPidotimod reduced the number and severity of symptoms associated with RTIs5

  • human trialPidotimod decreased disease burden and improved quality of life5

  • human trialPidotimod demonstrated significant advantages compared to placebo in terms of reduced reinfection rates12

  • human trialPidotimod showed a lesser need for antibiotics compared to placebo12

  • human trialPidotimod decreased absenteeism compared to placebo12

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  • human trialClinical studies demonstrate efficacy of pidotimod in reducing the rate of recurrent infections of the upper respiratory and urinary tracts in children16

  • human trialSame results were obtained in recurrent respiratory tract infections in adults16

  • human studyRecent studies have expanded its potential beyond traditional indications, with evidence supporting its role in patients with chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD), allergic rhinitis, and even viral infections, including SARS-CoV-21

  • human studyRecent studies have expanded its potential beyond traditional indications, with evidence supporting its role in patients with chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD), allergic rhinitis, and even viral infections, including SARS-CoV-2.2

  • human studyPidotimod effectively and safely prevents respiratory infections, mainly in children with recurrent and frequent infectious episodes4

  • human studyPidotimod, thanks to its immunomodulatory activity and preventing respiratory infections, may be beneficial in managing subjects with asthma and allergic diseases4

  • human studyPidotimod's immunostimulant activity has been firmly established in the management of recurrent respiratory infections in children with or without asthma6

  • human studyCompared to standard of care alone, addition of pidotimod to standard of care significantly prevents recurrences and reduces the severity and duration of acute episodes6

  • human studyAddition of pidotimod results in reduced visits to pediatric clinics and lower absenteeism at school6

  • human studyIn adults, pidotimod is effective in the prevention and treatment of acute infectious exacerbations of chronic bronchitis and chronic obstructive pulmonary disease (COPD)6

  • human studyPidotimod has firmly established immunostimulant activity in the management of recurrent respiratory infections in children with or without asthma7

  • human studyAddition of pidotimod to standard of care significantly prevents recurrences and reduces severity and duration of acute episodes in children with recurrent respiratory infections7

  • human studyPidotimod results in reduced visits to pediatric clinics and lower absenteeism at school7

  • human studyIn adults, pidotimod is effective in prevention and treatment of acute infectious exacerbations of chronic bronchitis and COPD7

  • human studyPidotimod demonstrates efficacy and safety in different clinical settings8

  • human studyPidotimod is effective in managing children and adults with recurrent respiratory infections in prevention and add-on therapy8

  • human studyPidotimod is safe and effective for preventing recurrent respiratory infections in susceptible patients8

  • human studyPidotimod is effective as an adjuvant in managing patients with infections8

  • human studyPidotimod has evidence supporting its role in patients with chronic obstructive pulmonary disease (COPD)9

  • human studyPidotimod has evidence supporting its role in allergic rhinitis9

  • human studyPidotimod has evidence supporting its role in viral infections, including SARS-CoV-29

  • human studyExtensive evidence about Pidotimod, accumulated over the last 30 years, has provided much data on the prevention of recurrent respiratory infections in susceptible children10

  • human studyExtensive evidence about Pidotimod shows prevention of respiratory exacerbations in patients with chronic bronchitis10

  • human studyPidotimod affects the metabolomic profiles of patients with bronchiectasis10

  • human studyPidotimod improves clinical and immunological outcomes of elderly patients with pneumonia10

  • human studyPidotimod produces clinical and cellular changes in patients with allergic rhinitis and asthma10

  • human studyPidotimod has beneficial effects on cytokines and humoral immunity in HIV patients10

  • human studyPidotimod can shorten the duration of COVID-19 infection and reduce clinical severity by modulating the immune response10

  • human studyIL-10, IFN gamma, and IL-4 were significantly higher at enrolment in HIV positive participants treated with Pidotimod compared to the control group11

  • human studyThe increase in IL-10, IFN gamma, and IL-4 under Pidotimod treatment persisted after supplementation suspension11

  • human studyPro-inflammatory cytokines levels were reduced in HIV positive participants treated with Pidotimod11

  • human studySalivary IgA increased during 4 weeks of Pidotimod supplementation and persisted at 4 weeks after completing supplementation11

  • human studyCystatin C and microalbuminuria levels decreased over time in Pidotimod-treated HIV positive participants, with Cystatin C serum levels decreasing to a greater extent11

  • human studyPidotimod achieved a rebalancing of pro-inflammatory and anti-inflammatory cytokines in HIV population11

  • human studyPidotimod resulted in a significant reduction in cystatin C levels in HIV population11

  • human studyPidotimod has immunostimulant activity firmly established in the management of recurrent respiratory infections in children with or without asthma13

  • human studyAddition of pidotimod to standard of care significantly prevents recurrences and reduces severity and duration of acute episodes compared to standard of care alone13

  • human studyPidotimod results in reduced visits to pediatric clinics and lower absenteeism at school in children with recurrent respiratory infections13

  • human studyIn adults, pidotimod is effective in prevention and treatment of acute infectious exacerbations of chronic bronchitis and COPD13

  • human studyImprovement of FEV1 and PEF in asthmatic patients treated with Pidotimod has been demonstrated14

  • human studyMain clinical outcomes are the reduction of the number of infectious episodes, lesser severity of signs and symptoms and consequently a reduction in use of antibiotics and symptomatic drugs14

  • human studyPidotimod shows less working and school days lost, less mortality and morbidity14

  • human studyImprovement of FEV1 and PEF in asthmatic patients treated with Pidotimod15

  • human studyReduction of the number of infectious episodes in treated patients15

  • human studyLesser severity of signs and symptoms with reduction in use of antibiotics and symptomatic drugs15

  • human studyLess working and school days lost with Pidotimod treatment15

  • human studyReduction in mortality and morbidity with Pidotimod15

  • human studyClinical studies demonstrating the efficacy of pidotimod in reducing the rate of recurrent infections of the upper respiratory and urinary tract in children18

  • human studySame results obtained in recurrent respiratory tract infections in adults18

  • human studyEffects more evident in the setting of immune defects such as senescence, Down's syndrome, and cancer18

  • human studyPidotimod reduces the severity of infectious episodes, improves clinical features, results in rapid recovery, reduces the need for antibiotic and other symptomatic treatments18

  • human studyDecreases school absenteeism and visits to pediatric clinics18

  • human studyImproves lung function and airway epithelial clearance, suggesting its potential to lower the rates of asthma in children18

  • human studyEfficacy in reducing acute exacerbations of CB or COPD with improvement in T-cell function18

  • human studyPidotimod effectively and safely prevents respiratory infections, mainly in children with recurrent and frequent infectious episodes21

  • human studyPidotimod, thanks to its immunomodulatory activity and preventing respiratory infections, may be beneficial in managing subjects with asthma and allergic diseases21

  • human studyPidotimod showed its usefulness in reducing need for antibiotics in airway infections24

  • human studyImmunostimulants reduce the incidence of acute respiratory tract infections (ARTIs) by 40% in susceptible children24

  • human studyPidotimod showed usefulness in reducing need for antibiotics in airway infections25

  • animalIn vivo studies have confirmed in vitro findings on innate and adaptive immune responses16

  • animalPidotimod treatment significantly reduced clinical scores in EAE mice compared to vehicle control20

  • animalNo protection of uropathogenic Escherichia coli infected zebrafish larvae following PDT treatment22

  • animalNo protection of Mycobacterium marinum infected zebrafish larvae following PDT treatment22

  • animalProstate hyperplasia of rats was reduced by Finasteride conjugate treatment similar to the Finasteride treatment26

  • in vitroIn vitro studies, both from animal and human specimens, have documented a good activity on innate and adaptive immune responses16

  • expert opinionpidotimod enhances the immune system properties often impaired in patients with allergic disorders23

  • expert opinionExtensive evidence about Pidotimod, accumulated over the last 30 years, has provided much data on the prevention of recurrent respiratory infections in susceptible children27

  • expert opinionPidotimod has evidence for prevention of respiratory exacerbations in patients with chronic bronchitis27

  • expert opinionPidotimod affects the metabolomic profiles of patients with bronchiectasis27

  • expert opinionPidotimod affects clinical and immunological outcomes of elderly patients with pneumonia27

  • expert opinionPidotimod produces clinical and cellular changes in patients with allergic rhinitis and asthma27

  • expert opinionPidotimod has beneficial effects on cytokines and humoral immunity in HIV patients27

  • expert opinionPidotimod can shorten the duration of COVID-19 infection and reduce clinical severity by modulating the immune response27

  • expert opinionPidotimod can prevent vaccination-related adverse events27

  • expert opinionRandomised control trials will be necessary to establish the real efficacy of Pidotimod in the prevention of ARTIs in paediatric age28

How it works

Based on 2 human trial findings, 17 human study findings, 12 animal findings, 24 in vitro findings, 30 expert opinion findings and 2 theoretical findings.

  • human trialPidotimod is a biological response modifier3

  • human trialPidotimod's activity was shown to be mediated via multiple pathways of the immune system12

  • human studyPidotimod exerts its effects by stimulating dendritic cells, enhancing toll-like receptor (TLR) expression, and promoting cytokine production, including IL-2 and IFN-γ, thereby supporting both cellular and humoral immunity1

  • human studyPidotimod exerts its effects by stimulating dendritic cells, enhancing toll-like receptor (TLR) expression, and promoting cytokine production, including IL-2 and IFN-γ, thereby supporting both cellular and humoral immunity.2

  • human studyPidotimod is a synthetic dipeptide that exerts immunomodulatory activity, modifying innate and adaptive immunity4

  • human studyPidotimod firstly acts on Toll-like receptors, then on antigen-presenting cells and other immunocompetent cells4

  • human studyPidotimod affects immunoglobulin production and their switching4

  • human studyPidotimod has an immunomodulatory activity which is able both to improve the clinical conditions of patients and to enhance and stimulate their immunity cells (lymphocytes but not only) functions acting on adaptive and innate immunity14

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  • human studyPidotimod is able to increase the concentration of salivary IgA directed against bacteria14

  • human studyPidotimod can modulate airway epithelial cells functions up-regulating the expression of toll-like receptors and acting on adhesion molecules14

  • human studyPidotimod could affect T-lymphocytes balance with a possible additional anti-allergic activity14

  • human studyPidotimod has immunomodulatory activity able to improve clinical conditions of patients and enhance immunity cell functions acting on adaptive and innate immunity15

  • human studyPidotimod is able to increase concentration of salivary IgA directed against bacteria15

  • human studyPidotimod can modulate airway epithelial cell functions by up-regulating toll-like receptor expression and acting on adhesion molecules15

  • human studyPidotimod could affect T-lymphocyte balance with possible additional anti-allergic activity in patients with atopic asthma15

  • human studyPidotimod affects phagocytosis and intracellular killing of Staphylococcus aureus by human circulating polymorphonuclear neutrophils and alveolar macrophages19

  • human studyPidotimod increases the level of immunoglobulins (IgA, IgM, IgG)25

  • human studyPidotimod increases T-lymphocyte subsets (CD3+, CD4+) endowed with immunomodulatory activity25

  • human studyPidotimod affects both innate and adaptive immune responses25

  • animalPidotimod stimulates natural killer cell activity and inhibits thymocyte cell death19

  • animalPidotimod decreased leukocyte infiltration in the spinal cord and brain20

  • animalPidotimod suppressed demyelination in the spinal cord20

  • animalPidotimod markedly increased populations of CD4CD25Foxp3 regulatory T cells (Tregs) and CD8Foxp3 Tregs20

  • animalPidotimod decreased numbers of CD4IFN-γ helper T cells (Th1), CD4IL-17 helper T cells (Th17), and CD8IL-17 cytotoxic T cells (Tc17) in the spleen20

  • animalPidotimod significantly diminished the population of B220TNF-α B cells in the spleen20

  • animalPidotimod effects on splenic lymphocytes were observed both in vitro and in vivo during the peak stage of EAE20

  • animalNeuroprotective effects of pidotimod in EAE mice may be attributed to its ability to regulate the balance of splenic lymphocytes20

  • animalPDT increased the recruitment of neutrophils and macrophages to the wound site22

  • animalPDT promoted the transcription of the pro-inflammatory cytokine il1b22

  • animalHigher expression of TLR2 and HLA-DR molecules is associated with Pidotimod25

  • animalPidotimod increases phagocytosis25

  • in vitroHigher expression of Toll Like Receptors (TLR) 2 and of HLA-DR molecules demonstrated in in vitro studies18

  • in vitroInduction of DC maturation and release of pro-inflammatory molecules in in vitro studies18

  • in vitroStimulation of T lymphocyte proliferation and differentiation toward a Th1 phenotype in in vitro studies18

  • in vitroIncrease in the phagocytosis associated with Pidotimod in in vitro studies18

  • in vitroUpregulation of HLA-DR and other co-stimulatory molecules (CD83 and CD86) expression18

  • in vitroIncrease in the activity of NK cells18

  • in vitroInhibits thymocyte apoptosis18

  • in vitroIncrease in salivary immunoglobulin (Ig) IgA levels18

  • in vitroUpregulation of TLR-7 and TLR-2 signaling pathway in respiratory epithelium18

  • in vitroPidotimod exerts immunomodulatory activity, modifying innate and adaptive immunity21

  • in vitroPidotimod firstly acts on Toll-like receptors, then on antigen-presenting cells and other immunocompetent cells21

  • in vitroPidotimod affects immunoglobulin production and their switching21

  • in vitroPidotimod increases the level of immunoglobulins (IgA, IgM, IgG)24

  • in vitroPidotimod increases T-lymphocyte subsets (CD3+, CD4+) endowed with immunomodulatory activity24

  • in vitroPidotimod affects both innate and adaptive immune responses24

  • in vitroHigher expression of TLR2 and of HLA-DR molecules has been demonstrated to be associated with Pidotimod24

  • in vitroPidotimod induces dendritic cell maturation24

  • in vitroPidotimod releases pro-inflammatory molecules24

  • in vitroPidotimod stimulates T lymphocyte proliferation and differentiation toward a Th1 phenotype24

  • in vitroPidotimod increases phagocytosis24

  • in vitroPidotimod induces dendritic cell maturation25

  • in vitroPidotimod causes release of pro-inflammatory molecules25

  • in vitroPidotimod stimulates T lymphocyte proliferation and differentiation toward Th1 phenotype25

  • in vitroThe inhibition of the Finasteride conjugate on 5α-reductase was stronger than that of Finasteride26

  • expert opinionPidotimod is a dipeptide which acts via multiple pathways of the immune system5

  • expert opinionPidotimod's activity was shown to be mediated via multiple pathways of the immune system5

  • expert opinionPidotimod is an immunostimulant researched for over two decades6

  • expert opinionPidotimod is an immunostimulant researched for over two decades7

  • expert opinionPidotimod is a synthetic dipeptide that modulates both innate and acquired immunity8

  • expert opinionPidotimod is a synthetic dipeptide9

  • expert opinionPidotimod enhances innate and adaptive immune responses9

  • expert opinionPidotimod exerts its effects by stimulating dendritic cells9

  • expert opinionPidotimod enhances toll-like receptor (TLR) expression9

  • expert opinionPidotimod promotes cytokine production, including IL-2 and IFN-γ9

  • expert opinionPidotimod supports both cellular and humoral immunity9

  • expert opinionPidotimod is a synthetic dipeptide with immunomodulatory properties10

  • expert opinionThe multifaceted mechanism of action of Pidotimod enables it to modulate innate and adaptive immunity10

  • expert opinionPidotimod is a synthetic dipeptide molecule showing immunomodulatory properties11

  • expert opinionPidotimod is an immunostimulant researched for over two decades13

  • expert opinionPidotimod (3-L-pyroglutamyl-L-thiazolidine-4carboxylic acid) is a synthetic dipeptide with immunomodulatory properties14

  • expert opinionPidotimod is a synthetic dipeptide with immunomodulatory properties15

  • expert opinionPidotimod is a synthetic dipeptide molecule with biological and immunological activity on both the adaptive and the innate immune responses16

  • expert opinionPidotimod (Polimod) is a synthetic dipeptide molecule17

  • expert opinionPidotimod is a synthetic dipeptide19

  • expert opinionPidotimod enhances innate and adaptive immune responses19

  • expert opinionPidotimod exerts its effects by stimulating dendritic cells, enhancing toll-like receptor (TLR) expression, and promoting cytokine production, including IL-2 and IFN-γ19

  • expert opinionPidotimod supports both cellular and humoral immunity19

  • expert opinionPidotimod is a synthetic dipeptide molecule which can improve immune responses in mice and humans, protecting hosts from infection22

  • expert opinionThe exact mechanism of protection remains ill-defined22

  • expert opinionpidotimod is able to ameliorate both innate and adaptive immunity23

  • expert opinionPidotimod (3-L-pyroglutamyl-L-thiaziolidine-4-carboxylic acid) is a synthetic dipeptide with immunomodulatory properties27

  • expert opinionPidotimod enables it to modulate innate and adaptive immunity27

  • expert opinionResearch on Pidotimod has attempted to clarify and define its mechanisms of action both in vitro and in vivo28

  • expert opinionPreclinical research will be essential to better understand the mechanisms of action of Pidotimod28

  • theoreticalPidotimod is a synthetic dipeptide molecule (3-l-pyroglutamyl-l-thiazolidine-4carboxilic acid) endowed with immunomodulatory activity that affects both innate and adaptive immune responses18

  • theoreticalPidotimod is a synthetic dipeptide21

Dosing

Based on 1 human study finding.

  • human studyFor prophylaxis of recurrences in both age groups, pidotimod needs to be continued for at least 2 months after the acute attack18

How the body handles it

Based on 1 human trial finding, 2 human study findings and 1 expert opinion finding.

  • human trialPidotimod ((R)-3-[(S)-(5-oxo-2-pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6), a new biological response modifier, was investigated in 3 different pharmacokinetic studies3

  • human studyPidotimod is rapidly absorbed by the gastrointestinal tract with a bioavailability of 45%18

  • human studyThe plasma half life is 4 h with poor metabolism and renal elimination of the unmodified molecule18

  • expert opinionThe plasma half life is 4 h with poor metabolism the unmodified molecule17

Safety and side effects

Based on 2 human trial findings, 10 human study findings, 2 animal findings and 2 expert opinion findings.

  • human trialNo safety concerns were raised in clinical studies with pidotimod5

  • human trialNo safety concerns were raised in pidotimod studies12

  • human studyPidotimod holds a safety profile suitable for oral administration1

  • human studyPidotimod has a safety profile and can be administered orally.2

  • human studyPidotimod is safe and well-tolerated in children4

  • human studyPidotimod may prevent vaccination-related adverse events10

  • human studyPidotimod has a good safety profile of the drug, without recording serious adverse events and mutagenic potential, and a very low incidence of side effects14

  • human studyPidotimod is a more safe solution in patients subjected to vaccination, if compared to lyophilized polibacterial, which can't be administered for thirty days before vaccination14

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  • human studyPidotimod has a good safety profile without serious adverse events and mutagenic potential15

  • human studyVery low incidence of side effects with Pidotimod15

  • human studyPidotimod is a safer solution in patients subjected to vaccination compared to lyophilized polibacterial15

  • human studyPidotimod is safe and well-tolerated in children21

  • animalZebrafish larvae were sensitive to PDT immersion causing toxicity at doses above 50 μg/mL22

  • animalFinasteride conjugate treated animals showed better viable condition than the Finasteride treated ones, suggesting the new compound may have improved toxicity profile than Finasteride26

  • expert opinionPidotimod has a safety profile suitable for oral administration9

  • expert opinionPidotimod has a safety profile suitable for oral administration19

What people use it for

Based on 11 human study findings and 18 expert opinion findings.

  • human studyPidotimod, a synthetic dipeptide, has been utilized for over three decades as an immunomodulatory agent to prevent recurrent respiratory infections, particularly in immunocompromised populations such as children and the elderly1

  • human studyPidotimod, a synthetic dipeptide, has been utilized for over three decades as an immunomodulatory agent to prevent recurrent respiratory infections, particularly in immunocompromised populations such as children and the elderly.2

  • human studyPidotimod may be helpful as an add-on strategy in managing children with infections4

  • human studyPidotimod has been evaluated in indications such as pneumonia, hand-foot-mouth disease, bronchiectasis, and chronic idiopathic urticaria6

  • human studyPidotimod has been utilized for over three decades as an immunomodulatory agent to prevent recurrent respiratory infections9

  • human studyPidotimod is used particularly in immunocompromised populations such as children and the elderly9

  • human studyPidotimod has been evaluated in pneumonia, hand-foot-mouth disease, bronchiectasis, and chronic idiopathic urticaria13

  • human studyPidotimod's efficacy has been tested both in children and in adults, with a focus of interest on respiratory tract infections14

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  • human studyEffects are more evident in the setting of immune defects such as senescence, Downs syndrome, and cancer16

  • human studyPidotimod may be helpful as an add-on strategy in managing children with infections21

  • human studyPidotimod has been used for preventing respiratory tract infections, and asthma or chronic obstructive pulmonary disease exacerbations24

  • expert opinionPidotimod is a useful management option in children and adults with respiratory tract infections5

  • expert opinionPidotimod can be used in combined therapy with antibiotics for pneumonia8

  • expert opinionPidotimod is useful in Down syndrome8

  • expert opinionPidotimod is useful in COVID-198

  • expert opinionPidotimod is useful in PFAPA8

  • expert opinionPidotimod is useful in wheezing8

  • expert opinionPidotimod is useful in urinary infections8

  • expert opinionPidotimod is indicated for use in adults and children over 3 years of age with documented cell-mediated immunodepression during respiratory and urinary tract infections10

  • expert opinionPidotimod should be considered during acute attacks of respiratory infections in children as well as in bacterial exacerbations in adults with CB18

  • expert opinionPidotimod can be considered in children and adults with acute and chronic respiratory conditions18

  • expert opinionPidotimod has been utilized for over three decades as an immunomodulatory agent to prevent recurrent respiratory infections, particularly in immunocompromised populations such as children and the elderly19

  • expert opinionPidotimod has potential in patients with chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD), allergic rhinitis, and viral infections, including SARS-CoV-219

  • expert opinionpidotimod is an immunostimulant for prevention and treatment of allergic diseases in pediatric population23

  • expert opinionPidotimod is potentially useful for asthma25

  • expert opinionPidotimod is potentially useful for COPD25

  • expert opinionPidotimod is potentially useful for recurrent respiratory tract infections25

  • expert opinionPidotimod is indicated for use in adults and children over 3 years of age with documented cell-mediated immunodepression during respiratory and urinary tract infections27

  • expert opinionPidotimod is an immunostimulant of synthetic origin introduced in some countries for the prevention of ARTIs in children28

Other findings

Based on 1 in vitro finding and 1 expert opinion finding.

  • in vitroFinasteride conjugate with C-18 amide N-polimod was synthesized26

  • expert opinionMore than a hundred papers have been published about Pidotimod since the early 90's24

Points of contention

Where the evidence is unsettled, thin, or says less than the popular claim — worth knowing before you draw conclusions.

Limited evidence

Much of the clinical evidence base is observational or expert opinion rather than controlled trials

Many claims of efficacy across chronic respiratory disease, HIV, COVID-19, bronchiectasis and elderly pneumonia are drawn from reviews graded as expert_opinion or human_observational rather than RCTs. One review (Pidotimod: the past and the present.) explicitly states that randomised controlled trials will be necessary to establish the real efficacy of pidotimod in preventing ARTIs in paediatric age.

Contested

An animal infection model failed to reproduce the protective effect seen in human/mouse reports

While reviews describe pidotimod improving immune responses and protecting hosts from infection, a zebrafish study (Pidotimod increases inflammation in wounded zebrafish embryos.) found no protection of uropathogenic E. coli or Mycobacterium marinum infected larvae following pidotimod treatment, and noted the exact mechanism of protection remains ill-defined and that toxicity occurred above 50 μg/mL.

Single source

Pharmacokinetic figures (45% bioavailability, 4 h half-life) come from limited sources

The stated 45% oral bioavailability appears in a single tier-2 web summary (Pidotimod: uses, Mechanism of action, and Pharmacokinetics_Chemicalbook), and the 4 h plasma half-life appears in Pidotimod: uses, Mechanism of action, and Pharmacokinetics_Chemicalbook and Pidotimod; detailed original PK data (Pharmacokinetics and oral bioavailability of pidotimod in humans. | Semantic Scholar) is only an abstract reference.

Other

One source concerns a finasteride derivative, not pidotimod itself

Synthesis and bioactivity of new Finasteride conjugate. describes a finasteride conjugate with 'N-polimod' and its effect on 5α-reductase and prostate hyperplasia in rats; this is a distinct chemical entity and does not describe pidotimod's own activity.

Using it with other compounds

Check a stack
  • SelankComplementary

    No documented conflict

    Selank is derived from tuftsin, an immune-signaling antibody fragment, and has reported immunomodulatory and Th1/Th2-balancing effects alongside its nootropic action. This overlaps with pidotimod's T-cell/cytokine tuning, so they share an immune-regulation dimension; the combination is plausible but the immune contribution of Selank is secondary to its CNS effects.

    Tier 4Theoretical — not established

    What the research doesn't fully establish

    Both peptides' mechanisms explicitly include T_cell_regulation in their approved tags. Pidotimod directly targets TLR-2/TLR-7, HLA-DR, and CD83/CD86 to drive Th1 differentiation and T-lymphocyte proliferation. Selank's mechanism includes 'Th1-Th2 and interferon signaling' pathways and carries the T_cell_regulation tag. Both are tagged anti_inflammatory. The proposed relationship correctly identifies these as shared dimensions: T-cell regulation (explicit in both) and anti-inflammatory effects (both tagged). The explanation accurately characterizes Selank's immune contribution as secondary to CNS effects while still present, which aligns with the mechanism material showing immunomodulatory effects alongside dopaminergic/GABAergic/BDNF actions. The 'complementary' relationship type is justified—they approach immune regulation through different primary mechanisms (innate/adaptive immunity vs. neuroimmune modulation) but converge on shared T-cell and anti-inflammatory dimensions.

    Shares anti inflammatory · T cell regulation

  • ThymulinSame downstream effect

    Worth caution

    Thymulin is a thymic hormone that drives T-lymphocyte maturation, tunes CD4/CD8 balance and boosts NK cytotoxicity — the same adaptive-immunity endpoints pidotimod promotes through dendritic-cell maturation and Th1 differentiation. They reach the same destination by different upstream mechanisms, which can be complementary for immune-deficiency support but also overlapping; stacking multiple immunostimulants adds little beyond one and should be monitored.

    Tier 4Theoretical — not established

    What the research doesn't fully establish

    Both peptides' mechanisms clearly converge on shared downstream immune outcomes. Pidotimod promotes T-lymphocyte proliferation, Th1 differentiation, and NK cell activity through dendritic cell maturation and TLR signaling. Thymulin directly promotes T-lymphocyte maturation, modulates CD4/CD8 balance, and enhances NK cytotoxicity. Both are tagged with innate_immune, anti_inflammatory, and T_cell_regulation. The proposed relationship correctly identifies that they operate through distinct upstream mechanisms (dendritic cell activation via TLRs vs. direct thymic hormone signaling) but converge on the same functional endpoints: T-cell differentiation, NK enhancement, and immune balance. The explanation's characterization of complementary but potentially overlapping mechanisms is consistent with the provided descriptions.

    Shares innate immune · anti inflammatory · T cell regulation

  • VilonSame downstream effect

    Worth caution

    Vilon is a Khavinson-school bioregulator reported to stimulate cellular immunity, improve CD4/CD8 ratio and enhance innate-immune markers — the same immune-enhancing goals as pidotimod but through a proposed gene/chromatin mechanism rather than TLR/dendritic-cell signaling. They overlap heavily on outcome, so combining them is more redundant than synergistic; choose based on evidence quality rather than stacking.

    Tier 4Theoretical — not established

    What the research doesn't fully establish

    Both peptides' mechanisms clearly support the three shared dimensions. Pidotimod targets TLR2/TLR7 and dendritic cells to drive Th1 differentiation, T-lymphocyte proliferation, NK cell activity, and immunoglobulin production (innate_immune, T_cell_regulation, anti_inflammatory via Th1 balance). Vilon's proposed chromatin/gene-expression mechanism similarly produces improved CD4/CD8 ratio, thymus stimulation, cellular immunity enhancement, and IL-1β/IL-6/TNF-α suppression (innate_immune, T_cell_regulation, anti_inflammatory). Both mechanisms converge on downstream immune activation and inflammatory modulation despite different entry points (receptor-mediated vs. gene-regulatory). The 'same_downstream' relationship is justified: they pursue overlapping immunological outcomes through mechanistically distinct pathways, making the redundancy concern valid.

    Shares innate immune · anti inflammatory · T cell regulation

  • LL-37Complementary

    No documented conflict

    Both modulate Toll-like receptor signaling and support innate immunity, but pidotimod primarily drives dendritic-cell maturation and adaptive (Th1/antibody) responses while LL-37 provides direct antimicrobial and TLR-modulating actions. This gives coverage across innate and adaptive immune defense.

    Tier 4Theoretical — not established

    What the research doesn't fully establish

    Both peptides' mechanisms clearly support the proposed complementary relationship. LL-37 targets multiple TLRs (TLR3, TLR7, TLR8, TLR9, TLR4) and FPR2, providing direct antimicrobial effects and broad-spectrum pathogen neutralization. Pidotimod targets TLR2 and TLR7, stimulating dendritic cell maturation and adaptive immunity (Th1 differentiation, T-lymphocyte proliferation, immunoglobulin production). All three shared dimensions are explicitly supported: (1) innate_immune—both activate TLR signaling and immune cell responses; (2) anti_inflammatory—both are tagged with this and modulate immune balance; (3) antimicrobial—LL-37 has direct antimicrobial activity while pidotimod reduces recurrent infections through immune enhancement. The explanation accurately characterizes their distinct but complementary mechanisms: LL-37 provides direct pathogen killing and TLR modulation, while pidotimod bridges innate to adaptive immunity via dendritic cell maturation. This division of labor across innate and adaptive defense is well-justified by the provided mechanisms.

    Shares innate immune · anti inflammatory · antimicrobial

  • ImunofanSame downstream effect

    Worth caution

    Pidotimod drives dendritic-cell maturation, Th1 differentiation, immunoglobulin production and phagocytosis through TLR2/TLR7 — a different upstream trigger than imunofan's thymopoietin pathway, but both raise T-cell competence and antimicrobial defense. They can complement each other for immune support, though effects on the same output should be monitored to avoid over-stimulation.

    Tier 4Theoretical — not established

    What the research doesn't fully establish

    Both peptides' mechanisms clearly establish the three shared dimensions claimed. Innate_immune: both enhance phagocytosis, NK cell activity, and antimicrobial defenses. Anti_inflammatory: both modulate cytokine balance (Imunofan reduces TNF/IL-6; Pidotimod drives Th1/IL-2/IFN-gamma). T_cell_regulation: both normalize T-cell ratios and enhance T-lymphocyte function. The proposed relationship correctly identifies distinct upstream triggers (thymopoietin receptors vs. TLR2/TLR7) converging on shared downstream immune outputs (enhanced T-cell competence, immunoglobulin production, phagocytic activity). The mechanisms support this 'same_downstream' characterization and the cautionary note about monitoring combined effects is reasonable given both drive overlapping immune pathways.

    Shares innate immune · anti inflammatory · T cell regulation

  • LactoferrinComplementary

    No documented conflict

    Pidotimod boosts adaptive and innate defences (dendritic-cell maturation, Th1, immunoglobulins) to reduce recurrent infections, while lactoferrin provides direct antimicrobial and iron-sequestering innate defence. Coming at infection resistance from adaptive-immune priming versus direct antimicrobial action, they are complementary rather than redundant.

    Tier 4Theoretical — not established

    What the research doesn't fully establish

    Both peptides' mechanisms clearly establish the three claimed shared dimensions: (1) innate_immune—lactoferrin targets microbial surfaces and activates innate responses; pidotimod enhances TLR signaling, dendritic-cell maturation, NK activity, and phagocytosis; (2) anti_inflammatory—lactoferrin shows anti-inflammatory and immunomodulatory activity; pidotimod modulates immune balance and reduces infection recurrence; (3) antimicrobial—lactoferrin has broad-spectrum antimicrobial activity; pidotimod reduces recurrent infections via immune enhancement. The complementary relationship is justified: lactoferrin operates via direct antimicrobial mechanisms (iron sequestration, cationic binding, ROS generation) and innate pathways, while pidotimod operates via adaptive-immune priming (Th1 differentiation, dendritic-cell maturation, immunoglobulin production) and TLR signaling. These represent distinct mechanistic approaches to infection resistance—one direct/innate, one adaptive-priming—making them complementary rather than redundant.

    Shares innate immune · anti inflammatory · antimicrobial

  • ElafinComplementary

    No documented conflict

    Pidotimod stimulates dendritic cell maturation and T-cell responses against recurrent infections, while elafin provides direct antiprotease and antimicrobial protection at epithelial surfaces. Complementary adaptive-plus-innate host defense.

    Tier 4Theoretical — not established

    What the research doesn't fully establish

    Both peptides' mechanisms clearly support the claimed shared dimensions and complementary relationship. Elafin targets innate immune proteases (neutrophil elastase, proteinase 3, cathepsin G/S) and provides direct antimicrobial activity with tissue protection at mucosal surfaces. Pidotimod stimulates innate immunity through TLR signaling and dendritic cell maturation while enhancing adaptive responses (T-cell proliferation, Th1 differentiation). Both are tagged with innate_immune, anti_inflammatory, and antimicrobial. The explanation accurately describes their distinct but complementary mechanisms: elafin acts as a direct protease inhibitor and antimicrobial agent at epithelial barriers, while pidotimod enhances immune cell activation and adaptive responses. These mechanisms work synergistically rather than redundantly, justifying the 'complementary' relationship type.

    Shares innate immune · anti inflammatory · antimicrobial

Safety and side effects

Safety and Tolerability

Reviews aggregating clinical studies reported that no safety concerns were raised with pidotimod, describing it as safe and well-tolerated in children with a good safety profile, no serious adverse events, no mutagenic potential, and a very low incidence of side effects (src-2, src-27, src-5, src-23, src-6, src-24). Reviews report its safety profile is suitable for oral administration (src-4, src-8, src-10, src-16).

Reviews also report that pidotimod may prevent vaccination-related adverse events and describe it as a safer solution in patients undergoing vaccination compared to lyophilized polibacterial products, which cannot be administered for thirty days before vaccination (src-1, src-20, src-6, src-24).

Animal Toxicity Signal

A zebrafish study reported that larvae were sensitive to pidotimod immersion, causing toxicity at doses above 50 μg/mL (src-29). The same study found no protection of uropathogenic E. coli or Mycobacterium marinum infected larvae following pidotimod treatment, and noted the exact mechanism of protection remains ill-defined (src-29, src-36).

Caveats

Much of the clinical safety and efficacy base is drawn from reviews graded as expert opinion or human observational rather than randomized controlled trials, and one review (src-21) states that randomised controlled trials will be necessary to establish real efficacy in preventing acute respiratory tract infections in paediatric age.

Reconstitution and handling

Dosing

No dose has been established for this compound in the sources provided as a formal recommendation. Pidotimod is described in reviews as an orally administered immunostimulant with a safety profile suitable for oral administration (src-4, src-8, src-10, src-16); the figures below are what the sources report, not guidance.

  • A pharmacokinetics summary reports pidotimod is rapidly absorbed by the gastrointestinal tract with a bioavailability of 45% (src-9). This 45% oral bioavailability figure appears in a single web summary.
  • Pharmacokinetic summaries report a plasma half-life of 4 hours with poor metabolism and renal elimination of the unmodified molecule (src-9, src-12).
  • A summary states that for prophylaxis of recurrences in both children and adults, pidotimod needs to be continued for at least 2 months after the acute attack (src-9).
  • Reviews describe use in adults and children over 3 years of age with documented cell-mediated immunodepression during respiratory and urinary tract infections (src-1, src-20).

Preparation Notes

The sources describe pidotimod as an orally administered agent rather than an injectable requiring reconstitution; no bacteriostatic-water reconstitution protocol is described in the provided claims. A product listing cites pidotimod at 98% purity, CAS 121808-62-6 (src-9). Detailed original pharmacokinetic data (src-13, published December 1994) is available only as an abstract reference, so the PK figures above should be read as coming from limited sources.

Sources

Ordered by evidence quality — the strongest first.

  1. From Legacy to Innovation: Pidotimod's Expanding ... - PMC(opens in a new tab)
    Tier 1Web · pmc.ncbi.nlm.nih.gov
  2. From Legacy to Innovation: Pidotimod’s Expanding Therapeutic Horizon(opens in a new tab)
    Tier 1Web · pmc.ncbi.nlm.nih.gov
  3. Pharmacokinetics and oral bioavailability of pidotimod in humans. | Semantic Scholar(opens in a new tab)
    Tier 1Web · semanticscholar.org
  4. Pidotimod in pediatrics: new evidence and future perspectives(opens in a new tab)
    Tier 1Web · pmc.ncbi.nlm.nih.gov
  5. Pidotimod: a review of its pharmacological features and clinical effectiveness in respiratory tract infections: Expert Review of Anti-infective Therapy: Vol 17, No 10(opens in a new tab)
    Tier 1Web · tandfonline.com
  6. Pidotimod: In-depth review of current evidence(opens in a new tab)
    Tier 1Web · pmc.ncbi.nlm.nih.gov
  7. Pidotimod: In-depth review of current evidence - PMC(opens in a new tab)
    Tier 1Web · pmc.ncbi.nlm.nih.gov
  8. An Italian multidisciplinary Delphi Consensus on new insights about the clinical relevance of Pidotimod.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 2025
  9. From Legacy to Innovation: Pidotimod's Expanding Therapeutic Horizon.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 2025
  10. Reappraisal of Pidotimod: an immunomodulatory agent with 30-year evidence.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 2024
  11. Pidotimod and Immunological Activation in Individuals Infected with HIV.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 2021
  12. Pidotimod: a review of its pharmacological features and clinical effectiveness in respiratory tract infections.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 2019
  13. Pidotimod: In-depth review of current evidence.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 2019
  14. Pidotimod: the state of art | Clinical and Molecular Allergy | Springer Nature Link(opens in a new tab)
    Tier 1Web · link.springer.com · 2015
  15. Pidotimod: the state of art.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 2015
  16. Pidotimod: a reappraisal.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 2009
  17. Pidotimod(opens in a new tab)
    Tier 2Web · journals.sagepub.com
  18. Pidotimod: uses, Mechanism of action, and Pharmacokinetics_Chemicalbook(opens in a new tab)
    Tier 2Web · m.chemicalbook.com
  19. PIDOTIMOD'S EXPANDING THERAPEUTIC HORIZON(opens in a new tab)
    Tier 2Web · mjhid.org · 2025
  20. Pidotimod alleviated experimental autoimmune encephalomyelitis by regulating the balance of splenic lymphocytes.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2025
  21. Pidotimod in pediatrics: new evidence and future perspectives.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2024
  22. Pidotimod increases inflammation in wounded zebrafish embryos.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2022
  23. Pidotimod in allergic diseases.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2020
  24. Immunostimulants in respiratory diseases: focus on Pidotimod(opens in a new tab)
    Tier 2Web · link.springer.com · 2019
  25. Immunostimulants in respiratory diseases: focus on Pidotimod.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2019
  26. Synthesis and bioactivity of new Finasteride conjugate.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2011
  27. Reappraisal of Pidotimod: an immunomodulatory agent with 30-year evidence - Minerva Medica 2024 August;115(4):503-15 - Minerva Medica - Journals(opens in a new tab)
    Tier 3Web · minervamedica.it
  28. Pidotimod: the past and the present.(opens in a new tab)
    Tier 3PubMed · pubmed.ncbi.nlm.nih.gov · 2013
  29. Pidotimod in pediatrics: new evidence and future perspectives | Multidisciplinary Respiratory Medicine(opens in a new tab)
    Tier 4Web · mrmjournal.org