Efficacy and safety of pidotimod in the prevention of recurrent respiratory infections in children: a multicentre study

Pidotimod increases inflammation in wounded zebrafish embryos

Pidotimod (PDT) is a synthetic dipeptide molecule which can improve immune responses in mice and humans, protecting hosts from infection. However, the exact mechanism of protection remains ill-defined. The effect of pidotimod has not yet been investigated in the inflammatory response of zebrafish. In this study, we used tail wound and infection models of zebrafish to study the effect of PDT on inflammation. We found that zebrafish larvae were sensitive to PDT immersion causing toxicity at doses above 50 μg/mL. The tail wound assay showed that PDT increased the recruitment of neutrophils and macrophages to the wound site and promoted the transcription of the pro-inflammatory cytokine il1b. However, we did not observe protection of uropathogenic Escherichia coli or Mycobacterium marinum infected zebrafish larvae following PDT treatment. This study provides a new platform for PDT research, which is worthy of further research to identify further effects of PDT therapy.

Prevention of recurrent respiratory infections : Inter-society Consensus

Recurrent respiratory infections (RRIs) are a common clinical condition in children, in fact about 25% of children under 1 year and 6% of children during the first 6 years of life have RRIs. In most cases, infections occur with mild clinical manifestations and the frequency of episodes tends to decrease over time with a complete resolution by 12 years of age. However, RRIs significantly reduce child and family quality of life and lead to significant medical and social costs.Despite the importance of this condition, there is currently no agreed definition of the term RRIs in the literature, especially concerning the frequency and type of infectious episodes to be considered. The aim of this consensus document is to propose an updated definition and provide recommendations with the intent of guiding the physician in the complex process of diagnosis, management and prevention of RRIs.

Prevention of New Respiratory Episodes in Children with Recurrent Respiratory Infections: An Expert Consensus Statement

In healthy infants and young children, the development of respiratory tract infections (RTIs) is extremely common. In this paper, we present an international consensus of the available approaches for the prevention of recurrent RTIs in children, including the atopic/allergic ones as well as those with asthma. Few convincing measures for reducing the frequency and clinical relevance of recurrent respiratory episodes in RTI-prone children have been developed until now. Among the most recently suggested measures, immunotherapy is attractive, but only for OM-85 is there a sufficient number of well-conducted clinical trials confirming efficacy in RTIs prevention with an adequate safety profile. In the case of probiotics, it is not clear which bacteria can offer the best results and which dosage and schedule of administration are the most effective. The problems of dosage and the schedule of administration are not solved also for vitamin D, despite some promising efficacy results. While we wait for new knowledge, the elimination or reduction as much as possible of the environmental factors that favor RTIs, vaccination when available and/or indicated, and the systematic application of the traditional methods for infection prevention, such as hand washing, remain the best measures to prevent recurrent infections in RTI-prone children.

Immunoactive preparations and regulatory responses in the respiratory tract: potential for clinical application in chronic inflammatory airway diseases

Introduction: The prevalence of chronic inflammatory airway diseases is rising. Their treatment with corticosteroids increases infection risk, while overuse of antimicrobial agents may increase morbidity and antimicrobial resistance. Nonspecific immunomodulatory compounds alter immune responses to both infectious and atopic challenges. These compounds may offer an alternative approach for symptom reduction and prophylaxis against both infections and exacerbations in chronic inflammatory airway disease.Areas covered: We assessed the available data on the efficacy of nonspecific immunomodulators including bacterial lysates, synthetic compounds, and vaccines in chronic rhinosinusitis (CRS); allergic and non-allergic rhinitis; chronic obstructive pulmonary disease (COPD), and asthma. A search of PubMed was carried out using the 'Clinical Trials' filter for each condition and immunomodulatory product detailed below, where available, data from meta-analyses were reported.Expert opinion: Pre-clinical data has revealed a coherent mechanistic path of action for oral immunomodulators on the respiratory immune system, principally via the gut-lung immune axis. In patients with asthma, allergic rhinitis, CRS, and COPD immunomodulatory therapy reduces symptoms, exacerbations, hospitalizations, and drug consumption. However, data are heterogeneous, and study quality remains limited. A lack of high-quality recent trials remains the major unmet research need in the field.

Role of viruses in asthma

Respiratory viral infections are the most important triggers of asthma exacerbations. Rhinovirus (RV), the common cold virus, is clearly the most prevalent pathogen constantly circulating in the community. This virus also stands out from other viral factors due to its large diversity (about 170 genotypes), very effective replication, a tendency to create Th2-biased inflammatory environment and association with specific risk genes in people predisposed to asthma development (CDHR3). Decreased interferon responses, disrupted airway epithelial barrier, environmental exposures (including biased airway microbiome), and nutritional deficiencies (low in vitamin D and fish oil) increase risk to RV and other virus infections. It is intensively debated whether viral illnesses actually cause asthma. Respiratory syncytial virus (RSV) is the leading causative agent of bronchiolitis, whereas RV starts to dominate after 1 year of age. Breathing difficulty induced by either of these viruses is associated with later asthma, but the risk is higher for those who suffer from severe RV-induced wheezing. The asthma development associated with these viruses has unique mechanisms, but in general, RV is a risk factor for later atopic asthma, whereas RSV is more likely associated with later non-atopic asthma. Treatments that inhibit inflammation (corticosteroids, omalizumab) effectively decrease RV-induced wheezing and asthma exacerbations. The anti-RSV monoclonal antibody, palivizumab, decreases the risk of severe RSV illness and subsequent recurrent wheeze. A better understanding of personal and environmental risk factors and inflammatory mechanisms leading to asthma is crucial in developing new strategies for the prevention and treatment of asthma.

Pidotimod: a review of its pharmacological features and clinical effectiveness in respiratory tract infections

Introduction: The majority of acute respiratory tract infections (RTIs) are caused by viruses and the overzealous use of antibacterial drugs, when not really required, is a cause for concern. This has led to evaluation of alternative approaches such as boosting the immune response in individuals who are most vulnerable to develop RTIs such as the very young and the elderly. Areas covered: This article overviews the immunostimulant activity and pharmacokinetic properties of pidotimod, and focuses on assessing its role in the treatment and prevention of acute RTIs through evaluation of clinical trials and real-world evidence. Articles were obtained from a full search of Medline, and this was augmented by published clinical studies known to the authors and manufacturer. Expert opinion: Pidotimod's activity was shown to be mediated via multiple pathways of the immune system. Comparison with placebo demonstrated significant advantages for pidotimod in terms of reduced reinfection rates [OR 0.20, 95% CI 0.12 to 0.33; p < 0.00001], a lesser need for antibiotics [mean difference -2.65, 95% CI -3.68 to -1.62; p < 0.00001] and rescue medications, and decreased absenteeism [mean difference-2.99, 95% CI -4.03 to -1.95; p < 0.00001]. No safety concerns were raised in these studies.

Pidotimod in the treatment of pediatric recurrent respiratory tract infection

Objective:

To observe the clinical efficacy of pidotimod in the treatment of recurrent respiratory tract infection in children.

Methods:

One hundred thirty-two patients with recurrent respiratory tract infection who received treatment in Tianan City Central Hospital were selected and divided into an observation group and a control group using random number table, 66 in each group. Patients in the control group were given conventional treatment, while patients in the observation group were given conventional treatment and pidotimod treatment; the clinical efficacy of the two therapies was compared. The levels of IgG and IgM were measured after treatment.

Results:

The vital signs and the content of inflammatory mediator and Th1/Th2 in serum before and after treatment were compared, and the clinical efficacy of the two groups was evaluated. The fever, pulmonary rale, cough and antiadoncus of patients in the observation group disappeared earlier than those in the control group (P<0.05). The onset duration of respiratory tract infection and days of antibiotic application of the observation group were shorter than those of the control group after treatment (P<0.05). The times of infection of the observation group were less than that of the control group (P<0.05). Before treatment, the two groups had no significant difference in the content of inflammatory mediators and Th1/Th2 in the serum (P>0.05). The serum content of tumor necrosis factor (TNF)-α and interleukin (IL)-4 of the two groups one week after treatment was lower than that before treatment, and the content of interferon (IFN)-γ and IFN-γ/IL-4 were higher than that before treatment; moreover the observation group had lower serum content of TFN-α and IL-4 and lower content of IFN-γ and IFN-γ/IL-4 compared to the control group (P<0.05). The overall response rate of the observation group was 92.4%, much higher than 81.8% in the control group (P<0.05).

Conclusion:

Pidotimod has a remarkable efficacy in the treatment of pediatric recurrent respiratory tract infection because it can effectively inhibit the infection and optimize Th1/Th2 immune function.

Effects of pidotimod and bifidobacteria mixture on clinical symptoms and urinary metabolomic profile of children with recurrent respiratory infections: a randomized placebo-controlled trial

BACKGROUND

Many preschool children develop recurrent respiratory tract infections (RRI). Strategies to prevent RRI include the use of immunomodulators as pidotimod or probiotics, but there is limited evidence of their efficacy on clinical features or on urine metabolic profile.

OBJECTIVE

To evaluate whether pidotimod and/or bifidobacteria can reduce RRI morbidity and influence the urine metabolic profile in preschool children.

MATERIALS AND METHODS

Children aged 3-6 years with RRI were enrolled in a four-arm, exploratory, prospective, randomized, double-blinded, placebo-controlled trial. Patients were randomly assigned to receive pidotimod plus bifidobacteria, pidotimod plus placebo, bifidobacteria plus placebo or double placebo for the first 10 days of each month over 4 consecutive months. Respiratory symptoms and infections were recorded with a daily diary by parents during the study. Metabolomic analyses on urine samples collected before and after treatment were performed.

RESULTS

Compared to placebo, children receiving pidotimod, alone or with bifidobacteria, had more symptom-free days (69 versus 44, p = 0.003; and 65 versus 44, p = 0.02, respectively) and a lower percentage of days with common cold (17% versus 37%, p = 0.005; and 15% versus 37%, p = 0.004, respectively). The metabolomic analysis showed that children treated with Pidotimod (alone or in combination with bifidobacteria) present, respect to children treated with placebo, a biochemical profile characterized by compounds related to the pathway of steroids hormones, hippuric acid and tryptophan. No significant difference in the metabolic profile was found between children receiving bifidobacteria alone and controls.

CONCLUSIONS

Preschool children with RRI treated with pidotimod have better clinical outcomes and a different urine metabolomic profile than subjects receiving placebo. Further investigations are needed to clarify the connection between pidotimod and gut microbiome.

Pidotimod: In-depth review of current evidence

Pidotimod, an immunostimulant, is researched for over two decades. Current evidence indicates its utility in a variety of indications in children as well as in adults. Its immunostimulant activity has been firmly established in the management of recurrent respiratory infections in children with or without asthma. Compared to standard of care alone, addition of pidotimod to standard of care significantly prevents the recurrences and reduces the severity and duration of acute episodes, ultimately resulting in reduced visits to pediatric clinics and lower absenteeism at school. In adults, pidotimod is effective in the prevention and treatment of acute infectious exacerbations of chronic bronchitis and chronic obstructive pulmonary disease (COPD). Further, it has been evaluated in indications such as pneumonia, hand–food–mouth disease, bronchiectasis, and chronic idiopathic urticaria. From a total of 32 studies conducted in child (24 studies) and adult (8 studies) population, this in-depth review discusses the current evidence of pidotimod. With further exploration, the immunostimulant activity of pidotimod might be extended to different immunological disorders.

Pidotimod, an immunostimulant in pediatric recurrent respiratory tract infections: A meta-analysis of randomized controlled trials

OBJECTIVES

Recurrent respiratory tract infections (RRTIs) remain a great challenge to pediatricians, because they can increase the risk of various complications and there is no confirmed effective treatment. In the present study, we aimed to assess the effectiveness and safety of pidotimod (PDT), an immunostimulant, in treatment of RRTIs in children aged 14 years and under.

METHODS

PubMed, EMBASE, Web of Science, Cochrane Library, ClinicalTrials.gov, CBM and CNKI were searched from their inception up to February 2018. All randomized controlled trials (RCTs) using PDT with various treatment durations and enrolling participants <14 years of age were included in the present review. The interventions were PDT plus conventional treatment (e.g. anti-bacterial and antiviral therapy) or PDT alone versus the conventional treatment plus placebo or conventional treatment alone.

RESULTS

A total of 29 RCTs consisting of 4344 pediatric patients were included in this meta-analysis. Ten RCTs were published from Italy, Russia or Greece, and 19 RCTs were published by Chinese groups. However, appropriate randomization methods were only used in 15 trials. Only one study had explicit allocation concealment. Since only eight RCTs were double-blind and placebo controlled, the evidence was not assessed as high quality. The meta-analysis indicates that treatment with PDT resulted in a significant increase in the proportion of participants who had lower RTIs (RR 1.59; 95% CI 1.45-1.74, p < 0.00001) compared with the conventional treatment. PDT could significantly decrease the duration of cough and fever. The number of patients in using antibiotics was also remarkably decreased in the PDT treatment group. Moreover, PDT administration improved the levels of serum immunoglobulin (IgG, IgA, or IgM) and T-lymphocyte subtypes (CD3+, CD4+). Besides, PDT administration did not increase the risk of adverse events of any cause (RR = 1.05, 95% CI 0.72-1.54, p = 0.80).

CONCLUSIONS

PDT showed a good efficacy and safety in treatment of pediatric RRTIs. Further high-quality and large-scale RCTs are still required to provide confirmatory evidence.

TRIAL REGISTRATION

The protocol of this study can be found at PROSPERO with the registration number of CRD42018093541.

Nonspecific immunomodulators for recurrent respiratory tract infections, wheezing and asthma in children: a systematic review of mechanistic and clinical evidence

PURPOSE OF REVIEW

To provide an overview of the mechanistic and clinical evidence for the use of nonspecific immunomodulators in paediatric respiratory tract infection (RTI) and wheezing/asthma prophylaxis.

RECENT FINDINGS

Nonspecific immunomodulators have a long history of empirical use for the prevention of RTIs in vulnerable populations, such as children. The past decade has seen an increase in both the number and quality of studies providing mechanistic and clinical evidence for the prophylactic potential of nonspecific immunomodulators against both respiratory infections and wheezing/asthma in the paediatric population. Orally administered immunomodulators result in the mounting of innate and adaptive immune responses to infection in the respiratory mucosa and anti-inflammatory effects in proinflammatory environments. Clinical data reflect these mechanistic effects in reductions in the recurrence of respiratory infections and wheezing events in high-risk paediatric populations. A new generation of clinical studies is currently underway with the power to position the nonspecific bacterial lysate immunomodulator OM-85 as a potential antiasthma prophylactic.

SUMMARY

An established mechanistic and clinical role for prophylaxis against paediatric respiratory infections by nonspecific immunomodulators exists. Clinical trials underway promise to provide high-quality data to establish whether a similar role exists in wheezing/asthma prevention.

Pharmacokinetics of pidotimod in broiler chickens by UHPLC-MS/MS after oral and intravenous administration

Pidotimod is widely used in children as an immune promoter but it has not been fully evaluated in animals. The pharmacokinetics of pidotimod and its oral bioavailability have not been described in broiler chickens. We developed a simple and sensitive UHPLC-MS/MS assay for rapid determination of pidotimod levels in chicken blood. Recoveries were nearly 100% and the coefficients of accuracy and precision were minimal. Healthy broiler chickens were given 10 mg/kg pidotimod either orally or intravenously. The oral pidotimod was rapidly absorbed (time to reach maximum concentration, 1.25 h) and rapidly eliminated (the mean residence time was 3.2 h). A noncompartmental analysis of the intravenous route indicated a mean plasma clearance of 2.2 L (h kg)^-1 with an estimated mean volume of distribution at steady state of 12.69 L/kg. The bioavailability of pidotimod after oral dosing was 27%.

Promising approaches for the treatment and prevention of viral respiratory illnesses

Viral respiratory tract infections are the most common human ailments, leading to enormous health and economic burden. Hundreds of viral species and subtypes have been associated with these conditions, with influenza viruses, respiratory syncytial virus, and rhinoviruses being the most frequent and with the highest burden. When considering prevention or treatment of viral respiratory tract infections, potential targets include the causative pathogens themselves but also the immune response, disease transmission, or even just the symptoms. Strategies targeting all these aspects are developing concurrently, and several novel and promising approaches are emerging. In this perspective we overview the entire range of options and highlight some of the most promising approaches, including new antiviral agents, symptomatic or immunomodulatory drugs, the re-emergence of natural remedies, and vaccines and public health policies toward prevention. Wide-scale prevention through immunization appears to be within reach for respiratory syncytial virus and promising for influenza virus, whereas additional effort is needed in regard to rhinovirus, as well as other respiratory tract viruses.

Pidotimod exacerbates allergic pulmonary infection in an OVA mouse model of asthma

Pidotimod is a synthetic dipeptide with biological and immuno‑modulatory properties. It has been widely used for treatment and prevention of recurrent respiratory infections. However, its impact on the regulation of allergic pulmonary inflammation is still not clear. In the current study, an ovalbumin (OVA)‑induced allergic asthma model was used to investigate the immune‑modulating effects of pidotimod on airway eosinophilia, mucus metaplasia and inflammatory factor expression compared with dexamethasone (positive control). The authors determined that treatment with pidotimod exacerbated pulmonary inflammation as demonstrated by significantly increased eosinophil infiltration, dramatically elevated immunoglobulin E production, and enhanced T helper 2 response. Moreover, treatment failed to attenuate mucus production in lung tissue, and did not reduce OVA‑induced high levels of FIZZ1 and Arg1 expression in asthmatic mice. In contrast, administration of dexamethasone was efficient in alleviating allergic airway inflammation in OVA‑induced asthmatic mice. These data indicated that pidotimod as an immunotherapeutic agent should be used cautiously and the effectiveness for controlling allergic asthma needs further evaluation and research.

Metabolomic profile of children with recurrent respiratory infections

Recurrent respiratory infections (RRI) represent a widespread condition which has a severe social and economic impact. Immunostimulants are used for their prevention. It is crucial to better characterize children with RRI to refine their diagnosis and identify effective personalized prevention strategies. Metabolomics is a high-dimensional biological method that can be used for hypothesis-free biomarker profiling, examining a large number of metabolites in a given sample using spectroscopic techniques. Multivariate statistical data analysis then enables us to infer which metabolic information is relevant to the biological characterization of a given physiological or pathological condition. This can lead to the emergence of new, sometimes unexpected metabolites, and hitherto unknown metabolic pathways, enabling the formulation of new pathogenetic hypotheses, and the identification of new therapeutic targets. The aim of our pilot study was to apply mass-spectrometry-based metabolomics to the analysis of urine samples from children with RRI, comparing these children's biochemical metabolic profiles with those of healthy peers. We also compared the RRI children's and healthy controls' metabolomic urinary profiles after the former had received pidotimod treatment for 3 months to see whether this immunostimulant was associated with biochemical changes in the RRI children's metabolic profile. 13 children (age range 3-6 yeas) with RRI and 15 matched per age healthy peers with no history of respiratory diseases or allergies were enrolled. Their metabolomic urine samples were compared before and after the RRI children had been treated with pidotimod for a period of 3 months. Metabolomic analyses on the urine samples were done using mass spectrometry combined with ultra-performance liquid chromatography (UPLC-MS). The resulting spectroscopic data then underwent multivariate statistical analysis and the most relevant variables characterizing the two groups were identified. Data modeling with post-transformation of PLS2-Discriminant Analysis (ptPLS2-DA) generated a robust model capable of discriminating the urine samples from children with RRI from those of healthy controls (R²=0.92,Q²_CV7-fold=0.75, p-value<0.001). The dataset included 1502 time per mass variables, and 138 of them characterized the difference between the two groups. Thirty-five of these distinctive 138 variables persisted in the profiles of the children with RRI after pidotimod treatment. Metabolomics can discriminate children with RRI from healthy controls, suggesting that the former have a dysregulated metabolic profile. Among the variables characterizing children with RRI there are metabolites that may reflect the presence of a different microbiome. After pidotimod treatment, the metabolic profile of the children with RRI was no longer very different from that of the healthy controls, except for the persistence of some microbiome-related variables. We surmise that pidotimod partially "restores" the altered metabolic profile of children with RRI, without modifying the metabolites related to the composition of the gut microbiota. In the light of these results, we hypothesize a potential synergic effect of the combined use of immunostimulants and probiotics for the purpose of prevention in children with RRI.

A robust LC-MS/MS method for the determination of pidotimod in different biological matrixes and its application to in vivo and in vitro pharmacokinetic studies

Pidotimod, (R)-3-[(S)-(5-oxo-2-pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, was frequently used to treat children with recurrent respiratory infections. Preclinical pharmacokinetics of pidotimod was still rarely reported to date. Herein, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to determine pidotimod in rat plasma, tissue homogenate and Caco-2 cells. In this process, phenacetin was chosen as the internal standard due to its similarity in chromatographic and mass spectrographic characteristics with pidotimod. The plasma calibration curves were established within the concentration range of 0.01-10.00μg/mL, and similar linear curves were built using tissue homogenate and Caco-2 cells. The calibration curves for all biological samples showed good linearity (r>0.99) over the concentration ranges tested. The intra- and inter-day precision (RSD, %) values were below 15% and accuracy (RE, %) was ranged from -15% to 15% at all quality control levels. For plasma, tissue homogenate and Caco-2 cells, no obvious matrix effect was found, and the average recoveries were all above 75%. Thus, the method demonstrated excellent accuracy, precision and robustness for high throughput applications, and was then successfully applied to the studies of absorption in rat plasma, distribution in rat tissues and intracellular uptake characteristics in Caco-2 cells for pidotimod.

Immunomodulatory activity of pidotimod administered with standard antibiotic therapy in children hospitalized for community-acquired pneumonia

BACKGROUND

Several attempts to improve immune function in young children have been made and encouraging results have been collected with pidotimod (PDT), a synthetic dipeptide molecule that seems to have immunomodulatory activity on both innate and adaptive responses. Until now, the effects of PDT on the immune system have only been studied in vivo after long-term administration to evaluate whether its immunomodulatory activity might prevent the development of infections. This study was planned to evaluate the immunomodulatory activity of PDT administered together with standard antibiotic therapy in children hospitalized for community-acquired pneumonia (CAP).

METHODS

A total of 20 children hospitalized for community-acquired pneumonia (CAP) were randomized at a 1:1 ratio to receive either standard antibiotics plus pidotimod (PDT) or standard antibiotics alone to evaluate the immunomodulatory activity of PDT. Blood samples for the evaluation of immunological parameters were drawn at the time of recruitment (T0) (i.e., before therapy administration), at T3 and T5 (i.e., 3 and 5 days after the initiation of therapy) as well as at T21 (i.e., 7 days after the therapy ended).

RESULTS

Following pneumococcal polysaccharide stimulation, the percentage of dendritic cells (DCs) expressing activation and costimulatory molecules was significantly higher in children receiving PDT plus antibiotics than in the controls. A significant increase in tumor necrosis factor-α and/or interleukin-12 secretion and expression of toll like receptor 2 was observed in PDT-treated children compared with controls; this was followed by an increased release of proinflammatory cytokines by monocytes. In the PDT-treated group, mRNA expression of antimicrobial peptides and genes involved in the inflammatory response were also augmented in comparison with the controls.

CONCLUSIONS

These results demonstrate, for the first time, that PDT administered together with standard antibiotics is associated with a favorable persistent immunomodulatory effect in children with CAP.