Comparing clinical trial population representativeness to real-world users of 17 biologics approved for immune-mediated inflammatory diseases: An external validity analysis of 66,639 biologic users from the Italian VALORE project.

To date, no population-based studies have specifically explored the external validity of pivotal randomized clinical trials (RCTs) of biologics simultaneously for a broad spectrum of immuno-mediated inflammatory diseases (IMIDs). The aims of this study were, firstly, to compare the patients' characteristics and median treatment duration of biologics approved for IMIDs between RCTs' and real-world setting (RW); secondly, to assess the extent of biologic users treated for IMIDs in the real-world setting that would not have been eligible for inclusion into pivotal RCT for each indication of use. Using the Italian VALORE distributed database (66,639 incident biologic users), adult patients with IMIDs treated with biologics in the Italian real-world setting were substantially older (mean age ± SD: 50 ± 15 years) compared to those enrolled in pivotal RCTs (45 ± 15 years). In the real-world setting, certolizumab pegol was more commonly used by adult women with psoriasis/ankylosing spondylitis (F/M ratio: 1.8-1.9) compared to RCTs (F/M ratio: 0.5-0.6). The median treatment duration (weeks) of incident biologic users in RW was significantly higher than the duration of pivotal RCTs in almost all indications for use and most biologics (4-100 vs. 6-167). Furthermore, almost half (46.4%) of biologic users from RW settings would have been ineligible for inclusion in the respective indication-specific pivotal RCTs. The main reasons were: advanced age, recent history of cancer and presence of other concomitant IMIDs. These findings suggest that post-marketing surveillance of biologics should be prioritized for those patients.

Investigating a Signal of Acquired Hemophilia Associated with COVID-19 Vaccination: A Systematic Case Review.

Acquired hemophilia A (AHA), a rare but life-threatening disorder, most commonly occurs in older people and during pregnancy. During the coronavirus disease 2019 (COVID-19) vaccination campaign, an unexpected number of newly diagnosed AHA patients have been identified in clinical practice that were temporally related to COVID-19 vaccination. We present the result of a signal detection analysis aimed at exploring a possible association between COVID-19 immunization and occurrence of AHA. A disproportionality analysis on the World Health Organization (WHO) database was performed to investigate the presence of a signal of risk for AHA associated with COVID-19 vaccines. Reports of AHA associated with any COVID-19 vaccine included in the WHO database were then integrated with those available on the Food and Drug Administration Vaccine Adverse Events Reporting System and those published in the medical literature. The WHO database included 146 reports of AHA. The information component (IC) was significant for the association of AHA with all COVID-19 vaccines (IC025: 1.1) and with the vaccine product BNT162b2 (IC025: 1.6). After duplicate exclusion, 96 unique cases of AHA following COVID-19 vaccines have been reviewed. Median time to diagnosis was 18 days and 40% of cases documented the occurrence after the second dose. Overall, in 57% of the investigated cases, a preexisting condition predisposing to AHA was excluded. About 22% of cases occurred in subjects with age ≤65 years and there was no case associated with pregnancy. Mortality was 11%. Although we cannot exclude that the unexpected frequency of AHA diagnosis can be explained by a detection bias, the signal for COVID-19 vaccine-related AHA is robust and deserves further investigations.

Cases of acquired hemophilia A following COVID-19 vaccines: Cogent safety signal or possible reporting/detection bias? Preliminary evidence from Tuscany, Italy.

PURPOSE: Several case reports of acquired hemophilia A (AHA) following COVID-19 vaccines were recently published. A possible increased incidence of AHA during the COVID-19 vaccination campaign was also suggested. We aimed at generating evidence for the preliminary assessment of the association between AHA and COVID-19 vaccination through an ecological study in one Italian region, Tuscany. METHODS: An ecological study was performed using the population-based administrative data source of Tuscany. Per each year between 2017 and 2021, we included patients aged 5+ and active into the database as of January 1. Temporal patterns of annual incidence of possible AHA cases and AHA-tested patients were respectively observed. The rates of possible AHA cases per AHA-tested patients were calculated in 2021 and 2017-2019, respectively (calendar year 2020 was excluded because non-representative of the pre-pandemic era). Age-sex standardization was applied. Poisson's 95% confidence intervals (95% CI) were estimated. Statically significant differences were defined as absence of 95% CI overlap. RESULTS: In 2021, standardized incidence of both possible AHA cases (5.6/million subjects/year; 95% CI = 3.4-8.7) and AHA-tested patients (60.7/1000 subjects/year; 95% CI = 60.4-60.9) showed the lowest point estimates, though only the latter was statistically different compared to previous calendar years. The standardized rate of possible AHA cases per AHA-tested patients was 9.2/100000 (95% CI = 5.6-14.3) in 2021 and 12.5/100000 (95% CI = 8.2-18.1) during 2017-2019. CONCLUSIONS: These preliminary findings do not support the hypothesis of an increased incidence of AHA cases during the COVID-19 vaccination campaign. However, in 2021, the still ongoing healthcare access restrictions might have contributed to the low incidence of AHA and laboratory tests observed. Therefore, large-scale multi-database studies are warranted.

Biosimilars approvals by thirteen regulatory authorities: A cross-national comparison.

Biosimilars are biological medicines highly similar to a previously licensed reference product and their licensing is expected to improve access to biological therapies. This study aims to present an overview of biosimilars approval by thirteen regulatory authorities (RA). The study is a cross-national comparison of regulatory decisions involving biosimilars in Argentina, Australia, Brazil, Chile, Canada, Colombia, Europe, Hungary, Guatemala, Italy, Mexico, Peru and United States. We examined publicly available documents containing information regarding the approval of biosimilars and investigated the publication of public assessment reports for registration applications, guidelines for biosimilars licensing, and products approved. Data extraction was conducted by a network of researchers and regulatory experts. All the RA had issued guidance documents establishing the requirements for the licensing of biosimilars. However, only three RA had published public assessment reports for registration applications. In total, the investigated jurisdictions had from 19 to 78 biosimilars approved, most of them licensed from 2018 to 2020. In spite of the advance in the number of products in recent years, some challenges still persist. Limited access to information regarding the assessment of biosimilars by RA can affect confidence, which may ultimately impact adoption of these products in practice.

Convalescent Plasma Therapy for COVID-19: State of the Art.

Convalescent plasma (CP) therapy has been used since the early 1900s to treat emerging infectious diseases; its efficacy was later associated with the evidence that polyclonal neutralizing antibodies can reduce the duration of viremia. Recent large outbreaks of viral diseases for which effective antivirals or vaccines are still lacking has renewed the interest in CP as a life-saving treatment. The ongoing COVID-19 pandemic has led to the scaling up of CP therapy to unprecedented levels. Compared with historical usage, pathogen reduction technologies have now added an extra layer of safety to the use of CP, and new manufacturing approaches are being explored. This review summarizes historical settings of application, with a focus on betacoronaviruses, and surveys current approaches for donor selection and CP collection, pooling technologies, pathogen inactivation systems, and banking of CP. We additionally list the ongoing registered clinical trials for CP throughout the world and discuss the trial results published thus far.

Utilisation patterns and clinical impact of the introduction of infliximab-biosimilar in Tuscany, Italy: real world evidence following the recommendation of switching for non-medical reasons.

OBJECTIVES: This study was aimed at assessing the impact of a non-medical recommendation on drug-utilisation patterns and clinical outcomes in a central Region of Italy (Tuscany). METHODS: We performed a pre-post study on data collected in Tuscan healthcare administrative databases. We included patients with diagnosis of rheumatoid arthritis, or psoriatic arthritis, or ankylosing spondylitis, or ulcerative colitis, or Crohn's disease, or psoriasis. The first analysis compared patients treated with infliximab on January 1st, 2013 (originator only available) to those on January 1st, 2016 (both originator and biosimilar available). The second analysis compared infliximab-originator users with infliximab-biosimilar ones. Adjusted odds ratios (OR) of persistence on treatment, Emergency Department (ED) admissions, hospitalisations and specialist visits were calculated. RESULTS: The first analysis included 606 patients and the second 434. In both analyses, we did not observe any significant difference in persistence. In the first analysis, the 2016 infliximab-originator cohort showed a significant association with the risk of having at least one ED admission (OR 1.54, 95% CI 1.02 to 2.31). A significant difference of accessing a specialist visit (more frequently rheumatologic) was observed in the 2016 cohort (OR 1.52, 95% CI 1.05 to 2.20). In the second analysis, the risk of having at least one hospitalisation decreased significantly in switchers to infliximab-biosimilar (OR 0.49, 95% CI 0.26 to 0.96). CONCLUSIONS: Our study showed no relevant changes in the clinical outcomes following the introduction of infliximab-biosimilar. The few observed differences observed can be explained mainly by a selective switching to infliximab-biosimilar in patients with lower burden of disease.

Use of antiseizure medications and safety of branded versus generic formulations: A comparative study on Tuscan administrative databases.

PURPOSE: To assess patterns of use of antiseizure medications (ASMs) and to compare the safety of generic versus branded formulations in terms of admission to hospital or to emergency department (ED). METHODS: We conducted a drug utilization study with a propensity score-matched design using the administrative databases of the Italian Tuscany region. New users of ASMs during 2015 with no history of neoplasia were considered and their first prescription was classified as: available only as branded (only-B-ASM); branded with generic available (B-ASM); and generic (G-ASM). Patients with G-ASM first prescription were matched with four patients with B-ASM prescription. Participants were followed up for one year or until the date of death or diagnosis of neoplasia. Cox regression models were fitted to estimate the risk of admission to hospital or ED. RESULTS: We identified 36,601 ASM new-users, including 2094 (6.4%) with only-B-ASM as first prescription, 24,588 (74.9%) with B-ASM, and 5788 (17.6%) with G-ASM. We found no differences in the risk of admission to hospital or ED (Hazard Ratio (HR), 0.92; 95% Confidence Interval (CI), 0.85-1.02) among users of generic ASMs compared to those using branded ASMs. CONCLUSIONS: In our study population, generic ASMs were used less than branded ones. The similarity in the safety of branded and generic formulations suggests that generic ASMs could be the preferred formulation in current clinical practice resulting in a substantial decrease in the cost of treatment.

Progressive multifocal leukoencephalopathy and anti-CD20 monoclonal antibodies: What do we know after 20 years of rituximab.

In 1997, rituximab was the first monoclonal antibody clinically approved for the treatment of cancer. Ten years later, progressive multifocal leukoencephalopathy (PML), until that time a rare opportunistic infection mostly seen in AIDS patients, was added as a black box warning after retrospective case-control studies showed an increased incidence in both B-cell lymphoproliferative disorders and autoimmune diseases. Despite more than 5 million worldwide exposures to date (and about 500 000 new exposures per year), insufficient data collection has hampered identification of risk minimization strategies, and concerns have been raised about a class effect extending to the newer anti-CD20 monoclonal antibodies (ofatumumab, obinutuzumab, and ocrelizumab). Here, we report current PML case counts registered in the FAERS and EudraVigilance databases and comment on severe CD4+ T lymphopenia as a plausible common mechanism of action for anti-CD20 antibodies in causation of PML.

Exploring pharmacological approaches for managing cytokine storm associated with pneumonia and acute respiratory distress syndrome in COVID-19 patients.

Sars-CoV-2 complications include pneumonia and acute respiratory distress syndrome (ARDS), which require intensive care unit admission. These conditions have rapidly overwhelmed healthcare systems, with detrimental effects on the quality of care and increased mortality. Social isolation strategies have been implemented worldwide with the aim of reducing hospital pressure. Among therapeutic strategies, the use of immunomodulating drugs, to improve prognosis, seems promising. Particularly, since pneumonia and ARDS are associated with a cytokine storm, drugs belonging to therapeutic classes as anti-IL-6, anti-TNF, and JAK inhibitors are currently studied. In this article, we discuss the potential advantages of the most promising pharmacological approaches.

NSAID-induced enteropathy: are the currently available selective COX-2 inhibitors all the same?

Nonsteroidal anti-inflammatory drugs (NSAIDs) can induce intestinal mucosal damage, but the underlying mechanisms remain poorly understood. The present study investigated the effects of celecoxib, etoricoxib, indomethacin, and diclofenac on small bowel integrity in rats. Male rats were treated orally with test drugs for 14 days. Animals were processed for assessment of blood hemoglobin levels and hepatic mitochondrial functions, microscopic evaluation of small intestinal damage, Western blot analysis of cyclooxygenase-1 and -2 (COX-1, COX-2) expression, and assay of malondialdehyde (MDA), myeloperoxidase (MPO), and prostaglandin E2 (PGE2) levels in small intestine. Indomethacin and diclofenac decreased blood hemoglobin levels, whereas etoricoxib and celecoxib were without effects. Celecoxib caused a lower degree of intestinal damage in comparison with the other test drugs. Indomethacin and diclofenac, but not etoricoxib or celecoxib, reduced intestinal PGE2 levels. Test drugs did not modify intestinal COX-1 expression, although they enhanced COX-2, with the exception of celecoxib, which downregulated COX-2. Indomethacin, diclofenac, and etoricoxib altered mitochondrial respiratory parameters, although celecoxib was without effects. Indomethacin or diclofenac increased MDA and MPO levels in both jejunum and ileum. In the jejunum, etoricoxib or celecoxib did not modify such parameters, whereas in the ileum, etoricoxib, but not celecoxib, increased both MDA and MPO levels. These findings suggest that nonselective NSAIDs and etoricoxib can induce enteropathy through a topic action, whereas celecoxib lacks relevant detrimental actions. The selectivity profile of COX-1/COX-2 inhibition by test drugs and the related effects on prostaglandin production do not appear to play a major role in the pathogenesis of enteropathy.

Lessons learnt from the preclinical discovery and development of ensitrelvir as a COVID-19 therapeutic option.

INTRODUCTION: The COVID-19 pandemic stimulated the development of several therapeutic tools with several degrees of success. Ensitrelvir, a protease inhibitor that blocks the replication of SARS-CoV-2, can reduce the viral load and the severity of symptoms in infected patients and become available for emergency use in Japan. Clinical trials showed a good tolerability profile although the potential for interactions with substrates, inhibitors, and inducers of CYP3A must be considered. The occurrence of resistance is also a matter of investigation. AREAS COVERED: In this article, the authors describe the development of ensitrelvir starting from the identification of the molecule to the pre-clinical and clinical trials up to the post-authorization phase. EXPERT OPINION: Ensitrelvir was developed in a late phase of the pandemic when the availability of patients that can be candidate to enter the clinical trial was limited with consequences for the possibility of assessing certain outcomes and for the robustness of results. Although the evidence about the benefits of ensitrelvir in COVID-19 is not questionable, the problems of interactions with other drugs, emerging resistant variants, the availability of alternative therapeutic options, costs, and accessibility will concur to its probable limited clinical use in the future.

Drug Use Patterns in Myasthenia Gravis: A Real-World Population-Based Cohort Study in Italy.

Background: In the context of a comparative study of efficacy and safety of drugs used in rare neuromuscular and neurodegenerative diseases (CAESAR-call AIFA_FV_2012-13-14), we assessed the use patterns of drugs indicated for myasthenia gravis (MG). Methods: A retrospective cohort study was conducted based on administrative healthcare data. For a cohort of MG patients, prevalent and incident use of pyridostigmine (Py) and other indicated drugs in the first year after case identification was evaluated. Prevalent combined use of major therapies (azathioprine (Az), prednisone (Pr), vitamin D (Vd)) stratified by Py use was assessed, and a comparison between therapies at the time of MG identification and during the first year of follow-up was performed. Results: We included 2369 MG patients between 2013 and 2019. Among them, prevalent and incident Py users were 38.4% and 22.0%, respectively. In the first year of follow-up, the use of Pr was observed in 74.5% of Py prevalent users and in 82.0% of Py incident users, respectively; the use of Az was observed in 24.9% and 23.0%, respectively; and the use of Vd was observed in 53.3% and 48.2%, respectively. Among 910 Py prevalent users, 13.1% also used Az, Pr, and Vd, while 15.3% used none of these. Among 938 non-Py users, 2.7% used Az, Pr, and Vd, while 53.8% used none of these. During the first year, an increase in combined therapies was evident in incident Py users. Conclusions: Our results suggest that, for some MG patients, there may be a need for treatments that combine a rapid onset of benefit with long-term and consistent disease control. These issues may be addressed by the new treatments currently being developed. To date, more studies are needed to address the heterogeneity, quality, and generalizability of the existing data and to evaluate patterns of use, efficacy, and safety of new or emerging therapies for MG.

A Cross-National Comparison of Biosimilars Pricing in Argentina, Australia, Brazil, and Italy.

BACKGROUND: Biosimilar medicines are defined as biological products highly similar to an already licensed biological product (RP). The market entry of biosimilars is expected to reduce the costs of biological treatments. OBJECTIVE: This study aims to evaluate the range of differences between the prices of biosimilars and the corresponding RP for biologicals approved in four countries. METHOD: This is a cross-national comparison of pricing of biosimilars in Argentina, Australia, Brazil, and Italy. The study examined online price databases provided by the national authorities of the investigated countries. Biosimilar price difference was calculated by subtracting the unit price of the biosimilar by the unit price of the RP, and then dividing it by the unit price of the RP. The results were presented as percentage. RESULTS: Brazil had the highest median price reduction (- 36.3%) in biosimilars price, followed by Italy (- 20.0%) and Argentina (- 18.6%). All the biosimilars in Italy were priced below the RP presenting a minimum reduction of 6.3%, while in Australia, most of the prices of biosimilars were equal to the RP. In Argentina, one infliximab-biosimilar displayed price above the RP (40.7%) while the lower priced brand had a reduction of 14.4%. Brazil had four biosimilars with prices above the respective RP, including isophane insulin (1), insulin glargine (1) and somatropin (2). CONCLUSION: The study revealed a marked dispersion in the price's differences between biosimilars and RP across the studied countries. Governments should evaluate whether their policies have been successful in improving affordability of biological therapies.

The Reporting of a Disproportionality Analysis for Drug Safety Signal Detection Using Individual Case Safety Reports in PharmacoVigilance (READUS-PV): Development and Statement.

BACKGROUND AND AIM: Disproportionality analyses using reports of suspected adverse drug reactions are the most commonly used quantitative methods for detecting safety signals in pharmacovigilance. However, their methods and results are generally poorly reported in published articles and existing guidelines do not capture the specific features of disproportionality analyses. We here describe the development of a guideline (REporting of A Disproportionality analysis for drUg Safety signal detection using individual case safety reports in PharmacoVigilance [READUS-PV]) for reporting the results of disproportionality analyses in articles and abstracts. METHODS: We established a group of 34 international experts from universities, the pharmaceutical industry, and regulatory agencies, with expertise in pharmacovigilance, disproportionality analyses, and assessment of safety signals. We followed a three-step process to develop the checklist: (1) an open-text survey to generate a first list of items; (2) an online Delphi method to select and rephrase the most important items; (3) a final online consensus meeting. RESULTS: Among the panel members, 33 experts responded to round 1 and 30 to round 2 of the Delphi and 25 participated to the consensus meeting. Overall, 60 recommendations for the main body of the manuscript and 13 recommendations for the abstracts were retained by participants after the Delphi method. After merging of some items together and the online consensus meeting, the READUS-PV guidelines comprise a checklist of 32 recommendations, in 14 items, for the reporting of disproportionality analyses in the main body text and four items, comprising 12 recommendations, for abstracts. CONCLUSIONS: The READUS-PV guidelines will support authors, editors, peer-reviewers, and users of disproportionality analyses using individual case safety report databases. Adopting these guidelines will lead to more transparent, comprehensive, and accurate reporting and interpretation of disproportionality analyses, facilitating the integration with other sources of evidence.

The REporting of A Disproportionality Analysis for DrUg Safety Signal Detection Using Individual Case Safety Reports in PharmacoVigilance (READUS-PV): Explanation and Elaboration.

In pharmacovigilance, disproportionality analyses based on individual case safety reports are widely used to detect safety signals. Unfortunately, publishing disproportionality analyses lacks specific guidelines, often leading to incomplete and ambiguous reporting, and carries the risk of incorrect conclusions when data are not placed in the correct context. The REporting of A Disproportionality analysis for drUg Safety signal detection using individual case safety reports in PharmacoVigilance (READUS-PV) statement was developed to address this issue by promoting transparent and comprehensive reporting of disproportionality studies. While the statement paper explains in greater detail the procedure followed to develop these guidelines, with this explanation paper we present the 14 items retained for READUS-PV guidelines, together with an in-depth explanation of their rationale and bullet points to illustrate their practical implementation. Our primary objective is to foster the adoption of the READUS-PV guidelines among authors, editors, peer reviewers, and readers of disproportionality analyses. Enhancing transparency, completeness, and accuracy of reporting, as well as proper interpretation of their results, READUS-PV guidelines will ultimately facilitate evidence-based decision making in pharmacovigilance.

An overview of methodological flaws of real-world studies investigating drug safety in the post-marketing setting.

INTRODUCTION: The evaluation of the post-marketing safety profile of drugs is a continuous monitoring process for approved and marketed medicines and it is crucial for detecting new adverse drug reactions. As such, real-world studies are essential to complement pre-marketing evidence with information concerning drug risk-benefit profile and use in wider patient populations and they have a great potential to support post-marketing drug safety evaluations. AREAS COVERED: A detailed description of the main limitations of real-world data sources (i.e. claims databases, electronic healthcare records, drug/disease registers and spontaneous reporting system databases) and of the main methodological challenges of real-world studies in generating real-world evidence is provided. EXPERT OPINION: Real-world evidence biases can be ascribed to both the methodological approach and the specific limitations of the different real-world data sources used to carry out the study. As such, it is crucial to characterize the quality of real-world data, by establishing guidelines and best practices for the assessment of data fitness for purpose. On the other hand, it is important that real-world studies are conducted using a rigorous methodology, aimed at minimizing the risk of bias.

Tixagevimab + cilgavimab against SARS-CoV-2: the preclinical and clinical development and real-world evidence.

INTRODUCTION: Direct-acting SARS-CoV-2 antiviral monoclonal antibodies have been an integral part of therapeutic strategies against COVID-19 pandemic. The monoclonal strategy was jeopardized by the emergence of new variants and resistant strains, making many monoclonal antibodies quickly obsolete. Nevertheless, a possible strategy consists in the use of antibody cocktails and the development of the cilgavimab + tixagevimab in combination is placed in this context. AREAS COVERED: In this review, we describe the development of the cilgavimab + tixagevimab cocktail, from pre-clinical to real-world evidence. EXPERT OPINION: The pre-clinical and clinical development of cilgavimab + tixagevimab followed a similar path to that of the antibodies developed in the earlier stages of the pandemic. Both antibodies have been developed from convalescent plasma and have been shown to be effective in clinical trials in prophylaxis and in early therapy. This cocktail has found its position in therapy especially in immunocompromised subjects for whom vaccine prevention is not feasible. The cocktail strategy, together with a more stable pandemic situation, could ensure a certain longevity to the drug against resistance, especially when compared with that of other antibodies. Recently emerged Omicron sub-lineages have demonstrated the ability to escape this cocktail's activity and so the future of this treatment could be compromised.

Potential missed diagnoses of Crohn's disease in tertiary care: impact on drug utilization and healthcare facilities use.

BACKGROUND: A missed diagnosis of Crohn's disease (CD) can delay treatment initiation with consequences on disease course. AIMS: To measure the possible impact of missed diagnoses on drug utilization and access to healthcare facilities in a real-world cohort of CD patients. METHODS: This retrospective observational study has been conducted on the regional administrative databases of Tuscany (Italy). We included patients with a first record of CD diagnosis between 06/11/2011 and 06/30/2016. Possible missed diagnosis (exposure) was defined by hospital presentation for gastrointestinal symptoms consistent with CD diagnosis that occurred in the 7-60 months preceding CD diagnosis. We compared exposed and non-exposed patients by assessing time-free from biologic drugs and from Emergency Department (ED) or hospital access. Hazard ratio (HR) was calculated using Cox models. RESULTS: Among 3342 CD patients, 584 (17.5%) had a possible missed diagnosis. A risk of being treated with biologic drugs [adjusted HR (aHR): 2.17, 95% CI: 1.75-2.71] and of access to ED or hospitalization (aHR: 1.59, 95% CI: 1.44-1.75) was observed in patients with a possible missed diagnosis as compared to those without. CONCLUSION: Tertiary care caregivers should be trained in the identification of early CD symptoms, to timely identify CD diagnosis and optimize pharmacological treatment and disease management.

Potentially inappropriate drug use in myasthenia gravis: a real-world population-based cohort study in Italy.

Introduction: To evaluate the use of pyridostigmine in presence of contraindications, and the use of concomitant potentially contraindicated drugs in a cohort of patients affected by Myasthenia Gravis (MG) in the Italian Regions of Lazio, Tuscany, and Umbria. Methods: This is a retrospective cohort study. A multivariate logistic regression model was used to evaluate the determinants of pyridostigmine and of potentially contraindicated drugs use in MG patients. Results: Among 591 incident pyridostigmine users affected by MG, 91 (15.4%) had at least one of the contraindications considered at the first prescription of pyridostigmine. Patients prescribed with pyridostigmine in presence of contraindications were more frequently affected by diabetes, obesity, and renal diseases. Age 75+ years (odds ratio, OR 4.94, 95% confidence interval, CI 1.60-15.22 for Latium; OR 3.78, 95%CI: 1.26-11.34 for Tuscany; OR 5.83, 95%CI 1.19-28.52 for Umbria), the presence of at least one specific comorbidity (OR 3.93; 95%CI 1.68-9.17 for Latium), and polytherapy (6+ drugs, OR 4.90, 95%CI: 1.35-17.85 for Tuscany) were found to be significantly associated with pyridostigmine use in presence of contraindications. Among patients affected by MG, 1,483 (62.6%) were treated with potentially contraindicated drugs in the first year of follow-up (67.06.9% in Latium; 59% in Tuscany; 57.6% in Umbria). Patients aged 75+ years, those with at least one specific complication or comorbidity, and those exposed to polytherapy were more likely to be treated with a potential contraindicated drug. Conclusion: Among incident users of pyridostigmine, more than 15% of patients have at least one of the contraindications considered, and among patients diagnosed with MG, in the first year of follow-up >60% of subjects were treated with potentially contraindicated drugs.