Reported Adverse Events in a Multicenter Cohort of Patients Ages 6-18 Years with Cystic Fibrosis and at Least One F508del Allele Receiving Elexacaftor/Tezacaftor/Ivacaftor.

OBJECTIVE: The objective of this study was to describe reported adverse events (AEs) associated with elexacaftor/tezacaftor/ivacaftor (ETI) in a pediatric sample with cystic fibrosis (CF) aged 6-18 years, with at least one F508del variant, followed at multiple Italian CF centers. STUDY DESIGN: This was a retrospective, multicenter, observational study. All children receiving ETI therapy from October 2019 to December 2023 were included. We assessed the prevalence and type of any reported potential drug-related AEs, regardless of discontinuation necessity. Persistent AEs were defined as those continuing at the end of the observation period. RESULTS: Among 608 patients on ETI, 109 (17.9%) reported at least 1 AE. The majority (n = 85, 77.9%) were temporary, with a median duration of 11 days (range 1-441 days). Only 7 (1.1%) patients permanently discontinued treatment, suggesting good overall safety of ETI. The most common AEs leading to discontinuation were transaminase elevations (temporary 14.1%, persistent 25.9%) and urticaria (temporary 41.2%, persistent 7.4%). Creatinine phosphokinase elevation was uncommon. No significant differences in AEs were observed based on sex, age groups (6-11 vs 12-18 years), or genotype. Pre-existing CF-related liver disease was associated with an increased risk of transaminase elevations. We identified significant variability in the percentage of reported AEs (ANOVA P value .026). CONCLUSIONS: This real-world study highlights significant variability in reported AEs. Our findings suggest that ETI is a safe and well-tolerated therapy in children and adolescents with CF. However, further long-term safety and effectiveness investigations are warranted.

Raman Spectroscopy and Cystic Fibrosis Disease: An Alternative Potential Tool for Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Modulator Response Differentiation-A Pilot Study Based on Serum Samples.

Cystic fibrosis (CF) is a genetic disorder that alters chloride transport in mucous membranes. Recent studies have demonstrated that treatment with modulators of the chloride channel reduces inflammatory markers, restoring, among others, the imbalance of lipids. In this study, we analyzed the serum samples of treated and non-treated patients with modulators with Raman spectroscopy. Nineteen (eight treated an eleven non-treated) patients were considered. The main difference between the two groups appeared in the 3020-2800 cm-1 range. A Voigt deconvolution fit was performed, and nine sub-bands were identified. To distinguish between treated and non-treated patients, the area ratio between the CH3 and CH2 vibration modes was calculated for each patient. The results were validated using statistical analyses. In particular, receiver operating characteristic (ROC) curves and Youden index (Y) were calculated (Area Under Curve (AUC): 0.977; Y: 3.30). An ROC curve represents the performance of the classification, illustrating the diagnostic ability of Raman spectroscopy. It was demonstrated that Raman spectroscopy is able to highlight peculiar differences between elexacaftor/tezacaftor/ivacaftor (ETI)-treated and non-treated patients, in relation with lipids biomarkers.

Long-term safety and efficacy of elexacaftor/tezacaftor/ivacaftor in people with cystic fibrosis and at least one F508del allele: 144-week interim results from a 192-week open-label extension study.

BACKGROUND: In two pivotal phase 3 trials, up to 24 weeks of treatment with elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) was efficacious and safe in patients with cystic fibrosis (CF) ≥12 years of age who have at least one F508del allele. The aim of this study is to assess long-term safety and efficacy of ELX/TEZ/IVA in these patients. METHODS: In this phase 3, open-label, single-arm extension study, participants with F508del-minimal function (from a 24-week parent study; n=399) or F508del-F508del (from a 4-week parent study; n=107) genotypes receive ELX/TEZ/IVA at the same dose (ELX 200 mg once daily, TEZ 100 mg once daily and IVA 150 mg every 12 h). The primary end-point is safety and tolerability. A prespecified interim analysis was conducted when the last participant reached the Week 144 visit. RESULTS: At the Week 144 interim analysis, mean duration of exposure to ELX/TEZ/IVA in the extension study was 151.1 weeks. Exposure-adjusted rates of adverse events (AEs) (586.6 events per 100 participant-years) and serious AEs (22.4 events per 100 participant-years) were lower than in the ELX/TEZ/IVA treatment group in the 24-week parent study (1096.0 and 36.9 events per 100 participant-years, respectively); most participants had AEs classified as mild (16.4% of participants) or moderate (60.3% of participants) in severity. 14 participants (2.8%) had AEs that led to treatment discontinuation. Following initiation of ELX/TEZ/IVA, participants had increases in forced expiratory volume in 1 s (FEV1) percentage predicted, Cystic Fibrosis Questionnaire-Revised respiratory domain score and body mass index, and had decreases in sweat chloride concentration and pulmonary exacerbation rates that were maintained over the interim analysis period. The mean annualised rate of change in FEV1 % pred was +0.07 (95% CI -0.12-0.26) percentage points among the participants. CONCLUSIONS: ELX/TEZ/IVA was generally safe and well tolerated, with a safety profile consistent with the 24-week parent study. Participants had sustained improvements in lung function, respiratory symptoms, CF transmembrane conductance regulator function, pulmonary exacerbation rates and nutritional status. These results support the favourable safety profile and durable, disease-modifying clinical benefits of ELX/TEZ/IVA.

The centripetal endoscopic sinus surgery in patients with cystic fibrosis: A preliminary study.

OBJECTIVES: The main aim of this study is to analyze the possible differences between clinical, demographic or genetic characteristics, in Cystic Fibrosis (CF) patients with chronic rhinosinusitis (CRS) with different phenotype. The secondary objective is to describe the possible benefit of surgery with Centripetal Endoscopic Sinus Surgery (CESS). METHODS: The study includes 56 who performed CT scan of the paranasal sinuses. They were divided in 3 group according to phenotype: CRS without Nasal Polyps (NP); CRS with NP; CRS complicated with Mucocele. The clinical symptoms, age, gender, genotype, microbial colonization and pulmonary disease stage were collected and analyzed to assess possible statistically significant differences. Regarding the 7 patients who performed CESS surgery, the number of hospitalizations, intravenous (iv) antibiotic courses, respiratory exacerbations, the FEV1, the Lund-Mackay Score (LMS) and the SNOT 22 were evaluated before and 1 year after surgery. RESULTS: No statistically significant differences regarding clinical symptoms between the 3 groups were identified (p > 0.05). Furthermore, there were no differences in age, gender, genotype, microbial colonization and pulmonary disease stage (p > 0.05). Regarding the patients who performed CESS, no significative difference in FEV1 progression was found. A reduction in hospitalization, pulmonary exacerbation and in the number of iv antibiotic courses resulted statistically significant different (p = 0.004; <0.001 and <0.001 respectively). A significant improvement in SNOT-22 and LMS (p < 0.001) was obtained. CONCLUSION: Radiological monitoring of the rhinosinus disease is necessary regardless of the clinical expression of the disease. The presence of CRS with NP complicated by mucocele is frequent and independent of the patient's age and clinical manifestations. An extensive surgical approach could represent the gold standard for patients with CF in consideration of the potential important advantages to perform a total toilet of all the sinuses and nasal cavities and at the same time eliminating a potential microbiological reservoir.

Vedolizumab-associated pulmonary manifestations in children with ulcerative colitis.

WHAT IS KNOWN AND OBJECTIVE: The off-label use of vedolizumab (VDZ) for inflammatory bowel disease in children is increasing. We report on possibly the first case of VDZ-associated pulmonary manifestations in paediatrics. CASE SUMMARY: This report details the case of a 13-year-old child with ulcerative colitis who was initiated on VDZ due to persistent active disease. After the first three doses, he developed a persistent and productive cough. Microbiological work-up was normal. VDZ discontinuation led to the resolution of symptoms. WHAT IS NEW AND CONCLUSION: To our knowledge, this is the first case report of VDZ-associated pulmonary manifestations in paediatrics. A direct, pro-inflammatory effect of VDZ has been hypothesized, but further studies are warranted.

Malassezia Folliculitis following Triple Therapy for Cystic Fibrosis.

Triple-combination therapy with elexacaftor, tezacaftor and ivacaftor has been recently approved for cystic fibrosis patients with at least one F508del mutation in the transmembrane conductance regulator of the cystic fibrosis gene. Among the adverse events of elexacaftor, tezacaftor and ivacaftor, the cutaneous ones have been rarely reported, mainly dealing with urticarial-like rashes. On this topic, we report two cases of Malassezia folliculitis following triple therapy administration in two young females. In the first patient, a papulopustular rush appeared before the folliculitis while in the second patient it was not preceded by other skin manifestations. The diagnosis was confirmed both by dermoscopy and histology. The prompt response to systemic antimycotic drugs provided further evidence for the causative role of Malassezia, requiring no discontinuation of cystic fibrosis therapy. We could hypothesize that the triple regimen treatment may induce changes in the skin microbiome, potentially able to favor colonization and proliferation of Malassezia species. Physicians should be aware of such associations to allow prompt diagnosis and early interventions, avoiding useless drug removal.

Functional constipation masked as irritable bowel syndrome.

BACKGROUND: Rome IV criteria for functional gastrointestinal disorders state that children suspected of having Irritable Bowel Syndrome (IBS) with Constipation (IBS-C) should be preliminarily treated for constipation. We aimed at verifying if functional constipation may indeed lead to an erroneous diagnosis of IBS with diarrhea (IBS-D) or IBS with mixed pattern of diarrhea and constipation (IBS-M). METHODS: We prospectively enrolled in an unblinded fashion 10 and 16 consecutive children referred to our center who met Rome IV criteria for a diagnosis of IBS-D and IBS-M, respectively. Patients who fulfilled criteria for suspect "occult constipation" were then given a bowel cleaning regimen with Polyethylene glycol 3350, re-evaluated at 2 months and followed up for at least 6 months. Sixteen additional patients with IBS with Constipation (IBS-C) referred in the same period served as control. The endpoints were: 1) a decrease of more than 50% in abdominal pain intensity and frequency scores; and 2) for patients with IBS-D and IBS-M: resolution of diarrhea. RESULTS: The endpoints were met by 8 (80%) and 14 (87%) of the patients with IBS-D and IBS-M, respectively, with decrease of abdominal pain and resolution of "diarrhea". The response was not significantly different from that observed in 15 (93%) of the IBS-C control group. CONCLUSION: Acknowledging the limitations of the small number of patients and of the uncontrolled nature of the study, we suggest that a possibly large number of patients labeled as IBS-D or IBS-M may actually simply present functional constipation and should be managed as such.

Diagnostic Yield of 2 Strategies for Adult Celiac Disease Identification in Primary Care.

GOALS: To compare the diagnostic yield and cost-consequences of 2 strategies, screening regardless of symptoms versus case finding (CF), using a point-of-care test (POCT), for the detection of celiac disease (CD) in primary care, to bridge the diagnostic gap of CD in adults. MATERIALS AND METHODS: All subjects under 75 years of age who consecutively went to their general practitioners' offices were offered POCT for anti-transglutaminase immunoglobulin A antibodies. The POCT was performed on all subjects who agreed, and then a systematic search for symptoms or conditions associated with higher risk for CD was performed, immediately after the test but before knowing the test results. The 2 resulting groups were: (a) POCT positive and (b) symptomatic subject at CF. Subjects were defined as symptomatic at CF in the presence of 1 or more symptoms. All POCT-positive or symptomatic subjects at CF were referred to the CD Centers for confirmation of CD. Data on resource consumption were gathered from patients' charts. Cost of examinations, and diagnostic and laboratory tests were estimated with regional outpatient tariffs (Sicily), and a price of &OV0556;2.5 was used for each POCT. RESULTS: Of a total of 2197 subjects who agreed to participate in the study, 36 (1.6%) and 671 (30.5%) were POCT positive and symptomatic at CF, respectively. The yield from the screening and CF was 5 new celiac patients. The total cost and mean cost for each new CD case were &OV0556;7497.35 and &OV0556;1499.47 for the POCT screening strategy, and &OV0556;9855.14 and &OV0556;1971.03 for the CF strategy, respectively. Assuming consecutive use of both strategies, performing POCT only in symptomatic subjects at CF, the calculated yield would be 4 new diagnoses with a total cost of &OV0556;2345.84 and a mean cost of &OV0556;586.46 for each newly diagnosed patient. Only 1 patient was celiac despite a negative POCT. CONCLUSIONS: Testing symptomatic subjects at CF only by POCT seems the most cost-effective strategy to bridge the diagnostic gap of adult CD in primary care.

Case report on pathogenetic link between gluten and IgA nephropathy.

BACKGROUND: A relationship between IgA nephropathy (IgAN) and celiac disease (CD) has been reported. We show the pathogenetic link for the first time. CASE PRESENTATION: A 39-year-old man with cystic fibrosis (CF) and CF-related diabetes started to present gross hematuria, back pain and headache. At admission, laboratory analysis showed increase in serum creatinine of 1.5 mg/dl, together with hematuria and mild proteinuria (1 g/24 h). He underwent a renal biopsy to investigate the cause of hematuria and renal failure. Biopsy was consistent with IgAN. In view of patient reported dyspepsia, an upper gastrointestinal endoscopy with duodenal biopsies was undertaken and was normal. We looked for mucosal deposits of tTG-2 in the duodenum and the renal mesangium. tTG-2 deposits were found both in the duodenum and in renal biopsies, where they topographically replicated mesangial IgA deposits. After one year on a continued gluten containing diet, the patient developed a Marsh 2 type duodenal pathology. CONCLUSIONS: Our findings suggest a connection between CD and IgAN in terms of an immune-mediated gluten-induced pathogenesis even in the absence of villous atrophy and serum celiac autoantibodies.

C3 glomerulopathy in cystic fibrosis: a case report.

BACKGROUND: C3 glomerulonephritis is a rare glomerulopathy characterized at renal biopsy by C3 deposition, alone or with scanty immunoglobulins, as well as by an electron-dense material in mesangium, subendothelial and subepithelial space. An abnormal systemic activation of the alternative pathway of the complement cascade is responsible for the development of the disease if triggered by several possible environmental conditions. We report the first case in literature of a patient affected by cystic fibrosis and C3GN. CASE PRESENTATION: Our case involves a young woman with cystic fibrosis, who had persistent microscopic hematuria, proteinuria and hypocomplementemia C3 for over three months. Renal biopsy confirmed the diagnosis of C3 glomerulopathy. Complement system dysregulation was tested and resulted in a strong terminal pathway activation proved by high levels of sC5b-9 complex, amounting to 1588 ng/ml (normal value < 400 ng/ml). Next generation sequencing (NGS) showed polymorphism in CFH (p.V62I in SCR1) and THBD (p.A473V), already known as pathogenic for C3GN, as well as a mutation in C3 (p.R102G) associated only with age-related macular degeneration (AMD) so far. Treatment was based on ACE inhibitors and kidney function is currently stable (GFR 50 ml/min, serum creatinine 1.7). CONCLUSIONS: The co-existence of C3 glomerulopathy in a patient with CF, which is characterized by chronic infection/inflammation, makes this case an interesting model of chronic altered systemic activation of the alternative pathway of the complement cascade.

Diagnosis of celiac disease and applicability of ESPGHAN guidelines in Mediterranean countries: a real life prospective study.

BACKGROUND: We assessed how the diagnosis of Celiac Disease (CD) is made and how the new ESPGHAN guidelines can be applied in children from countries with different resources. METHODS: A real life prospective study was performed in 14 centres of 13 different Mediterranean countries. Participants were asked to apply the usual diagnostic work-up for CD according to their diagnostic facilities. RESULTS: There were 1974 patients enrolled in the study, mean age 4 years, 10 months; 865 male, 1109 female. CD was confirmed in 511 (25.9%) and was unconfirmed in 1391 (70.5%) patients; 14 patients were diagnosed as having CD according to the new ESPGHAN guidelines, 43 patients were classified as having potential CD. In all participating countries the diagnosis of CD relied on histology of duodenal biopsy; in 5 countries, HLA, and in one country endomysial antibodies (EMA) were not available. Symptoms did not add a significant increase to the pre-test probability of serological tests. The positive predictive value of tissue transglutaminase type 2 (tTG) antibodies performed with different kits but all corresponding to those recommended by ESPGHAN was 96.1% (95% CI 94-97.9%) in presence of tTG > 10xULN. In 135 patients with tTG >10xULN, HLA genotyping was performed and in all it was compatible with CD. CONCLUSIONS: The results of our study show that CD diagnosis still relies on intestinal biopsy in the Mediterranean area. New ESPGHAN criteria are not applicable in 5 countries due to lack of resources needed to perform HLA genotyping and, in one country, EMA assay. Further simplification of the new ESPGHAN guidelines might be made according to what preliminarily the present results suggest if confirmed by new prospective studies.

Cystic Fibrosis: A Risk Condition for Renal Disease.

OBJECTIVE: Cystic fibrosis (CF) is the most common autosomal recessive disease affecting the Caucasian population, with a birth incidence ranging between 1:2,500 and 1:1,800. It is caused by mutations in the CF transmembrane regulator gene which is localized on 7 chromosomes. Renal disease is reported as a relatively rare complication in adult patient with CF. We evaluated proteinuria and chronic renal failure (CRF) in a population of patients with CF. METHODS: A retrospective study was carried out in a referral center for CF at University of Messina in Italy. We identified all patients with renal disease, characterized by proteinuria and/or CRF, during the period 2007 to 2012 and reviewed their medical records to assess influence on renal disease of genotype, number of pulmonary exacerbation, pancreatic insufficiency, pulmonary function, CF-related diabetes, and antibiotics courses. RESULTS: From a population of 77 adult patients with CF, we identified 9 patients with proteinuria (11.7%), and 11 patients (14.28%) with CRF. Mean age was 35.6 (+5.1 standard deviation) years, 55% were female and 33% had diabetes mellitus. Renal biopsy was performed in 3 patients because of nephrotic syndrome in 1 patient and proteinuria with renal failure in the other 2 patients. Renal amyloidosis was disclosed in 2, whereas IgA nephropathy in 1 patient. The ΔF508 mutation in homozygosis was present in 44% of patients with proteinuria (vs. 27% of our CF population, relative risk 2.07), whereas genotype ΔF508/N1303K in 22%. ΔF508 allele mutation was present in 77.7% of proteinuric patients. CONCLUSIONS: Our study shows a higher prevalence of renal disease in patients with CF, than was previously described. The main reason may be related to increased life expectancy because of better management. Moreover, patients with ΔF508 homozygosis had higher risk of proteinuria.

A point-of-care test for facing the burden of undiagnosed celiac disease in the Mediterranean area: a pragmatic design study.

BACKGROUND: We aimed at assessing the factors that can influence results of the dissemination of an already validated, new generation commercial Point-of-Care Test (POCT) for detecting celiac disease (CD), in the Mediterranean area, when used in settings where it was designed to be administered, especially in countries with poor resources. METHODS: Pragmatic study design. Family pediatricians at their offices in Italy, nurses and pediatricians in Slovenia and Turkey at pediatricians', schools and university primary care centers looked for CD in 3,559 (1-14 yrs), 1,480 (14-23 yrs) and 771 (1-18 yrs) asymptomatic subjects, respectively. A new generation POCT detecting IgA-tissue antitransglutaminase antibodies and IgA deficiency in a finger-tip blood drop was used. Subjects who tested positive and those suspected of having CD were referred to a Celiac Centre to undergo further investigations in order to confirm CD diagnosis. POCT Positive Predictive Value (PPV) at tertiary care (with Negative Predictive Value) and in primary care settings, and POCT and CD rates per thousand in primary care were estimated. RESULTS: At tertiary care setting, PPV of the POCT and 95% CI were 89.5 (81.3-94.3) and 90 (56-98.5) with Negative Predictive Value 98.5 (94.2-99.6) and 98.7% (92-99.8) in children and adults, respectively. In primary care settings of different countries where POCT was performed by a different number of personnel, PPV ranged from 16 to 33% and the CD and POCT rates per thousand ranged from 4.77 to 1.3 and from 31.18 to 2.59, respectively. CONCLUSIONS: Interpretation of POCT results by different personnel may influence the performance of POC but dissemination of POCT is an urgent priority to be implemented among people of countries with limited resources, such as rural populations and school children.

Celiac disease in the Mediterranean area.

BACKGROUND: The World Gastroenterology Organization recommends developing national guidelines for the diagnosis of Celiac Disease (CD): hence a profile of the diagnosis of CD in each country is required. We aim to describe a cross-sectional picture of the clinical features and diagnostic facilities in 16 countries of the Mediterranean basin. Since a new ESPGHAN diagnostic protocol was recently published, our secondary aim is to estimate how many cases in the same area could be identified without a small intestinal biopsy. METHODS: By a stratified cross-sectional retrospective study design, we examined clinical, histological and laboratory data from 749 consecutive unselected CD children diagnosed by national referral centers. RESULTS: The vast majority of cases were diagnosed before the age of 10 (median: 5 years), affected by diarrhea, weight loss and food refusal, as expected. Only 59 cases (7.8%) did not suffer of major complaints. Tissue transglutaminase (tTG) assay was available, but one-third of centers reported financial constraints in the regular purchase of the assay kits. 252 cases (33.6%) showed tTG values over 10 times the local normal limit. Endomysial antibodies and HLA typing were routinely available in only half of the centers. CD was mainly diagnosed from small intestinal biopsy, available in all centers. Based on these data, only 154/749 cases (20.5%) would have qualified for a diagnosis of CD without a small intestinal biopsy, according to the new ESPGHAN protocol. CONCLUSIONS: This cross-sectional study of CD in the Mediterranean referral centers offers a puzzling picture of the capacities to deal with the emerging epidemic of CD in the area, giving a substantive support to the World Gastroenterology Organization guidelines.

The importance of disease prevalence in assessing the diagnostic value of a test: endoscopic markers in celiac disease.

BACKGROUND/AIMS: We evaluated the diagnostic variability and reproducibility of endoscopic signs in two populations with a different pretest likelihood of celiac disease (CD). METHODS: We recruited 289 CD patients (both adults and children) in a multicenter prospective study. Group 1 (high risk) included 111 patients referred for positive serology. Group 2 (low risk) included 178 unselected patients. Mosaic pattern, reduction/loss of Kerckring's folds, scalloping of the valvulae conniventes and a nodular pattern were the endoscopic findings looked for in the duodenum. RESULTS: In group 1, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of endoscopic findings were 100, 84.6, 94.2 and 100% in adults, and 86.8, 9.1, 82.1 and 12.5% in children. In group 2, the sensitivity, specificity, PPV and NPV of endoscopic findings were 33.3, 91.4, 7.7 and 98.5% in adults, and noncalculable, 78.3, 0.0 and 100% in children. Comparing group 1 and group 2, there was a statistically significant difference in sensitivity and PPV in adults, and in specificity, PPV and NPV in children. Concerning the reproducibility of endoscopic findings, a wide variability of κ values was found. CONCLUSION: Endoscopic signs have low reproducibility for CD, and their diagnostic value in selecting patients for multiple intestinal biopsies is unacceptable, especially in populations with low disease prevalence.

A systematic review on gender dysphoria in adolescents and young adults: focus on suicidal and self-harming ideation and behaviours.

INTRODUCTION: Gender dysphoria (GD) is characterized by the incongruence between one's experienced and expressed gender and assigned-sex-at-birth; it is associated with clinically significant distress. In recent years, the number of young patients diagnosed with GD has increased considerably. Recent studies reported that GD adolescents present behavioural and emotional problems and internalizing problems. Furthermore, this population shows a prevalence of psychiatric symptoms, like depression and anxiety. Several studies showed high rates of suicidal and non-suicidal self-injurious thoughts and behaviour in GD adolescents. To increase understanding of overall mental health status and potential risks of young people with GD, this systematic review focused on risk of suicide and self-harm gestures. METHODS: We followed the PRISMA 2020 statement, collecting empirical studies from four electronic databases, i.e., PubMed, Scopus, PsycINFO, and Web of Science. RESULTS: Twenty-one studies on GD and gender nonconforming identity, suicidality, and self-harm in adolescents and young adults met inclusion criteria. Results showed that GD adolescents have more suicidal ideation, life-threatening behaviour, self-injurious thoughts or self-harm than their cisgender peers. Assessment methods were heterogeneous. CONCLUSION: A standardised assessment is needed. Understanding the mental health status of transgender young people could help develop and provide effective clinical pathways and interventions.

Rescue by elexacaftor-tezacaftor-ivacaftor of the G1244E cystic fibrosis mutation's stability and gating defects are dependent on cell background.

BACKGROUND: Cystic fibrosis is caused by mutations impairing expression, trafficking, stability and/or activity of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. The G1244E mutation causes a severe gating defect that it is not completely rescued by ivacaftor but requires the use of a second compound (a co-potentiator). Recently, it has been proposed that the corrector elexacaftor may act also as a co-potentiator. METHODS: By using molecular, biochemical and functional analyses we performed an in-depth characterization of the G1244E-CFTR mutant in heterologous and native cell models. RESULTS: Our studies demonstrate that processing and function of the mutant protein, as well as its pharmacological sensitivity, are markedly dependent on cell background. In heterologous expression systems, elexacaftor mainly acted on G1244E-CFTR as a co-potentiator, thus ameliorating the gating defect. On the contrary, in the native nasal epithelial cell model, elexacaftor did not act as a co-potentiator, but it increased mature CFTR expression possibly by improving mutant's defective stability at the plasma membrane. CONCLUSIONS: Our study highlights the importance of the cell background in the evaluation of CFTR modulator effects. Further, our results draw attention to the need for the development of novel potentiators having different mechanisms with respect to ivacaftor to improve channel activity for mutants with severe gating defect.