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Background: Sweat chloride (SC) concentrations in people with cystic fibrosis (PwCF) reflect relative CF transmembrane conductance regulator (CFTR) protein function, the primary CF defect. Populations with greater SC concentrations tend to have lesser CFTR function and more severe disease courses. CFTR modulator treatment can improve CFTR function within specific CF genotypes and is commonly associated with reduced SC concentration. However, SC concentrations do not necessarily fall to concentrations seen in the unaffected population, suggesting potential for better CFTR treatment outcomes. We characterized post-modulator SC concentration variability among CHEC-SC study participants by genotype and modulator., Methods: PwCF receiving commercially approved modulators for ≥90 days were enrolled for a single SC measurement. Clinical data were obtained from chart review and the CF Foundation Patient Registry (CFFPR). Variability of post-modulator SC concentrations was assessed by cumulative SC concentration frequencies., Results: Post-modulator SC concentrations (n = 3787) were collected from 3131 PwCF; most (n = 1769, 47 %) were collected after elexacaftor/tezacaftor/ivacaftor (ETI) treatment. Modulator use was associated with lower SC distributions, with post-ETI concentrations the lowest on average. Most post-ETI SC concentrations were <60 mmol/L (79 %); 26 % were <30 mmol/L. Post-ETI distributions varied by genotype. All genotypes containing at least one F508del allele had individuals with post-ETI SC ≥60 mmol/L, with the largest proportion being F508del/minimal function (31 %)., Conclusions: Post-modulator SC concentration heterogeneity was observed among all genotypes and modulators, including ETI. The presence of PwCF with post-modulator SC concentrations within the CF diagnostic range suggests room for additional treatment-associated CFTR restoration in this population., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

Rationale: Pulmonary exacerbations (PEx) remain the most common cause of morbidity, recurrent hospitalization, and diminished survival in people with cystic fibrosis (PWCF) and are characterized by excess inflammation. Corticosteroids are potent, widely available antiinflammatory drugs. However, corticosteroid efficacy data from randomized controlled trials in PWCF are limited. Objectives: To determine whether adjunctive systemic corticosteroid therapy is associated with improved outcomes in acute CF PEx. Methods: We performed a secondary analysis of Standardized Treatment of Pulmonary Exacerbations 2 (STOP2), a large multicenter randomized controlled trial of antimicrobial treatment durations for adult PWCF presenting with PEx, that included the use of corticosteroids as a stratification criterion in its randomization protocol. Corticosteroid treatment effects were determined after propensity score matching for covariates including age, sex, baseline forced expiratory volume in 1 second (FEV 1 ), genotype, and randomization arm. The primary outcome measure was the change in percentage predicted FEV 1 (ppFEV 1 ). Symptoms, time to next PEx, and the incidence of adverse events (AEs) and serious adverse events (SAEs) were assessed as secondary endpoints. Phenotypic factors associated with the clinical decision to prescribe steroids were also investigated. Results: Corticosteroids were prescribed for 168 of 982 PEx events in STOP2 (17%). Steroid prescription was associated with decreased baseline ppFEV 1 , increased age, and female sex. Cotreatment with corticosteroids was independent of treatment arm allocation and did not result in greater mean ppFEV 1 response, longer median time to next PEx, or more substantial symptomatic improvement compared with propensity-matched PWCF receiving antibiotics alone. AEs were not increased in corticosteroid-treated PWCF. The total number of SAEs-but not the number of corticosteroid-related or PEx-related SAEs-was higher among patients receiving corticosteroids. Conclusions: Empiric, physician-directed treatment with systemic corticosteroids, although common, is not associated with improved clinical outcomes in PWCF receiving antibiotics for PEx. Clinical trial registered with www.clinicaltrials.gov (NCT02781610).

Background: Pulmonary exacerbations (PEx) remain a major cause of morbidity and mortality in people with cystic fibrosis (PWCF). Although the combination cystic fibrosis transmembrane conductance regulator (CFTR) modulators lumacaftor/ivacaftor and tezacaftor/ivacaftor have been shown to reduce PEx frequency, their influence on clinical and biochemical responses to acute PEx treatment is unknown., Methods: We performed a secondary analysis of STOP2, a large multicenter randomized controlled trial of antimicrobial treatment durations for adult PWCF presenting with PEx. Propensity score matching was used to compare outcomes in antibiotic-treated F508del/F508del PWCF receiving lumacaftor/ivacaftor or tezacaftor/ivacaftor with those observed in antibiotic-treated F508del/F508del controls not receiving CFTR modulator therapy. The primary outcome measure was the change in percent predicted FEV 1 (ppFEV 1 ) following completion of intravenous (IV) antibiotics, with post-antibiotic changes in symptoms, serum C-reactive protein (CRP) concentrations and weight included as secondary endpoints., Results: Among 982 PEx events in randomized PWCF, 480 were homozygous for F508del, of whom 289 were receiving lumacaftor/ivacaftor or tezacaftor/ivacaftor at initiation of antibiotic therapy. Modulator-treated F508del/F508del PWCF did not demonstrate greater improvements in ppFEV 1 , symptoms, serum CRP or weight following antibiotic treatment compared to modulator-naïve controls matched for age, sex, baseline ppFEV 1 , genotype, body mass index, initial CRP, initial symptoms, exacerbation history, diabetic status, randomization arm and concomitant medical therapy., Conclusion: In the acute setting, CFTR modulator therapy with lumacaftor/ivacaftor or tezacaftor/ivacaftor does not convey additional clinical or biochemical advantage above standardized PEx treatment in F508del/F508del PWCF., Competing Interests: Declaration of Competing Interest O.J.McE. has been an investigator for Chiesi and Grifols. P.A.F. has been an investigator for Novartis, Novoteris, Proteostasis, Savara, Sound, Chiesi and Vertex. C.H.G. has been an investigator for Boehringer Ingelheim and a DSMB chair for Novartis. The remaining authors have no relevant or competing interests to disclose., (Copyright © 2023. Published by Elsevier B.V.)

Objective: To assess the feasibility of enrolling people with CF (pwCF) taking the CFTR modulator elexacaftor/tezacaftor/ivacaftor (ETI) in clinical trials of a new modulator., Methods: PwCF receiving ETI at CHEC-SC study (NCT03350828) enrollment were surveyed for interest in 2-week to 6-month placebo- (PC) and active-comparator (AC) modulator studies. Those taking inhaled antimicrobials (inhABX) were surveyed for interest in PC inhABX studies., Results: Of 1791 respondents, 75% [95% CI 73, 77] would enroll in a 2-week PC modulator study versus 51% [49, 54] for a 6-month study; 82% [81, 84] and 63% [61, 65] would enroll in 2-week and 6 month AC studies; 77% [74, 80] of 551 taking inhABX would enroll in a 2-week PC inhABX study versus 59% [55, 63] for a 6-month study. Previous clinical trial experience increased willingness., Conclusions: Study designs will affect feasibility of future clinical trials of new modulators and inhABX in people receiving ETI., Competing Interests: Declaration of Competing Interest The authors have no competing or conflicting interests to report., (Copyright © 2023. Published by Elsevier B.V.)

Background: Reducing treatment burden is a priority for people with cystic fibrosis, whose health has benefited from using new modulators that substantially increase CFTR protein function. The SIMPLIFY study aimed to assess the effects of discontinuing nebulised hypertonic saline or dornase alfa in individuals using the CFTR modulator elexacaftor plus tezacaftor plus ivacaftor (ETI)., Methods: The SIMPLIFY study included two parallel, multicentre, open-label, randomised, controlled, non-inferiority trials at 80 participating clinics across the USA in the Cystic Fibrosis Therapeutics Development Network. We included individuals with cystic fibrosis aged 12-17 years with percent predicted FEV 1 (ppFEV 1 ) of 70% or more, or those aged 18 years or older with ppFEV 1 of 60% or more, if they had been taking ETI and either (or both) mucoactive therapies (≥3% hypertonic saline or dornase alfa) for at least 90 days before screening. Participants on both hypertonic saline and dornase alfa were randomly assigned to one of the two trials, and those on a single therapy were assigned to the applicable trial. All participants were then randomly assigned 1:1 to continue or discontinue therapy for 6 weeks using permuted blocks of varying size, stratified by baseline ppFEV 1 (week 0; ≥90% or <90%), single or concurrent use of hypertonic saline and dornase alfa, previous SIMPLIFY study participation (yes or no), and age (≥18 or <18 years). For participants randomly assigned to continue their therapy during a given trial, this therapy was instructed to be taken at least once daily according to each participant's pre-existing, clinically prescribed regimen. Hypertonic saline concentration was required to be at least 3%. The primary objective for each trial was to determine whether discontinuing was non-inferior to continuing, measured by the 6-week change in ppFEV 1 in the per-protocol population. We established a non-inferiority margin of -3% for the difference between groups in the 6-week change in ppFEV 1 . Safety outcomes were analysed in the intention-to-treat population. This study is registered with ClinicalTrials.gov, NCT04378153., Findings: From Aug 25, 2020, to May 25, 2022, a total of 672 unique participants were screened for eligibility for one or both trials, resulting in 847 total random assignments across both trials with 594 unique participants. 370 participants were randomly assigned in the hypertonic saline trial and 477 in the dornase alfa trial. Participants across both trials had an average ppFEV 1 of 96·9%. Discontinuing treatment was non-inferior to continuing treatment with respect to the absolute 6-week change in ppFEV 1 in both the hypertonic saline trial (-0·19% [95% CI -0·85 to 0·48] in the discontinuation group [n=133] vs 0·14% [-0·51 to 0·78] in the continuation group [n=140]; between-group difference -0·32% [-1·25 to 0·60]) and dornase alfa trial (0·18% [-0·38 to 0·74] in the discontinuation group [n=199] vs -0·16% [-0·73 to 0·41] in the continuation group [n=193]; between-group difference 0·35% [-0·45 to 1·14]), with consistent results in the intention-to-treat populations. In the hypertonic saline trial, 64 (35%) of 184 in the discontinuation group versus 44 (24%) of 186 participants in the continuation group and, in the dornase alfa trial, 89 (37%) of 240 in the discontinuation group versus 55 (23%) of 237 in the continuation group had at least one adverse event., Interpretation: In individuals with cystic fibrosis on ETI with relatively well preserved pulmonary function, discontinuing daily hypertonic saline or dornase alfa for 6 weeks did not result in clinically meaningful differences in pulmonary function when compared with continuing treatment., Competing Interests: Declaration of interests GR-B reports grants and contracts from Vertex Pharmaceuticals and the Cystic Fibrosis Foundation (CFF). SHD reports contracts from AstraZeneca, Calithera, CFF, US National Institutes of Health (NIH), Vertex Pharmaceuticals; consulting fees from Polarean, 501 Ventures, and Chiesi USA; fees for advisory boards for Enterprise Therapeutics and Gilead Sciences; and participation on a data safety monitoring board (DSMB) for Abbvie and Boehringer Ingleheim. JLT-C reports grants and contracts from CFF, Vertex Pharmaceutics, Eloxx, and 4DMT; consulting fees from Vertex Phamaceuticals, Insmed, and 4DMT; participation on a DSMB for Abbvie; and serving on an advisory board for CFF, American Thoracic Society (ATS), Journal of Cystic Fibrosis, and Emily's Entourage. KAR reports grants from CFF; royalties from Springer Publishing; honoraria from Vertex Pharmaceuticals; and serving on an advisory board for ATS. AB reports grants from the CFF for Therapeutics Development Network (TDN) studies. FR reports grants from Vertex Phamaceuticals and consulting fees from Vertex Phamaceuticals, Proteostasis, Translate Bio, Boehringer Ingelheim, and Calithera. JKY reports grants from CFF. SM reports grants from CFF to support TDN studies. DPN reports grants from CFF and NIH; consulting fees from BiomX, Clarametyx, Genentech, GlaxoSmithKline, Nabriva, Respirion, and Vertex Pharmaceuticals; and advisory board membership for CFF and Kither Biotechnology. DR reports grants and contracts from CFF and Vertex Pharmaceuticals. AHG reports grants and contracts from CFF, Insmed, AbbVie, and 4D Molecular Therapeutics. GSS reports advisory board participation for Vertex Pharmaceuticals and Gilead Sciences. CHG reports grants and contracts from CFF, NIH, and the US Food and Drug Administration; consulting fees from Enterprise Therapeutics; and honoraria from Gilead Sciences, Novartis, Boehringer Ingelheim, Vertex Phamaceuticals, and stock options in Aer Therapeutics. JPC reports employment at the CFF. NM-H reports grants from CFF, NIH, and US Food and Drug Administration; consulting fees from Enterprise Therapeutics; and DSMB membership for the NIH. BPO, KO-D, AHG, GO, CA, RR, and KM declare no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Background: CHEC-SC is an ongoing epidemiologic study characterizing modulator-induced sweat chloride (SC) responses across the CF population, with interim results available prior to the availability of triple combination modulator therapy., Methods: Eligible participants had been prescribed a modulator for ≥90 days with re-enrollment allowed upon establishment of a new modulator. Pre-modulator SC values were obtained from chart review; post-modulator sweat was collected and analyzed locally. SC changes were descriptively summarized with biologic sex effects adjusted for age, weight, and CFTR genotype. Heterogeneity in ivacaftor SC response was characterized in relation to published CFTR functional responses., Results: 1848 participants provided 2004 SC measurements, 26.2% on ivacaftor, 39.1% on lumacaftor/ivacaftor, and 34.7% on tezacaftor/ivacaftor. Average SC changes for all modulators were consistent with those reported in previous clinical studies, with greater variation in SC response observed among rarer mutations and notable shifts in the proportion with SC <60mmol/L independent of the magnitude of SC change. Ivacaftor induced in vitro CFTR functional change was significantly correlated with ivacaftor-modulated SC response (Pearson correlation= ‒0.52, 95% CI: ‒0.773, ‒0.129). Average SC change from ivacaftor to tezacaftor/ivacaftor was ‒4.9 mmol/L (n=17,95% CI:‒9.3, ‒0.5) and differed from those switching from lumacaftor/ivacaftor (10.0 mmol/L, n=139, 95% CI:7.8,12.3). Sex at birth was not associated with SC response., Conclusions: CHEC-SC is the largest study characterizing modulator-induced SC changes across the CF population. There was a strong association between ivacaftor induced in vitro CFTR function and SC response across a genotypically heterogenous cohort. Biological sex was not associated with SC response., Competing Interests: Conflict of Interest Statement NMH serves as a consultant through her institution in her role as Executive Director of the CF Therapeutics Development Network Coordinating Center (CF TDNCC) and has received personal consulting fees from Vertex Pharmaceuticals. She has received grant funding from the Cystic Fibrosis Foundation (CFF) and National Institutes of Health (NIH). DRV has received personal consulting fees from AbbVie, Albumedix, AN2, Aradigm, Armata, Arrevus, Calithera, Chiesi USA, Cipla, Corbus, CFF, Eloxx, Enbiotix, Eveo, Galephar, Horizon, IBF, ICON clinical sciences, Ionis, Kala, Merck, Microbion, NDA, Protalix, PTC, Pulmocide, Recida, Savara, Vast, and VRTX. MWK has received personal consulting fees for advisory board participation, grant support to his institution for clinical trial participation, and non-financial support from VRTX, Savara, Laurent, Corbus Pharmaceuticals, PTC, and AzurRx. He has received personal consulting fees and non-financial support from Chiesi, Celtaxsys, Merck, and Kala. Personal consulting fees were received from Albumedix, Paranta, Protalix, Santhera, pH Pharma, Novartis, Ionis, the Italian Cystic Fibrosis Foundation, and the Food and Drug Administration. SMR reports grants and personal fees from Vertex Pharmaceuticals Inc, during the conduct of the study; grants and personal fees from Novartis, grants and personal fees from Bayer, grants from Translate Bio, grants and non-financial support from Proteostasis, grants, personal fees and non-financial support from Galapagos/Abbvie, grants, personal fees and non-financial support from Synedgen/Synspira, grants from Eloxx, grants from Celtaxsys, grants, personal fees and non-financial support from Vertex Pharmaceuticals Inc, personal fees and non-financial support from Renovion, grants and personal fees from Arrowhead, grants, personal fees and non-financial support from Ionis, grants from Astra Zenica, personal fees from Cystetic Medicines, outside the submitted work. ETZ reports grants and personal consulting fees from Vertex Pharmaceuticals and the Cystic Fibrosis Foundation during the conduct of the study., (Copyright © 2022. Published by Elsevier B.V.)

Background: The Characterizing CFTR Modulated Changes in Sweat Chloride and their Association with Clinical Outcomes (CHEC-SC) study is a large epidemiologic study designed to determine the relationship between sweat chloride response and clinical outcomes in people with cystic fibrosis (CF) on commercially approved CFTR modulators. A challenge to study feasibility was capturing sweat chloride measurements before modulator initiation. We tested the hypothesis that historic sweat chloride approximated contemporary pre-modulator values to estimate CFTR modulator-induced changes, allowing a single-visit study design., Methods: GOAL and PROSPECT were multi-center prospective studies of individuals initiating ivacaftor or lumacaftor-ivacaftor. At enrollment, pre-modulator sweat chloride was measured and historic results recorded. Post-modulator sweat chloride was measured at 1, 3 and 6 months. For this analysis, differences between historic and pre-modulator sweat chloride were estimated. CFTR modulator-induced sweat chloride mean changes were compared using historic and pre-modulator sweat chloride., Results: Paired historic and pre-modulator sweat chloride (n=406 participants) revealed a non-significant mean change of -1.0 mmol/L (95% CI: -2.71, 0.66) over an average of 17.2 years. Calculating sweat response to ivacaftor or lumacaftor-ivacaftor using historic or pre-modulator values resulted in similar estimates of modulator response. Based on these results, the CHEC-SC study was designed with a single, post-modulator sweat chloride measurement., Conclusions: Historic sweat chloride values provide a reliable estimate of pre-modulator sweat chloride for people starting on modulator therapy. The CHEC-SC study anticipates capturing approximately 5,000 sweat chloride values, providing an unprecedented understanding of sweat chloride across the CF population in the era of CFTR modulators., Competing Interests: Declaration of Competing Interest ETZ, NMH, DRV, SMR, MWK: grants or consulting CFF; DRV consults for aMoon, Arrevus, Eloxx, Enbiotix, Felix, Ionis, Matinas, Merck, Polyphor, Respirion, Savara; SMR consults for Vertex; MWK consults for Anthera, AzurRx, Celtaxsys, Chiesi, Ionis, Kala, Laurent, Merck, Paranta, pH Pharma, Santhera, Vertex; JPC, KOD and MS: none., (Copyright © 2021. Published by Elsevier B.V.)

The care for individuals with cystic fibrosis (CF) with at least one F508del mutation will greatly change as a result of the unparalleled clinical benefits observed with the new triple-combination CFTR (CF transmembrane regulator)-modulator therapy elexacaftor/tezacaftor/ivacaftor (ETI). Incorporating ETI into the standard of care creates new motivation and opportunity to consider reductions in overall treatment burden and evaluate whether other chronic medications can now be safely discontinued without loss of clinical benefit. SIMPLIFY is a master protocol poised to test the impact of discontinuing versus continuing two commonly used chronic therapies in people with CF who are at least 12 years of age or older and stable on ETI therapy. The protocol is composed of two concurrent randomized controlled trials designed to evaluate the independent short-term effects of discontinuing hypertonic saline or dornase alfa, enabling individuals on both therapies to participate in one or both trials. The primary objective for each trial is to determine whether discontinuing treatment is noninferior to continuing treatment after establishment of ETI, as measured by the 6-week absolute change in the percent-predicted forced expiratory volume in 1 second. Developing this study required a balance between ideal study-design principles and feasibility. SIMPLIFY will be the largest multicenter, randomized, controlled medication-withdrawal study in CF. This study is uniquely positioned to provide timely evidence on whether the daily treatment burden can be reduced among individuals on CFTR-modulator therapy. Clinical trial registered with www.clinicaltrials.gov (NCT04378153).

Rationale: Chronic azithromycin is commonly used in cystic fibrosis based on short controlled clinical trials showing reductions in pulmonary exacerbations and improved FEV 1 . Long-term effects are unknown. Objectives: Examine pulmonary outcomes among chronic azithromycin users compared with matched controls over years of use and consider combined azithromycin use in cohorts using chronic inhaled tobramycin or aztreonam. Methods: This retrospective cohort study used the U.S. cystic fibrosis Foundation Patient Registry. Incident chronic azithromycin users were compared with matched controls by FEV 1 % predicted rate of decline and rates of intravenous antibiotic use to treat pulmonary exacerbations. Propensity score methods were utilized to address confounding by indication. Predefined sensitivity analyses based on lung function, Pseudomonas aeruginosa (PA) status, and follow-up time intervals were conducted. Measurements and Main Results: Across 3 years, FEV 1 % predicted per-year decline was nearly 40% less in those with PA using azithromycin compared with matched controls (slopes, -1.53 versus -2.41% predicted per yr; difference: 0.88; 95% confidence interval [CI], 0.30-1.47). This rate of decline did not differ based on azithromycin use in those without PA. Among all cohorts, use of intravenous antibiotics was no different between azithromycin users and controls. Users of inhaled tobramycin and azithromycin had FEV 1 % predicted per-year decline of -0.16 versus nonusers (95% CI, -0.44 to 0.13), whereas users of inhaled aztreonam lysine and azithromycin experienced a mean 0.49% predicted per year slower decline than matched controls (95% CI, -0.11 to 1.10). Conclusions: Results from this study provide additional rationale for chronic azithromycin use in PA-positive patients to reduce lung function decline.