Longitudinal improvements in clinical and functional outcomes following initiation of elexacaftor/tezacaftor/ivacaftor in patients with cystic fibrosis.

Background: Use of elexacaftor/tezacaftor/ivacaftor (ETI) for treatment of cystic fibrosis (CF) has resulted in unprecedented clinical improvements necessitating development of outcome measures for monitoring disease course. Intranasal micro-optical coherence tomography (µOCT) has previously helped detect and characterize mucociliary abnormalities in patients with CF. This study was done to determine if µOCT can define the effects of ETI on nasal mucociliary clearance and monitor changes conferred to understand mechanistic effects of CFTR modulators beyond CFTR activation. Methods: 26 subjects, with at least 1 F508del mutation were recruited and followed at baseline (visit 1), +1 month (visit 2) and +6 months (visit 4) following initiation of ETI therapy. Clinical outcomes were computed at visits 1, 2 and 4. Intranasal µOCT imaging and functional metrics analysis including mucociliary transport rate (MCT) estimation were done at visits 1 and 2. Results: Percent predicted forced expiratory volume in 1 s (ppFEV1) showed a significant increase of +10.9 % at visit 2, which sustained at visit 4 (+10.6 %). Sweat chloride levels significantly decreased by -36.6 mmol/L and -41.3 mmol/L at visits 2 and 4, respectively. µOCT analysis revealed significant improvement in MCT rate (2.8 ± 1.5, visit 1 vs 4.0 ± 1.5 mm/min, visit 2; P = 0.048). Conclusions: Treatment with ETI resulted in significant and sustained clinical improvements over 6 months. Functional improvements in MCT rate were evident within a month after initiation of ETI therapy indicating that µOCT imaging is sensitive to the treatment effect of HEMT and suggests improved mucociliary transport as a probable mechanism of action underlying the clinical benefits.

COVID-19 Causes Ciliary Dysfunction as Demonstrated by Human Intranasal Micro-Optical Coherence Tomography Imaging.

Severe acute respiratory syndrome coronavirus (SARS-CoV-2), causative agent of coronavirus disease 2019 (COVID-19), binds via ACE2 receptors, highly expressed in ciliated cells of the nasal epithelium. Micro-optical coherence tomography (µOCT) is a minimally invasive intranasal imaging technique that can determine cellular and functional dynamics of respiratory epithelia at 1-µm resolution, enabling real time visualization and quantification of epithelial anatomy, ciliary motion, and mucus transport. We hypothesized that respiratory epithelial cell dysfunction in COVID-19 will manifest as reduced ciliated cell function and mucociliary abnormalities, features readily visualized by µOCT. Symptomatic outpatients with SARS-CoV-2 aged ≥ 18 years were recruited within 14 days of symptom onset. Data was interpreted for subjects with COVID-19 (n=13) in comparison to healthy controls (n=8). Significant reduction in functional cilia, diminished ciliary beat frequency, and abnormal ciliary activity were evident. Other abnormalities included denuded epithelium, presence of mucus rafts, and increased inflammatory cells. Our results indicate that subjects with mild but symptomatic COVID-19 exhibit functional abnormalities of the respiratory mucosa underscoring the importance of mucociliary health in viral illness and disease transmission. Ciliary imaging enables investigation of early pathogenic mechanisms of COVID-19 and may be useful for evaluating disease progression and therapeutic response.

Ataluren/ivacaftor combination therapy: Two N-of-1 trials in cystic fibrosis patients with nonsense mutations.

Premature termination codons (PTCs) in cystic fibrosis transmembrane conductance regulator (CFTR) produce nonfunctional protein. No approved therapies exist for PTC mutations, including W1282X. We hypothesized that ivacaftor, combined with readthrough therapy, may benefit W1282X patients. Two N-of-1 clinical trials were conducted with ataluren and ivacaftor in various combinations. No meaningful clinical benefit was observed in either patient with ivacaftor alone or ataluren/ivacaftor combination. However, isolated improvements of uncertain significance were noted by a nasal potential difference (NPD) and FEV1 % with ivacaftor in Patient-1 and with ataluren/ivacaftor combination by NPD and body mass index in Patient-2. Drug regimen composed of readthrough agents and potentiators warrant further development for W1282X and other CFTR nonsense mutations.

A glycopolymer improves vascoelasticity and mucociliary transport of abnormal cystic fibrosis mucus.

Cystic fibrosis (CF) is characterized by increased mucus viscosity and delayed mucociliary clearance that contributes to progressive decline of lung function. Mucus in the respiratory and GI tract is excessively adhesive in the presence of airway dehydration and excess extracellular Ca2+ upon mucin release, promoting hyperviscous, densely packed mucins characteristic of CF. Therapies that target mucins directly through ionic interactions remain unexploited. Here we show that poly (acetyl, arginyl) glucosamine (PAAG), a polycationic biopolymer suitable for human use, interacts directly with mucins in a Ca2+-sensitive manner to reduce CF mucus viscoelasticity and improve its transport. Notably, PAAG induced a linear structure of purified MUC5B and altered its sedimentation profile and viscosity, indicative of proper mucin expansion. In vivo, PAAG nebulization improved mucociliary transport in CF rats with delayed mucus clearance, and cleared mucus plugging in CF ferrets. This study demonstrates the potential use of a synthetic glycopolymer PAAG as a molecular agent that could benefit patients with a broad array of mucus diseases.

Ivacaftor improves rhinologic, psychologic, and sleep-related quality of life in G551D cystic fibrosis patients.

BACKGROUND: Ivacaftor is a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator that improves pulmonary function in cystic fibrosis (CF) patients with at least 1 copy of the G551D CFTR mutation. The purpose of this study is to evaluate the impact of ivacaftor on chronic rhinosinusitis (CRS) symptoms in this population. METHODS: The G551D Observational (GOAL) study was a multicenter prospective cohort study enrolling CF patients ≥6 years with at least 1 G551D mutation. Subjects were provided 20-item Sino-Nasal Outcome Test (SNOT-20) questionnaires prior to ivacaftor therapy and at 1, 3, and 6 months afterward. The impact on rhinologic (R), psychological (P), sleep (S), and ear/facial (E) quality of life (QOL) domains was evaluated separately. RESULTS: Of 153 subjects, 129 (84%) completed all questionnaires. Typical baseline symptom burden was low (75% with scores <1) and degree of improvement (ie, reduced scores) was greater with higher baseline scores. SNOT-20 decreased, reflecting improvement, at all follow-up intervals (1 month: [mean change ± standard deviation] -0.25 ± 0.53, p < 0.01; 3 months; -0.29 ± 0.58, p < 0.01; 6 months: -0.21 ± 0.58, p = 0.02), but less than the prespecified minimal clinically important difference (0.8). Significant improvement was observed at 1, 3, and 6 months in the R domain (1 month: -0.24, p < 0.01; 3 months: -0.34, p < 0.01; 6 months: -0.25, p < 0.01) and P domain (1 month: -0.25, p < 0.01; 3 months: -0.32, p < 0.01; 6 months: -0.26, p < 0.01), and 1 and 3 months in the S domain (1 months: -0.35, p < 0.01; 3 months: -0.32, p < 0.01; 6 months: -0.18, p = 0.07). There was no improvement in the E domain at any time point. CONCLUSION: Ivacaftor improves QOL in the R, P, and S domains in G551D CF patients, although QOL instruments validated for CRS may not translate well to CF CRS patients because symptom burden was surprisingly low.

Optimizing nasal potential difference analysis for CFTR modulator development: assessment of ivacaftor in CF subjects with the G551D-CFTR mutation.

Nasal potential difference (NPD) is used as a biomarker of the cystic fibrosis transmembrane conductance regulator (CFTR) and epithelial sodium channel (ENaC) activity. We evaluated methods to detect changes in chloride and sodium transport by NPD based on a secondary analysis of a Phase II CFTR-modulator study. Thirty-nine subjects with CF who also had the G551D-CFTR mutation were randomized to receive ivacaftor (Kalydeco™; also known as VX-770) in four doses or placebo twice daily for at least 14 days. All data were analyzed by a single investigator who was blinded to treatment assignment. We compared three analysis methods to determine the best approach to quantify changes in chloride and sodium transport: (1) the average of both nostrils; (2) the most-polarized nostril at each visit; and (3) the most-polarized nostril at screening carried forward. Parameters of ion transport included the PD change with zero chloride plus isoproterenol (CFTR activity), the basal PD, Ringer's PD, and change in PD with amiloride (measurements of ENaC activity), and the delta NPD (measuring CFTR and ENaC activity). The average and most-polarized nostril at each visit were most sensitive to changes in chloride and sodium transport, whereas the most-polarized nostril at screening carried forward was less discriminatory. Based on our findings, NPD studies should assess both nostrils rather than a single nostril. We also found that changes in CFTR activity were more readily detected than changes in ENaC activity, and that rigorous standardization was associated with relatively good within-subject reproducibility in placebo-treated subjects (± 2.8 mV). Therefore, we have confirmed an assay of reasonable reproducibility for detecting chloride-transport improvements in response to CFTR modulation.

Reduced sodium transport with nasal administration of the prostasin inhibitor camostat in subjects with cystic fibrosis.

BACKGROUND: Prostasin, a trypsin-like serine protease, is a channel-activating protease and major regulator of epithelial sodium channel-mediated sodium absorption. Its direct inhibition by camostat represents a potential approach to inhibiting sodium transport in cystic fibrosis (CF). METHODS: To determine whether a topical formulation of camostat represents an efficacious and tolerable approach to reducing Na+ transport in the CF airway, we conducted a two-part randomized, double-blind, placebo-controlled, crossover, ascending single-dose study to evaluate the pharmacodynamics, safety, and pharmacokinetics of camostat administered through a nasal spray pump in subjects with CF. Nasal potential difference (PD) was measured before and after treatment, and safety and pharmacokinetics were assessed by a standardized approach. RESULTS: In part 1, nine subjects were enrolled, and six completed crossover dosing at the maximally tolerated dose. The change in maximal (most polarizing) basal PD 2 h following administration of camostat was +13.1 mV (1.6-mg dose group) compared with -8.6 mV following placebo (P<.005). Intrasubject change in Ringer and amiloride-sensitive PDs exhibited similar and consistent responses. Bayesian analysis in an additional six subjects in part 2 estimated a dose of 18 µg/mL to provide 50% of the maximum effect. There was no significant change in chloride transport or total nasal symptom score, nasal examination rating, and laboratory parameters. CONCLUSIONS: This study establishes the proof of concept that a reduction in sodium transport in the human CF airway can be achieved through inhibition of prostasin activity, identifying a potential therapeutic target in the disease. TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT00506792; URL: www.clinicaltrials.gov.

An international randomized multicenter comparison of nasal potential difference techniques.

BACKGROUND: The transepithelial nasal potential difference (NPD) is used to assess cystic fibrosis transmembrane conductance regulator (CFTR) activity. Unreliability, excessive artifacts, and lack of standardization of current testing systems can compromise its use as a diagnostic test and outcome measure for clinical trials. METHODS: To determine whether a nonperfusing (agar gel) nasal catheter for NPD measurement is more reliable and less susceptible to artifacts than a continuously perfusing nasal catheter, we performed a multicenter, randomized, crossover trial comparing a standardized NPD protocol using an agar nasal catheter with the same protocol using a continuously perfusing catheter. The data capture technique was identical in both protocols. A total of 26 normal adult subjects underwent NPD testing at six different centers. RESULTS: Artifact frequency was reduced by 75% (P < .001), and duration was less pronounced using the agar catheter. The measurement of sodium conductance was similar between the two catheter methods, but the agar catheter demonstrated significantly greater CFTR-dependent hyperpolarization, because Δ zero Cl- + isoproterenol measurements were significantly more hyperpolarized with the agar catheter (224.2 ± 12.9 mV with agar vs 18.2 ± 9.1 mV with perfusion, P < .05). CONCLUSIONS: The agar nasal catheter approach demonstrates superior reliability compared with the perfusion nasal catheter method for measurement of NPD. This nonperfusion catheter method should be considered for adoption as a standardized protocol to monitor CFTR activity in clinical trials.