William T. Harris

Safety, pharmacokinetics, and pharmacodynamics of ivacaftor in patients aged 2–5 years with cystic fibrosis and a CFTR gating mutation (KIWI): an open-label, single-arm study

BACKGROUND Ivacaftor has been shown to be a safe, effective treatment for cystic fibrosis in patients aged 6 years or older with a CFTR gating mutation. We aimed to assess the safety, pharmacokinetics, and pharmacodynamics of ivacaftor in children aged 2-5 years. METHODS In the two-part KIWI study, we enrolled children aged 2-5 years weighing 8 kg or more with a confirmed diagnosis of cystic fibrosis and a CFTR gating mutation on at least one allele from 15 hospitals in the USA, UK, and Canada. Participants received oral ivacaftor 50 mg (if bodyweight <14 kg) or 75 mg (if bodyweight ≥14 kg) every 12 h for 4 days in part A (to establish the short-term safety of doses for subsequent assessment in part B), and then for 24 weeks in part B (to assess safety and longer-term pharmacodynamics). Children could participate in both or just one part of the study. Primary outcomes were pharmacokinetics and safety, analysed in all patients who received at least one dose of ivacaftor. Secondary outcomes were absolute change from baseline in sweat chloride concentrations and bodyweight, body-mass index (BMI), and height Z scores, and pharmacokinetic parameter estimation of ivacaftor. This study is registered with ClinicalTrials.gov, number NCT01705145. FINDINGS Between Jan 8, 2013, and March 1, 2013, nine patients were enrolled onto part A of the study, all of whom completed the 4 day treatment period, and eight of whom took part in part B. Between June 28, 2013, and Sept 26, 2013, 34 patients were enrolled in part B, 33 of whom completed the 24 week treatment period. All patients received at least one dose of ivacaftor. Results of ivacaftor pharmacokinetics suggested that exposure was similar to that reported in adults (median Cmin were 536 ng/mL for the 50 mg dose; 580 ng/mL for the 75 mg dose; median ivacaftor AUC values were 9840 ng × h/mL and 10 200 ng × h/mL, respectively). Common adverse events in part B included cough (in 19 [56%] of 34 patients) and vomiting (in ten [29%]). Five (15%) patients had liver function test (LFT) results that were more than eight times higher than the upper limit of normal, four of whom had study drug interrupted, and one of whom had study drug discontinued. Six (18%) of 34 patients had seven serious adverse events; a raised concentration of transaminases was the only serious adverse event regarded as related to ivacaftor and the only adverse event that resulted in study treatment discontinuation. At week 24, in patients for whom we had data, sweat chloride had changed from baseline by a mean of -46·9 mmol/L (SD 26·2, p<0·0001), weight Z score by 0·2 (0·3; p<0·0001), BMI Z score by 0·4 (0·4, p<0·0001), and height Z score by -0·01 (0·3; p=0·84). INTERPRETATION Ivacaftor at doses of 50 mg and 75 mg seems to be safe in children aged 2-5 years with cystic fibrosis with a gating mutation followed up for 24 weeks, although the frequency of elevated LFTs suggests that monitoring should be frequent in young children, particularly those with a history of elevated LFTs. Results of an ongoing extension study assessing durability of these effects and longer-term safety are warranted. FUNDING Vertex Pharmaceuticals Incorporated.

Myofibroblast differentiation and enhanced TGF-B signaling in cystic fibrosis lung disease.

Rationale TGF-β, a mediator of pulmonary fibrosis, is a genetic modifier of CF respiratory deterioration. The mechanistic relationship between TGF-β signaling and CF lung disease has not been determined. Objective To investigate myofibroblast differentiation in CF lung tissue as a novel pathway by which TGF-β signaling may contribute to pulmonary decline, airway remodeling and tissue fibrosis. Methods Lung samples from CF and non-CF subjects were analyzed morphometrically for total TGF-β1, TGF-β signaling (Smad2 phosphorylation), myofibroblast differentiation (α-smooth muscle actin), and collagen deposition (Masson trichrome stain). Results TGF-β signaling and fibrosis are markedly increased in CF (p<0.01), and the presence of myofibroblasts is four-fold higher in CF vs. normal lung tissue (p<0.005). In lung tissue with prominent TGF-β signaling, both myofibroblast differentiation and tissue fibrosis are significantly augmented (p<0.005). Conclusions These studies establish for the first time that a pathogenic mechanism described previously in pulmonary fibrosis is also prominent in cystic fibrosis lung disease. The presence of TGF-β dependent signaling in areas of prominent myofibroblast proliferation and fibrosis in CF suggests that strategies under development for other pro-fibrotic lung conditions may also be evaluated for use in CF.

Plasma TGF-β1 in pediatric cystic fibrosis: Potential biomarker of lung disease and response to therapy

Transforming growth factor beta‐1 (TGF‐β1) is an important genetic modifier of lung disease severity in cystic fibrosis (CF), yet the mechanism behind this disease association remains unknown. Initial steps in the investigation of the relationship between TGF‐β1 and CF lung disease include determining the most appropriate available biospecimen for TGF‐β1 protein measurement.

Inhaled versus systemic antibiotics and airway inflammation in children with cystic fibrosis and Pseudomonas.

Inhaled tobramycin has been shown to transiently clear Pseudomonas from lower airways in early cystic fibrosis (CF), but does not markedly reduce lung inflammation, a key factor in disease progression.

Transforming growth factor-β1 in bronchoalveolar lavage fluid from children with cystic fibrosis†

Transforming factor β1 (TGF‐β1) genetic polymorphisms have been identified as a modifier of cystic fibrosis (CF) lung disease severity. However, few data link TGF‐β1 protein levels and clinical markers of CF lung disease severity.

Tgf-beta downregulation of distinct chloride channels in cystic fibrosis-affected epithelia.

Rationale The cystic fibrosis transmembrane conductance regulator (CFTR) and Calcium-activated Chloride Conductance (CaCC) each play critical roles in maintaining normal hydration of epithelial surfaces including the airways and colon. TGF-beta is a genetic modifier of cystic fibrosis (CF), but how it influences the CF phenotype is not understood. Objectives We tested the hypothesis that TGF-beta potently downregulates chloride-channel function and expression in two CF-affected epithelia (T84 colonocytes and primary human airway epithelia) compared with proteins known to be regulated by TGF-beta. Measurements and Main Results TGF-beta reduced CaCC and CFTR-dependent chloride currents in both epithelia accompanied by reduced levels of TMEM16A and CFTR protein and transcripts. TGF-beta treatment disrupted normal regulation of airway-surface liquid volume in polarized primary human airway epithelia, and reversed F508del CFTR correction produced by VX-809. TGF-beta effects on the expression and activity of TMEM16A, wtCFTR and corrected F508del CFTR were seen at 10-fold lower concentrations relative to TGF-beta effects on e-cadherin (epithelial marker) and vimentin (mesenchymal marker) expression. TGF-beta downregulation of TMEM16A and CFTR expression were partially reversed by Smad3 and p38 MAPK inhibition, respectively. Conclusions TGF-beta is sufficient to downregulate two critical chloride transporters in two CF-affected tissues that precedes expression changes of two distinct TGF-beta regulated proteins. Our results provide a plausible mechanism for CF-disease modification by TGF-beta through effects on CaCC.

Alterations in blood leukocytes of G551D-bearing cystic fibrosis patients undergoing treatment with ivacaftor.

BACKGROUND Ivacaftor improves clinical outcome by potentiation of mutant G551D CFTR. Due to the presence of CFTR in monocytes and polymorphonuclear neutrophils (PMNs), we hypothesized that ivacaftor may impact leukocyte activation. METHODS We examined blood leukocytes from G551D CF subjects prior to and at one and six months after receiving ivacaftor. Blood leukocytes from ivacaftor-naïve G551D, F508del, and healthy controls were also treated with ivacaftor ex vivo to assess mutation-specific effects. RESULTS Compared to healthy controls, G551D CF subjects had significantly higher expression of active CD11b on PMNs and of CD63 on monocytes, which were normalized by in vivo ivacaftor treatment. Ex vivo exposure to ivacaftor of blood cells from G551D, but not F508del and healthy subjects, resulted in changes in CXCR2 and CD16 expression on PMNs. CONCLUSIONS In vivo and ex vivo exposure of G551D CF leukocytes to ivacaftor resulted in an altered activation profile, suggesting mutation-specific leukocyte modulation.

Adherence to Airway Clearance Therapy in Pediatric Cystic Fibrosis: Socioeconomic Factors and Respiratory Outcomes

The evidence linking socioeconomic status (SES) and adherence in cystic fibrosis (CF) is inconclusive and focused on medication uptake. We examined associations between SES, adherence to airway clearance therapy (ACT), and CF respiratory outcomes.

MicroRNA-145 Antagonism Reverses TGF-β Inhibition of F508del CFTR Correction in Airway Epithelia

Rationale: MicroRNAs (miRNAs) destabilize mRNA transcripts and inhibit protein translation. miR‐145 is of particular interest in cystic fibrosis (CF) as it has a direct binding site in the 3′‐untranslated region of CFTR (cystic fibrosis transmembrane conductance regulator) and is upregulated by the CF genetic modifier TGF (transforming growth factor)‐&bgr;. Objectives: To demonstrate that miR‐145 mediates TGF‐&bgr; inhibition of CFTR synthesis and function in airway epithelia. Methods: Primary human CF (F508del homozygous) and non‐CF airway epithelial cells were grown to terminal differentiation at the air‐liquid interface on permeable supports. TGF‐&bgr; (5 ng/ml), a miR‐145 mimic (20 nM), and a miR‐145 antagonist (20 nM) were used to manipulate CFTR function. In CF cells, lumacaftor (3 &mgr;M) and ivacaftor (10 &mgr;M) corrected mutant F508del CFTR. Quantification of CFTR mRNA, protein, and function was done by standard techniques. Measurements and Main Results: miR‐145 is increased fourfold in CF BAL fluid compared with non‐CF (P < 0.01) and increased 10‐fold in CF primary airway epithelial cells (P < 0.01). Exogenous TGF‐&bgr; doubles miR‐145 expression (P < 0.05), halves wild‐type CFTR mRNA and protein levels (P < 0.01), and nullifies lumacaftor/ivacaftor F508del CFTR correction. miR‐145 overexpression similarly decreases wild‐type CFTR protein synthesis (P < 0.01) and function (P < 0.05), and eliminates F508del corrector benefit. miR‐145 antagonism blocks TGF‐&bgr; suppression of CFTR and enhances lumacaftor correction of F508del CFTR. Conclusions: miR‐145 mediates TGF‐&bgr; inhibition of CFTR synthesis and function in airway epithelia. Specific antagonists to miR‐145 interrupt TGF‐&bgr; signaling to restore F508del CFTR modulation. miR‐145 antagonism may offer a novel therapeutic opportunity to enhance therapeutic benefit of F508del CFTR correction in CF epithelia.

Ivacaftor treatment of cystic fibrosis in children aged 12 to <24 months and with a CFTR gating mutation (ARRIVAL): a phase 3 single-arm study

BACKGROUND Ivacaftor is generally safe and effective in patients aged 2 years and older who have cystic fibrosis and specific CFTR mutations. We assessed its use in children aged 12 to <24 months. METHODS The ARRIVAL study is a phase 3, single-arm, two-part, multicentre study. Eligible children were aged 12 to <24 months at enrolment and had a confirmed diagnosis of cystic fibrosis and a CFTR gating mutation on at least one allele and could participate in one or both parts of the study. Children received 50 mg (bodyweight 7 to <14 kg) or 75 mg (bodyweight ≥14 to <25 kg) ivacaftor orally every 12 h. In study part A, children received ivacaftor for 3 days plus one morning. In study part B, children received 24 weeks of treatment. Children were enrolled into part A at seven sites in Australia (one site), the UK (one), and the USA (five) and into part B at 13 sites in Australia (two sites), Canada (one), the UK (three), and the USA (seven). Primary endpoints were pharmacokinetics (part A) and safety (parts A and B) in children who received at least one dose of ivacaftor. Secondary endpoints in part B were pharmacokinetics in children who received at least one dose of ivacaftor and absolute change from baseline in sweat chloride concentration. We also explored changes in growth parameters and markers of pancreatic function. This study is registered with ClinicalTrials.gov, number NCT02725567. FINDINGS Children aged 12 to <24 months were enrolled between Aug 25, 2016, and Nov 1, 2017. Seven children were enrolled in part A, of whom five received 50 mg and two received 75 mg ivacaftor. All completed treatment. Of 19 children enrolled in part B, including one from part A, all received 50 mg ivacaftor and 18 completed treatment (one withdrew because of difficulty with blood draws). All children received at least one dose of ivacaftor. Pharmacokinetics indicated exposure was similar to that in children aged 2 to <6 years and adults. No children discontinued because of adverse events or safety findings. In part A, three (43%) of seven children had treatment-emergent adverse events, all of which were mild and deemed not to be or unlikely to be related to ivacaftor. By 24 weeks in part B, treatment-emergent adverse events had been reported in 18 (95%) of 19 children, of which most were mild or moderate and the most frequent was cough (14 [74%] children). Two children in part B had four serious adverse events: one had constipation (possibly related to ivacaftor), distal intestinal obstruction syndrome, and eczema herpeticum, and one had persistent cough, all needing hospital admission. In five (28%) of 18 children aspartate or alanine aminotransferase concentrations rose to more than three times the upper limit of normal (to more than eight times in two children with concurrent infections). At week 24, the mean absolute change from baseline in sweat chloride concentration was -73·5 (SD 17·5) mmol/L. Growth parameters for age were normal at baseline and at week 24. At week 24, concentrations of faecal elastase-1 had increased and concentrations of immunoreactive trypsinogen had decreased from baseline. Mean serum lipase and amylase were raised at baseline and rapidly decreased after treatment was started. INTERPRETATION Ivacaftor was generally safe and well tolerated in children aged 12 to <24 months for up to 24 weeks and was associated with rapid and sustained reductions in sweat chloride concentrations. Improvements in biomarkers of pancreatic function suggest that ivacaftor preserves exocrine pancreatic function if started early. The study is continuing in infants younger than 12 months. FUNDING Vertex Pharmaceuticals Incorporated.