Gastroenterological Endpoints in Drug Trials for Cystic Fibrosis

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1 51:S18 S22 (2016) Gastroenterological Endpoints in Drug Trials for Cystic Fibrosis Frank A.J.A. Bodewes, MD, PhD, 1 * Henkjan J. Verkade, MD, PhD, 1 and Micheal Wilschanski, MD 2 Summary. The phenotype of cystic fibrosis includes a wide variety of clinical and biochemical gastrointestinal presentations. These gastrointestinal characteristics of the disease have come under renewed interest as potential outcome measures and clinical endpoints for therapeutic trials in cystic fibrosis. Established gastrointestinal clinical endpoints, like e.g. fecal elastase-1, are already used in trials. Other potential gastrointestinal outcome measures gather more scientific interest for evaluation in future trials. Gastrointestinal outcome measures look particularly relevant and promising for trials in CF patients with normal lung function or therapeutic studies in young children and infants. We review, the currently reported gastrointestinal effects of CFTR modulation therapies and discuss the potential of gastrointestinal outcome measures for therapeutic trials in cystic fibrosis. Pediatr Pulmonol. 2016;51:S18 S22. ß 2016 Wiley Periodicals, Inc. Key words: cystic fibrosis; gastrointestinal; clinical outcome measures; clinical endpoint; biomarkers. Funding source: none reported. INTRODUCTION Cystic fibrosis (CF) is a severe, genetic, progressive multi-organ disease with a high morbidity and mortality. CF is caused by decreased or absent function of the CF transmembrane conductance regulator (CFTR) protein due to mutations in the CFTR gene. 1 The CFTR protein is a transmembrane chloride channel, expressed mainly in secretory epithelia, including sweat glands, lungs, pancreas, intestine, and bile ducts. 2 The prognosis for CF patients has improved dramatically over recent decades. To date, the median survival of CF patients is approximately 40 years. 3 The primary cause of premature death in CF patients relates to a progressive decline in pulmonary function due to recurrent pulmonary infections. Severe gastrointestinal manifestations play a significant role in CF. Exocrine pancreatic insufficiency (EPI) is present in the majority of CF patients, often already at birth or in the 1st weeks of life. Many CF patients suffer from intestinal fat malabsorption, leading to poor growth and weight gain and deficiencies of fat-soluble vitamins and essential fatty acids. A substantial percentage of CF patients, suffer from intestinal obstruction phenomena varying from recurrent abdominal pain and constipation to the potentially lifethreatening distal intestinal obstruction syndrome (DIOS). Finally, up to 25% of CF patients develop some form of CFrelated liver disease (CFLD). CFLD occurs in different levels of severity. The most severe form of CFLD is the development of cirrhosis and portal hypertension, which occurs in about 5% of CF patients. 4 ß 2016 Wiley Periodicals, Inc. CFTR MODULATION THERAPIES With the recent development and clinical implementation of CFTR protein modulation (potentiators and correctors), significant advances have been made in the treatment of CF. CFTR correctors and potentiators target the pathophysiology of the disease, by improving the processing and/or function of the CFTR protein function. 5 The currently available CFTR correctors have been demonstrated to improve or restore CFTR protein function using in vitro and ex-vivo models. Several groundbreaking clinical trials have demonstrated a highly significant clinical effect in genetically selective groups of CF patients. There is, however, considerable variation in the degree of functional restoration and clinical 1 Department of Pediatric Gastroenterology, University Medical Center Groningen, Groningen, The Netherlands. 2 Pediatric Gastroenterology Unit, Division of Pediatrics, Hadassah University Hospitals, Jerusalem, Israel. Correspondence to: Frank A.J.A. Bodewes, MD, PhD, Department of Pediatric Gastroenterology University Medical Center Groningen, PO Box 30001, 9700 RB Groningen, The Netherlands. f.a.j.a.bodewes@umcg.nl Received 4 June 2016; Revised 28 June 2016; Accepted 3 July DOI /ppul Published online 21 July 2016 in Wiley Online Library (wileyonlinelibrary.com).

2 CF GI Clinical Endpoints S19 response among the various mutations and mutation classes of CF. To date, two CFTR modulation-based therapies have been approved for the treatment of CF based on positive effects in randomized clinical trials: Ivacaftor (Kalydeco 1 ) and the combination of lumacaftor and ivacaftor (Orkambi 1 ). 6 8 Ivacaftor monotherapy is registered for the treatment of CF patients with so-called gating mutations. Gating mutations are characterized by an unaffected intracellular CFTR protein synthesis, processing, and surface expression, but disrupted opening (gating) of the protein for transporting chloride. Ivacaftor, a CFTR protein corrector, improves the protein gating function and thus can restore chloride transport. The lumacaftor/ivacaftor combination targets the CFTR function at two separate levels, increasing the amount of functional protein at the plasma membrane and improving the function of the protein at the plasma membrane. It is registered, at the end of 2015, for treatment of CF patients homozygous for the F508del mutation. The F508del mutation is the most common CFTR mutation in CF patients. Patients with the F508del mutation have a normal CFTR protein synthesis. However, the mutation disrupts both the intracellular protein processing, leading to decreased membrane surface expression and decreased gating functionality of the protein. The combination therapy of a CFTR protein processing potentiator (lumacaftor) and a CFTR corrector (ivacaftor) targets both levels of the pathophysiology. To date, in clinical trials, the effect of CFTR modulation effect is assessed on several established clinical outcome measures for CF including improvement in sweat chloride concentration, forced expiratory volume in 1 sec (FEV1), absolute weight gain or BMI percentile, and a patient-reported outcome measure based on the validated CF Questionnaire (CFQ). In the lumacaftor/ ivacaftor combination trials, the pulmonary exacerbation rate was included as an additional surrogate outcome for the pulmonary condition of CF patients. For clinical trials with CFTR modulators in young children and infants, fecal elastase-1 as a biomarker of exocrine pancreas secretion function has been reported. CURRENTLY DESCRIBED GASTROINTESTINAL EFFECTS OF CFTR MODULATION THERAPIES Weight Gain and BMI An increase in body weight has been the most striking gastrointestinal-related effect of CFTR modulation. This effect was first reported for ivacaftor. Ramsey et al. reported an absolute increase in weight of 3.1 kg in G551D CF patients over a 6-month treatment period. 7 The effect of ivacaftor was reported to be sustained over time periods up to 3 years. 9 Davies et al. reported similar patterns of weight gain and BMI improvement after ivacaftor treatment in children 6 11 years of age with a F508del mutation. 10 The lumacaftor/ivacaftor combination for patients homozygous for the F508del mutation also resulted in a significant increase in weight and BMI compared to placebo (þ1.2 to 1.6 kg, and þ0.24 to 0.28km/m 2, respectively, each P < 0.001); however, the effect was of a clearly smaller magnitude as for as ivacaftor monotherapy in patients with a gating mutation. 8 This effect may be influenced by the type of CFTR mutation. The mechanism underlying the effects of CFTR modulation on weight gain and BMI has not been resolved. However, it could potentially be related to the improved CFTR function-dependent intestinal absorption of nutrients including dietary fats and proteins. Intestinal ph It has been reported that the ph profile over the length of the intestinal lumen differs between CF patients and healthy controls. The dynamic intestinal ph can be measured using an intraluminal ph measuring capsule, for example using the so-called Smartpill The most striking difference in CF compared to healthy controls is the delayed duodenal ph recovery from acidity after gastric emptying. In healthy controls, after the passage of the stomach content into the duodenum, the ph in the duodenum drops but then rapidly increases to a ph around 7. The increase of ph is clearly decreased and prolonged in the duodenum of CF patients. Gelfond et al. showed that ivacaftor normalizes the ph profile of the intestinal lumen in patients with a G551D mutation. 12 It is speculated that recovery of duodenal or pancreatic CFTR-mediated bicarbonate secretion underlies this clear treatment effect. Fecal Elastase-1 Davies et al. recently reported the results of the KIWI study, in which children aged 2 5 years old with a CFTR gating mutation were treated with ivacaftor. 13 Ninety-two percent of the studied population had an EPI based on a fecal elastase-1 concentration below 50 mg/g. Ivacaftor increased fecal elastase concentration with 100 mg/g. However, there was a wide variation among the patients, and even within individual patients over time. Nevertheless, the results do indicate that EPI, based on the pancreas fibrosis, could be reversible. These findings suggest that early or even preemptive treatment of CFTR dysfunction with modulators might completely recover or prevent the development of EPI in CF. Hepatic Steatosis In a case-study, Hayes et al. reported the association between ivacaftor treatment and the recovery of

3 S20 Bodewes et al. radiologically proven steatosis of the liver. 14 In a 17-yearold female with a G551D CFTR mutation, they found that the biopsy-proven non-alcoholic steatohepatitis developed to a radiologically normal liver on a CT scan without any signs of steatosis after 2 years of ivacaftor treatment. Hepatic steatosis is a frequent, not well-explained finding in CF patients. This case report suggests a beneficial effect of CFTR modulation on CFTR-dependent hepatic lipid metabolism. GI-Related Adverse Effect of CFTR Modulation To underline that CFTR modulators have effect(s) in the GI tract, we analyzed GI-related adverse events in recent clinical trials. GI-related adverse reactions like nausea, vomiting, and abdominal pain are very rarely reported in CFTR modulator trials and certainly not more frequent than in placebo-treated patients. The only adverse event that is variously reported in different studies is the elevation of liver enzymes. In the ivacaftor studies in adult CF patients with a G551D mutation, elevation of liver enzymes was reported in only one out of 83 subjects of the treated patients. 7 Similarly, Davies et al. did not observe elevation of liver enzymes in pediatric CF patients with a G551D mutation (age 6 11 years). 10 In the lumacaftor/ivacaftor combination trial in CF patients with a F508del mutation, the incidence of LFT elevation was similar to that in placebo-treated patients, 5%. 8 However, in the KIWI trial, up to 15% of CF patients aged 2 5 years with a gating mutation had elevated liver enzymes (>8 ULN). 13 In four out the 34 patients, the study was interrupted because of the elevation of liver function tests. Also in this study, the incidence of vomiting was rather high (up to 30%) in the children treated with ivacaftor. These results suggest that there might be an age-dependent sensibility of the liver to ivacaftor CFTR modulator treatment. Intestinal Current Measurements (ICM) Intestinal current measurements (ICM) are an ex vivo electrophysiological method in which a freshly obtained rectal biopsy is evaluated for its electrical responses related to chloride ion transport. 15 The procedure is performed by mounting a fresh rectal biopsy in an Ussing chamber and adding a series of chemicals to the baths, to stimulate secretion. It is a method that assesses functional CFTR activity. There is a clear difference in ICM between normal (non-cf) and abnormal (CF) tissues. 16 The value of ICM for diagnostic reasons and assessment of treatment effects was recently extensively reviewed. 17,18 In 2015, Gr aber et al. reported that ICM can be used to quantify the in vivo effects of ivacaftor on restoring CFTR function in G551D patients. 19 These results indicate the value of using ICM as a potential outcome measure for the assessment of the therapeutic effects of CFTR modulators in individual patients. NEW POTENTIAL GI RELATED CLINICAL EFFECTS AND OUTCOME MEASURES FOR CFTR MODULATION THERAPIES Recently, several new CF-related developments and insights in the gastrointestinal involvement and diagnostic options have been reported. 20 They cover different aspects and characteristics of the CF gastrointestinal clinical phenotype including intestinal inflammation or CFTR protein function measurement in the gut and intestinal organoids. Intestinal Inflammation Animal and human studies have indicated that intestinal inflammation is prevalent under CF conditions. 21,22 To date, the underlying cause of intestinal inflammation in CF is not known. It is hypothesized that the inflammation could be related to alterations in bacterial flora secondary to dietary or metabolic factors in the micro-milieu of the gut. Alternatively, there could be a more direct effect of intestinal CFTR on the microflora or the inflammatory responses in the intestine. In general, endoscopy and mucosal biopsies are the gold standard for the diagnosis of intestinal inflammation. However, in clinical practice, these investigations are not often performed in CF because of the invasive character of the procedures and the current lack of therapeutic possibilities. Different studies have been reported concerning surrogate parameters, like fecal markers and video endoscopy, for assessing intestinal inflammation in CF. Fecal Calprotectin and Other Markers of Intestinal Inflammation Several fecal biomarkers of intestinal inflammation are now available, of which fecal calprotectin is the most frequently used both in research and clinical practice. 23,24 Calprotectin is a protein that originates from inflammatory neutrophils in the body, and the intestine fecal calprotectin concentration is increased upon intestinal inflammation. It has been demonstrated in several studies that fecal calprotectin levels in CF patients are increased compared to healthy individuals. 21 Dhaliwal et al. reported a unique CF spectrum of fecal biomarkers compared to other forms of intestinal inflammatory disease like IBD. In CF, increased fecal calprotectin often coincides with normal fecal S100A12 and osteoprotegerin concentrations, other markers of intestinal inflammation. 25 They also report that the increase in fecal calprotectin as a marker of severity for intestinal inflammation strongly correlated with poor growth in CF children.

4 CF GI Clinical Endpoints S21 Video Capsule Endoscopy Small bowel capsule endoscopy (SBCE) is a visual diagnostic tool for intestinal inflammation. The use of SBCE in CF patients has been reported in two studies. Werlin et al. demonstrated that most CF patients had diffuse areas of inflammation with varying degrees of severity findings in the small intestine. 22 Recently, Flass et al. confirmed these findings but additionally showed that patients with CF-related cirrhosis had more severe intestinal mucosal lesions on capsule endoscopy than those without CF-related cirrhosis. 26 Markers of Bile Salt Metabolism Increased fecal bile salt excretion is an intrinsic and consistent phenotype of CF. The increased fecal bile salt excretion is independent of CF-related intestinal fat malabsorption or EPI. 27 Measurements of markers of bile salt metabolism, therefore, provide an opportunity to evaluate this CFTR protein-related gut function. Plasma Fibroblast Growth Factor 19 (FGF19) is an intestinal nuclear receptor hormone involved in the negative feedback of hepatic bile salt synthesis and is a biomarker for intestinal bile salt loss. 28 In CF patients, increased intestinal bile salt loss decreases FGF19 concentration in plasma and stimulates hepatic bile salt synthesis. Plasma 4- cholesten-3-one (C4) is an intermediate product of the bile salt biosynthesis. It functions as a biomarker for CYP7A1 enzyme regulated hepatic bile salt synthesis. Increased intestinal bile salt loss is compensated by de novo hepatic bile salt synthesis. This increase in synthesis is reflected by an increase in the plasma C4 Levels. 29,30 Intestinal Organoids Intestinal organoids are sphere-like intestinal mucosal crypt-villus structures derived from primary intestinal stem cells. 31 Intestinal organoids can be cultured from rectal biopsies, which enables the procuring of mutationspecific intestinal tissue cultures. Intestinal organoids express CFTR making them suitable to assess CFTR protein function. CFTR activity can be quantitatively assessed using a swelling assay that reflects the CFTR chloride transport function. 32 Via this methodology, small molecules and other potential CFTR protein modulators can be tested for their potency to functionally corrects CFTR activity on a mutation and patient specific basis. 33 A new approach is a bioassay using intestinal organoids to measure the effect of CFTR modulators in human plasma. 34 In these methods, the correction effect of plasma samples of treated patients on intestinal organoids is used as ex-vivo dose and range finding methodology. Currently, the intestinal organoids are mainly used to evaluate CFTR treatment interactions. However, the Fig. 1. Schematic representation of gastrointestinal endpoints and clinical outcome measures in cystic fibrosis. organoid model does not seem suitable for further intestinal function tests because of structural limitations. The closed, sphere structure does not facilitate the quantitative assessment of luminal transport of various compounds. Additionally, the current organoid systems do not allow for the complex microbiota and immunological interactions in the gut to be incorporated. CONCLUSION CF patients present with a variety of distinct clinical and biochemical gastrointestinal phenotypes. In recent years, several newly discovered or revisited CF-related GI properties have been evaluated in the light of novel therapeutic options for CF (Fig. 1). Several of these GI outcome measures, like fecal elastase-1, are currently been used in trials and clinical practice. Other GI outcome measures gather more and more interest for evaluation in upcoming trials and research. GI outcome measures seem particularly relevant for research in infants and children with CF. Based on this prospect, we expect an increase in the interest for the opportunities that the GI tract offers in terms of the therapeutic and preventive treatments of CF. REFERENCES 1. Riordan JR, Rommens JM, Kerem B, Alon N, Rozmahel R, Grzelczak Z, Zielenski J, Lok S, Plavsic N, Chou JL. Identification of the cystic fibrosis gene: cloning and characterization of complementary DNA. Science 1989;245: Trezíse AE, Buchwald M. In vivo cell-specific expression of the cystic fibrosis transmembrane conductance regulator. Nature 1991;353:

5 S22 Bodewes et al. 3. Cystic fibrosis Foundation patient registry 2014 annual data report Bethesda, Maryland 2016 cystic fibrosis foundation Stonebraker JR, Ooi CY, Pace RG, Corvol H, Knowles MR, Durie PR, Ling SC. Features of severe liver disease with portal hypertension in patients with cystic fibrosis. Clin Gastroenterol Hepatol Mayer-Hamblett N, Boyle M, VanDevanter D. Advancing clinical development pathways for new CFTR modulators in cystic fibrosis. Thorax 2016;71: Accurso FJ, Rowe SM, Clancy J, Boyle MP, Dunitz JM, Durie PR, Sagel SD, Hornick DB, Konstan MW, Donaldson SH. Effect of VX-770 in persons with cystic fibrosis and the G551D-CFTR mutation. N Engl J Med 2010;363: Ramsey BW, Davies J, McElvaney NG, Tullis E, Bell SC, Drevínek P, Griese M, McKone EF, Wainwright CE, Konstan MW. A CFTR potentiator in patients with cystic fibrosis and the G551D mutation. N Engl J Med 2011;365: Wainwright CE, Elborn JS, Ramsey BW, Marigowda G, Huang X, Cipolli M, Colombo C, Davies JC, De Boeck K, Flume PA. Lumacaftor-ivacaftor in patients with cystic fibrosis homozygous for Phe508del CFTR. N Engl J Med 2015;373: Sawicki GS, McKone EF, Pasta DJ, Millar SJ, Wagener JS, Johnson CA, Konstan MW. Sustained benefit from ivacaftor demonstrated by combining clinical trial and cystic fibrosis patient registry data. Am J Respir Crit Care Med 2015;192: Davies JC, Wainwright CE, Canny GJ, Chilvers MA, Howenstine MS, Munck A, Mainz JG, Rodriguez S, Li H, Yen K. Efficacy and safety of ivacaftor in patients aged 6 to 11 years with cystic fibrosis with a G551D mutation. Am J Respir Crit Care Med 2013;187: Maqbool S, Parkman HP, Friedenberg FK. Wireless capsule motility: comparison of the SmartPill 1 GI monitoring system with scintigraphy for measuring whole gut transit. Dig Dis Sci 2009;54: Gelfond D, Ma C, Semler J, Borowitz D. Intestinal ph and gastrointestinal transit profiles in cystic fibrosis patients measured by wireless motility capsule. Dig Dis Sci 2013;58: Davies JC, Cunningham S, Harris WT, Lapey A, Regelmann WE, Sawicki GS, Southern KW, Robertson S, Green Y, Cooke J. 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. Lancet Respir Med 2016;4: Hayes DJr, Warren PS, McCoy KS, Sheikh SI. Improvement of hepatic steatosis in cystic fibrosis with ivacaftor therapy. J Pediatr Gastroenterol Nutr 2015;60: Veeze HJ, Halley DJ, Bijman J, de Jongste JC, de Jonge HR, Sinaasappel M. Determinants of mild clinical symptoms in cystic fibrosis patients. residual chloride secretion measured in rectal biopsies in relation to the genotype. J Clin Invest 1994;93: Clancy JP, Szczesniak RD, Ashlock MA, Ernst SE, Fan L, Hornick DB, Karp PH, Khan U, Lymp J, Ostmann AJ. Multicenter intestinal current measurements in rectal biopsies from CF and non-cf subjects to monitor CFTR function. PLoS ONE 2013;8:e De Boeck K, Kent L, Davies J, Derichs N, Amaral M, Rowe SM, Middleton P, de Jonge H, Bronsveld I, Wilschanski M, et al. CFTR biomarkers: time for promotion to surrogate end-point. Eur Respir J 2013;41: Cohen-Cymberknoh M, Yaakov Y, Shoseyov D, Shteyer E, Schachar E, Rivlin J, Bentur L, Picard E, Aviram M, Israeli E. Evaluation of the intestinal current measurement method as a diagnostic test for cystic fibrosis. Pediatr Pulmonol 2013;48: Graeber SY, Hug MJ, Sommerburg O, Hirtz S, Hentschel J, Heinzmann A, Dopfer C, Schulz A, Mainz JG, T ummler B. Intestinal current measurements detect activation of mutant CFTR in patients with cystic fibrosis with the G551D mutation treated with ivacaftor. Am J Respir Crit Care Med 2015;192: Bodewes FA, Verkade HJ, Taminiau JA, Borowitz D, Wilschanski M. Cystic fibrosis and the role of gastrointestinal outcome measures in the new era of therapeutic CFTR modulation. J Cystic Fibros 2015;14: Bruzzese E, Raia V, Gaudiello G, Polito G, Buccigrossi V, Formicola V, Guarino A. Intestinal inflammation is a frequent feature of cystic fibrosis and is reduced by probiotic administration. Aliment Pharmacol Ther 2004;20: Werlin SL, Benuri-Silbiger I, Kerem E, Adler SN, Goldin E, Zimmerman J, Malka N, Cohen L, Armoni S, Yatzkan-Israelit Y. Evidence of intestinal inflammation in patients with cystic fibrosis. J Pediatr Gastroenterol Nutr 2010;51: Kopylov U, Rosenfeld G, Bressler B, Seidman E. Clinical utility of fecal biomarkers for the diagnosis and management of inflammatory bowel disease. Inflamm Bowel Dis 2014;20: Lee JM, Leach ST, Katz T, Day AS, Jaffe A, Ooi CY. Update of faecal markers of inflammation in children with cystic fibrosis. Mediators Inflamm 2012; Dhaliwal J, Leach S, Katz T, Nahidi L, Pang T, Lee JM, Strachan R, Day AS, Jaffe A, Ooi CY. Intestinal inflammation and impact on growth in children with cystic fibrosis. J Pediatr Gastroenterol Nutr 2015;60: Flass T, Tong S, Frank DN, Wagner BD, Robertson CE, Kotter CV, Sokol RJ, Zemanick E, Accurso F, Hoffenberg EJ. Intestinal lesions are associated with altered intestinal microbiome and are more frequent in children and young adults with cystic fibrosis and cirrhosis. PLoS ONE 2015;10:e Strandvik B, Einarsson K, Lindblad A, Angelin B. Bile acid kinetics and biliary lipid composition in cystic fibrosis. J Hepatol 1996;25: Walters JRF, Tasleem AM, Omer OS, Brydon WG, Dew T, Le Roux CW. A new mechanism for bile acid diarrhea: defective feedback inhibition of bile acid biosynthesis. Clin Gastroenterol Hepatol 2009;7: Schaap FG, van der Gaag NA, Gouma DJ, Jansen PLM. High expression of the bile salt-homeostatic hormone fibroblast growth factor 19 in the liver of patients with extrahepatic cholestasis. Hepatology 2009;49: Gothe F, Beigel F, Rust C, Hajji M, Koletzko S, Freudenberg F. Bile acid malabsorption assessed by 7 alpha-hydroxy-4-cholesten-3-one in pediatric inflammatory bowel disease: correlation to clinical and laboratory findings. J Crohn s Colitis 2014;8: Sato T, Vries RG, Snippert HJ, van de Wetering M, Barker N, Stange DE, van Es JH, Abo A, Kujala P, Peters PJ. Single Lgr5 stem cells build crypt villus structures in vitro without a mesenchymal niche. Nature 2009;459: Dekkers JF, Wiegerinck CL, de Jonge HR, Bronsveld I, Janssens HM, de Winter-de Groot Karin M, Brandsma AM, de Jong NW, Bijvelds MJ, Scholte BJ. A functional CFTR assay using primary cystic fibrosis intestinal organoids. Nat Med 2013;19: Dekkers JF, van der Ent, Cornelis K, Beekman JM. Novel opportunities for CFTR-targeting drug development using organoids. Rare Dis 2013;1:e Dekkers R, Vijftigschild L, Vonk A, Kruisselbrink E, de Winter-de Groot K, Janssens H, van der Ent C, Beekman J. A bioassay using intestinal organoids to measure CFTR modulators in human plasma. J Cyst Fibros 2015;14: