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Felix Ratjen

Title: Paediatric Respirologist, Division of Respiratory Medicine
Designations: MD, FRCP(C)
Phone: 416-813-6167
Alternate Contact Name: Sara Chowns
Alternate Phone: 416-813-7654 ext. 305130
Alternate Email:
U of T Positions: Professor, Department of Paediatrics

Research Positions

Program Head and Senior Scientist
Translational Medicine


Dr. Felix Ratjen is the Division Chief of Paediatric Respiratory Medicine at The Hospital for Sick Children  (SickKids) and Professor of Paediatrics at the University of Toronto. He is also Program Head and Senior Scientist in the Translational Medicine research program at SickKids Research Institute.  He is co-leading the CF Centre at SickKids with Christine Bear, another Senior Scientist in the Molecular Medicine Program.

Dr. Ratjen completed a majority of his medical education in Germany, along with a research fellowship at the Children's Hospital in Boston. He subsequently worked at the University of Essen, where he was appointed Deputy Chief of the Department of Paediatrics in 1998 and Professor of Paediatrics in 2001. Until 2005 he was the chief executive of the scientific board of the German CF foundation before relocating in Canada in the same year. He also is involved in the organizing committees of the major respiratory meetings (American Thoracic Society, European Respiratory Society and the North American CF conference), works on multiple grant review panels is a member of the several editorial boards including the American Journal of Respiratory and Critical Care Medicine, Thorax, Pediatric Pulmonology Lancet Respiratory Medicine and the Journal of Cystic Fibrosis. 


Dr. Ratjen is conducting multiple clinical trials addressing cystic fibrosis lung disease including new therapeutic strategies to target the underlying defect, treatment of airway infections such as first infection with Pseudomonas aeruginosa, airway inflammation and other important aspects of the disease. While some of these studies are single centre studies within the CF centre at SickKids or in collaboration with the adult centre at St. Michael’s Hospital, many of them include both national and international collaborations with centres in Canada, the U.S., Europe and Australia. In addition, he is involved in developing and validating new outcome measures to quantify important aspects of CF lung disease that can be utilized in clinical trials. He also studies other lung diseases and over the recent years has developed an interest in the clinical evaluation of Hereditary Hemorrhagic Telangiectasia (HHT), for which he is leading one of the largest dedicated pediatric clinics.

Education and experience

  • 1986: Doctor of Medicine, Johann Wolfgang Goethe University in Frankfurt a.M, Germany
  • 1987–1989: Research Fellowship, Pediatric Pulmonary Medicine, Children's Hospital, Harvard Medical School, Boston, Massachusetts
  • 1988–1993: Paediatric training, Children’s Hospital, University of Essen
  • 1996: PhD, Habilitation Paediatrics, University of Essen, Germany
  • 2009: Leadership Training, University of Toronto, Rotman School of Business


  • 2005: Adolft-Windorfer Prize for Outstanding Research in CF
  • 2005–2020: SickKids Foundation, H.E Sellers Chairholder
  • 2012: Queen Elizabeth II Diamond Jubilee Medal for service to Cystic Fibrosis Patients
  • 2014: Fellowship of the ERS (FERS)
  • 2018: Maestro de Pulmonologica Pediatricia Latinamericana

Associate Editor

  • Journal of Cystic Fibrosis
  • Canadian Journal Respiratory and Critical Care Medicine
  • Cochrane CF and Rare Disease Group

Editorial Boards

  • American Journal of Respiratory and Critical Care Medicine
  • Lancet Respiratory Medicine
  • Pediatric Pulmonology
  • Thorax


  1. Efficacy and safety of lumacaftor and ivacaftor in patients aged 6-11 years with cystic fibrosis homozygous for F508del-CFTR: a randomised, placebo-controlled phase 3 trial. Ratjen F, Hug C, Marigowda G, Tian S, Huang X, Stanojevic S, Milla CE, Robinson PD, Waltz D, Davies JC; VX14-809-109 investigator group.Lancet Respir Med. 2017 Jul;5(7):557-567. 
  2. Hyperpolarised 129Xe magnetic resonance imaging to monitor treatment response in children with cystic fibrosis. Rayment JH, Couch MJ, McDonald N, Kanhere N, Manson D, Santyr G, Ratjen F.Eur Respir J. 2019 May 2;53(5):1802188.
  3. Changes in Lung Clearance Index in Preschool-aged Patients with Cystic Fibrosis Treated with Ivacaftor (GOAL): A Clinical Trial. Ratjen F, Klingel M, Black P, Powers MR, Grasemann H, Solomon M, Sagel SD, Donaldson SH, Rowe SM, Rosenfeld M.Am J Respir Crit Care Med. 2018 Aug 15;198(4):526-528. 
  4. Inhaled hypertonic saline in preschool children with cystic fibrosis (SHIP): a multicentre, randomised, double-blind, placebo-controlled trial. Ratjen F, Davis SD, Stanojevic S, Kronmal RA, Hinckley Stukovsky KD, Jorgensen N, Rosenfeld M; SHIP Study Group. Lancet Respir Med. 2019 Sep;7(9):802-809. doi: 10.1016/S2213-2600(19)30187-0. Epub 2019 Jun
  5. The future of cystic fibrosis care: a global perspective. Bell SC, Mall MA, Gutierrez H, Macek M, Madge S, Davies JC, Burgel PR, Tullis E, Castaños C, Castellani C, Byrnes CA, Cathcart F, Chotirmall SH, Cosgriff R, Eichler I, Fajac I, Goss CH, Drevinek P, Farrell PM, Gravelle AM, Havermans T, Mayer-Hamblett N, Kashirskaya N, Kerem E, Mathew JL, McKone EF, Naehrlich L, Nasr SZ, Oates GR, O'Neill C, Pypops U, Raraigh KS, Rowe SM, Southern KW, Sivam S, Stephenson AL, Zampoli M, Ratjen F.  Lancet Respir Med. 2020 Jan;8(1):65-124. 

2012–2017: NIH – National Heart Lung and Blood Institute Lung Clearance Index (LCI) as a marker of early lung disease in preschool children.  
1,738,992.71 USD
Principal Investigator  

2014–2018: Cystic Fibrosis Foundation Therapeutics Inc. SHIP (Saline Hypertonic in Preschoolers) Study.
2,058,043 USD 
Co-Principal Investigator

2015–2024: Sick Kids Foundation – Cystic Fibrosis Canada Program for Individualized CF Therapy 
7,500,000 CAD 
Co-Pricipal Investigators: F Ratjen, C Bear

2018–2022: Genome Canada – LSARP Personalized Therapy for Individuals with Cystic Fibrosis
$10,073,757 CAD ($5,000,000 GC contribution) 
Principal Investigator: Felix Ratjen 
Co-Investigators: L Strug, C Bear, B Knoppers, G Keller, J Rossant, M Krahn, J Kimmelman

2019–2022: Cystic Fibrosis Foundation Hyperpolarized Imaging for New Therapies (HyPOINT) in Pediatric CF  
774,379.00 USD 
Principal Investigator: J Woods 
Co-Investigator: F Ratjen

Relevant pages

Ratjen Lab

The Ratjen Lab's research focuses on evaluating novel treatments, designing new ways to conduct research and investigating how we can better measure and monitor lung function in young children.

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