Mary Kay Koenig ¹ Vincenzo Leuzzi ² Riadh Gouider ³ Eppie M Yiu ⁴ Barbara Pietrucha ⁵ Asbjørg Stray-Pedersen ⁶ Susan L Perlman ⁷ Steve W Wu ⁸ Trudy Burgers ⁹ Rupam Borgohain ¹⁰ Rukmini Mridula Kandadai ¹¹ Isabelle Meyts ¹² Giorgia Bucciol ¹³ Anaita Udwadia-Hegde ¹⁴ Ravi Yadav ¹⁵ Donna Roberts ¹⁶ Aaron Dane ¹⁷ Maureen Roden ¹⁸ Dirk Thye ¹⁸ Biljana Horn ^18* Howard Lederman ¹⁹ William Whitehouse ²⁰

• ¹ Department of Pediatrics, Division of Child and Adolescent Neurology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States
• ² Department of Human Neuroscience, Unit of Child Neurology and Psychiatry, La Sapienza University, Rome, Italy
• ³ Department of Neurology, Clinical Investigation Center Neurosciences and Mental Health, Razi University Hospital, Faculty of Medicine, Tunis El Manar University, Tunis, Tunis, Tunisia
• ⁴ Department of Neurology, Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
• ⁵ Department of Clinical Immunology, Children's Memorial Health Institute (IPCZD), Warsaw, Masovian, Poland
• ⁶ Norwegian National Institute Unit for Newborn Screening, Division of Pediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Nordland, Norway
• ⁷ Department of Neurology, University of California Los Angeles Medical Center, Los Angeles, United States
• ⁸ Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
• ⁹ Department of Habilitation, Innlandet Hospital, Ottestad, Norway
• ¹⁰ Department of Neurology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India
• ¹¹ Parkinson's Disease and Movement Disorder Research Center, Citi Neuro Center, Hyderabad, India
• ¹² Department of Pediatrics and Department of Microbiology, Immunology and Transplantation, University Hospitals Leuven, Leuven, Brussels, Belgium
• ¹³ Department of Pediatrics and Department of Microbiology, Immunology and Transplantation, University Hospitals of Leuven, Leuven, Belgium
• ¹⁴ Department of Neurology, Jaslok Hospital and Research Center, Mumbai, India
• ¹⁵ Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, Karnataka, India
• ¹⁶ Gem Programming Solutions, Macclesfield, United Kingdom
• ¹⁷ Danestat Consulting Limited, Macclesfield, United Kingdom
• ¹⁸ Quince Therapeutics, South San Francisco, California, United States
• ¹⁹ Division of Pediatric Allergy and Immunology, Johns Hopkins Hospital, Baltimore, United States
• ²⁰ School of Medicine University of Nottingham, Nottingham, United Kingdom

Background: Dexamethasone sodium phosphate (DSP) encapsulated in autologous erythrocytes (EryDex) was developed as an alternative to standard glucocorticoids in an effort to eliminate chronic steroid toxicity while preserving efficacy. The primary objective of this report is to describe the safety of long-term use of EryDex in treatment of pediatric patients with ataxia telangiectasia.Methods: This is a post-hoc analysis of patients treated with EryDex for a minimum of 24 months in two prospective clinical trials. Outcomes include adverse events, growth, hemoglobin and serum iron, glucose levels, HbA1c, CD4+ lymphocytes, and bone mineral density.Results: Sixty-eight patients completed a minimum of two years of treatment with EryDex (mean treatment length 39 ± 11 months). Treatment-emergent adverse events (TEAE), reported in 67 (99%) out of 68 patients, were typically mild and did not cause discontinuation of treatment or death. Treatment-related TEAE were noted in 48 (71%) patients. Notable adverse events included transient pruritus reported in 23 (34%) patients and findings of low serum iron reported in 27 (40%) patients, while at baseline one fifth of patients had low serum iron. Anemia was reported in 9 (13%) patients. The mean hemoglobin level changed by -0.8 ± 1.0 g/dL after 6 months of therapy without subsequent decline. Longitudinal height and weight mean z-scores showed minimal change from baseline to month 24 for height (-0.06 ± 0.49), weight (-0.02 ± 0.71), and body mass index (0.03 ± 0.87). The mean bone mineral density (BMD) z-score showed a decline of 0.4 points over the 24 months of treatment. Values for glucose, HbA1c, cortisol, and CD4+ lymphocyte counts did not show clinically significant changes during prolonged treatment with EryDex.The most common treatment-related adverse events were transient infusion-related pruritus and iron deficiency. There was a decline in BMD which could not be distinguished from the natural course of disease. There were no adverse effects on height, weight and body mass index noted, as documented by stable z-scores throughout the 2 years of treatment. Adverse events typically observed with prolonged glucocorticoid use such as Cushingoid features, weight gain, hypertension, hirsutism, diabetes or stunted growth were rarely reported.