Anti-thymocyte globulin exposure in patients with diffuse cutaneous systemic sclerosis undergoing autologous haematopoietic stem cell transplantation

Yu-Hsiang Chiu; Anouk Drijver; Rick Admiraal; Anna van Rhenen; Stefan Nierkens; Jacob M van Laar; Julia Spierings

doi:10.1177/23971983231188232

Anti-thymocyte globulin exposure in patients with diffuse cutaneous systemic sclerosis undergoing autologous haematopoietic stem cell transplantation

J Scleroderma Relat Disord. 2023 Oct;8(3):241-246. doi: 10.1177/23971983231188232. Epub 2023 Jul 24.

Authors

Yu-Hsiang Chiu^{1

2}, Anouk Drijver¹, Rick Admiraal³, Anna van Rhenen⁴, Stefan Nierkens^{3

5}, Jacob M van Laar¹, Julia Spierings¹

Affiliations

¹ Department of Rheumatology and Clinical Immunology, University Medical Center Utrecht, Utrecht, The Netherlands.
² Division of Rheumatology/Immunology/Allergy, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei.
³ Princess Máxima Center for Paediatric Oncology, Utrecht, The Netherlands.
⁴ Department of Haematology, University Medical Center Utrecht, Utrecht, The Netherlands.
⁵ Centre for Translational Immunology, University Medical Center Utrecht, Utrecht, The Netherlands.

Abstract

Introduction: Autologous haematopoietic stem cell transplantation improves event-free survival and lung function and reduces skin thickening in patients with progressive diffuse cutaneous systemic sclerosis. Anti-thymocyte globulin is a key lymphoablative constituent of conditioning protocols and is administered in a weight-based dosage. However, whether anti-thymocyte globulin exposure contributes to response to autologous haematopoietic stem cell transplantation and lymphocyte reconstitution in diffuse cutaneous systemic sclerosis patients is unknown. We aimed to explore the relationship between anti-thymocyte globulin exposure, lymphocyte reconstitution and treatment response in diffuse cutaneous systemic sclerosis patients undergoing autologous haematopoietic stem cell transplantation.

Methods: A retrospective cohort of 15 diffuse cutaneous systemic sclerosis patients undergoing autologous haematopoietic stem cell transplantation was performed. Clinical characteristics and routine laboratory results were retrieved from electronic medical records. Anti-thymocyte globulin concentrations were measured in cryopreserved plasma samples at four time points (day 1 and week 1, 2 and 4) after stem cell reinfusion. Anti-thymocyte globulin exposure was estimated using a validated population pharmacokinetic model.

Results: During a median follow-up of 45 months (interquartile range 19-66), 11 (73%) patients had a treatment response, and 4 (27%) were non-responders. Although all patients received the same weight-based anti-thymocyte globulin dosage, 7.5 mg/kg divided over 3 days, anti-thymocyte globulin exposure varied. Anti-thymocyte globulin exposure was higher in responders than in non-responders (163 AU*day/mL (interquartile range 153-183) and 137 AU*day/mL (interquartile range 101-149), respectively, p = .026). Anti-thymocyte globulin exposure was not correlated with lymphocyte reconstitution or infection rate.

Conclusion: Weight-based dosing of anti-thymocyte globulin results in variable anti-thymocyte globulin exposure and treatment response across individuals.

Keywords: Systemic sclerosis; anti-thymocyte globulin; haematopoietic stem cell transplantation; immune reconstitution; scleroderma.