Although the first patients were transplanted in the late 1990s [3, 4], it has only really been in recent years that aHSCT has increasingly been gaining interest as a therapeutic option for immune reconstitution in MS. Patients who may be considered for transplantation have a disease form with an active inflammatory component and in particular relapsing-remitting MS (RRMS). In other words, for patients who are experiencing frequent (> 2 per year) relapses or have had a relapse and then at a separate point within the past 12 months have also had evidence of disease activity on magnetic resonance imaging (MRI). In addition, this must have occurred despite treatment with one full course of disease-modifying therapy (DMT). In very exceptional cases for patients with a “malignant” or “aggressive” disease course, aHSCT can be considered prior to a full course of DMT if severe disability has developed within the past 12 months. Evidence suggests that younger patients (< 45 years) with a shorter disease duration (< 10 years) and minimal disability (EDSS ≤ 5.5) have better outcomes, although aHSCT may be considered for progressive forms of MS with ongoing active inflammation, i.e., relapses [1, 2]. aHSCT involves the five main stages: stringent patient selection and pre-transplantation care; mobilisation and harvesting of haematopoietic stem cells (HSC) from the bone marrow with or without further stem cell selection in the laboratory; complete or incomplete ablation of the bone marrow, often also immune cells in the peripheral circulation; reinfusion of HSC; engraftment of the newly transplanted HSC and post-transplantation care. The therapy used to ablate bone marrow and peripheral immune cells may be classified according to its intensity (high, intermediate, and low). In our study and in line with the EBMT, we identified that intermediate-intensity conditioning regimens were used most often and therefore have the most evidence supporting their use. Outcomes do appear promising, but trials were heterogenous and not enough randomised, controlled trials have been performed to establish whether aHSCT is a better option than other therapies for this select patient group. It is therefore critical to report cases of aHSCT for MS to a patient registry, for example that of the EBMT. Mortality, infertility, secondary autoimmune disease, secondary malignancy, and immunity must be discussed in depth with patients prior to aHSCT, in addition to side effects such as infection, viral reactivation, and fever. aHSCT remains a promising therapeutic option that may perhaps offer patients a long, perhaps in some cases life-long, period of remission from disease. We aim to continue investigating this therapeutic option and thereby be able to offer patients with MS the best possible care.
References:
1. Willison AG, Ruck T, Lenz G, Hartung HP, Meuth SG. The current standing of autologous haematopoietic stem cell transplantation for the treatment of multiple sclerosis. J Neurol. 2022.10.1007/s00415-022-11063-5.
Professor Sven Meuth