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Most patients with relapsing-remitting multiple sclerosis (RRMS) treated with autologous hematopoietic stem cell transplantation (AHSCT) showed no evidence of disease activity (NEDA) for 5 to 10 years, observational data showed.

Of 174 Swedish patients treated with AHSCT, estimated NEDA was 73% (95% CI 66-81) at 5 years and 65% (95% CI 57-75) at 10 years, reported Joachim Burman, MD, PhD, of Uppsala University in Sweden, and co-authors in the .

A total of 149 patients had baseline disability. Over a median follow-up of 5.5 years, 54% improved, 37% were stable, and 9% deteriorated.

"The incidence of severe adverse events was low, and there was no record of treatment-related mortality, suggesting that AHSCT can be safely implemented within routine healthcare," the researchers wrote.

The findings support the sole randomized controlled trial conducted to date, they added.

High-dose chemotherapy followed by AHSCT has been used to treat MS since the 1990s, Burman and colleagues observed. "The goal of AHSCT is to reset the immune system by eliminating autoreactive lymphocytes, in order to induce long-term remission," they wrote.

The Swedish Board of Health and Welfare approved AHSCT for MS in 2016, but in most countries, it has not yet been integrated into clinical guidelines. In 2020, the National Multiple Sclerosis Society (NMSS) about using AHSCT in MS.

Consensus is emerging about which patients are best candidates for AHSCT, and questions remain about the ideal protocol, especially the best conditioning regimen to kill immune cells, the NMSS said. The ongoing , which compares investigational AHSCT against high-efficacy biologic drugs for treatment-resistant relapsing MS in the U.S. and U.K. may yield some answers.

To examine the efficacy of AHSCT, Burman and colleagues conducted a retrospective analysis of prospectively collected data from the Swedish MS registry. They assessed safety by reviewing patients' electronic medical records for 100 days after the procedure. Patients were treated between 2004 and 2020.

Of 174 people in the study, 64% were women. Mean age at AHSCT was 31, and median disease duration was 3.4 years. NEDA was defined as the absence of new relapses, new or enlarged lesions on MRI, and confirmed disability worsening.

The annualized relapse rate was 1.7 in the year before AHSCT and 0.035 during the follow-up period. All instances of confirmed disability worsening occurred independently of relapses.

The median (EDSS) score at baseline was 3.5 on a scale of from 0 (indicating no disability) to 10. At the last follow-up, the median EDSS was 2, significantly lower than the baseline score (P<0.0001).

Patients received a median of two disease-modifying treatments before AHSCT, and 23 patients were previously untreated. After a median of 2.9 years, 20 patients received a disease-modifying drug after AHSCT. After a median of 4.1 years, 10 patients transitioned from RRMS to secondary progressive MS.

Febrile neutropenia was the most common side effect, experienced by 68% of patients. Overall, five patients were required intensive care, and 61 developed a bacterial infection within 100 days of treatment.

Herpes zoster reactivation was documented in three patients, and three patients had a confirmed localized fungal infection. No patient developed Epstein-Barr virus-related or cytomegalovirus-related disease. No treatment-related deaths were reported.

Early trials of AHSCT raised concerns around safety, and "it is important to note that no patients died in this study," observed Ruth Dobson, PhD, of Queen Mary University London in England, who posted comments on the U.K.'s .

However, five patients needed ICU admission and most patients required treatment of infections during their treatment, Dobson pointed out. "This would be in keeping with other, more recent studies, and highlights the need to select patients carefully for these kinds of treatments," she wrote.

"At 10 years, 65% patients had no evidence of disease activity, 75% at 5 years," she noted. "This underlines the efficacy of this treatment in people with MS. We do need more comparative evidence, such as is being generated with (a U.K. study of [autologous stem cell transplantation] vs high-efficacy treatments), in order to be able to contextualize the efficacy against other treatments that are now in increasingly common use."

The absence of a control group in their study precluded definitive conclusions about the effect size of AHSCT compared with other RRMS treatments, Burman and co-authors noted. In addition, some data may have been missing which may have led to underreporting, primarily of adverse events, they acknowledged.

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