Autologous hematopoietic stem cell transplantation vs low-dose immunosuppression in secondary-progressive multiple sclerosis

Autologous haematopoietic stem cell transplantation for treatment of multiple sclerosis and neuromyelitis optica spectrum disorder - recommendations from ECTRIMS and the EBMT

Autologous haematopoietic stem cell transplantation (AHSCT) is a treatment option for relapsing forms of multiple sclerosis (MS) that are refractory to disease-modifying therapy (DMT). AHSCT after failure of high-efficacy DMT in aggressive forms of relapsing-remitting MS is a generally accepted indication, yet the optimal placement of this approach in the treatment sequence is not universally agreed upon. Uncertainties also remain with respect to other indications, such as in rapidly evolving, severe, treatment-naive MS, progressive MS, and neuromyelitis optica spectrum disorder (NMOSD). Furthermore, treatment and monitoring protocols, rehabilitation and other supportive care before and after AHSCT need to be optimized. To address these issues, we convened a European Committee for Treatment and Research in Multiple Sclerosis Focused Workshop in partnership with the European Society for Blood and Marrow Transplantation Autoimmune Diseases Working Party, in which evidence and key questions were presented and discussed by experts in these diseases and in AHSCT. Based on the workshop output and subsequent written interactions, this Consensus Statement provides practical guidance and recommendations on the use of AHSCT in MS and NMOSD. Recommendations are based on the available evidence, or on consensus when evidence was insufficient. We summarize the key evidence, report the final recommendations, and identify areas for further research.

Effects of multiple treatments with stem cell therapy in patients with multiple sclerosis

OBJECTIVE

This study was to evaluate the effectiveness of stem cell therapies (AHSCT: autologous hematopoietic stem cell transplantation and MSCs: mesenchymal stem cells) compared to non-stem cell therapies in multiple sclerosis (MS) patients.

DESIGN

Clinical trials to investigate the therapeutic effects of stem cells therapy was searched by PubMed, Embase, Web of Science, and the Cochrane Library. The Cochrane Risk of Bias Assessment Tool and data analysis software will be applied.

RESULTS

Data were collected between the earliest available date and August 2023. Ten studies were included, with a sample size of 5288 used in the studies. Results showed that human umbilical cord-derived mesenchymal stem cells reduced the Annualized Relapse Rate (SUCRA: 70.9 %) and Expanded Disability Status Scale (SUCRA: 77.1 %) of MS patients, AHSCT reduced mortality rate (SUCRA: 69.8 %), autologous peripheral blood stem cell transplantation (APBSCT) reduced recurrence rate (SUCRA: 86.7 %) and improved No Evidence of Disease Activity-3 (SUCRA: 92.8 %).

CONCLUSION

At present, AHSCT and MSCs have been demonstrated to reduce the recurrence rate of multiple sclerosis and improve disability, particularly in the case of hUC-MSCs. However, APBSCT and AHSCT in the context of the NEDA-3 criteria have not yielded the desired outcomes.

Exploring the therapeutic potential of autologous hematopoietic stem cell transplantation in progressive multiple sclerosis-a systematic review

BACKGROUND AND PURPOSE

The aim was to determine the value of autologous haematopoietic stem cell transplantation (aHSCT) as a therapeutic intervention for progressive multiple sclerosis (PMS) based on a systematic review of the current literature.

METHODS

All studies from the databases PubMed and Google Scholar published in English before February 2024 which provided individual data for PMS patients were systematically reviewed. PICO was defined as population (P), primary progressive MS and secondary progressive MS patients; intervention (I), treatment with aHSCT; comparison (C), none, disease-modifying therapy treated/relapsing-remitting MS cohorts if available; outcome (O), transplant-related mortality, progression-free survival (PFS) and no evidence of disease activity.

RESULTS

A total of 15 studies met the criteria including 665 patients with PMS (74 primary progressive MS, 591 secondary progressive MS) and 801 patients with relapsing-remitting MS as controls. PFS data were available for 647 patients. PMS patients showed more severe disability at baseline than relapsing-remitting MS patients. The average transplant-related mortality for PMS in 10 studies was 1.9%, with 10 deaths in 528 patients. PFS ranged from 0% to 78% in PMS groups 5 years after treatment initiation, demonstrating a high variability. No evidence of disease activity scores at 5 years ranged from 0% to 75%.

CONCLUSION

Based on the available data, aHSCT does not halt progression in people with PMS. However, there appears to be evidence of improved outcome in selected patients. Due to the heterogeneity of the available data, more comprehensive clinical trials assessing the efficacy of aHSCT across different patient groups are urgently needed to reduce variability and improve patient stratification.

Multiple sclerosis: a narrative overview of current pharmacotherapies and emerging treatment prospects

Multiple sclerosis (MS) is a chronic autoimmune disease characterized by pathological processes of demyelination, subsequent axonal loss, and neurodegeneration within the central nervous system. Despite the availability of numerous disease-modifying therapies that effectively manage this condition, there is an emerging need to identify novel therapeutic targets, particularly for progressive forms of MS. Based on contemporary insights into disease pathophysiology, ongoing efforts are directed toward developing innovative treatment modalities. Primarily, monoclonal antibodies have been extensively investigated for their efficacy in influencing specific pathological pathways not yet targeted. Emerging approaches emphasizing cellular mechanisms, such as chimeric antigen receptor T cell therapy targeting immunological cells, are attracting increasing interest. The evolving understanding of microglia and the involvement of ferroptotic mechanisms in MS pathogenesis presents further avenues for targeted therapies. Moreover, innovative treatment strategies extend beyond conventional approaches to encompass interventions that target alterations in microbiota composition and dietary modifications. These adjunctive therapies hold promise as complementary methods for the holistic management of MS. This narrative review aims to summarize current therapies and outline potential treatment methods for individuals with MS.

Spinal cord size as promising biomarker of disability outcomes after hematopoietic stem cell transplantation in multiple sclerosis

BACKGROUND

Biomarkers predictive of disability outcomes in individual multiple sclerosis (MS) patients undergoing autologous haematopoietic stem cell transplantation (AHSCT) are currently lacking. As correlations between spinal cord atrophy and clinical disability in MS were previously described, in this study spinal cord size was investigated in MS patients treated with AHSCT, exploring whether baseline spinal cord volume may predict disability progression after AHSCT.

METHODS

relapsing-remitting (RR-) and secondary-progressive (SP-) MS patients treated with AHSCT (BEAM/ATG regimen) at a single academic centre in Florence, who performed at least two standardized brain magnetic resonance imaging (MRIs) scans (acquired between one-year pre-AHSCT to 5 years after AHSCT) were included. Cervical spinal cord atrophy was estimated as upper cervical spinal cord cross-sectional area (SCCSA). Brain volume loss (BVL) was analysed at the same timepoints.

RESULTS

Eleven (8 RR-; 3 SP-) MS patients were included. Over a median follow-up of 66 (range 37 - 100) months, no relapses nor brain MRI activity were observed; disability progressed in 2 cases (both SP-MS). Baseline SCCSA was associated with EDSS change between pre- and one-year post-AHSCT. Compared to patients who stabilized, patients who progressed after AHSCT tended to have lower SCCSA at C4 level at baseline and year 1 after AHSCT. Longitudinal changes in SCCSA or BVL did not correlate with EDSS change.

CONCLUSIONS

Baseline pre-AHSCT SCCSA, but not its longitudinal changes nor BVL, predicted EDSS change within the two years following AHSCT. SCCSA may represent a biomarker of treatment response and a promising screening tool for assessing patient eligibility for high-impact treatments such as AHSCT.

Effectiveness of autologous haematopoietic stem cell transplantation versus natalizumab in progressive multiple sclerosis

BACKGROUND

Natalizumab was not shown to modify disability in progressive multiple sclerosis (MS). This matched observational study compared the effectiveness of autologous haematopoietic stem cell transplantation (AHSCT) with natalizumab in progressive MS.

METHODS

Patients with primary/secondary progressive MS from seven AHSCT MS centres and the MSBase registry, treated with AHSCT or natalizumab, were matched on a propensity score derived from sex, age, Expanded Disability Status Scale (EDSS), number of relapses 12/24 months before baseline, time from MS onset, the most effective prior therapy and country. The pairwise-censored groups were compared on hazards of 6-month confirmed EDSS worsening and improvement, relapses and annualised relapse rates (ARRs), using Andersen-Gill proportional hazards models and conditional negative binomial model.

RESULTS

39 patients treated with AHSCT (37 with secondary progressive MS, mean age 37 years, EDSS 5.7, 28% with recent disability progression, ARR 0.54 during the preceding year) were matched with 65 patients treated with natalizumab. The study found no evidence for difference in hazards of confirmed EDSS worsening (HR 1.49, 95% CI 0.70 to 3.14) and improvement (HR 1.50, 95% CI 0.22 to 10.29) between AHSCT and natalizumab over up to 4 years. The relapse activity was also similar while treated with AHSCT and natalizumab (ARR: mean±SD 0.08±0.28 vs 0.08±0.25; HR 1.05, 95% CI 0.39 to 2.82). In the AHSCT group, 3 patients experienced febrile neutropenia during mobilisation, 9 patients experienced serum sickness, 6 patients required intensive care unit admission and 36 patients experienced complications after discharge. No treatment-related deaths were reported.

CONCLUSION

This study does not support the use of AHSCT to control disability in progressive MS with advanced disability and low relapse activity.

Clinical Progress in Hepatic Targeting for Novel Prophylactic Therapies in Hereditary Angioedema

Hereditary angioedema (HAE) is typically caused by a deficiency of the protease inhibitor C1 inhibitor (C1INH). The absence of C1INH activity on plasma kallikrein and factor XIIa leads to overproduction of the vasoactive peptide bradykinin, with resulting angioedema. As the primary site of C1INH and prekallikrein production, the liver is recognized as an important therapeutic target in HAE, leading to the development of hepatic-focused treatment strategies such as GalNAc-conjugated antisense technology and gene modification. This report reviews currently available data on hepatic-focused interventions for HAE that have advanced into human trials. Donidalorsen is an investigational GalNAc3-conjugated antisense oligonucleotide that binds to prekallikrein mRNA in the liver and reduces the expression of prekallikrein. Phase 2 data with subcutaneous donidalorsen demonstrated a significant reduction in HAE attack rate compared with placebo. Phase 3 trials are underway. ADX-324 is a GalNAc3-conjugated short-interfering RNA being investigated in HAE. BMN 331 is an investigational AAV5-based gene therapy vector that expresses wild-type human C1INH and is targeted to hepatocytes. A single intravenous dose of BMN 331 is intended to replace the defective SERPING1 gene and enable patients to produce functional C1INH. A first-in-human phase 1/2 study is ongoing with BMN 331. NTLA-2002 is an investigational in vivo clustered regularly interspaced short palindromic repeats/Cas9-based therapy designed to knock out the prekallikrein-coding KLKB1 gene in hepatocytes; a phase 1/2 study is ongoing. Findings from these and other ongoing studies are highly anticipated with the expectation of expanding the array of treatment options in HAE.

Benefits of aHSCT over alemtuzumab in patients with multiple sclerosis besides disability and relapses: Sustained improvement in cognition and quality of life

BACKGROUND

Autologous hematopoietic stem cell transplantation (aHSCT) exhibits promising results for multiple sclerosis (MS) in the short term. We investigated the long-term outcome differences in disease progression and cognitive impairment after aHSCT and alemtuzumab treatment.

METHODS

20 patients receiving aHSCT and 21 patients treated with alemtuzumab between 2007 and 2020 were included in this monocentric observational cohort study. The primary objective was to compare the outcome of both groups with regards to achieving No Evidence of Disease Activity (NEDA-3), defined by the absence of relapses, EDSS progression, and MRI activity. Secondary endpoints in the study included the assessment of neurocognitive functioning, quality of life (QoL), Multiple Sclerosis Functional Composite (MSFC), and EDSS improvement.

RESULTS

Baseline characteristics between both groups were comparable, except for a longer disease duration in the alemtuzumab group of 11.3 years compared to 5.4 years in aHSCT-treated patients (p = 0.002) and a longer mean follow-up time in the aHSCT cohort of 9.0 (range 2.8-15.7) years compared to 5.9 years (range 0.9-9.2) in alemtuzumab patients. NEDA-3 was more frequently observed in the aHSCT group with 75.0 % and 55.0 % at five and 10 years, respectively, than in the alemtuzumab group with only 40.0 % at five years (p = 0.012). Relapse free survival was higher in the aHSCT group (p < 0.001). None of the aHSCT-treated patients showed new T2-lesions six months after therapy initiation until the end of the observational period in contrast to 35.0 % of the alemtuzumab-treated patients showing new T2-lesions (95 %CI 14.2-98.9, p = 0.002). aHSCT-treated patients showed significantly improved cognitive performance in five out of 12 cognitive tests whereas alemtuzumab treated patients deteriorated in four out of 12 tests. Quality of life remained on a constant level for up to 10 years in patients receiving aHSCT with improved scores for the subscale fatigue (p = 0.013).

CONCLUSION

aHSCT seems to be superior to alemtuzumab in maintaining long-term NEDA-3 status, improving cognition and stabilizing quality of life for up to 10 years.

Current knowledge on multiple sclerosis pathophysiology, disability progression assessment and treatment options, and the role of autologous hematopoietic stem cell transplantation

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) that affects nearly 2.8 million people each year. MS distinguishes three main types: relapsing-remitting MS (RRMS), secondary progressive MS (SPMS) and primary progressive MS (PPMS). RRMS is the most common type, with the majority of patients eventually progressing to SPMS, in which neurological development is constant, whereas PPMS is characterized by a progressive course from disease onset. New or additional insights into the role of effector and regulatory cells of the immune and CNS systems, Epstein-Barr virus (EBV) infection, and the microbiome in the pathophysiology of MS have emerged, which may lead to the development of more targeted therapies that can halt or reverse neurodegeneration. Depending on the type and severity of the disease, various disease-modifying therapies (DMTs) are currently used for RRMS/SPMS and PPMS. As a last resort, and especially in highly active RRMS that does not respond to DMTs, autologous hematopoietic stem cell transplantation (AHSCT) is performed and has shown good results in reducing neuroinflammation. Nevertheless, the question of its potential role in preventing disability progression remains open. The aim of this review is to provide a comprehensive update on MS pathophysiology, assessment of MS disability progression and current treatments, and to examine the potential role of AHSCT in preventing disability progression.

Stem Cell Transplantation for Multiple Sclerosis: A 2023 Review of Published Studies

This comprehensive literature review underscores the potential of stem cell transplantation (SCT) as a therapeutic intervention for multiple sclerosis (MS). By amalgamating evidence from various sources, including randomized controlled trials (RCTs), observational, retrospective, and comparative studies, this review offers a holistic understanding of SCT's effectiveness, safety, and feasibility in diverse contexts of MS management. SCT has shown promise in mitigating disease activity and progression, particularly in relapsing-remitting MS (RRMS). RCTs like the high dose immunoablation and autologous hematopoietic stem cell transplantation in MS (ASTIMS) versus mitoxantrone therapy in severe multiple sclerosis and multiple sclerosis international stem cell transplant (MIST) trials reveal SCT's capacity to reduce new lesion occurrences and inflammatory activity. However, variability exists in disability score improvements among these studies. Observational and retrospective investigations further affirm SCT's potential, highlighting decreased relapse rates, enhanced expanded disability status scale (EDSS) scores, and a noteworthy proportion of patients achieving no evidence of disease activity (NEDA). The initial literature search using all of the search items produced a total of 3,636 articles. After title, abstract, and article type screening and article retrieving, 147 articles were assessed for eligibility using the inclusion criteria. At the end of the literature search, 37 articles met the eligibility criteria. They were included in our review according to preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Patients treated with hematopoietic stem cell transplantation (HSCT) present lower progression and relapse rates, suppression of inflammatory activity, and a greater reduction in T2 lesions on MRI than those treated with disease-modifying therapies (DMTs). In summary, while SCT presents promise as a therapeutic option for MS, its deployment should be tailored to individual patient characteristics, disease stages, and responses.

Autologous haematopoietic stem cell transplantation for multiple sclerosis: a position paper and registry outline

Background

While substantial progress has been made in the development of disease-modifying medications for multiple sclerosis (MS), a high percentage of treated patients still show progression and persistent inflammatory activity. Autologous haematopoietic stem cell transplantation (AHSCT) aims at eliminating a pathogenic immune repertoire through intense short-term immunosuppression that enables subsequent regeneration of a new and healthy immune system to re-establish immune tolerance for a long period of time. A number of mostly open-label, uncontrolled studies conducted over the past 20 years collected about 4000 cases. They uniformly reported high efficacy of AHSCT in controlling MS inflammatory disease activity, more markedly beneficial in relapsing-remitting MS. Immunological studies provided evidence for qualitative immune resetting following AHSCT. These data and improved safety profiles of transplantation procedures spurred interest in using AHSCT as a treatment option for MS.

Objective

To develop expert consensus recommendations on AHSCT in Germany and outline a registry study project.

Methods

An open call among MS neurologists as well as among experts in stem cell transplantation in Germany started in December 2021 to join a series of virtual meetings.

Results

We provide a consensus-based opinion paper authored by 25 experts on the up-to-date optimal use of AHSCT in managing MS based on the Swiss criteria. Current data indicate that patients who are most likely to benefit from AHSCT have relapsing-remitting MS and are young, ambulatory and have high disease activity. Treatment data with AHSCT will be collected within the German REgistry Cohort of autologous haematopoietic stem CeLl trAnsplantation In MS (RECLAIM).

Conclusion

Further clinical trials, including registry-based analyses, are urgently needed to better define the patient characteristics, efficacy and safety profile of AHSCT compared with other high-efficacy therapies and to optimally position it as a treatment option in different MS disease stages.

Haematopoietic Stem Cell Transplantation for the Treatment of Multiple Sclerosis: Recent Advances

PURPOSE OF REVIEW

Autologous haematopoietic stem cell transplantation (AHSCT) is increasingly considered a treatment option for patients with multiple sclerosis (MS), an autoimmune demyelinating and degenerative disease of the central nervous system (CNS). AHSCT persistently suppresses inflammation and improves the disease course in large proportions of patients with relapsing-remitting (RR) MS. Aim of this article is to review the relevant new knowledge published during the last 3 years.

RECENT FINDINGS

Laboratory studies reported confirmatory and new insights into the immunological and biomarker effects of AHSCT. Retrospective clinical studies confirmed excellent outcomes in RRMS, showing possible superior effectiveness over standard therapies and suggesting a possible benefit in early secondary progressive (SP) MS with inflammatory features. New data on risks of infertility and secondary autoimmunity were also reported. Further evidence on the high effectiveness and acceptable safety of AHSCT strengthens its position as a clinical option for aggressive RRMS. Further research is needed to better define its role in treatment-naïve and progressive forms of MS, ideally within randomised clinical trials (RCTs).

Autologous haematopoietic stem cell transplantation for immune-mediated neurological diseases: what, how, who and why?

In carefully selected patients, autologous haematopoietic stem cell transplantation (HSCT) is a safe, highly effective and cost-saving treatment modality for treatment-resistant, and potentially treatment-naïve, immune-mediated neurological disorders. Although the evidence base has been growing in the last decade, limited understanding has led to confusion, mistrust and increasing use of health tourism. In this article, we discuss what autologous HSCT is, which immune-mediated conditions can be treated with it, how to select patients, what are the expected outcomes and potential adverse effects, and how cost-effective this treatment is.

Hematopoietic Stem Cell Transplantation in People With Active Secondary Progressive Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Uncontrolled evidence suggests that autologous hematopoietic stem cell transplantation (AHSCT) can be effective in people with active secondary progressive multiple sclerosis (SPMS). In this study, we compared the effect of AHSCT with that of other anti-inflammatory disease-modifying therapies (DMTs) on long-term disability worsening in active SPMS.

METHODS

We collected data from the Italian Bone Marrow Transplantation Study Group and the Italian Multiple Sclerosis Register. Patients were considered eligible if treatment had been started after the diagnosis of SPMS. Disability worsening was assessed by the cumulative proportion of patients with a 6-month confirmed disability progression (CDP) according to the Expanded Disability Status Scale (EDSS) score. Key secondary endpoints were the EDSS time trend after treatment start and the prevalence of disability improvement over time. Time to first CDP was assessed by means of proportional hazard Cox regression models. A linear mixed model with a time × treatment group interaction was used to assess the longitudinal EDSS time trends. Prevalence of improvement was estimated using a modified Kaplan-Meier estimator and compared between groups by bootstrapping the area under the curve.

RESULTS

Seventy-nine AHSCT-treated patients and 1975 patients treated with other DMTs (beta interferons, azathioprine, glatiramer-acetate, mitoxantrone, fingolimod, natalizumab, methotrexate, teriflunomide, cyclophosphamide, dimethyl fumarate, and alemtuzumab) were matched to reduce treatment selection bias using propensity score and overlap weighting approaches. Time to first CDP was significantly longer in transplanted patients (hazard ratio [HR] = 0.50; 95% CI = 0.31-0.81; p = 0.005), with 61.7% of transplanted patients free from CPD at 5 years. Accordingly, EDSS time trend over 10 years was higher in patients treated with other DMTs than in AHSCT-treated patients (+0.157 EDSS points per year compared with -0.013 EDSS points per year; interaction p < 0.001). Patients who underwent AHSCT were more likely to experience a sustained disability improvement: 34.7% of patients maintained an improvement (a lower EDSS than baseline) 3 years after transplant vs 4.6% of patients treated by other DMTs (p < 0.001).

DISCUSSION

The use of AHSCT in people with active SPMS is associated with a slowing of disability progression and a higher likelihood of disability improvement compared with standard immunotherapy.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that autologous hematopoietic stem cell transplants prolonged the time to CDP compared with other DMTs.

[Multiple sclerosis: interventions to halt disease : Which patients can be considered for autologous stem cell transplantation]

BACKGROUND

Autologous hematopoietic stem cell transplantation (aHSCT) for treatment of multiple sclerosis (MS) is gaining increasing prominence in the therapeutic landscape. This review article focuses on describing the evidence and European guidelines for aHSCT so that neurologists in Germany can consider this treatment option for appropriate MS patients. In this context, it must be taken into consideration that in every case a cost transfer must be individually applied for.

AIM

To provide information for neurologists considering aHSCT for patients with MS.

MATERIAL AND METHODS

In this narrative review articles from PubMed were pooled and analyzed.

RESULTS AND DISCUSSION

High quality data from randomized, controlled clinical trials are required to compare the efficacy of aHSCT to the currently available highly effective disease-modifying therapies (DMT) so that reliable conclusions can be drawn regarding the relationship between the risks and benefits of aHSCT in MS; however, the studies discussed in this review provide important points of reference for patient selection and the transplantation protocol. Further advice is available from the European Society for Blood and Marrow Transplantation (EBMT) for experienced centers considering aHSCT. The available data and the European guidelines suggest that patients aged less than 45 years, an expanded disability status scale (EDSS) ≤ 5.5, highly active MS, a disease duration of less than 10 years, an ineffective course of DMT or rapidly progressive MS may be eligible for aHSCT and should be referred to an experienced center for further assessment.

The current standing of autologous haematopoietic stem cell transplantation for the treatment of multiple sclerosis

Autologous haematopoietic stem cell transplantation (aHSCT) is gaining traction as a valuable treatment option for patients affected by severe multiple sclerosis (MS), particularly the relapsing–remitting form. We describe the current literature in terms of clinical trials, observational and retrospective studies, as well as immune reconstitution following transplantation, with a focus on the conditioning regimens used for transplantation. The evidence base predominantly consists of non-randomised, uncontrolled clinical trials or data from retrospective or observational cohorts, i.e. very few randomised or controlled trials. Most often, intermediate-intensity conditioning regimens are used, with promising results from both myeloablative and lymphoablative strategies, as well as from regimens that are low and high intensity. Efficacy of transplantation, which is likely secondary to immune reconstitution and restored immune tolerance, is, therefore, not clearly dependent on the intensity of the conditioning regimen. However, the conditioning regimen may well influence the immune response to transplantation. Heterogeneity of conditioning regimens among studies hinders synthesis of the articles assessing post-aHSCT immune system changes. Factors associated with better outcomes were lower Kurtzke Expanded Disability Status Scale, relapsing–remitting MS, younger age, and shorter disease duration at baseline, which supports the guidance for patient selection proposed by the European Society for Blood and Marrow Transplantation. Interestingly, promising outcomes were described for patients with secondary progressive MS by some studies, which may be worth taking into account when considering treatment options for patients with active, progressive disease. Of note, a significant proportion of patients develop autoimmune disease following transplantation, with alemtuzumab-containing regimens associated with the highest incidence.