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Authors; Qiukui Hao, and Aleksandra Grobelna.
Neuromyelitis optica spectrum disorder (NMOSD) (also named neuromyelitis optica or Devic disease) is a rare and relapsing chronic autoimmune disease of the central nervous system characterized by demyelination and axonal damage primarily targeting astrocytes in optic nerves and the spinal cord.1 Neuroimaging characteristics (observed by MRI) and aquaporin-4(AQP4) autoantibodies are important in NMOSD diagnosis and the differential diagnosis from multiple sclerosis and myelin oligodendrocyte glycoprotein antibody-associated diseases.1 The NMOSD incidence (0.037 to 0.73 per 100,000 person-years) and prevalence (0.7 to 10 per 100,000 persons) vary across studies, with the incidence and prevalence reported to be the highest in Afro-Caribbean regions and lowest in Australia and New Zealand.2 In British Columbia, Canada, the mean incidence of NMOSD ranged from 0.14 to 0.60 per 100,000 person-years from 1986 to 2020 in Asian populations.3 Sex and ethnic groups were identified as influencing factors for these epidemiological data.
The median age of NMOSD onset is 32 to 41 years, with the peak incidence in middle-aged adults (30 to 59 years), but it also can affect children and older adults.1,2 The prevalence of NMOSD among females was reported as 2.3 to 7.6 times greater than that among males.2 People with NMOSD suffer from a wide range of symptoms that include severe visual loss, physical disability, pain, bladder dysfunction, intractable vomiting and hiccoughs, or other non-disease-specific symptoms (e.g., muscle, trunk, or leg pain).1 The features of clinical manifestations for NMOSD typically reflect the acute episodes of optic neuritis (optic nerve inflammation), transverse myelitis (spinal cord inflammation), and area postrema syndrome.4 Unlike multiple sclerosis, patients with NMOSD are unlikely to experience a secondary progressive phase of the disease; however, relapse and attacks are closely related to disability and death.1 Over half of the patients with NMOSD will be disabled and approximately one-third of patients will have died within 5 years after the first attack if the disease is left untreated.5
Acute attacks for NMOSD include the first attack and subsequent acute relapses defined as the worsening of original symptoms or the onset of new related symptoms that last for at least 24 hours and occur more than 30 days after the previous attack.6 Severe acute attacks can lead to paraplegia (paralysis of the legs), blindness, respiratory failure, or long-term disabilities.6 The most important goals of the management for NMOSD are to prevent disability and mortality by reducing the duration and severity of acute attacks or the risk of consequential relapses after the first attack.4,6 For all patients with suspected NMOSD acute attack, several clinical practice guidelines recommend a high-dose glucocorticoid pulse as the first-line intervention and plasma exchange as the second-line treatment. Considering relapses could result in accumulated neurologic deficits closely related to poor prognosis, long-term immunotherapy (at least 5 years or lifetime treatment) is generally used once the diagnosis of NMOSD is made or after the management of the acute attacks.7
For long-term immunotherapies, available options include humanized monoclonal antibodies, azathioprine (AZA), mycophenolate mofetil (MMF), methotrexate, mitoxantrone, and oral glucocorticoids.7 Health Canada–approved the humanized monoclonal antibodies eculizumab and satralizumab as immunosuppressive drugs for preventing relapse in people with NMOSD.8 However, due to inconsistency in the limited available evidence, the current clinical practice guidelines have not established the optimal immunotherapies and treatment durations.7 Some clinicians prescribe the off-label use of tocilizumab (TCZ) or rituximab for patients with NMOSD as alternative immunosuppressive drugs.7
TCZ is a humanized monoclonal antibody against the interleukin-6 (IL-6) receptor that is approved in Canada for the treatment of moderately to severely active rheumatoid arthritis.9,10 TCZ also can be used in patients hospitalized with Covid-19 pneumonia and other diseases.11 In patients with NMOSD, IL-6 can stimulate abnormal B-cell response and increase AQP4 autoantibodies that play a crucial role in immunopathogenesis and astrocyte injury.12 TCZ as 1 of the IL-6 inhibitors, had demonstrated immunological effects on immune cells and in reducing the AQP4 antibody levels,13 suggesting it may be a promising immunotherapy option for this condition. The purpose of this report is to review the clinical effectiveness and cost-effectiveness of TCZ for patients with NMOSD compared to alternative pharmacological therapies or no treatment. We also summarized relevant evidence-based guidelines regarding the use of TCZ in patients with NMOSD.
A literature search was conducted by an information specialist on key resources, including MEDLINE, Embase, the Cochrane Database of Systematic Reviews, the International HTA Database, the websites of Canadian and major international health technology agencies, as well as a focused internet search. The search strategy comprised controlled vocabulary, such as the National Library of Medicine’s MeSH (Medical Subject Headings), and keywords. The main search concepts were tocilizumab and neuromyelitis optica spectrum disorder (NMOSD). No filters were applied to limit the retrieval by study type. Where possible, retrieval was limited to the human population. The search was completed on February 2, 2023 and was limited to English-language documents published since January 1, 2018.
One reviewer screened citations and selected studies. In the first level of screening, titles and abstracts were reviewed and potentially relevant articles were retrieved and assessed for inclusion. The final selection of full-text articles was based on the inclusion criteria presented in Table 1.
Selection Criteria.
Articles were excluded if they did not meet the selection criteria outlined in Table 1. We also excluded duplicate publications and citations that were published before 2018. Systematic reviews in which all relevant studies were captured in other more recent or more comprehensive systematic reviews were excluded. Primary studies retrieved by the search were excluded if they were captured in 1 or more included systematic reviews or reported the impacts of the intervention only on immune cells. Guidelines with unclear methodology were also excluded.
The included publications were critically appraised by 1 reviewer using the following tools as a guide: A Measurement Tool to Assess systematic Reviews 2 (AMSTAR 2)14 for systematic reviews, the Downs and Black checklist15 for randomized and non-randomized studies, and the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument16 for guidelines. Summary scores were not calculated for the included studies; rather, the strengths and limitations of each included publication were described narratively.
A total of 54 citations were identified in the literature search. Following the screening of titles and abstracts, 24 citations were excluded, and 30 potentially relevant reports from the electronic search were retrieved for full-text review. Ten potentially relevant publications were retrieved from the grey literature search for a full-text review. Of these potentially relevant articles, 33 publications were excluded for various reasons, and 7 publications met the inclusion criteria and were included in this report. These comprised 4 systematic reviews, 2 non-randomized studies, and 1 evidence-based guideline. Appendix 1 presents the PRISMA17 flow chart of the study selection. Additional references of potential interest are provided in Appendix 6.
Four systematic reviews,18-21 2 non-randomized studies,22,23 and 1 evidence-based guideline24 were included. Three systematic reviews19-21 had broader inclusion criteria on interventions; only the subset of studies reporting on TCZ and its comparison were relevant to the current report. We only described the characteristics and results of this subset in this report. Appendix 5 includes a table describing the overlap in relevant primary studies in the included systematic reviews. Given this overlap, the summary of the systematic reviews in this report may repeat some primary study findings. Additional details regarding the characteristics of included publications are provided in Appendix 2.
Three18-20 of 4 systematic reviews included meta-analyses and 1 systematic review21 summarized the findings from primary studies narratively but did not conduct a meta-analysis. The number of primary studies involving TCZ that were included in the systematic reviews ranged from 7 to 27 primary studies, which comprised retrospective observational studies, case reports, and 1 randomized controlled trial (RCT). One review18 provided an indirect comparison of TCZ (7 primary studies) and AZA (19 primary studies) for 1 outcome using pooled effect size based on the test of interaction.25 Three systematic reviews18,20,21 included the same RCT (TANGO trial), which compared TCZ and AZA.26 Two systematic reviews20,21 were published in 2021, 1 systematic review19 was published in 2022 and the fourth systematic review18 was published in 2023 with the search up to July 21, 2022.
Two observational studies with a retrospective before-after design were published in 202323 and 2021.22 One study23 retrospectively collected data for NMOSD patients treated with TCZ and compared the changes between baseline and after treatment. This study also employed adjusted logistic regression models to identify risk factors for relapse. The second study22 included NMOSD patients treated with TCZ, AZA, and rituximab and healthy controls. This study compared the differences between baseline and after treatment within each treatment group or across the 3 drug groups as well as the difference between NMOSD patients and the healthy controls on optical coherence tomography (OCT) measures.
One evidence-based clinical practice guideline was included from Latin America.24 The guideline development group comprised experts in neurology who were involved in the diagnosis and care of NMOSD patients and conducted a systematic literature search (from 1990 to 2019) to identify relevant evidence. The ratings of the quality of evidence and strength of recommendations were not reported. The RAND-UCLA methodology for reaching formal consensus was used, and the recommendations were formulated based on formal consensus and voting processes.24 The grade (i.e., appropriate, inappropriate, or uncertain) and proportion of expert agreement for recommendation statements were provided as outputs of the voting processes.
Of the 4 systematic reviews,18-21 2 systematic reviews were from Nepal,20,21 the third systematic review was from China,18 and the fourth systematic review21 was from the US. One systematic review20 presented the countries or regions of included primary studies. Of the 7 relevant studies, the RCT was conducted in 6 centres in China and the 6 observational studies were conducted in Germany, Spain, France, Japan, and the US.20
The 2 observational studies22,23 were single-centre studies that were conducted in the same hospital in China; and a group from Latin American developed the clinical practice guideline.24
All 4 systematic reviews18-21 involved patients with NMOSD, and the number of included patients ranged from 59 to 1,078. The age of patients ranged from 12 years to 68 years with mean age ranging from 29 years to 50 years in primary studies included in 1 systematic review;20 mean ages were 42 years (TCZ studies) and 37 years (AZA studies) in the second systematic review;18 the mean age ranged from 29 to 50 in the primary studies included in the third systematic review;19 and age was not reported in the fourth systematic review.21 The study populations were predominantly female in 3 systematic reviews18-20, with the proportion of females ranging from 86% to 92%. The fourth systematic review21 did not report the proportion of females. The proportion of patients with AQP4-positive serotype ranged from 14% to 100% across primary studies in 1 systematic review,19 40% to 100% in the second review,20 and was reported as 85.8% in patients with TCZ treatment in the third systematic review and 81.3% for the fourth systematic review.18 One review20 noted that AZA and mycophenolate mofetil were the most common add-on drugs for TCZ, while the remaining systematic reviews18,19,21 did not report the add-on drugs.
The 2 non-randomized studies22,23 included adults with NMOSD. The first study included 65 adult patients with a median age of 44.23 The second study22 included 50 adults with NMOSD and 10 healthy controls with an age range of 18 years to 75 years (mean age from 41 years to 53 years for patients with NMOSD and 44 for healthy controls). The proportion of females was 90% or over for both studies.22,23 The proportion of patients with AQP4-IgG seropositive was 83% in 1 study,23 while all patients were AQP4-IgG seropositive in the second study.22
The included clinical practice guideline was for the management of patients with NMOSD.24 The intended users of the guideline were clinicians involved in the care of patients with NMOSD. There was no pediatrician in the guideline development panel; therefore, pediatric patients with NMOSD may not have been considered in this guideline.
Two systematic reviews18,21 compared the effectiveness and safety of TCZ and AZA, and the remaining 2 systematic reviews19,20 compared the before-and-after changes for TCZ without a comparator group. Two systematic reviews18,19 did not report the dosage and route of administration of TCZ. The other 2 systematic reviews20,21 reported TCZ can be administrated with IV with a dosage of 6 mg/kg to 8 mg/kg every 4 or 6 weeks, or subcutaneously with a dose of 162 mg every 1 to 2 weeks, and AZA can be administered orally with a dosage of 2 to 3 mg/kg per day.
One eligible retrospective observational study23 included patients who were regularly administered IV TCZ (8 mg/kg) every 4, 6 or 8 weeks and compared outcomes before-and-after treatment. The second retrospective observational study22 compared the before-after change scores of OCT measures across 3 drug interventions: IV TCZ (8 mg/kg/month), oral AZA (2 mg/kg/day to 3 mg/kg/day) and IV rituximab (dosage depending on the proportion of CD19+ B-cells in peripheral blood mononuclear cells) and healthy controls.
The included guideline24 considered most treatments for NMOSD that includes TCZ, AZA, eculizumab, inebilizumab, satralizumab, cyclophosphamide, mitoxantrone, IV methylprednisolone, plasmapheresis, mycophenolate mofetil, and rituximab.
All 4 systematic reviews18-21 reported relapse-related outcomes and disability status. Two systematic reviews20,21 reported adverse events and death. One systematic review21 also reported MRI-related disease activity, AQP-4 antibody titres, pain and fatigue (each measured by a numerical rating scale with an unreported range). The specific outcomes for relapse included: annualized relapse rate (ARR), relapse-free rate, hazard risk for relapse and time to first relapse. Disability status was assessed by the Expanded Disability Status Scale (EDSS)27 and ambulatory status. EDSS is a formal scale with possible scores ranging from 0 to10 with higher scores indicating greater disability, while ambulatory status was not a formal scale with the following options: unrestricted, restricted, wheelchair, cane, or walker.28 The mean or median follow-up duration ranged from 16 months to 78.9 months in 1 systematic review,18 12 months to 31 months in the second systematic review,19 12 months to 31.8 months in the third systematic review,20 and 3 months to 80 months in the fourth systematic review.21
One retrospective observational before-and-after study23 reported relapse-related outcomes (including ARR, relapse-free rate, time to the first relapse and risk factors for relapse), disability status, and adverse events with a median follow-up of 34 months. The other retrospective observational study22 reported the changes in visual acuity measures and imaging features (OCT) with a median follow-up ranging from 13 months to 14.6 months.
The included guideline24 considered the relapse risk, disability, and safety outcomes. For some recommendation statements, the costs were considered.
In all 4 systematic reviews,18-21 the objective was clearly described, multiple databases were searched, keywords of the search and study selection flow charts were provided, the review authors declared no conflicts of interest, lists of included articles were presented and the study characteristics were described. None of the systematic reviews18-21 provided lists of excluded articles or assessed the funding sources in individual studies. Two systematic reviews18,21 did not report performing a grey literature search. These limitations may result in the inappropriate exclusion of some studies, missing some unpublished studies or misidentification of potential publication bias. In 1 systematic review,20 article selection and data extraction were done independently by 2 reviewers. In 2 systematic reviews,18,21 it was unclear how article selection and data extraction were conducted. In the fourth systematic review,19 the article selection was done independently by 2 reviewers, but it was unclear how the data extraction was performed, The possibility of missing some relevant articles or errors in data extraction cannot be ruled out. Although 3 systematic reviews18-20 assessed the risk of bias of included individual studies (and reported study quality to be “satisfactory” or “Newcastle-Ottawa Scale score ranged from 5 to 7” for observational studies [1 systematic review20 presented the overall rating for 6 individual studies: 5 high risk of bias and 1 low risk of bias]; with “some concerns” in risk of bias for the included RCT), they did not assess the potential impact of study risk of bias on the interpretation of results. One systematic review21 did not assess the risk of bias of included individual studies, so the quality of these studies is unknown. The results may be driven by individual studies with high risk of bias.
One systematic review18 compared the effectiveness of TCZ and AZA, but only included the TCZ arm of the TANGO trial and left the direct comparison between the 2 drugs out of the pooled analysis. Instead, the systematic review authors pooled data from single-arm trials of TCZ and AZA, and then used the Douglas G test of interaction25 to compare the difference in ARR between the 2 drug groups. This method did not adjust potential confounding factors and cannot take the advantage of randomization in the primary RCT, which only can provide indirect evidence and is likely an inappropriate analysis method for indirect comparisons. This systematic review18 also misinterpreted the P values for effect size and used a fixed-effect model for meta-analysis with moderate heterogeneity, which will result in a narrow confidence interval and in favour of interventions that compared a random-effect model. One systematic review21 summarized findings from individual studies narratively, and some outcome measures (fatigue and ambulatory status) were not validated.
Among the 3 systematic reviews18,20,21 that included the TANGO trial (which provided the only direct comparison between TCZ and AZA among all included primary studies), 2 systematic reviews18,20 assessed the risk of bias for the TANGO trial. One systematic review20 reported the TANGO trial had a high risk of bias in the deviation from the intended intervention domain and an unclear risk of bias in the missing outcome data domain based on Cochrane’s risk of bias tool. This RCT was assessed as having “some concerns” by systematic review authors. The other systematic review18 reported that 2 stars for “selection,” 1 star for “comparability,” an 3 stars for “outcome” based on the Newcastle-Ottawa Scale (no further information was available about how the risk of bias assessments were conducted and the meaning of the risk of bias).
The 2 retrospective observational studies22,23 clearly reported study objectives, inclusion and exclusion criteria, intervention details, participant characteristics, outcome measures, and the main findings. The 2 studies used appropriate statistical analysis methods for comparing changes before-and-after the intervention. Both studies22,23 were funded by academic institutions in China, which may have little influence on potential publication bias. Neither study22,23 conducted sample size calculations, which may result in underpowering for detecting the changes in visual acuity or pain measures. One study23 used a before-after design without a control group. Due to the nature of the design, it is difficult to attribute the before-and-after changes to the effect of TCZ. In this study,23 the authors did not describe the secondary outcome measures well (disability and pain) and the covariates in the logistic regression models. In the other study,22 the authors did not provide detailed information on changes in visual acuity measures, the number of eyes in each drug group, and the covariates in the generalized estimating equations.
The critical appraisal of the included clinical practice guideline24 was performed in a previous CADTH report on rituximab for NMOSD.29 More details about the quality of the guideline can be found in the reports. Briefly, the guideline had clear descriptions of scope, population, target users, guideline developers, and was externally peer-reviewed. The guideline had a transparent literature search and recommendation development methods based on consensus and voting, but the evidence assessment and strength of the recommendations were unclear. Although several authors declared the conflicts of interest, how these were addressed is unclear.
Additional details regarding the strengths and limitations of included publications are provided in Appendix 3.
Three included systematic reviews18,20,21 included the TANGO trial, which was an RCT that compared TCZ and AZA.26 Two reviews18,20 only included data from the TCZ arm of the trial, and the third systematic review21 included data from the 2 arms; however, they included the interim analysis for the TANGO trial as the final results of this trial were not available at that time. The directions of all reported outcomes in the interim analysis were the same as the final trial result report. In this report, we summarized the main findings of the trial based on the final report26 rather than the interim analysis. Appendix 4 presents the main study findings.
Due to some overlap in the studies included in the systematic reviews (Appendix 5), the pooled estimates from these systematic reviews may contain some of the same data. For the systematic reviews without a meta-analysis that narratively summarized the findings on the same outcome,20,21 to avoid duplication of results, outcome data from an individual primary study are only reported once.
Four systematic reviews18-21 reported on ARR, mostly based on findings from single-arm trials. Three systematic reviews18-20 showed that pooled estimates of ARR were statistically significantly reduced after TCZ treatment compared with before TCZ treatment. One systematic review21 reported mean or median changes in ARR for the individual included studies and showed that ARR values were numerically lower after TCZ treatment than before TCZ treatment. The included before-after study23 also showed that the ARR values were statistically significantly reduced after TCZ treatment compared with before TCZ treatment. One systematic review18 reported that ARR was statistically significantly lower with TCZ than AZA, based on indirect comparisons of pooled TCZ and AZA findings from separate, single-arm studies. Moderate to substantial statistical heterogeneities were found in this systematic review18 for TCZ and AZA arms.
One systematic review21 (presenting findings from the TANGO trial26) and 1 before-after study23 reported relapse-free rates. The proportion of patients who were relapse-free was 76.9% from 1 observational study with a median follow-up of 34.1 months after TCZ treatment.23 The systematic review21 narratively summarized the findings of 2 individual included case series and reported 70.3% of patients were relapse-free after TCZ treatment with an unclear follow-up period. The proportion of patients who were relapse-free at the end of the study (up to 92 weeks of follow-up) was statistically significantly higher in the TCZ arm (89%) compared with the AZA arm (56%) in the TANGO trial.26 The before-after study23 showed that the median time to first relapse was 62 weeks for patients treated with TCZ, and identified an infusion interval of more than 4 weeks and pGFAP greater than 220 pg/mL as statistically significant risk factors for relapse with very wide confidence intervals (i.e., low precision). There was a trend for TCZ monotherapy to increase the risk of relapse, but this did not reach statistical significance.
Three systematic reviews18-20 reported that pooled estimates of EDSS were statistically significantly reduced after TCZ treatment compared with before TCZ treatment. Moderate statistical heterogeneities were found in 2 systematic reviews.18,19 One systematic review21 narratively summarized EDSS findings from 10 observational studies (case reports included) and reported 6 individual studies with “significant” EDSS improvement, 2 studies with “mild” improvement, and 2 studies with “unchanged” in EDSS after TCZ treatment. Levels of EDSS improvement were not otherwise defined by systematic review authors. This systematic review also narratively summarized the difference in EDSS between patients treated with TCZ and AZA from the TANGO trial. Presenting findings from the TANGO trial publication,26 there was a statistically significantly lower disability progression rate measured by EDSS in the TCZ group than in the AZA group after 12 weeks of treatment (5 of59 versus 15 of 59, HR: 0.288; 95% CI, 0.105 to 0.759; P = 0.0087). The study authors concluded the same at 24 weeks of treatment; however, the statistical test results for comparing the 2 groups on disability progression were inconsistent within the trial publication at this time point (2 of 59 versus 5 of 59, HR: 0.221; 95% CI, 0.047 to 1.042; P = 0.0309 in the main text; P = 0.0004 in Table 2). The TANGO trial considered the minimally important difference for EDSS as validated for patients with multiple sclerosis (i.e., “disability progression” was defined as an increase in EDSS of at least 1.0 if baseline score was 5.5 or less; at least of 0.5 if baseline score was great than 5.5). The included before-after study23 also showed that the median EDSS scores were statistically significantly reduced after TCZ treatment compared with before treatment both for AQP4-antibody positive and negative patients.
One systematic review21 identified a case series (with 12 patients) that reported on ambulatory status and found that most patients (n = 9) had stable ambulatory status after TCZ treatment.
Two systematic reviews20,21 and 1 before-and-after study23 reported adverse events in patients with NMOSD who received TCZ treatment. One systematic review20 showed that the pooled estimate of the proportion of patients with any adverse events was 56%, and the proportion of patients with serious adverse events was 11%. One systematic review21 that included findings from the TANGO trial reported that the proportions of patients with at least 1 adverse event were 97% (61% treatment-related adverse events as determined by the trial authors) in the TCZ arm and 95% (83% treatment-related adverse events as determined by the trial authors) in the AZA arm and the proportions of patients with at least 1 serious adverse event was 8% and 15%, respectively (without statistical test). The serious adverse events included pneumonia, herpes zoster infection, deep vein thrombosis, basal ganglia hemorrhage, and myelitis.
One systematic review21 identified 3 deaths. One occurred in 1 of the included observational studies, and 2 occurred in the TANGO trial (1 for each arm). The trial and the systematic review authors noted these deaths are unlikely related to the treatment.
One systematic review21 and 1 before-after study reported on pain outcomes measured by the numerical rating scale. The systematic review showed that pain scores were numerically lower after 12 months of TCZ treatment compared with before TCZ treatment (without statistical test). However, the before-after study23 reported the pain score remained unchanged after TCZ treatment (median follow-up of 34.1 months) compared with before TCZ treatment (without statistical test). Based on findings from individual included studies, 1 systematic review21 reported that the general fatigue scores (no details on the measures) were numerically lower after TCZ treatment compared with before TCZ treatment (without statistical test).
One observational study22 reported eye- and vision-related outcomes in patients with NMOSD who were treated with TCZ, rituximab, or AZA and compared the changes in eye measures between patients and heathy controls. This study concluded that there were no changes in LogMAR visual acuity or low-contrast letter acuity either in NMOSDON+ eyes (eyes with a history of acute optic neuritis attack) or NMOSDON- eyes (eyes without a history of acute optic neuritis attack) after TCZ, AZA and rituximab treatment compared with baseline. No data were reported to support conclusions on visual acuity. The study also reported OCT measures of eyes and noted that patients treated with TCZ and rituximab did not display macular ganglion cell complex or peripapillary retinal nerve fibre layer thinning in NMOSDON- eyes, while patients treated with AZA showed statistically significant macular ganglion cell complex or peripapillary retinal nerve fibre layer thinning in NMOSDON- eyes. NMOSD patients treated with AZA showed statistically significant greater thinning in macular ganglion cell complex or peripapillary retinal nerve fibre layer measures compared with patients treated with TCZ and rituximab in NMOSDON- eyes. These measures may serve as indicators of retinal ganglion cell loss.
One systematic review21 also reported MRI-related disease activity measures and AQP4-and myelin oligodendrocyte glycoprotein antibody titres in patients with NMOSD after TCZ treatment but noted that the 2-antibody status was not correlated with a higher risk of relapse.
No cost-effectiveness evidence regarding TCZ for patients with NMOSD was identified; therefore, no summary can be provided.
The clinical practice guidelines24 from Latin America presents statements on various treatments for patients with NMOSD, described in detail in a previous CADTH report.29 For long-term relapse prevention, the guideline recommends the early start of immunosuppressant treatments to reduce disease activity and prevent NMOSD attacks. Immunosuppressant treatments addressed by this guideline include AZA, MMF, rituximab, TCZ, eculizumab, satralizumab, inebilizumab, and oral steroids.
TCZ is suggested as 1 of the second-line treatment options for patients who have no response to other immunosuppressants to prevent long-term relapse prevention (Appropriate, 90% agreement). Eculizumab, inebilizumab, and satralizumab also can be used under these conditions; the guideline did not favour a particular humanized monoclonal antibody for second-line therapy. When starting immunosuppressant treatment (AZA, MMF, or rituximab), oral steroid tapering or maintained therapy were suggested in this guideline; however, this guideline did not mention whether adding TCZ should be combined with the oral steroid therapy. This guideline did not report the strength of the recommendations or the quality of evidence informing the recommendations, though the authors cited the TANGO trial26 and 1 observational study to support the statement regarding TCZ. The 2 studies were captured by systematic reviews included in this report.
Although we identified 4 systematic reviews18-21 and 2 retrospective observational studies22,23 to answer the research question on the clinical effectiveness of TCZ, most included primary studies in these systematic reviews were uncontrolled before-after studies or case reports, except for 1 RCT. This RCT (with “some concerns” according to systematic review authors20) overlapped among 3 systematic reviews, and an overlap matrix of relevant primary studies (Appendix 5) reveals that more recent systematic reviews do not substantially build on the evidence base. Due to the nature of the observational studies, potential selection bias, recall bias or performance bias in the body of evidence cannot be ruled out. Potentially inappropriate indirect comparisons of pooled estimates may amplify the bias. The quantity and quality of evidence regarding pain and fatigue were limited. The death events (n = 3) were low among included studies, and the comparison of TCZ and other immunosuppressants on mortality was not determined.
TCZ and other antibodies are usually expensive compared with traditional oral drugs (e.g., AZA), and patients underwent prolonged infusion intervals mainly due to economic burden.23 Cost-effectiveness will be essential for future decision-making. However, we did not find any cost-effectiveness studies of TCZ among patients with NMOSD.
Most eligible patients for the included studies were adults and most (over 80%) of them are female, which reflects the prevalence of NMOSD worldwide.2 However, the data did not allow us to comment on the subgroup effects of the pediatric population and the male population. When applying the evidence to these minor populations, one might need to consider the applicability of the evidence to the target population. The management of patients with NMOSD involved many drugs and the usual care may differ across different studies. Observational studies, especially for uncontrolled before-after studies, may not account for these differences, and it is unclear to what extent the difference in outcome measures between studies can be attributed to different usual care therapies. The variabilities in add-on drugs, treatment intervals, or comorbidities in the primary studies were probably some reasons for the observed heterogeneity in the pooled estimates. The current report did not identify comparisons of TCZ versus other immunosuppressant treatments such as satralizumab, MMF, methotrexate, cyclophosphamide, cyclosporine, prednisone, eculizumab, inebilizumab, and rituximab. Furthermore, the identified guideline24 did not address the place in therapy for TCZ relative to other second-line treatment options. Together, it remains unclear which patients may benefit from TCZ compared to alternative immunosuppressant therapies, particularly other humanized monoclonal antibodies.
The primary studies of the included systematic reviews18-21 were conducted in Asia, Europe, and the US. The clinical practice guideline24 was from Latin America and considered the local cost in Latin America. Thus, the generalizability of these findings to settings in Canada is uncertain.
Four systematic reviews18-21 and 2 observational studies22,23 were identified to address the clinical effectiveness of TCZ for patients with NMOSD. Evidence from before-and-after studies without a control group suggests that patients treated with TCZ had statistically significantly reduced ARR and EDSS compared with before TCZ treatment. Evidence from 2 systematic reviews18,21 indicated that TCZ may be better than AZA to manage patients with NMOSD in reducing the relapse risk and increasing the relapse-free rate. However, these findings were based on a single RCT26 and an indirect comparison of pooled findings from single-arm trials, which did not account for confounding variables. One before-and-after study23 without a control group, identified infusion interval of more than 4 weeks and pGFAP greater than 220 pg/mL as risk factors for relapse, but the confidence intervals were very wide (i.e., low precision). Using TCZ may slow disability progression compared with AZA; however, some observational studies showed the EDSS scores were unchanged after TCZ treatment. The adverse events were common during the treatment. However, the proportion of adverse events was similar between TCZ and AZA, and the proportions of treatment-related adverse events and serious adverse events were numerically higher in the AZA group than in the TCZ group. The serious adverse events included pneumonia, herpes zoster infection, deep vein thrombosis, basal ganglia hemorrhage, and myelitis. Based on a retrospective study,22 TCZ treatments may have little or no impact on visual acuity function but may have some benefits in OCT measures. The impacts of TCZ on pain and fatigue were inconsistent: some studies in 1 included systematic review21 showed numerically lower scores (pain and fatigue), while another study23 with a longer follow-up did not show any changes in pain measure scores.
One evidence-based clinical practice guideline24 from Latin America suggests that TCZ can be used for patients with NMOSD who have no response to other immunosuppressants to prevent long-term relapse. However, this guideline did not report the strength of the recommendation or the quality of evidence informing the recommendation. The available evidence identified for this report suggests TCZ can be potentially used before AZA when considering the relapse outcomes and disability status, but the quality of evidence was low. Future guidelines may need to consider all related evidence regarding benefits and harms to make transparent and trustworthy recommendations. Considering the limitations of the body of evidence, such as the limitation of observational studies with before-and-after study designs without a control group, and the potentially inappropriate indirect comparison of pooled estimates, these findings should be interpreted with caution. In addition, the generalizability of the evidence to settings in Canada or minor NMOSD populations (e.g., pediatric, male) was unclear.
Cost-effectiveness will be helpful for decision- or policy-making. However, no evidence regarding the cost-effectiveness of TCZ for patients with NMOSD was identified that met the inclusion criteria for this report. TCZ requires IV or subcutaneous administration; patients’ values or preferences regarding injection and oral medicine also may affect the decision-making.30
To compare the clinical effectiveness of TCZ to other pharmacological therapies or no treatment, we should consider both direct and indirect evidence. The evidence synthesis by 1 included systematic review18 omitted the direct comparison from the TANGO trial that directly compared TCZ versus AZA. To help decision-making regarding the use of TCZ for NMOSD, we need to consider it relative to other immunosuppressant treatments, including other humanized monoclonal antibodies recommended for second-line therapy. However, an available systematic review with network meta-analysis31 did not include TCZ. When possible, given the availability of trials that address the relative effects of AZA versus other treatments, a systematic review with network meta-analysis may be helpful to answer the question. Future primary studies with a robust methodology, such as those with prospective designs or RCTs, comparing TCZ with other immunosuppressants, are also required.
aquaporin 4
annualized relapse rate
azathioprine
confidence interval
Expanded Disability Status Scale
hazard ratio
IV methylprednisolone
logarithm of the minimum angle of resolution
mycophenolate mofetil
neuromyelitis optica spectrum disorder
optical coherence tomography
odds ratio
standardized mean difference
tocilizumab
Selection of Included Studies.
Note that these tables have not been copy-edited.
Characteristics of Included Systematic Reviews.
Characteristics of Included Primary Clinical Studies.
Characteristics of Included Guideline.
Note that these tables have not been copy-edited.
Strengths and Limitations of Systematic Reviews Using AMSTAR 214.
Strengths and Limitations of Clinical Studies Using the Downs and Black Checklist.
Strengths and Limitations of Guideline Using AGREE II.
Note that these tables have not been copy-edited.
Summary of Findings by Outcome — Relapse Risk.
Summary of Findings by Outcome — Disability.
Summary of Findings by Outcome — Adverse Events.
Summary of Findings by Outcome — Pain and Fatigue.
Summary of Findings by Outcome — Optical Coherence Tomography Measures.
Summary of Findings by Outcome — Other outcomes.
Summary of Recommendations in Included Guidelines.
Note that this table has not been copy-edited.
Overlap in Relevant Primary Studies Between Included Systematic Reviews.
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