Long-term clinical outcomes in patients with multiple sclerosis who are initiating disease-modifying therapy with natalizumab compared with BRACETD first-line therapies.

Background: Aggressive disease control soon after multiple sclerosis (MS) diagnosis may prevent irreversible neurological damage, and therefore early initiation of a high-efficacy disease-modifying therapy (DMT) is of clinical relevance. Objectives: Evaluate long-term clinical outcomes in patients with MS who initiated treatment with either natalizumab or a BRACETD therapy (interferon beta, glatiramer acetate, teriflunomide, or dimethyl fumarate). Design: This retrospective analysis utilized data from MSBase to create a matched population allowing comparison of first-line natalizumab to first-line BRACETD. Methods: This study included patients who initiated treatment either with natalizumab or a BRACETD DMT within 1 year of MS diagnosis and continued treatment for ⩾6 months, after which patients could switch DMTs or discontinue treatment. Patients had a minimum follow-up time of ⩾60 months from initiation. A subgroup analysis compared the natalizumab group to patients in the BRACETD group who escalated therapy after 6 months. Outcomes included unadjusted annualized relapse rates (ARRs), time-to-first relapse, time-to-first confirmed disability improvement (CDI), and time-to-first confirmed disability worsening (CDW). Results: After 1:1 propensity score matching, 355 BRACETD patients were matched to 355 natalizumab patients. Patients initiating natalizumab were less likely to experience a relapse over the duration of follow-up, with ARRs [95% confidence interval (CI)] of 0.080 (0.070-0.092) for natalizumab patients and 0.191 (0.178-0.205) for BRACETD patients (p < 0.0001). A Cox regression model of time-to-first relapse showed a reduced risk of relapse for natalizumab patients [hazard ratio (95% CI) of 0.52 (0.42-0.65); p < 0.001] and a more favorable time-to-first CDI. The risk of CDW was similar between groups. The subgroup analysis showed an increased relapse risk as well as a significantly higher risk of CDW for BRACETD patients. Conclusion: Early initiation of natalizumab produced long-term benefits in relapse outcomes in comparison with BRACETD, regardless of a subsequent escalation in therapy.

Progressive multifocal leukoencephalopathy with natalizumab extended or standard interval dosing in the United States and the rest of the world.

BACKGROUND: Progressive multifocal leukoencephalopathy (PML), an important identified risk for natalizumab, has been described for standard interval dosing (SID; dosing interval every-4-weeks). Information on PML with natalizumab extended interval dosing (EID; dosing interval >every-4-weeks) in the US and the rest of the world (ROW) is limited. RESEARCH DESIGN AND METHODS: A retrospective analysis of patient demographics, risk factors, clinical characteristics, and clinical outcomes was conducted on confirmed natalizumab EID and SID PML cases evaluated from Biogen pharmacovigilance systems. RESULTS: Of 857 confirmed natalizumab PML cases, EID and SID accounted for 7.5% and 92.5%, respectively (US: 12.9% and 87.1%; ROW: 5.4% and 94.6%). PML risk factors included anti-JCV index > 1.5 (US: EID, 56.7% and SID, 12.8%; ROW: EID, 44.1% and SID, 21.0%), mean duration of natalizumab treatment (US: 90.0 and 70.2 months; ROW: 54.1 and 49.8 months), and prior immunosuppressive therapy (US: 20.0% and 21.7%; ROW:11.8% and 18.0%). In the EID and SID groups, 68.8% and 76.0% of patients, respectively, were alive at up to 2 years after diagnosis. CONCLUSIONS: This analysis provides insights on PML in patients receiving natalizumab that extend current knowledge, particularly regarding PML in patients receiving natalizumab EID, which can be built upon in the future.

Serum neurofilament light levels in natalizumab-treated patients with multiple sclerosis who switch to extended interval dosing from every-4-week dosing in real-world clinical practice.

BACKGROUND: Serum levels of neurofilament light chain (sNfL) are a potentially useful biomarker for assessing the efficacy of multiple sclerosis (MS) treatments. OBJECTIVE: To compare levels of sNfL in patients with MS who switched from natalizumab every 4 weeks (Q4W) to extended interval dosing (EID) and patients who remained on Q4W dosing in real-world clinical practice. METHODS: This was a retrospective analysis of samples from patients treated with natalizumab from 2010 to 2015 at a single center in the United States. Levels of sNfL were compared in patients who stayed on Q4W dosing or who switched to EID (parallel-arm analyses) and during Q4W and EID periods in patients who switched to EID (pre- and post-switch analyses). RESULTS: The analysis included 139 patients (Q4W: n = 79; EID: n = 60). After adjustment, levels of sNfL did not significantly differ between patients who remained on Q4W dosing and those who switched to EID in parallel-arm analyses (adjusted Q4W-EID difference = 0.51 pg/mL; p = 0.60) or pre- and post-switch analyses (adjusted difference = 0.96 pg/mL; p = 0.10). CONCLUSION: These sNfL biomarker results suggest that the effectiveness of natalizumab is maintained in patients who switch from Q4W dosing to EID.

Chronic lesion activity and disability progression in secondary progressive multiple sclerosis.

Objective: Slowly expanding lesions (SELs), a subgroup of chronic white matter lesions that gradually expand over time, have been shown to predict disability accumulation in primary progressive multiple sclerosis (MS) disease. However, the relationships between SELs, acute lesion activity (ALA), overall chronic lesion activity (CLA) and disability progression are not well understood. In this study, we examined the ASCEND phase III clinical trial, which compared natalizumab with placebo in secondary progressive MS (SPMS). Methods: Patients with complete imaging datasets between baseline and week 108 (N=600) were analysed for SEL prevalence (the number and volume of SELs), disability progression, ALA (assessed by gadolinium-enhancing lesions and new T2-hyperintense lesions) and CLA (assessed by T1-hypointense lesion volume increase within baseline T2-non-enhancing lesions identified as SELs and non-SELs). Results: CLA in both SELs and non-SELs was greater in patients with SPMS with confirmed disability progression than in those with no progression. In the complete absence of ALA at baseline and on study, SEL prevalence was significantly lower, while CLA within non-SELs remained associated with disability progression. Natalizumab decreased SEL prevalence and CLA in SELs and non-SELs compared with placebo. Conclusions: This study shows that CLA in patients with SPMS is decreased but persists in the absence of ALA and is associated with disability progression, highlighting the need for therapeutics targeting all mechanisms of CLA, including smouldering inflammation and neurodegeneration. Trial registration number: NCT01416181.

Comparison of switching to 6-week dosing of natalizumab versus continuing with 4-week dosing in patients with relapsing-remitting multiple sclerosis (NOVA): a randomised, controlled, open-label, phase 3b trial.

BACKGROUND: Treatment with natalizumab once every 4 weeks is approved for patients with relapsing-remitting multiple sclerosis, but is associated with a risk of progressive multifocal leukoencephalopathy. Switching to extended-interval dosing is associated with lower progressive multifocal leukoencephalopathy risk, but the efficacy of this approach is unclear. We aimed to assess the safety and efficacy of natalizumab once every 6 weeks compared with once every 4 weeks in patients with relapsing-remitting multiple sclerosis. METHODS: We did a randomised, controlled, open-label, phase 3b trial (NOVA) at 89 multiple sclerosis centres across 11 countries in the Americas, Europe, and Western Pacific. Included participants were aged 18-60 years with relapsing-remitting multiple sclerosis and had been treated with intravenous natalizumab 300 mg once every 4 weeks with no relapses for at least 12 months before randomisation, with no missed doses in the previous 3 months. Participants were randomly assigned (1:1), using a randomisation sequence generated by the study funder and contract personnel with interactive response technology, to switch to natalizumab once every 6 weeks or continue with once every 4 weeks. The centralised MRI reader, independent neurology evaluation committee, site examining neurologists, site backup examining neurologists, and site examining technicians were masked to study group assignments. The primary endpoint was the number of new or newly enlarging T2 hyperintense lesions at week 72, assessed in all participants who received at least one dose of assigned treatment and had at least one postbaseline MRI, relapse, or neurological examination or efficacy assessment. Missing primary endpoint data were handled under prespecified primary and secondary estimands: the primary estimand included all data, regardless of whether participants remained on the assigned treatment; the secondary estimand classed all data obtained after treatment discontinuation or study withdrawal as missing. Safety was assessed in all participants who received at least one dose of study treatment. Study enrolment is closed and an open-label extension study is ongoing. This study is registered with EudraCT, 2018-002145-11, and ClinicalTrials.gov, NCT03689972. FINDINGS: Between Dec 26, 2018, and Aug 30, 2019, 605 patients were assessed for eligibility and 499 were enrolled and assigned to receive natalizumab once every 6 weeks (n=251) or once every 4 weeks (n=248). After prespecified adjustments for missing data, mean numbers of new or newly enlarging T2 hyperintense lesions at week 72 were 0·20 (95% CI 0·07-0·63) in the once every 6 weeks group and 0·05 (0·01-0·22) in the once every 4 weeks group (mean lesion ratio 4·24 [95% CI 0·86-20·85]; p=0·076) under the primary estimand, and 0·31 (95% CI 0·12-0·82) and 0·06 (0·01-0·31; mean lesion ratio 4·93 [95% CI 1·05-23·20]; p=0·044) under the secondary estimand. Two participants in the once every 6 weeks group with extreme new or newly enlarging T2 hyperintense lesion numbers (≥25) contributed most of the excess lesions. Adverse events occurred in 194 (78%) of 250 participants in the once every 6 weeks group and 190 (77%) of 247 in the once every 4 weeks group, and serious adverse events occurred in 17 (7%) and 17 (7%), respectively. No deaths were reported. There was one case of asymptomatic progressive multifocal leukoencephalopathy (without clinical signs) in the once every 6 weeks group, and no cases in the once every 4 weeks group; 6 months after diagnosis, the participant was without increased disability and remained classified as asymptomatic. INTERPRETATION: We found a numerical difference in the mean number of new or newly enlarging T2 hyperintense lesions at week 72 between the once every 6 weeks and once every 4 weeks groups, which reached significance under the secondary estimand, but interpretation of statistical differences (or absence thereof) is limited because disease activity in the once every 4 weeks group was lower than expected. The safety profiles of natalizumab once every 6 weeks and once every 4 weeks were similar. Although this trial was not powered to assess differences in risk of progressive multifocal leukoencephalopathy, the occurrence of the (asymptomatic) case underscores the importance of monitoring and risk factor consideration in all patients receiving natalizumab. FUNDING: Biogen.

No difference in radiologic outcomes for natalizumab patients treated with extended interval dosing compared with standard interval dosing: Real-world evidence from MS PATHS.

BACKGROUND: Extended interval dosing (EID; average dosing interval approximately every 6 weeks) of natalizumab is associated with significantly lower risk of progressive multifocal leukoencephalopathy than standard interval dosing (SID; every 4 weeks) in patients with relapsing-remitting multiple sclerosis (MS). Real-world studies, though limited, suggest that natalizumab effectiveness is generally maintained in patients who switch to EID after initiation of stable treatment with SID. MS PATHS (Multiple Sclerosis Partners Advancing Technology and Health Solutions) is a collaborative, multicenter learning health system that generates real-world clinical and MRI data using highly standardized acquisition protocols. We compared MRI outcomes in MS PATHS patients treated with natalizumab EID versus SID. We also compared MRI outcomes in patients treated with natalizumab (EID and/or SID) versus injectable MS platform therapy. METHODS: Natalizumab infusion data from the TOUCH Prescribing Program database and MS PATHS MRI assessment data from seven US sites as of July 23, 2020, were used to identify patients with relapsing-remitting MS who had received natalizumab EID or SID in the interval between two MRI scans (an MRI segment). Patients who received injectable platform MS therapy between two MRI scans were also identified. MRI data were used to determine the incidence rate and odds of developing new or enlarging T2 lesions, annualized percentage change in T2 lesion volume (T2LV), and annualized percentage change in brain parenchymal fraction (BPF). MRI outcomes were compared for 1) natalizumab EID treatment versus natalizumab SID treatment, 2) natalizumab treatment (EID + SID) versus platform therapy, and 3) natalizumab EID versus platform therapy. Propensity score-based weighting or matching were used to balance covariates at the start of MRI segments for all comparisons. RESULTS: The MRI outcomes observed with natalizumab EID treatment did not differ significantly from those observed with natalizumab SID treatment. The odds ratio for any new or enlarging T2 lesion was 1.07 (95% confidence interval [CI]: 0.93, 1.24; p = 0.355), and the rate ratio (95% CI) for new or enlarging T2 lesions was 1.62 (0.93, 2.82; p = 0.090). Differences (95% CI) between EID and SID patients in mean annualized percentage change in T2LV and BPF were 1.56% (-3.77%, 6.90%; p = 0.566) and -0.11% (-0.25%, -0.10%; p = 0.096), respectively. Conversely, when MRI outcomes in natalizumab and platform therapy patients were compared, there were significant differences favoring natalizumab in all assessments: the odds of any new or enlarging T2 lesion (odds ratio: 0.69 [95% CI: 0.64, 0.75]; p<0.001), the incidence rate of new or enlarging T2 lesions (rate ratio: 0.47 [95% CI: 0.37, 0.61]; p<0.001), annualized percentage change (decrease) in T2LV (difference: -3.68% [95% CI: -7.06%, -0.30%]; p = 0.033), and annualized percentage change (increase) in BPF (difference: 0.22% [95% CI: 0.16%, 0.29%]; p<0.001). Results of the subgroup comparison of natalizumab EID patients with platform therapy patients were similar to those of the overall-natalizumab-group-versus-platform-therapy comparison. CONCLUSIONS: The results indicate that natalizumab EID and SID provide comparable real-world effectiveness on quantitative MRI metrics. These data further demonstrate that natalizumab EID can provide superior real-world effectiveness to injectable platform therapy on quantitative MRI metrics.

No evidence for loss of natalizumab effectiveness with every-6-week dosing: a propensity score-matched comparison with every-4-week dosing in patients enrolled in the Tysabri Observational Program (TOP).

BACKGROUND: Extended interval dosing of natalizumab is associated with significantly lower progressive multifocal leukoencephalopathy risk compared with every-4-week (Q4W) dosing in patients with relapsing-remitting multiple sclerosis. Previous studies have suggested that natalizumab effectiveness is maintained in patients who switch from Q4W to extended interval dosing but have been limited by a lack of well-matched patient cohorts. METHODS: Tysabri Observational Program (TOP) data as of November 2019 were used to identify patients with relapsing-remitting multiple sclerosis treated with natalizumab Q4W and those with a single physician-indicated dosing change from Q4W to every-6-week (Q6W) dosing after ⩾1 year of Q4W treatment. Patients were propensity score matched at the time of the switch from Q4W to Q6W dosing. Clinical outcomes (annualized relapse rate and probability of remaining relapse free or free of 24-week confirmed disability worsening) and safety outcomes were assessed for the two cohorts. RESULTS: This study included 219 pairs of propensity score-matched Q6W and Q4W patients. Annualized relapse rates were similar for Q6W (0.150) and Q4W (0.157) patients. The probability of remaining relapse free [hazard ratio = 1.243 (95% confidence interval = 0.819-1.888); p = 0.307] and of remaining free of 24-week confirmed disability worsening [hazard ratio = 0.786 (95% confidence interval = 0.284-2.176); p = 0.644] did not differ significantly between Q6W and Q4W patients. Summarized safety results for the matched Q6W and Q4W patients are also presented. CONCLUSION: These real-world findings in well-matched patient cohorts from TOP demonstrate that natalizumab effectiveness is maintained in patients who switch to Q6W dosing after ⩾1 year of Q4W dosing. CLINICALTRIALSGOV IDENTIFIER: NCT00493298.

Clinical outcomes in patients who discontinue natalizumab therapy after 2 years in the Tysabri® Observational Program (TOP).

BACKGROUND: Natalizumab is a highly efficacious therapy for relapsing-remitting multiple sclerosis (RRMS). Patients who discontinue natalizumab may experience return of MS disease activity. OBJECTIVE: The aim of this study was to analyze predictors of post-natalizumab disease activity return. METHODS: The Tysabri® Observational Program (TOP) is an ongoing observational study of natalizumab-treated RRMS patients. Patients discontinuing natalizumab are encouraged to remain in TOP. RESULTS: Analyses included 3221 TOP patients. After ⩾2 years on natalizumab, relapse risk was twice as high for patients who switched to an oral therapy (n = 660, hazard ratio (HR) = 2.18, p < 0.001) and three times as high for patients who switched to an injectable therapy (n = 95, HR = 3.02, p < 0.001) as for those who stayed on natalizumab (n = 2466). Relapse rates after switching remained below pre-natalizumab rates. In patients who switched to an oral therapy, higher relapse risk was predicted by longer washout time, more pre-natalizumab relapses, higher Expanded Disability Status Scale score at natalizumab initiation, and shorter natalizumab treatment duration. CONCLUSION: Patients who stayed on natalizumab had better clinical outcomes than those who switched to an oral or injectable therapy after ⩾2 years on natalizumab. These results highlight modifiable risk factors for disease activity return (e.g. natalizumab treatment duration and washout duration) to consider when making treatment decisions.

Modeling the Efficacy of Natalizumab in Multiple Sclerosis Patients Who Switch From Every-4-Week Dosing to Extended-Interval Dosing.

Natalizumab is approved for multiple sclerosis treatment at a dose of 300 mg every 4 weeks. Extended-interval dosing of natalizumab has been proposed as a strategy to mitigate the risk of progressive multifocal leukoencephalopathy, but the efficacy of extended-interval dosing is not established. Previous models suggesting lower efficacy when initiating natalizumab treatment with extended-interval dosing rather than every-4-week dosing are inconsistent with reports from clinical observations and real-world studies conducted in patient populations switching to extended-interval dosing after a period of receiving natalizumab every 4 weeks. Here, the efficacy of natalizumab extended-interval dosing was modeled specifically in patients switching from every-4-week dosing to extended-interval dosing. Published population pharmacokinetic/pharmacodynamic models were used to simulate the distribution of alpha-4 integrin saturations for different body weight categories and dosing intervals (every 5, 6, 7, 8, 10, or 12 weeks). Generalized estimating equations relating alpha-4 integrin saturation to probability of multiple sclerosis lesion or relapse were derived from RESTORE trial data, which included patients (n = 175) who discontinued natalizumab after being treated every 4 weeks for ≥1 year and had no relapses in the year before discontinuation. The model-based simulations described indicate that every-5-week or every-6-week dosing is likely to maintain the efficacy of natalizumab, particularly at body weights <80 kg, in patients who switch after a period of stability on every-4-week dosing. The efficacy of natalizumab decreases as dosing intervals and body weight increase. Partial model validation was achieved in that observed outcomes in an independent clinical study were similar to those predicted by the models.

Real-world disability improvement in patients with relapsing-remitting multiple sclerosis treated with natalizumab in the Tysabri Observational Program.

BACKGROUND: Natalizumab has been associated with disability improvement as indicated by a confirmed Expanded Disability Status Scale (EDSS) score decrease. OBJECTIVE: The aim of this study was to characterize disability improvement in patients in the Tysabri Observational Program (TOP), an ongoing observational study of relapsing-remitting multiple sclerosis patients initiating natalizumab in clinical practice. METHODS: TOP data as of November 2018 were included. Confirmed disability improvement (CDI) was defined as a decrease ⩾1.0 confirmed 24 weeks later from a baseline EDSS score ⩾2.0. Confirmed functional system (FS) improvement was defined as a decrease ⩾1.0 confirmed 24 weeks later from a baseline score ⩾1.0 in that FS. RESULTS: Of 5384 patients, 1287 (23.9%) had CDI; 51.8% experienced CDI in the first treatment year. Among patients with CDI, 56.6% had CDI ⩾1.5 points; 34.4% had CDI ⩾2.0 points. The cumulative probability of maintaining improvement 8 years after the CDI event was 52.6%. At treatment initiation, 5363 patients (85.2%) had impairment in ⩾1 FS. At 8 years, the cumulative probability of confirmed improvement in any FS was 88.8% and ranged from 38.3% to 58.6% in individual FS. CONCLUSION: These results highlight disability improvement as a potential benefit of natalizumab treatment. Improvements across all FS demonstrate the range of functional improvement.

Natalizumab versus fingolimod for patients with active relapsing-remitting multiple sclerosis: results from REVEAL, a prospective, randomised head-to-head study.

OBJECTIVE: To directly compare the efficacy of natalizumab and fingolimod in patients with active relapsing-remitting multiple sclerosis. METHODS: This phase 4, randomised, rater- and sponsor-blinded, prospective, parallel-group, clinic-based head-to-head study was conducted at 43 sites in nine countries. Patients were randomised (1:1) to intravenous natalizumab 300 mg every 4 weeks or oral fingolimod 0.5 mg once daily for ≤52 weeks. Enrolment-related early study termination precluded assessment of the primary endpoint (evolution of new on-treatment gadolinium-enhancing (Gd+) lesions to persistent black holes). Unplanned exploratory analyses of secondary endpoints evaluated the effects of treatment on the development of new T1 Gd+ lesions and new/newly enlarging T2 lesions, lesion volumes and relapse outcomes. RESULTS: The intent-to-treat population comprised 108 patients (natalizumab, n=54; fingolimod, n=54); 63 completed ≥24 weeks of treatment. Due to the limited numbers of events and patients at risk, MRI and relapse outcomes were reported over up to 24 and 36 weeks, respectively. The mean number of new T1 Gd+ lesions was numerically lower with natalizumab than with fingolimod by 4 weeks; accumulation rates were 0.02 and 0.09 per week, respectively, over 24 weeks (p=0.004). The cumulative probability of developing ≥1 lesion at 24 weeks was 40.7% with natalizumab versus 58.0% with fingolimod (HR=0.60; 95% CI 0.31-1.16; p=0.126); the corresponding probabilities for ≥2 lesions were 11.5% vs 48.5% (HR=0.25; 95% CI 0.09-0.68; p=0.007). No significant between-group differences were observed for the other MRI outcomes at 24 weeks. The cumulative probability of relapse over follow-up was 1.9% with natalizumab versus 22.3% with fingolimod (HR=0.08; 95% CI 0.01-0.64; p=0.017). Adverse events were consistent with known safety profiles. CONCLUSIONS: These results suggest that natalizumab is more efficacious than fingolimod in reducing multiple sclerosis relapses and T1 Gd+ lesion accumulation in patients with active disease. TRIAL REGISTRATION NUMBERS: NCT02342704; EUCTR2013-004622-29-IT; Post-results.

Long-term safety and effectiveness of natalizumab treatment in clinical practice: 10 years of real-world data from the Tysabri Observational Program (TOP).

OBJECTIVE: The Tysabri Observational Programme (TOP), which began >10 years ago, is an open-label, multinational, prospective observational study evaluating the long-term safety and effectiveness of natalizumab in relapsing-remitting multiple sclerosis patients. METHODS: These data provide a 10-year interim analysis of safety and effectiveness in TOP. Annualised relapse rates (ARRs) and disability progression/improvement were analysed using the Poisson model and the Kaplan-Meier method, respectively. Analyses included patients on natalizumab and those who discontinued natalizumab but remained in TOP. RESULTS: As of November 2017, TOP included 6148 patients. Overall, 829 patients (13.5%) experienced ≥1 serious adverse event (SAE), with infection the most common (4.1%). Fifty-three patients (0.9%) had confirmed progressive multifocal leukoencephalopathy. SAE data were consistent with natalizumab's known safety profile; no new safety signals were identified. A total of 3210 patients (52.2%) discontinued natalizumab; 2117 (34.4%) withdrew from TOP. Median time on natalizumab was 3.3 (range 0-11.6) years; median follow-up time was 5.2 (range 0-10.8) years. The on-natalizumab ARR was 0.15, a 92.5% reduction from the year before initiation. Ten-year cumulative probabilities of disability worsening and improvement were 27.8% and 33.1%, respectively. On-natalizumab ARRs were similar between patients who discontinued or remained on natalizumab, suggesting limited attrition bias. CONCLUSIONS: Since the TOP 5-year interim analysis (December 2012), cohort size (6148 vs 4821), median exposure (3.3 vs 1.8 years) and median follow-up time (62 vs 26 months) have increased. This 10-year interim analysis further supports the robust real-world effectiveness and well-established safety profile of natalizumab. TRIAL REGISTRATION NUMBER: NCT00493298.

Risk of natalizumab-associated PML in patients with MS is reduced with extended interval dosing.

OBJECTIVE: To use the large dataset from the Tysabri Outreach: Unified Commitment to Health (TOUCH) program to compare progressive multifocal leukoencephalopathy (PML) risk with natalizumab extended interval dosing (EID) vs standard interval dosing (SID) in patients with multiple sclerosis (MS). METHODS: This retrospective cohort study included anti-JC virus antibody-positive patients (n = 35,521) in the TOUCH database as of June 1, 2017. The effect of EID on PML risk was evaluated with 3 planned analyses using Kaplan-Meier methods stratified by prior immunosuppressant use. Risk of PML was analyzed by Cox regression adjusted for age, sex, prior immunosuppressants, time since natalizumab initiation, and cumulative number of infusions. RESULTS: This study included 35,521 patients (primary analysis: 1,988 EID, 13,132 SID; secondary analysis: 3,331 EID, 15,424 SID; tertiary analysis: 815 EID, 23,168 SID). Mean average dosing intervals were 35.0 to 43.0 and 29.8 to 30.5 days for the EID and SID cohorts, respectively. Hazard ratios (95% confidence intervals) of PML risk for EID vs SID were 0.06 (0.01-0.22, p < 0.001) and 0.12 (0.05-0.29, p < 0.001) for the primary and secondary analyses, respectively. Relative risk reductions were 94% and 88% in favor of EID for the primary and secondary analyses, respectively. The tertiary analysis included no cases of PML with EID. CONCLUSION: Natalizumab EID is associated with clinically and statistically significantly lower PML risk than SID. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that for patients with MS, natalizumab EID is associated with a lower PML risk than SID.

Effect of natalizumab on disease progression in secondary progressive multiple sclerosis (ASCEND): a phase 3, randomised, double-blind, placebo-controlled trial with an open-label extension.

BACKGROUND: Although several disease-modifying treatments are available for relapsing multiple sclerosis, treatment effects have been more modest in progressive multiple sclerosis and have been observed particularly in actively relapsing subgroups or those with lesion activity on imaging. We sought to assess whether natalizumab slows disease progression in secondary progressive multiple sclerosis, independent of relapses. METHODS: ASCEND was a phase 3, randomised, double-blind, placebo-controlled trial (part 1) with an optional 2 year open-label extension (part 2). Enrolled patients aged 18-58 years were natalizumab-naive and had secondary progressive multiple sclerosis for 2 years or more, disability progression unrelated to relapses in the previous year, and Expanded Disability Status Scale (EDSS) scores of 3·0-6·5. In part 1, patients from 163 sites in 17 countries were randomly assigned (1:1) to receive 300 mg intravenous natalizumab or placebo every 4 weeks for 2 years. Patients were stratified by site and by EDSS score (3·0-5·5 vs 6·0-6·5). Patients completing part 1 could enrol in part 2, in which all patients received natalizumab every 4 weeks until the end of the study. Throughout both parts, patients and staff were masked to the treatment received in part 1. The primary outcome in part 1 was the proportion of patients with sustained disability progression, assessed by one or more of three measures: the EDSS, Timed 25-Foot Walk (T25FW), and 9-Hole Peg Test (9HPT). The primary outcome in part 2 was the incidence of adverse events and serious adverse events. Efficacy and safety analyses were done in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT01416181. FINDINGS: Between Sept 13, 2011, and July 16, 2015, 889 patients were randomly assigned (n=440 to the natalizumab group, n=449 to the placebo group). In part 1, 195 (44%) of 439 natalizumab-treated patients and 214 (48%) of 448 placebo-treated patients had confirmed disability progression (odds ratio [OR] 0·86; 95% CI 0·66-1·13; p=0·287). No treatment effect was observed on the EDSS (OR 1·06, 95% CI 0·74-1·53; nominal p=0·753) or the T25FW (0·98, 0·74-1·30; nominal p=0·914) components of the primary outcome. However, natalizumab treatment reduced 9HPT progression (OR 0·56, 95% CI 0·40-0·80; nominal p=0·001). In part 1, 100 (22%) placebo-treated and 90 (20%) natalizumab-treated patients had serious adverse events. In part 2, 291 natalizumab-continuing patients and 274 natalizumab-naive patients received natalizumab (median follow-up 160 weeks [range 108-221]). Serious adverse events occurred in 39 (13%) patients continuing natalizumab and in 24 (9%) patients initiating natalizumab. Two deaths occurred in part 1, neither of which was considered related to study treatment. No progressive multifocal leukoencephalopathy occurred. INTERPRETATION: Natalizumab treatment for secondary progressive multiple sclerosis did not reduce progression on the primary multicomponent disability endpoint in part 1, but it did reduce progression on its upper-limb component. Longer-term trials are needed to assess whether treatment of secondary progressive multiple sclerosis might produce benefits on additional disability components. FUNDING: Biogen.

Risk of natalizumab-associated progressive multifocal leukoencephalopathy in patients with multiple sclerosis: a retrospective analysis of data from four clinical studies.

BACKGROUND: Previous estimates of risk of progressive multifocal leukoencephalopathy (PML) in patients with multiple sclerosis receiving natalizumab were stratified by three risk factors: anti-John Cunningham virus (JCV) antibodies in serum, previous immunosuppressant use, and treatment duration, which were estimated using population-based assumptions. We aimed to calculate PML risk estimates from patient-level risk-factor data and to stratify risk by concentrations of anti-JCV antibody in serum (anti-JCV antibody index). METHODS: Data on natalizumab-treated patients were pooled from four large, observational, open-label studies: STRATIFY-2, STRATA, TOP, and TYGRIS. Data were analysed with and without imputation for missing values of anti-JCV antibody status and previous immunosuppressant use. For anti-JCV antibody-positive patients in this pooled cohort, cumulative PML risk with or without previous immunosuppressant use was estimated using Kaplan-Meier analysis. Annual PML risks (per 12 natalizumab infusions) for patients without PML in the preceding year were estimated using conditional probability based on the life table method. For anti-JCV antibody-positive patients without previous immunosuppressant use, risk estimates were further stratified using a probability distribution for anti-JCV antibody index values, separately for patients with or without PML. Anti-JCV antibody index cutoffs were selected via sensitivity and specificity assessments for identifying PML cases in an index cohort. FINDINGS: 156 (<1%) of 37 249 patients in the pooled cohort had PML. We imputed missing values on anti-JCV antibody status (3912 patients) and on previous immunosuppresant use (544 patients) using a multiple imputation method. For anti-JCV antibody-negative patients (n=13 996), estimated PML risk was less than 0·07 per 1000 patients (95% CI 0·00-0·40). In anti-JCV antibody-positive patients (n=21 696), estimated cumulative PML probability over 6 years (72 infusions of natalizumab) was 2·7% (95% CI 1·8-4·0) in patients with previous immunosuppressant use and 1·7% (1·4-2·1) in those without. In patients without previous immunosuppressant use (n=18 616), estimated annual PML risks per 1000 patients, conditional on having no PML before that year, ranged from 0·01 (0·00-0·03) in year 1 (1-12 infusions) to 0·6 (0·0-1·5) in year 6 (61-72 infusions) for people with an index of 0·9 or less; from 0·1 (0·0-0·2) in year 1 to 3·0 (0·2-5·8) in year 6 for those with an index of more than 0·9 up to and including 1·5; and from 0·2 (0·0-0·5) in year 1 to 10·0 (5·6-14·4) in year 6 for those with an index of more than 1·5. INTERPRETATION: Our risk estimates calculated from patient-level clinical data allow individualised annual prediction of risk of PML in patients receiving natalizumab for multiple sclerosis, supporting yearly benefit-risk re-evaluation in clinical practice. Further, our estimates are generally consistent with previously calculated estimates. Incorporating anti-JCV antibody index allows further risk stratification for anti-JCV antibody-positive patients who have not previously taken immunosuppressants. FUNDING: Biogen.

Natalizumab reduces relapse clinical severity and improves relapse recovery in MS.

OBJECTIVES: Compare relapse clinical severity, post-relapse residual disability, and the probability of confirmed complete recovery from relapse between patients who relapsed during natalizumab (n=183/627 [29%]) and placebo (n=176/315 [56%]) treatments in the AFFIRM trial. METHODS: In this post-hoc analysis, relapse clinical severity and residual disability were defined by change in Expanded Disability Status Scale (EDSS) score occurring between pre-relapse and at-relapse assessment and between pre-relapse and post-relapse assessment, respectively. Patients were considered completely recovered from relapse when their post-relapse EDSS score was less than or equal to their pre-relapse EDSS score, and this was maintained for 12 or 24 weeks. RESULTS: At relapse, an increase in EDSS score of ≥0.5 points occurred in 71% of natalizumab and 84% of placebo patients (P=0.0088); an increase of ≥1.0 point occurred in 49% of natalizumab and 61% of placebo patients (P=0.0349) (mean increase in EDSS at relapse: natalizumab=0.77; placebo=1.09; P=0.0044). After relapse, residual disability of ≥0.5 EDSS points remained in 31% of natalizumab and 45% of placebo patients (P=0.0136) (mean post-relapse residual EDSS increase: natalizumab=0.06; placebo=0.28; P=0.0170). In patients with an increase in EDSS of ≥0.5 or ≥1.0 during relapse, natalizumab increased the probability of 12-week confirmed complete recovery from relapse by 55% (hazard ratio [HR]=1.554; P=0.0161) and 67% (HR=1.673; P=0.0319) compared to placebo, respectively. CONCLUSIONS: In AFFIRM, natalizumab treatment decreased the clinical severity of relapses and improved recovery from disability induced by relapses. These beneficial effects would limit the step-wise accumulation of disability.

Imaging neural activity using Thy1-GCaMP transgenic mice.

The ability to chronically monitor neuronal activity in the living brain is essential for understanding the organization and function of the nervous system. The genetically encoded green fluorescent protein-based calcium sensor GCaMP provides a powerful tool for detecting calcium transients in neuronal somata, processes, and synapses that are triggered by neuronal activities. Here we report the generation and characterization of transgenic mice that express improved GCaMPs in various neuronal subpopulations under the control of the Thy1 promoter. In vitro and in vivo studies show that calcium transients induced by spontaneous and stimulus-evoked neuronal activities can be readily detected at the level of individual cells and synapses in acute brain slices, as well as chronically in awake, behaving animals. These GCaMP transgenic mice allow investigation of activity patterns in defined neuronal populations in the living brain and will greatly facilitate dissecting complex structural and functional relationships of neural networks.

Nicotinic control of adult-born neuron fate.

The hippocampus is one of only two regions in the adult brain where neurons are generated in significant numbers throughout the lifetime of the animal. Numerous studies have demonstrated that these adult-born neurons are essential for optimal cognitive function with unimpaired memory formation and retrieval. The extent to which adult-born neurons survive through an early "critical period" and become integrated into functional networks has been shown to depend on the richness of stimulation they receive during these formative stages. The dentate gyrus in the hippocampus - home of the adult-born neurons - receives extensive cholinergic innervation, and newly generated neurons in the adult hippocampus express substantial numbers of both major types of neuronal nicotinic acetylcholine receptors. Early studies indicated that nicotinic signaling may be important for the development of adult-born neurons: repeated exposure to nicotine impaired their long-term survival. Recent studies with mutant mice lacking either one of the two major nicotinic receptor subtypes demonstrate that receptor loss results in fewer adult-born neurons surviving the critical period and becoming integrated into neural networks. The key nicotinic receptor mediating the largest effects is one that has a high relative permeability to calcium. In view of this feature, it may not be surprising that excessive exposure to nicotine can have detrimental effects on survival and maturation of adult-born neurons in the dentate; these same receptors appear to be key. The results pose serious challenges for therapeutic strategies targeting an individual class of nicotinic receptors for global treatment in the recipient.