Characterization of exposure-Clinical Dementia Rating-Sum of Boxes relationship in subjects with early Alzheimer's disease from the aducanumab Phase 3 trials.

Clinical Dementia Rating-Sum of Boxes (CDR-SB) assessments from two Phase 3 studies (ENGAGE and EMERGE) of aducanumab in subjects with early Alzheimer's disease (AD) were pooled to develop an exposure-response (ER) model. A linear model in the logit-transformed scaled CDR-SB best characterized the time profile for placebo- and aducanumab-treated subjects, with concentration as the exposure metric. The model allowed delineation of slow (4%), typical (86%), and fast (10%) progressing subpopulations in the data. The estimated drug effect on the disease progression rate was significant, 2.05 L/(g·year), with a 95% confidence interval (1.60, 2.50) that did not include zero. Following an evaluation of a series of ER model forms including differential drug and null effects either between the studies or among the three progression classes, the final ER model with a common (pooled) estimate of the drug effect between the studies and among the three progression classes was considered parsimonious. The final model provides supportive evidence that the two studies demonstrate a common intrinsic pharmacology. None of the identified covariates (Mini-Mental State Examination-BL score and Asian race) were clinically meaningful. Finally, simulations demonstrated that the intrinsic pharmacology remained consistent between the two Phase 3 studies.

A randomized study of natalizumab dosing regimens for relapsing-remitting multiple sclerosis.

BACKGROUND: REFINE was an exploratory, dose- and frequency-blinded, prospective, randomized, dose-ranging study in relapsing-remitting multiple sclerosis (RRMS) patients. OBJECTIVE: To examine the efficacy, safety, and tolerability of natalizumab administered via various regimens in RRMS patients. METHODS: Clinically stable RRMS patients previously treated with 300 mg natalizumab intravenously for ⩾12 months were randomized to one of six natalizumab regimens over 60 weeks: 300 mg administered intravenously or subcutaneously every 4 weeks (Q4W), 300 mg intravenously or subcutaneously every 12 weeks (Q12W), or 150 mg intravenously or subcutaneously Q12W. The primary endpoint was the mean cumulative number of combined unique active magnetic resonance imaging (MRI) lesions at week 60. RESULTS: In total, 290 patients were enrolled. All Q12W dosing arms were associated with increased clinical and MRI disease activity and closed early; ⩾39.5% of patients in each Q12W arm met rescue criteria. In the 300 mg intravenous and subcutaneous Q4 W arms, the mean cumulative number of combined unique active MRI lesions was 0.23 and 0.02, respectively; annualized relapse rates were 0.07 and 0.08, respectively; and trough natalizumab serum levels and α4-integrin saturation were comparable. CONCLUSION: Natalizumab 300 mg subcutaneous Q4W was comparable to 300 mg intravenous Q4W dosing with respect to efficacy, pharmacokinetics/pharmacodynamics, and safety.

Exposure-disease response analysis of natalizumab in subjects with multiple sclerosis.

Natalizumab, a human immunoglobulin monoclonal antibody that targets α4ß1/α4ß7 integrin, is an effective therapy approved for the treatment of multiple sclerosis (MS). The objective of this analysis was to develop a population exposure-response model utilizing gadolinium-enhancing (Gd) lesion count data from four clinical studies and annualized relapse rate (ARR) data from three clinical studies. The natalizumab exposures were derived for the individuals using a population pharmacokinetic model. A log-linear exposure effect on Gd lesion count and ARR adequately characterized the relationship between exposure and disease response. In the case of the Gd lesion count model, a bimodal model that distributed subjects into two subpopulations based on low or high baseline Gd lesion count provided a superior goodness of fit. The mean (95% confidence interval) slopes from the exposure-Gd lesion count model and exposure-ARR model are -0.0903 (-0.100, -0.081) and -0.0222 (-0.026, -0.015) (mg/L)-1, respectively. From these slopes, it can be inferred that both Gd lesion count and ARR decrease with increasing exposure to natalizumab in MS subjects. Model-based simulations demonstrated that although reductions in Gd lesion count and ARR were observed with lower doses (75, 150, or 200 mg), only the dose of 300 mg every 4 weeks (q4w) was associated with an ARR ≤0.25 and was considered clinically effective. The results from the exposure-Gd lesion count and exposure-ARR models thus support the appropriateness of the approved natalizumab dose (300 mg q4w) in MS subjects.

A Time-to-Event Exposure-Response Model for Amyloid-Related Imaging Abnormalities Following Administration of Aducanumab to Subjects With Early Alzheimer Disease.

Amyloid-related imaging abnormalities with edema (ARIA-E) have been reported in patients with early Alzheimer disease treated with aducanumab. ARIA-E incidence has been observed to be dependent on both dose and apolipoprotein E4 carrier status. A time-to-event (TTE) approach applying data from 2 phase 3 studies (studies 301 and 302) was used to describe the effect of aducanumab serum exposure on the instantaneous risk of 2 end points: the first incidence of ARIA-E and time to ARIA-E resolution. A total of 3251 subjects with 826 events supported the TTE model to characterize the first ARIA-E event. The TTE resolution model was supported by data from 768 of 826 subjects who had ARIA-E resolved. Relationships between drug concentrations and ARIA-E events were modeled with a hazard function dependent on time, aducanumab serum concentrations, attenuation of aducanumab exposure effects with time (ie, potential for tolerance to aducanumab exposure), study, and apolipoprotein E4 carrier status. The TTE model showed that ARIA-E incidence rates were higher during the first 200 days, followed by a reduction in rates. The change in event rate reflects the attenuation of drug effect, thereby providing support for the current proposed titration regimen. Time to ARIA-E resolution was characterized by a constant baseline hazard with a probability to resolution affected by baseline ARIA-E severity and aducanumab concentration. ARIA-E resolution was found to be driven primarily by baseline hazard and time and suggested that aducanumab concentration effect is a minor contributor to the time to resolution of ARIA-E.

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.

Safety of the tau-directed monoclonal antibody BIIB092 in progressive supranuclear palsy: a randomised, placebo-controlled, multiple ascending dose phase 1b trial.

BACKGROUND: Progressive supranuclear palsy is a rare neurodegenerative disease associated with dysfunctional tau protein. BIIB092 is a humanised monoclonal antibody that binds to N-terminal tau and is thus being assessed as a potential novel treatment for progressive supranuclear palsy. We aimed to investigate the safety and tolerability of BIIB092 in individuals with progressive supranuclear palsy. METHODS: This 12-week, double-blind, randomised, placebo-controlled, multiple ascending dose, phase 1b trial was done at 13 outpatient sites in the USA. Participants aged 41-86 years with probable or possible progressive supranuclear palsy with a score of 20 or greater on the Mini-Mental State Examination (MMSE) were enrolled. Three BIIB092 dose escalation cohorts (150 mg, 700 mg, or 2100 mg; eight participants per cohort) were tested sequentially. For each dose cohort, the first two participants were randomly assigned by a computer-generated scheme to receive either BIIB092 or placebo intravenously every 4 weeks for 57 days. After 2 days, the six remaining participants in each cohort were randomly assigned (5:1) to receive BIIB092 or placebo for 57 days. An additional expansion panel of 24 patients was randomly assigned (3:1) to receive 2100 mg or placebo every 4 weeks for 57 days. All participants were followed up to day 85. The primary outcome was safety, which was analysed in the treated population (all enrolled participants who received at least one dose of the study drug). This trial is registered with ClinicalTrials.gov, NCT02460094. FINDINGS: Between Oct 2, 2015, and Oct 19, 2016, 48 participants were enrolled and randomly assigned to the BIIB092 (n=36) and placebo (n=12) groups. No apparent demographic differences were observed between the two groups at baseline. All 48 participants completed the treatment phase of the study. Adverse events were generally mild to moderate in severity; the most common in the placebo and BIIB092 groups were falls (in two [17%] of 12 patients and in ten [28%] of 36 patients), urinary tract infections (in one [8%] of 12 and in six [17%] of 36), contusions (in one [8%] of 12 and in five [14%] of 36), and headaches (in none and in five [14%] of 36). Four serious adverse events resulting in admission to hospital were reported in three participants who received BIIB092 2100 mg: two severe adverse events of urinary tract infection, one severe adverse event of change in mental status, and one moderate adverse event of aspiration pneumonia. None was considered to be related to the study drug, all were resolved, and no deaths were reported. INTERPRETATION: Repeated administration of the anti-tau monoclonal antibody BIIB092, at doses of up to 2100 mg, appears to be well tolerated in participants with progressive supranuclear palsy. Results of this phase 1b trial have informed the design of the ongoing phase 2 PASSPORT (NCT03068468) study to examine the efficacy and safety of BIIB092. FUNDING: Bristol-Myers Squibb, Biogen.

Population Pharmacokinetics and Target Engagement of Natalizumab in Patients With Multiple Sclerosis.

Natalizumab (humanized immunoglobulin G4 antibody targeting alpha-4 integrins) is a highly efficacious treatment for relapsing-remitting multiple sclerosis (RRMS) that has been in clinical use since 2006. However, natalizumab pharmacokinetic (PK) characteristics and concentration alpha-4 integrin saturation relationships have not been well described in the scientific literature. Therefore, clinical data from 11 studies were pooled and analyzed to characterize the PK and pharmacodynamic (PD) properties of natalizumab in RRMS subjects. Natalizumab PK was best described using a 2-compartment model with linear first-order and Michaelis-Menten elimination. Subcutaneous absorption of natalizumab was characterized using first-order absorption with lag time. The relationship between natalizumab concentration and alpha-4 integrin saturation (PD) was best described by a direct response model with a sigmoidal effect on alpha-4 integrin saturation mediated by a maximum effect relationship with natalizumab concentrations. Covariate analysis showed that body weight, product formulations, and the presence of antinatalizumab antibodies were the main covariates affecting natalizumab PK, whereas age and formulations affected PD. The use of simulations based on a pharmacokinetic-pharmacodynamic model showed that covariates, although statistically significant, are not expected to have any clinical impact at the approved clinical dosing regimen of natalizumab (300 mg once every 4 weeks).

Reversibility of the effects of natalizumab on peripheral immune cell dynamics in MS patients.

OBJECTIVE: To characterize the reversibility of natalizumab-mediated changes in pharmacokinetics/pharmacodynamics in patients with multiple sclerosis (MS) following therapy interruption. METHODS: Pharmacokinetic/pharmacodynamic data were collected in the Safety and Efficacy of Natalizumab in the Treatment of Multiple Sclerosis (AFFIRM) (every 12 weeks for 116 weeks) and Randomized Treatment Interruption of Natalizumab (RESTORE) (every 4 weeks for 28 weeks) studies. Serum natalizumab and soluble vascular cell adhesion molecule-1 (sVCAM-1) were measured using immunoassays. Lymphocyte subsets, α4-integrin expression/saturation, and vascular cell adhesion molecule-1 (VCAM-1) binding were assessed using flow cytometry. RESULTS: Blood lymphocyte counts (cells/L) in natalizumab-treated patients increased from 2.1 × 109 to 3.5 × 109. Starting 8 weeks post last natalizumab dose, lymphocyte counts became significantly lower in patients interrupting treatment than in those continuing treatment (3.1 × 109 vs 3.5 × 109; p = 0.031), plateauing at prenatalizumab levels from week 16 onward. All measured cell subpopulation, α4-integrin expression/saturation, and sVCAM changes demonstrated similar reversibility. Lymphocyte counts remained within the normal range. Ex vivo VCAM-1 binding to lymphocytes increased until ≈16 weeks after the last natalizumab dose, then plateaued, suggesting reversibility of immune cell functionality. The temporal appearance of gadolinium-enhancing lesions was consistent with pharmacodynamic marker reversal. CONCLUSIONS: Natalizumab's effects on peripheral immune cells and pharmacodynamic markers were reversible, with changes starting 8 weeks post last natalizumab dose; levels returned to those observed/expected in untreated patients ≈16 weeks post last dose. This reversibility differentiates natalizumab from MS treatments that require longer reconstitution times. Characterization of the time course of natalizumab's biological effects may help clinicians make treatment sequencing decisions. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that the pharmacodynamic markers of natalizumab are reversed ≈16 weeks after stopping natalizumab.

A Randomized Trial Evaluating Various Administration Routes of Natalizumab in Multiple Sclerosis.

The study's primary objective was to compare the pharmacokinetics (PK) and pharmacodynamics (PD) of single subcutaneous (SC) or intramuscular (IM) 300-mg doses of natalizumab with IV 300-mg doses of natalizumab in patients with multiple sclerosis (MS). Secondary objectives included investigation of the safety, tolerability, and immunogenicity of repeated SC and IM natalizumab doses. DELIVER was a 32-week, open-label, multicenter study of natalizumab-naive patients with relapsing-remitting MS (RRMS) or secondary progressive MS (SPMS) randomized to receive 300 mg natalizumab by SC injection, IM injection, or IV infusion. PK and PD were evaluated over 8 weeks after the first natalizumab treatment (Part 1) and over 24 weeks with repeated dosing every 4 weeks, beginning at week 8 (Part 2). Seventy-six patients (24 with RRMS and 52 with SPMS) were enrolled in DELIVER. Following SC or IM administration of natalizumab, peak serum concentrations were approximately 40% of those observed with IV administration and showed no major differences in elimination characteristics. Mean bioavailability relative to IV administration was 57.1% to 71.3% with SC administration and 48.7% with IM administration; mean trough serum concentrations were similar with SC or IV administration and lower with IM administration. Following single or multiple doses of natalizumab, PD response was comparable across administration routes and disease stages. No meaningful differences were observed across administration groups in the incidence or nature of overall adverse events, serious adverse events, administration site reactions, hypersensitivity reactions, or antinatalizumab antibodies. These findings support the comparability of PD measures of natalizumab administered IV, SC, or IM.