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

Automated Poisson regression exposure-response analysis for binary outcomes with PoissonERM

PoissonERM is an R package used to conduct exposure-response (ER) analysis on binary outcomes for establishing the relationship between exposure and the occurrence of adverse events (AE). While Poisson regression could be implemented with glm(), PoissonERM provides a simple way to semi-automate the entire analysis and generate an abbreviated report as an R markdown (Rmd) file that includes the essential analysis details with brief conclusions. PoissonERM processes the provided data set using the information from the user's control script and generates summary tables/figures for the exposure metrics, covariates, and event counts of each endpoint (each type of AE). After checking the incidence rate of each AE, the correlation, and missing values in each covariate, an exposure-response model is developed for each endpoint based on the provided specifications. PoissonERM has the flexibility to incorporate and compare multiple scale transformations in its modeling. The best exposure metric is selected based on a univariate model's p-value or deviance (Δ D $$ \Delta D $$ ) as specified. If a covariate search is specified in the control script, the final model is developed using backward elimination. PoissonERM identifies and avoids highly correlated covariates in the final model development of each endpoint. Predicting event incidence rates using external (simulated) exposure metric data is an additional functionality in PoissonERM, which is useful to understand the event occurrence associated with certain dose regimens. The summary outputs of the cleaned data, model developments, and predictions are saved in the working folder and can be compiled into a HTML report using Rmd.

Disease activity and neonatal outcomes after exposure to natalizumab throughout pregnancy

BACKGROUND

After natalizumab discontinuation severe relapses can occur despite pregnancy, but third trimester exposure is associated with neonatal haematological abnormalities (HA). The best time point for stopping natalizumab during pregnancy is unclear.

METHODS

Prospective, observational cohort with 350 natalizumab exposed pregnancies from the German Multiple Sclerosis and Pregnancy Registry. Clinical disease activity and neonatal outcomes are compared between women with natalizumab discontinuation during (1st Trim-group) versus after the first trimester (maintaining-group) and for subgroup analysis before (<30-subgroup) or after (≥30-subgroup) the 30th gestational week (gw).

RESULTS

Baseline characteristics did not significantly differ between the 1st Trim-group (n=179; median exposure duration: 2.60 gw, IQR 1.30-3.60) and the maintaining-group (n=171; median exposure duration: 30.9 gw, IQR 26.9-33.3). Fewer relapses occurred during pregnancy and the postpartum year in the maintaining-group (25.7%) compared with the 1st Trim-group (62.6%; p<0.001). Women in ≥30-subgroup had a significantly lower relapse risk in the first 6 months postpartum (relapse rate ratio: 0.36, 95% CI: 0.15 to 0.84). In total, 7.5% retained meaningful disability 12 months postpartum. No significant effect on neonatal outcomes were observed, but anaemia (OR: 2.62, 95% CI: 1.12 to 6.52) and thrombocytopaenia (OR: 2.64, 95% CI: 1.15 to 6.46) were significantly more common in the ≥30-subgroup. 21.8% of all neonates were born small for gestational age, independent of the timing of natalizumab discontinuation.

CONCLUSION

Continuing natalizumab during pregnancy after gw 30 decreases the relapse risk postpartum going along with a higher risk for HA in the newborns. These results add relevant knowledge as a basis for informed risk-benefit discussion.

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 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.

ClinicalTrials.gov identifier:

NCT00493298

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.

Pregnancy outcomes amongst multiple sclerosis females with third trimester natalizumab use

BACKGROUND

Natalizumab, a monoclonal antibody directed against alpha-4-integrin, is an efficacious treatment used in Multiple Sclerosis (MS). Use in early pregnancy is safe but information in the third trimester is limited. Ceasing natalizumab is often associated with an increased risk in MS relapse and in some instances natalizumab continuation during pregnancy may be required. However natalizumab crosses the placenta in late pregnancy and has been associated with hematological abnormalities. We present clinical and hematological outcome data of newborns from a series of MS patients who received natalizumab during their second and third pregnancy trimesters. We describe possible methods to mitigate risks to the fetus.

METHODS

Retrospective chart review of 15 births from mothers receiving natalizumab throughout pregnancy.

RESULTS

Thirteen mothers with third-trimester exposure to natalizumab were identified. Median age at conception was 34 years (26-40) and median disease duration was 53.5 months (11-204). The 13 mothers gave birth to 15 newborns (2 mothers each with 2 individual births), median (SD) birth weight was 2778 gs (2100 - 3790). Congenital or laboratory abnormalities were identified in 5 which included anemia (n = 2) and thrombocytopenia (n = 3).

CONCLUSIONS

Complications following natalizumab administration during the second and third trimester of pregnancy occurred in 33% of newborns. However, did not result in mortality or morbidity. Dose alterations during the third trimester, pre-delivery umbilical cord sampling and IVIG administration may reduce hematological effects on newborns. Prospective studies with larger numbers of patients are required to provide further evidence regarding the safety of Natalizumab use in pregnancy.

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.