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Background: Patients with multiple sclerosis (MS) or Crohn's disease (CD) being treated with natalizumab (Tysabri®, Biogen) who are planning to become pregnant or discover they are pregnant after exposure to natalizumab are currently advised to balance the potential benefits and potential risks of exposure when considering treatment options. This study was undertaken to evaluate pregnancy outcomes of women with MS or CD who were exposed to natalizumab at any time within 3 months prior to conception or during pregnancy. A pregnancy registry was created to better understand the effect of natalizumab exposure on pregnancy outcomes. Methods: The Tysabri Pregnancy Exposure Registry was a global, observational exposure registration and follow-up study. Evaluations included spontaneous abortions (<22 weeks gestational age), fetal losses (≥22 weeks gestational age), ectopic pregnancies, elective or therapeutic terminations, stillbirths, birth defects, and live births. Birth defects were reviewed and coded in accordance with the Metropolitan Atlanta Congenital Defects Program (MACDP) classification of birth defects. Results: A total of 369 patients with MS and 7 patients with CD were enrolled prospectively, of whom 355 patients (99.4 %; 349 MS and 6 CD) had known pregnancy outcomes (including 8 twin sets). The spontaneous abortion rate was 9.0 % (n = 32; 95 % confidence interval [C. I.], 6.3-12.5 %). An independent advisory committee review determined the major birth defect rate to be 5.05 % (16 of 316 live births + 1 elective abortion; 95 % C. I., 2.9-8.1 %). The mean gestational age of the live-born infants was 38.3 weeks, and the mean birth weight was 3158.3 g. Conclusions: Although the overall rate of birth defects was higher than that observed by the MACDP, these registry outcomes showed no specific pattern of malformations that would suggest a drug effect, and the spontaneous abortion rate was consistent with that of the general population. Trial Registration: ClinicalTrials.gov NCT00472992 (11 May 2007). [ABSTRACT FROM AUTHOR]

Objective As of 3 September 2013, 399 cases of natalizumab-associated progressive multifocal leukoencephalopathy ( PML) were confirmed in multiple sclerosis ( MS) patients. We evaluated outcomes of natalizumab-treated MS patients who were asymptomatic at PML diagnosis. Methods Analyses included data available as of 5 June 2013. Asymptomatic patients diagnosed with PML by magnetic resonance imaging ( MRI) findings and JC virus DNA detection in the central nervous system were compared with patients presenting with symptoms at diagnosis. Demographics, MRI, and survival over 12 months were analyzed. Expanded Disability Status Scale ( EDSS) and Karnofsky Performance Scale ( KPS) scores were recorded pre- PML, at diagnosis, and at 6 and 12 months post-diagnosis. Results A total of 372 PML cases were analyzed; 30 patients were asymptomatic and 342 were symptomatic at PML diagnosis. Classifications of PML lesions on MRI in asymptomatic versus symptomatic patients were unilobar in 68% versus 37%, multilobar in 21% versus 24%, and widespread in 11% versus 40%. In both groups with unilobar lesions, frontal lobe lesions predominated. Prior to PML, mean EDSS and KPS scores were similar for asymptomatic and symptomatic patients. At diagnosis, mean EDSS score was significantly lower for asymptomatic patients (4.1; n = 11) than for symptomatic patients (5.4; n = 193; P = 0.038). Six months after PML diagnosis, asymptomatic patients had less functional disability than symptomatic patients. As of 5 June 2013, 96.7% of asymptomatic patients and 75.4% of symptomatic patients were alive. Interpretation PML patients asymptomatic at diagnosis had better survival and less functional disability than those who were symptomatic at diagnosis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]