[Open use of natalizumab. Neutralising antibodies and clinical data]

New insights into the pharmacokinetics and pharmacodynamics of natalizumab treatment for patients with multiple sclerosis, obtained from clinical and in vitro studies

BACKGROUND

The monoclonal antibody natalizumab (NAT) inhibits the migration of lymphocytes throughout the blood-brain barrier by blocking very late antigen (VLA)-4 interactions, thereby reducing inflammatory central nervous system (CNS) activity in patients with multiple sclerosis (MS). We evaluated the effects of different NAT treatment regimens.

METHODS

We developed and optimised a NAT assay to measure free NAT, cell-bound NAT and VLA-4 expression levels in blood and cerebrospinal fluid (CSF) of patients using standard and prolonged treatment intervals and after the cessation of therapy.

RESULTS

In paired CSF and blood samples of NAT-treated MS patients, NAT concentrations in CSF were approximately 100-fold lower than those in serum. Cell-bound NAT and mean VLA-4 expression levels in CSF were comparable with those in blood. After the cessation of therapy, the kinetics of free NAT, cell-bound NAT and VLA-4 expression levels differed. Prolonged intervals greater than 4 weeks between infusions caused a gradual reduction of free and cell-bound NAT concentrations. Sera from patients with and without NAT-neutralising antibodies could be identified in a blinded assessment. The NAT-neutralising antibodies removed NAT from the cell surface in vivo and in vitro. Intercellular NAT exchange was detected in vitro.

CONCLUSIONS

Incorporating assays to measure free and cell-bound NAT into clinical practice can help to determine the optimal individual NAT dosing regimen for patients with MS.

Pregnancy and natalizumab: results of an observational study in 35 accidental pregnancies during natalizumab treatment

BACKGROUND

Natalizumab, a therapeutic monoclonal antibody approved for the treatment of relapsing-remitting multiple sclerosis (RRMS), is recommended to be withdrawn 3 months prior to a planned pregnancy. Our aim was to analyse the safety and impact of natalizumab exposure on course of disease and pregnancy outcome.

OBJECTIVES

Prospective follow-up of women with MS who became accidentally pregnant during natalizumab treatment in comparison with pregnancies of women with MS not exposed to disease-modifying treatments (DMT).

METHOD

35 women with MS who became accidentally pregnant while treated with natalizumab, and 23 women with MS who became pregnant devoid of any DMT as a control group, were chosen.

RESULTS

All pregnancies except one were followed in a prospective fashion. Of the women exposed to natalizumab during pregnancy, 29 women gave birth to 28 healthy children; one child was born with hexadactyly. Five pregnancies ended in an early miscarriage and one woman decided to undergo an elective termination of pregnancy. MS activity did not rebound during pregnancy or post partum after natalizumab was withdrawn, and no significant differences were observed when compared with the non-DMT-exposed control group.

CONCLUSION

Our data may support the notion that an elective termination of pregnancy due to natalizumab exposure may not be necessary, but rather requires careful monitoring. Women should still be advised to stop natalizumab in the course of planned pregnancy until more data on long-term outcomes are available.

[Choice of early and escalation treatment options for multiple sclerosis]

Recent advances in understanding of the immunopathogenesis of multiple sclerosis (MS) have led to the development of new treatment options. To date several immunomodulatory agents have been licensed for the treatment of relapsing-remitting MS. However, some debate remains on the optimal time point for initiating therapy. While there is general consensus on the benefit of an early treatment start, the issues of how to define "early MS" and how to identify patients with a "benign" disease course have not yet been finally addressed. Further open questions include the situations of treatment failure and therapeutic escalation. Here we summarize available data from studies on early treatment with immunomodulatory drugs for a first demyelinating event, also referred to as clinically isolated syndrome. Furthermore, options for the escalation of immunomodulatory therapy will be discussed, e.g. with the recently licensed monoclonal antibody natalizumab.