Flow cytometry and drug-monitoring of natalizumab saturation of immune cells in multiple sclerosis1)

Abstract

Background: Natalizumab (Tysabri) is a blocking antibody specific to the α -4 integrin subunit and can be detected on the surface of immune cells by flow cytometry. We investigated if the determination of natalizumab saturation of immune cells has the potential to act as a biomarker for treatment effectiveness in multiple sclerosis (MS). Methods: Natalizumab saturation of immune cells from 11 patients was measured before the start of treatment and after 4, 8, and 12 weeks of natalizumab therapy on T cells (CD3 + ) and T cell subsets [naive (CD45RA + /memory (CD45R0 + ) CD4 + and CD8 + ] by flow cytometry. Results: At weeks 4, 8, and 12 the average (n = 9) natalizumab saturation of T cells approximated 80%. One patient with natalizumab neutralizing antibodies (NABs) and another patient with irregular infusion intervals were identified by abnormalities in the natalizumab saturation of cells. Different α -4 expression levels of T cell subpopulations were irrelevant to measuring cellular natalizumab saturation. Conclusions: We showed that monitoring natalizumab saturation of T cells by flow cytometry is a useful and routine-qualified method to identify patients with a reduced treatment effect due to NABs or irregular infusion intervals. Further studies to determine a cut-off value for suboptimal natalizumab saturation of immune cells will also show the potential of this parameter concerning more individualized treatment schedules. Considering the risk of opportunistic infections it is very important to increase the safety of this highly effective MS therapy.

A routine-qualified flow cytometric method for the identification of multiple sclerosis patients with a reduced therapeutic effectiveness of natalizumab

“…It is important to have a biomaker which is informative if the treatment can be effective. This study, and previous studies from our group, have shown that the natalizumab saturation level of immune cells can be such a biomarker [11,12] . We demonstrated the importance of regular 4-weekly infusion intervals by showing that patients experience strong fluctuations in their cellular natalizumab saturation levels in case of prolonged infusion intervals of 6 -8 weeks [12] .…”

“…This study, and previous studies from our group, have shown that the natalizumab saturation level of immune cells can be such a biomarker [11,12] . We demonstrated the importance of regular 4-weekly infusion intervals by showing that patients experience strong fluctuations in their cellular natalizumab saturation levels in case of prolonged infusion intervals of 6 -8 weeks [12] . Furthermore, we demonstrated in a patient with NAB that freshly infused natalizumab transiently neutralized NAB to the end that serum NAB were no longer detectable but natalizumab saturation levels of immune cells had recovered.…”

“…Natalizumab saturation levels of T cells were analyzed using a 5-color flow cytometer (Cytomics FC500, Beckman Coulter, Vienna, Austria). The natalizumab saturation level (in %, also see formula) of the T cells was then determined by relating the median fluorescence intensity (MFI) of in vivo bound natalizumab to the MFI of in vitro saturated immune cells (10 μ g/mL, representing 100% natalizumab saturation) [12] .…”

“…However, other studies indicated that natalizumab saturation levels of immune cells are a more robust parameter than CD49d expression levels for drawing conclusions about the success of natalizumab treatment [11,12] . In the current study, we examined whether analyzing the natalizumab saturation level on T lymphocytes by flow cytometry represents a sensitive method to early identify patients with a reduced therapeutic success and increased probability of infusion-related side effectiveness due to NAB.…”

Routine-taugliche durchflusszytometrische Methode zur Identifikation von Multiple Sklerose PatientInnen mit einer nicht ausreichenden Therapieeffizienz unter einer Natalizumab-Therapie

“…Andere Studien zeigten jedoch, dass der NatalizumabSättigungsgrad ein stabilerer Parameter ist als die CD49d-Expression, um Rückschlüsse auf den Therapieerfolg von Natalizumab ziehen zu können [11,12]. Der NatalizumabSättigungsgrad berechnet sich aus dem Vergleich von in vivo gebundenen Natalizumab und dem in vitro mit Natalizumab gesättigten Immunzellen.…”