Prediction of antibody persistency from antibody titres to natalizumab.

BACKGROUND

In a subgroup of patients with multiple sclerosis natalizumab therapy causes generation of anti-natalizumab antibodies that may be transient or persistent. It is recommended to discontinue natalizumab therapy in persistently antibody-positive patients.

OBJECTIVE

To use titres of anti-natalizumab antibodies to predict persistency of antibodies.

PATIENTS AND METHODS

In 525 consecutive natalizumab treated patients tested for anti-natalizumab antibodies 43 (8.2%) were antibody-positive. Thirty of the antibody-positive patients, who were tested both at three and at six months after treatment start, had antibody titres in blood measured using an extended ELISA method.

RESULTS

Samples from persistently positive patients ( N =18) had higher titre values than samples from transiently positive patients ( N =12). A cut-off value for high titre values was generated, above which patients may discontinue natalizumab therapy after three months. The method had a sensitivity of 0.83, a specificity of 1.00 and a diagnostic accuracy of 0.90.

CONCLUSION

An extended ELISA method for measuring anti-natalizumab antibody titres in multiple sclerosis patients on natalizumab therapy may be used for evaluation of antibody persistence. A test at three months may identify patients with high titres, who should discontinue natalizumab therapy, and patients with transient low-titre antibodies, who may continue natalizumab therapy despite development of antibodies.