Clinical features of antibody-induced complete secondary failure of botulinum toxin therapy

In some patients treated with botulinum toxin type A (BT), secondary therapy failure occurs. It can either be partial (PSTF) or complete (CSTF). One of the main causes for CSTF is the formation of antibodies against BT. We wanted to study the clinical features of BT antibody-induced CSTF to improve its detection. For this, 27 patients with various dystonic syndromes and antibody- failure were studied. In 22 patients CSTF was preceded by a total of 63 injection series with PSTF. The number of injection series with preceding PSTF was 2.52 +/- 2.37 with a range from 0 to 8. When PSTF occurred, the maximal efficacy of BT therapy was reduced on 55 occasions and the efficacy duration on 48 occasions. CSTF occurred after treatment times of 61-1,507 days with grouping around 324.9 +/- 148.9 days and 1,155.7 +/- 436.8 days and patients with short interinjection intervals significantly overrepresented in the first group (Mann-Whitney U test, p = 0.009). Sex and age at initiation of BT therapy, single BT dose, and number of booster injection series were not different in both groups. Immunological complications could not be detected in any of the patients. Clinical features of antibody failure described in this study show that the shorter the interinjection intervals, the earlier antibody failure occurs. They make it highly unlikely for patients with long-standing BT therapy to develop antibody failure, and they might be useful to identify antibody failure before elaborate BT antibody testing is initiated.