Disclosures: Rashid Kazerooni, PharmD, MS, BCPS: Merz North America (Products/Services: Yes) (Employment)

Objective : Sufficient long term data comparing botulinum neurotoxin type A (BoNT-A) agents for antibody formation, resistance, and loss of effect is lacking. IncobotulinumtoxinA is the only BoNT-A agent that has removed unnecessary proteins, leaving just the 150 kDa active component. The aim of this analysis was to assess the BoNT-A agents for decreased therapeutic effect over time.

Design: BoNT-A cases were included when it was considered the “Primary Suspect” drug. All three US Food and Drug Administration (FDA) approved BoNT-A agents which have both cosmetic and therapeutic indications were included (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA).

Setting : The FDA Adverse Event Reporting System (FAERS) database was utilized.

Participants : The analysis was conducted on data between March 2014 and June 2019.

Interventions: N/A

Main Outcome Measures: The primary outcome was relative rate of decreased therapeutic effect over time by drug, defined as presence of ‘therapeutic response decreased’ and/or ‘drug effect decreased’ being reported as an adverse event. This relative rate methodology has been well described previously in the pharmacovigilance literature.

Results: A total of 23,789 unique BoNT-A cases were included across a wide array of cosmetic and therapeutic indications. Relative incidence of decreased therapeutic effect for patients on >1 year of treatment versus < 1 year was significantly higher for onabotulinumtoxinA [14.4% (609/4219) vs 7.6% (753/9909); p>0.001] and abobotulinumtoxinA [9.9% (59/597) vs 3.3% (38/1144); p < 0.001]. This phenomenon was not observed with incobotulinumtoxinA [0.0% (0/34) vs 3.7% (18/485); p=0.62.

Conclusions: Causal relationships cannot be established from pharmacovigilance analyses. However, a clear safety signal was detected in this analysis of one of the largest BoNT-A safety data sets ever researched. Long term differences in decreased BoNT-A therapeutic effect by agent warrants further study, including whether even lower dose indications are not immune from this phenomenon over time.

Level of Evidence: Level III

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/decreased-therapeutic-effect-over-time-amongst-botulinum-toxin-type-a-agents/