Systematic Review and Meta‐Analysis of Secondary Treatment Failure and Immunogenicity with Botulinum Neurotoxin A in Multiple Indications—Comment on Recommending <scp>IncobotulinumtoxinA</scp> as First‐Line to Prevent Secondary Treatment Failure [Letter]

I read with interest the systematic review and meta-analysis by Walter et al. [1] on secondary treatment failure (STF) and neutralizing antibodies (NAbs) formation with botulinum neurotoxin type A (BoNT-A). The authors provide a valuable compilation of the available literature. However, I am concerned that the concluding recommendation favoring incobotulinumtoxinA as a first-line strategy to prevent these immunogenicity-related outcomes may go beyond what the current evidence can robustly support. Importantly, clinical failure is multifactorial. As Walter et al. [1] acknowledge, there is a complex and non-linear relationship between neutralizing antibodies and clinical failure, with a substantial proportion of partial secondary failure occurring without detectable antibodies, consistent with prior meta-analytic evidence [5]. Technical factors (muscle selection, dosing, injection interval, use of guidance, and disease progression) remain key determinants of apparent loss of response. Therefore, while differences in antigenic load may be plausible, the current evidence does not justify a definitive clinical hierarchy. Clinical practice should therefore continue to prioritize optimized technique, appropriate dosing, and individualized injection intervals rather than endorsing a specific formulation as a first-line strategy, while awaiting independent, long-term, head-to-head studies using harmonized STF definitions. Fabiano Nadson Magacho-Vieira: conceptualization, investigation, writing – original draft, writing – review and editing. No photos or patient personal information are in this manuscript. No institutional approval was required for this publication. The author confirms that this manuscript adheres to the ethical policies of the journal, as noted on the journal's author guidelines page. Dr. F.N. Magacho-Vieira is the medical director of Dermadream Corporation Brazil. The author reports no other conflicts of interest in this communication. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.