NapFFKKK peptide hydrogel delivers Botulinum Toxin A, extending strabismus correction to 2 months and reducing ptosis
Background
Strabismus, a condition of ocular misalignment, is commonly treated with Botulinum Toxin Type A (BTXA) injections. However, the efficacy of free BTXA is often limited by its rapid diffusion from the injection site, leading to unintended paralysis of non-target extraocular muscles. This off-target effect frequently causes complications like ptosis (drooping eyelid) and necessitates repeated injections due to reduced therapeutic duration. There is a critical need for advanced delivery systems that can localize BTXA activity, thereby enhancing its safety and extending its therapeutic window.
Study Design
Researchers co-assembled the pentapeptide hydrogelator Nap-Phe-Phe-Lys-Lys-Lys (NapFFKKK) with Botulinum Toxin A (BTXA) under physiological conditions to create a supramolecular hydrogel, Gel Nap+BTXA. They evaluated its physicochemical properties, cytocompatibility, and hemocompatibility in vitro. The in vitro drug release profile and in vivo drug diffusion were assessed using single-photon emission computed tomography (SPECT) imaging. For in vivo efficacy, Gel Nap+BTXA was intramuscularly injected into the superior rectus muscles of rabbits, comparing its therapeutic effects on ocular alignment and ptosis, as well as biosafety, against a control arm receiving free BTXA solution.
Results
Co-assembly of BTXA with NapFFKKK successfully formed Gel Nap+BTXA, characterized by a well-organized nanofibrous network and enhanced mechanical strength. Crucially, this formulation maintained the biological activity of BTXA while enabling sustained drug release. In vivo experiments demonstrated a significant improvement in local toxin retention: > Compared to free BTXA solution, Gel Nap+BTXA showed about 3.1-fold higher local retention of the toxin at 24 h post-injection. This enhanced localization translated into superior therapeutic outcomes. Gel Nap+BTXA effectively alleviated ptosis and provided more stable and long-lasting ocular alignment correction, extending the therapeutic effect up to 2 months. Furthermore, the study reported no detectable ocular or systemic toxicity associated with Gel Nap+BTXA treatment, indicating a favorable safety profile.
Key Findings
- NapFFKKK peptide co-assembled with BTXA to form a stable hydrogel (
Gel Nap+BTXA) maintaining BTXA's biological activity. Gel Nap+BTXAshowed 3.1-fold higher local toxin retention at 24 h post-injection compared to free BTXA.- The hydrogel formulation effectively alleviated ptosis in rabbits.
- Ocular alignment correction was stable and lasted up to 2 months with
Gel Nap+BTXA. - No detectable ocular or systemic toxicity was observed with
Gel Nap+BTXA.
Why It Matters
This localized delivery strategy for Botulinum Toxin A represents a significant advancement for strabismus treatment, potentially reducing the frequency of injections and mitigating common side effects like ptosis. For clinicians and patients, this could mean a more effective and safer therapeutic option, improving patient comfort and compliance. The use of a self-assembling peptide hydrogel offers a biocompatible and biodegradable platform, moving closer to a clinically translatable protocol. This approach could lead to longer-lasting effects from BTXA, requiring fewer interventions and minimizing off-target adverse events. While currently demonstrated in rabbits, the principles of localized, sustained release are highly relevant for human applications, suggesting a promising future for enhanced neurotoxin therapies.
botulinum-toxin-a
napffkkk
strabismus
hydrogel
localized-delivery
neurotoxin