Characterization of diffusion and duration of action of a new botulinum toxin type A formulation.

RT002, an injectable form of botulinum neurotoxin type A (BoNTA), comprised of a purified 150 kDa neurotoxin formulated in a novel formulation, is designed to limit the extent of diffusion and permit safe administration of longer acting doses. The aim of this study was to evaluate the degree of diffusion of RT002 in comparison to another commercially available BoNTA product, Botox® Cosmetic (OnabotulinumtoxinA, Allergan, Inc., Irvine, CA, USA), and establish the relative duration of effect for diffusion matched doses of the two BoNTA formulations using quantitative measurements in mice. Measurement of muscle paralysis by muscle force generation (MFG) in mice at the injected gastrocnemius muscles indicated that RT002 and Botox are equipotent. Measurements of MFG inhibition in an adjacent muscle, the tibialis anterior muscle, indicated significantly less diffusion for RT002 as compared to Botox. When RT002 and Botox were dosed using the established diffusion matched doses, RT002 treatment resulted in an extended duration of drug effect as compared to Botox by 58-100% as assessed by either partial or complete recovery endpoints. Use of a daily voluntary running activity model provided confirmation that the two BoNTA formulations are equipotent by daily running distance and further confirmed the diffusion matched dose ratio assessed by degree of drug effect on body weight gain. Using these diffusion matched doses, RT002 treatment resulted in an extended duration of drug effect as compared to Botox (100-126% increase in duration) as assessed by either partial or complete recovery endpoints. Use of this model provides further evidence that the RT002 formulation limits diffusion with equipotency and thereby may permit safe administration of higher and more efficacious doses. In summary, data from two murine models suggest that RT002 may represent a next generation of BoNTA drug formulation offering superior degree and duration of effect at the intended target while controlling the unwanted diffusion and accompanying adverse effects of BoNTA at neighboring muscles and distal systemic targets.