Comparative evaluation of the potency and antigenicity of two distinct BoNT/A-derived formulations

Abstract

IncobotulinumtoxinA (Xeomin®) and onabotulinumtoxinA (BOTOX®) are unique botulinum neurotoxin type A (BoNT/A)-derived drugs. IncobotulinumtoxinA utilizes the naked 150 kDa holotoxin portion of BoNT/A, whereas onabotulinumtoxinA uses the complete native 900 kDa complex as drug substance. On the basis of purportedly similar pharmacological characteristics, these formulations were evaluated for potency by LD₅₀ and mouse Digit Abduction Score (DAS) bioassays. DAS was also used to assess antigenicity. Full-range DAS dose-response profiles were achieved with four lots of each product, with similar observations between lots for a given product. Between products, however, the mean DAS potency of incobotulinumtoxinA (ED₅₀ range 7.0-10.2 U/kg) was significantly lower than that of onabotulinumtoxinA (ED₅₀ range 4.4-6.4 U/kg), consistent with lower measured potencies in the LD₅₀ assay for incobotulinumtoxinA (potency range 62-82 U). In assessments of DAS duration of effect at similar unit doses, the observed lower potency of incobotulinumtoxinA translated into decreased peak efficacy and dose effect over time (i.e. shorter duration). In contrast, at equi-efficacious doses yielding near-maximal DAS responses, both toxin formulations were uniformly inhibited in a statistically significant manner when preincubated with rabbit-derived, onabotulinumtoxinA-neutralizing antibodies, supporting the position that inhibition of 150 kDa holotoxin serves as the common basis for neutralization and, therefore, incobotulinumtoxinA would not be expected to be effective in onabotulinumtoxinA-immunoresistant subjects (and vice versa). Further, with lower lot-to-lot relative potency, incobotulinumtoxinA is not dose-equivalent or interchangeable with onabotulinumtoxinA, suggesting that various aspects of drug product formulation may influence observed pharmacology.

Pharmacological differences and clinical implications of various botulinum toxin preparations: a critical appraisal

“…When BoNTA was evaluated against the Allergan 100-unit standard, under Allergan assay conditions, the activity of incobotulinumtoxinA was less than 100 Allergan units (i.e., 69 to 78 units over three different tested lots). These results were replicated in other assays (Brown et al, 2013), confirming that, due to underlying product differences, assay conditions markedly influence potency measurements. In a mouse model, the potency of BoNT products in inducing hind limb paresis resulted in an estimated conversion ratio of incobotulinumtoxinA and onabotulinumtoxinA of between 1: 0.75 and 1: 0.5 (Kutschenko et al, 2016).…”

“…This was confirmed by recent in vivo studies showing that, on a labeled unit-to-unit basis, onabotulinumtoxinA displayed greater biological activity and potency than incobotulinumtoxinA (Canty et al, 2017). Moreover, the mean digit abduction score (DAbS) of median effective dose (ED50) potency of incobotulinumtoxinA (ED50 range 7.0-10.2 U/kg) was significantly lower than that of onabotulinumtoxinA (ED50 range 4.4-6.4 U/kg), consistent with lower measured potencies in the LD50 assay for incobotulinumtoxinA (potency range 62-82 U) (Brown et al, 2013). The extent and duration of the biological effect of BoNT in humans have been tested using the frontalis test or the extensor digitorum brevis test for all BoNT products (Marion et al, 2016).…”

“…Animal models of muscle weakening have shown non-parallel dose-response curves, which indicate that dose ratio changes depend on the level of muscleweakening efficacy or on specific mortality rates (Aoki, 2001). A more recent study that used DAbS to compare the ED 50 of different BoNTAs showed that a DAbS of 2 could be obtained with 6 U of onabotulinumtoxinA and 10 U of incobotulinumtoxinA (Brown et al, 2013). Overall, onabotulinumtoxinA showed greater efficacy and longer effect duration than incobotulinumtoxinA at both high and low dosages in the DAbS model (Brown et al, 2013 (Marion et al, 1995) 1: 3 NA (Nussgens and Roggenkamper, 1997;Roggenkamper et al, 2006) 1: 4 AbobA>OnabA (Sampaio et al, 1997) 1: 4 AbobA>OnabA (Bihari, 2005) 1: 4 -1: 5 NA (Bentivoglio et al, 2012) 1: 1 -1: 13.3 NA (Dodel et al, 1997) 1:4 -1:6 AbobA>OnabA Cervical dystonia (Naumann et al, 2003) 1: 5 -1: 6 AbobA=OnabA (Odergren et al, 1998) 1: 3 AbobA=OnabA (Ranoux et al, 2002) 1: 3 -1: 4 AbobA>OnabA (Bihari, 2005) 1: 4 -1: 5 NA (Misra et al, 2012) 3.1: 1 AbobA>OnabA (Rystedt et al 2015) 1.7: 1 NA (Yun et al 2015) 2.5: 1 AbobA=OnabA (Dodel et al, 1997) 1:4 -1:6 AbobA>OnabA (Van den Bergh and Lison, 1998) 1: 2.5 AbobA=OnabA Hemifacial spasm (Marion et al, 1995) 1: 3 NA (Bihari, 2005) 1: 4 -1: 5 NA (Dodel et al, 1997) 1:4 -1:6 AbobA>OnabA (Van den Bergh and Lison, 1998) 1: 2.5 AbobA=OnabA Spasticity (Rasmussen, 2000) 1: 4 NA (Bhakta et al, 1996) 1: 4 -1: 5 NA (Hesse et al, 2012) 1: 5 NA ( Keren-Capelovitch, et al 2010) 1: 2.5 NA Abbreviations: OnabA =OnabotulinumtoxinA; AbobA=AbobotulinumtoxinA; NA=not available/not applicable © C I C E d i z i o n i I n t e r n a z i o n a l i at least 12 months, were administered increasing doses of onabotulinumtoxinA until a similar response to that obtained with abobotulinumtoxinA was observed.…”

In-vivo comparison of the neurotoxic potencies of incobotulinumtoxinA, onabotulinumtoxinA, and abobotulinumtoxinA

“…However, recent animal studies suggest a lower potency for A/Inco [6,8,15]. Conflicting results have also been reported for the conversion ratio between A/Ona and A/Abo.…”

“…However, the mouse LD50 test is not internationally standardized and differs between the manufacturers. This results in not identical MUs of the BoNT/A preparations [6][7][8]. Further disadvantages of this test are that one cannot measure the effect duration and that BoNT is injected intraperitoneally and not intramuscularly.…”