IncobotulinumtoxinA: A Highly Purified and Precisely Manufactured Botulinum Neurotoxin Type A

Inc.) is composed of the 150 kDa BoNT-A with a peptide excipient, RTP-004, derived from the human immunodeficiency virus type 1 (HIV-1) transactivator of transcription (TAT) protein.²¹ In naturally occurring BoNT, the NTNHA protein directly binds to BoNT, protecting it from low pH and proteolytic cleavage in the gastrointestinal tract,²² while HA proteins help to transport the BoNT into the bloodstream through interactions with intestinal epithelial cells.^23-25 By protecting the BoNT from digestive destruction, the complexing proteins increase the toxicity of native BoNT compared with the purified BoNT when ingested via oral route.²⁶ Contrary to their role as mediator for the oral toxicity of naturally occurring BoNT, complexing proteins have no role in clinical applications.^17,27 Stability of the commercial BoNT complex (300, 500, 900 kDa) is pH dependent and dissociates from the active 150 kDa BoNT with a half-life of 17 Furthermore, unnecessary clostridial proteins also do not appear to contribute to the stability of BoNT in the commercially manufactured vial. IncobotulinumtoxinA remained stable, with no effects on the content (neurotoxin or excipients) or the biological activity of the BoNT, when stored unreconstituted with refrigeration or at ambient temperatures for ≤48 months, and under elevated temperatures ≤60°C (140°F) for one month.²⁸ Efficacy was also retained when incobotulinumtoxinA was stored at 25°C (77°F) for one week post-reconstitution.²⁹ IncobotulinumtoxinA is the only currently approved BoNT-A formulation that can be stored unreconstituted at ambient temperatures, which may be a benefit in everyday clinical practice. Because incobotulinumtoxinA does not require coldchain storage, this can be advantageous during the summer months, in temperate countries, in practices with limited space, or in outpatient clinics where refrigeration may be problematic. Besides the practical and clinical implications, it should be taken into consideration that greenhouse gas emissions due to secondary shipping and handling of non-temperature-controlled versus temperature-controlled BoNT reduces our carbon footprint.⁶³

Although unnecessary clostridial proteins play no role in clinical applications when injected,^17,27 or in stabilizing the molecule,^17,28 they may act as adjuvants, stimulating an immune response, thus potentially altering the response to BoNT therapy.²⁷ Two types of antibodies may be produced in response to injected BoNT; neutralizing antibodies against BoNT itself have been reported³⁰ and can lead to reduced efficacy or treatment non-response, even at the low doses indicated for aesthetic applications.^31,32 The non-neutralizing antibodies directed against the unnecessary clostridial proteins do not affect the biological activity of the neurotoxin, but the unecessary clostridial proteins may act as adjuvants.^30,33,34 Two pre-clinical studies suggest an adjuvant role for unnecessary proteins, increasing the antigenicity of injected BoNT.^33,35 Unnecessary clostridial proteins, but not pure BoNT-A, stimulated an immune response by modulating the inflammatory response.^33,36 However, results should be interpreted with caution as these studies included formal- dehyde-fixed proteins, non-comparable dosing, and shorter injection intervals than those used in clinical practice. Although the extent of non-response in aesthetics is unknown, reports of neutralizing antibody development are increasing.^32,37 Individuals are increasingly initiating aesthetic treatment earlier in life.³ As BoNT treatment effects are temporary, and repeat injections are required to maintain efficacy,³² clinicians should consider both the temporal extent of exposure² and BoNT protein load to reduce the risk of neutralizing antibody formation and treatment non-response.³² Previous exposure for use in aesthetics may lead to non-response if BoNT-A were required for essential therapeutic treatment (eg, of post-stroke spasticity) later in life. In contrast to abobotulinumtoxinA and onabotulinumtoxinA, repeated incobotulinumtoxinA treatment in rabbits did not result in the formation of neutralizing antibodies, suggesting immunogenicity is lower with incobotulinumtoxinA.³⁸ Consistent with this, incobotulinumtoxinA is the only formulation with no subjects in clinical studies who have developed neutralizing antibodies and demonstrated a secondary lack of treatment response in the PI/SmPC product characteristics.^1,6,10 A recent analysis of the US FDA adverse event (AE) reporting system database found the incidence of AEs involving decreased therapeutic effect was 2.2% (15/689) for incobotulinumtoxinA; 9.2% (79/858) for abobotulinumtoxinA; and 11.6% (1247/10,733) for onabotulinumtoxinA. Reduced efficacy was more frequent among subjects on >1 year of treatment vs <1 year for both abobotulinumtoxinA (11.9% [36/302] vs 4.3% [11/257]) and onabotulinumtoxinA (19.6% [504/2577] vs 10.1% [539/5350]), but not incobotulinumtoxinA (0.0% [0/10] vs 4.5% [13/291] cases).³⁹

IncobotulinumtoxinA is purified and precisely manufactured in a world-class German facility using advanced technology under Good Manufacturing Practice. The unnecessary clostridial proteins are removed in a refined process using step-wise chromatography to precisely isolate the therapeutic component