Using Metabolite Data to Develop Patient Centric Specification for Amide Impurity in Vildagliptin Tablets

Many specified impurities in vildagliptin's finished product have been disclosed in the literature that are above their qualification threshold. We used the impurity B (amide impurity) as a case example to explore whether existing literature can be leveraged to determine the safe level of impurity and thereby develop a patient-centric specification (PCS) for impurities. No-observed-adverse-effect level (NOAEL) was derived from rate metabolism information and converted to human equivalent dose (HED). The HED was estimated as 6.5 mg/day. The high qualification levels are supported by repeat dose toxicity studies performed in rats, mice and dogs. Maximum theoretical amount (MTA) was correlated with the maximum observed amount (MOA) to verify whether the exposure was due to impurity and/or metabolite. MOA/MTA was found ≥1 suggesting that metabolism contributed to the amount excreted in feces and therefore could be used to further justify a higher specification limit than the usual one of ≤0.5%. Quite often the drug metabolism and degradation pathways overlap, resulting in the formation of identical constituents. Therefore, metabolism data can be leveraged for deriving safe levels of degradation impurities and develop PCS for impurities.

Repeat-Dose Toxicity Study Using the AFPL1-Conjugate Nicotine Vaccine in Male Sprague Dawley Rats

Tobacco smoking is the cause of 20% of Canadian deaths per year. Nicotine vaccines present a promising alternative to traditional smoking cessation products, but to date, no vaccine has been able to move through all phases of clinical trials. We have previously demonstrated that the AFPL1-conjugate nicotine vaccine does not induce systemic or immunotoxicity in a mouse model and that a heterologous vaccination approach is more advantageous than the homologous routes to inducing mucosal and systemic anti-nicotine antibodies. The purpose of this study was to confirm the safety profile of the vaccine in a repeat-dose toxicity study. The heterologous vaccination strategy was again used, and Sprague Dawley rats were administered a dose five times greater than in our previous studies. Physiological conditions, food and water consumption, body temperature, injection site inflammation, relative weights of organs, histopathology, and blood chemistry and hematology were evaluated during the course of the vaccination period to determine the safety of the vaccine. The AFPL1-conjugate nicotine vaccine did not induce clinically relevant changes or induce symptoms that would be associated with toxicity, making it a promising candidate for future investigations.