Predicting bioequivalence and developing dissolution bioequivalence safe space in vitro for warfarin using a Physiologically-Based pharmacokinetic absorption model

OBJECTIVE

Bioequivalence (BE) studies support the approval and clinical use of both new and generic drug products. Narrow therapeutic index (NTI) drugs have relatively high costs and low success rates of BE evaluation clinical trials as high-risk drugs. A physiologically-based pharmacokinetic (PBPK) model can be used to evaluate the BE of two preparations.

METHODS

This study inputs the basic physical and chemical property parameters of warfarin sodium available at the present stage into GastroPlus™ software, and combined it with the Advanced Compartmental Absorption and Transit (ACAT™) model built into the software. The PBPK model of Chinese individuals taking 2.5 mg of warfarin sodium orally while fasted condition was developed using the disposal parameters calculated from the clinically measured PK data of the reference preparations. The model was tested using the PK data of other reference preparations and tested preparations from different domestic manufacturers.

RESULTS

The results revealed that at least 30% of drugs are released in 30 min under a pH of 4.5 condition, and at least 80% are released in 30 min under a pH of 6.8 condition, which can be used as bioequivalent dissolution limits under fasted conditions. The risk of BE failure in the fed condition will be significantly reduced for the clinical study on the BE of warfarin sodium, which is a NTI drug if the fasted condition is bioequivalent.

CONCLUSION

The results revealed that the PBPK models were successfully developed for 2.5 mg of warfarin sodium tablets in Chinese individuals. Developing a PBPK model for NTI drugs based on in vitro dissolution data in software is a promising method for BE evaluation, which can provide great help for developing new drugs and the clinical trial research of BE of generic drugs.

[Clinical characteristics of "classical" and "non-classical" paraneoplastic neurological syndrome]

Objective: To explore the clinical features of classical and non-classical paraneoplastic neurological syndrome (PNS). Methods: From 2015 to 2020, 48 cases of definite PNS admitted to the First Affiliated Hospital of University of Science and Technology of China were retrospectively collected, and classification, clinical characteristics, onconeural antibodies and primary tumors were analyzed. The included cases were divided into classical and non-classical groups according to Graus criteria, and the differences of clinical characteristics, onconeural antibodies, combined tumors, time of diagnosis and mortality were compared between the two groups. Results: Among the 48 confirmed patients, 21 (43.8%) were positive for well-characterized onconeural antibodies. There were 28 cases (58.3%) and 20 cases (41.7%) in classic and non-classical PNS groups, respectively. No significant differences of age, sex, clinical involvement site, characteristic positive antibody type, tumor diagnosis rate and follow-up mortality were found between the two groups (all P>0.05). The time of diagnosis in the non-classical PNS group was 3.0 (2.0, 6.5) months, which was significantly longer than that in the classical PNS group 1.0(0.6, 3.0) months (P<0.05). Meanwhile, the combination rate of non-characteristic antibodies in the classical PNS group (10 cases, 35.7%) was significantly higher than that in the non-classical PNS group (1 case, 5.0%) (P=0.016). During the follow-up, 39 patients (81.3%) with tumor were confirmed, and 29 patients (60.4%) were diagnosed with PNS before the tumor was found. Conclusions: The"non-classical"PNSs are common in clinical settings. Diagnosis may be delayed due to the nonclassical symptoms of the patients. When patients have clinical symptoms related to PNS, onconeural antibodies should be detected and the relevant tumors should also be screened. Patients have positive antibodies but with no tumors should be closely followed up for more than 5 years.