Sensitive studies with a significant dose-response curve for inhaled corticosteroids to investigate equivalent relative potency are feasible

Regulatory Considerations for Approval of Generic Inhalation Drug Products in the US, EU, Brazil, China, and India

This article describes regulatory approaches for approval of "generic" orally inhaled drug products (OIDPs) in the United States, European Union, Brazil, China and India. While registration of a generic OIDP in any given market may require some documentation of the formulation and device similarity to the "original" product as well as comparative testing of in vitro characteristics and in vivo performance, the specific documentation approaches, tests and acceptance criteria vary by the country. This divergence is due to several factors, including unique cultural, historical, legal and economic circumstances of each region; the diverse healthcare and regulatory systems; the different definitions of key terms such as "generic" and "reference" drug; the acknowledged absence of in vitro in vivo correlations for OIDPs; and the scientific and statistical issues related to OIDP testing (such as how best to account for the batch-to-batch variability of the Reference product, whether to use average bioequivalence or population bioequivalence in the statistical analysis of results, whether to use healthy volunteers or patients for pharmacokinetic studies, and which pharmacodynamic or clinical end-points should be used). As a result of this discrepancy, there are ample opportunities for the regulatory and scientific communities around the world to collaborate in developing more consistent, better aligned, science-based approaches. Moving in that direction will require both further research and further open discussion of the pros and cons of various approaches.

Generics, chemisimilars and biosimilars: is clinical testing fit for purpose?

The effectiveness and safety of generic drugs are backed by sound physicochemical control and regulatory bioequivalence acceptance criteria. Statistical testing of bioequivalence, comparing the pharmacokinetic profiles of the test and reference products, was made possible by modern drug assays. When the pharmacokinetic profile correlates with the dose, such comparisons show assay sensitivity and readily detect differences in dose. For large biological molecules, different manufactured batches cannot be validated using pharmacokinetic data alone. For these biosimilars, there is a three-stage assessment of pharmaceutical quality, laboratory testing and clinical data. This approach has also been applied to certain chemical products, termed 'chemisimilars', which have variable or complex synthesis of the active substance, or complex formulation, or a complex delivery device. Although there may be no detectable difference between the test and reference on clinical testing, many of the outcome measures are insensitive to even large differences in dose. For testing to be fit for purpose it should distinguish important dose differences, but many clinical tests of chemisimilars and biosimilars do not. As pharmacokinetic and pharmacodynamic technology advances, the trend of replacing dose-insensitive clinical trial data with equivalence tests that show assay sensitivity can be expected to continue.