FDA regulatory guidance
In the United States, "biological products" are subject to a different premarket pathway and differing intellectual property protections than products regulated only as drugs. Biologic and drug legislation also provides different schemes for resolving patent issues regarding entry of follow-on products or biosimilar products. While the US Food and Drug Administration is getting ready to approve the first biosimilar product, there is a history of products approved under abbreviated pathway in the United States for years. Many biologics cannot be tested in commonly used animal species, such as rats and dogs, because of their biological activity and species or tissue-specific activity. Many biologics are capable of eliciting immune responses, which can affect preclinical study results. In some cases, these effects are desired, but unwanted immunogenicity might be harmful. Sponsors usually must conduct pharmacodynamic studies, such as in vitro binding assays and in vivo studies that assess the product's pharmacological activity and define its mechanism of action.