**1. Introduction**

Generic medicines find application in both chemotherapy and supportive care in oncology. Generics are increasingly available for small molecules and biologic agents used in oncology treatment regimens.

Generic medicines are pharmaceutical drugs that have the same chemical substance, i.e., the same active pharmaceutical ingredient (API), as that of the originator drug. According to the US Food and Drug Administration (FDA), "a generic drug is a medication created to be the same as an existing approved brand-name drug in dosage form, safety, strength, route of administration, quality, performance characteristics, and intended use [1]." According to the European Medicines Agency (EMA), "a generic medicine is developed to be the same as a medicine that has already been authorized, called the reference


#### **Table 1.**

*Key differences between generic medicines and biosimilar agents.*

medicine [2]." These regulatory directions of similarity imply the possible substitution of innovator products with generic medicines. According to the World Health Organization (WHO), a generic is a 'multisource pharmaceutical product which is intended to be interchangeable with the comparator product.' This also includes an originator brand for which the patent has expired. WHO has distinguished between originator brand, regardless of its patent status, and lowest-priced generic equivalents [3]. Biosimilars are defined as biologic products that are highly similar to reference products, notwithstanding minor differences in clinically inactive components. Biosimilars have no clinically meaningful differences to the reference product in terms of safety profile, purity, and potency [4]. Both generics and biosimilars are widely used in cancer care. However, there are several differences between the two agents (**Table 1**) [5].

Generic medicines may differ from the originator products in the manufacturing processes. There may be subtle differences in the excipients, color, and packaging. Sometimes, generic medicines may also have different formulations. According to the EMA, "a generic medicine's inactive ingredients, name, appearance and packaging can be different [2]." Approval of generics and biosimilars are granted after confirmation of evidence of biophysical similarity to the originator reference products. This is a proxy to similarity in the clinical effectiveness and safety of generics and biosimilars. Generics and biosimilars are approved only when there is 'totality of evidence' for similarity to the reference originator product. This includes robust scientific data for parameters of structural analysis, preclinical, pharmacokinetic, efficacy and safety, and immunogenicity.
