**1. Introduction**

### **1.1 Overview of drug approval agencies**

Drug approval agencies are responsible for the oversight and scientific evaluations that ensure the safety and effectiveness of the drugs that reach the market, and eventually, patients. Several agencies regulate drug approval worldwide, with the United States (US) and Europe being the top regulators. Some examples include the US Food and Drug Administration (FDA), the European Medicines Agency (EMA), Health Canada, Japan's Pharmaceutical and Medical Devices Agency (PMDA), Australia's Therapeutic Goods Administration (TGA), and so on [1]. In the last 5 years, the US FDA has approved about 245 drugs, many of which include anti-cancer and neurological disorder drugs [2]. Following drug discovery and preclinical trials, different types of applications can be filed to the FDA to begin a drug's journey to the market. A sponsor can either file the Investigational New Drug (IND) application followed by the New Drug Application (NDA) or the Abbreviated New Drug Application (ANDA). An IND application is submitted if

a drug is deemed safe after preclinical investigations. Then, an NDA can be submitted after the drug is deemed safe from the clinical trial results. At this point, a request can be made to produce and market the drug in the US [3]. On the other hand, ANDA is filed for the approval of generic drugs. Although clinical studies are not needed for this application, sponsors must prove that their drug is similar and bioequivalent to the original approved branded counterpart [4]. In the European Union, sponsors submit a clinical trial application (CTA) followed by a marketing authorization through either a centralized process or a decentralized process [3, 5]. Notably, both the FDA and EMA have similar yet distinct regulatory mechanisms to categorize drug approvals. For example, the FDA may grant drugs a standard approval, fast-track designation, accelerated approval, breakthrough designation, or priority review. Similarly, besides the standard approval, the EMA has accelerated assessment and conditional approval for expedited programs to bring a drug to market faster [5]. Taken together, these drug approval agencies do participate in a global collaborative effort to protect and improve public health by ensuring patients' timely access to safe and effective medicines [6].
