The road toward drug development is risky and depends on several complex factors. On average, a single drug needs more than a billion dollars in investment and can take 14 years or more to reach the market shelf. Besides, each drug product has to clear stringent regulatory criteria backed by robust clinical and preclinical data.
The current article discusses the drug development timeline, from initial discovery to post-marketing monitoring. The drug development process flowchart consists of five main phases; discovery, preclinical studies, clinical studies, regulatory approval, and post-marketing analysis. So let us dive deep and understand the drug discovery process in detail.
Discovery and drug development
Drug discovery is the starting phase of drug development. Generally, drug developers employ high throughput screening to assess compounds against a specific molecular target. Compounds passing this initial screening stage moves on to the next step in the drug development timeline.
Often large libraries of compounds are assessed through computers. This approach, called the in-silico approach, focuses on identifying specific relationships that might be exploited in subsequent in vitro studies.
Moreover, bioequivalence studies of drug products are often needed for generic drugs. The US FDA has bioequivalence guidelines for comparing the bioavailability of generic and reference-listed drugs.
Once potential drug compounds pass the initial screening stage, they are tested in animal models. These animal models include rats, mice, and especially mammals, who can help predict drug safety and efficacy in subsequent human trials. However, there is growing consensus on reducing the number of animals used in preclinical studies. Drug developers focus on 3Rs, reduce, refine and replace animal use in preclinical studies. Modern approaches, can be used in preclinical research, such as an organ on a chip that mimics human organs.
After acquiring robust preclinical data, drug developers apply for IND submissions. Once the US FDA approves the drug for human testing, sponsors begin with human trials. The human trials have three main phases, Phase I, II, and III.
The Phase I trials test the drug in a small number of healthy subjects and determine a safe dosage. Next, a larger study population with the target disease is enrolled in the trial. Phase II trial focuses on assessing drug safety and efficacy in the intended patient population. Finally, in Phase III clinical trials, thousands of patients are tested with the pharmaceutical drug for efficacy and safety.
Upon completion of clinical trials, data is submitted to the US FDA for approval. Generally, the FDA takes ten months for approval to market the drug to the patient population.
Even after receiving FDA approval, sponsors must monitor the drug post-marketing. This stage helps sponsors and regulatory agencies monitor the long-term effects of the pharmaceutical drug product. The post-marketing analysis is particularly important for drugs that have received accelerated approval. Besides, the number of individuals consuming the drug also increases exponentially.
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Hence, the drug development process is lengthy and costly and is associated with risks at every step in the drug development timeline.