Chapter two gives an overview on the whole drug discovery process, from basic approaches of drug discovery to marketing.
Chapter one and two constitutes the first module of the course.
Drug discovery pipeline
This section focuses on the concept of target-based discovery and the drug-discovery pipeline. In addition, concepts and practices of phenotype-based drug discovery are introduced.
I recommend a resource provided by the course’s instructor: for the general audience, a video made by Roche Pharma Research and Early Development (Roche pRED), highlights very well the principle of target identification. This is the link to the video, available on Youtube.com. I recommend this video not because I work for Roche pRED, but because it uses cartoons and simple languages to show how target identification in principle works.
The three phases of clinical trials are Phase I (mainly for safety reasons, with 10-20 enrolled persons), Phase II (mainly for efficacy, with 100-200 enrolled patients), and Phase III (for regulatory approval, with 1,000-2,000 enrolled patients). In some cases, such as the Influenza Resistance Information Study (IRIS) study that I was participating, a Phase IV study is needed to monitor the efficacy, and sometimes like in the Influenza study, the consequences (e.g. viral mutation) of the drug.
Phase Ia and Ib
Phase I trials are divided into two parts: phase Ia and Ib. Phase Ia studies are usually very small and normally only involve healthy volunteers. It is about short-term safety information and beginning to understand the half-life and metabolism of the drug in humans. In Phase Ib, patients (not healthy volunteers) are participating so researchers can understand how the disease state affects short-term safety, half-life, and metabolism of the clinical candidates.
In case highly toxic compounds (e.g. for oncology) are tested, phase Ia can recruit patients instead of healthy volunteers.
Phase IIa and IIb
In non-oncology indications, Phase IIa provides the hypothesis, i.e. the efficacy and/or mechanisms (proof of concept, proof of mechanism) of the drug in a limited number of patients. It may include some dose range exploration, but does not need to.
Phase IIb, in a larger group of patients, represents the definitive dose-range or finding, i.e. determining the doses that show efficacy with minimal side effects.
The Phase IIb study is designed to guide the dose selection for the larger, pivotal Phase III studies. Phase IIb studies also typically use the expected final formulation of the drug, while Phase IIa does not.
Intellectual property and patent
Currently, a patent has a term of 20 years. Drug patents are usually filed around the preclinical stage in order to prevent other companies adopting the same idea and filing their own patents.
The anecdotes on Ranitidine and Ritonavir show that polymorphism, i.e. different crystallisation forms of the same drug molecules, can have effects on bioavailability and can complicate the patenting process.
Task: use molinspiration to design a molecule with high specificity against one type of drug targets over other types. The six types of drug targets for which a bioactivity score is predicted are:
- GPCR (ligand)
- Ion channel (modulator)
- Kinase (inhibitor)
- Nuclear receptor (ligand)
- Protease (inhibitor)
- Enzyme (inhibitor)
- IND: Investigational New Drug