How a new medicine is developed: from lab to pharmacy

How does drug discovery start in the laboratory?

Drug discovery begins when researchers identify a biological target. This is often a gene or protein involved in a disease process. Once the target is identified, researchers search for a molecule that can act on it. This early work usually takes place in university laboratories or pharmaceutical company research units, funded by research bodies or industry grants^[1].

As many as 10,000 compounds may be considered at this stage. Researchers narrow this down to around 10 to 20 candidates. These are molecules that could theoretically interfere with the disease process. Candidate molecules can be found among natural compounds from plants, fungi or marine organisms. Increasingly, they are also designed from scratch using knowledge of genetics and protein structure with the help of computer modelling^[1].

A candidate molecule is first tested in laboratory systems such as antibodies or cultured cells. This early screening checks whether it shows the biological activity researchers are looking for^[2]. None of this laboratory work involves people. It helps scientists decide which ideas are worth testing further before any human volunteer is involved^[3]. This early filtering matters enormously, because it is far cheaper and quicker to discard a poor candidate in a test tube than to discover the same problem years later in a costly human trial^[2].

What happens during preclinical testing before a medicine reaches humans?

During preclinical development, promising molecules known as "leads" are produced in small quantities. They are then studied in more detail using computerised models, cells and animal studies to check safety and effect^[2][1]. Scientists also assess how the compound could be manufactured at larger scale. At the same time, they consider whether it would be well absorbed if taken orally^[2].

Around half of the candidates that enter preclinical testing make it through this stage. This leaves roughly five to ten compounds ready to be tested in humans for the first time. Before any testing in people can begin, the company must submit a clinical trial application. This is reviewed by medical and scientific experts. They decide whether enough preliminary evidence exists to justify moving into human trials. Their judgement rests on the accumulated laboratory and animal data gathered so far. Only when this evidence is considered sufficiently robust is permission granted to expose human volunteers to the candidate medicine for the first time^[1]. This preclinical stage typically takes several years and forms the evidence base that regulators later scrutinise when deciding whether a first-in-human study can go ahead at all^[2].

What is a clinical trial and why is it different from laboratory research?

A clinical trial, also called an interventional study, tests the safety and effectiveness of a medical intervention in living people rather than in a laboratory setting. Such interventions include a medicine, a procedure or a device. Clinical trials study interventions on people's health. Every drug, device, diagnostic test and technique used in medicine today was once tested in volunteers who took part in a clinical research study^[3].

Clinical research studies need people of every age, health status, gender, ethnicity and background. This diversity increases the chances that a treatment will be safe and effective across the whole population that will eventually use it. Volunteers are carefully screened before being accepted into a study, mainly because of safety considerations. Participation is always voluntary, and you can leave a trial at any time and for any reason^[3].

What happens in each phase of a clinical trial?

Clinical trials of new medicines move through a series of phases. Each phase is designed to answer a different question about safety and effectiveness before larger numbers of people are exposed to the treatment. New medicines are usually compared against a control, which is either a dummy treatment (placebo) or a standard treatment already in use^[4]. Specialist centres dedicated to early-phase trials, such as those run by cancer research organisations, help coordinate this process by linking laboratory scientists with clinicians who run first-in-human studies^[5].

Phase	Main purpose	Typical number of participants	Key detail for patients
Phase 1	Test safety and side effects; work out the right dose	20–100, often healthy volunteers	Doses start small and only increase if earlier volunteers show no or only minor side effects[4]
Phase 2	Check short-term effects in people who have the condition; find the most effective dose and method of delivery	100–500 patients	Most drugs that fail during clinical trials fail at this stage, usually due to lack of effect or safety concerns[1]
Phase 3	Confirm effectiveness and safety against an existing treatment or placebo in a much larger population	1,000–5,000, often across multiple countries	Trials often last a year or more[4][1]
Phase 4	Continue studying safety, side effects and effectiveness once the medicine is in everyday use	Varies	Only carried out on medicines that have already passed all earlier phases and received a marketing licence; not required for every medicine[4]

Phase 1: how do researchers find a safe starting dose?

In a Phase 1 trial, a small number of people, who may be healthy volunteers, receive the medicine for the first time in humans. Researchers test for side effects and calculate what dose might be appropriate for later treatment. They start with small doses and increase them only if volunteers tolerate them well^[4]. At least half of the compounds tested at this stage are usually considered safe enough to progress to Phase 2^[1].

Phase 2: does the medicine work, and at what dose?

Phase 2 trials test the new medicine in a larger group of people who actually have the condition it is meant to treat. This gives researchers a better idea of its short-term effects^[4]. These studies aim to identify the most effective dose and delivery method, such as oral or intravenous administration. They also confirm the dosing interval and safety profile seen so far^[1].

Phase 3: how is a medicine's benefit confirmed before approval?

Phase 3 trials are carried out only on medicines that have already passed Phase 1 and Phase 2. They test the medicine in much larger groups of ill patients, comparing it against an existing treatment or a placebo^[4]. The aim is to reconfirm the findings from Phase 2 in a larger population. Researchers also want to identify the best dosage regimen before the medicine is submitted for authorisation^[1].

How do control groups, randomisation and blinding protect trial results?

If you take part in a clinical trial, you are usually randomly assigned to either the treatment group or the control group. The treatment group receives the medicine being studied, while the control group receives an existing standard treatment or, if no proven standard treatment exists, a placebo. Researchers try to keep every other condition the same between the two groups. This way, any difference in outcome can be attributed to the treatment itself rather than to other factors^[4].

Who authorises a new medicine for use across the European Union?

In the European Union, a medicine must be authorised before it can be marketed and made available to patients. There are two main routes: a centralised procedure and a national procedure. Under the centralised procedure, a pharmaceutical company submits a single marketing-authorisation application to the European Medicines Agency (EMA). This single application allows the medicine to be marketed throughout the EU on the basis of one authorisation^[6].

EMA's Committee for Medicinal Products for Human Use (CHMP) carries out the scientific assessment of the application. It then issues a recommendation on whether the medicine should be authorised. EMA itself has no authority to grant marketing authorisation directly. The European Commission is the authorising body. It takes a legally binding decision based on EMA's recommendation. This decision is usually issued within 67 days of receiving that recommendation^[6].

Before a medicine is authorised, its risks are studied and weighed against its benefits. A medicine can only be authorised if the available data show that its benefits outweigh its risks. Whether a particular side effect is considered acceptable depends on the seriousness of the disease being treated. A serious side effect may be acceptable for a life-threatening illness such as cancer, but not for a simple painkiller. This balancing exercise is never a fixed formula. It is instead a judgement made case by case, informed by the severity of the disease, the availability of alternative treatments, and the strength of the evidence submitted^[7].

EMA also supports medicine development directly by offering scientific advice and protocol assistance to developers. This support sits alongside dedicated procedures for paediatric medicines, advanced-therapy medicines and orphan designation for rare diseases^[8].

What happens to a medicine's safety monitoring after it reaches the pharmacy?

Once a medicine is on the market, information about its known side effects and recommendations for safe use are made available to patients and healthcare professionals. Medicines are carefully and continuously monitored after authorisation. The goal is to detect any new safety issues that were not apparent during clinical trials^[7].

EMA works together with national competent authorities in each EU country to continuously monitor a wide range of data sources. This monitoring draws on scientific studies and reports from patients to identify when action is needed. This proactive monitoring allows authorities to respond when new risks emerge. The actions taken can range from adding a new warning for patients and healthcare professionals to restricting how a medicine is used, or in some cases suspending its use entirely^[7].

Some medicines also go through a Phase 4 trial once they are already on the market and available on prescription. This allows their safety, side effects and effectiveness to continue being studied in everyday use, although this is not required for every medicine^[4].

How can you find and join a clinical trial as a patient or volunteer?

You can ask your doctor or a patient organisation whether they know of a clinical trial for which you may be eligible. Alternatively, you can search dedicated registers and register your interest in taking part yourself. Charities focused on specific health conditions also list trials relevant to their communities. International registers such as the World Health Organization's International Clinical Trials Registry Platform give access to trials in countries around the world^[4].

• Taking part may benefit you directly, or it may help others with the same condition in the future, but there is also a chance the new treatment turns out to be no better, or worse, than the standard treatment^[4];
• Some trials offer payment, which varies depending on what is involved, while others only cover travel expenses^[4];
• Participation can be time-consuming, involving repeated screening and follow-up visits, and sometimes overnight stays^[4];
• There may be restrictions during the trial, for example being asked not to eat or drink alcohol for a period of time, and you may experience side effects that are not yet fully known^[4].

Both healthy people and people with a diagnosed medical condition can take part in clinical research. Participation is always completely voluntary, and you can leave the study at any time and for any reason^[3].

When should you talk to your doctor or pharmacist about a clinical trial or a new medicine?

Speak with your doctor before agreeing to join a clinical trial. This gives you time to weigh the possible benefits, the time commitment, and the unknown side effects specific to that particular study^[4]. If you are already taking a medicine that later reaches Phase 4 monitoring, or if you notice a side effect that seems new or worsening, report it to your doctor or pharmacist. It can then be assessed and, where relevant, passed on to the authorities monitoring that medicine's safety^[7]. Ask your care team about eligibility criteria, screening requirements, and what happens if you wish to withdraw from a study before it ends^[3].

Summary

A new medicine's route from the laboratory to the pharmacy passes through laboratory discovery, preclinical testing in cells and animals, and four phases of clinical trials in progressively larger groups of people. It ends with formal authorisation before it can be prescribed. Out of thousands of candidate compounds, only a small handful ever complete this journey. The whole process commonly takes over a decade. It draws on the combined work of laboratory scientists, clinical researchers and regulatory assessors at every stage^[1].

Even after a medicine reaches the pharmacy, its safety is not left to chance: EMA and national authorities across the EU continue to monitor real-world use, and patients themselves can play a part by reporting side effects to their doctor or pharmacist. If you are ever invited to take part in a clinical trial, remember that participation is voluntary and you will be told what is expected of you in advance. You can also withdraw at any point, just as EMA's own oversight of medicines continues long after a marketing authorisation has been granted^[8].

1. [1] Drug development: the journey of a medicine from lab to shelf (accessed 2 June 2026) — https://pharmaceutical-journal.com/article/feature/drug-development-the-journey-of-a-medicine-from-lab-to-shelf
2. [2] A guide to the development and manufacture of medicines (accessed 2 June 2026) — https://www.abpi.org.uk/publications/a-guide-to-the-development-and-manufacture-of-medicines/
3. [3] Clinical Research: What Is It? (accessed 2 June 2026) — https://www.hopkinsmedicine.org/research/understanding-clinical-trials/clinical-research-what-is-it
4. [4] Clinical trials (accessed 2 June 2026) — https://www.nhs.uk/tests-and-treatments/clinical-trials/
5. [5] https://www.cancerresearchuk.org/for-researchers/how-we-deliver-research/our-research-infrastructure/centre-for-drug-development
6. [6] Authorisation of medicines (accessed 2 June 2026) — https://www.ema.europa.eu/en/about-us/what-we-do/authorisation-medicines
7. [7] From laboratory to patients. How the safety of medicines is ensured in the European Union (accessed 2 June 2026) — https://www.ema.europa.eu/en/documents/other/laboratory-patients-how-safety-medicines-ensured-european-union_en.pdf
8. [8] What we do (accessed 2 June 2026) — https://www.ema.europa.eu/en/about-us/what-we-do