How New Drugs Are Tested and Approved

🔬 How New Drugs Are Tested and Approved

Developing a new antibiotic is a long and tightly regulated process. Before any drug reaches patients, it must pass through a series of staged tests that progressively involve more complex living systems. This staged approach exists because safety failures caught early save lives — and money. The full process typically takes 10–15 years and costs over £1 billion per drug.

Stage 1: Pre-clinical Testing (Before Any Humans Are Involved)

Pre-clinical testing happens entirely outside human subjects. Researchers test the potential drug on:

• Cells and tissues (in vitro): The drug is applied to living cells or tissue samples in a laboratory dish. This checks basic toxicity — does the drug kill human cells? Does it interfere with normal cell function? This step is relatively cheap and fast.
• Animals (in vivo): The drug is tested in living organisms (typically mice or rats). This reveals how the drug behaves in a whole living system — how it is absorbed, broken down, and excreted by the body. It also identifies side effects that only appear in living organisms and helps establish a safe dosage range.

A drug must pass all pre-clinical tests before it can proceed to any human trials. Many candidate drugs fail here and never move forward.

Stage 2: Clinical Trials — Three Phases

Clinical trials test the drug in human volunteers and patients. They are divided into three phases, each progressively larger:

Phase	Who is involved	Main purpose
Phase 1	Small group of healthy volunteers (20–100 people)	Safety — identify side effects, find the maximum safe dose the human body can tolerate
Phase 2	Larger group of patients who have the disease (100–300 people)	Efficacy — does the drug actually work against the disease? What is the optimum dose?
Phase 3	Thousands of patients across multiple sites	Large-scale comparison — compare the new drug against existing treatments or a placebo; build statistical confidence that the effect is real

Double-blind Trial Design

In Phase 3 trials, it is critical to remove bias from the results. This is achieved using a double-blind trial:

• Half the patients receive the real drug; the other half receive a placebo — a dummy treatment that looks and tastes identical but contains no active ingredient.
• Neither the patient nor the doctor administering the treatment knows who has received the real drug or the placebo. This is what makes the trial "double-blind" — both sides are unaware.
• Without this, patients who know they are receiving a real drug may report improvement just because they expect to feel better (the placebo effect). Doctors who know which patients received the real drug may unconsciously interpret their symptoms more favourably.
• Once all data is collected, the blind is broken and results are analysed.

Peer Review and Regulatory Approval

After clinical trials, results are published and subjected to peer review — independent scientists check the methodology and conclusions. Only once a drug has passed peer-reviewed clinical trials and satisfied regulatory bodies (such as the MHRA in the UK) can it be prescribed to patients.

Why New Antibiotics Are So Hard to Develop

• Time and cost: 10–15 years and over £1 billion per drug
• Regulatory requirements: Every phase must demonstrate safety and efficacy
• Limited commercial return: Antibiotics are taken for short courses (unlike drugs for chronic conditions), reducing profit incentive for pharmaceutical companies
• Rapid resistance: Bacteria may develop resistance to a new antibiotic before it even reaches market

Alternative Approaches Being Researched

• Bacteriophages: Viruses that specifically infect and kill bacteria
• Antimicrobial peptides: Natural defence molecules found in living organisms
• Combination therapies: Using two drugs together to reduce the chance bacteria can develop resistance to both simultaneously