Drug discovery, testing and publication
Infection and response • Communicable diseases
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Key concepts
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Stages of drug discovery and development
Drug development begins with computer modelling to predict interactions and prioritise candidates. Laboratory testing follows, often using cultured cells and tissues to observe biological effects. Promising compounds enter preclinical animal studies to assess safety and dosing before any human exposure. Human testing proceeds in clinical trial phases to determine toxicity, efficacy and dose, after which regulators licence effective and safe medicines for manufacture and sale. The whole process is lengthy and costly and many candidates fail at each stage.
Preclinical testing: cells, tissues and animals
Cell and tissue tests allow direct observation of a compound's effect on target cells and help detect immediate toxic effects in vitro. These tests reveal mechanisms of action and identify damaging effects on particular tissues. Live-animal studies model whole-body responses, drug distribution and long-term toxicity when complex interactions are important. Animal data inform likely human doses and identify major safety concerns, but animal results may not always predict human responses and ethical limits apply.
Testing for toxicity, efficacy and dose
Toxicity testing determines whether a compound harms the body and identifies harmful dose ranges. Efficacy testing checks whether the drug produces the intended therapeutic effect. Dose-finding experiments establish the smallest effective dose and the maximum safe dose. Early human tests focus on toxicity and safe doses; later trials measure how well the drug treats the condition. All three aspects-toxicity, efficacy and dose-guide whether development continues and what licence applications require.
Clinical trials: volunteers, patients and trial design
Phase 1 trials use small numbers of healthy volunteers and start at low doses to check for toxicity and safety. Phase 2 trials test efficacy on small groups of patients with the condition and refine dosing. Phase 3 trials recruit large numbers of patients to confirm effectiveness and finalise optimal doses. Random allocation and control groups reduce bias. Double-blind trials hide treatment allocation from both patient and doctor and often use a placebo to remove psychological effects; this improves the reliability of results. Low initial doses and stepwise increases protect participants.
Publication and peer review
Trial results enter the scientific record only after peer review. Peer review means other qualified scientists examine the methods, data and conclusions to identify errors, bias or false claims. Peer review reduces the chance of publishing unreliable findings and allows the wider scientific community to judge validity before regulatory or clinical decisions. Publication after peer review supports transparency and replication.
Origins of some important drugs
Many medicines originate from natural sources. Penicillin originates from the Penicillium mould; Alexander Fleming observed that the fungus killed Staphylococcus bacteria and isolated penicillin in 1928. Aspirin originates from willow bark; the natural compound salicin, identified in the 18th century, led to aspirin manufacture in 1897. Digitalis originates from foxglove plants and provides compounds used to treat irregular heartbeat. Natural sources remain important starting points for drug discovery.
Key notes
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