Pharmacology · MU Sofia

3. Drug development- stages and phases.

Covers the multi-step route a new drug takes from target identification and lead compound selection through in vitro and in vivo work, preclinical safety testing and the IND application. It then walks through Phases I to III of clinical trials with their participant numbers and durations, the NDA and regulatory review, and Phase IV post-marketing surveillance. Includes recap questions at the end.

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Topic 3 of 93 in the MU Sofia syllabus for Pharmacology (Dental Medicine, Year 3). The free AceMed note covers it in 1 section, about 699 words (5 min of reading), with 10 flashcards.

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  1. Drug development- stages and phases.

Drug development- stages and phases.

Drug development is a complex, multi-step process that ensures new drugs are safe, effective, and suitable for human use. It consists of preclinical research, clinical trials, regulatory approval, and post-marketing surveillance.

Stages of Drug Development

1. Discovery and Preclinical Research

This is the initial stage where potential drug candidates are identified and tested before clinical trials.

  • Target Identification: Biological targets (proteins, enzymes, or genes) associated with diseases are identified.
  • Lead Compound Identification: Scientists search for molecules (lead compounds) that can interact with the target.
  • Optimization: The selected compounds are modified to improve efficacy, safety, and selectivity.
  • In Vitro Studies: Drug candidates are tested in cell cultures to assess biological activity.
  • In Vivo Studies: Animal studies are conducted to evaluate pharmacokinetics (ADME – Absorption, Distribution, Metabolism, Excretion) and pharmacodynamics (drug effects on the body).

If a drug shows positive results in preclinical research, it moves to preclinical testing and development.

2. Preclinical Testing/Development

Before testing in humans, the drug undergoes extensive safety and toxicity studies.

  • Pharmacokinetic Testing: Determines how the drug is absorbed, distributed, metabolized, and excreted.
  • Safety Pharmacology: Assesses potential adverse effects on the heart, lungs, and central nervous system.
  • Toxicokinetic Studies: Measures drug toxicity levels at different doses.
  • Carcinogenicity Studies: Evaluates whether the drug causes cancer over long-term exposure.
  • Reproductive Toxicity Testing: Assesses the drug’s impact on fertility and fetal development.
  • Bioanalytical Testing: Measures drug concentration in blood, tissues, and organs.

If the drug passes preclinical safety standards, the company submits an Investigational New Drug (IND) application to regulatory authorities (e.g., FDA) to begin clinical trials in humans.

3. Phases of Clinical Trials

Clinical trials involve testing the drug in humans to evaluate its safety, efficacy, and optimal dosage.

1. Phase I Clinical Trials

  • Objective: Assess safety, tolerability, pharmacokinetics, and pharmacodynamics of the drug in humans.
  • Participants: 20-100 healthy volunteers (or patients in some cases).
  • Duration: Several months.
  • Outcome:
  • Determines safe dosage ranges.
  • Identifies common side effects.
  • Helps in understanding how the drug is processed in the body.

If the drug is safe, it moves to Phase II.

2. Phase II Clinical Trials

  • Objective: Evaluate the drug's efficacy while continuing to monitor safety.
  • Participants: 100-300 patients with the disease or condition being studied.
  • Duration: Several months to 2 years.
  • Outcome:
  • Provides preliminary data on how effective the drug is.
  • Helps determine the optimal dosage for treatment.
  • Further assesses short-term side effects.

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