Clinical Trials : Animal and Human Study

Animal Study [Pre-Clinical Trial]

• Animals such as mice, rats, dogs, and rabbits are used in animal research. However, smaller animals like rats, rabbits, and guinea pigs are preferred.
• The major aim of the animal study is to find out the toxicity of the drug, since not all diseases occur in animals. Under toxicity, we check the following:
  • Acute toxicity.
  • Subacute toxicity.
  • Chronic toxicity.
  • Teratogenic effect.
  • Carcinogenic effect.
  • Mutagenic effect.
• The second major aspect of the animal study is to check the efficacy of the drug.
• Sometimes, tissue culture or organic cultures are used to check the efficacy and toxicity. This is done to avoid killing animals for the study.

The Human Study [Clinical Trial]

• This is the third aspect of new drug development.
• The first step in the human study is to file an investigational new drug (IND) application with the Central Drug Safety Control Organization (CDSCO).
• The head of CDSCO is called the Drug Controller General of India (DCGI).
• The DCGI will check whether the pre-clinical trials are conducted correctly and will approve the human study only after the animal trials are satisfactory.
• Once the DCGI approves the human study or the clinical trial, then we must proceed with the Phase I, Phase II, and Phase III trials, respectively.
• After the completion of the Phase III trials, we need to apply for a new drug application (NDA) to CDSCO to obtain a marketing license. Once granted, then the drug can be made available on the market.
• After obtaining the marketing license, the Phase IV clinical trial (post-marketing surveillance) is conducted.

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Phases of Clinical Trials

Various phases of clinical trials must be passed to ensure that the drug produced by the pharmaceutical industry is safe for consumption by the general population. These phases have to be remembered for the theoretical MBBS examinations as well as the competitive examinations like NEET-PG and FMGE.

Types of phases:

• Phase zero of the clinical trial 
  • Phase zero is a testing that is done on Healthy human volunteers.
  • It has Up to 10 participants in the trial.
  • The following is the main purpose of phase zero:
    • Micro dosing: 1/100 of a dose because high doses may be fateful
• Phase one of the clinical trial
  • Phase one is also tested on Healthy human volunteers. 
  • The phase one clinical trial usually extends from months to years (10-100)
  • The following is the main purpose of phase one:
    • Safety 
    • Nontoxicity of drugs 
    • Maximum tolerated of a drug.
    • Adverse effects of a drug
• Phase two of the clinical trial
  • Phase two is tested on actual patients.
  • There are about 50-500 participants in phase two of the clinical trials.
  • The trial lasts for around  1-2 years. 
  • The main purposes of Phase Two are:
    • To check for the Effectiveness of the drug
    • To check the Efficacy of the drug
    • Maximum drug failure occurs in Phase 2. It is very efficient if we catch the mistake early on.
• Phase four of the clinical trials
  • Phase four clinical trials are also tested on Patients
  • Phase four clinical trial study is unending till the drug is removed from circulation. 
  • It is the Longest phase of a clinical trial, and it continues for at least 10-25 years.
  • The main purpose of this phase is:
    • Monitoring the Long-term and rare side effects of drugs.
    • Phase four helps in the Post-marketing surveillance of the drug.

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Summary

• The first step in the new drug development is to find out the source of the drug.
• The next step is the animal study. The main aim of the animal study is to check for toxicity rather than efficacy since most of the human diseases do not occur in all animals.
• Following the successful completion of the animal study, an IND is submitted to CDSCO.
• After the IND is filed, the Phase I trial is commenced, which is also called human safety pharmacology. Here, the main goal is to check the safety of the drug.
• The Phase II trial will be conducted in one or two centers to assess drug’s efficacy.
• The next step is the Phase III trial. This is done to confirm the efficacy of the drug.
• The last step is the Phase IV trial. This is conducted to check for rare adverse events, the long-term safety of the drug, drug interactions, and the drug's effect on a special population.

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