**14. Evaluation of new drugs and drug approval process**

Toxicity testing is time consuming and expensive and may require two to five years to collect and analyze data before the drug can be considered ready for testing in humans.

Large numbers of animals are needed to obtain valid preclinical data.

Extrapolation of toxicity data from animals to humans may not be completely reliable.

The safety or efficacy of a drug must be thoroughly understood before the drug is ad‐ ministered to any group of individuals. Therefore regulations governing the develop‐ ment of new drugs have evolved to assure safety and efficacy of new medications. The clinical trials during drug development and post marketing experience form the scientific basis of patient response to a drug.

Once a drug is judged ready to be studied in humans, a notice of clinical investigational exemption for a new drug (IND) must be filled with the government body concerned with the regulation and registration of drugs. The IND includes manufacturing information, all data from animal studies, clinical plans and protocols and the names and credentials of physicians who will conduct the clinical trials.

#### **14.1. Phase I clinical trials**

The main goal in phase I is to determine whether test animals and humans show signifi‐ cant different responses to the drug and to establish limits of the safe clinical dosage range. The measurements carried out in phase I include, the rate of absorption, t1/2 and metabolism of the candidate drug compound. The effects of the drug as a function of dosage are established in a small number 25 – 50 of healthy volunteers. When the drug is expected to have significant toxicity, as often the case with cancer and AIDS therapy, volunteer patients with the disease are used instead of the healthy volunteers. The re‐ quirements of clinical trials include the following:

