Clinical trials involve clinical studies of humans to validate biomedical interventions such as vaccines, drugs, medical devices, and supplements. Each trial is conducted to find new ways to prevent, diagnose, or treat specific diseases.
Clinical trials for hepatitis C are divided into four phases. In Phase I, the main aim of the trial is to determine if the drug is safe enough to proceed to studies with longer duration exposure and larger numbers of patients. Phase I trials involve a small study group of 20 to 80 people and are conducted for only a few days.
Drugs that pass Phase I with few side effects recorded proceed to Phase II, the objective of which is to determine the right dosage for patients, and assess the activity of the drug against the hepatitis C virus in infected individuals. Conducted in different locations and generally involving more than 100 people, the duration of Phase 2 clinical trials is typically 24 weeks, including 12 weeks of drug treatment, before final results are collated and analyzed.
Phase III trials are strictly controlled. They may be conducted in multiple countries, and researchers test the drug regimen's safety and effectiveness in a large number of patients.
Phase IV trials, also known as postmarketing trials, are typically performed on target groups previously excluded from participating in the earlier phases. Phase IV trials may include individuals with other infections, such as HIV, or in the case of hepatitis C, patients with very advanced liver disease or some other systemic illness.