During the Phase I stage of a clinical trial, clinical trial companies investigate the effects of a drug on around 20 to 80 patients over a period of several months. These are patients who do not have any health conditions.
This phase monitors the effects of a drug and evaluates its safety as well as the safe dosage of the medication which can be taken and the best way in which the drug can be administered.
If the drug is deemed to be safe, it moves to Phase II of the clinical trial.
Goal of Phase II Trials
The goal of Phase II clinical trials is to estimate the activity of a new drug or treatment and assesses its toxicity and therapeutic efficacy. The outcome of these pilot studies determine whether the new drug is promising and a further large scale Phase III testing is warranted. The outcome is based on the observed response whether using the trial drug results in an improvement over existing drugs or treatments.
The number of patients in Phase II CRO trials varies between 20 and 50 and the trial is able to detect improvements of over 10%. Improvements of less than 5% can only be detected in much larger sample sizes.
In cancer therapeutics Phase II studies play a prominent role as new treatments arise from a combination of existing therapies or result from by varying the radiation dosage.
Objectives of Phase II Trials
Phase II trials have three main objectives
- Test whether the new drug or treatment will benefit the patient
- To screen the new drug for the response activity
- To extend knowledge about the toxicology and pharmacology of the treatment.
One of the important characteristics of Phase II trials is the use of rules for early stopping.
If upon testing sufficient evidence is obtained that the treatment has a positive effect, the treatment is considered to be promising and effective, resulting in the testing being terminated.
On the contrary, if the treatment does not result in an appreciable improvement in the patient‘s condition, the test is terminated and the treatment does not go on to Phase III.
How Phase II Trials Differ From Phase I Trials
While Phase I trials recruits healthy patient volunteers to determine maximum doses and what dose ranges should be administered, Phase II clinical trials are focused on therapeutic efficacy among a particular sample of patients in order to establish if the drug being trialed will benefit patients and if the drug merits consideration to be studied in a Phase III trial.
Phase II trials are generally randomized and controlled evaluating the efficacy and safety of a drug for a specific condition. The research involves the selection of participants using narrow criteria, allowing clinical trial companies to closely monitor the patient sample.
Although the earlier phases provide information about well-tolerated and safe doses of drug development, Phase II trials assess safety parameters for checking any adverse effects which could have been missed or may relate specifically to only a certain patient sample.
Phase II trials determine an appropriate treatment regimen and dose which can be tested in Phase III trials and dose response studies are carried out accordingly. Doses used in Phase II clinical trials are usually less than the highest does used in Phase I. The treatment is also administered on a larger patient sample in Phase 2 clinical trials.
Phase II clinical trials are sometimes subdivided in two subgroups. The trials in one subgroup focus on the dosage. The patients in this subgroup are given different doses of the drug to evaluate the dose-response relationship. The objective is to examine if there is an increase in response which correlates to an increase in increments of the dose. In addition to this, the optimal frequency for administering the dose is explored.
In the second subgroup, the trials are designed to specifically test the effectiveness of the drug in diagnosing, preventing and treating a disease.
Phase II clinical trials are being increasingly performed by clinical trial companies and being reported. They are essential to determining whether a new drug or procedure is worth being investigated in randomised and controlled Phase III studies.
Well-designed clinical studies, complete with reporting of patient eligibility, trial design, study endpoints as well as statistical analyses, the data from Phase II clinical trials can be reliable and applicable in those clinical situations where there is a lack of “better” evidence. Clinical trial companies must evaluate the merit of the clinical trial and its relevance to a particular clinical setting.