Clinical trial phase that investigates whether the drug works and the safety on people who are suffering from the disease

• A. Phase II
• B. Phase III
• C. Phase IV
• D. Phase I

Answer: (A)

Testing whether a drug actually works in patients who have the disease, while continuing to monitor safety, happens in the phase that follows initial safety checks and dose finding. In this phase, researchers enroll people who have the condition to see if the drug produces the desired effect and to collect more safety data in the target population. This helps establish that the treatment has true therapeutic benefit and acceptable risk before larger, more definitive studies. After this step, larger randomized trials compare the new treatment to standard care to confirm effectiveness, and later studies continue to monitor safety after approval. So, this description fits the phase focused on preliminary efficacy in the disease population, with ongoing safety assessment.