The randomized controlled trial (RCT) is the gold standard for assessing new therapeutic and preventative interventions by cmparing them wih a control group which receives the current standard intervention (or none if there isn't one). Allocating each individual participant to the new or standard intervention by a random process removes bias in the selection of treatment, so that differences in outcome are likely to be due to the intervention, not differences in the characteristics of the participants. 

New interventions including drugs can be more reliably evaluated in systematic reviews, which bring together the results from many different RCTs that have been carried out, addressing the same question. The gold standard for systematic review is meta analysis of individual patient data from all of the RCTs. This allows the exploration of effects within specific subgroups which individual trials cannot address and can provide more robust estimates of the risks and benefits of new therapeutic approaches.