One of the features of clinical trials is that they experiment with random individuals of a target group. Clinical trials are planned forecast studies which monitor the individuals evolution over time. The treatment provided normally tends to differ from usual ones, either because it is not authorised or because it is used under different conditions as the ones approved. Therefore they may not provide any benefit to the individual.
Clinical trials are complex process with a very specific target. Its sponsor needs to be conscious of the viability of the project and whether future outcomes may be applicable or not.
Clinical trials success will very much depend on how well it is planned and how potential issues are being managed.