In clinical trial, Phase 1 and 2 trials establish proof-of-concept, and phase 3 trials establish the efficacy and safety of the treatment in human population. Despite positive results in phase 1 and 2 trials, many times phase 3 trails fails. Phase 3 trials are povital trial and over phase 2 there is a large jump in time and resources to conduct a phase 3 trial, many potential treatments go unstudied.
That’s what the importance of the phase 2B trials.
Phase 2b clinical trial is to investigate the efficacy in a small-scale efficacy trial, before beginning the large scale phase 3 trail.