We investigate, under three general adaptive scenarios, the operating characteristics of adaptive patient enrichment study designs. The adaptive enrichment approaches permit assessment of treatment effect that may be applicable to specific nested patient (sub)sets due to heterogeneous patient characteristics and/or differential response to treatment, e.g., a responsive patient subset versus a lack of beneficial patient subset, in all patient (sub)sets studied. We show that regardless of whether the treatment effect eventually assessed is applicable to the originally studied patient population or only to the nested patient subsets, it is possible to devise an adaptive enrichment approach that statistically outperforms one-size-fits-all fixed design approach and the fixed design with a pre-specified multiple test procedure. The adaptive designs, when applicable, are along the line of efficiency consideration in a drug development program. The utility of patient subpopulation enrichment will be highlighted using typical case examples.