5-Bromo-1H-pyrrolo[2,3-b]pyridine (aka 5-Bromo-7-azaindole) is a pharmaceutical intermediate that typically used in the preparation of ABT-199, as a potent and selective BCL-2 inhibitor, in the treatment of chronic lymphocytic leukemia (CLL). Recently it is also employed in the preparation of 7-Azaindole Scaffold Derivatives as PI3K Inhibitors.
ABT-199: A new hope for selective BCL-2 inhibition. 
ABT-199, a potent and selective BCL-2 inhibitor, achieves antitumor activity while sparing platelets. 
Discovery of novel 7-azaindoles as PDK1 inhibitors. 
Discovery of a Novel Series of 7-Azaindole Scaffold Derivatives as PI3K Inhibitors with Potent Activity. 
 M.S.Davids, et al, Cancer Cell, 2013, 23(2), pp 139-141.
 A.J.Soners, et al, Nat. Med., 2013, 19(2), pp 202-208.