(-)-JQ1 is the inactive stereoisomer of the potent, cell-permeable, small molecule bromodomain inhibitor (+)-JQ1 that competitively binds to acetyl-lysine recognition motifs. (+)-JQ1 competitively binds to the bromodomain displacing the BRD4 fusion oncoprotein from chromatin, which induces squamous differentiation and specific anti-proliferative effect in BRD4-dependent cell lines and patient-derived xenograft models. However, study results have shown that (-)-JQ1 fails to significantly interact with any bromodomain tested and exhibits inhibition against BRD4(1) with and IC₅₀ of 10,000 nM.