Turetsky, AnnaKim, EunhaKohler, RainerMiller, MilesWeissleder, Ralph2014-05-062014Turetsky, Anna, Eunha Kim, Rainer H. Kohler, Miles A. Miller, and Ralph Weissleder. 2014. “Single cell imaging of Bruton's Tyrosine Kinase using an irreversible inhibitor.” Scientific Reports 4 (1): 4782. doi:10.1038/srep04782. http://dx.doi.org/10.1038/srep04782.2045-2322http://nrs.harvard.edu/urn-3:HUL.InstRepos:12152828A number of Bruton's tyrosine kinase (BTK) inhibitors are currently in development, yet it has been difficult to visualize BTK expression and pharmacological inhibition in vivo in real time. We synthesized a fluorescent, irreversible BTK binder based on the drug Ibrutinib and characterized its behavior in cells and in vivo. We show a 200 nM affinity of the imaging agent, high selectivity, and irreversible binding to its target following initial washout, resulting in surprisingly high target-to-background ratios. In vivo, the imaging agent rapidly distributed to BTK expressing tumor cells, but also to BTK-positive tumor-associated host cells.en-USJournal Article2014-05-0610.1038/srep04782