In cell‐free enzymatic assays, TPCA‐1 displays 22‐fold selectivity for IKK‐2 over IKK‐1 and a >550‐fold selectivity over other kinases, including MAP kinases and JNK kinases 32, though a recent study showed that in non–small cell lung cancer cell lines TPCA‐1 also inhibited STAT‐3 phosphorylation 34. Here, STAT3 is linked to small cell lung carcinoma.