STAT3 and neoplasm: However, before in vitro application, we ensured that the primary concerns associated with employing a new compound, namely target-selectivity and possible toxicity to non-tumor tissues, were not significant factors in our assays: YHO-1701 effectively inhibited the binding of phospho-Tyr peptide to the SH2 domain of STAT3 in a concentration-dependent manner with IC50 values of 2.5 μM for STAT3 and >30 μM for other adapter proteins containing SH2 domains, such as STAT1 and Grb2, thereby demonstrating high selectivity for STAT3 (Fig. 3b and Supplementary Fig. 5a).