The commercially available STAT3 inhibitor 5,15-diphenylporphyrin (5,15-DPP) does not directly interact with STAT3 core residues 127-722.

Here, we show using surface plasmon resonance spectroscopy that a common STAT3-SH2 inhibitor, 5,15-diphenylporphyrin (5, 15-DPP), does not bind STAT3 core amino acid residues 127 to 722 relative to another commercially available SH2 inhibitor, S3I-201. This finding should provide caution in data interpretation when using 5,15-DPP in in vitro and in vivo laboratory investigations.