Pifithrin-mu, 10 mg

STEMCELL Technologies supplies a small molecule designated Pifithrin-mu (PFTHμ; PFT-μ) that acts as an inhibitor of p53-mediated apoptosis by preventing p53 from binding to Bcl-xL and Bcl-2 at the mitochondrial surface, without affecting p53 transactivational activities. In vitro, the compound binds p53 with a Kd of 0.82 mM and Bcl-xL with a Kd of 0.80 mM, and it also interacts selectively with heat shock protein 70 (HSP70), disrupting the association of HSP70 with many of its co-chaperones and substrate proteins.

The chemical is 2-phenylethynesulfonamide (CAS 64984-31-2; formula C₈H₇NO₂S; molecular weight 181.2 g/mol), supplied as a crystalline solid at a purity of ≥ 98%. It is soluble in absolute ethanol and DMSO at concentrations up to 75 mM, with additional reported solubilities of approximately 0.1 mg/mL in a 1:10 EtOH:PBS (pH 7.2) solution and approximately 14 mg/mL in ethanol, DMSO, and DMF. The product is stable at –20°C as supplied and should be protected from prolonged light exposure. A 10 mM stock solution in DMSO can be prepared by resuspending 1 mg in 552 µL of fresh DMSO, with stock solutions ideally prepared fresh before use; for cell culture applications the final DMSO concentration should be kept below 0.1% to avoid potential cell toxicity.

Published research applications include combining the compound with the ROCK inhibitor Y-27632 to improve cell recovery after cryopreservation and using it to inhibit DNA damage–induced apoptosis in human embryonic stem cells. The product is classified as hazardous: it is harmful if swallowed, causes skin and serious eye irritation, and may cause respiratory irritation, and is supplied for research use only.