PF-543

PF-543 is a potent, selective, reversible, and sphingosine-competitive inhibitor of SphK1 with an IC₅₀ value of 2nM and a Ki value of 3.6 nM^[1]. SphK1 is a kinase that phosphorylates sphingosine to sphingosine-1-phosphate (S1P), which promotes cell growth, survival, and migration, and regulates lymphocyte trafficking. The selectivity of PF-543 for SPHK 1 is over 100 times that of SPHK 2^[2]. PF-543 induces apoptosis, necrosis, and autophagy.

In vitro, PF-543 inhibits the formation of C17-S1P in 1483 cells, with an IC₅₀ of 1.0 nM^[1]; PF-543 inhibits SphK1 leading to a dose-dependent depletion of intracellular S1P levels, with an EC₅₀ of 8.4 nM and an accompanying increase in intracellular sphingosine levels in 1483 cells^[1]; PF-543 (10-1000 nM; 24h) treatment eliminates SK expression in PASM cells^[1]. Treatment with 200 nM PF-543 for 1h decreased endogenous S1P levels by tenfold in 1483 cells, with a corresponding increase in sphingosine levels^[2]. PF-543 (0.1-10 μM; 24 h) treatment of PASM cells induces caspase-3/7 activity^[3].

In vivo, PF-543 (1 mg/kg; intraperitoneal injection; every other day; for 3 weeks) reduces right ventricular hypertrophy in female C57BL/6 J mice, decreases the expression of p53, increases the expression of the antioxidant nuclear factor Nrf-2, but has no effect on vascular remodeling^[3]. When mice were initially treated with an intraperitoneal injection of 10 mg/kg or 30 mg/kg PF-543 for 24 h, the blood sample T_1/2 was 1.2 h, which could induce a decrease in SK1 expression in the pulmonary vasculature^[3].

References:

[1] Schnute M E et al. , Modulation of cellular S1P levels with a novel, potent and specific inhibitor of sphingosine kinase-1. Biochem J. 2012, 444(1): 79-88.

[2] Hamada M, et al. Induction of autophagy by sphingosine kinase 1 inhibitor PF-543 in head and neck squamous cell carcinoma cells. Cell Death Discov. 2017 Aug 14;3:17047.   

[3] MacRitchie N, et al. Effect of the sphingosine kinase 1 selective inhibitor, PF-543 on arterial and cardiac remodelling in a hypoxic model of pulmonary arterial hypertension. Cell Signal. 2016 Aug;28(8):946-55.