Cell experiment:

To determine the effects of the test compounds (e.g., Opaganib (ABC294640)) on proliferation, cells are plated into 96-well microtiter plates and allowed to attach for 24 h. Varying concentrations of Opaganib are added to individual wells and the cells are incubated for an additional 72 h. At the end of this period, the number of viable cells is determined by use of the sulforhodamine-binding assay. The percentage of cells killed is calculated as the percentage decrease in sulforhodamine-binding compare with control cultures. Regression analyses of inhibition curves are performed by use of GraphPad Prism[1].

Animal experiment:

Rats[1] Sprague-Dawley male rats (7-8 weeks old) are orally dosed with 0, 100, or 250 mg of ABC294640oHCl/kg in 0.375% Polysorbate-80 in PBS daily for 7 days. The animals are observed daily for viability, signs of gross toxicity, and behavioral changes, and a battery of detailed observations are performed on study days 1 and 7. Blood is sampled from all animals on day 8 of the study for hematology, clinical biochemistry, and serology assessments, and the animals are sacrificed. Gross necropsies are performed on all study rats, and selected organs and tissues are evaluated in the control and high-dose level groups. Mice[3] Male C57BL/6 (8-9 weeks) mice are gavaged with 50 mg/kg of Opaganib (ABC294640), or an equivalent volume of vehicle (0.375% Tween 80 in phosphate buffered saline, pH 7.1) 1 h before surgery. Under ether anesthesia, ischemia to 70% of the total liver is induced for 1 h. After opening the vascular clamp, the non-ischemic liver lobes are removed, and mice are observed 7 days for survival. Sham operation included equivalent anesthesia and laparotomy without ischemia.

ABC294640 is a selective and competitive inhibitor of sphingosine kinase 2 (SK2) with IC50 value of 60μM [1].

ABC294640 is a competitive inhibitor of SK2. It shows IC50 value of about 60μM against recombinant human SK2. In the kinetic assay, ABC294640 competes with sphingosine and exerts a Ki value of 9.8μM. Because of its targeting of the sphingosine binding site of SK2, ABC294640 shows no inhibition activity against other 20 kinases. In MDA-MB-231 cells, ABC294640 prevents S1P production with IC50 value of 26μM. Moreover, ABC294640 has anti-proliferation and anti-migration efficacies in tumor cells. It suppresses cell proliferation of a variety of tumor cell lines such as 1025LU, A-498, Caco-2 and HT-29. The IC50 values are ranged from 6μM to 48μM. Furthermore, administration of ABC294640 inhibits tumor growth in the immunocompetent BALB/c mice bearing mammary adenocarcimona xenografts. Besides that, ABC294640 is also found to have greater anti-proliferation effects in ER-positive than ER-negative breast cancer cells. The effect of E2 signaling caused by ABC294640 is expected to be a therapeutic in endocrine-related diseases [1, 2].

References:
[1] French K J, Zhuang Y, Maines L W, et al. Pharmacology and antitumor activity of ABC294640, a selective inhibitor of sphingosine kinase-2. Journal of Pharmacology and Experimental Therapeutics, 2010, 333(1): 129-139.
[2] Antoon J W, White M D, Meacham W D, et al. Antiestrogenic effects of the novel sphingosine kinase-2 inhibitor ABC294640. Endocrinology, 2010, 151(11): 5124-5135.