Ilorasertib (ABT-348) (ABT-348) is an ATP-competitive multitargeted kinase inhibitor, which inhibits Aurora A/Aurora B/Aurora C (IC50s: 120 nM/7 nM/1 nM). It also suppresses RET tyrosine kinase, PDGFRβ, and Flt1 (IC50s: 7 nM, 3 nM, and 32 nM).

VEGFR2:2 nM, VEGFR1:1 nM, Aurora C:1 nM, PDGFRα:11 nM, Aurora B:7 nM, PDGFRβ:13 nM, Aurora A:120 nM, FLT3:1 nM

In addition to targeting Aurora kinases, Ilorasertib is a potent inhibitor of the VEGFR and PDGFR kinase families and, to a lesser extent, the Src family of cytoplasmic tyrosine kinases. Ilorasertib induces a concentration-dependent increase in the extent and number of two NSCLC cell lines exhibiting polyploidy (EC50: 5, 10 nM). Ilorasertib shows antiproliferative activity against BCR-ABL expressing CML cells and cells expressing the Gleevec-resistant BCR-ABL T315I mutation (IC50: 47, 260 nM) [2].

Ilorasertib inhibits the VEGF response with a potency (ED50: 0.2 mg/kg, i.v.) in a uterine edema model. Ilorasertib (25 mg/kg, s.c.) leads to an inhibition of histone H3 phosphorylation in circulating tumor cells obtained from an engrafted leukemia model. Ilorasertib (20 mg/kg, p.o.) inhibits the growth of established tumors and causes regression of advanced tumors in human xenograft models [2]. Ilorasertib demonstrates significant antitumor efficacy in both solid and hematological xenograft models after intravenous, mini-pump or parenteral once-weekly dosing [3].

Noncycling primary HUVEC are used to assess the effect of Ilorasertib on nonproliferating cells. Cells (35,000/well) are seeded in growth medium in a 96-well tissue culture plate, and after 2 days, the medium is changed and the cells are treated with Ilorasertib. After an additional 3 days, cell viability is measured with Cell TiterGlo reagent [2].

For flank xenograft models, cells are suspended in PBS, mixed with Matrigel (phenol red-free) in a ratio of 1:4 (v/v), and inoculated into the flank of female SCID/beige mice (5 million cells per site). Inoculated mice are randomized into groups of 10, and treatment is initiated when mean tumor volume is approximately 0.4 cm^3 or 0.5 cm^3. Tumor growth in the flank is assessed by measuring tumor size with calipers and calculating volume using the formula (L × W2/2). Study groups are terminated before tumor volume reaches 3 cm^3. Inhibition of tumor growth is assessed at the time the vehicle-treated group is terminated by calculating the ratio of the mean volume of the test drug group to the mean volume of the untreated (control) group (T/C) and calculating the percentage of inhibition of control [(1 ? T/C) × 100]. The dosing formulation of test agents is prepared by stepwise addition, with mixing, of the following reagents: EtOH, Tween 80, polyethylene glycol 400, and 2% hydroxypropyl methylcellulose (2:5:20:73, v/v). The dosing volume is 10 mL/kg [2].