THZ2 (CDK7-IN-1), an analog of THZ1, is a potent and selective CDK7 inhibitor(IC50:13.9 nM),with the potential to treat Triple-negative breast cancer (TNBC).

CDK2:222 nM, CDK7:13.9 nM, CDK5:134 nM, CDK9:194 nM, CDK8:6830 nM, CDK1:96.9 nM

Cells were firstly seeded into a 96-well plate at a density of 3000 cells per well, and incubated with THZ2 in three parallel wells for 72 h. Then MTT was added to each well at a final concentration of 0.5 mg/ml. After incubation for 4 h, formazan crystals were dissolved in 100 μl of DMSO, and absorbance at 570 nm was measured by plate reader. The concentrations required to inhibit growth by 50% (IC50) were calculated from survival curves using the Bliss method[1].

Balb/c nude mice feed on sterilized food and water. Six female nude mice with 5 weeks old were used for two groups. Each mouse was injected subcutaneously with BGC-823 cells (3 × 10^6 in 100 μl of medium) under the shoulder. When the subcutaneous tumors were approximately 0.3 × 0.3 cm^2 (two perpendicular diameters) in size, mice were randomized into two groups, and were injected intraperitoneally with vehicle alone (0.9% saline) and THZ2 (10 mg/kg) once/day at first 16 days and twice/day at last 6 days. The body weights of mice and the two perpendicular diameters (A and B) of tumors were recorded. The tumor volume (V) was calculated according to the formula: V = (π/6) × [(A+B)/2]^3. The mice were anaesthetized after experiment, and tumor tissue was excised from the mice and weight. The rate of inhibition (IR) was calculated according to the formula: IR = [1 - (Mean tumor weight of experimental group/Mean tumor weight of control group)] × 100%[1].