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).

The survivals of all six cell lines were decreased in a dose-dependent manner after THZ2 treatment. GES-1 cells were most insensitive to THZ2 with the highest IC50 values of 2.45 μM. The IC50 values of THZ2 in AGS, BGC-823, MGC-803, MKN-45 and SGC-7901 were 0.19 μM, 0.69 μM, 0.74 μM, 0.73 μM and 0.68 μM respectively, which were positively correlated with the protein expression of CDK7 in these cells[1].

Generated the xenograft tumor models by transplanting BGC-823 cells into nude mice. Compared with the control group, treatment with THZ2 significantly inhibited the growth of BGC-823 tumors by diminishing the volume and weight of tumors, but did not change the the weight of nude mice. The inhibition rate of tumor growth in THZ2 treatment group was 44.00%[1].

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].