Synthetic Lethal Strategy Identifies a Potent and Selective TTK and CLK1/2 Inhibitor for Treatment of Triple-Negative Breast Cancer with a Compromised G1–S Checkpoint

Abstract

Historically, phenotypic-based drug discovery has yielded a high percentage of novel drugs while uncovering new tumor biology. CC-671 was discovered using a phenotypic screen for compounds that preferentially induced apoptosis in triple-negative breast cancer cell lines while sparing luminal breast cancer cell lines. Detailed kinase profiling shows CC-671 potently and selectively inhibits two kinases-TTK and CLK2. Cellular mechanism of action studies demonstrate that CC-671 potently inhibits the phosphorylation of KNL1 and SRp75, direct TTK and CLK2 substrates, respectively. Furthermore, CC-671 causes mitotic acceleration and modification of pre-mRNA splicing leading to apoptosis, consistent with cellular TTK and CLK inhibition. Correlative analysis of genomic and potency data against a large panel of breast cancer cell lines identifies breast cancer cells with a dysfunctional G-S checkpoint as more sensitive to CC-671, suggesting synthetic lethality between G-S checkpoint and TTK/CLK2 inhibition. Furthermore, significant CC-671 efficacy was demonstrated in two cell line-derived and one patient tumor-derived xenograft models of triple-negative breast cancer (TNBC) following weekly dosing. These findings are the first to demonstrate the unique inhibitory combination activity of a dual TTK/CLK2 inhibitor that preferably kills TNBC cells and shows synthetic lethality with a compromised G-S checkpoint in breast cancer cell lines. On the basis of these data, CC-671 was moved forward for clinical development as a potent and selective TTK/CLK2 inhibitor in a subset of patients with TNBC. .

Cdc-Like Kinases (CLKs): Biology, Chemical Probes, and Therapeutic Potential

“…Some of the compounds exhibiting sufficient activity in the cell and in vivo have been pre-clinically profiled as anti-tumor agents [ 76 , 135 , 137 ]. Of note, the therapeutic potential of CLK inhibitors might be enhanced by simultaneous inhibition of additional targets [ 136 , 137 ].…”

“…In 2018, CC-671 ( Figure 24 ) was reported as CLK/TTK inhibitor [ 137 ]. Interestingly, this compound exhibits some selectivity for CLK2 (IC 50 = 6 nM) vs. CLK1 (IC 50 = 300 nM) and especially CLK3 (60% residual activity at 3 µM concentration), based on biochemical assay [ 137 ]. Unfortunately, the compound’s ability to inhibit CLK4 is unknown as well as its selectivity profile in the cell.…”

“…Although CC-671 does not fulfill the criteria for a quality probe, further profiling (and potentially structural modifications) may potentially lead to an interesting tool compound for specific inhibition of CLK2. In addition, CC-671 has been used in various cell-based and in vivo assays where it elicited growth inhibition and induction of apoptosis in various types of cancer cells [ 137 ]. The in vivo efficacy was shown in two cell line-derived and one patient tumor-derived xenograft models of triple-negative breast cancer.…”

Dual TTK/CLK2 inhibitor, CC‐671, selectively antagonizes ABCG2‐mediated multidrug resistance in lung cancer cells

“…The dual inhibitory mechanism represents a new class of cancer therapy, particularly in triple negative breast cancer patients. 33 In the course of searching MDR-reversing agents, we found that CC-671 can effectively antagonize ABCG2-mediated MDR. Our study indicates the significant reversal effect of CC-671 and therefore provides a potential combined treatment strategy to overcome MDR.…”

Upregulation of Thr/Tyr kinase Increases the Cancer Progression by Neurotensin and Dihydropyrimidinase-Like 3 in Lung Cancer

“…TTK has been considered to be dysregulated in various cancer cells because TTK dysregulation causes excess centrosomes resulting in aberrant mitotic spindles. Reduced in TTK level or activity in tumors can lead to a decrease of cell viability and division; thus, inhibition of TTK has been regard as an attractive target for anti-cancer drug development [6][7][8]. TTK has been also reported that upregulation of TTK increases lung cancer progression due to X-linked deubiquitinase USP9X dysfunction [9,10].…”