Unique functions of CHK1 and WEE1 underlie synergistic anti-tumor activity upon pharmacologic inhibition

Abstract

BackgroundInhibition of kinases involved in the DNA damage response sensitizes cells to genotoxic agents by abrogating checkpoint-induced cell cycle arrest. CHK1 and WEE1 act in a pathway upstream of CDK1 to inhibit cell cycle progression in response to damaged DNA. Therapeutic targeting of either CHK1 or WEE1, in combination with chemotherapy, is under clinical evaluation. These studies examine the overlap and potential for synergy when CHK1 and WEE1 are inhibited in cancer cell models.MethodsSmall molecules MK-8776 and MK-1775 were used to selectively and potently inhibit CHK1 and WEE1, respectively.ResultsIn vitro, the combination of MK-8776 and MK-1775 induces up to 50-fold more DNA damage than either MK-8776 or MK-1775 alone at a fixed concentration. This requires aberrant cyclin-dependent kinase activity but does not appear to be dependent on p53 status alone. Furthermore, DNA damage takes place primarily in S-phase cells, implying disrupted DNA replication. When dosed together, the combination of MK-8776 and MK-1775 induced more intense and more durable DNA damage as well as anti-tumor efficacy than either MK-8776 or MK-1775 dosed alone. DNA damage induced by the combination was detected in up to 40% of cells in a treated xenograft tumor model.ConclusionsThese results highlight the roles of WEE1 and CHK1 in maintaining genomic integrity. Importantly, the strong synergy observed upon inhibition of both kinases suggests unique yet complimentary anti-tumor effects of WEE1 and CHK1 inhibition. This demonstration of DNA double strand breaks in the absence of a DNA damaging chemotherapeutic provides preclinical rationale for combining WEE1 and CHK1 inhibitors as a cancer treatment regimen.

Phase II Study of WEE1 Inhibitor AZD1775 Plus Carboplatin in Patients With TP53-Mutated Ovarian Cancer Refractory or Resistant to First-Line Therapy Within 3 Months

“…32 In conclusion, our study provides clinical evidence that AZD1775 enhances the antitumor efficacy of carboplatin in patients with TP53-mutated ovarian cancer resistant to first-line therapy and suggests that AZD1775 plus carboplatin may outperform first-line platinum-based chemotherapy in these patients. On the basis of these encouraging results, further development starting with a randomized phase II or III study is warranted in this particular patient group and in other p53-deficient tumors to substantiate the true value of AZD1775.…”

CHK1 and WEE1 inhibition combine synergistically to enhance therapeutic efficacy in acute myeloid leukemia ex vivo

“…[37][38][39][40] Davies et al performed a medium throughput screen to the Chk1 inhibitor AR458323 and identified WEE1 as their top hit in one lung cancer and two prostate cancer cell lines. 38 In a separate study by Carrassa et al, high throughput siRNA screening identified WEE1 kinase to be synthetically lethal with the small molecule Chk1 inhibitor PF-00477736 in ovarian cancer cell lines.…”

An Unbiased Oncology Compound Screen to Identify Novel Combination Strategies

“…Although broadly synergistic combinations may seem the most attractive, we suspect that many of these combinations may not be well tolerated in mice and human patients. Notably, the mTOR inhibitor/Wee1 inhibitor combination was well tolerated at the respective MTDs while the Chk1 inhibitor/Wee1 inhibitor was not (11,17). Context-dependent combinations, especially those that combine drugs targeting two different pathways, are less likely to have overlapping toxicities.…”

“…Of the 538 combinations tested, 287 ($50%) were synergistic in at least one cell line and 178 ($30%) were antagonistic in at least one cell line. We identified few broadly synergistic combinations including the Wee1 inhibitor combined with the Chk1 inhibitor (11) and PARP inhibitor combined with temozolimide (12, 13). Context-dependent synergistic drug combinations were also identified, including the mTOR inhibitor/AKT inhibitor combination and mTOR inhibitor/ERK inhibitor combination.…”