CCNE1 copy number is a biomarker for response to combination WEE1-ATR inhibition in ovarian and endometrial cancer models.

CCNE1-amplified ovarian cancers (OVCAs) and endometrial cancers (EMCAs) are associated with platinum resistance and poor survival, representing a clinically unmet need. We hypothesized that dysregulated cell-cycle progression promoted by CCNE1 overexpression would lead to increased sensitivity to low-dose WEE1 inhibition and ataxia telangiectasia and Rad3-related (ATR) inhibition (WEE1i-ATRi), thereby optimizing efficacy and tolerability. The addition of ATRi to WEE1i is required to block feedback activation of ATR signaling mediated by WEE1i. Low-dose WEE1i-ATRi synergistically decreases viability and colony formation and increases replication fork collapse and double-strand breaks (DSBs) in a CCNE1 copy number (CN)-dependent manner. Only upon CCNE1 induction does WEE1i perturb DNA synthesis at S-phase entry, and addition of ATRi increases DSBs during DNA synthesis. Inherent resistance to WEE1i is overcome with WEE1i-ATRi, with notable durable tumor regressions and improved survival in patient-derived xenograft (PDX) models in a CCNE1-level-dependent manner. These studies demonstrate that CCNE1 CN is a clinically tractable biomarker predicting responsiveness to low-dose WEE1i-ATRi for aggressive subsets of OVCAs/EMCAs.

Xu H ，George E ，Kinose Y ，Kim H ，Shah JB ，Peake JD ，Ferman B ，Medvedev S ，Murtha T ，Barger CJ ，Devins KM ，D'Andrea K ，Wubbenhorst B ，Schwartz LE ，Hwang WT ，Mills GB ，Nathanson KL ，Karpf AR ，Drapkin R ，Brown EJ ，Simpkins F ... -  《-》

WEE1 inhibitor and ataxia telangiectasia and RAD3-related inhibitor trigger stimulator of interferon gene-dependent immune response and enhance tumor treatment efficacy through programmed death-ligand 1 blockade.

Wu X ，Kang X ，Zhang X ，Xie W ，Su Y ，Liu X ，Guo L ，Guo E ，Li F ，Hu D ，Qin X ，Fu Y ，Peng W ，Jia J ，Wang C ... -  《-》

Identification of a Molecularly-Defined Subset of Breast and Ovarian Cancer Models that Respond to WEE1 or ATR Inhibition, Overcoming PARP Inhibitor Resistance.

PARP inhibitors (PARPi) induce synthetic lethality in homologous recombination repair (HRR)-deficient tumors and are used to treat breast, ovarian, pancreatic, and prostate cancers. Multiple PARPi resistance mechanisms exist, most resulting in restoration of HRR and protection of stalled replication forks. ATR inhibition was highlighted as a unique approach to reverse both aspects of resistance. Recently, however, a PARPi/WEE1 inhibitor (WEE1i) combination demonstrated enhanced antitumor activity associated with the induction of replication stress, suggesting another approach to tackling PARPi resistance. We analyzed breast and ovarian patient-derived xenoimplant models resistant to PARPi to quantify WEE1i and ATR inhibitor (ATRi) responses as single agents and in combination with PARPi. Biomarker analysis was conducted at the genetic and protein level. Metabolite analysis by mass spectrometry and nucleoside rescue experiments ex vivo were also conducted in patient-derived models. Although WEE1i response was linked to markers of replication stress, including STK11/RB1 and phospho-RPA, ATRi response associated with ATM mutation. When combined with olaparib, WEE1i could be differentiated from the ATRi/olaparib combination, providing distinct therapeutic strategies to overcome PARPi resistance by targeting the replication stress response. Mechanistically, WEE1i sensitivity was associated with shortage of the dNTP pool and a concomitant increase in replication stress. Targeting the replication stress response is a valid therapeutic option to overcome PARPi resistance including tumors without an underlying HRR deficiency. These preclinical insights are now being tested in several clinical trials where the PARPi is administered with either the WEE1i or the ATRi.

Serra V ，Wang AT ，Castroviejo-Bermejo M ，Polanska UM ，Palafox M ，Herencia-Ropero A ，Jones GN ，Lai Z ，Armenia J ，Michopoulos F ，Llop-Guevara A ，Brough R ，Gulati A ，Pettitt SJ ，Bulusu KC ，Nikkilä J ，Wilson Z ，Hughes A ，Wijnhoven PWG ，Ahmed A ，Bruna A ，Gris-Oliver A ，Guzman M ，Rodríguez O ，Grueso J ，Arribas J ，Cortés J ，Saura C ，Lau A ，Critchlow S ，Dougherty B ，Caldas C ，Mills GB ，Barrett JC ，Forment JV ，Cadogan E ，Lord CJ ，Cruz C ，Balmaña J ，O'Connor MJ ... -  《-》

Differential Activity of ATR and WEE1 Inhibitors in a Highly Sensitive Subpopulation of DLBCL Linked to Replication Stress.

DNA damage checkpoint kinases ATR and WEE1 are among key regulators of DNA damage response pathways protecting cells from replication stress, a hallmark of cancer that has potential to be exploited for therapeutic use. ATR and WEE1 inhibitors are in early clinical trials and success will require greater understanding of both their mechanism of action and biomarkers for patient selection. Here, we report selective antitumor activity of ATR and WEE1 inhibitors in a subset of non-germinal center B-cell (GCB) diffuse large B-cell lymphoma (DLBCL) cell lines, characterized by high MYC protein expression and CDKN2A/B deletion. Activity correlated with the induction of replication stress, indicated by increased origin firing and retardation of replication fork progression. However, ATR and WEE1 inhibitors caused different amounts of DNA damage and cell death in distinct phases of the cell cycle, underlying the increased potency observed with WEE1 inhibition. ATR inhibition caused DNA damage to manifest as 53BP1 nuclear bodies in daughter G1 cells leading to G1 arrest, whereas WEE1 inhibition caused DNA damage and arrest in S phase, leading to earlier onset apoptosis. In vivo xenograft DLBCL models confirmed differences in single-agent antitumor activity, but also showed potential for effective ATR inhibitor combinations. Importantly, insights into the different inhibitor mechanisms may guide differentiated clinical development strategies aimed at exploiting specific vulnerabilities of tumor cells while maximizing therapeutic index. Our data therefore highlight clinical development opportunities for both ATR and WEE1 inhibitors in non-GCB DLBCL subtypes that represent an area of unmet clinical need. SIGNIFICANCE: ATR and WEE1 inhibitors demonstrate effective antitumor activity in preclinical models of DLBCL associated with replication stress, but new mechanistic insights and biomarkers of response support a differentiated clinical development strategy.

Young LA ，O'Connor LO ，de Renty C ，Veldman-Jones MH ，Dorval T ，Wilson Z ，Jones DR ，Lawson D ，Odedra R ，Maya-Mendoza A ，Reimer C ，Bartek J ，Lau A ，O'Connor MJ ... -  《-》

Combining PARP with ATR inhibition overcomes PARP inhibitor and platinum resistance in ovarian cancer models.

Kim H ，Xu H ，George E ，Hallberg D ，Kumar S ，Jagannathan V ，Medvedev S ，Kinose Y ，Devins K ，Verma P ，Ly K ，Wang Y ，Greenberg RA ，Schwartz L ，Johnson N ，Scharpf RB ，Mills GB ，Zhang R ，Velculescu VE ，Brown EJ ，Simpkins F ... -  《Nature Communications》