Goetz, Matthew P.

Abstract Triple-negative breast cancer (TNBC) is characterized by elevated locoregional recurrence risk despite aggressive local therapies. New tumor-specific radiosensitizers are needed. We hypothesized that the ATR inhibitor, VX-970 (now known as M6620), would preferentially radiosensitize TNBC. Noncancerous breast epithelial and TNBC cell lines were investigated in clonogenic survival, cell cycle, and DNA damage signaling and repair assays. In addition, patient-derived xenograft (PDX) models generated prospectively as part of a neoadjuvant chemotherapy study from either baseline tumor biopsies or surgical specimens with chemoresistant residual disease were assessed for sensitivity to fractionated radiotherapy, VX-970, or the combination. To explore potential response biomarkers, exome sequencing was assessed for germline and/or somatic alterations in homologous recombination (HR) genes and other alterations associated with ATR inhibitor sensitivity. VX-970 preferentially inhibited ATR-Chk1-CDC25a signaling, abrogated the radiotherapy-induced G2–M checkpoint, delayed resolution of DNA double-strand breaks, and reduced colony formation after radiotherapy in TNBC cells relative to normal-like breast epithelial cells. In vivo, VX-970 did not exhibit significant single-agent activity at the dose administered even in the context of genomic alterations predictive of ATR inhibitor responsiveness, but significantly sensitized TNBC PDXs to radiotherapy. Exome sequencing and functional testing demonstrated that combination therapy was effective in both HR-proficient and -deficient models. PDXs established from patients with chemoresistant TNBC were also highly radiosensitized. In conclusion, VX-970 is a tumor-specific radiosensitizer for TNBC. Patients with residual TNBC after neoadjuvant chemotherapy, a subset at particularly high risk of relapse, may be ideally suited for this treatment intensification strategy. Mol Cancer Ther; 17(11); 2462–72. ©2018 AACR.

Abstract Background: A recent exploratory subgroup analysis pooling data from over 1000 patients (pts) in MONARCH 2 (final analysis) and MONARCH 3 (interim analysis) demonstrated that pts with clinical characteristics that predict for worse outcome (e.g. liver metastases, progesterone receptor [PgR]-negative status, high-grade tumors) received the largest benefit from the addition of abemaciclib to endocrine therapy (ET). There is also interest in determining the extent to which abemaciclib improves progression-free survival (PFS) in pts with favorable prognostic factors (e.g. bone-only disease, long treatment-free interval [TFI]). Here we present an update of the subgroup analyses of the MONARCH 3 study using data from the preplanned final PFS analysis. Methods: Enrollment criteria and study designs were previously described (Sledge et al. J Clin Oncol. 2017; Goetz et al. J Clin Oncol. 2017). An exploratory pooled analysis was conducted using data from MONARCH 2 (NCT02107703) and the MONARCH 3 (NCT02246621) preplanned final PFS analysis to identify significant prognostic factors regardless of therapy received. Using the updated MONARCH 3 data, PFS and objective response rate (ORR) (in pts with measurable disease) were examined within the prognostic subgroups that had been previously identified as being statistically significant. Additionally, subpopulation treatment effect pattern plot (STEPP) methodology was used to evaluate the association between TFI following adjuvant ET and outcomes of NSAI alone or with abemaciclib. Results: Assessment of clinical factors from MONARCH 2 and MONARCH 3 (final PFS data) confirmed that the following factors remained significantly prognostic regardless of treatment received: bone-only disease, liver metastases, tumor grade, PgR status, and ECOG performance status. In MONARCH 3, prognosis was poor in pts with liver metastases, PgR-negative tumors, and high-grade tumors. While all subpopulations benefited from the addition of abemaciclib to ET regardless of prognosis, pts with these three poor prognostic factors received substantial benefit from abemaciclib, with PFS hazard ratios (HR) ranging from 0.4 to 0.5 and with differential improvement in ORR typically >30%. Furthermore, STEPP analysis of TFI (on the MONARCH 3 pts who had received adjuvant ET) demonstrated that pts who had a shorter TFI had a worse prognosis and received relatively greater benefit from abemaciclib plus NSAI than did pts with a longer TFI. Patients with bone-only disease or a long TFI also received benefit from abemaciclib, but to a relatively lesser extent (HR ranging from approximately 0.6 to 0.8). Conclusions: This exploratory analysis of the preplanned final PFS data from MONARCH 3 confirms previous findings that pts with poor prognostic factors may receive relatively greater benefit from the addition of abemaciclib to ET. Citation Format: Joyce O'Shaughnessy, Matthew P. Goetz, George W. Sledge, Miguel Martin, Yong Lin, Tammy Forrester, Ian C. Smith, Angelo Di Leo, Stephen Johnston. The benefit of abemaciclib in prognostic subgroups: An update to the pooled analysis of MONARCH 2 and 3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT099.

Abstract Background: Abemaciclib is an orally administered, selective CDK4 & 6 inhibitor dosed on a continuous schedule. In patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC), abemaciclib demonstrated clinical activity as monotherapy in MONARCH 1 and efficacy with a generally tolerable safety profile in combination with fulvestrant in MONARCH 2. At the MONARCH 3 (NCT02246621) interim analysis, abemaciclib plus a nonsteroidal aromatase inhibitor (NSAI) significantly improved progression-free survival (PFS) (hazard ratio [HR], 0.543; 95% confidence interval [CI], 0.409, 0.723; p=.000021) and objective response rate (ORR) (measurable disease: abemaciclib arm, 59.2%; placebo arm, 43.8%; p=.004) with a generally tolerable safety profile as initial treatment for HR+, HER2- ABC. Here we present the MONARCH 3 results from the preplanned final PFS analysis. Methods: MONARCH 3 is a double-blind, Phase 3 study of abemaciclib/placebo (150 mg, twice daily continuous schedule) + NSAI (1 mg anastrozole or 2.5 mg letrozole, daily) in postmenopausal women with HR+, HER2- ABC who have had no prior systemic therapy for advanced disease. Endocrine therapy (ET) naïve pts or pts with disease relapse >12 months after (neo)adjuvant ET were randomized 2:1 and stratified by metastatic site (visceral, bone-only, or other) and prior ET (aromatase inhibitor, no ET, or other). The primary objective was investigator-assessed PFS. Additional objectives included ORR, clinical benefit rate (CBR), duration of response (DoR), overall survival (OS), and safety and tolerability. The study was powered to 80% at 1-sided α=.025 assuming a HR of 0.67 in favor of abemaciclib + NSAI, with the final analysis at 240 PFS events. Results: 493 pts were randomized to abemaciclib + NSAI (n=328) or placebo + NSAI (n=165). At the final PFS analysis, 246 PFS events had occurred. Abemaciclib + NSAI significantly extended PFS (HR, 0.540; 95% CI, 0.418, 0.698; p=.000002; median: abemaciclib arm, 28.18 vs placebo arm, 14.76 months). PFS was improved across all subgroups. For pts with measurable disease, the ORR was 61.0% in the abemaciclib arm and 45.5% in the placebo arm (p=.003), and the CBR was 79.0% in the abemaciclib arm and 69.7% in the placebo arm (p=.037). The median DoR was 27.39 months in the abemaciclib arm compared to 17.46 months in the placebo arm. OS was immature at the time of analysis. Adverse events were consistent with previous reports. Conclusions: Abemaciclib + NSAI demonstrated a generally tolerable safety profile and was an effective initial treatment for pts with HR+, HER2- ABC, significantly improving PFS and ORR. Citation Format: Matthew P. Goetz, Miguel Martin, Angelo Di Leo, Seock-Ah Im, Ahmad Awada, Tammy Forrester, Martin Frenzel, Joanne Cox, Susana Barriga, Masakazu Toi, Hiroji Iwata, Stephen Johnston. MONARCH 3: Abemaciclib as initial therapy for patients with HR+, HER2- advanced breast cancer - Results from the preplanned final PFS analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT040.

Abstract Purpose: TNBC represents an aggressive subtype characterized by earlier relapse and worse survival compared to non-TNBC. Patients with residual TNBC after neoadjuvant chemotherapy (NAC) have a high risk of locoregional recurrence despite aggressive subsequent local therapies, including RT. Thus, new radiosensitizers that address chemoresistant TNBC (i.e residual disease after NAC) are needed. ATR plays a key role in the cellular response to replication stress and DNA damage. TNBC is characterized by G1 checkpoint loss, homologous recombination deficiency (HRD), and other features which increase dependence on ATR pathway signaling. We hypothesized that VX-970, a selective inhibitor of ATR, would effectively radiosensitize TNBC. Methods: Cell lines representing varying subtypes of TNBC (MDA-MB-231, HCC1806, and BT-549) and the normal breast epithelial cell line MCF10a were investigated in clonogenic survival, cell cycle, and DNA damage signaling and repair assays. In addition, Mayo Clinic (MC)TNBC1 and MCTNBC2, patient derived xenograft models (PDXs) generated prospectively from baseline and chemoresistant residual disease surgical specimens after NAC, respectively, of unique patients in the Breast Cancer Genome Guided Therapy Study were analyzed. Tumors were injected into hind-legs of athymic nude mice and animals were randomized to: 1) Vehicle 2) RT 3) VX-970 4) RT + VX-970. RT was delivered in 5 daily fractions of 2 Gy. VX-970 was administered daily 1 hour prior to RT at a dose of 60 mg/kg. Exome sequencing was assessed for germ-line and/or somatic alterations in HR genes and an ex-vivo RAD51 foci formation assay was applied to confirm the functional status of HR in each PDX model. Results: In vitro, VX-970 preferentially inhibited ATR-Chk1-CDC25a signaling, abrogated the RT-induced G2/M checkpoint, delayed resolution of γH2AX and 53BP1 foci and reduced colony formation after RT in MDA-MB-231, HCC1806, and BT-549 relative to MCF10a. In vivo, VX-970 did not exhibit single agent activity at the dose administered but markedly sensitized both MCTNBC1 and MCTNBC2 to RT, suggesting that VX-970 could overcome chemoresistant TNBC biology. For MCTNBC1 and MCTNBC2, the median time to tumor tripling was 26 vs 49 days (p=0.002) and 25 vs 43 days (p=0.006) for the RT and RT + VX-970 groups, respectively. Ex-vivo RAD51 foci formation was robust in MCTNBC1, a PDX without HR gene alterations. In contrast, there was no RT-induced RAD51 foci formation in MCTNBC2, suggesting a BRCA1 mutation in the corresponding human tumor resulted in loss of HR function in that model. Conclusion: VX-970 + RT effectively radiosensitized TNBC PDXs established from both pre-treatment biopsy specimens and chemoresistant residual tumor samples and in both HR deficient and HR proficient settings. ATR inhibition should be investigated in the clinic in combination with RT for patients with residual TNBC after NAC. Citation Format: Robert W. Mutter, Mohamed M. Kahila, Xinyi Tu, Qin Zhou, Jia Yu, Krishna R. Kalari, Liewei Wang, Judy C. Boughey, Matthew P. Goetz, Jann N. Sarkaria, Zhenkun Lou. ATR inhibition is a promising radiosensitizing strategy for chemotherapy-resistant triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 840.

Metastatic breast cancer continues to be a life-threatening diagnosis that impacts hundreds of thousands of patients around the world. Targeted therapies are usually associated with less toxicity compared with cytotoxic chemotherapies and often induce response or durable disease control in estrogen receptor (ER) and/or HER2+ breast cancers. Drugs that target CDK 4/6 either alone or in combination with endocrine therapy have demonstrated substantial improvements in progression-free survival (PFS) compared with endocrine monotherapy. Most recently, PARP inhibitors have shown longer PFS compared with physician’s choice of chemotherapy in BRCA-associated cancers, leading to the first U.S. Food and Drug Administration (FDA) approval of a targeted therapy with the potential to benefit a subgroup of patients with triple-negative breast cancer (TNBC). Finally, newer drug delivery strategies using antibody drug conjugates have also allowed a “targeted approach” to deliver moderate to extremely potent cytotoxins directly to sites of metastatic disease, with less toxicity.

LBA1 Background: In hormone receptor (HR)-positive, HER2-negative, axillary node (AN)-negative breast cancer, the 21-gene expression assay (Oncotype DX Recurrence Score [RS]) is prognostic for distant recurrence, prognostic for low recurrence with endocrine therapy alone if low (0-10), and predictive of chemotherapy benefit if high (26 or higher). We performed a prospective, randomized trial of endocrine therapy (ET) versus chemoendocrine therapy (CET) in women with a mid-range RS of 11-25. Methods: Eligibility criteria included women 18-75 years of age with HR-positive, HER2-negative, axillary node (AN)-negative breast cancer and tumors 1.1-5.0 cm in size (or 0.6-1.0 cm and int/high grade) and agreed to have chemotherapy assigned or randomized based on the RS. Women with a mid-range RS (11-25) were randomized to receive ET or CET. The primary endpoint was invasive disease-free survival (iDFS), and the trial was designed to show non-inferiority for ET alone by not rejecting equality (hazard ratio [HR] margin up to 1.322 for omission of chemotherapy, 1-sided type I error rate 10%, type II error rate 5%). The target sample size was adjusted to compensate for non-adherence to randomized treatment, and the protocol-specified final analysis was triggered after 835 iDFS events. Results: Of the 10,253 eligible women enrolled between 4/7/06-10/6/10, 6711 (65.5%) had a RS of 11-25 and adequate information. There were 836 iDFS events at final analysis with a median followup of 90 months. ET was non-inferior to CET for iDFS (HR 1.08, 95% confidence intervals [CI] 0.94, 1.24, p=0.26) in the intention-to-treat (ITT) population. ET was also non-inferior for distant recurrence-free interval (DRFI; HR 1.03, p=0.80), recurrence-free interval (RFI; HR 1.12, p=0.28), and overall survival (OS; HR 0.97, p=0.80). Nine year rates were similar for iDFS (83.3% vs. 84.3%), DRFI (94.5% vs. 95.0%), RFI (92.2% vs. 92.9%), and OS (93.9% vs. 93.8%). Recurrence accounted for 338 (41.6%) the first iDFS event, of which 199 (23.8%) were distant recurrences. Treatment interaction tests were significant for age (iDFS p=0.03; RFI p= 0.02), but not menopause, tumor size, grade, or RS (continuous or RS 11-15, 16-20, 21-25). Conclusions: In women with HR-positive, HER2-negative, AN-negative breast cancer and a RS of 11-25, adjuvant ET was not inferior to CET in the ITT analysis. (Funded by NCI, BCRF, and Komen Foundation.) Clinical trial information: NCT00310180.

Abstract Purpose: Although high glucocorticoid receptor (GR) expression in early-stage estrogen receptor (ER)-negative breast cancer is associated with shortened relapse-free survival (RFS), how associated GR transcriptional activity contributes to aggressive breast cancer behavior is not well understood. Using potent GR antagonists and primary tumor gene expression data, we sought to identify a tumor-relevant gene signature based on GR activity that would be more predictive than GR expression alone. Experimental Design: Global gene expression and GR ChIP-sequencing were performed to identify GR-regulated genes inhibited by two chemically distinct GR antagonists, mifepristone and CORT108297. Differentially expressed genes from MDA-MB-231 cells were cross-evaluated with significantly expressed genes in GR-high versus GR-low ER-negative primary breast cancers. The resulting subset of GR-targeted genes was analyzed in two independent ER-negative breast cancer cohorts to derive and then validate the GR activity signature (GRsig). Results: Gene expression pathway analysis of glucocorticoid-regulated genes (inhibited by GR antagonism) revealed cell survival and invasion functions. GR ChIP-seq analysis demonstrated that GR antagonists decreased GR chromatin association for a subset of genes. A GRsig that comprised n = 74 GR activation-associated genes (also reversed by GR antagonists) was derived from an adjuvant chemotherapy-treated Discovery cohort and found to predict probability of relapse in a separate Validation cohort (HR = 1.9; P = 0.012). Conclusions: The GRsig discovered herein identifies high-risk ER-negative/GR-positive breast cancers most likely to relapse despite administration of adjuvant chemotherapy. Because GR antagonism can reverse expression of these genes, we propose that addition of a GR antagonist to chemotherapy may improve outcome for these high-risk patients. Clin Cancer Res; 24(14); 3433–46. ©2018 AACR.