Effective combination therapies in preclinical endocrine resistant breast cancer models harboring ER mutations.
ABSTRACT: Although endocrine therapy is successfully used to treat patients with estrogen receptor (ER) positive breast cancer, a substantial proportion of this population will relapse. Several mechanisms of acquired resistance have been described including activation of the mTOR pathway, increased activity of CDK4 and activating mutations in ER. Using a patient derived xenograft model harboring a common activating ER ligand binding domain mutation (D538G), we evaluated several combinatorial strategies using the selective estrogen receptor degrader (SERD) fulvestrant in combination with chromatin modifying agents, and CDK4/6 and mTOR inhibitors. In this model, fulvestrant binds WT and MT ER, reduces ER protein levels, and downregulated ER target gene expression. Addition of JQ1 or vorinostat to fulvestrant resulted in tumor regression (41% and 22% regression, respectively) though no efficacy was seen when either agent was given alone. Interestingly, although the CDK4/6 inhibitor palbociclib and mTOR inhibitor everolimus were efficacious as monotherapies, long-term delayed tumor growth was only observed when co-administered with fulvestrant. This observation was consistent with a greater inhibition of compensatory signaling when palbociclib and everolimus were co-dosed with fulvestrant. The addition of fulvestrant to JQ1, vorinostat, everolimus and palbociclib also significantly reduced lung metastatic burden as compared to monotherapy. The combination potential of fulvestrant with palbociclib or everolimus were confirmed in an MCF7 CRISPR model harboring the Y537S ER activating mutation. Taken together, these data suggest that fulvestrant may have an important role in the treatment of ER positive breast cancer with acquired ER mutations.
Project description:PURPOSE:While FGFR1 amplification has been described in breast cancer, the optimal treatment approach for FGFR1-amplified (FGFR1+) metastatic breast cancer (MBC) remains undefined.Experimental Design: We evaluated clinical response to endocrine and targeted therapies in a cohort of patients with hormone receptor-positive (HR+)/HER2- MBC and validated the functional role of FGFR1-amplification in mediating response/resistance to hormone therapy in vitro. RESULTS:In the clinical cohort (N = 110), we identified that patients with FGFR1+ tumors were more likely to have progesterone receptor (PR)-negative disease (47% vs. 20%; P = 0.005), coexisting TP53 mutations (41% vs. 21%; P = 0.05), and exhibited shorter time to progression with endocrine therapy alone and in combination with CDK4/6 inhibitor, but not with a mTOR inhibitor (everolimus), adjusting for key prognostic variables in multivariate analysis. Furthermore, mTOR-based therapy resulted in a sustained radiological and molecular response in an index case of FGFR1+ HR+/HER2- MBC. In preclinical models, estrogen receptor-positive (ER+)/FGFR1-amplified CAMA1 human breast cancer cells were only partially sensitive to fulvestrant, palbociclib, and alpelisib, but highly sensitive to everolimus. In addition, transduction of an FGFR1 expression vector into ER+ T47D cells induced resistance to fulvestrant that could be overcome by added TORC1 inhibition, but not PI3K or CDK4/6 inhibition. CONCLUSIONS:Collectively, these findings suggest that while FGFR1 amplification confers broad resistance to ER, PI3K, and CDK4/6 inhibitors, mTOR inhibitors might have a unique therapeutic role in the treatment of patients with ER+/FGFR1+ MBC.
Project description:BACKGROUND:Cyclin-dependent kinase 4/6?(CDK4/6) inhibitors (palbociclib and abemaciclib) and mammalian target of rapamycin (mTOR) inhibitors (everolimus) are effective agents for restoring endocrine sensitivity in patients with advanced breast cancer progression on prior aromatase inhibitors. We conducted a network meta-analysis to compare these treatments in terms of progression-free survival (PFS), objective response rate (ORR), and clinical benefit rate (CBR). METHODS:The PubMed and Embase databases were searched for relevant publications between January 2000 and June 2018. Treatments were ranked based on a network meta-analysis. Ranking was determined by P-score. A random-effect model was used when heterogeneity was detected; otherwise, a fixed-effect model was used. RESULTS:Six trials comprising 4063 patients formed the comparison network. Compared with everolimus plus exemestane, the combinations of palbociclib or abemaciclib with fulvestrant showed similar efficacies in PFS and no differences in ORR. For the CBR, palbociclib demonstrated improvement, while abemaciclib did not. Incidences of severe adverse events did not significantly differ. A total of 29%, 15.9%, and 4% of patients discontinued everolimus, abemaciclib, and palbociclib, respectively, due to toxicity. CONCLUSION:These results suggest similar efficacies between CDK4/6 inhibition and mTOR blockade; however, CDK4/6 inhibitors were associated with favorable toxicity profiles.
Project description:Using an ORF kinome screen in MCF-7 cells treated with the CDK4/6 inhibitor ribociclib plus fulvestrant, we identified FGFR1 as a mechanism of drug resistance. FGFR1-amplified/ER+ breast cancer cells and MCF-7 cells transduced with FGFR1 were resistant to fulvestrant ± ribociclib or palbociclib. This resistance was abrogated by treatment with the FGFR tyrosine kinase inhibitor (TKI) lucitanib. Addition of the FGFR TKI erdafitinib to palbociclib/fulvestrant induced complete responses of FGFR1-amplified/ER+ patient-derived-xenografts. Next generation sequencing of circulating tumor DNA (ctDNA) in 34 patients after progression on CDK4/6 inhibitors identified FGFR1/2 amplification or activating mutations in 14/34 (41%) post-progression specimens. Finally, ctDNA from patients enrolled in MONALEESA-2, the registration trial of ribociclib, showed that patients with FGFR1 amplification exhibited a shorter progression-free survival compared to patients with wild type FGFR1. Thus, we propose breast cancers with FGFR pathway alterations should be considered for trials using combinations of ER, CDK4/6 and FGFR antagonists.
Project description:We aimed to explore what kind of endocrine treatments are optimal for hormone receptor-positive and human epidermal growth factor receptor 2-negative locally advanced or metastatic breast cancer in some specific clinical situations. We searched randomized controlled trials in Embase, Medline, the Cochrane library, and PubMed from inception to April 1, 2020 and performed a network meta-analysis based on a Bayesian fixed-effects model. Progression-free survival (PFS) with hazard ratios and corresponding 95% confidence interval was defined as the primary endpoint, while overall survival (OS), objective response rate (ORR), clinical benefit rate and serious adverse events were used as secondary endpoints. A total of 35 studies involving 12,285 patients and 24 treatment options were included. In general, most co-treatment options prolonged PFS compared to single-agent therapy, of which aromatase inhibitor (AI) plus everolimus and fulvestrant plus palbociclib were probably the most effective agents, and the latter had the best safety record. However, despite the superior efficacy of fulvestrant plus capecitabine for PFS and OS, palpable toxic effects have been demonstrated for this treatment, so its application must be scrupulously considered. The results of subgroup analysis indicated that fulvestrant combined with palbociclib improved prognosis for phosphatidylinositol 3-kinase (PI3K)-mutated patients, PI3K-unmutated patients, patients with endocrine therapy resistance, and visceral metastatic patients, while no obvious improvement was detected in OS. Moreover, the efficacy of fulvestrant plus cyclin-dependent kinase 4/6 (CDK4/6) inhibitors was slightly better than that of AI plus CDK4/6 inhibitors, while AI plus everolimus was more efficacious than fulvestrant combined with everolimus in terms of PFS, OS, and ORR. In conclusion, our results provide moderate evidence that fulvestrant plus palbociclib and AI plus everolimus were the most effective treatments, while the efficacy and safety of fulvestrant plus palbociclib was obviously superior in some specific clinical situations.
Project description:BACKGROUND:Endocrine therapy constitutes a central modality in the treatment of oestrogen receptor (ER)-positive advanced breast cancer. PURPOSE:To evaluate the evidence for endocrine treatment in postmenopausal patients with advanced breast cancer focusing on the aromatase inhibitors, letrozole, anastrozole, exemestane and fulvestrant. METHODS:A review was carried out using PubMed. Randomised phase II and III trials reporting on ?100 patients were included. RESULTS:35 trials met the inclusion criteria. If not used in the adjuvant setting, a non-steroid aromatase inhibitor was the optimal first-line option. In general, the efficacy of the different aromatase inhibitors and fulvestrant was similar in tamoxifen-refractory patients. A randomised phase II trial of palbociclib plus letrozole versus letrozole alone showed significantly increased progression-free survival (PFS) when compared with endocrine therapy alone in the first-line setting (20.2 vs 10.2?months). Furthermore, the addition of everolimus to exemestane in the Breast Cancer Trials of OraL EveROlimus-2 (BOLERO-2) study resulted in an extension of median PFS by 4.5?months after recurrence/progression on a non-steroid aromatase inhibitor. However, overall survival was not significantly increased. CONCLUSION:Conventional treatment with an aromatase inhibitor or fulvestrant may be an adequate treatment option for most patients with hormone receptor-positive advanced breast cancer. Mammalian target of rapamycin (mTOR) inhibition and cyclin-dependent kinase 4/6 (CDK4/6) inhibition might represent substantial advances for selected patients in some specific settings. However, there is an urgent need for prospective biomarker-driven trials to identify patients for whom these treatments are cost-effective.
Project description:PURPOSE:The combination of targeting the CDK4/6 and estrogen receptor (ER) signaling pathways with palbociclib and fulvestrant is a proven therapeutic strategy for the treatment of ER-positive breast cancer. However, the poor physicochemical properties of fulvestrant require monthly intramuscular injections to patients, which limit the pharmacokinetic and pharmacodynamic activity of the compound. Therefore, an orally available compound that more rapidly reaches steady state may lead to a better clinical response in patients. Here, we report the identification of G1T48, a novel orally bioavailable, non-steroidal small molecule antagonist of ER. METHODS:The pharmacological effects and the antineoplastic mechanism of action of G1T48 on tumors was evaluated using human breast cancer cells (in vitro) and xenograft efficacy models (in vivo). RESULTS:G1T48 is a potent and efficacious inhibitor of estrogen-mediated transcription and proliferation in ER-positive breast cancer cells, similar to the pure antiestrogen fulvestrant. In addition, G1T48 can effectively suppress ER activity in multiple models of endocrine therapy resistance including those harboring ER mutations and growth factor activation. In vivo, G1T48 has robust antitumor activity in a model of estrogen-dependent breast cancer (MCF7) and significantly inhibited the growth of tamoxifen-resistant (TamR), long-term estrogen-deprived (LTED) and patient-derived xenograft tumors with an increased response being observed with the combination of G1T48 and the CDK4/6 inhibitor lerociclib. CONCLUSIONS:These data show that G1T48 has the potential to be an efficacious oral antineoplastic agent in ER-positive breast cancer.
Project description:While ER has multiple biological effects, ER-cyclin D1-CDK4/6-RB is a critical pathway for the action of estrogen on the cell cycle, especially for breast cancers that rely on estrogen for growth. The latest and most efficient CDK4/6 inhibitors target the phosphorylation of retinoblastoma (RB) tumor suppressor gene; thus, altering levels of many cell cycle molecules. Estrogen receptor (ER)+/HER2- breast cancers have shown great progression free survival when CDK4/6 inhibitors are combined with endocrine therapies. Here we report the mechanism of antiestrogen (fulvestrant) combination with CDK4/6 inhibitors is due to synergism in the suppression of ER-mediated cell cycle progression. Furthermore, we performed single cell analysis of cells from an estrogen dependent/hormone receptor-positive patient derived xenograft (PDX) tumor model treated with palbociclib. These single cells expressed various levels of ER and RB which are involved in cell cycle regulation; and the response to palbociclib treatment relies not only on the ER-cyclin D1-CDK4/6-RB pathway but it is also dependent on elevated levels of ER and/or RB. Our preclinical studies show that palbociclib response is dependent on cells with ER, which is directly involved in cell cycle progression in hormone receptor positive (HR+) breast cancer.
Project description:<h4>Background</h4>There are no established molecular biomarkers for patients with breast cancer receiving combination endocrine and CDK4/6 inhibitor (CDK4/6i). We aimed to determine whether genomic markers in circulating tumor DNA (ctDNA) can identify patients at higher risk of early progression on fulvestrant therapy with or without palbociclib, a CDK4/6i.<h4>Methods</h4>PALOMA-3 was a phase III, multicenter, double-blind randomized controlled trial of palbociclib plus fulvestrant (n?=?347) vs placebo plus fulvestrant (n?=?174) in patients with endocrine-pretreated estrogen receptor-positive (ER+) breast cancer. Pretreatment plasma samples from 459 patients were analyzed for mutations in 17 genes, copy number in 14 genes, and circulating tumor fraction. Progression-free survival (PFS) was compared in patients with circulating tumor fraction above or below a prespecified cutoff of 10% and with or without a specific genomic alteration. All statistical tests were 2-sided.<h4>Results</h4>Patients with high ctDNA fraction had worse PFS on both palbociclib plus fulvestrant (hazard ratio [HR] = 1.62, 95% confidence interval [CI] = 1.17 to 2.24; P = .004) and placebo plus fulvestrant (HR = 1.77, 95% CI = 1.21 to 2.59; P = .004). In multivariable analysis, high-circulating tumor fraction was associated with worse PFS (HR = 1.20 per 10% increase in tumor fraction, 95% CI = 1.09 to 1.32; P < .001), as was TP53 mutation (HR = 1.84, 95% CI = 1.27 to 2.65; P = .001) and FGFR1 amplification (HR = 2.91, 95% CI = 1.61 to 5.25; P < .001). No interaction with treatment randomization was observed.<h4>Conclusions</h4>Pretreatment ctDNA identified a group of high-risk patients with poor clinical outcome despite the addition of CDK4/6 inhibition. These patients might benefit from inclusion in future trials of escalating treatment, with therapies that may be active in these genomic contexts.
Project description:Breast cancer (BC) is the most common malignancy in women worldwide, with approximately two-thirds having hormone receptor-positive (HR+) tumors. New endocrine therapy (ET) strategies include combining ET agents as well as adding inhibitors targeting growth factors, angiogenesis, the mechanistic target of rapamycin, phosphoinositide 3-kinase (PI3K), or cyclin-dependent kinase 4/6 to ET. Level 1 evidence supports use of fulvestrant plus anastrozole or palbociclib plus letrozole as first-line therapy for HR+/HER- advanced BC with special consideration for the former in ET-naïve patients, as well as everolimus plus exemestane or palbociclib plus fulvestrant as second-line therapy with special consideration in select first-line patients. Although the safety profiles of these combinations are generally predictable and manageable, both everolimus and palbociclib are associated with an increased risk of potentially serious or early-onset toxicities requiring individualized a priori adverse event risk stratification, earlier and more rigorous agent-specific monitoring, and patient education. Although each of these combinations improves progression-free survival, none with the exception of anastrazole plus fulvestrant have demonstrated improved overall survival. PI3K catalytic-? mutations assessed from circulating tumor DNA represent the first potentially viable serum biomarker for the selection of ET combinations, and new data demonstrate the feasibility of this minimally invasive technique as an alternative to traditional tissue analysis. Therapeutic ratios of select ET combinations support their use in first- and second-line settings, but optimal sequencing has yet to be determined.2017;22:12-24 IMPLICATIONS FOR PRACTICE: Emerging data show that new endocrine therapy (ET) combinations can improve progression-free and overall survival outcomes in patients with hormone receptor-positive, HER2-negative (HR+/HER-) advanced breast cancer. Level 1 evidence supports consideration of dual ET regimens, particularly in ET-naïve patients, or palbociclib plus letrozole as first-line therapy, as well as the addition of mTOR or CDK4/6 inhibitors to established ET in the second-line setting and in select first-line patients. Some combinations are associated with increased risk of class-specific toxicities that will require individualized risk stratification, earlier and more rigorous agent-specific monitoring, and patient education. Recent data on a noninvasive biomarker assay that predicts response to a phosphoinositide 3-kinase inhibitor demonstrates the feasibility of this minimally invasive technique as an alternative to traditional tissue analysis.