Abemaciclib In Combination Research Articles

Abemaciclib in Combination with Endocrine Therapy for Adjuvant Treatment of Hormone Receptor-Positive, HER2-Negative, Node-Positive Early Breast Cancer: An Evidence Review Group Perspective of a NICE Single Technology Appraisal.

The National Institute for Health and Care Excellence (NICE) invited the manufacturer (Eli Lilly) of abemaciclib (Verzenios) to submit evidence for the clinical and cost effectiveness of this drug in combination with endocrine therapy (ET) for the treatment of adult patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, node-positive early breast cancer at high risk of recurrence, as part of the Institute's Single Technology Appraisal (STA) process. Kleijnen Systematic Reviews Ltd, in combination with Newcastle University, was commissioned to act as the independent Evidence Review Group (ERG). This paper summarised the Company Submission (CS), presents the ERG's critical review of the clinical and cost-effectiveness evidence in the CS, highlights the key methodological considerations, and describes the development of the NICE guidance by the Appraisal Committee. The ERG produced a critical review of the evidence for the clinical and cost-effectiveness evidence in the CS and also independently searched for relevant evidence and modified the manufacturer decision analytic model to examine the impact of altering some of the key assumptions. A systematic literature review identified the MonarchE trial, an ongoing, open-label, randomised, double blind trial involving 5637 people comparing abemaciclib in combination with ET versus ET alone. The trial included two cohorts that used different inclusion criteria to define high risk of recurrence. The ERG considered Cohort 1 as an adequate representation of this population and the AC concluded that Cohort 1 was generalisable to National Health Service clinical practice. Trial results showed improvements in invasive disease-free survival for the abemaciclib arm, which was considered an appropriate surrogate outcome. The ERG believed that the modelling structure presented in the de novo economic model by the company was appropriate but highlighted several areas of uncertainty that had the potential to have a significant impact on the resulting incremental cost-effectiveness ratio (ICER). Areas of uncertainty included the extrapolation of long-term survival curves, the duration of treatment effect and treatment waning, and the proportion of patients who receive other CDK4/6 treatments for metastatic disease after receiving abemaciclib. ICER estimates were £9164 per quality-adjusted life-year gained for the company's base-case and £17,810 for the ERG's base-case. NICE recommended abemaciclib with ET as an option for the adjuvant treatment of HR-positive, HER2-negative, node-positive early breast cancer at high risk of recurrence.

Abstract OT2-01-09: ABEMACARE: Abemaciclib in Combination with Endocrine Therapy as First Line Therapy in Metastatic Breast Cancer Patients with Symptomatic Visceral Metastases or High Tumor Burden – A prospective multicenter observational study

Abstract OT2-01-09: ABEMACARE: Abemaciclib in Combination with Endocrine Therapy as First Line Therapy in Metastatic Breast Cancer Patients with Symptomatic Visceral Metastases or High Tumor Burden – A prospective multicenter observational study

Abemaciclib: A Review in Early Breast Cancer with a High Risk of Recurrence.

Abemaciclib [Verzenio® (USA) or Verzenios® (EU)] is a cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor approved in combination with adjuvant endocrine therapy for patients with hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-), node-positive, early breast cancer with a high risk of recurrence. In a phase III trial, abemaciclib plus endocrine therapy reduced the risk of recurrence of breast cancer compared with endocrine therapy alone, including in patients who had previously received neoadjuvant chemotherapy, in patients with high- and low-scoring Ki-67 tumours, and in both premenopausal and postmenopausal patients. The tolerability profile of abemaciclib plus endocrine therapy was acceptable and manageable, with diarrhoea, infections and neutropenia being the most common adverse events. Thus, abemaciclib in combination with standard endocrine therapy is a valuable additional treatment option for patients with HR+, HER2-, node-positive early breast cancer with a high risk of recurrence.

CYCLONE 3: A phase 3, randomized, double-blind, placebo-controlled study of abemaciclib in combination with abiraterone plus prednisone in men with high-risk, metastatic, hormone-sensitive prostate cancer (mHSPC).

TPS289 Background: Landmark trials have established a survival benefit for novel hormonal agents (NHA) added to androgen deprivation therapy (ADT) for mHSPC. Yet, there is a significant medical need to expand therapeutic options, especially for pts with high-risk mHSPC who experience poorer outcomes. Abemaciclib is an oral selective inhibitor of cyclin-dependent kinase 4 and 6 (CDK4 & 6) dosed on a continuous schedule, approved for the treatment of node-positive high-risk early-stage and advanced or metastatic HR+, HER2- breast cancer. Analogous to the estrogen receptor signaling pathway in breast cancer, there is evidence that the androgen receptor axis activates CDK4 & 6 to sustain prostate cancer cell proliferation, and upregulation of cyclin D1 is a potential mechanism of resistance to NHA therapy. In preclinical models, abemaciclib induces cell cycle arrest and inhibition of prostate tumor growth. Methods: CYCLONE 3 (NCT05288166) is a global, randomized, double-blind, placebo-controlled study evaluating the addition of abemaciclib to abiraterone+prednisone (AP) in pts with high-risk mHSPC. Approximately 900 pts with high-risk mHSPC defined by ≥4 bone metastasis and/or visceral disease will be randomised in a 1:1 ratio to the AP + abemaciclib or AP + placebo arm. Up to 3 months of ADT prior to randomization is permitted; prior D for mHSPC will be excluded per planned protocol amendment. Pts who have not undergone orchiectomy will continue ADT. Stratification factors are de novo mHSPC and visceral metastases. Primary endpoint is investigator-assessed radiographic progression-free survival (rPFS). Key secondary endpoints include rPFS assessed by blinded independent central review, castration-resistant prostate cancer-free survival, overall survival, time to pain progression, safety and pharmacokinetics. Enrollment is open at approximately 270 sites across 25 countries. Clinical trial information: NCT05288166 .

The BRD4 inhibitor JQ1 augments the antitumor efficacy of abemaciclib in preclinical models of gastric carcinoma

BackgroundAdvanced gastric cancer (GC) is a lethal malignancy, harboring recurrent alterations in cell cycle pathway, especially the CDKN2A-CDK4/CDK6/CCND1 axis. However, monotherapy of CDK4/6 inhibitors has shown limited antitumor effects for GC, and combination treatments were urgently needed for CDK4/6 inhibitors.MethodsHere, we performed a comprehensive analysis, including drug screening, pan-cancer genomic dependency analysis, and epigenetic sequencing to identify the candidate combination with CDK4/6 inhibitors. Mechanisms were investigated by bulk RNA-sequencing and experimental validation was conducted on diverse in vitro or in vivo preclinical GC models.ResultsWe found that the BRD4 inhibitor JQ1 augments the antitumor efficacy of the CDK4/6 inhibitor abemaciclib (ABE). Diverse in vitro and in vivo preclinical GC models are examined and synergistic benefits from the combination therapy are obtained consistently. Mechanistically, the combination of ABE and JQ1 enhances the cell cycle arrest of GC cells and induces unique characteristics of cellular senescence through the induction of DNA damage, which is revealed by transcriptomic profiling and further validated by substantial in vitro and in vivo GC models.ConclusionThis study thus proposes a candidate combination therapy of ABE and JQ1 to improve the therapeutic efficacy and worth further investigation in clinical trials for GC.

CYCLONE 3: A Phase 3, randomized, double-blind, placebo-controlled study of abemaciclib in combination with abiraterone plus prednisone in men with high-risk metastatic hormone-sensitive prostate cancer (mHSPC)

CYCLONE 3: A Phase 3, randomized, double-blind, placebo-controlled study of abemaciclib in combination with abiraterone plus prednisone in men with high-risk metastatic hormone-sensitive prostate cancer (mHSPC)

Novel combination treatment of CDK 4/6 inhibitors with PARP inhibitors in triple negative breast cancer cells.

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors provide promising results for treating hormone receptor-positive breast cancer. However, the efficacy of CDK4/6 inhibitors remains uncertain in triple negative breast cancer (TNBC) patients with particularly carrying RB-deficient tumors. Poly-(ADP-ribose) polymerase (PARP) inhibitors offer a therapeutic strategy for the treatment of BRCA-mutated TNBC patients. However, the acquired drug resistance, changes in the cell cycle regulation, and DNA damage repair have demonstrated the necessity for developing new combination strategies. This preclinical study assessed a combinatory treatment of the CDK4/6 inhibitor abemaciclib with PARP inhibitors talazoparib (TAL) in HCC1937 BRCA-mutated RB-deficient TNBC cells and TAL-resistant HCC1937-R cells through WST-1 analysis, annexin V, cell cycle, acridine orange/propidium iodide staining, RT-PCR, and apoptosis array. Our findings revealed that abemaciclib and TAL combination synergistically suppressed the growth of TNBC cells and overcame TAL resistance through G0/G1 arrest and the activity of both intrinsic and extrinsic apoptotic pathways. These preliminary results suggest that the combination of abemaciclib and TAL could expand the use of these inhibitors in BRCA mutated and RB deficient TNBC patients and potentially overcomes PARP inhibitors resistance.

Targeting chromosome 12q amplification in relapsed glioblastoma: the use of computational biological modeling to identify effective therapy—a case report

Relapsed glioblastoma (GBM) is often an imminently fatal condition with limited therapeutic options. Computation biological modeling, i.e., biosimulation, of comprehensive genomic information affords the opportunity to create a disease avatar that can be interrogated in silico with various drug combinations to identify the most effective therapies. We report the outcome of a GBM patient with chromosome 12q amplification who achieved substantial disease remission from a novel therapy using this approach. Following next generation sequencing (NGS) was performed on the tumor specimen. Mutation and copy number changes were input into a computational biologic model to create an avatar of disease behavior and the malignant phenotype. In silico responses to various drug combinations were biosimulated in the disease network. Efficacy scores representing the computational effect of treatment for each strategy were generated and compared to each other to ascertain the differential benefit in drug response from various regimens. Biosimulation identified CDK4/6 inhibitors, nelfinavir and leflunomide to be effective agents singly and in combination. Upon receiving this treatment, the patient achieved a prompt and clinically meaningful remission lasting 6 months. Biosimulation has utility to identify active treatment combinations, stratify treatment options and identify investigational agents relevant to patients' comprehensive genomic abnormalities. Additionally, the combination of abemaciclib and nelfinavir appear promising for GBM and potentially other cancers harboring chromosome 12q amplification.

CTIM-08. A PILOT STUDY OF ABEMACICLIB WITH BEVACIZUMAB IN RECURRENT GLIOBLASTOMA PATIENTS WITH LOSS OF CDKN2A/B OR GAIN OR AMPLIFICATION OF CDK4/6

Abstract The recurrence rate for glioblastomas is essentially 100% and median overall survival (OS) for recurrent glioblastoma patients is usually poor, approximately 6-8 months from first recurrence. There is an unmet need in recurrent glioblastomas for novel therapeutic options with favorable safety profiles and potentially longer OS. PURPOSE The goal was to assess the impact of treating recurrent Glioblastoma patients whose tumors harbor loss of CDKN2A and/or CDKN2B, and/or copy gains or amplifications of CDK4 and/or CDK6 with dual therapy Abemaciclib with Bevacizumab. METHODS This was a single institution, pilot study (N = 10) of recurrent glioblastoma patients given the combination of Abemaciclib with Bevacizumab. Study patients received the combination of Abemaciclib at 150 mg po bid daily along with intravenous Bevacizumab at 10 mg/kg once every 2 weeks within a 28-day cycle. Staging brain MRIs with contrast were obtained every 8 weeks. Trial patients were removed from the study for significant treatment toxicities, clinical or MRI progression, patient choice, or death. RESULTS A total of 10 patients were enrolled in the study. There were 3 patients initially enrolled that were evaluated for safety followed by the additional 7 patients meeting clinical accrual from Jan. 2020-Sept. 2021. A total of 9 patients received at least one cycle (M = 6, F = 3). Preliminary findings revealed a median PFS of 14 weeks (range 5 weeks–25 weeks) and median OS of 20 weeks (range 5-70 weeks). CONCLUSION The combination of Abemaciclib with Bevacizumab compared to monotherapy Bevacizumab, surprisingly, had poorer outcomes. In a 2014 Bevacizumab study in recurrent glioblastomas, the median PFS was 13 weeks and OS 34.8 weeks compared to our combination therapy study of 14 weeks and 20 weeks, respectively. It is postulated that the use of Bevacizumab with Abemaciclib caused a drug-drug interaction that led to poor outcomes in our pilot study.

Abemaciclib in combination with pembrolizumab for HR+, HER2− metastatic breast cancer: Phase 1b study

This nonrandomized, open-label, multi-cohort Phase 1b study (NCT02779751) investigated the safety and efficacy of abemaciclib plus pembrolizumab with/without anastrozole in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) metastatic breast cancer (MBC) without prior CDK4 and 6 inhibitor exposure. Patients were divided into two cohorts: treatment naïve (cohort 1) and pretreated (cohort 2). Patients received abemaciclib plus pembrolizumab with (cohort 1) or without (cohort 2) anastrozole over 21-day cycles. The primary objective was safety, and secondary objectives included efficacy and pharmacokinetics (PK). Cohort 1/2 enrolled 26/28 patients, respectively. Neutropenia (30.8/28.6%), AST increase (34.6/17.9%), ALT increase (42.3/10.7%), and diarrhea (3.8/10.7%) were the most frequent grade ≥3 adverse events in cohort 1/2, respectively. A total of two deaths occurred, which investigators attributed to treatment-related adverse events (AEs), both in cohort 1. Higher rates of all grade and grade ≥3 interstitial lung disease (ILD)/pneumonitis were observed compared to previously reported with abemaciclib and pembrolizumab monotherapy. The PK profiles were consistent between cohorts and with previous monotherapy studies. In cohorts 1/2, the overall response rate and disease control rate were 23.1/28.6% and 84.6/82.1%, respectively. Median progression-free survival and overall survivals were 8.9 (95% CI: 3.9–11.1) and 26.3 months (95% CI: 20.0–31.0) for cohort 2; cohort 1 data are immature. Abemaciclib plus pembrolizumab demonstrated antitumor activity, but high rates of ILD/pneumonitis and severe transaminase elevations occurred with/without anastrozole compared to the previous reporting. Benefit/risk analysis does not support further evaluation of this combination in the treatment of HR+, HER2− MBC.

175 (PB055) - Abemaciclib drug combination screening with other targeted therapies in complex multicellular tumor spheroids

Drug combinations are frequently used to improve clinical efficacy, to minimize toxicity, and to reduce the development of resistance. Here, we investigated the growth inhibitory activity of the CDK4/6 inhibitor abemaciclib in combination with other targeted agents. Twelve well-characterized patient-.derived cancer cell lines from the NCI Patient-Derived Models Repository (https://pdmr.cancer.gov/models/database.htm) and seven established cell lines from the NCI-60 human tumor cell line panel were grown as multicellular 3D complex spheroids.

1423TiP CYCLONE 3: A phase III, randomized, double-blind, placebo-controlled study of abemaciclib in combination with abiraterone plus prednisone in men with high-risk metastatic hormone-sensitive prostate cancer (mHSPC)

Landmark trials led to the integration of docetaxel (D) or novel hormonal agents (NHA) added to androgen deprivation therapy (ADT) into the treatment paradigm for mHSPC. Recent data showed survival benefit for treatment intensification with ADT+D+NHA triplet therapy vs ADT+D in selected patients (pts). Yet, there is a significant medical need to expand therapeutic options especially for pts with poor prognoses, including those not candidates for chemotherapy. Abemaciclib is an oral selective inhibitor of cyclin-dependent kinase 4 and 6 (CDK4 & 6) dosed on a continuous schedule, approved for the treatment of advanced or metastatic and certain types of high-risk early stage HR+, HER2- breast cancer.

Selinexor inhibits growth of patient derived chordomas in vivo as a single agent and in combination with abemaciclib through diverse mechanisms.

Chordoma is a rare cancer that grows in the base of the skull and along the mobile spine from remnants of embryonic notochord tissue. The cornerstone of current treatments is surgical excision with adjuvant radiation therapy, although complete surgical removal is not always possible. Chordomas have high rates of metastasis and recurrence, with no approved targeted agents. Selinexor and eltanexor are selective inhibitors of nuclear export (SINE) that prevent the karyopherin protein exportin-1 (XPO1) from shuttling its cargo proteins through nuclear pore complexes out of the nucleus and into the cytoplasm. As cancer cells overexpress XPO1, and many of its cargos include tumor suppressor proteins and complexes bound to oncogene mRNAs, XPO1 inhibition can suppress oncogene translation and restore tumor suppressor protein activity in different cancer types. SINE compounds have exhibited anti-cancer activity in a wide range of hematological and solid tumor malignancies. Here we demonstrate the preclinical effectiveness of SINE compounds used as single agents or in combination with either the proteasome inhibitor, bortezomib, or the CDK4/6 inhibitor, abemaciclib, against various patient- derived xenograft (PDX) mouse models of chordoma, which included clival and sacral chordomas from adult or pediatric patients with either primary or metastatic disease, with either differentiated or poorly differentiated subtypes. SINE treatment significantly impaired tumor growth in all five tested chordoma models, with the selinexor and abemaciclib combination showing the strongest activity (tumor growth inhibition of 78-92%). Immunohistochemistry analysis of excised tumors revealed that selinexor treatment resulted in marked induction of apoptosis and reduced cell proliferation, as well as nuclear accumulation of SMAD4, and reduction of Brachyury and YAP1. RNA sequencing showed selinexor treatment resulted in differences in activated and repressed signaling pathways between the PDX models, including changes in WNT signaling, E2F pathways and glucocorticoid receptor signaling. This is consistent with SINE-compound mediated XPO1 inhibition exhibiting anti-cancer activity through a broad range of different mechanisms in different molecular chordoma subsets. Our findings validate the need for further investigation into selinexor as a targeted therapeutic for chordoma, especially in combination with abemaciclib.

CDK4/6 inhibitors improve the anti-tumor efficacy of lenvatinib in hepatocarcinoma cells.

Hepatocellular carcinoma (HCC) is the most frequent primary liver cancer with a poor prognosis and limited treatment options. Considering that alterations of the CDK4/6-cyclin D-Rb pathway occur frequently in HCC, we tested the efficacy of two CDK4/6 inhibitors, abemaciclib and ribociclib, in combination with lenvatinib, a multi-kinase inhibitor approved as first-line therapy for advanced HCC, in a panel of HCC Rb-expressing cell lines. The simultaneous drug combinations showed a superior anti-proliferative activity as compared with single agents or sequential schedules of treatment, either in short or in long-term experiments. In addition, the simultaneous combination of abemaciclib with lenvatinib reduced 3D cell growth, and impaired colony formation and cell migration. Mechanistically, these growth-inhibitory effects were associated with a stronger down-regulation of c-myc protein expression. Depending on the HCC cell model, reduced activation of MAPK, mTORC1/p70S6K or src/FAK signaling was also observed. Abemaciclib combined with lenvatinib arrested the cells in the G1 cell cycle phase, induced p21 accumulation, and promoted a stronger increase of cellular senescence, associated with elevation of β-galactosidase activity and accumulation of ROS, as compared with single treatments. After drug withdrawal, the capacity of forming colonies was significantly impaired, suggesting that the anti-tumor efficacy of abemaciclib and lenvatinib combination was persistent.Our pre-clinical results demonstrate the effectiveness of the simultaneous combination of CDK4/6 inhibitors with lenvatinib in HCC cell models, suggesting that this combination may be worthy of further investigation as a therapeutic approach for the treatment of advanced HCC.

EE183 Cost-Effectiveness Analysis of Early Versus Delayed Use of Abemaciclib Combination Treatment in Patients with HR+/HER2- High-Risk Early Breast Cancer: A US Payer Perspective

Clinical guidelines recommend use of abemaciclib, a cyclin-dependent kinase 4 and 6 inhibitor, in combination with endocrine therapy (ET) as adjuvant treatment for patients with hormone receptor-positive (HR+), HER2-negative (HER2-) early breast cancer (EBC) at high risk of recurrence or in combination with fulvestrant if patients develop metastatic breast cancer (MBC). We evaluated the cost-effectiveness of early use of abemaciclib and ET combination as first-line adjuvant therapy and then use of fulvestrant after developing MBC (early use) versus ET treatment in EBC followed by delayed use of combination abemaciclib and fulvestrant in MBC (delayed use).

Gilteritinib Enhances Anti-Tumor Efficacy of CDK4/6 Inhibitor, Abemaciclib in Lung Cancer Cells.

Abemaciclib is a cyclin-dependent kinases 4/6 (CDK4/6) inhibitor approved for the treatment of metastatic breast cancer. Preclinical studies suggest that abemaciclib has the potential for lung cancer treatment. However, several clinical trials demonstrate that monotherapy with abemaciclib has no obvious superiority than erlotinib to treat lung cancer patients, limiting its therapeutic options for lung cancer treatment. Here, we show that the US Food and Drug Administration (FDA)-approved drug, gilteritinib, enhances the cytotoxicity of abemaciclib through inducing apoptosis and senescence in lung cancer cells. Interestingly, abemaciclib in combination with gilteritinib leads to excessive accumulation of vacuoles in lung cancer cells. Mechanistically, combined abemaciclib and gilteritinib induces complete inactivation of AKT and retinoblastoma (Rb) pathways in lung cancer cells. In addition, RNA-sequencing data demonstrate that combination of abemaciclib and gilteritinib treatment induces G2 phase cell-cycle arrest, inhibits DNA replication, and leads to reduction in homologous recombination associated gene expressions. Of note, abemaciclib-resistant lung cancer cells are more sensitive to gilteritinib treatment. In a mouse xenograft model, combined abemaciclib and gilteritinib is more effective than either drug alone in suppressing tumor growth and appears to be well tolerated. Together, our findings support the combination of abemaciclib with gilteritinib as an effective strategy for the treatment of lung cancer, suggesting further evaluation of their efficacy is needed in a clinical trial.

Abstract 1881: Drug combination screening of Ipatasertib and Abemaciclib with other targeted agents in complex multicellular tumor spheroids from the NCI-60 and the National Cancer Institute’s Patient-Derived Models Repository

Abstract Drug combinations are frequently used to improve clinical efficacy, to minimize toxicity, and to reduce the development of drug resistance. Here, we investigated the growth inhibitory activities of the pan-Akt inhibitor ipatasertib and the CDK4/6 inhibitor abemaciclib in combination with other targeted agents. Twelve well-characterized patient-derived cancer cell lines from the National Cancer Institute’s Patient-Derived Models Repository (https://pdmr.cancer.gov/models/database.htm) and seven established cell lines from the NCI-60 tumor cell line panel (https://dtp.cancer.gov/discovery_development/nci-60/cell_list.htm) were grown as multicellular 3D complex spheroids. The complex spheroids, a mixture of tumor cells (60%), endothelial cells (25%), and mesenchymal stem cells (15%), were grown for 3 days before drug(s) were added. All agents were tested both alone and in combinations at multiple concentrations up to their reported clinical Cmax value and cell viability was assayed using CellTiter-Glo 3D seven days after drug exposure. While abemaciclib had minimal activity as a single agent, ipatasertib was noticeably selective for tumor cells harboring activating PI3K/AKT/mTOR pathway variants. Dual inhibition of the PI3K/AKT/mTOR and RAS/MEK/ERK pathways was one of the most effective combinations. For example, the combination of ipatasertib with the MEK inhibitor selumetinib or the ERK inhibitor ravoxertinib resulted in additive and/or synergistic cytotoxicity in over half the complex spheroid models screened. The V600E variant-specific BRAF inhibitor vemurafenib and the KRAS G12C selective inhibitor sotorasib in combination with ipatasertib showed activity in the one BRAF V600E and two KRAS G12C variant containing complex spheroid models, respectively. Another effective ipatasertib combination was vertical inhibition of the PI3K/AKT/mTOR pathway with the mTORC1/2 kinase inhibitor sapanisertib, which demonstrated additive and/or synergistic responses across multiple complex spheroid models. For abemaciclib, the most successful combination was with the CDK2/7/9 inhibitor BMS-387032, which achieved greater than one log of cytotoxicity in the majority of the complex spheroid models. For the combination of abemaciclib and selumetinib, there was a high correlation between the responses of two patient-derived cell lines grown as complex spheroids and their corresponding patient-derived xenografts (PDX). Additional PDX studies are planned for promising drug combinations from this in vitro screen. This project was funded in part with federal funds from the NCI, NIH, under contract no. HHSN261201500003I. Citation Format: Thomas Steven Dexheimer, Thomas Silvers, Rene Delosh, Julie Laudeman, Russell Reinhart, Chad Ogle, Siddhartha Paul, Nathan P. Coussens, Ralph E. Parchment, Joel Morris, John Wright, Naoko Takebe, Beverly A. Teicher, James H. Doroshow. Drug combination screening of Ipatasertib and Abemaciclib with other targeted agents in complex multicellular tumor spheroids from the NCI-60 and the National Cancer Institute’s Patient-Derived Models Repository [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1881.

Abstract 1857: Glioblastoma growth is suppressed dual inhibition of EGFR and CDK6 kinases

Abstract Glioblastoma (GBM) is a malignant brain tumor that has proven difficult to treat, despite expressing promising targets such as EGFRvIII. EGFRvIII, a mutant version of the epidermal growth factor receptor (EGFR), is constitutively active and not present in normal brain cells. The tumor specificity of EGFRvIII and the frequent EGFR amplification seen in GBM make EGFR a potentially attractive therapeutic target; however, clinical studies have shown little to no efficacy for EGFR tyrosine kinase inhibitors (TKI). One reason for this lack of efficacy may be adaptive resistance. We used RNA sequencing and multiplexed inhibitor beads with mass spectrometry (MIB-MS) to study the transcriptomes and kinomes of genetically engineered mouse astrocytes to investigate this resistance and identify potential targets for dual inhibition. Out of 329 kinases detected by MIB-MS, 76 were differentially expressed between cells with Cdkn2a deletion (“C”) and cells that also overexpressed EGFRvIII (“CEv3”). Thirty-four of these kinases were overexpressed in the CEv3 cells relative to the parental C cells (log2 fold change of 5.6, p<1x105). One of these kinases, Cdk6, is also significantly overexpressed in CEv3 cells versus cells that have a further loss of function mutation of Pten (“CEv3P”) (log2 fold change of 5.6, p<1x105). Despite this significant differential expression at the protein level, RNA expression of Cdk6 was similar between cell lines. When these cells were treated with the CDK6 inhibitor abemaciclib, CEv3 cells were found to be significantly more sensitive to inhibition than C and CEv3P cells (IC50 of 0.10 μM vs. 0.18 μM and 0.23 μM, respectively). Similarly, when cells were treated with abemaciclib in combination with the EGFR inhibitor neratinib, there was significantly higher synergy in CEv3 cells than C or CEv3P cells. Genotypically-matched patient-derived xenograft (PDX) cells were assayed for EGFR-CDK6 inhibitor synergy and showed a similar pattern of greater synergy in cells with EGFRvIII overexpression and functional PTEN than cells with EGFRvIII overexpression and PTEN loss. CEv3 and CEv3P cells were orthotopically implanted into mice and treated with neratinib, abemaciclib, or a combination. In CEv3-injected mice, combination treatment led to significantly longer survival than either single agent or control treatment. However, in CEv3P-injected mice, no survival difference was seen between any of the treatment arms. Taken together, these data provide strong evidence that CDK6 is a promising target for combination treatment with EGFR inhibitors in glioblastoma. Citation Format: Erin Smithberger, Abigail K. Shelton, Ryan E. Bash, Madison K. Butler, Alex R. Flores, Allie Stamper, Steven P. Angus, Michael P. East, Gary L. Johnson, Michael E. Berens, Frank B. Furnari, Ryan Miller. Glioblastoma growth is suppressed dual inhibition of EGFR and CDK6 kinases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1857.

Phase 3 ENABLAR-2 study to evaluate enobosarm and abemaciclib combination compared to estrogen-blocking agent for the second-line treatment of AR+, ER+, HER2- metastatic breast cancer in patients who previously received palbociclib and estrogen-blocking agent combination therapy.

TPS1121 Background: Targeting the androgen receptor (AR) may be the next important endocrine therapy for advanced breast cancer. The AR has been demonstrated to be a tumor suppressor when activated. Enobosarm is an oral selective AR targeting agonist that activates the AR in breast cancer. Preclinical studies in CDK4/6 inhibitor resistant PDX models demonstrated combinatorial synergistic activity of enobosarm plus CDK 4/6 inhibitors. An open-label, Phase 2 study, was conducted in 136 women with heavily pretreated ER+ HER2- metastatic breast cancer that were randomized to oral daily enobosarm at a dose of 9 or 18 mg. The efficacy evaluable (EE) group were patients that were AR positive (> 10% AR nuclear staining). In the EE population with measurable disease at baseline, 10 patients had received prior endocrine therapy + a CDK 4/6 inhibitor. Subsequent treatment with enobosarm resulted in a clinical benefit rate of 50% and the best overall response rate (ORR) was 30% (2CRs and 1 PR). Of the 10 patients, 7 had AR nuclear staining ≥40%. None of the patients with AR nuclear staining < 40% responded to enobosarm. Although a small subset of the study, it appears that enobosarm has activity in patients who had ≥40% AR staining and who had progressed on standard endocrine therapy with a CDK 4/6 inhibitor. Overall, treatment with enobosarm was well tolerated with significant positive effects on quality-of-life measurements. Methods: The ENABLAR-2 trial is an ongoing Phase 3, randomized, open-label, efficacy and safety study in patients with AR+ ER+ HER2- MBC with AR nuclear staining of ≥40%, who have progressed after one line of systemic therapy comprising estrogen blocking agent and palbociclib. The planned sample size is 186 patients randomized 1:1 to enobosarm + abemaciclib OR fulvestrant if the first line of therapy for MBC was a non-steroidal AI plus palbociclib, until disease progression, toxicity, or loss of clinical benefit. If first line therapy for metastatic breast cancer was fulvestrant plus palbociclib, then the patient will be randomized 1:1 to either enobosarm + abemaciclib OR an AI. Randomization will be stratified by AR% nuclear staining, ≥60% versus < 60%, as well as by estrogen blocking agent such that each cohort will have the same number of subjects previously receiving fulvestrant + palbociclib in first line therapy. The key objectives are to determine the safety and efficacy of enobosarm and abemaciclib combination versus an alternative estrogen blocking agent with the primary endpoint of PFS. Secondary endpoints include ORR, duration of response, overall survival, change from baseline in Short Physical Performance Battery (SPPB), change in EORTC Quality of Life Questionnaire (EORTC-QLQ) and change in body composition as measured by DEXA. Clinical trial information: NCT05065411.

Pharmacological reactivation of RBL2/p130 could be an effective antitumoral strategy for malignant pleural mesothelioma

Malignant mesothelioma (MM) is an aggressive tumor developing from the mesothelium covering the body cavities. The most common MM type affects the pleura surrounding the lungs. MM is mainly associated with asbestos exposure. At present, no curative modalities are effective against MM exist. The molecular mechanisms underlying MM development seem to depend mostly on the inactivation of tumor suppressors, among which also the dysfunction of the retinoblastoma (RB) protein pathway that is a hallmark of cancers. We previously demonstrated that RBL2/p130 is a direct AKT target and its reactivation following AKT inhibition mediates apoptosis in MM.So, we hypothesize that concomitant inhibition of CDK and AKT activity, both converging on the reactivation of RBL2/p130 tumor suppressor role, synergize in counteracting MM.We first assessed, through an MTS assay, the effect of three new generation CDK inhibitors (CDKi), palbociclib, ribociclib, abemaciclib, on the cell viability of MM (NCI‐H28, IST‐MES TWO, NCI‐H2452, MMB, MSTO‐211H, NCI‐H2052) and immortalized human normal mesothelial (MET‐5A) cells at 72h. Then, to verify whether CDKi exerted long‐term cell growth inhibition, we performed clonogenic assays upon treatment of all the MM All the MM and mesothelial cell lines. Finally, we also examined, by MTS, the possible synergistic effects of abemaciclib in combination with an AKT inhibitor (AKT1/2 VIII).Our preliminary data show that ribociclib and palbociclib only moderately reduce viability of the MPM cells, whereas abemaciclib shows cytotoxic effects at very low doses in all MM cell lines. Abemaciclib treatment induces a dose‐dependent cytotoxic effect in all the MM cell lines without meaningfully affecting the normal mesothelial cells. Interestingly, abemaciclib also induced a cytotoxic effect in the most aggressive histotype, the sarcomatoid NCI‐H2052 cells. To verify whether abemaciclib exerted long‐term cell growth inhibition, we performed clonogenic assays upon treatment with IC50 of abemaciclib and found that the CDKi dramatically reduced colony formation in all the MM cell lines. We also examined, by MTS, the possible synergistic effects of abemaciclib in combination with a kinase AKT inhibitor (iAKT1/2 VIII), so we treated the MM cell lines for 72 h with the two agents, both alone and in combination, at five different concentrations, in a constant ratio. The cell viability data were evaluated through the Chou–Talalay method and showed a strong synergism revealing a combination index (CI) values < 1 for all cell.Although reactivating oncosoppressor genes is difficult to achieve because they are hardly ‘druggable’, our preliminary findings will provide the rationale for pharmacological strategies able to unleash RBL2/p130 tumor suppressor potential. The pharmacological reactivation of RBL2/p130 could be an effective strategy against MM, which can be rapidly implemented in the clinical practice.