Palbociclib In Combination Research Articles

UPAR Immuno-PET in Pancreatic Cancer, Aging, and Chemotherapy-Induced Senescence.

Identifying cancer therapy resistance is a key time-saving tool for physicians. Part of chemotherapy resistance includes senescence, a persistent state without cell division or cell death. Chemically inducing senescence with the combination of trametinib and palbociclib (TP) yields several tumorigenic and prometastatic factors in pancreatic cancer models with many potential antibody-based targets. In particular, urokinase plasminogen activator receptor (uPAR) has been shown to be a membrane-bound marker of senescence in addition to an oncology target. Methods: Here, 2 antibodies against murine uPAR and human uPAR were developed as immuno-PET agents to noninvasively track uPAR antigen abundance. Results: TP treatment increased cell uptake both in murine KPC cells and in human MiaPaCa2 cells. In vivo, subcutaneously implanted murine KPC tumors had high tumor uptake with the antimurine uPAR antibody independently of TP in young mice, yet uPAR uptake was maintained in aged mice on TP. Mice xenografted with human MiaPaCa2 tumors showed a significant increase in tumor uptake on TP therapy when imaged with the antihuman uPAR antibody. Imaging with either uPAR antibody was found to be more tumor-selective than imaging with [18F]FDG or [18F]F-DPA-714. Conclusion: The use of radiolabeled uPAR-targeting antibodies provides a new antibody-based PET imaging candidate for pancreatic cancer imaging as well as chemotherapy-induced senescence.

A Kinome-Wide Synthetic Lethal CRISPR/Cas9 Screen Reveals That mTOR Inhibition Prevents Adaptive Resistance to CDK4/CDK6 Blockade in HNSCC.

A kinome-wide CRISPR/Cas9 screen identified cell-cycle inhibition as a synthetic lethal target of mTORis. A combination of mTORi and palbociclib, a CDK4/6-specific inhibitor, showed strong synergistic effects in HNSCC. Mechanistically, mTORis inhibited palbociclib-induced increase in CCNE1.

Pyrotinib and trastuzumab plus palbociclib and fulvestrant in HR+/HER2+ breast cancer patients with brain metastasis

Human epidermal growth factor receptor 2-positive (HER2+) breast cancer (BC) patients are at a high risk of developing metastases in the brain. However, research focusing on treatment strategies for hormonal receptor positive (HR+), HER2+ BC patients with brain metastases (BM) remains limited. Thus, a multi-center, prospective trial was conducted in China. Women over the age of 18 who were naive to whole brain radiotherapy and had estrogen receptor (ER)/progesterone-receptor (PgR) positive, HER2+ BM were treated with palbociclib, fulvestrant, trastuzumab and pyrotinib, until disease progression or the development of intolerable side effects. The primary endpoint was objective response rate (ORR) in the central nervous system (CNS). This ongoing study is still recruiting participants and is registered with ClinicalTrials.gov (NCT04334330). This report presents the findings from an interim analysis. From December 4, 2020, to November 2, 2022, 15 patients were enrolled. Among the 14 patients who were evaluable for clinical response, the ORR was 35.7% (95% CI: 12.8–64.9%), with a CNS–ORR of 28.6% (95% CI: 8.4–58.1%). The median follow-up period was 6.3 months (range, 2.1–14.3 months), during which the median progression-free survival (PFS) was 10.6 months (95% CI: 4.3–16.9 months), and the median time to CNS progression was 8.5 months (95% CI: 5.9–11.1 months). The most common adverse event was diarrhea (93%), with 33% having grade 3 and 6.7% having grade 4. The study suggests that the combination of palbociclib, trastuzumab, pyrotinib and fulvestrant offers a promising chemo-free treatment strategy for HR+, HER2+ BC patients with BM.

Primary results from PATRICIA cohort C (SOLTI-1303), a randomized phase II study evaluating palbociclib with trastuzumab and endocrine therapy in pretreated HER2-positive and PAM50 luminal advanced breast cancer.

1008 Background: The PATRICIA trial (cohorts A-B) demonstrated that palbociclib plus trastuzumab (T) is safe and active in patients (pts) with T-pretreated HER2-positive Hormone Receptor-positive (HR+/HER2+) PAM50 Luminal advanced breast cancer (ABC). Here, we present the primary efficacy analysis of the randomized cohort C from the PATRICIA trial that compares the efficacy of palbociclib + T + endocrine therapy (ET) with treatment of physicians’ choice (TPC). Methods: PATRICIA (cohort C) is a randomized, open-label, phase II study conducted at 34 sites in Spain recruiting from August 2019 to August 2023. Pts with HER2+/HR+ and centrally tested PAM50 Luminal A or B intrinsic subtype ABC who had received at least one prior line of anti-HER2 based regimens were eligible. Pts were randomized 1:1 to Cohort C1 (Palbociclib 125 mg/day orally 3 weeks/1 week off + T + ET) or Cohort C2 (TPC, including T + any ET or chemotherapy (CT) + T, or T-DM1). The stratification factors were number of previous regimens for ABC and presence of visceral disease. The primary endpoint was progression-free survival (PFS). The trial was designed to recruit a total of 102 pts, having an 80% power with one-sided alpha=0.1 to detect a HR of 0.62 in favor of the palbociclib cohort. The study was closed after 73 pts were randomized due to slow recruitment. Results: At data cut-off, 264 pts were pre-screened, and 73 pts were randomized. Baseline pts characteristics are summarized in Table 1. In cohort C1, 50% of the pts received fulvestrant and 50% aromatase inhibitor as ET. In cohort C2, 37.1% of pts were treated with TDM-1, 45.7% with CT+ T, 11.4 % with ET + T and two pts withdrew their consent before starting the treatment. Palbociclib + T + ET was associated with longer PFS compared to TPC (median 9.1 vs 7.5 months, stratified HR=0.52 [95%CI 0.29-0.94]; two-sided p=0.031); 12-months PFS rates were 43.7% and 21.4%, respectively. The overall response rate was 18.9% (95% CI 8.6-35.7) in cohort C1 and 8.3% (95% CI 1.4-28.5) in cohort C2. Grade ≥3 adverse events occurred in 63.2% of pts in C1 and 45.5% in C2 cohort. The most frequent grade ≥3 adverse event in the experimental arm was neutropenia (55.3%). Conclusions: The combination of palbociclib, T and ET showed a statistically significant improvement in PFS in patients with previously treated PAM50 luminal A or B HER2+ advanced breast cancer, as compared to TPC. Clinical trial information: NCT02448420 . [Table: see text]

Real-world treatment patterns and clinical outcomes among patients with HR+/HER2- advanced/metastatic breast cancer receiving palbociclib in Brazil: IRIS study.

e13088 Background: Palbociclib was approved for hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) advanced/metastatic breast cancer (aBC/mBC) in Brazil in 2018. Worldwide studies explore palbociclib's real-world use and outcomes; however, this data is not available for Brazilian patients. IRIS Brazil study aimed to describe demographic/clinical characteristics, treatment and clinical outcomes of adult female patients who have received palbociclib as first-line treatment for HR+/HER2- aBC/mBC in private healthcare institutions in Brazil. Methods: This retrospective descriptive study included females aged 18 years or older diagnosed with HR+/HER2- aBC/mBC and those who had received palbociclib as their initial line of therapy. The study analyzed variables such as demographics, clinical characteristics, treatment history, palbociclib combinations, and clinical outcomes. Progression-free survival (PFS) and overall survival (OS) were calculated using Kaplan-Meier estimates at 6- and 12-month time points. Results: A total of 121 patients were included in the study. The mean age was 54.4 years, and 82 (67.7%) were menopausal at diagnosis. A total of 51 patients (42.1%) were treated with palbociclib + fulvestrant, while 67 (55.8%) were treated with palbociclib + aromatase inhibitors. The majority of patients (n = 79; 65.3%) did not require any dose adjustments. Among the 40 patients (33.1%) who required dose adjustments, the main reason was adverse events/toxicity (n = 36; 90%). The PFS rates at 6 and 12 months were 78% and 60%, respectively. The OS rates at 6 and 12 months were 86% and 70%, respectively. Conclusions: Results from this initial real-world assessment of clinical outcomes in Brazil suggest that Palbociclib combinations exhibit favorable effectiveness in treating HR+/HER2- aBC/mBC disease, as measured by PFS and OS rates.

Abstract PO4-05-04: Comparative effectiveness of Palbociclib plus Aromatase inhibitor versus fulvestrant alone as initial endocrine therapy for HR+/HER2- advanced breast cancer in Chinese clinical practice: a real-world study

Abstract Background: In the real world, there are still a large number of HR+/HER2- advanced breast cancer patients receiving initial endocrine therapy with fulvestrant monotherapy in China, especially patients with bone metastases only. It is due to lack of data comparing the effective between Palbociclib combined with AI and fulvestrant monotherapy as initial endocrine therapy. On the other hand, there are economic factors and access issues. According to the National Cancer Center's previous clinical experience, Palbociclib combined with AI is superior to fulvestrant monotherapy in HR+/HER2- advanced breast cancer patients receiving initial endocrine therapy. Therefore, we collected and summarized the previous clinical data in our center to compare the effective of Palbociclib combined with AI and fulvestrant monotherapy for HR+/HER2-advanced breast cancer patients receiving initial endocrine therapy in China. Patients and methods: This is a retrospective real-world study of multicenter studies. It aimed at verifying the effective of Palbociclib combined with AI and fulvestrant monotherapy for HR+/HER2-advanced breast cancer patients receiving initial endocrine therapy in China. A total of 392 patients with ≥3 months of follow-up received Palbociclib plus AI or fulvestrant alone in the first-line setting between April 1, 2015 and February 1, 2023. Stabilized inverse probability treatment weighting (sIPTW) was used to balance baseline demographic and clinical characteristics. Real-world progression-free survival (rwPFS) and overall survival (OS) were analyzed. Results: After sIPTW adjustment, a median follow-up of 37 months (range 34-40) in the Palbociclib group and 59 months (range 56-61) in those taking fulvestrant alone. Palbociclib combination regiment was associated with significantly longer median rwPFS compared to fulvestrant alone (22.0 vs 14.0 months; HR,0.469;95% CI 0.370–0.594, p< 0·0001). Median OS was not reached in the Palbociclib group and was 57 months (95% CI 54.0–66.0) in the fulvestrant group(HR,0.666; 95% CI 0.437–1.017, p< 0·94). Conclusion: In the real-world population of patients, palbociclib combined with AI endocrine therapy is superior to fulvestrant monotherapy in HR+/HER2- advanced breast cancer patients receiving initial endocrine therapy. PFS and OS before IPTW PFS and OS after IPTW Table patient characteristics Citation Format: Jian Yue, Xue Wang, Jie Ju, Zixiang Yang, Tong Wei, Peng Yuan, Min Gao, Ling Xu, Yin Guan. Comparative effectiveness of Palbociclib plus Aromatase inhibitor versus fulvestrant alone as initial endocrine therapy for HR+/HER2- advanced breast cancer in Chinese clinical practice: a real-world study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-05-04.

Abstract PS12-07: Phase II clinical trial of palbociclib and binimetinib in advanced triple-negative breast cancer (TNBC) with hyperactivation of ERK and/or CDK4/6

Abstract Background: We previously demonstrated that a kinase-based taxonomy of TNBC was most parsimonious than next-generation sequencing in defining TNBC subtypes associated with prognostic categories in early disease. The most aggressive TNBC variants were driven by a heterogeneous set of genetic aberrations that converged in the increased activity of 6 kinases: KIT, PNKP, PRKCE, P70S6K, ERK and CDK6 (Nat Commun; 9:3501-18). The combined inhibition of these kinases in pairs led to potent tumor regression in preclinical models, being the most powerful combination that one directed against CDK6 and ERK. This prompted us to design a phase II trial testing the combination of palbociclib (against CDK6) and binimetinib (against the ERK upstream kinase MEK, since no ERK inhibitor was available at that moment outside phase I trials) in advanced TNBC. Hyperactivation of CDK6 and/or ERK was selected as entry criterion. Trial design: This was a single-arm, prospective, multicentric, open-label, phase II investigator-initiated trial. CDK6 and phosphor-ERK levels were measured in tumor samples by immunohistochemistry and normalized with a reference sample collection to a Z-score. Patients with scores for either kinase above the median were candidates for the trial. Key inclusion criteria included metastatic >18year-old TNBC, adequate organ function, measurable disease, and progression to 1-2 prior treatment lines (including immunotherapy, and a PARP inhibitor in case of germline BRCA1/2 mutation). Patients started continuous oral binimetinib at 45 mg/BID and palbociclib 100 mg/day from days 1 to 21, in 28-day cycles. Patients experiencing ≤ grade 1 tolerable side effects as the greatest toxicity were escalated to palbociclib to 125 in cycle 2. RECIST 1.1 and NCI CTC AE V 5.0 were used for assessing disease control (q8 weeks) and toxicity. The primary aims were to assess the efficacy and toxicity of this combination, and the secondary one to detect biomarkers of activity. At the time of trial design, in absence of available Sacituzumab for prescription, the reference PFS to beat in advanced lines for physician’s choice in TNBC was 1.7 month (NEJM; 384:1529-41, 2021). With alpha and beta errors of 0.05 and 0.2, the minimum number of patients to demonstrate a 30% improvement in PFS to 2.5 months was 25. Results: From November 2020 to April 2023, 69 patients were screened and 24 entered the trial (5 positive for phosphor-ERK; 2 for CDK6; 17 for both). Toxicity was generally mild and included grade 1-2 diarrhea (33% of the patients), grade 1-2 asthenia (50%), grade 1-3 neutropenia (75%), grade 2 retinal toxicity (8.3%) and grade 3 rash (4.2%); no grade 4/5 toxicities were observed. Median PFS was 1.83 months (range 0.3 to 11.3+). Phospho-ERK and CDK6 levels were not correlated (Pearson’s R= -0.089; P=0.68); CDK6 levels did not show association with PFS time (R = -0.120; P=0.58). Interestingly, however, phosphor-ERK levels in the baseline tumor sample showed correlation with PFS time (R = 0.428; P=0.037). Conclusion: The combination of palbociclib and binimetinib was generally safe, and PFS time showed correlation with baseline phosphorylation levels of ERK. However, the trial did not meet its primary endpoint. Citation Format: Rodrigo Sánchez-Bayona, Alfonso Cortes, Juan Miguel Cejalvo, Luis Manso, Serafin Morales, Jose A Garcia-Saenz, Jorge Silva, Juan A Guerra, Diego Malón-Giménez, Silvana Mouron, Eduardo Caleiras, Miguel Quintela-Fandino. Phase II clinical trial of palbociclib and binimetinib in advanced triple-negative breast cancer (TNBC) with hyperactivation of ERK and/or CDK4/6 [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS12-07.

Abstract PO4-19-08: Randomized phase II study of talazoparib vs talazoparib plus atezolizumab for patients with premenopausal HR+/HER2- metastatic breast cancer harboring homologous recombination deficiency scar (Young-PALETTA, KCSG BR21-09)

Abstract Background Cyclin D kinase-4/6(CDK4/6) inhibitor combined with endocrine treatment have significantly increased progression free survival(PFS) and overall survival(OS) of patients with hormone receptor(HR)-positive/HER2-negative metastatic breast cancer, and currently is a standard 1st line endocrine treatment option. Homologous recombination deficiency(HRD) including germline(g) BRCA1/2 pathogenic mutation is known to be prevalent among young premenopausal patients. Recently several retrospective data suggested that patients with germline BRCA1/2 pathogenic mutation or HRD have poorer outcome with CDK4/6 inhibitor treatment, however there is no prospective evidence. Poly ADP-ribose polymerase(PARP) inhibitors have shown significant benefit over standard chemotherapy in patients with HER2-neg metastatic breast cancer and gBRCA1/2 pathogenic mutation in two Phase 3 trials. Since preclinical data suggested that PARP inhibitors play a role in anti-tumor immune modulation, immunotherapy combined with PARP inhibitors were explored and showed promising antitumor efficacy in several single arm trials. In this trial, we investigate talazoparib and atezolizumab combination compared with talazoparib monotherapy in premenopausal women with HR+/HER2- metastatic breast cancer with HRD-scar after failure with 1st line palbociclib and endocrine treatment combination. Methods This study is a multicenter, randomized, open-label phase II trial comparing talazoparib versus talazoparib with atezolizumab in premenopausal women with HR+/HER2- metastatic breast cancer harboring HRD scar whose disease have progressed with endocrine and palbociclib combination as the 1st-line endocrine treatment. Prior one line of cytotoxic chemotherapy other than platinum for metastatic setting is allowed, but prior palliative endocrine treatment is not allowed. Eligible patients will be pre-screened with tumor tissue biopsy and peripheral blood sampling before endocrine and palbociclib treatment commencement. HRD status is determined through targeted sequencing(SOLIDaccuTestTM by NGeneBio) of tumor tissue and germline HRD genes including BRCA1/2 variant test. Whole genome sequencing and RNA sequencing are performed for biomarker analyses. Patients harboring HRD scar will receive first line endocrine treatment with palbociclib plus aromatase inhibitor with ovarian suppression. After progression with 1L endocrine treatment, patients will be randomized to either talazoparib alone or talazoparib plus atezolizumab combination. Germline BRCA1/2 pathogenic mutation is a stratification factor. Primary endpoint is a progression free survival after randomization(PFS2). Secondary objectives are a composite of PFS1 and PFS2, PFS1, overall survival, patient reported outcome, and biomarkers for treatment response. A total of 178 subjects are required to detect hazard ratio of 0.62 (median PFS2 of at least 10.5 months with talazoparib and atezolizumab combination vs 6.5 months with talazoparib alone), to achieve 80% power at a two-sided a significance level at 10%, considering drop-out rate of 5%. The study period is expected to be 72 months overall(36 months for accrual and randomization and 24 months of follow-up for primary endpoint PFS2). Citation Format: Hee Kyung Ahn, Jieun Lee, Jee Hung Kim, Kyung-Hun Lee, Jee Hyun Kim, Min Hwan Kim, Minsuk Kwon, Han Jo Kim, Kyung Hae Jung, Yeon Hee Park. Randomized phase II study of talazoparib vs talazoparib plus atezolizumab for patients with premenopausal HR+/HER2- metastatic breast cancer harboring homologous recombination deficiency scar (Young-PALETTA, KCSG BR21-09) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-19-08.

Abstract RF02-01: A Multicenter, Phase I/II Trial of Anastrozole, Palbociclib, Trastuzumab, and Pertuzumab in Hormone Receptor (HR)-Positive, HER2-Positive Metastatic Breast Cancer (ASPIRE)

Abstract Background: Among patients (pts) with HR-positive and HER2-positive breast cancer, crosstalk between HER2 and estrogen receptor (ER) signaling pathways may contribute to endocrine resistance but anti-HER2 agents in combination with endocrine therapy can restore endocrine sensitivity. Mechanistically, HER2/HER3 signaling promotes survival by way of PI3K-AKT activation whereas ER-CDK4/6-Rb signaling promotes cell cycle progression. The combination of anti-HER2 therapy with an aromatase inhibitor (AI) and a CDK 4/6 inhibitor would allow for blockade of both pathways and provide a novel, all biologic, and chemotherapy-free approach to the treatment of HR-positive, HER2-positive metastatic breast cancer (MBC). Methods: We conducted a phase I/II multi-institution trial in pts with previously untreated, HR-positive and HER2-positive MBC. In the Phase I portion, pts received escalating doses of palbociclib (100mg, 125mg) in conjunction with trastuzumab, pertuzumab and an AI anastrozole, using a 3+3 dose escalation trial design. In the phase II portion, pts received palbociclib at the maximum tolerated dose (MTD), anastrozole, trastuzumab, and pertuzumab. The primary endpoints of the Phase I and II portions were MTD and clinical benefit rate (CBR) defined as the sum of complete response, partial response, and stable disease for >/= 6 months, respectively. Secondary endpoints included progression free survival (PFS), objective response rate (ORR) and safety. The Phase II portion of this study was powered with 30 pts to show efficacy of palbociclib administered at the MTD in combination with anastrozole, trastuzumab and pertuzumab if the CBR achieved at 6 months exceeded 58%. The Clopper-Pearson method was used to calculate confidence intervals for ORR and CBR. The PFS distribution was estimated using the Kaplan-Meier method. Results: In the Phase I portion, a total of 9 pts were enrolled. No DLTs were observed at the 100mg dose (N=3) or the 125mg dose (N=6) level, and thus, 125mg was established as the MTD. An additional 24 pts were enrolled to the Phase II portion at the MTD, with a total of 30 pts in the modified intention-to-treat population included in the efficacy analysis. The median age of the population was 57.6 years (range 50.5-63.8) and 27% of pts were premenopausal and received ovarian function suppression as part of treatment. As shown in Table 1, the primary endpoint, CBR, was 97% (95% CI: 0.83-1.0, p<0.0001). ORR was 70% (95% CI: 0.51-0.85). Median time to objective response was 2.8 months with earliest response at 3 months. Median duration of response was not reached with range of 5.1-42.2 months. Median PFS was also not reached with range of 8-44.8 months. Safety data were consistent with known toxicity profiles of agents. Most common adverse events included diarrhea (80%), neutropenia (77%), leukopenia (70%), anemia (67%), and fatigue (60%). Grade 3-4 events occurred in 63% (19/30) of pts and included neutropenia (68%), leukopenia (32%), decrease in absolute neutrophil count (21%), and anemia (21%). Conclusions: The combination of anastrozole, palbociclib, trastuzumab, and pertuzumab was well tolerated and effective with a clinical benefit rate of 97% in pts with previously untreated HR-positive, HER2-positive MBC. The combination provides a chemotherapy-free alternative for pts with triple positive breast cancers. Further follow up will determine impact on PFS. Table 1. Results in Patients on Anastrozole, Palbociclib, Trastuzumab, and Pertuzumab Citation Format: Rima Patel, Krystal Cascetta, Paula Klein, Erin Moshier, Maryann Kwa, Julie Fasano, Anupama Goel, Melissa Accordino, Charles Shapiro, Rita Vaccaro, Gargi Atul Joshi, Joseph Sparano, Amy Tiersten. A Multicenter, Phase I/II Trial of Anastrozole, Palbociclib, Trastuzumab, and Pertuzumab in Hormone Receptor (HR)-Positive, HER2-Positive Metastatic Breast Cancer (ASPIRE) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr RF02-01.

Targeting cellular senescence as a therapeutic vulnerability in gastric cancer

AimsCellular senescence (CS) represents an intracellular defense mechanism responding to stress signals and can be leveraged as a “vulnerability” in cancer treatment. This study aims to construct a CS atlas for gastric cancer (GC) and uncover potential therapeutics for GC patients. Materials and methods38 senescence-associated regulators with prognostic significance in GC were obtained from the CellAge database to construct Gastric cancer-specific Senescence Score (GSS). Using eXtreme Sum algorism, GSS-based drug repositioning was conducted to identify drugs that could antagonize GSS in CMap database. In vitro experiments were conducted to test the effect of combination of palbociclib and exisulind in eliminating GC cells. Key findingsPatients with high GSS exhibited CS-related features, such as CS markers upregulation, adverse clinical outcomes and hypomethylation status. scRNA-seq data showed malignant cells with high GSS exhibited enhanced senescence state and more immunosuppressive signals such as PVR-CD96 compared with malignant cells with low GSS. In addition, the GSS-High cancer associated fibroblasts might secrete cytokines and chemokines such as IL-6, CXCL1, CXCL12, and CCL2 to from an immunosuppressive microenvironment, and GSS could serve as an indicator for immunotherapy resistance. Exisulind exhibited the greatest potential to reverse GSS. In vitro experiments demonstrated that exisulind could induce apoptosis and suppress the proliferation of palbociclib-induced senescent GC cells. SignificanceOverall, GSS offers a framework for better understanding of correlation between senescence and GC, which might provide new insights into the development of novel therapeutics in GC.

Abstract 7592: Combined inhibition of CDK4/6 and AKT is highly active against the luminal androgen receptor (LAR) subtype of triple negative breast cancer (TNBC)

Abstract The LAR subtype of TNBC is enriched for targetable biomarkers such as androgen receptor (AR) expression, PIK3CA mutations, and intact Rb. The purpose of this study was to investigate the most effective combination of CDK4/6, AR, and PI3K-AKT inhibitors in preclinical models of LAR TNBC. The MDAMB453 and MFM223 (AR positive/Rb intact/PIK3CAmutant) LAR TNBC cells were treated with each inhibitor alone or in combination. Drug sensitivity was assessed using colony formation, cell viability, and live-cell analysis. The Loewe additivity equation was used to measure the additive drug effects. Immunoblot analysis was used to evaluate cell cycle and PI3K-AKT signaling and ARE luciferase assay was used to assess AR transcriptional activity. MDAMB453 and MFM223 cells were sensitive to the single agents palbociclib, alpelisib, and capivasertib (IC50, ~500 nM), which inhibited CDK4/6, PI3Kα, and AKT, respectively. Enzalutamide, an AR antagonist, exerted no growth inhibitory activity (IC50, 15-25 μM). Treatment with palbociclib, alpelisib, or capivasertib did not alter the AR protein levels or transcriptional activity. The combination of palbociclib+capivasertib synergistically inhibited the proliferation of MDAMB453 and MFM223 cells (synergistic scores 7.34, p=5.81-11, and 4.78, p=0.012, respectively) better than palbociclib+alpelisib. Enzalutamide did not enhance either combination. Palbociclib+capivasertib inhibited PI3KCA-mutant and Rb-intact LAR TNBC PDX growth more potently than palbociclib+alpelisib (p=0.046). Treatment of LAR TNBC cells with palbociclib suppressed Rb phosphorylation and resulted in adaptive activation of P-AKTS473/T308 and the AKT substrates GSK3β, PRAS40, and FoxO3a after 24 h. Capivasertib inhibited the phosphorylation of AKT and AKT substrates, following CDK4/6 blockade with palbociclib, more potently than alpelisib. PI3Kβ inhibitors (TGX221, GSK2636771) did not block AKT substrate upregulation, suggesting PI3Kβ does not mediate adaptive responses. Rictor knockdown failed to reduce AKT activation following palbociclib treatment, suggesting an mTORC2-independent mechanism. Human Phospho-kinase Array of MDA-MB-453 cells treated with palbociclib showed time dependent upregulation of GSK3βS9, STAT3Y727 and PDFGRβY751. PDGFRβ activation after palbociclib treatment was confirmed in MFM223 cells. PDGFRβ siRNAs in MDAMB453 cells blocked P-AKTS473 upregulation after palbociclib treatment. Treatment with palbociclib and the PDGFRβ small-molecule antagonist CP673451 arrested LAR TNBC growth similar to palbociclib+capivasertib, suggesting an adaptive response involving PDGFRβ signaling. In conclusion, this study supports the clinical testing of the palbociclib and capivasertib combination for LAR TNBC patients and reveals adaptive responses after palbociclib treatment through PDGFRβ signaling. Citation Format: Rosario Chica-Parrado, Gun Min Kim, Yasuaki Uemoto, Dan Ye, Fabiana Napolitano, Chang-Ching Lin, Emmanuel Bikorimana, Kyung-min Lee, Saurabh Mendiratta, Ariella B. Hanker, Carlos L. Arteaga. Combined inhibition of CDK4/6 and AKT is highly active against the luminal androgen receptor (LAR) subtype of triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7592.

Abstract 7241: Combination of CDK4/6 inhibitor promotes the antitumor effect of oncolytic adenovirus against canine breast cancer cells

Abstract Background: Oncolytic virotherapy has emerged as a novel antitumor platform to induce tumor-specific cytopathic effect against human cancer cells. However, whether oncolytic virotherapy is effective to canine cancer cells remains unclear. We developed telomerase-specific oncolytic adenoviruses OBP-301 and a p53-armed OBP-702 based on human adenovirus serotype 5. OBP-301 and OBP-702 have therapeutic potential against various types of human cancer cells. As recent report has suggested that human adenovirus serotype 5 induces cytopathic effect against canine cancer cells, OBP-301 and OBP-702 are expected to have therapeutic effects against canine cancer cells. Furthermore, it has been reported that CDK4/6 inhibitors clinically used for human breast cancers promote the replication of oncolytic adenoviruses, suggesting that combination of CDK4/6 inhibitors promote the therapeutic potential of oncolytic adenoviruses. In this study, we investigated the therapeutic potential of OBP-301 and OBP-702 against canine breast cancer cells in monotherapy and combination therapy with CDK4/6 inhibitor. Methods: Two canine breast cancer cell lines (CMT-U27, AZA-CB) were used in this study. The antitumor effect of OBP-301 and OBP-702 against canine breast cancer cells was analyzed using the XTT assay. The therapeutic potential of combination therapy with CDK4/6 inhibitor (palibociclib) was further analyzed. Virus-mediated induction of adenovirus E1A and p53 expression was analyzed by Western blotting. The in vivo antitumor effects of OBP-301 and OBP-702 were assessed using CMT-U27 subcutaneous tumor model. Results: OBP-301 and OBP-702 had cytopathic effect against CMT-U27 and AZA-CB cells. The antitumor activity of OBP-702 was superior to that of OBP-301. The combination of palbociclib and OBP-301 showed a more profound antitumor effect compared with monotherapy against CMT-U27 and AZA-CB cells. The expression of E1A and p53 was increased in virus-treated CMT-U27 and AZA-CB cells in a dose-dependent manner. Intratumoral administration of OBP-301 and OBP-702 significantly suppressed the growth of subcutaneous CMT-U27 tumors compared with mock treatment. Conclusion: Our results suggest that telomerase-specific oncolytic adenoviruses have cytopathic effect against canine breast cancer cells via virus infection and replication. Furthermore, combination of CDK4/6 inhibitor may be a promising strategy for promoting the antitumor effect of oncolytic adenovirus against canine breast cancers. Citation Format: Naoyuki Hashimoto, Hiroshi Tazawa, Satoru Kikuchi, Shinji Kuroda, Yasuo Urata, Shunsuke Kagawa, Toshiyoshi Fujiwara. Combination of CDK4/6 inhibitor promotes the antitumor effect of oncolytic adenovirus against canine breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7241.

Abstract 4622: Anti-tumor activity of CDK2 inhibitor BLU-222 in combination with CDK4/6 inhibitors for overcoming resistance in HR positive and triple negative metastatic breast cancers models

Abstract Background: Cyclin-dependent-kinase-4/6 inhibitors (CDK4/6is) plus endocrine therapy (ET) are standard of care first-line treatment for patients with hormone receptor (HR)-positive, HER2-negative metastatic breast cancer (mBC). However, the emergence of resistance to CDK4/6is plus ET presents a clinical challenge with few treatment alternatives. The effectiveness of CDK4/6is in patients with triple-negative (TN) breast cancer remains uncertain, although the potential synergy with other targeted therapies is currently under investigation. Our study demonstrates the enhanced and synergistic activity of BLU-222, a selective CDK2 inhibitor, when combined with CDK4/6is in preclinical models of both HR+/HER2- and TN breast cancer resistant to CDK4/6is. Methods: Palbociclib resistant (PR) HR+/HER2- (MCF7 and T47D) and TN (MDA-MB-231 and BT-20) breast cancer cell lines were generated by escalating palbociclib concentrations in culture. Using SynergyFinder, we assessed the effect of BLU-222 alone and in combination with palbociclib in the highest single-agent model in vitro. The effectiveness of BLU-222, alone or in combination with palbociclib, was further evaluated in four patient-derived xenograft (PDX) models from HR+/HER2- patients whose tumors progressed after palbociclib plus ET, two TN PDX models, and a TN breast cancer transgenic model driven by tumor-specific forms of cyclin E. Results: The PR HR+/HER2- and TN breast cancer cell lines, unresponsive to palbociclib, exhibited significantly increased sensitivity to BLU-222. The combination of BLU-222 and palbociclib in all four cell lines revealed a robust synergistic effect in PR cells, inducing enhanced apoptosis and cell cycle alterations in G1 or G2/M phases. Treatment with BLU-222 and palbociclib demonstrated substantial antitumor activity in all six PDX models and the cyclin E high TN transgenic models, surpassing the effects of individual treatments in each model. This combination led to lasting tumor regression and extended survival, even after treatment discontinuation. Mechanistically, treatment with BLU-222, alone or combined with palbociclib, induced the expression of p21 and/or p27 in all in vivo models, which we hypothesize sensitizes tumors to palbociclib. In vitro, the CRISPR knockout of p21 or p27 in MCF-7 PR cells abolished the synergistic activity of BLU-222 and palbociclib, confirming the crucial involvement of p21 and p27 in influencing the treatment's effectiveness. Conclusions: We found robust activity of the CDK2 inhibitor, BLU-222 when combined with CDK4/6is in resistant HR+/HER2- and TN breast cancer cell lines and in vivo models. These results support the potential clinical utility of BLU-222 in combination with CDK4/6is for the treatment of both subtypes of breast cancer. Citation Format: Linjie Luo, Yan Wang, Tuyen Bui, Mi Li, Serena Kim, Juliana Navarro-Yepes, Nicole M. Kettner, Debasish Tripathy, Kelly K. Hunt, Kerrie Faia, Khandan Keyomarsi. Anti-tumor activity of CDK2 inhibitor BLU-222 in combination with CDK4/6 inhibitors for overcoming resistance in HR positive and triple negative metastatic breast cancers models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4622.

The CDK4/6 Inhibitor Palbociclib Synergizes with ATRA to Induce Differentiation in AML.

Differentiation therapy based on ATRA almost cured acute promyelocytic leukemia (APL). However, it is disappointing that ATRA is not effective against other acute myeloid leukemia (AML) subtypes. Developing new and effective anti-AML therapies that promote leukemia differentiation is necessary. The CDK4/6-cyclin D pathway is a key initiator of the G1-S phase transition, which determines cell fate. Herein, we investigated whether the CDK4/6 inhibitor palbociclib would synergize with ATRA to promote leukemia differentiation in vitro and in vivo. Our findings revealed that CDK4/6-cyclin D pathway genes were aberrantly expressed in AML, and we observed that palbociclib sensitized AML cells to ATRA-induced morphologic, biochemical, and functional changes indicative of myeloid differentiation. The combination of palbociclib and ATRA attenuated AML cell expansion in vivo. These enhanced differentiation effects may be associated with the regulation of transcription factors, including RARα, E2F1, and STAT1. Overall, our findings demonstrate that CDK4/6 inhibition sensitizes AML cells to ATRA and could guide the development of novel therapeutic strategies for patients with AML.

Combining lapatinib and palbociclib inhibits cell proliferation and invasion via AKT signaling pathway in endocrine-resistant breast cancer cells.

Endocrine therapy plays a critical role in patients with hormone receptor-positive breast cancer. Endocrine-resistant breast cancer cells exhibit more HER2 signaling proteins (pAKT and pERK) and mesenchymal biomarkers than wild-type cell lines. In head and neck squamous cell carcinoma, the combination of lapatinib and palbociclib demonstrated synergistic inhibitory effects on cell proliferation and suppressed ERK1/2 phosphorylation. The combination of lapatinib and palbociclib at half-maximal inhibitory concentrations resulted in an increasing cytotoxic effect on cell proliferation. Furthermore, invasion activity was significantly decreased when combining two drugs at nontoxic concentrations more than either single drug alone did. The combination also remarkably suppressed epithelial-mesenchymal transition transcription factors, such as Snail and pAKT, more than monotherapy. Combining drugs, particularly lapatinib and palbociclib for targeting endocrine-resistant breast cancer cells whose tumors overexpressed HER2 after resistance to hormonal therapy, demonstrated better antiproliferative, anti-invasive effects, and suppression of EMT protein and pAKT than a single drug. These results could be from the interruption of the EMT process via the AKT pathway. Thus, this study provides preliminary data for applying this combination to patients with endocrine-resistant breast cancer in further clinical trials.

Trametinib boosts palbociclib's efficacy in breast cancer via autophagy inhibition.

Breast cancer, a predominant global health issue, requires ongoing exploration of new therapeutic strategies. Palbociclib (PAL), a well-known cyclin-dependent kinase (CDK) inhibitor, plays a critical role in breast cancer treatment. While its efficacy is recognized, the interplay between PAL and cellular autophagy, particularly in the context of the RAF/MEK/ERK signaling pathway, remains insufficiently explored. This study investigates PAL's inhibitory effects on breast cancer using both in vitro (MCF7 and MDA-MB-468 cells) and in vivo (tumor-bearing nude mice) models. Aimed at elucidating the impact of PAL on autophagic processes and exploring the potential of combining it with trametinib (TRA), an MEK inhibitor, our research seeks to address the challenge of PAL-induced drug resistance. Our findings reveal that PAL significantly decreases the viability of MCF7 and MDA-MB-468 cells and reduces tumor size in mice while showing minimal cytotoxicity in MCF10A cells. However, PAL also induces protective autophagy, potentially leading to drug resistance via the RAF/MEK/ERK pathway activation. Introducing TRA effectively neutralized this autophagy, enhancing PAL's anti-tumor efficacy. A combination of PAL and TRA synergistically reduced cell viability and proliferation, and in vivo studies showed notable tumor size reduction. In conclusion, the PAL and TRA combination emerges as a promising strategy for overcoming PAL-induced resistance, offering a new horizon in breast cancer treatment.

The combination of IL-2 nanoparticles and Palbociclib enhances the anti-tumor immune response for colon cancer therapy.

Immunotherapy of tumors plays a pivotal role in the current treatment of cancer. While interleukin 2 (IL-2) demonstrated its efficacy as an immunotherapeutic drug in the early days, its short blood circulation time poses challenges in maintaining effective therapeutic concentrations. Additionally, IL-2's activation of regulatory T cells can counteract its anti-cancer effects. Therefore, the primary goal of this study was to formulate IL-2-carrying nanoparticles via boron-nitrogen coordination between methoxy poly (ethylene glycol) block poly-[(N-2-hydroxyethyl)-aspartamide]phenylboronic acid (mPEG-b-PHEA-PBA, P-PBA) and poly (L-lysine) (PLL). These nanoparticles are intended to be used in combination with CDK4/6 inhibitors to address the short blood circulation time of IL-2, reduce its immunosuppressive effects, and enhance the overall immune response. The envisaged outcome is a sustained and potent therapeutic effect, offering a novel and promising combination therapy strategy for tumor immunotherapy.

Doublet and Triplet Combinations of Eribulin, Fulvestrant, and Palbociclib in Preclinical Breast Cancer Models.

This study investigated in vivo synergism between eribulin and palbociclib in a breast cancer patient-derived xenograft (PDX) model, with expanded scope to include fulvestrant as a third drug. Eribulin plus palbociclib combinations were tested in vitro in six cell lines each of estrogen receptor positive and triple-negative breast cancer, and in vivo in the OD-BRE-0192 PDX model using weekly eribulin plus 5×/week or 7×/week palbociclib (holiday or no-holiday schedules, respectively). When included as a third drug, fulvestrant was dosed weekly. In vitro, combining palbociclib with eribulin led to increased eribulin IC50s in 11 of 12 cell lines, suggesting that the drugs antagonized each other due to mutual exclusion of the mitotic and G1/S cell cycle block points for eribulin and palbociclib. An in vivo study in the OD-BRE-0192 PDX model compared weekly eribulin plus either palbociclib holiday or no-holiday schedules to gauge the importance of post-palbociclib cell cycle synchronization. Results showed no advantage of holiday over no-holiday schedules, arguing that differing pharmacokinetics of the drugs were sufficient to overcome cell cycle-based mechanistic antagonism. In vivo comparisons of doublet and triplet combinations of eribulin, palbociclib, and fulvestrant showed that all three doublets were superior to individual monotherapies, and that the triplet combination was markedly superior to all three doublets, being the only group to show tumor regression in 100% of the mice. Results show complex synergistic interactions between eribulin, fulvestrant, and palbociclib, and point to a particularly robust synergy when combining all three drugs.

A Two-Part Study Evaluating the Combination of Tazemetostat and CPX-351 (Part 1) and Palbociclib with CPX-351 (Part 2) for the Treatment of Relapsed or Refractory Acute Myeloid Leukemia

BACKGROUND AND SIGNIFICANCE Acute myeloid leukemia (AML) is an aggressive cancer of early hematopoietic progenitor cells with only 25-30% of patients (pts) surviving 5 years from diagnosis. For fit pts, conventional chemotherapy with DNA-damaging agents remains the mainstay of treatment. Conventional chemotherapeutic agents cause DNA-damage by targeting cells during DNA replication. Chromatin structure is highly influential in the efficacy of DNA-damaging agents, as areas of compacted chromatin are more resistant to DNA-damaging effects. Areas of DNA marked with histone 3 lysine 27 trimethylation (H3K27me3) are transcriptionally repressed and exhibit reduced accessibility to DNA-damaging agents. Enhancer of Zeste Homolog 2 (EZH2) serves as the catalytic subunit of the polycomb repressive complex 2 which methylates H2K27 to produce a di- or trimethylated state (H3K27me2/3). In preclinical studies, treatment of AML cell lines with the combination of an EZH2 inhibitor (EZH2i) and doxorubicin resulted in an increase in DNA damage and apoptosis compared to those treated with doxorubicin alone. Further, a significant decrease in leukemia burden was seen in mice injected with THP-1 (AML) cells and treated with an EZH2i and doxorubicin and cytarabine compared to doxorubicin and cytarabine alone. This effect was further enhanced by pre-treatment of AML cells with palbociclib (PALB), a CDK4/6 inhibitor, by significantly increasing the number of cells in S phase when exposed to the EZH2i and doxorubicin combination, resulting in an increase in DNA damage and apoptosis compared to cells that were not pre-treated with PALB. These findings were reproduced in in vivo studies with mice injected with the primary AML cells (Porazzi P, et al. Cancer Res., 2021). STUDY DESIGN AND METHODS We will perform a 2-part phase I dose escalation study utilizing EZH2i tazemetostat (TAZ) in combination with CPX-351 induction chemotherapy and of PALB pre-treatment followed by CPX-351 in pts with relapsed or refractory (R/R) AML (NCT05627232). All pts will receive CPX-351 at standard dose on days 1, 3 and 5. Part 1 evaluate the addition of TAZ to CPX-351 via traditional 3+3 design. Pts will be treated with TAZ on days -1 to 6 at a starting dose of 600 mg twice daily to open chromatin concurrent with CPX-351 administration. Part 2 evaluate the pre-treatment with PALB via traditional 3+3 design. Pts will be treated with PALB starting dose of 100 mg daily on days -3 to -1 to induce cell cycle G1. PALB will be held on day 1 to allow cells to then enter S phase prior to administration of CPX-351. ( Figure 1). The study will enroll pts with R/R AML treated at Sidney Kimmel Cancer Center. Pts must be ≥18 years of age with R/R AML (non-acute promyelocytic leukemia) and have received at least 1 prior line of therapy and have adequate performance status and organ function. Pts whose participation would result in a total cumulative dose of daunorubicin greater than 550 mg/m 2 (450 mg/m 2 if they previously received mediastinal radiation) and those with active central nervous system involvement of AML, unstable cardiac disease or other severe concurrent disease will be excluded. The primary endpoints of Parts 1 and 2 will be to determine the maximum tolerated dose of TAZ and of PALB in combination with CPX-351, respectively. Secondary endpoints for Parts 1 and 2 include preliminary assessment of efficacy. Correlative studies to evaluate the on-target effect of TAZ on H3K27me3 and DNA-damage and of PALB on cell cycling will be performed at protocol-specified time points. If these two 2-drug combinations prove to be safe, we will amend the protocol to add Part 3 which will evaluate the safety of the 3-drug combination of pre-treatment with PALB followed by co-treatment with TAZ and CPX-351.

Combination of CDK4/6 Inhibitor Palbociclib and PI3K Inhibitor Idelalisib Synergistically Induces an Anti-Tumor Effect in B-Cell Lymphoma and Overcomes Ibrutinib Resistance

Introduction: Aberrant activity of cyclin-dependent kinases 4/6 (CDK4/6) is frequently detected in B-cell non-Hodgkin's lymphoma (B-NHL), indicating the therapeutic implications of CDK4/6 inhibitors for B-cell malignancies. What's more, the introduction of agents targeting B cell receptor signaling, especially phosphatidylinositol 3-kinase (PI3K) isoform-specific inhibitors, is rapidly changing how B cell malignancies are treated. In this study, we aim to investigate whether the combination of CDK4/6 inhibitor palbociclib (PAL) and PI3Kδ inhibitor idelalisib (IDE) has synergistic anti-tumor effects in B cell lymphoma. Besides, we also evaluated the effect of co-administration PAL and IDE in Bruton's tyrosine kinase inhibitor (BTKi) resistant model. Methods: In vitro, cell viability was analyzed using Cell Titer-Glo ®️ Luminescent Cell Viability Assay. Flow cytometry was used to detect apoptosis and cell cycle arrest induction. Western Blotting analysis was used to detect the changes in essential proteins in related signaling pathways. We also conducted RNA-seq to evaluate the whole transcriptome changes brought by co-treatment with PAL and IDE. The synergistic anti-tumor effects of PAL and IDE were also evaluated in vivo. BTKi secondary resistant cell lines were generated by long-time exposure to ibrutinib and BTK C481S mutation cell line was conducted by lentivirus infection and puromycin selection. Results: Firstly, we analyzed diffuse large cell lymphoma (DLBCL) gene expression profile results from GEO database, and there were more than 50% patients carried cell cycle-related genes alterations, especially for CDKN2A-CDK4/6/CCND1-Rb machinery. Then, it was noteworthy that the high level of CDK4/6 mRNA and protein expression correlated with worse survival of DLBCL patients. Next, we illustrated that pharmacological inhibition of CDK4/6 kinase activity induced inhibition of cell proliferation, tumor cell apoptosis, and cell senescence. Meanwhile, PAL treatment upregulated the expression of PI3Kδ, p-AKT (S473), and p-mTOR (S2448), suggesting compensatory activation of the PI3K-AKT-mTOR signaling pathway. Thus, combination treatment of PAL and PI3K inhibitor IDE was assessed, and this combination synergistically induced a more potent anti-proliferative effect in several B-NHL cell lines, including mantle cell lymphoma cell lines (Z-138 and Jeko-1), DLBCL cell lines (U2932 and OCI-Ly8) and Burkitt lymphoma cell line (Raji). Meanwhile, co-administration treatment could also trigger synergistic anti-tumor activity in BTK inhibitor ibrutinib-resistant HBL-1 BTK C481S and HBL-1 IR cells (long time exposure to ibrutinib). Next, the flow cytometry results indicated that the B-NHL cells became apoptotic after the PAL and IDE treatment. The activation of apoptosis-related proteins (cleaved-caspase3 and cleaved-PARP) and decrease of anti-apoptosis proteins expression (BCL-2, BCL-xL, XIAP, and MCL-1) were induced by combination of CDK4/6 and PI3K inhibitor treatment. The combination of PAL and IDE also substantially increased the cell population of G0/G1 phase and elevated expression of CDK4, CDK6, and CyclinD1. Furthermore, the gene expression profile analysis demonstrated that the mRNA expression level of PLK1 was significantly decreased by co-administration treatment, rather than in PAL or IDE treatment alone. Finally, the combination treatment also showed synergistic anti-tumor activity in multiple tumor-bearing mice models. Conclusion: The combination of CDK4/6 inhibitor palbociclib and PI3K inhibitor idelalisib synergistically induced anti-tumor activity in B-cell lymphoma through downregulation of PLK1 expression, suggested a new combination direction for the treatment of B-NHL and even BTK inhibitor-resistant patients.