Abemaciclib Research Articles

Neutrophil-targeted liposomal platform: A shift in novel approach for early detection and treatment of cancer metastasis

Tumor metastasis is responsible for 90 % of cancer-associated deaths, and its early detection may decrease the likelihood of mortality. Studies have demonstrated that metastasis results from the interaction between “seeds” (tumor cells) and “soil” (pre-metastatic niche, PMN). As the first and most abundant immune cells to be recruited to PMN, neutrophils play a key role in the ultimate formation of metastatic foci through mechanisms such as supporting tumor cell growth, promoting angiogenesis, and shaping an immune-suppressive microenvironment. In this study, two distinct types of sialic acid (SA)-modified liposomes were prepared to target and regulate pro-metastatic neutrophils through the l-selectin receptor. One of these liposomes, named ICG@SAL, was used to encapsulate indocyanine green (ICG) and was specifically designed for the early detection of cancer metastasis. The other liposome, referred to as ABE/Cur@SAL, co-loaded abemaciclib (ABE) and curcumin (Cur), with the intention of suppressing the progression of metastatic tumor. Fluorescence imaging results from the mouse spontaneous metastasis model indicated that ICG@SAL demonstrated faster targeting and stronger accumulation in the metastatic organs than unmodified ICG liposomes (ICG@CL). This suggested that ICG@SAL could detect tumor metastasis at an early stage. The therapy with co-loaded liposomes in the mouse experimental lung metastasis model indicated that ABE/Cur@SAL could inhibit regulatory T (Treg) cell proliferation, enhance effector T cell activity and reduce tumorigenic factor release, implying that ABE/Cur@SAL could inhibit tumor metastasis. Overall, our work provided a sensitive and convenient approach to early diagnosis and treatment of tumor metastasis. ICG@SAL could be employed for the early detection of tumor metastasis, while ABE/Cur@SAL could be used to inhibit the development of tumor metastasis when early metastasis was identified.

Radiation hepatitis after postmastectomy radiation therapy for early breast cancer: difficult to differentiate from drug-induced liver injury caused by abemaciclib.

Abemaciclib (ABM) is recommended for adjuvant endocrine therapy in hormone receptor-positive, human epidermal growth factor receptor type 2-negative early breast cancer (EBC) patients at high risk of recurrence. Here, we present a case of radiation hepatitis challenging to differentiate from drug-induced liver injury during ABM treatment. The patient, a woman in her 40s, underwent right mastectomy, axillary dissection, and postmastectomy radiation therapy (PMRT) after neoadjuvant chemotherapy for EBC. Subsequently, she received ABM as adjuvant endocrine therapy. Despite suspending ABM due to Grade 3 leukopenia, she developed Grade 3 hepatic dysfunction upon cessation. Based on the dynamic contrast-enhanced computed tomography, we diagnosed the cause of liver dysfunction as radiation hepatitis. Spontaneous improvement allowed us to resume ABM treatment. Clinicians may need to consider radiation hepatitis as a potential cause of hepatic dysfunction in patients who underwent PMRT, along with drug-induced liver injury.

Effect of abemaciclib and curcumin administration on sex hormones, reproductive functions, and oxidative DNA expression in rats

ABSTRACT This study investigated whether abemaciclib (ABE) administration had any adverse effects on ovarian and sex hormones in female rats, and the protective effect of curcumin. Forty female rats were equally divided into the sham control, DMSO, curcumin (CMN), ABE, and ABE+CMN groups. Pharmaceuticals were administered by gavage daily for 28 days. Serum sex hormones were measured in an autoanalyzer operating with a microparticle immunoassay method. In addition, histopathological examination and 8-OHdG expression were performed on the ovarian tissue. Progesterone and testosterone levels were significantly decreased, while estradiol levels were significantly increased, in the ABE group compared to the sham and DMSO groups. In addition, there were significant differences in sex hormone levels in the CMN and/or CMN+ABE groups compared to the ABE group. There was decreased expression of 8-OHdG in the ABE+CMN group compared to the ABE or CMN only groups. This study exhibited that ABE administration can adversely affect functions and histology of the ovarian tissue, but CMN therapy may be protective against the adverse effects on ovarian in ABE-induced rats.

CYCLONE 2: A phase 3 study of abemaciclib with abiraterone in patients with metastatic castration-resistant prostate cancer.

5001 Background: Oncogenic addiction to androgen receptor (AR) signaling drives mCRPC progression, highlighting the unmet need for novel treatment strategies to maximize AR-directed therapy. Preclinical evidence suggests a key role for CDK4/6 in sustained AR signaling, uncontrolled proliferation, and hormonal resistance in prostate cancer. Abemaciclib (ABEMA) is a potent CDK4/6 oral inhibitor that significantly augments the efficacy of endocrine therapy in hormonally driven (ER+) high-risk early-stage and metastatic breast cancer. ABEMA also showed single-agent activity in heavily pretreated mCRPC. Here, we report the primary results of CYCLONE 2, a Phase 3 study of ABEMA plus abiraterone (ABI) in pts with 1L mCRPC. Methods: CYCLONE 2 was a seamless Phase 2/3 adaptive trial with a dose-finding safety lead-in. Randomization to the ABEMA or placebo (PBO) plus ABI and predniso(lo)ne was stratified by prior docetaxel receipt for mHSPC, measurable disease, and radiographic progression at study entry. Primary endpoint was investigator-assessed radiographic progression-free survival (rPFS) per RECIST v1.1 and PCWG3. The study was powered at ~90%, assuming a HR of 0.55 for rPFS, at a cumulative 2-sided alpha level of 0.05. Results: Between Nov 2018 and Jul 2022, 393 pts were randomized. Baseline characteristics were balanced across arms. Primary endpoint of rPFS was not met (HR 0.829; 95% CI, 0.619–1.111; p=0.2123), medians were 21.96 months for the ABEMA plus ABI group vs 20.28 months for the PBO plus ABI group. rPFS by blinded independent central review was consistent with investigator assessment (HR 0.842; 95% CI, 0.611–1.160). OS was a gated secondary endpoint and not inferentially tested (HR 0.927; 95% CI, 0.669–1.285; 38.9% maturity). Other secondary endpoints included time to PSA progression (HR 0.637; 95% CI, 0.474–0.856), time to symptomatic progression (HR 0.768; 95% CI, 0.522–1.131), and time to worst pain progression (HR 0.935; 95% CI 0.665–1.314). The most common grade ≥3 adverse events (AEs) reported in the ABEMA plus ABI group were anemia (13.6% vs 4.3% in the PBO plus ABI group), neutropenia (12.6% vs 0.5%) and ALT increased (8.7% vs 6.5%). Discontinuations of all study treatments due to AEs were 13.1% vs 4.3% in ABEMA plus ABI vs PBO plus ABI groups, while discontinuations of ABEMA or PBO alone due to AEs were 5.8% vs 1.6%, respectively. Conclusions: In patients with mCRPC, adding abemaciclib to abiraterone did not significantly increase rPFS. While no OS detriment was observed, secondary endpoints were not meaningfully improved. Overall, the combination was well tolerated, and safety was consistent with the known profiles of the individual medicines. Clinical trial information: NCT03706365 Clinical trial information: NCT03706365 .

Real-world treatment outcomes in patients with HR+ HER2- advanced breast cancer treated with CDK4/6 inhibitors and endocrine therapy.

1067 Background: The addition of cyclin-dependent kinases 4 and 6 inhibitors (CDK4/6i) to endocrine therapy (ET) improves progression-free (PFS) and overall survival (OS) in hormone receptor-positive, HER2-negative advanced breast cancer (HR+/HER2- ABC) in 1st and 2nd line setting. The international guidelines advise using 1st line CDK4/6i; however, its superiority over 2nd line use is debatable. Methods: We retrospectively analyzed clinical data of HR+/HER2- ABC pts administered palbociclib (PAL), ribociclib (RIB) or abemaciclib (ABM) added to either 1st or 2nd line ET. Results: A total of 1511 pts (PAL=507; RIB=724; ABM=280) from 11 cancer Polish centers treated between Sep 2017 and Dec 2023. Median follow-up was 29.6 (95%CI 28.2 to 30.9) months (m). Mean age was 62.6±11.9, 58.9±12.2 and 61.4±10.8 years in PAL, RIB and ABM, respectively. 815 patients (53.9%) had visceral and 1109 (73.4%) bone metastases. 1254 pts (83%) received 1st line CDK4/6i, in 841 (67%) combined with aromatase inhibitor (AI) and in 413 (33%) with fulvestrant (FUL). Second-line CDK4/6i was used in 257 pts (17%); 59 (23%) and 198 (67%) with AI and FUL, respectively. There was no difference in PFS, PFS2, and OS between three CDK4/6i in combination with AIs in 1st and 2nd line setting. Median PFS (95%CI) for 1st line AI with PAL, RIB, ABM were 29.0 (21.6-37.0), 32.0 (24.5-36.9), not reached (N/R) (21.9-N/R) m; PFS2: 37.0 (28.8-N/R), 33.0 (29.5-40.2), N/R (28.9-N/R); OS: 48.9 (42.9-N/R), 48.6 (41.9-N/R), N/R (36.7-N/R). Median PFS (95%CI) for 2nd line AI with PAL, RIB, ABM were 11.9 (9.49-N/R), 10.8 (8.27-N/R), 11.0 (6.43-N/R); PFS2: 22.7 (16.8-N/R), 32.3 (24.9-N/R), 31.0 (13.2-N/R); OS: 27.4 (24.4-N/R), 36.7 (30.1-N/R), 45.5 (29.0-N/R) (no statistical significance). In contrast, RIB+FUL was superior to PAL+FUL and ABM+FUL in both lines (Table). The safety profile was concordant with the reported data for ET + CDK4/6i. Conclusions: Identifying predictive factors of response is essential for the rational use of CDK4/6i and ET in HR+/HER2- ABC. [Table: see text]

Innovation of the first-line strategy optimized as abemaciclib with endocrine therapy based on the ESR1mutation of ctDNA for patients with HR-positive HER2-negative advanced metastatic breast cancer (JBCRG-M08; AMBER study).

TPS1134 Background: Aromatase inhibitor (AI) + CDK4/6 inhibitor (CDK4/6i) has been established as a standard of care of 1st line treatment for hormone receptor (HR)-positive/HER2-negative advanced metastatic breast cancer (AMBC). ESR1 mutations are considered to be one of the causes of acquiring resistance against the AI +CDK4/6i. PADA-1 trial showed that replacing AI with fulvestrant (FUL) as a partner of palbociclib (PAL) at occurrence of some ESR1 mutations improved progression-free survival (PFS) and PFS2, suggesting PAL should be used based on the strategy of selecting endocrine agents according to ESR1 mutation status by ctDNA analysis. On the other hand, we don’t know if this strategy is effective in the case of abemaciclib (ABM), another CDK4/6i established as the standard of care for AMBC. We are conducting a study to make evidence on this clinical question. Methods: This multicenter, single-arm phase II study is designed to evaluate the efficacy and safety of the strategy to replace AI with FUL for detectable ESR1 mutations in combination with ABM. Key eligibility criteria include patients receiving AI+ABM for at least 6 months as first-line treatment for HR-positive/ HER2-negative AMBC without progressive disease (PD). While continuing AI+ABM, ctDNA analysis will be performed at approximately 3, 9, 15 months from enrollment. If ESR1 mutation is identified at any point and non-PD is confirmed by CT, FUL+ABM will be initiated instead of AI+ABM. In patients with ESR1 mutations completely cleared by ctDNA analysis 6 months after the start of FUL+ABM, AI+ABM will be resumed (Re-AI+ABM arm); the Re-AI+ABM arm is intended to investigate whether the discontinuation of FUL will allow clones with ESR1 mutations to proliferate again. Primary endpoint is 2-year PFS rate in full analysis set. Key secondary endpoints include 2-year PFS rate by treatment sequences, and rate of disappearance of ESR1mutations in ctDNA with FUL+ABM. Plasma-SeqSensei Breast Cancer IVD Kit, which can simultaneously detect mutations in a wide range of six genes including ESR1, as well as PIK3CA, AKT1, ERBB2, KRAS, and TP53, is used for ctDNA analysis in this study. Based on PFS data in MONARCH3 study, the threshold and expected value of the 2-year PFS rate were estimated to be 45% and 55%, respectively, and target sample size was calculated as 160 patients. Patient enrollment started in December 2022 and run through December 2024; as of December 2023, 54 patients have been enrolled. Clinical trial information: 051220133.

Abstract PS17-06: A phase I trial of the PI3K inhibitor (PI3Ki) copanlisib and fulvestrant in combination with continuous or intermittent abemaciclib in patients with estrogen receptor-positive (ER+), HER2-negative (HER2-) metastatic breast cancer

Abstract Background: Activation of the phosphoinositide 3-kinase (PI3K) pathway is a prominent resistance mechanism to endocrine therapy and CDK4/6 inhibition (CDK4/6i) in ER+, HER2- breast cancer. There is reciprocal crosstalk between PI3K and cell cycle regulatory pathways. Triplet therapy that targets ER, CDK4/6, and PI3K prevents or delays disease progression in preclinical models of ER+, HER2- breast cancer. However, the toxicities of triplet therapy hinder its clinical development. Copanlisib (COP) is an intravenous (IV) PI3Ki with potent activity against α and δ isoforms. Intermittent high-dose PI3Ki is expected to be less toxic and more effective than continuous daily dosing. We set out to determine the recommended phase 2 dose (RP2D) for the COP/Fulvestrant (FUL)/Abemaciclib (ABE) combination. Methods: Eligible patients (pts) included men or women with ER+, HER2- metastatic breast cancer (MBC), with no more than 1 prior chemotherapy in the metastatic setting, and no limits on prior endocrine or targeted therapy. Prior FUL, CDK4/6i and PI3K/mTORi were allowed. Pts with HbA1c >8.5% were excluded. Pts received FUL 500 mg IM standard dosing and COP/ABE at assigned doses. Premenopausal women also received a GnRH agonist. Dose-limiting toxicity (DLT) was assessed during the first 28-day cycle. Adverse events (AEs) were graded according to NCI-CTCAE v5.0. Dose escalation/de-escalation was based on continual reassessment (CRM) and the RP2D was defined as the dose with the highest probability of the DLT rate within the acceptable 25~35%. Results: Between June 2020 and June 2023, 24 pts with ER+, HER2- MBC were enrolled. Table 1 shows the dose levels (DLs) and DLTs. The first 10 pts were enrolled to Part A on two consecutive DLs of COP (DL1: 45 mg IV D1 and D15, n=7; DL2: 45 mg IV D1, D8, and D15, n=3), with ABE fixed at 100 mg PO BID continuously. DL2a exceeded the maximum tolerated dose (MTD). DL1a was tolerable based on Cycle 1 AEs. However, during subsequent cycles, only 1 of the 7 pts in DL1a maintained the intended dose of ABE due to neutropenia, others reduced ABE to 50mg bid (n=5) or discontinued (n=1). This triggered a protocol amendment, adding Part B with ABE administered 5 days on and 2 days off (5-on/2-off) intermittent schedule. 14 pts were enrolled to Part B in 2 consecutive DLs of COP (DL1b: n=7; DL2b: n=7), the same as in Part A. ABE was fixed at 100 mg PO Bid 5-on/2-off. DL2b exceeded the MTD. DL1b was tolerable based on Cycle 1 AEs. In addition, in subsequent cycles, only 1 of 7 pts on DL1b required dose reduction of ABE to 50mg bid. RP2D is therefore defined as DL1b. Grade (G) 4 AEs were rare. The most common all cycle G3 AEs included transient hypertension (45%), rash (30%), anemia (25%), neutropenia (25%), and AST elevation (20%). As of 6/14/2023, 22 pts, with a median of 1 prior metastatic regimen (range 0-5), prior CDK4/6i in 18 (82%), liver mets in 8 (36%), and PIK3CA mutation in 8 (50%) of 16 pts with known mutation status, were evaluable for response. There were 5 partial responses and 3 stable diseases lasting for ≥24 weeks. Clinical benefit rate was 36.4% (8/22, 95%CI: 17.19% ~ 59.34%). Responses were observed in pts regardless of prior CDK4/6i, FUL, or PIK3CA mutation. Conclusion: COP/FUL/intermittent ABE can be safely administered with fair overall tolerability. Preliminary anti-tumor activity was observed, which will be further examined in the randomized phase II trial (NCT 03939897). Table 1 Dose-limiting Toxicities by Dose Level Citation Format: Cynthia Ma, Jingqin Luo, Jessica Moss, Maryann Kwa, Ritesh Parajuli, Katia Khoury, Emily Douglas, Ashley Frith, Caron Rigden, Foluso Ademuyiwa, Shana Thomas, Brittney Haas, Gerburg Wulf, Claire Dees, Rabih Said. A phase I trial of the PI3K inhibitor (PI3Ki) copanlisib and fulvestrant in combination with continuous or intermittent abemaciclib in patients with estrogen receptor-positive (ER+), HER2-negative (HER2-) metastatic breast cancer [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 PS17-06.

Abstract PO2-01-09: Patient preferences for CDK4/6 inhibitor treatments in HR+/HER2− early breast cancer: a discrete choice survey study

Abstract Background: Patients (pts) with stage II/III HR+/HER2− early breast cancer (EBC) are at risk of recurrence that persists over years. The addition of a CDK4/6 inhibitor (CDK4/6i) to adjuvant endocrine therapy (ET) was investigated in monarchE, evaluating abemaciclib (ABE) in lymph node (LN)+ high-risk pts, and NATALEE, using ribociclib (RIB) in stage II/III disease, including pts with N0 disease. ABE was FDA approved in this indication in 2021, while NATALEE recently reported statistically significant iDFS results. Both efficacy and tolerability are relevant for pts treated in a curative setting. This prospective study evaluated the extent pts with EBC value different treatment (tx) attributes and how these may translate into preferences between the two CDK4/6i in the US. Methods: A web-based discrete choice experiment survey was conducted among pts with EBC between Jan and May 2023 before NATALEE results were available. Eligible pts were adult women in a US clinical practice setting with self-reported stage II/III HR+/HER2− EBC +/- prior chemotherapy receiving only adjuvant ET at the time of survey, who completed curative surgery 1-3 years ago. Pts selected the scenario that best reflected their preferences from a series of choice cards, each displaying a pair of hypothetical tx profiles. A total of 8 attributes related to efficacy (5-year iDFS), adverse events (AEs), monitoring requirements, tx duration, and schedule were included (Table 1). Attributes were included based on an initial pilot qualitative assessment that selected efficacy and safety attributes most relevant to pts, clinical input, and differentiating features between CDK4/6i. A conditional logit regression model was used to estimate preference weights and relative importance (RI) of each attribute. Utility scores, summarizing overall preference for CDK4/6i tx profiles, were estimated from the model, and various scenarios were tested. Subgroup analyses by menopausal status and BC stage will be presented. Results: 409 pts participated in the survey (median age, 53 years; White/Black/other race, 59%/23%/18%; BC stage II/III, 48%/52%; employed, 38%). Pt preferences for attributes that significantly impacted tx decision, in order of high to low RI, were higher efficacy (iDFS), lower risk of diarrhea, lower risk of fatigue, shorter tx duration, and lower risk of venous thromboembolic events. Attributes based on monitoring or schedule, including number of blood tests, number of EKGs, and tx schedule, did not affect tx choice (Table 2). Overall utility scores were consistently higher for reconstructed tx profiles that resembled RIB features, including under conservative scenarios where efficacy of RIB was assumed to be equivalent or lower than that of ABE. Conclusions: This study showed that, driven by strong preference for lower risk of AEs, pts with HR+/HER2− EBC prefer tx profiles that more closely resemble the clinical experience of receiving RIB. These pt preferences are important for shared decision making when discussing the addition of a CDK4/6i to adjuvant tx for eligible pts with HR+/HER2− EBC. Discrete Choice Experiment Attributes and Levels Estimated Preference Weight and Relative Importance Citation Format: Erica Mayer, Mary Lou Smith, Annie Guerin, Dominick Latremouille-Viau, Nisha C. Hazra, Yan Meng, Wendi Qu, Remi Bellefleur, Vaidyanathan Ganapathy, Liz Santarsiero, Robert Morlock, Maryam Lustberg. Patient preferences for CDK4/6 inhibitor treatments in HR+/HER2− early breast cancer: a discrete choice survey 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 PO2-01-09.

Abstract PO4-05-07: Differential dynamics of fragmentomic and epigenetic circulating tumor DNA (ctDNA) features in first-line Palbociclib and Ribociclib treatment for Hormone Receptor (HR) positive, HER2 negative metastatic breast cancer (MBC)

Abstract Background: Cyclin-dependent kinase inhibitors (CDK4/6i) in combination with endocrine therapy (ET) represent the cornerstone for the management of HR positive, HER2 negative MBC. However, the lack of prospective cohorts comparing the distinctions among palbociclib (PAL), ribociclib (RIB) and abemaciclib (ABE) poses a significant clinical knowledge gap. The aim of this ancillary analysis was to explore the differential clinical impact of CDK4/6i by leveraging new ctDNA biomarkers in a prospective clinical study. Methods: A total of 114 patients (pts) with HR positive, HER2 negative MBC were prospectively enrolled in the multicenter MAGNETIC.1 study (CRO-2018-56) from January 2018 to January 2023. At baseline (BL) and every 3 months (mos.), ctDNA samples were collected concurrently with radiological restaging. The samples were then analyzed through methylation-specific (MS) droplet digital PCR (ddPCR), ddPCR fragmentomics, and next generation sequencing. Matched pairs of variations were tested through Wilcoxon signed rank test, and survival was analyzed by log-rank test. Results: Out of the 114 pts enrolled, 59 received PAL, 48 RIB, and 16 ABE. In the de novo subgroup, 51.4 % of pts were treated with PAL, 42.9% with RIB, and 5.7% with ABE. Among the pts who received PAL, 7 harbored an ESR1 mutation at BL (D538G: 2, H377R: 1, Y537N: 1, Y537S: 3). Additionally,12 pts had PIK3CA mutations, and 2 pts had AKT1 mutations. In the RIB group, 5 and 2 pts, respectively, had a PIK3CA- and AKT-mutated MBC, while no ESR1 mutations were detected. When comparing matched pairs of variations, it was found that at BL, at first radiological restaging (T1), and at 6 mos. after initiation of CDK4/6i (T2), only PAL showed significantly higher levels of promoter A and B methylation (promA and promB) at T1 (P = 0.0005 and P = 0.0056, respectively for promA and promB), A significant decrease in promA and promB levels was detected at T2 for PAL (P = 0.0005 and P < 0.0001 respectively for promA and promB) but not for RIB. Both PAL and RIB demonstrated a significant decrease in ctDNA short fragments at T1 (P = 0.0263 for PAL and P = 0.0001 for RIB), However, PAL showed a significant rebound at T2, with an increase in 80% of samples (P = 0.0014). The same was not seen with RIB. After a median follow-up of 34.8 mos., there were no significant differences between PAL and RIB in terms of PFS (P= 0.2573) and OS (P= 0.3783). The PFS rates at 12 and 24 mos. were 69% and 48% for PAL, and 76% and 64% for RIB. The OS rates at 12 and 24 mos. were 94% and 84% for PAL, compared to 97% and 82% of RIB, respectively. Conclusions This analysis of MAGNETIC.1 highlighted significant differences in ctDNA biomarkers between palbociclib and ribociclib, suggesting their potential impact on the development of endocrine resistance. Further biomarker-driven clinical trials leveraging this concept are needed to refine the sequencing algorithms for CDK4/6i. Citation Format: Claudia Noto, Linda Cucciniello, Elisabetta Molteni, Silvia Bolzonello, Alessandra Franzoni, Lucia Da Ros, Silvia Buriolla, Arianna Dri, Lorenzo Foffano, Simon Spazzapan, Stefania Russo, Brenno Pastò, Giulia Cudia, Giada Targato, Serena Della Rossa, Marta Bonotto, Alessandro Marco Minisini, Giuseppe Damante, Barbara Belletti, Lorenzo Gerratana, Fabio Puglisi. Differential dynamics of fragmentomic and epigenetic circulating tumor DNA (ctDNA) features in first-line Palbociclib and Ribociclib treatment for Hormone Receptor (HR) positive, HER2 negative metastatic breast cancer (MBC) [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 PO4-05-07.

Abstract PO3-19-12: Evaluating the impact of ePRO-based follow-up system (Pink Ribbon Diary) on quality of life and treatment adherence in patients with breast cancer receiving CDK4/6 inhibitors: a single center, randomized controlled study (JPRO-B)

Abstract Background: Treatment-related toxicities (TRT) may decrease patient’s quality of life (QOL) and may result in a decrease of adherence to the therapy. Cyclin-dependent kinase 4/6 inhibitors (CDK4/6is), such as palbociclib (PAL) and abemaciclib (ABM) improved patients’ outcomes with estrogen receptor-positive (ER+) HER2 negative (HER2-) advanced breast cancer (ABC), however, majority of patients who undergo CDK4/6i therapy experience ≥ Grade 2 TRTs, such as hematological abnormalities, gastrointestinal disorders or general fatigue. While prompt management of those TRTs is mandatory to prevent patients from discontinuing the therapy, real-time monitoring of TRTs has been warranted. Recently, efforts have been made to monitor symptoms using electronic patient-reported outcome (ePRO) to detect side effects as early as possible and to provide timely support. However, the efficacy of ePRO in daily clinical practice for those receiving CDK4/6is is still unclear. In addition, the researches in the field of ePRO to date have only focused on drugs administered intravenously in hospitals, where patients’ adherence has no clinical importance. Study design and eligibility criteria: This randomized, open-label, controlled phase 2 trial is designed to assess the efficacy of a new proprietary ePRO system, the Pink Ribbon Diary (PRD), compared with placebo (usual care without the ePRO system) in breast cancer patients with ER+HER2-ABC receiving oral CDK4/6i-based therapy aged ≥ 20 years. All eligible patients who complete training on how to use ePRO system are randomly allocated to either arm A using ePRO system or arm B receiving usual care (1:1). Participants in the arm A are required to record medication taken and physical condition every day for 3 months, and report adverse events using PRO-CTCAETM once a week. Patients in the arm B are also asked to answer to questions concerning adverse events using PRO-CTCAETM at monthly hospital visit for 3 months. All participants are asked to respond to the EORTC QLQ-C30 at their monthly visit and a questionnaire survey on adherence before the study and after completion of the study. Participants in the arm A and healthcare providers, will answer the questionnaire about the feeling of using the PRD. Primary endpoint is the change in global health status/QOL (EORTC QLQ-C30) at 3 months from baseline. Secondary endpoints are RDI (relative dose intensity), other domains of EORTC QLQ-C30, number of days missed medication, PDC (proportion of days covered), survey of medication compliance awareness using MMAS-8 (Morisky Medication Adherence Scale), questionnaire on use of PRD, and comparison between two groups of occurrence of adverse events and incidence of missed medication. Study objective: To assess the clinical efficacy of PRD in patients with ER+HER2-ABC undergoing CDK4/6i-based therapy. Statistical methods: For analysis of QOL, the primary endpoint, the differences in global health status/QOL (EORTC QLQ-C30) before and after the study will be compared between the two groups using the t-test. Present accrual and target accrual: The study was approved by institutional review board in December 2022, and is open for enrollment. The target sample size is 70. The study is on-going and 22 patients have been accrued to date. Trial registration numbers: Japan Registry of Clinical Trials (jRCT) jRCT1030220626 (https://jrct.niph.go.jp/re/reports/detail/30182). Citation Format: Rie Ozeki, Hideo Shimizu, Kotaro Iijima, Misato Okazaki, Junichiro Watanabe, Mitsue Saito. Evaluating the impact of ePRO-based follow-up system (Pink Ribbon Diary) on quality of life and treatment adherence in patients with breast cancer receiving CDK4/6 inhibitors: a single center, randomized controlled study (JPRO-B) [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 PO3-19-12.

Combination therapy application of Abemaciclib with Doxorubicin in triple negative breast cancer cell line MDA-MB-231.

Due to lack of clinical biomarkers, Triple Negative Breast Cancer (TNBC) is more likely to have spread to other tissues at time of diagnosis and therapy planning generally involves use of cytotoxic chemotherapy agents, such as Doxorubicin. We aimed to investigate possible advantages of using combination strategy using Doxorubicin alongside Abemaciclib. After determining the IC50 values for Doxorubicin (DOX) and Abemaciclib (ABE); CompuSyn and ComBenefit software were used to reveal the effect resulting from the combination of two drugs. Following the determined effect, cell death was revealed by fluorescence microscopy and a colony forming assay was performed to see the potential of even a single cancer cell with adhesive character to survive over time and form a clone of itself. Detection of changing antioxidant activity following DOX, ABE and DOX+ABE combination therapy in MDAMB231 cells was determined by measuring MDA, SOD and GSH activities. The expression of Cleaved Caspase 3, PARP, Cleaved PARP, Cdk2 and Bax, which changed as a result of DOX, ABE and DOX+ABE application, was shown by Western Blotting.Cyclin-dependent kinase inhibitors appear as promising agents in therapy planning for breast cancer due to their prominent role in cell cycle regulation, where the number of studies interrogating its efficiency in the treatment of cancer such as TNBC is limited. For this reason, in this study, we aimed to determine the impact of the combined use of the CDK4/6 inhibitors ABE and DOX on the cytotoxicity, apoptotic homeostasis, alterations in antioxidative mechanisms, and the molecular pathways that they utilize. Our results showed that when used in combination, Doxorubicin and Abemaciclib showed a synergistic effect on TNBC cell line MDA-MB-231.

Abemaciclib pharmacology and interactions in the treatment of HR+/HER2- breast cancer: a critical review.

Abemaciclib (ABE) in combination with endocrine therapy represents the mainstay treatment for either endocrine-resistant metastatic or high-risk early-stage HR+/HER2- breast cancer patients. Hence, an adequate knowledge of this agent pharmacodynamic, pharmacokinetic, and of its drug-drug interactions (DDIs) is crucial for an optimal patients management. Additionally, ABE interference with food and complementary/alternative medicines should be taken into account in the clinical practice. Several online tools allow to freely check DDIs and can be easily consulted before prescribing ABE. According to one of this instruments, ABE display the lowest number of interactions among the available cyclin-dependent kinase 4/6 inhibitors. Still, clinicians should be aware that online tools cannot replace the technical datasheet of the drug as well as a comprehensive clinical assessment for each patient. Here we critically review the main pharmacological features of ABE, then focusing on its potential interactions with drugs, food, and alternative medicine, in order to provide a guide for its optimal use in the treatment of HR+/HER2- breast cancer patients.

The cyclin-dependent kinase inhibitor abemaciclib-induced hepatotoxicity: Insight on the molecular mechanisms in HepG2/THP-1 co-culture model

Drug-induced liver injury (DILI) is one of the widespread causes of liver injury and immune system plays important role. Abemaciclib (ABE) is a cyclin-dependent kinase inhibitor used as monotherapy or combination therapy in the treatment of breast cancer. Like other kinase inhibitors, the underlying mechanisms of ABE-induced hepatotoxicity are not completely known yet. In the current study, hepatotoxicity of ABE was evaluated with HepG2/THP-1 co-culture model which has been developed in recent years for the evaluation of DILI potential. Following ABE treatment, oxidative stress, mitochondrial damage, cytokine secretion levels, apoptotic/necrotic cell death were determined. According to our results, ROS production along with GSH depletion was observed in HepG2 cells after ABE treatment. ABE promoted secretion of pro-inflammatory mediators (TNF-α and MCP-1) and declined anti-inflammatory cytokine IL-10 release. Besides, NFKβ and JNK1 protein expression levels increased following ABE treatment. ABE enhanced intracellular calcium levels, induced early apoptotic and necrotic cell deaths in HepG2 cells. Furthermore, the changes in some mitochondrial parameters including a reducement in intracellular ATP levels and complex V activity; hyperpolarized mitochondrial membrane potential and enhanced mitochondrial ROS levels were observed, whereas mitochondrial mass did not show any differences after ABE treatments. Therefore, ABE-induced hepatotoxic effects is probably via oxidative stress, inflammatory response and necrotic cell death rather than direct mitochondrial toxicity. In conclusion; the study makes a significant contribution to strengthening the infrastructure we have on in vitro toxicity mechanism evaluations, which are the basis of preclinical toxicity studies.

Potential degradation products of abemaciclib: Identification and structural characterization employing LC-Q/TOF-MS and NMR including mechanistic explanation

Degradation products are the potential drug impurities that can be generated during transport and storage of pharmaceuticals. Before this study, degradation chemistry and potential degradation products of abemaciclib (ABM) were unknown. Moreover, no stability-indicating analytical method was available that can be used to analyse ABM in presence of its degradation products. In this study, stress testing on ABM was carried out under oxidative, thermal, photolytic (UV & visible), and hydrolytic (acid, alkaline, and neutral) degradation conditions. The study revealed that ABM is susceptible to photolytic, oxidative, and thermal stress leading to the formation of five degradation products (DPs). ABM and its degradation products were chromatographically separated employing a developed RP-HPLC-based stability-indicating analytical method. The method was transferred to an LC-Q-TOF system for further analysis. To elucidate the structure of degradation products, fragmentation pathway of ABM was initially established through high-resolution mass spectrometry (HRMS). Subsequently, mass fragmentation pathways of all the DPs have been established through HRMS and MSn based analysis. The major degradation product was isolated and fully characterized using atmospheric chemical ionization-mass spectrometry and nuclear magnetic resonance techniques. ABM showed extensive degradation under oxidative and photolytic systems. Therefore, special care may be sought during storage and transport of ABM or its formulations to avoid photolytic and oxidative stress exposure to the drug. Lastly, in silico toxicity of the characterized degradation products was assessed employing ProTox ІІ online web predictor freeware in which some of them were found to have the potential of hepatotoxicity, immunogenicity and mutagenicity.

Effect of curcumin on lipid profile, fibrosis, and apoptosis in liver tissue in abemaciclib-administered rats

Abemaciclib (ABEM) is an important antitumor agent for breast cancer treatment. However, the side-effects of ABEM are unclear in the liver. This study investigated the protective effect of curcumin (CURC) on liver damage caused by ABEM. The rats were divided into five groups with eight animals in each group; Control, DMSO (150 µL for per rats), CURC, 30 mg/kg/day), ABE (26 mg/kg/day), and ABE + CURC (26 mg/kg/day ABE, 30 mg/kg/day) groups. Injections were administered daily for 28 days. The levels of AST, LDH, HDL, LDL, triglyceride, and total cholesterol in serum, and hepatic tissue fibrosis, caspase-3, Bax, and TNF-α expression were higher in the ABE group compared to the control group (p < 0.05). Also, these parameters in the ABEM + CURC group were lower than in the ABE group (p < 0.05). The results showed that ABE administration could cause liver damage and increase fibrosis in the liver. In addition, it was shown that co-administration of CURC with ABE could suppress the levels of AST, LDH, HDL, LDL, triglyceride, and total cholesterol in serum, and fibrosis, caspase-3, Bax, and TNF-α expressions in the liver. These data are the first in the literature. Therefore, the administration of CURC following ABE may be a therapeutic agent in preventing liver damage.

Abstract P5-02-23: Association of Neutrophil-to-Lymphocyte Ratio and Absolute Lymphocyte Count with Clinical Outcomes for Patients with Advanced Breast Cancer in the MONARCH 2 Trial

Abstract Background: Pretreatment neutrophil-to-lymphocyte ratio (NLR) and absolute lymphocyte count (ALC) are putative prognostic factors in patients with advanced breast cancer (ABC). Little information is available on the prognostic value of these immune status markers in patients treated with abemaciclib (ABE). In this study, we investigated the relationship between baseline NLR and ALC and clinical outcomes using data from the phase 3 MONARCH 2 (M2) trial. Methods: The M2 study compared ABE/fulvestrant to placebo (PBO)/fulvestrant in patients with estrogen-receptor positive, human epidermal growth factor receptor 2-negative ABC that had progressed on prior endocrine therapy. The current post hoc analyses used baseline laboratory data and outcome data from the June 20, 2019, cutoff date (median follow-up: 47.7 months). For both baseline NLR and baseline ALC, patients were divided into high and low categories, defined by a cutoff of 2.5 for NLR and 1.5 × 109/L for ALC. The association of baseline NLR and ALC with investigator-assessed progression-free survival (PFS) and overall survival (OS) was explored using Cox models stratified by treatment and described using Kaplan-Meier estimates. After assessing the prognostic value of baseline NLR and ALC for PFS and OS using a univariate analysis, a multivariate model was used to determine whether baseline NLR and ALC were independently prognostic considering additional baseline and disease characteristic factors. Results: Data were available for 426 and 219 patients in the ABE and PBO arms, respectively. Median baseline NLR was 2.5 and 2.4 in the ABE and PBO arms, respectively. Median baseline ALC was 1.4 × 109/L in both arms. The numbers of patients categorized into the high and low categories were well balanced for analysis of both NLR and ALC. Univariate analyses showed that baseline NLR (&amp;lt; 2.5, ≥2.5) was a prognostic factor for PFS and OS (2-sided p&amp;lt; 0.0001). Patients with low baseline NLR consistently had better PFS and OS than those with high baseline NLR, and the treatment effect of ABE against PBO was consistently observed regardless of NLR category (Table 1). Univariate analyses showed that baseline ALC (&amp;lt; 1.5 × 109/L, ≥1.5 × 109/L) was also a prognostic factor for PFS and OS (2-sided p=0.0116 and 0.0032, respectively). PFS and OS were better for patients with high baseline ALC than for those with low baseline ALC, and the treatment effect of ABE against PBO was observed regardless of ALC category (Table 1). For PFS, the multivariate model was adjusted for Eastern Cooperative Oncology Group performance status (ECOG PS), tumor grade, presence of liver metastasis, and bone-only disease. For OS, the multivariate model was adjusted for sensitivity to endocrine therapy, ECOG PS, presence of liver metastasis, and bone-only disease. When adjusting for these additional prognostic factors, baseline NLR, but not baseline ALC, remained statistically significant in the multivariate model (2-sided p&amp;lt; 0.0001). Conclusions: These exploratory analyses suggest that while both baseline NLR and ALC are prognostic of clinical outcomes, only baseline NLR is independently prognostic of PFS and OS. Low baseline NLR was associated with better PFS and OS outcomes, but the benefit of adding ABE to fulvestrant was similar regardless of baseline NLR status. Table 1. Summary of outcomes by treatment arm for NLR and ALC categories ALC, absolute lymphocyte count; CI, confidence interval; NLR, neutrophil-to-lymphocyte ratio; NR, not reached; OS, overall survival; PFS, progression-free survival. Citation Format: Eriko Tokunaga, Yasuo Miyoshi, Koji Dozono, Tsutomu Kawaguchi, Masakazu Toi. Association of Neutrophil-to-Lymphocyte Ratio and Absolute Lymphocyte Count with Clinical Outcomes for Patients with Advanced Breast Cancer in the MONARCH 2 Trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-23.

Economic Evaluation for Palbociclib Plus Fulvestrant vs Ribociclib Plus Fulvestrant and Abemaciclib Plus Fulvestrant in Endocrine-Resistant Advanced or Metastatic Breast Cancer in Italy.

To date, no study evaluated the cost-effectiveness of palbociclib (PAL) plus fulvestrant (FUL) vs ribociclib (RIB) plus FUL and abemaciclib (ABM) plus FUL in Italy. Cost-effectiveness analysis comparing the three cyclin-dependent 4/6 kinase inhibitors in combination with endocrine therapies for the management of postmenopausal women with HR+, HER2- advanced or metastatic breast cancer in Italy was developed. To assess the cost-effectiveness of PAL plus FUL vs RIB plus FUL and ABM plus FUL, a cost-minimization has been carried out with a conservative scenario considering three CDK4/6 inhibitors with equal effectiveness in terms of overall survival (OS) (MAIC, Rugo et al 2021). Adverse events (AEs) associated with all therapies were obtained from clinical trials. Ad-hoc analysis was performed to estimate the cost-effectiveness considering the quality-of-life (QoL) data (Lloyd et al 2006). Cost-minimization inputs were drugs, visits and exams, AE monitoring and best supportive care (BSC) before the progression state, active and BSC in the progression and terminal phase of the last two weeks of life. Given the comparability of PAL, RIB and ABM in terms of efficacy, this analysis demonstrated slight economic savings over a lifetime for PAL. Results showed saving per patient of €305 (lifetime) when PAL is compared with RIB; for PAL vs ABM a saving of €243 (lifetime) in a conservative scenario. Results of a budget impact analysis showed a potential savings of €319,563 for PAL vs RIB and €297,544 for PAL vs ABM. When QoL data were considered, results may favor PAL due to the lower impact of AE with savings and improvement in the QoL related to fewer AE. From the Italian perspective, a cost-saving profile associated with the use of PAL+FUL for the management of advanced/metastatic HR+/HER2- breast cancer compared to RIB+FUL and ABM+FUL emerged.

Abstract P5-02-05: Detection of high-risk patients resistant to CDK4/6 inhibitors with hormone receptor-positive HER2-negative breast cancer in Japan

Abstract (Background) Cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) improve the prognosis of hormone receptor-positive HER2-negative breast cancer (HR+/HER2- BC) by approximately 5 years. However, some patients show resistance to CDK4/6i and have poor prognosis. Thus, predicting resistance in patients is important. Although PAM50 is a strong tool for predicting late recurrence risk in HR+/HER2- BC by analyzing gene expression signatures, it is not always available. The non-luminal disease score (NOLUS), developed as an approximate formula for PAM50, is a pathology-based subtyping assay used to predict non-luminal disease using immunohistochemical analysis (Pascual et al. Front Oncol, 2021). (Materials &amp; Methods) This multicenter, retrospective observational study was approved by the central ethics committee of Gifu University. From December 2017 to December 2021, real-world data of patients with metastatic HR+/HER2- BC who received CDK4/6i therapy were collected from 11 institutes in Japan. Data were obtained for patients who received CDK4/6i, such as palbociclib (PAL) or abemaciclib (ABE), as the first- or second-line endocrine therapy. The association between the efficacy of CDK4/6i and NOLUS was investigated by evaluating pathological and clinical data, including progression-free survival (PFS) and overall survival (OS). Pathological data, including the expression levels of ER, PgR, HER2, and Ki67, were evaluated according to the ASCO/CAP guidelines by experienced pathologists in each institute using either primary or metastatic tumors. PFS was defined as the period from the 1) starting date of combination therapy to progressive disease (PD); 2) the starting date of combination therapy to PD when CDK4/6i was interrupted due to adverse events or patients’ preference; and 3) the starting date of endocrine monotherapy to PD when CDK4/6i was added. NOLUS was calculated using the formula: NOLUS (0-100) = -0.45*ER% − 0.28*PR% + 0.27*Ki67% + 73, and the patients were divided into two groups, NOLUS(+) [≥ 51.38, non-luminal disease] and NOLUS(−) [&amp;lt; 51.38, luminal disease]. The expression levels of ER, PgR, HER2, and Ki67 in each group were compared using Wilcoxon rank-sum and Fisher’s exact tests. Next, prognosis, including survival rate, PFS, and OS, was evaluated with a 95% confidence interval (CI) using the Kaplan–Meier method with the log-rank test. Statistical significance was set at p &amp;lt; 0.05. (Results) Of the 300 patients, 28 (9.3%) were NOLUS(+) and 272 (90.7%) were NOLUS(−). The expression rates (%) in NOLUS(+) and NOLUS(−) were, respectively, 28.2 ± 19.4 and 89.0 ± 11.3 for ER (p &amp;lt; 0.001); 6.3 ± 15.9 and 44.3 ± 37.9 for PgR (p &amp;lt; 0.001); and 42.5 ± 23.8 and 26.9 ± 19.1 for Ki67 (p &amp;lt; 0.001). The expressions of HER2 (score 0, 1, 2, and ISH-negative, 3) were 42.9%, 28.6%, 28.6%, and 0% for NOLUS(+); and 30.8%, 51.7%, 17.5%, and 0.4% for NOLUS(−) (p = 0.086). There were apparent statistical differences in prognosis between the NOLUS(+) and NOLUS(−) groups. PFSs for 6M and 1y were 71.4% and 30.5% for NOLUS(+), and 85.2% and 66.6% for NOLUS(−) (HR, 3.15; 95%CI: 2.02-4.93; p &amp;lt; 0.001). OS for 6M and 1y were 92.6% and 92.6% for NOLUS(+), and 97.7% and 93.8% for NOLUS(−) (HR, 3.01; 95%CI: 1.48-6.09, p = 0.001). NOLUS(−) patients showed statistically better PFS with first-line therapy than with second-line therapy. However, NOLUS(+) patients showed no prognostic difference between the first and second therapeutic lines, suggesting CDK4/6i inefficacy. (Conclusion) CDK4/6i efficacy and prognosis were significantly different between NOLUS(+) and NOLUS(−) patients. This feasible method can predict patients with CDK4/6i-resistance and help select a better therapeutic approach to overcome resistance. Citation Format: Manabu Futamura, Takahiro Nakayama, Tersuhiro Yoshinami, Chiya Oshiro, Mikiya Ishihara, Midori Morita, Akira Watanabe, Azusa Taniguchi, Masami Tsukabe, Masafumi Shimoda, Kanae Mitta, Yoko Chihara, Hiroyuki Yasojima, Yoshimi Ouchi, Yoshihisa Tokumaru, Takuma Ishihara, Norikazu Masuda. Detection of high-risk patients resistant to CDK4/6 inhibitors with hormone receptor-positive HER2-negative breast cancer in Japan [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-05.

Abstract P4-01-26: Real-world treatment duration of subsequent therapy after palbociclib (PAL) in patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2−) advanced breast cancer (ABC) in Japan

Abstract Background: PAL is a first-in-class cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) for the treatment of HR+/HER2− ABC. Two CDK4/6is are currently available in Japan; PAL and abemaciclib (ABE). CDK4/6i+endocrine therapy (ET) has shown significant clinical benefits compared to ET alone in clinical trials. CDK4/6i combination therapy is strongly recommended as a first-line (1L) treatment in global and Japanese treatment guidelines. However, no optimal subsequent treatment has been established after discontinuing treatment with CDK4/6i+ET. Substantial data are required to determine whether the available treatment options remain effective after CDK4/6i treatment. Here, we report the treatment pattern of subsequent therapy after PAL in a real-world setting in Japan to provide insights into the optimal subsequent therapy. Methods: This retrospective, observational study utilized a nationwide hospital-based medical claims database managed by Medical Data Vision (MDV). The MDV database, one of the largest medical databases in Japan, covers 26% of acute-care hospitals across Japan, including 226 cancer therapeutic facilities. We evaluated the data of patients who received PAL from September 2017 to June 2021 and subsequently received therapy. Any treatment for ABC initiated within 30 days was considered part of one regimen. The median time-to-treatment failure (TTF) of subsequent therapy was estimated using the Kaplan–Meier method. Results: From the database, we identified 1,170 patients with HR+/HER2− ABC who received PAL, among which 398 (34%) received combination therapy as 1L treatment. The median age at PAL initiation was 64 years (range 53–72), and 13.0% of the patients were pre-/peri-menopausal. Among the 398 patients, 224 (56.3%) received therapy after PAL+ET. Endocrine-based therapy was commonly used as the first subsequent therapy (n=136; 60.7%), including CDK4/6i+ET (n=70; 31.2%), ET alone (n=39; 17.4%), and everolimus+ET (n=27; 12.1%). Among the 81 (36.2%) patients who received chemotherapy as the first subsequent therapy, 27 (12.1%) received bevacizumab+chemotherapy. The median TTF (95% confidence interval [CI]) of the first subsequent therapy was 7.5 months (6.5–8.4), and that of each subsequent regimen is listed in Table 1. The median TTF (95% CI) for patients received CDK4/6i+ET as first subsequent therapy after PAL+ET was the longest among the regimens, 10.9 months (6.5–15.6). Among the 70 patients, 36 changed only CDK4/6i type, 17 changed only ET type, and 12 changed both CDK4/6i and ET types. The median TTF (95% CI) was 20.1 months (6.5– not reached [NR]), 8.7 months (2.9–11.2), and 7.7 months (2.6–NR), respectively. No obvious trend was observed between the TTF of PAL+ET as a 1L treatment and the TTF of subsequent ABE after the PAL+ET treatment. Conclusion: More than half the patients received endocrine-based therapy after PAL+ET as a 1L treatment, and the observed treatment duration was comparable to the results of clinical trials reported to date, even after PAL treatment. ET+targeted therapy and chemotherapy represent acceptable treatment options after PAL+ET. One-third of patients received CDK4/6i+ET after PAL+ET in Japanese clinical practice; however, further investigation is warranted to confirm that this treatment strategy is effective. Table 1. Median TTF of each subsequent therapy after PAL+ET Citation Format: Masataka Sawaki, Yasuaki Muramatsu, Kanae Togo, Hiroji Iwata. Real-world treatment duration of subsequent therapy after palbociclib (PAL) in patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2−) advanced breast cancer (ABC) in Japan [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-26.

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.