Abemaciclib Therapy Research Articles

Predictors of abemaciclib discontinuation in patients with breast cancer: a multicenter retrospective cohort study

ObjectiveThis study explored the predictors of abemaciclib discontinuation, a cyclin-dependent kinase 4 and 6 inhibitor, in patients with breast cancer.Material and MethodsBetween November 2018 and March 2023, 147 patients with breast cancer treated with abemaciclib at Osaka Medical and Pharmaceutical University Hospital and Kindai University Nara Hospital were included. The exclusion criteria were as follows: lack of blood testing within 2 weeks prior to starting abemaciclib therapy, transfer to another facility after the commencement of abemaciclib therapy, and discontinuation of abemaciclib therapy due to the diagnosis of another cancer. The duration from the initiation of abemaciclib to discontinuation for any reason and to temporary suspension or dose reduction due to adverse events were analyzed as outcome variables using multivariate Cox regression analysis.ResultsBaseline weight < 54 kg, bone metastases, and hemoglobin level ≤ 12.4 g/dL were independent predictors of abemaciclib discontinuation for any reason. The main adverse events leading to abemaciclib discontinuation were liver enzyme elevation and gastrointestinal symptoms. Additionally, focusing on the adverse event of abemaciclib, a baseline weight < 54 kg was an independent predictor of temporary suspension or dose reduction due to adverse events. The most common adverse events leading to temporary suspension or dose reduction were neutropenia and diarrhea.ConclusionPatients with lower body weight are more susceptible to the adverse events of abemaciclib, increasing their risk of treatment discontinuation. In such patients, strict monitoring of adverse events and consideration of more frequent medical visits are necessary from the start of abemaciclib therapy.

Abemaciclib Therapy Using the MonarchE Criteria Results in Large Numbers of Excess Axillary Node Clearances-Time to Pause and Reflect?

The monarchE study added the CDK4/6 inhibitor abemaciclib to the care of women with oestrogen-positive (ER+) breast cancers. Eligibility required meeting monarchE criteria-either >3 positive axillary nodes, or 1-3 positive sentinel nodes (SNB+) with tumour size >50 mm or grade 3 cancers. Women were advised to proceed to completion axillary node clearance (cANC) if size/grade criteria were not fulfilled for >3 positive nodes to be identified. However, cANC is associated with significant morbidity, conflicting with the potential benefits of abemaciclib. We analysed data of 229 consecutive women (2016-2022) with ER+ breast cancer and SNB+ who proceeded to cANC, keeping with contemporary treatment guidelines. We used this cohort to assess numbers that, under national guidance in place currently, would be advised to undergo cANC solely to check eligibility for abemaciclib treatment. Using monarchE criteria, 90 women (39%) would have accessed abemaciclib based on SNB+ and size/grade, without cANC. In total, 139 women would have been advised to proceed to cANC to check eligibility, with only 15/139 (11%) having >3 positive nodes after sentinel node biopsy and cANC. The remaining 124 (89%) would have undergone cANC but remained ineligible for abemaciclib. Size, age, grade, and Ki67 did not predict >3 nodes at cANC. Following cANC, a large majority of women with ER+, <50 mm, and grade 1-2 tumours remain ineligible for abemaciclib yet are subject to significant morbidity including lifelong lymphoedema risk. The monarchE authors state that 15 women need abemaciclib therapy for 1 to clinically benefit. Thus, in our cohort, 139 women undergoing cANC would lead to one woman benefitting.

Monitoring of estradiol levels in premenopausal women receiving adjuvant abemaciclib and ovarian function suppression.

Approximately 15% of women who receive ovarian function suppression (OFS) as adjuvant treatment for high-risk, localized hormone receptor-positive (HR+) breast cancer may have inadequate estradiol suppression which can require therapeutic modification when used in combination with an aromatase inhibitor (AI). We previously reported that abemaciclib may interfere with the estradiol Abbott Alinity chemiluminescent microparticle immunoassay (CMIA) commonly used to monitor estradiol levels and suggested liquid chromatography-mass spectrometry (LC-MS/MS) is preferred in this setting. The aim of this study was to determine discrepancies in estradiol levels using CMIA compared to LC-MS/MS and subsequent treatment changes in a larger patient population. We conducted a retrospective review of premenopausal women with early-stage HR+ breast cancer at our institution who received adjuvant OFS and abemaciclib with at least 1 CMIA estradiol level drawn during abemaciclib therapy from October 2021 to April 2023. Of the 22 women who met criteria for review, 20 (90.9%) had CMIA estradiol levels in the premenopausal range, of whom 9 also had estradiol measured by LC-MS/MS. All 9 women receiving OFS and abemaciclib with estradiol measurements by both methods had premenopausal range CMIA estradiol levels and postmenopausal range LC-MS/MS estradiol levels. Of the 20 patients with premenopausal estradiol levels by CMIA estradiol, treatment changes included increased OFS dosage or preparation (n = 7), change from AI to tamoxifen (n = 3), and surgical oophorectomy (n = 7). Our findings suggest the likely interference of abemaciclib with the Abbott Alinity immunoassay which may lead to unnecessary treatment changes. It is recommended that the LC-MS/MS assay be used when monitoring estradiol levels in patients receiving abemaciclib concurrently with OFS.

HER4 Affects Sensitivity to Tamoxifen and Abemaciclib in Luminal Breast Cancer Cells and Restricts Tumor Growth in MCF-7-Based Humanized Tumor Mice.

The impact of the HER4 receptor on the growth and treatment of estrogen receptor-positive breast cancer is widely uncertain. Using CRISPR/Cas9 technology, we generated stable HER4 knockout variants derived from the HER4-positive MCF-7, T-47D, and ZR-75-1 breast cancer cell lines. We investigated tumor cell proliferation as well as the cellular and molecular mechanisms of tamoxifen, abemaciclib, AMG232, and NRG1 treatments as a function of HER4 in vitro. HER4 differentially affects the cellular response to tamoxifen and abemaciclib treatment. Most conspicuous is the increased sensitivity of MCF-7 in vitro upon HER4 knockout and the inhibition of cell proliferation by NRG1. Additionally, we assessed tumor growth and immunological effects as responses to tamoxifen and abemaciclib therapy in humanized tumor mice (HTM) based on MCF-7 HER4-wildtype and the corresponding HER4-knockout cells. Without any treatment, the enhanced MCF-7 tumor growth in HTM upon HER4 knockout suggests a tumor-suppressive effect of HER4 under preclinical but human-like conditions. This phenomenon is associated with an increased HER2 expression in MCF-7 in vivo. Independent of HER4, abemaciclib and tamoxifen treatment considerably inhibited tumor growth in these mice. However, abemaciclib-treated hormone receptor-positive breast cancer patients with tumor-associated mdm2 gene copy gains or pronounced HER4 expression showed a reduced event-free survival. Evidently, the presence of HER4 affects the efficacy of tamoxifen and abemaciclib treatment in different estrogen receptor-positive breast cancer cells, even to different extents, and is associated with unfavorable outcomes in abemaciclib-treated patients.

Abstract PO1-17-09: Real-world clinical outcomes in US patients with brain metastases secondary to HR+/HER2- metastatic breast cancer treated with abemaciclib

Abstract Background: Abemaciclib has demonstrated pharmacologically relevant intracranial concentrations and antitumor activity in patients with brain metastases secondary to HR+/HER2- metastatic breast cancer (MBC). However, clinical data is limited, and further assessments are warranted. This retrospective study describes real-world outcomes following abemaciclib initiation in patients with brain metastases secondary to HR+/HER2- MBC. Methods: Data were accessed from the US nationwide Flatiron Health electronic health records-derived de-identified database from 01/01/2011 to 12/31/2021. This real-world study included adult patients with a diagnosis of HR+/HER2- MBC with brain metastases prior to abemaciclib initiation. Patient and treatment characteristics were summarized using descriptive statistics. Kaplan-Meier methods were used to assess clinical outcomes from abemaciclib initiation: time to treatment discontinuation (TTD), progression-free survival (rwPFS), overall survival (rwOS). Intracranial rw best responses were also reported. Results: This study included 82 patients (one male) diagnosed with MBC and brain metastases prior to abemaciclib initiation and the median follow-up was 12.8 months. At data cut-off, 17 (20.7%) patients remained on abemaciclib therapy. Twenty-three (28%) patients received abemaciclib as the first line of therapy for MBC. Of the 82 patients in the study, 68 (82.9%) patients used concomitant endocrine therapy. Prior to abemaciclib initiation, 25 (30.5%) patients received chemotherapy and 33 (40.2%) patients received a CDK4 and 6 inhibitor. Most patients (67.1%) initiated abemaciclib at a dose of 150 mg twice daily. The median time from diagnosis of brain metastasis to abemaciclib initiation was 2.1 months (interquartile range:1.0, 8.0); 16 (19.5%) did not undergo surgical resection or receive radiation to the brain during this time. Sixty-six (80.5%) patients received brain radiation of which 56.1% received stereotactic radiosurgery (SRS) and 47.0% received whole-brain radiation (WBRT) either alone or in combination with craniotomy/metastasectomy, intrathecal chemotherapy, or surgery. The median TTD for abemaciclib was 7.1 months (95% confidence interval [95% CI]: 4.6, 11.3); most common reasons for discontinuation were disease progression (39.0%) or adverse events (29.3%). The median rwPFS was 9.2 months (95% CI: 6.0, 11.6) and median rwOS was 20.8 months (95% CI: 13.9, 26.0). Of the patients where response data were available (n = 51), rw intracranial clinical benefit rate (CBR; complete response [CR]/partial response [PR]/stable disease [SD] ≥24 weeks of abemaciclib initiation) was 62.7% (Table 1). Conclusion: In this real-world study, most patients with brain metastases secondary to HR+/HER2- MBC who initiated abemaciclib treatment received SRS or WBRT prior to or concurrent with abemaciclib initiation. While the clinical outcomes, rwPFS and intracranial CBR were encouraging, these findings should be interpreted with caution due to the nature of the real-world study design. Table 1. Intracranial Real-World Best Responses Citation Format: Wambui Gathirua-Mwangi, Holly Martin, Dan He, Shen Zheng, Kristin Sheffield, Jincy John, Sarah Rybowski, Priscilla Brastianos. Real-world clinical outcomes in US patients with brain metastases secondary to HR+/HER2- metastatic breast cancer treated with abemaciclib [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 PO1-17-09.

Abstract PO5-02-01: Concerning Discrepancies in Estradiol Levels in Premenopausal Women Receiving Abemaciclib and Ovarian Function Suppression

Abstract Background: Adjuvant abemaciclib in combination with endocrine therapy improves outcomes for patients with high-risk, hormone receptor-positive (HR+), HER2-negative early-stage breast cancer. In premenopausal women, the use of an aromatase inhibitor (AI) requires chemical or surgical ovarian function suppression (OFS). Our published case report of a premenopausal woman receiving adjuvant abemaciclib with elevated estradiol levels measured by the Abbott Alinity chemiluminescent microparticle immunoassay (CMIA) despite bilateral salpingo-oophorectomy (BSO) but low estradiol levels using liquid chromatography-mass spectrometry (LC-MS/MS) suggested an interference of abemaciclib with the immunoassay (PMID: 37124155). The aim of this study was to determine discrepancies in estradiol levels using CMIA compared to LC-MS/MS and subsequent treatment changes in a larger patient population. Methods: We conducted an IRB-approved retrospective review of premenopausal women with early-stage HR+ breast cancer treated with adjuvant OFS and abemaciclib at our institution from October 2021 to April 2023 who had at least 1 CMIA estradiol level drawn during abemaciclib therapy. Pathology, treatment plans, and lab data were abstracted from medical records. Postmenopausal estradiol levels were based on reference ranges of &amp;lt; 41 pg/mL using CMIA or &amp;lt; 15 pg/mL using LC-MS/MS. We utilized descriptive statistics to describe the population and management. Results: We identified 22 patients who met criteria for our review. The average age was 42.3 years, all had positive axillary nodes, 6 (27%) received neoadjuvant chemotherapy, and 15 (68%) received adjuvant chemotherapy. There were 14 (64%) patients who received leuprolide and 8 (36%) received goserelin, whereas 19 (86%) received AI and 3 (14%) received tamoxifen as their initial oral antiestrogen therapy. The majority of patients did not have baseline estradiol levels when starting OFS though after starting abemaciclib, 20 patients had CMIA estradiol levels in the premenopausal range, 9 of which had estradiol monitored by both CMIA and LC-MS/MS (Table 1). The average length of time from starting OFS to starting abemaciclib was 144.6 days with 1 patient switching from tamoxifen to OFS and AI after starting abemaciclib. Due to elevated CMIA estradiol, treatment changes included increased OFS dosage (5 patients), change of OFS (2 patients), and change to tamoxifen (3 patients). There were 6 patients who underwent BSO, 3 due to persistently elevated CMIA estradiol levels, 2 due to patient preference, and 1 due to a BRCA mutation. Following surgery, 2 patients had persistently elevated CMIA estradiol but low LC-MS/MS estradiol. The remainder of these patients did not have estradiol levels measured by CMIA. Conclusions: Our retrospective review demonstrated the likely interference of abemaciclib with the Abbott Alinity immunoassay as shown by 9 patients treated with OFS and abemaciclib with simultaneous premenopausal range CMIA estradiol levels and postmenopausal range LC-MS/MS estradiol levels. As up to 91% of patients in our study may have had a false positive estradiol level erroneously suggesting inadequate OFS, monitoring of estradiol levels using the CMIA assay in patients receiving adjuvant abemaciclib in addition to OFS could lead to changes in therapy that may be unnecessary. It is recommended that the LC-MS/MS assay be used when monitoring of estradiol levels is indicated in patients receiving abemaciclib concurrently with OFS. Table 1: Estradiol levels in patients receiving OFS and abemaciclib who had both CMIA and LC-MS/MS assays Citation Format: Alaina Kessler, Rima Patel, Emily Gallagher, Tianxiang Sheng, Damodara Rao Mendu, Amy Tiersten, Paula Klein, Aarti Bhardwaj, Anupama Goel, Joseph Sparano, Theresa Shao, Julie Fasano. Concerning Discrepancies in Estradiol Levels in Premenopausal Women Receiving Abemaciclib and Ovarian Function Suppression [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 PO5-02-01.

Abstract PO3-02-01: Educational Opportunities to Improve Community Healthcare Professionals’ Management of High-Risk HR-Positive/HER2-Negative Early Breast Cancer

Abstract Background: The treatment landscape for patients with hormone receptor–positive/HER2-negative early breast cancer (HR+/HER2- EBC) has evolved with the emergence of adjuvant CDK4/6 inhibitor therapy as a new option for patients with a high risk of disease recurrence. Adjuvant abemaciclib plus aromatase inhibitors (AIs) is guideline recommended for high clinical risk HR+ disease and reduces risk of recurrence regardless of Ki-67 expression level. Here, we examine healthcare professionals’ (HCPs’) awareness and practice regarding the use of adjuvant abemaciclib. Methods: Between November 2022 and June 2023, we conducted a series of regional educational activities for HCPs focused on management of high-risk HR+/HER2- EBC. Each activity included an interactive lecture led by a clinical investigator with expertise in managing patients with high-risk HR+/HER2- EBC and polling questions designed to assess key aspects of HCP knowledge and practice in the optimal management of high-risk HR+/HER2- EBC. A wider HCP audience was able to view an interactive on-demand webcast with the same content and embedded polling questions. Results: In total, 701 HCPs participated in one of 20 live (n = 373) activities or the one associated on-demand (n = 328) webcast. The distribution of HCP participation differed between the live and online activities with more physicians participating in the online activity vs the live activity (59% vs 34%, respectively); the converse was true for nurse participation (9% online vs 34% live). Polling result trends were similar between the live and online activities. At baseline, 38% (n/N = 182/405) of HCPs chose adjuvant therapy with an AI plus abemaciclib for a patient with high-risk, node-positive HR+/HER2- EBC consistent with expert and guideline recommendations. Following the education, 92% (n/N = 405/439) of HCPs selected AI plus abemaciclib for appropriate patients. Before education, 32% of HCPs (n/N = 147/454) were aware that adjuvant abemaciclib plus endocrine therapy improved invasive disease-free survival compared with endocrine therapy alone in patients with high-risk, node-positive HR+/HER2- EBC regardless of Ki-67 expression level, which increased to 87% (n/N = 370/425) following the education. Regarding the management of grade 2 neutropenia associated with adjuvant abemaciclib therapy, HCP knowledge was low at baseline (32%, n/N = 141/446) and improved to 80% (n/N = 332/415) after education. Conclusions: HCPs’ knowledge of and practice concerning adjuvant abemaciclib as a newer approved therapy for patients with high-risk HR+/HER2- EBC remain suboptimal. These results suggest an ongoing need for expert guidance and educational activities on the use of adjuvant abemaciclib therapy for appropriate patients with high-risk HR+/HER2- EBC. As the treatment landscape for HR+/HER2- EBC continues to evolve with the potential approval of additional new therapies, this need will only increase with a clear impact on optimizing and individualizing adjuvant therapy strategies for patients with HR+/HER2- EBC. Citation Format: Marie Becker, Timothy Quill, Erika Hamilton, Joyce O'Shaughnessy. Educational Opportunities to Improve Community Healthcare Professionals’ Management of High-Risk HR-Positive/HER2-Negative Early 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 PO3-02-01.

Abstract PO4-17-12: Early adherence to adjuvant abemaciclib: Data from the Belgian Medical Need Program

Abstract Patient adherence profiles for adjuvant hormonal therapy combined with abemaciclib in HR+/HER2- High Risk EBC based on real world evidence (RWE) from a Medical Need Program in Belgium Background Following results of MonarchE, demonstrating clinically meaningful improvement in invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS), a 2-year treatment with abemaciclib has been reimbursed in Belgium since May 1st, 2023 for the adjuvant treatment of HR+, HER2–, lymph node-positive (&amp;gt;3 or 1-3 if pT3 or grade 3) early breast cancer (EBC). In this trial, adverse event related treatment discontinuation was reported in 18,5% (8.9% after dose reduction) of which 10.1% in the first 5 months after starting this CDK 4/6 inhibitor. Prior to reimbursement, an early access program was initiated in Belgium on June 28 2022. We studied the proportion of patients estimated to be eligible for the program nationwide who effectively started adjuvant abemaciclib, as well as early treatment discontinuation and dose reductions. Methods The number of eligible patients for the adjuvant abemaciclib Medical Need Program (MNP) was estimated by the Belgian Cancer Registry based on the above mentioned reimbursement criteria for patients registered during the incidence year 2018. The MNP was active in Belgium from June 28 2022 until May 1 2023. Discontinuation rate and proportion with dose reductions were calculated using a nationwide prospective managed monthly updated register of participating patients including information on age at diagnosis, time since therapy start, delivered doses and patient reported adverse events (AE). They all signed an informed consent and agreed to share their registered data after anonymization. Data analysis was retrospective. Descriptive statistics were used. Results In this 10-month period, 840 patients were estimated to be eligible to receive adjuvant abemaciclib in Belgium. A total of 311 patients (309 women, 2 men) were included in the program, 37% of the estimated number of patients. Median age at initiation was 57 y. Median time on treatment was 4.5 months (156 patients &amp;gt;4.5 months on treatment). 21/311 (6.7%) patients discontinued (all causes). 2 patients never started. 10 patients (3.2%) discontinued their therapy without dose reduction. 12/311 (3.8%) had a starting dose of 2 × 100 mg/d. 128/311 (41.1%) had a dose reduction, 96/128 (75%) before 3 months of therapy. In the subgroup of 156 patients starting treatment &amp;gt;4.5 months ago, 16/156 (10.2%) discontinued treatment, 13 patients have not yet been reported. 79/156 (50.6%) required a dose reduction, of which 7 (4.5%) discontinued after dose reduction. The reasons for discontinuation reported: 8/21 (38%) gastro-intestinal intolerance, 3/21 (14.2%) real deterioration in renal function, 8/21 quality of life issues (not specified), 1/21 anal burning sensation and anal fistula, 3/21 asthenia and fatigue. Conclusion Of the estimated eligible patients in Belgium 37 % started with adjuvant abemaciclib. These results illustrate that there is a need to further improve implementation of adjuvant abemaciclib. Early results show that 89.8% of patients receiving adjuvant abemaciclib therapy in Belgium continued their treatment after 4.5 months and 50% of patients needed a dose reduction. Longer follow-up will be needed. Understanding the reasons of discontinuation and early dose adjustments can enable better patient support on adherence. This is a critical capability to ensure optimal patient compliance. Citation Format: Maxime Van Houdt, Marc Michaux, Sevilay Altintas, Ahmad Awada, Jean-Luc Canon, Hannelore Denys, François Duhoux, Guy Jerusalem, Jeroen Mebis, Rosanne Janssens, Isabelle Huys, Barbier Liese, Charlotte Verbeke, Sileny Han, Hans Wildiers, Patrick Neven. Early adherence to adjuvant abemaciclib: Data from the Belgian Medical Need Program [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 PO4-17-12.

The Real-world Experiences of Abemaciclib for Estrogen Receptor-positive Human Epidermal Growth Factor Receptor-negative-2 Metastatic Breast Cancer – Sharing from a Single Institute in Southern Taiwan

Abstract Background: CDK 4/6 inhibitor (CDK4/6i) is the first-line therapeutic drug to treat ER-positive (ER+) HER2-negative (HER2 -) metastatic breast cancer (MBC) now. We have three CDK4/6i: Palbociclib, Ribociclib, and Abemaciclib. In the long-term follow-up study, there are some different results among the three CDK4/6i. Some real-world reports demonstrated some patients would have clinical benefits from Abemaciclib in the ER+ HER2- metastatic BC patients who had priorly received the other CDK 4/6 inhibitor (Palbociclib). In Taiwan, Abemaciclib is the third available CDK 4/6 inhibitor behind the other two CDK4/6i. However, Abemaciclib was not reimbursed in ER+ HER2- MBC by Taiwan Health Insurance until now. Most doctors in Taiwan have the less therapeutic experiences for Abemaciclib. In this article, we would share the clinical experiences for the first thirteen patients who were prescribed with Abemaciclib to treat ER+ HER2- MBC. Materials and Methods: This chart review study was conducted from January 1, 2020, to May 31, 2023. We reviewed the medical charts at National Cheng Kung University Hospital (NCKUH) and identified 13 patients who had received abemaciclib treatment for ER+ HER2− MBC. The study was approved by the Institutional Review Board at NCKUH (approval number: B-ER-112-220). All of the 13 patients were treated with abemaciclib (150 mg twice daily initially), in combination with other anti-cancer medications. We recorded the clinical parameters, including sex, age, treatments in neoadjuvant/adjuvant setting, metastatic sites, other prior CDK4/6i therapy, treatment lines of abemaciclib in the metastatic setting, survival period before abemaciclib treatment, time to treatment failure for abemaciclib, causes of abemaciclib discontinuation, dose reduction, and adverse effects (AEs) related to abemaciclib. Results: Up to the cut-off date (May 31, 2023), four (4/13) patients were still receiving therapy and nine patients (9/13) had discontinued abemaciclib therapy. Five (5/9) patients discontinued abemaciclib due to disease progression (PD), and two (2/9) patients interrupted abemaciclib treatment due to personal reasons. Two (2/9) patients stopped abemaciclib early because of AEs, and one patient died due to PD. The time to treatment failure for abemaciclib ranged from 1 to 41 months (average: 19.2 months, median: 14 months). AEs were noted in 12 patients (no recording in one patient), of which diarrhea (10/12), anemia (4/12), and neutropenia (3/12) were the most common. Conclusion: According to our real-world data, Abemaciclib is effective and safe for the ER+ HER2- metastatic BC cancer patients who they were heavily treated.

Abstract 5266: Deciphering the systemic immune effects of abemaciclib in recurrent metastatic breast cancer: A multicenter, prospective study

Abstract Background: Abemaciclib, a CDK4/6 inhibitor, stands as a cornerstone for managing hormone receptor-positive, HER2-negative advanced or metastatic recurrent breast cancer. It is known to modulate the tumor immune microenvironment, enhancing anti-tumor responses. Yet, its systemic immunological impact remains to be elucidated. This investigation aims to delineate the influence of abemaciclib on both the gut microbiota and the systemic immune landscape in patients with breast cancer. Methods: A multicenter, prospective clinical trial was conducted involving 40 patients with hormone receptor-positive, HER2-negative advanced or metastatic recurrent breast cancer, scheduled for abemaciclib therapy. The trial's primary objectives were to evaluate the duration of treatment efficacy and the severity of gastrointestinal toxicity. Secondary objectives included assessing the interplay between circulating immune profiles, gut microbiota, and clinical outcomes. Patient samples, including peripheral blood mononuclear cells (PBMCs) for single-cell RNA sequencing and stool for 16S rRNA gene analysis, were collected at baseline and after 90 days of treatment initiation. Results: This interim report presents findings from 39 patients. We examined 75 PBMC samples and 78 stool samples. Preliminary analysis indicated that abemaciclib precipitated an upregulation of cytokines pivotal for anti-tumor immunity, notably IL-7 and IP-10, alongside an activation of circulating innate immune cells such as CD4-positive T cells and dendritic cells. Concurrently, gut microbiota analysis revealed a post-treatment reduction in alpha diversity, with notable shifts in microbial populations implicated in innate immune activation. Discussion: This study presents novel insights into the systemic immunomodulatory effects of abemaciclib. Our results suggest that abemaciclib's therapeutic efficacy may partially derive from its ability to alter the circulating immune profile and gut microbiota. These findings could pave the way for innovative immunotherapeutic approaches, integrating gut microbiome considerations into the treatment of hormone receptor-positive, HER2-negative breast cancer. Citation Format: Yukiko Fukui, Kosuke Kawaguchi, Yurina Maeshima, Yuri Fujimoto, Hiroshi Ishiguro, Kazuhiko Yamagami, Sachiko Takahara, Hirofumi Suwa, Masae Torii, Shigenori Nagai, Yasuaki Sagara, Wakako Tsuji, Hiroyasu Yamashiro, Takeshi Kotake, Shinji Fukuda, Kuniaki Saito, Yasuko Yamamoto, Masako Kataoka, Yuki Himoto, Atsushi Yonezawa, Yuki Nakamura, Wei Li, Sunao Tanaka, Satoshi Morita, Masahiro Takada, Masakazu Toi. Deciphering the systemic immune effects of abemaciclib in recurrent metastatic breast cancer: A multicenter, prospective study [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 5266.

Ki-67 Testing in Breast Cancer: Assessing Variability With Scoring Methods and Specimen Types and the Potential Subsequent Impact on Therapy Eligibility.

Abemaciclib was originally FDA approved for patients with ER-positive/HER2-negative breast cancer with Ki-67 expression ≥20%. However, there were no guidelines provided on which specimen to test or which scoring method to use. We performed a comprehensive study evaluating the variation in Ki-67 expression in breast specimens from 50 consecutive patients who could have been eligible for abemaciclib therapy. Three pathologists with breast expertise each performed a blinded review with 3 different manual scoring methods [estimated (EST), unweighted (UNW), and weighted (WT) (WT recommended by the International Ki-67 in Breast Cancer Working Group)]. Quantitative image analysis (QIA) using the HALO platform was also performed. Three different specimen types [core needle biopsy (CNB) (n=63), resection (RES) (n=52), and axillary lymph node metastasis (ALN) (n=50)] were evaluated for each patient. The average Ki-67 for all specimens was 14.68% for EST, 14.46% for UNW, 14.15% for WT, and 11.15% for QIA. For the manual methods, the range between the lowest and highest Ki-67 for each specimen between the 3 pathologists was 8.44 for EST, 5.94 for WT, and 5.93 for UNW. The WT method limited interobserver variability with ICC1=0.959 (EST ICC1=0.922 and UNW=0.949). Using the aforementioned cutoff of Ki-67 ≥20% versus <20% to determine treatment eligibility, the averaged EST method yields 20 of 50 patients (40%) who would have been treatment-eligible, versus 15 (30%) for the UNW, 17 (34%) for the WT, and 12 (24%) for the QIA. There was no statistically significant difference in Ki-67 among the 3 specimen types. The average Ki-67 difference was 4.36 for CNB vs RES, 6.95 for CNB versus ALN, and RES versus ALN (P=0.93, 0.99, and 0.94, respectively). Our study concludes that further refinement in Ki-67 scoring is advisable to reduce clinically significant variation.

A Case Report of a Breast Cancer Patient Developing Pneumonitis as a Result of Abemaciclib Therapy

Introduction: Breast cancer is the most common cancer affecting women in the United States, and the prognosis is good, with a 5-year survival rate of 91.2%. Advancements in treatment options using molecular profiling have allowed therapies to be more personalized and have improved patient outcomes. Of the many specific therapy agents, cyclin-dependent kinase (CDK) 4/6 inhibitors, such as abemaciclib, are commonly used. Case: We present a case of a 74-year-old female with a history of HR+ breast cancer who has been on abemaciclib for over two and a half years and developed pneumonitis. Discussion: Pneumonitis, as a direct result of abemaciclib or other CDK 4/6 inhibitors, is a rare side effect with an unknown mechanism of action. The Federal Drug Administration (FDA) has warned about the potential for this severe and potentially fatal inflammation of the lungs when using these agents. No studies have investigated additional risk factors in developing this side effect. However, reviewing other case reports supports that patients typically develop this side effect within the first three years of treatment initiation. The mechanism of manifesting this side effect has not been explored. However, it has been proposed that it is related to over activation of the immune system. Treatment includes clinical observation for asymptomatic and glucocorticoids for symptomatic patients. Conclusion: This case highlights the complexities of breast cancer therapies and the rare side effects of pneumonitis with CDK 4/6 inhibition from drugs like abemaciclib. More research should be conducted to better understand and prevent the manifestation of this potentially fatal side effect.

Clinical protocol: Feasibility of evaluating abemaciclib neuropharmacokinetics of diffuse midline glioma using intratumoral microdialysis.

Diffuse midline gliomas (DMG) are the most aggressive brain tumors of childhood and young adults, with documented 2-year survival rates <10%. Treatment failure is due in part to the function of the BBB. Intratumoral microdialysis sampling is an effective tool to determine brain entry of varied agents and could help to provide a better understanding of the relationship of drug permeability to DMG treatment responsivity. This is a non-randomized, single-center, phase 1 clinical trial. Up to seven young adult (18-39 years) patients with recurrent high-grade or diffuse midline glioma will be enrolled with the goal of 5 patients completing the trial over an anticipated 24 months. All patients will take abemaciclib pre-operatively for 4.5 days at twice daily dosing. Patients will undergo resection or biopsy, placement of a microdialysis catheter, and 48 hours of dialysate sampling coupled with timed plasma collections. If intratumoral tumor or brain dialysate sampling concentrations are >10nmol/L, or tumor tissue studies demonstrate CDK inhibition, then restart of abemaciclib therapy along with temozolomide will be administered for maintenance therapy and discontinued with evidence of radiologic or clinical disease progression. The poor survival associated with diffuse midline gliomas underscore the need for improved means to evaluate efficacy of drug delivery to tumor and peritumoral tissue. The findings of this novel study, will provide real-time measurements of BBB function which have the potential to influence future prognostic and diagnostic decisions in such a lethal disease with limited treatment options. Trial registration: Clinicaltrials.gov, NCT05413304. Registered June 10, 2022, Abemaciclib Neuropharmacokinetics of Diffuse Midline Glioma Using Intratumoral Microdialysis.

TRLS-02. FEASIBILITY OF EVALUATING ABEMACICLIB NEUROPHARMACOKINETICS OF DIFFUSE MIDLINE GLIOMA USING INTRATUMORAL MICRODIALYSIS

Abstract BACKGROUND Diffuse midline gliomas (DMG) are the most aggressive brain tumors of childhood and young adults, with documented 2-year survival rates &amp;lt;10%. Treatment failure is due in part to the function of the BBB. Intratumoral microdialysis sampling is an effective tool to determine brain entry of varied agents and could help to provide a better understanding of the relationship of drug permeability to DMG treatment response. METHODS This is a non-randomized, single-center, phase 1 clinical trial. Up to seven young adult (18-39 years) patients with recurrent high-grade or diffuse midline glioma will be enrolled with the goal of 5 patients completing the trial over an anticipated 24 months. All patients will take abemaciclib pre-operatively for 4.5 days at twice daily dosing. Patients will undergo resection or biopsy, placement of a microdialysis catheter, and 48 hours of dialysate sampling coupled with timed plasma collections. If intratumoral tumor or brain dialysate sampling concentrations are &amp;gt;10nmol/L, or tumor tissue studies demonstrate CDK inhibition, then restart of abemaciclib therapy along with temozolomide will be administered for maintenance therapy and discontinued with evidence of radiologic or clinical disease progression. DISCUSSION The poor survival associated with diffuse midline gliomas underscore the need for improved means to evaluate efficacy of drug delivery to tumor and peritumoral tissue. The findings of this novel study, will provide real-time measurements of BBB function which have the potential to influence future prognostic and diagnostic decisions in such a lethal disease with limited treatment options. TRIAL REGISTRATION: Clinicaltrials.gov, NCT05413304. Registered June 10, 2022, Abemaciclib Neuropharmacokinetics of Diffuse Midline Glioma Using Intratumoral Microdialysis; https://clinicaltrials.gov/ct2/show/NCT05413304?term=22c0003&amp;draw=2&amp;rank=1

A Nomogram for Identifying HR+/Her2- Breast Cancer Patients with Positive Sentinel Lymph Nodes and Omitted Axillary Lymph Node Dissection Who Need Abemaciclib Therapy.

BACKGROUND The efficacy of abemaciclib in high-risk patients with early-stage HR+/Her2- breast cancer has been verified by MonarchE. However, accurately determining the number of axillary lymph node (ALN) metastases remains challenging. The Z0011 trial changed the axillary management strategy, eliminating the need for axillary lymph node dissection (ALND) in patients with 1-2 sentinel lymph node (SLN) metastases. Therefore, further exploration is needed to identify patients who could benefit from abemaciclib therapy. MATERIAL AND METHODS This retrospective study included cT1-2N0M0 HR+/Her2- patients with 1-2 positive SLNs who underwent ALND. Clinicopathological data were collected, and logistic regression analyses identified independent predictors for ≥4 positive ALNs. A predictive nomogram was developed, and discrimination and calibration were evaluated using the C-index and calibration curve. Clinical efficacy was assessed using decision curve analysis (DCA). RESULTS We enrolled 444 patients, with 77 (17.3%) having ≥4 positive ALNs. Independent predictors for ≥4 positive ALNs included abnormal ALN on ultrasound, mammographic calcifications, T stage, and the number of positive SLNs. The nomogram demonstrated an AUC of 0.777 (95% CI: 0.735-0.815, P<0.001), and internal validation showed good calibration and discrimination (C-index, 0.802; 95% CI: 0.779-0.824). DCA revealed a positive net benefit for risk levels ranging from 5% to 54%. CONCLUSIONS This nomogram is a convenient and reliable tool to predict the risk of ≥4 positive ALNs in HR+/Her2- patients. It aids in protocol selection by identifying SLN-positive patients who may benefit from abemaciclib therapy without ALND.

Utility of Ki67 in guiding adjuvant abemaciclib therapy for patients with hormone receptor (HR)-positive, early breast cancer (EBC).

559 Background: The monarchE trial found that the addition of adjuvant abemaciclib to endocrine therapy in pts with lymph node (LN)+, HR+ EBC improved invasive disease-free survival in two pt cohorts: (1) ≥ 4 +LNs or 1-3 +LNs and Grade 3 disease or tumor ≥ 5 centimeters and (2) 1-3 +LNs and Ki67 ≥ 20%. The FDA approved adjuvant abemaciclib only in pts with HR+, HER2-negative, LN+ EBC with Ki67 ≥ 20%. The role of Ki67 as a predictive biomarker in this setting is unclear. ASCO guidelines recommend offering abemaciclib to pts who meet eligibility for either cohort and not restricting inclusion by Ki67. The objectives of this study were to (1) determine the association between Ki67 and the 21-gene recurrence score (RS), an established prognostic and predictive biomarker, using Ki67 cutoff ≥ 20% and (2) compare eligibility for adjuvant abemaciclib by FDA versus ASCO criteria. Methods: Women with HR+, HER2-negative EBC with 1-3 +LNs, diagnosed between 2018 and 2019, and who had available information on Ki67 and RS in the National Cancer Database were identified. Pts were categorized into Ki67 low ( &lt; 20%) or high ( ≥ 20%) based on cutoff used in the monarchE and stratified by RS of low-intermediate (0-25) or high (26-100). Stratified agreement between Ki67 and RS were assessed using the proportion of agreement and Kappa statistic. McNemar’s test was used to compare proportion of pts eligible for abemaciclib by FDA versus ASCO criteria. Results: 50,222 eligible women were included. 63.9% (n = 32,082) had Ki67 &lt; 20% and 36.1% (n = 18,140) Ki67 ≥ 20%. There was fair agreement (Kappa 0.21-0.40) between Ki67 and RS, which was statistically significant (Kappa = 0.272, p ≤ 0.001). Overall, using the FDA criteria for abemaciclib, 36.1% (n = 18,140) of patients would be eligible while based on ASCO criteria, 39.9% (n = 20,061) could be offered adjuvant abemaciclib (p &lt; 0.001). Among the 20,061 patients eligible for abemaciclib based on ASCO criteria, 57.4% (n = 11,513) were eligible due to Ki67 ≥ 20% alone, 9.6% (n = 1,921) due to Grade 3 alone, while 33.0% (n = 6,627) satisfied both Ki67 ≥ 20% and Grade 3 criteria. There were 33,789 patients who were post-menopausal with RS 0-25 and would be spared chemotherapy, yet 32.1% (n = 10,856) would be eligible for adjuvant abemaciclib based on FDA or ASCO criteria. Conclusions: There was only fair agreement between Ki67 and RS in patients with 1-3 +LNs based on Ki67 cutoff of 20%. Among patients with LN+ EBC, more patients would be offered abemaciclib using ASCO criteria compared to FDA criteria. Most were eligible for abemaciclib based on Ki67 alone, suggesting that Ki67 may provide additional information beyond tumor grade. In postmenopausal women with 1-3 +LNs, about 30% may be spared adjuvant chemotherapy based on the RS but still be sufficiently high risk to be considered for adjuvant abemaciclib.

Ki67 in Breast Cancer Assay: An Ad Hoc Testing Recommendation from the Canadian Association of Pathologists Task Force

Ki67, a marker of cellular proliferation, is commonly assessed in surgical pathology laboratories. In breast cancer, Ki67 is an established prognostic factor with higher levels associated with worse long-term survival. However, Ki67 IHC is considered of limited clinical use in breast cancer management largely due to issues related to standardization and reproducibility of scoring across laboratories. Recently, both the American Food and Drug Administration (FDA) and Health Canada have approved the use of abemaciclib (CDK4/6 inhibitor) for patients with HR+/HER2: high-risk early breast cancers in the adjuvant setting. Health Canada and the FDA have included a Ki67 proliferation index of ≥20% in the drug monograph. The approval was based on the results from monarchE, a phase III clinical trial in early-stage chemotherapy-naïve, HR+, HER2 negative patients at high risk of early recurrence. The study has shown significant improvement in invasive disease-free survival (IDFS) with abemaciclib when combined with adjuvant endocrine therapy at two years. Therefore, there is an urgent need by the breast pathology and medical oncology community in Canada to establish national guideline recommendations for Ki67 testing as a predictive marker in the context of abemaciclib therapy consideration. The following recommendations are based on previous IKWG publications, available guidance from the monarchE trial and expert opinions. The current recommendations are by no means final or comprehensive, and their goal is to focus on its role in the selection of patients for abemaciclib therapy. The aim of this document is to guide Canadian pathologists on how to test and report Ki67 in invasive breast cancer. Testing should be performed upon a medical oncologist's request only. Testing must be performed on treatment-naïve tumor tissue. Testing on the core biopsy is preferred; however, a well-fixed resection specimen is an acceptable alternative. Adhering to ASCO/CAP fixation guidelines for breast biomarkers is advised. Readout training is strongly recommended. Visual counting methods, other than eyeballing, should be used, with global rather than hot spot assessment preferred. Counting 100 cells in at least four areas of the tumor is recommended. The Ki67 scoring app developed to assist pathologists with scoring Ki67 proposed by the IKWG, available for free download, may be used. Automated image analysis is very promising, and laboratories with such technology are encouraged to use it as an adjunct to visual counting. A score of <5 or >30 is more robust. The task force recommends that the results are best expressed as a continuous variable. The appropriate antibody clone and staining protocols to be used may take time to address. For the time being, the task force recommends having tonsils/+pancreas on-slide control and enrollment in at least one national/international EQA program. Analytical validation remains a pending goal. Until the data become available, using local ki67 protocols is acceptable. The task force recommends participation in upcoming calibration and technical validation initiatives.

Abstract GS1-09: Abemaciclib plus endocrine therapy for HR+, HER2-, node-positive, high-risk early breast cancer: results from a pre-planned monarchE overall survival interim analysis, including 4-year efficacy outcomes

Abstract Background Adjuvant abemaciclib (a CDK4 and 6 inhibitor) combined with ET resulted in significant and clinically meaningful improvement in invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS) in patients (pts) with HR+, HER2-, node-positive, high risk EBC in the monarchE trial, and is an approved adjuvant therapy for these patients. Here we present efficacy results from a pre-specified overall survival interim analysis (OS IA2) which was planned to occur 2 years (yrs) after the primary outcome analysis. Methods Pts were randomized (1:1) to receive ET for up to 10 yrs +/- abemaciclib for 2 yrs (study treatment period). High-risk EBC was defined as either ≥4 positive axillary lymph nodes (ALN), or 1-3 ALN with either Grade 3 disease and/or tumor ≥5 cm (Cohort 1). While the proliferation biomarker Ki-67 was centrally assessed in all pts with available tissue sample, an additional smaller group of pts with 1-3+ ALN and central Ki-67 ≥20% as the only high-risk feature were included (Cohort 2). The intent-to-treat (ITT) population consisted of both Cohort 1 (5120 pts) and Cohort 2 (517 pts). Hazard ratios (HR) were estimated using Cox proportional hazard model. Results At a median follow-up of 42 months, all pts were off abemaciclib. IDFS and DRFS data illustrate a sustained benefit beyond the treatment period. In the ITT population, the HR for IDFS was 0.664 (95% CI: 0.578, 0.762) and DRFS was 0.659 (95% CI: 0.567, 0.767). At 4 yrs, this reflected an improvement in IDFS rates from 79.4% to 85.8% (absolute difference 6.4%), and in DRFS rates from 82.5% to 88.4% (absolute difference 5.9%). The continued separation of the curves was associated with an increase in absolute benefit in IDFS 4-year rates compared to 2-and 3-year IDFS rates (absolute difference 2.8% and 4.8% respectively). While OS remained immature, there was a lower number of deaths observed in the abemaciclib plus ET arm compared to the ET alone arm (157 [5.6%] vs 173 [6.1%], HR 0.929 [95% CI: 0.748, 1.153], p = 0.503), suggesting that the robust benefit in IDFS and DRFS began to translate into a numerically favorable OS HR. As previously described, within Cohort 1, a Ki-67 index of ≥20% was associated with a worse prognosis, but similar abemaciclib treatment effects were observed regardless of Ki-67 index. No new safety signals were observed. Conclusion The clinically meaningful benefit of adjuvant abemaciclib added to ET in HR+, HER2-, node-positive, high-risk EBC persists beyond completion of abemaciclib therapy, yielding an increase in absolute IDFS and DRFS benefit at 4 yrs. While OS remains immature at this time, the lower number of deaths in the abemaciclib arm compared to the ET arm suggest that a survival signal favoring abemaciclib is emerging. Citation Format: Stephen Johnston, Masakazu Toi, Joyce O’Shaughnessy, Priya Rastogi, Mario Campone, Patrick Neven, Chiun Sheng Huang, Jens Huober, Georgina Garnica Jaliffe, Irfan Cicin, Sara Tolaney, Matthew P. Goetz, Hope Rugo, Elżbieta Senkus, Laura Testa, Lucia Del Mastro, Chikako Shimizu, Ran Wei, Ashwin Shahir, Maria Munoz, Belen San Antonio, Valerie Andre, Nadia Harbeck, Miguel Martín. Abemaciclib plus endocrine therapy for HR+, HER2-, node-positive, high-risk early breast cancer: results from a pre-planned monarchE overall survival interim analysis, including 4-year efficacy outcomes [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 GS1-09.

CLRM-05 FEASIBILITY OF EVALUATING ABEMACICLIB NEUROPHARMACOKINETICS OF DIFFUSE MIDLINE GLIOMA USING INTRATUMORAL MICRODIALYSIS

INTRODUCTIONDiffuse midline gliomas are the most aggressive brain tumors of childhood and young adults, with documented 2 year survival rates of <10%. Treatment failure is due in part to the presence of the blood-brain barrier (BBB), which limits permeability of varied agents. Efforts to evaluate drug delivery across the BBB in midline gliomas have been restricted to post biopsy specimens. Intracerebral microdialysis sampling of cortical tissue has been shown to be a highly effective tool in determining neuropharmacokinetics in adult brain tumors. METHODSAll participants will take abemaciclib pre-operatively for 4.5 days at twice daily dosing. A maximally safe surgical resection for cortical high grade glioma or stereotactic needle biopsy for midline glioma will be performed in the OR and verified by brain CT. Continuous microdialysis sampling will be obtained over the course of the next 48 hours. We propose to evaluate 5 participants. RESULTSThis is a safety and feasibility study to evaluate tumor pharmacokinetics (PK) and pharmacodynamics (PD) of abemaciclib in recurrent high grade glioma and midline glioma participants in need of surgical resection or biopsy respectively. If intratumoral or PK brain dialysate sampling concentrations are >10nmol/L, or PD findings suggest CDK inhibition (decreased expression of Rb and/or topoIIα), then restart of abemaciclib therapy along with temozolomide will be administered for maintenance therapy post resection or biopsy. After every 3 cycles, repeat brain MRI’s will be obtained to evaluate treatment response and disease progression. Exploratory aims include catheter stability testing, tissue genomic sequencing and PDX modeling. CONCLUSIONWe propose a trial using clinical microdialysis, placed in diffuse midline glioma tissue post biopsy, as an experimental research tool, to assess CNS drug entry and targeted inhibition with abemaciclib. These studies will be the first of their kind focused on the dynamic nature of CNS drug delivery with the overall intent to inform future clinical therapies.

Venous and arterial thrombosis associated with abemaciclib therapy for metastatic breast cancer.

The CDK4/6 inhibitor abemaciclib is a mainstay of treatment for hormone receptor-positive breast cancer. However, increased venous thromboembolism (VTE) rates in multiple clinical trials resulted in a black-box warning for this agent. Thrombosis rates in unselected real-world populations receiving abemaciclib remain ill defined. A multicenter observational cohort study was conducted of patients with metastatic breast cancer receiving abemaciclib. The primary end point was thrombosis during treatment or within 30 days of discontinuation. Multivariable logistic models assessed predictors of VTE, and a multivariable Cox proportional hazards model assessed mortality. A total of 364 patients were included, with a median treatment duration of 5.5 months. Twenty-six patients developed 27 (7.4%) thrombotic events (17 VTE, nine arterial thrombosis, and one with both events). No baseline characteristics were associated with increased VTE risk in multivariable modeling. Patients developing VTE during therapy had a higher risk of death than those who did not (hazard ratio, 2.09; 95% CI, 1.07-4.13). Median survival in patients who developed VTE compared with those who did not was 9.6 vs 25.8 months, respectively. The rate of VTE and any thrombosis during abemaciclib therapy was 9.1 and 13.7 events per 100 person-years, respectively, which is notably higher than rates observed in clinical trials. In a real-world setting, abemaciclib was associated with a VTE rate approximately two-fold greater than the already elevated rates reported in the MONARCH trials. Patients developing thrombosis on abemaciclib had a significantly higher risk of death. Given these findings, studies evaluating the role of thromboprophylaxis in patients receiving abemaciclib are needed.