Pharmacokinetic Model of Abemaciclib: Correlation With Severe Diarrhea as the Primary Toxicity Endpoint in Patients With Localized Hormone Receptor-positive Breast Cancer (DOSABEMA)

Remarkable progress has recently been made in the treatment of locally advanced, hormone receptor-positive, HER2-negative breast cancer with a high risk of recurrence, thanks to the addition of abemaciclib to endocrine therapy. This combination has led to a significant improvement in invasive disease-free survival. However, despite the combination's acceptable safety profile, 38% of patients experience grade 3 or higher diarrhea, and 23% experience grade 3 or higher neutropenia. This toxicity can lead to the premature discontinuation of treatment, limiting the benefits of this molecule. As with all oral therapies, the pharmacokinetics of abemaciclib lie at the intersection of efficacy and toxicity and can be modified by several external factors.

The hypothesis of the study is that abemaciclib's toxicity is correlated with its plasma levels and that its concentration is modified by certain patient characteristics. To this end, a pharmacokinetic model of abemaciclib could be developed using a prospective, multicenter, real-world blood dosage study. This study will describe the relationship between abemaciclib concentration and diarrhea and severe neutropenia, as classified by CTCAE, as well as potential clinical and drug interactions.

It is hoped that this model demonstrates the importance of monitoring abemaciclib concentrations. This could lead to a therapeutic trial in which the abemaciclib dose is adjusted according to concentration to limit toxicity while maintaining efficacy.

Study Overview

• Status: Not yet recruiting
• Conditions: Breast Cancer; Abemaciclib; Abemaciclib-related Diarrhea
• Intervention / Treatment: Biological: Blood samples for PK; Other: Questionnaire

• Study Type: Interventional
• Enrollment (Estimated): 235
• Phase: Phase 4

Contacts and Locations

• Study Contact: Name: Matthieu BAINAUD, MD; Phone Number: 05 49 44 44 44; Email: matthieu.bainaud@chu-poitiers.fr
• Study Contact Backup: Name: Celine ABONNEAU, Project manager

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Women ≥ 18 years old
• Having breast cancer of all histologies combined
• Type Luminal A or B with positive hormone receptors (>10% expression for estrogen receptor and/or progesterone receptor) and HER2 negative or low epidermal growth receptor (according to GEFPICS1 definition)
• Stage 2 or stage 3 according to the international classification, translated into the SENORIF recommendation
• Having undergone complete excision surgery (R0 on the invasive tumor and/or on the ductal entity in situ) after neoadjuvant chemotherapy or not
• Defined as high risk of recurrence according to the Monarch-E study, at initial diagnosis of the disease: either ≥ 4 affected axillary lymph nodes (≥N2 involvement), or 1-3 affected axillary lymph nodes (≥N1 involvement) associated with an Elston Ellis grade 3 or a tumor ≥ 5 cm
• Initiation of adjuvant treatment with abemaciclib in combination with hormone therapy
• Patient ECOG performance status between 0 and 2
• Patients with a neutrophil count (NCC) defined as normal prior to the first dose of abemaciclib, i.e., an absolute NCC ≥ 1500/ mm3 (≥ 1.5 x 109/L) without granulocyte colony-stimulating factor (GCSF) injection within 15 days prior to laboratory testing, as well as a platelet count ≥ 100,000/mm3 and a hemoglobin level ≥ 8g/dL.
• Patient with the psychological and mental capacity to understand the protocol and sign the consent form independently
• Must be affiliated with the social security system or receive benefits through a third party
• Have signed the study consent form after reading the information sheet

Exclusion Criteria:

• Hypersensitivity to any of the excipients listed in section 6.1 of the abemaciclib (Verzenios) SPC
• History of treatment with an anti-CDK4/6 (palbociclib, ribociclib, abemaciclib) for any indication
• History of invasive cancer of any histology within the last 2 years, except for superficial skin tumors, not considered to be in complete remission
• Presence of functional or inflammatory colorectal disease (Crohn's disease, ulcerative colitis) causing chronic diarrhea (as defined by the WHO as at least 3 bowel movements per day and/or liquid stools for at least 1 month)
• Patient who has undergone total gastrectomy or suffers from short bowel syndrome
• Patient unable to sign the consent form for societal reasons (illiteracy) or somatic reasons (central nervous system disease).
• Persons benefiting from enhanced protection, namely minors, persons deprived of their liberty by judicial or administrative decision, persons staying in a health or social care institution, adults under legal protection, and finally patients in emergency situations.
• Pregnant or breastfeeding women, women of childbearing age who are not using highly effective contraceptive methods (e.g., double-barrier contraception) during treatment and for at least 3 weeks after stopping treatment (The duration of contraception required for concomitant treatments, if any, should also be taken into account.)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Patient treated with abemaciclib; All new patients who benefit from the addition of abemaciclib to adjuvant hormone therapy and who meet the inclusion criteria may be included in the study. This single-arm study involves enrolled patients undergoing blood tests and completing self-administered questionnaires at various points during their treatment.	Biological: Blood samples for PK; Three additional blood tubes will be collected during routine biological tests.; Other: Questionnaire; EQ-5D-5L

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Determine the relationship between the probability of occurrence of a severe diarrheal adverse event and plasma exposure to abemaciclib and its metabolites in patients with RH+HER2- breast cancer at high risk of recurrence receiving adjuvant abemaciclib	The probability of severe diarrhea (grades 2, 3, and 4 according to CTCAE v5.0) occurring based on exposure to abemaciclib and its metabolites (M2 and M20) will be characterized by a joint mixed-effects model combining longitudinal, pharmacokinetic (continuous type), and toxicity data (survival type).	From enrollment to 6 months of treatment

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Determine the relationship between the occurrence of severe neutropenic adverse events and plasma exposure to abemaciclib and its metabolites in patients with HR+, HER2- breast cancer at high risk of recurrence who are receiving adjuvant abemaciclib	The probability of severe neutropenia (grades 3 and 4 according to the current CTCAE) occurring based on exposure to abemaciclib and its metabolites (M2 and M20) will be characterized by a joint mixed-effects model combining longitudinal pharmacokinetic (continuous) and pharmacodynamic (neutrophil concentration, continuous) data. pharmacokinetic (continuous type) and pharmacodynamic (concentration of neutrophils, continuous type) data.	From enrollment to 6 months of treatment
Develop a joint pharmacokinetic/pharmacodynamic (PK/PD) mixed-effects model that includes data on abemaciclib and metabolite concentrations, neutrophil counts, and severe diarrhea	The mixed-effects PK/PD model was validated using standard diagnostic tools, such as data fit diagnostic plots, visual predictive checks, estimation accuracy, and shrinkage.	From enrollment to 6 months of treatment
Evaluate the free fraction (fu) of abemaciclib concentrations at different protocol treatment times in the target population (only at Poitiers University Hospital)	Free concentrations of abemaciclib will only be measured for patients enrolled at Poitiers University Hospital. The "fu" of abemaciclib concentrations will be modeled within the mixed-effects PK/PD model and any correlation with clinical-biological covariates will be evaluated. This exploratory analysis will only be performed on patients enrolled at Poitiers University Hospital for pre-analytical technical reasons. The technique has only been validated on the mass spectrometer in the pharmacology department at Poitiers University Hospital.	From enrollment to 6 months of treatment

Collaborators and Investigators

• Sponsor: Poitiers University Hospital

Study record dates

Study Major Dates

• Study Start (Estimated): April 1, 2026
• Primary Completion (Estimated): April 1, 2029
• Study Completion (Estimated): April 1, 2029

Study Registration Dates

• First Submitted: March 18, 2026
• First Submitted That Met QC Criteria: March 18, 2026
• First Posted (Actual): March 24, 2026

Study Record Updates

• Last Update Posted (Actual): April 1, 2026
• Last Update Submitted That Met QC Criteria: March 26, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Skin Diseases; Breast Diseases; Skin and Connective Tissue Diseases; Breast Neoplasms; Health Care Quality, Access, and Evaluation; Investigative Techniques; Epidemiologic Methods; Specimen Handling; Clinical Laboratory Techniques; Diagnostic Techniques and Procedures; Diagnosis; Punctures; Surgical Procedures, Operative; Data Collection; Health Care Evaluation Mechanisms; Quality of Health Care; Public Health; Environment and Public Health; Surveys and Questionnaires; Blood Specimen Collection
• Other Study ID Numbers: 2025-521696-31-00 (Ctis)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No