Table of contents

• Clinical trial overview
• Breast cancer studies
• Other cancers studied
• Trial phases and what they mean
• Main endpoints used in the trials
• Who may join these studies
• Treatment combinations and comparisons

Clinical trial overview

The trial data show that Abemaciclib is being studied in many cancer settings, with the largest group of studies in breast cancer.^[1][2] Most trials are interventional studies, which means people are assigned to a treatment plan so researchers can compare results.^[1]

These studies are mostly authorised, and they include both early-stage and advanced disease.^[1][2] Some trials also include special groups such as older adults, men, women, children, and young adults.^[6][13][13]

Breast cancer studies

Many trials focus on hormone receptor-positive and HER2-negative breast cancer, which is a common breast cancer type studied with hormone-based treatment.^[1][2] Some studies are in the adjuvant setting, meaning treatment after surgery to lower the risk of the cancer coming back.^[1]

For example, NCT03155997 studies endocrine therapy with or without Abemaciclib after surgery in people with high-risk, node-positive, early-stage HR+/HER2- breast cancer, and its main endpoint is invasive disease-free survival.^[1] NCT04565054 also studies Abemaciclib with standard adjuvant endocrine therapy in intermediate to high-risk early breast cancer, with invasive disease-free survival since randomization as the main outcome.^[2]

Several studies look at advanced or metastatic breast cancer, which means cancer that has spread or cannot be removed by surgery.^[3][5][7] These trials often compare Abemaciclib combinations with other treatments, such as fulvestrant, letrozole, or other CDK4/6 inhibitors.^[3][5][7]

Some breast cancer trials are more specific. NCT05696626 studies women and men with locally advanced or metastatic breast cancer with an ESR1 mutation, which is a change in a gene that may affect treatment response, and measures progression-free survival.^[3] NCT06365788 studies Abemaciclib plus bicalutamide in androgen receptor-positive triple-negative breast cancer, and its main endpoint is disease control rate at 16 weeks.^[9]

There are also studies in special breast cancer groups such as older patients, brain metastases, and rare ovarian tumors with estrogen receptor positivity.^[8][13][17] NCT05386108 studies elacestrant with Abemaciclib in people with brain metastases from ER-positive, HER2-negative breast cancer, and it first checks the recommended Phase 2 dose before measuring objective response rate.^[17]

Other cancers studied

Abemaciclib is also being studied outside breast cancer.^{[4][10][12][15]} NCT05288166 studies Abemaciclib with abiraterone plus prednisone in men with high-risk metastatic hormone-sensitive prostate cancer, and the main endpoint is radiographic progression-free survival.^[4]

NCT05440786 studies Abemaciclib with irinotecan and temozolomide in people with Ewing’s sarcoma, and the main endpoint is progression-free survival by blinded independent review.^[15] NCT02152631 studied Abemaciclib in previously treated KRAS-mutated lung cancer, with overall survival as the main outcome.^[12]

Other trials include high-grade glioma after radiotherapy, low-grade serous ovarian cancer, adult-type granulosa cell tumor, and rare epithelial ovarian tumors.^[10][11][14] These studies show that researchers are testing whether Abemaciclib may help in different tumor types, not only breast cancer.^[10][11][14]

Trial phases and what they mean

The studies range from Phase 1 to Phase 4, and some are low-intervention or phase 1/2 studies.^{[1][6][7][12][15][18]}

Phase 1 studies mainly focus on safety, tolerability, dose-limiting toxicities, and finding a recommended dose.^[7][12][17] For example, NCT05386108 and 2025-521128-31-00 both include safety and dose-finding parts.^[7][12]

Phase 2 and Phase 3 studies usually test whether Abemaciclib improves cancer control compared with another treatment or a control group.^{[1][2][3][4][5]}

One Phase 4 study in prostate cancer looks at whether Abemaciclib can be added safely and whether it improves radiographic progression-free survival in a later-stage research setting.^[18]

Main endpoints used in the trials

The most common endpoint is progression-free survival, which means the time before the cancer gets worse or the patient dies.^{[3][4][5][8][15]} Many trials use this endpoint because it helps show whether a treatment delays cancer growth.^[3][5]

Other important endpoints include invasive disease-free survival, overall survival, objective response rate, and disease control rate.^{[1][12][14][16]} Some studies also measure ctDNA change, Ki67 change, residual cancer burden, or time to treatment failure.^{[10][13][16][13]}

Safety is also a major part of several trials, especially Phase 1 studies, where researchers track adverse events, serious adverse events, lab results, ECG results, and dose-limiting toxicities.^[7][16][13]

Who may join these studies

Eligibility depends on the cancer type and the stage of disease.^[1][3][4] Some trials include people after surgery with early breast cancer, while others include people with locally advanced, unresectable, metastatic, or recurrent disease.^[1][3][10]

Some studies are limited to specific groups, such as postmenopausal women, pre- and postmenopausal women and men, older patients, children and young adults, or men with prostate cancer.^{[3][4][6][10][12]}

Several trials also require prior treatment history, such as having already received endocrine therapy, a CDK4/6 inhibitor, or chemotherapy, depending on the study question.^[3][5][7][9]

Treatment combinations and comparisons

Abemaciclib is often studied in combination with endocrine therapy, which is hormone-based treatment used in hormone receptor-positive cancer.^[1][2][5][8]

It is also tested with other medicines such as fulvestrant, letrozole, tamoxifen, abiraterone, prednisone, bicalutamide, temozolomide, irinotecan, elacestrant, giredestrant, capivasertib, and ARV-471.^{[3][4][7][9][11][14][15][17]}

Some studies compare Abemaciclib combinations with another CDK4/6 inhibitor, a placebo, or standard treatment, so researchers can see whether the Abemaciclib arm works better or has a different safety profile.^{[2][5][6][18]}