Pharmacotherapeutic group: Antineoplastic agents, protein kinases inhibitors, ATC code: L01EF03
Mechanism of action
Abemaciclib is a potent and selective inhibitor of cyclin-dependent kinases 4 and 6 (CDK4 and CDK6), and most active against Cyclin D1/CDK4 in enzymatic assays. Abemaciclib prevents retinoblastoma protein (Rb) phosphorylation, blocking cell cycle progression from the G1 to the S‑phase of cell division, leading to suppression of tumour growth. In oestrogen receptor‑positive breast cancer cell lines, sustained target inhibition with abemaciclib prevented rebound of Rb phosphorylation resulting in cell senescence and apoptosis. In vitro, Rb-negative and Rb-depleted cancer cell lines are generally less sensitive to abemaciclib. In breast cancer xenograft models, abemaciclib dosed daily without interruption at clinically relevant concentrations alone or in combination with anti-oestrogens resulted in reduction of tumour size.
Pharmacodynamic effects
In cancer patients, abemaciclib inhibits CDK4 and CDK6 as indicated by inhibition of phosphorylation of Rb and topoisomerase II alpha, which results in cell cycle inhibition upstream of the G1 restriction point.
Cardiac electrophysiology
The effect of abemaciclib on the QTcF interval was evaluated in 144 patients with advanced cancer. No large change (that is, > 20 ms) in the QTcF interval was detected at the mean observed maximal steady state abemaciclib concentration following a therapeutic dosing schedule.
In an exposure‑response analysis in healthy subjects at exposures comparable to a 200 mg twice‑daily dose, abemaciclib did not prolong the QTcF interval to any clinically relevant extent.
Clinical efficacy and safety
Early breast cancer
Randomised Phase 3 Study monarchE: Verzenios in combination with endocrine therapy
The efficacy and safety of Verzenios in combination with adjuvant endocrine therapy was evaluated in monarchE, a randomised, open label, two cohort, phase 3 study, in women and men with HR‑positive, HER2‑negative, node positive early breast cancer at high risk of recurrence. High risk of recurrence in Cohort 1 was defined by clinical and pathological features: either ≥ 4 pALN (positive axillary lymph nodes), or 1‑3 pALN and at least one of the following criteria: tumor size ≥ 5 cm or histological grade 3.
A total of 5 637 patients were randomised in a 1:1 ratio to receive 2 years of Verzenios 150 mg twice daily plus physician's choice of standard endocrine therapy, or standard endocrine therapy alone. Randomization was stratified by prior chemotherapy, menopausal status, and region. Men were stratified as postmenopausal. Patients had completed definitive locoregional therapy (with or without neoadjuvant or adjuvant chemotherapy). Patients must have recovered from the acute side effects of any prior chemotherapy or radiotherapy. A washout period of 21 days after chemotherapy and 14 days after radiotherapy prior to randomization was required. Patients were allowed to receive up to 12 weeks of adjuvant endocrine therapy prior to randomisation following the last non-endocrine therapy (surgery, chemotherapy or radiation). Adjuvant treatment with fulvestrant was not allowed as standard endocrine therapy. Patients with eastern cooperative oncology group (ECOG) Performance Status 0 or 1 were eligible. Patients with history of VTEs were excluded from the study. After the end of the study treatment period, in both treatment arms patients continued to receive adjuvant endocrine therapy for a cumulative duration of at least 5 years and up to 10 years, if medically appropriate. LHRH agonists were given when clinically indicated to pre- and perimenopausal women, and men.
Among the 5 637 randomised patients, 5 120 were enrolled in Cohort 1, representing 91 % of the ITT population. In Cohort 1, patient demographics and baseline tumour characteristics were balanced between treatment arms. The median age of patients enrolled was approximately 51 years (range, 22‑89 years), 15 % of patients were 65 or older, 99 % were women, 71 % were Caucasian, 24 % were Asian, and 5 % Other. Forty three percent of patients were pre- or perimenopausal. Most patients received prior chemotherapy (36 % neoadjuvant, 62 % adjuvant), and prior radiotherapy (96 %). Initial endocrine therapy received by patients included letrozole (39 %), tamoxifen (31 %), anastrozole (22 %), or exemestane (8 %).
Sixty-five percent of the patients had 4 or more positive lymph nodes, 41 % had Grade 3 tumour, and 24 % had pathological tumour size ≥ 5 cm at surgery.
The primary endpoint was invasive disease-free survival (IDFS) in ITT population defined as the time from randomization to the first occurrence of ipsilateral invasive breast tumour recurrence, regional invasive breast cancer recurrence, distant recurrence, contralateral invasive breast cancer, second primary non-breast invasive cancer, or death attributable to any cause. Key secondary endpoint was distant relapse free survival (DRFS) in ITT population defined as time from randomization to the first occurrence of distant recurrence, or death attributable to any cause.
The primary objective of the study was met at the pre‑planned interim analysis (16 Mar 2020 cut-off). A statistically significant improvement in IDFS was observed in patients who received Verzenios plus endocrine therapy versus endocrine therapy alone in the ITT population. At the time of the subsequent final overall survival (OS) analysis (15 July 2025 cut-off) a statistically significant improvement in OS was also observed in patients who received Verzenios plus endocrine therapy versus endocrine therapy alone in the ITT population. The approval was granted for the large subpopulation, Cohort 1.
At the final OS analysis all patients in Cohort 1 were off the 2-year study treatment period and the median duration of follow-up was 76 months (6.3 years).
Efficacy results in Cohort 1 are summarised in Table 9, Figure 1 and Figure 2.
Table 9. monarchE: Summary of efficacy data (Cohort 1 population)
| | Verzenios plus endocrine therapy N = 2 555 | Endocrine therapy alone N = 2 565 |
| Invasive disease-free survival (IDFS) | | |
| Number of patients with event (n, %) | 512 (20.0) | 678 (26.4) |
| Hazard ratio (95 % CI) | 0.726 (0.648, 0.815) |
| IDFS at 84 months (%, 95 % CI) | 77.0 (75.0, 78.8) | 70.1 (68.0, 72.1) |
| Distant relapse free survival (DRFS) | | |
| Number of patients with an event (n, %) | 448 (17.5) | 589 (23.0) |
| Hazard ratio (95 % CI) | 0.736 (0.651, 0.832) |
| DRFS at 84 months (%, 95 % CI) | 79.5 (77.6, 81.2) | 74.0 (72.0, 75.9) |
| Overall Survival (OS) | | |
| Number of events, n (%) | 286 (11.2) | 344 (13.4) |
| Hazard Ratio (95% CI) | 0.835 (0.713, 0.977) |
Abbreviation: CI = confidence interval.
Data cut-off date 15 July 2025
Figure 1. monarchE: Kaplan-Meier plot of IDFS (Investigator assessment, Cohort 1 population)
Abbreviations: IDFS = invasive disease-free survival; N = number of patients in the population.
Data cut-off date 15 July 2025
Figure 2. monarchE: Kaplan-Meier plot of OS (Cohort 1 population)
Abbreviations: ET = endocrine therapy; OS = overall survival; N = number of patients in the population.
Data cut-off date 15 Jul 2025
Benefit was observed across patient subgroups defined by geographic region, menopausal status and prior chemotherapy within Cohort 1.
Advanced or metastatic breast cancer
Randomised Phase 3 Study MONARCH 3: Verzenios in combination with aromatase inhibitors
The efficacy and safety of Verzenios in combination with an aromatase inhibitor (anastrozole or letrozole) was evaluated in MONARCH 3, a randomised, double‑blind, placebo‑controlled phase 3 study in women with HR positive, HER2 negative locally advanced or metastatic breast cancer who had not received prior systemic therapy in this disease setting. Patients were randomised in a 2:1 ratio to receive Verzenios 150 mg twice daily plus a non-steroidal aromatase inhibitor given daily at the recommended dose versus placebo plus a non-steroidal aromatase inhibitor according to the same schedule. The primary endpoint was investigator-assessed progression-free survival (PFS) evaluated according to RECIST 1.1; key secondary efficacy endpoints included objective response rate (ORR), clinical benefit rate (CBR) and overall survival (OS).
The median age of patients enrolled was 63 years (range 32 ‑ 88). Approximately 39 % of patients had received chemotherapy and 44 % had received antihormonal therapy in the (neo)adjuvant setting. Patients with prior (neo)adjuvant endocrine therapy must have completed this therapy at least 12 months before study randomisation. The majority of patients (96 %) had metastatic disease at baseline. Approximately 22 % of patients had bone-only disease, and 53 % patients had visceral metastases.
The study met its primary endpoint of improving PFS. Primary efficacy results are summarised in Table 10 and Figure 3.
Table 10. MONARCH 3: Summary of efficacy data (Investigator assessment, intent-to-treat population)
| | Verzenios plus aromatase inhibitor | Placebo plus aromatase inhibitor |
| Progression-free survival | N = 328 | N = 165 |
| Investigator assessment, number of events (%) | 138 (42.1) | 108 (65.5) |
| Median [months] (95 % CI) | 28.18 (23.51, NR) | 14.76 (11.24, 19.20) |
| Hazard ratio (95 % CI) and p-value | 0.540 (0.418, 0.698), p = 0.000002 |
| Independent radiographic review, number of events (%) | 91 (27.7) | 73 (44.2) |
| Median [months] (95 % CI) | NR (NR, NR) | 19.36 (16.37, 27.91) |
| Hazard ratio (95 % CI) and p-value | 0.465 (0.339, 0.636); p < 0.000001 |
| Objective response rateb [%] (95 % CI) | 49.7 (44.3, 55.1) | 37.0 (29.6, 44.3) |
| Duration of response [months] (95 % CI) | 27.39 (25.74, NR) | 17.46 (11.21, 22.19) |
| Objective response for patients with measurable diseasea | N = 267 | N = 132 |
| Objective response rateb [%] (95 % CI) | 61.0 (55.2, 66.9) | 45.5 (37.0, 53.9) |
| Complete response, (%) | 3.4 | 0 |
| Partial response, (%) | 57.7 | 45.5 |
| Clinical benefit ratec (measurable disease) [%] (95 % CI) | 79.0 (74.1, 83.9) | 69.7 (61.9, 77.5) |
a Measurable disease defined per RECIST version 1.1
b Complete response + partial response
c Complete response + partial response + stable disease for ≥ 6 months
N = number of patients; CI = confidence interval; NR = not reached.
Figure 3. MONARCH 3: Kaplan-Meier plot of progression-free survival (Investigator assessment, intent-to-treat population)
These results correspond to a clinically meaningful reduction in the risk of disease progression or death of 46 % for patients treated with abemaciclib plus an aromatase inhibitor.
OS was not mature at the final PFS analysis (93 events observed across the two arms). The HR was 1.057 (95 % CI: 0.683, 1.633), p = 0.8017.
A series of prespecified subgroup PFS analyses showed consistent results across patient subgroups including age (< 65 or ≥ 65 years), disease site, disease setting (de novo metastatic vs recurrent metastatic vs locally advanced recurrent), presence of measurable disease, progesterone receptor status, and baseline ECOG performance status. A reduction in the risk of disease progression or death was observed in patients with visceral disease, (HR of 0.567 [95 % CI: 0.407, 0.789]), median PFS 21.6 months versus 14.0 months; in patients with bone-only disease (HR of 0.565 [95 % CI: 0.306, 1.044]); and in patients with measurable disease (HR of 0.517 [95 % CI: 0.392, 0.681]).
At the first OS interim analysis, 197 events were observed across the two arms and the HR was 0.786 (95 % CI: 0.589, 1.049).
At the second OS interim analysis, 255 events were observed across the two arms and the HR was 0.754 (95 % CI: 0.584, 0.974).
The results from the Final OS analysis were not statistically significant (summarised in Table 11 and Figure 4).
Table 11.: MONARCH 3: Summary of Overall Survival data (Intent-to-Treat Population)
| | Verzenios plus Anastrozole or Letrozole | Placebo plus Anastrozole or Letrozole |
| Overall survival | N = 328 | N = 165 |
| Number of events (n, %) | 198 (60.4) | 116 (70.3) |
| Median OS [months] (95% CI) | 66.81 (59.21, 74.83) | 53.72 (44.75, 59.34) |
| Hazard ratio (95% CI) | 0.804 (0.637, 1.015) |
Abbreviations: N = number of patients; CI = confidence interval; ITT = intent-to-treat; OS = overall survival.
Analyses for OS in patients with visceral disease showed an OS HR of 0.758 (95% CI: 0.558, 1.030). Median OS was 63.72 months in the abemaciclib plus AI arm and 48.82 months in the placebo plus AI arm. Similar to the ITT population, the results were not statistically significant.
Figure 4. MONARCH 3: Kaplan-Meier plot of overall survival (Intent-to-treat population)
Randomised Phase 3 Study MONARCH 2: Verzenios in combination with fulvestrant
The efficacy and safety of Verzenios in combination with fulvestrant was evaluated in MONARCH 2, a randomised, double‑blind, placebo‑controlled phase 3 study in women with HR positive, HER2 negative locally advanced or metastatic breast cancer. Patients were randomised in a 2:1 ratio to receive Verzenios 150 mg twice daily plus fulvestrant 500 mg at intervals of one month, with an additional 500 mg dose given two weeks after the initial dose, versus placebo plus fulvestrant according to the same schedule. The primary endpoint was investigator-assessed PFS evaluated according to RECIST 1.1; key secondary efficacy endpoints included ORR, CBR and OS.
The median age of patients enrolled was 60 years (range, 32 ‑ 91 years). In each treatment arm the majority of patients were white, and had not received chemotherapy for metastatic disease. 17 % of patients were pre/perimenopausal on ovarian suppression with a GnRH agonist. Approximately 56 % patients had visceral metastases. Approximately 25 % of patients had primary endocrine resistance (progression on endocrine therapy within the first 2 years of adjuvant endocrine therapy or within the first 6 months of first line endocrine therapy for metastatic breast cancer) and for the majority, endocrine resistance developed later. 59 % of patients had most recent endocrine therapy in the (neo)adjuvant setting, and 38 % in metastatic setting.
The study met its primary endpoint of improving PFS. Primary efficacy results are summarised in Table 12 and Figure 5.
Table 12. MONARCH 2: Summary of efficacy data (Investigator assessment, intent-to-treat population)
| | Verzenios plus fulvestrant | Placebo plus fulvestrant |
| Progression-free survival | N = 446 | N = 223 |
| Investigator assessment, number of events (%) | 222 (49.8) | 157 (70.4) |
| Median [months] (95 % CI) | 16.4 (14.4, 19.3) | 9.3 (7.4, 12.7) |
| Hazard ratio (95 % CI) and p-value | 0.553 (0.449, 0.681), p = 0.0000001 |
| Independent radiographic review, number of events (%) | 164 (36.8) | 124 (55.6) |
| Median [months] (95 % CI) | 22.4 (18.3, NR) | 10.2 (5.8, 14.0) |
| Hazard ratio (95 % CI) and p-value | 0.460 (0.363, 0.584); p < 0.000001 |
| Objective response rateb [%] (95 % CI) | 35.2 (30.8, 39.6) | 16.1 (11.3, 21.0) |
| Duration of response [months] (95 % CI) | NR (18.05, NR) | 25.6 (11.9, 25.6) |
| Objective response for patients with measurable diseasea | N = 318 | N = 164 |
| Objective response rateb [%] (95 % CI) | 48.1 (42.6, 53.6) | 21.3 (15.1, 27.6) |
| Complete response, (%) | 3.5 | 0 |
| Partial response, (%) | 44.7 | 21.3 |
| Clinical benefit ratec (measurable disease) [%] (95 % CI) | 73.3 (68.4, 78.1) | 51.8 (44.2, 59.5) |
a Measurable disease defined per RECIST version 1.1
b Complete response + partial response
c Complete response + partial response + stable disease for ≥ 6 months
N = number of patients; CI = confidence interval; NR = not reached.
Figure 5. MONARCH 2: Kaplan-Meier plot of progression-free survival (Investigator assessment, intent-to-treat population)
These results correspond to a clinically meaningful reduction in the risk of disease progression or death of 44.7 % for patients treated with Verzenios plus fulvestrant. Verzenios plus fulvestrant prolonged progression‑free survival with neither a clinically meaningful, or significant detriment to health‑related quality of life.
A series of prespecified subgroup PFS analyses showed consistent results across patient subgroups including age (< 65 or ≥ 65 years), race, geographic region, disease site, endocrine therapy resistance, presence of measurable disease, progesterone receptor status, and menopausal status. A reduction in the risk of disease progression or death was observed in patients with visceral disease, (HR of 0.481 [95 %CI: 0.369, 0.627]), median PFS 14.7 months versus 6.5 months; in patients with bone‑only disease (HR of 0.543 [95 % CI: 0.355, 0.833]); patients with measurable disease (HR of 0.523 [95 % CI: 0.412, 0.644]). In patients who were pre/perimenopausal, the hazard ratio was 0.415 (95 % CI: 0.246, 0.698); in patients who were progesterone receptor negative, the HR was 0.509 (95 % CI: 0.325, 0.797).
In a sub-population with locally advanced or metastatic disease that had not received prior endocrine therapy, the PFS was also consistent.
At the pre‑specified interim OS analysis (20 June 2019 cut‑off), the ITT population showed a statistically significant improvement in patients receiving Verzenios plus fulvestrant compared with those receiving placebo plus fulvestrant. The OS results are summarized in Table 13.
Table 13. MONARCH 2: Summary of overall survival data (Intent-to-treat population)
| | Verzenios plus fulvestrant | Placebo plus fulvestrant |
| Overall survival | N = 446 | N = 223 |
| Number of events (n, %) | 211 (47.3) | 127 (57.0) |
| Median OS [months] (95 % CI) | 46.7 (39.2, 52.2) | 37.3 (34.4, 43.2) |
| Hazard ratio (95 % CI) | 0.757 (0.606, 0.945) |
| p‑value | 0.0137 |
N = number of patients; CI = confidence interval; OS = overall survival
Analyses for OS by stratification factors showed OS HR of 0.675 (95 % CI: 0.511, 0.891) in patients with visceral disease, and 0.686 (95 % CI: 0.451, 1.043) in patients with primary endocrine resistance.
At the pre‑specified final OS analysis (18 March 2022 cut‑off), 440 events were observed across the 2 arms. The improvement in OS previously observed at the interim OS analysis (20 June 2019 cut‑off) was maintained in the abemaciclib plus fulvestrant arm compared to the placebo plus fulvestrant arm, with a HR of 0.784 (95 % CI: 0.644, 0.955). Median OS was 45.8 months in the abemaciclib plus fulvestrant arm and 37.25 months in the placebo plus fulvestrant arm. The OS results are presented in Figure 6.
Figure 6. MONARCH 2: Kaplan-Meier plot of overall survival (Intent-to-treat population)
Paediatric population
The licencing authority has waived the obligation to submit the results of studies with Verzenios in all subsets of the paediatric population in breast cancer (see section 4.2 for information on paediatric use).
The efficacy and safety of Verzenios in combination with irinotecan and temozolomide was evaluated in Study J1S-MC-JP04, a multicentre, randomised, open-label, phase 2 study in participants with relapsed or refractory Ewing sarcoma. The primary endpoint was progression-free survival (PFS) assessed by a blinded independent review committee. 46 participants, 3 to 35 years of age, were randomised to receive Verzenios plus irinotecan and temozolomide or irinotecan and temozolomide in a 2:1 ratio. 58.7 % of patients (27 patients) were < 18 years of age. 45 participants were treated in 21-day cycles until disease progression or having met other discontinuation criteria. No difference in PFS was observed with the addition of Verzenios. The median PFS was 2.8 months in patients treated with Verzenios in combination irinotecan and temozolomide and 2.9 months in patients treated with irinotecan and temozolomide (HR 0.64 [95% CI: 0.28, 1.45]).