{"entity":{"id":"postmonarch","kind":"trial","name":"postMONARCH","aka":[],"tldr":"Continuing CDK4/6 blockade with a different drug after the first one fails gives a small but real benefit.","summary":"postMONARCH, trial NCT05169567 sponsored by Eli Lilly and reported in 2024, showed that continuing CDK4/6 blockade with a different drug after the first one fails gives a small but real benefit in HR-positive, HER2-negative advanced breast cancer. It randomised 368 women who had progressed on a CDK4/6 inhibitor plus endocrine therapy to abemaciclib or placebo with fulvestrant and met its primary progression-free survival endpoint, the first placebo-controlled phase 3 to show benefit from CDK4/6 inhibition beyond progression, with the largest gains in tumours without ESR1 or PIK3CA mutations. OnCo links it to CDK4/6 as a target, abemaciclib and fulvestrant. The absolute gain is modest, and whether biomarkers can pick the patients who benefit is the open question.","status":"positive","asOf":"2026-09-07","links":[{"label":"ClinicalTrials.gov NCT05169567","url":"https://clinicaltrials.gov/study/NCT05169567"}],"tags":[],"related":[],"cancers":["breast-hr-positive","hr-positive-metastatic-post-cdk46"],"sections":[],"technologies":["cdk46-inhibitor"],"targets":["cdk4-6"],"drugs":["abemaciclib"],"companies":["eli-lilly"],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"nct":"NCT05169567","phase":"3","setting":"HR+/HER2- advanced breast cancer after progression on CDK4/6 + endocrine therapy: abemaciclib + fulvestrant vs placebo + fulvestrant","sponsor":"Eli Lilly","result":"PFS 6.0 vs 5.3 months, HR 0.73.","started":"2022-03-11","startedType":"actual","yearReported":2024,"enrolled":368,"enrolledBasis":"registry","outcomes":[{"endpoint":"Progression-free survival","primary":true,"unit":"months","arms":[{"name":"Abemaciclib + fulvestrant","n":182,"value":6},{"name":"Placebo + fulvestrant","n":186,"value":5.3}],"hr":0.73,"ci":[0.57,0.95],"p":"0.017","source":"https://ascopubs.org/doi/10.1200/JCO-24-02086"}],"replication":"Contrasts with the negative PACE and PALMIRA trials of continuing palbociclib; MAINTAIN (ribociclib switch) was positive in phase 2."},"route":"/trials/postmonarch/","neighbours":{"cancer":[{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"},{"id":"hr-positive-metastatic-post-cdk46","kind":"cancer","name":"HR-positive metastatic breast cancer after CDK4/6 inhibitors","route":"/cancers/hr-positive-metastatic-post-cdk46/"}],"technology":[{"id":"cdk46-inhibitor","kind":"technology","name":"CDK4/6 inhibitors","route":"/technologies/cdk46-inhibitor/"}],"target":[{"id":"cdk4-6","kind":"target","name":"CDK4/6","route":"/targets/cdk4-6/"}],"drug":[{"id":"abemaciclib","kind":"drug","name":"Abemaciclib","route":"/drugs/abemaciclib/"},{"id":"fulvestrant","kind":"drug","name":"Fulvestrant","route":"/drugs/fulvestrant/"}],"company":[{"id":"eli-lilly","kind":"company","name":"Eli Lilly (incl. Loxo)","route":"/companies/eli-lilly/"}],"roadmap":[{"id":"hormonal-therapy-roadmap","kind":"roadmap","name":"Hormonal therapy roadmap: removing the ovaries → tamoxifen → oral degraders switched by a blood test","route":"/roadmaps/hormonal-therapy-roadmap/"}]}}