FDA clears Inluriyo plus Verzenio for ESR1-mutated advanced breast cancer — companion Guardant360 CDx also approved.

The Food and Drug Administration on 18 September 2026 approved imlunestrant (Inluriyo) in combination with abemaciclib (Verzenio) for adults with estrogen receptor (ER)-positive, HER2-negative, ESR1-mutated advanced or metastatic breast cancer, as detected by an FDA-authorized test, with disease progression following at least one line of endocrine therapy, according to the FDA Drugs@FDA announcement opened for this pack. Soft FLAG: Inluriyo and Verzenio are both manufactured by Eli Lilly and Company, the FDA page states. The agency also approved the Guardant360 CDx assay as a companion diagnostic to identify patients with breast cancer harbouring ESR1 mutations for treatment with the combination.

The mechanism is a selective estrogen receptor degrader (SERD) paired with a CDK4/6 inhibitor after progression on prior endocrine therapy. Soft FLAG: “SERD” framing appears in secondary Medscape coverage opened for colour; the FDA page itself states the indication and trial design without using that marketing label in the opened text — prefer FDA wording in hed/dek body claims.

Efficacy as the FDA page states it: evidence comes from EMBER-3 (NCT04975308), a randomized, open-label, active-controlled, multicenter trial that enrolled 874 adults with ER-positive, HER2-negative, locally advanced or metastatic breast cancer previously treated with an aromatase inhibitor alone or with a CDK4/6 inhibitor. Patients were randomized 1:1:1 to imlunestrant, investigator’s choice endocrine therapy (fulvestrant or exemestane), or imlunestrant plus abemaciclib. Soft FLAG: the FDA states that while PFS for the combination versus imlunestrant monotherapy was statistically significant in the overall population, a PFS improvement was not demonstrated for imlunestrant monotherapy versus investigator’s choice in the overall or ESR1m-not-detected populations, “indicating that the benefit was only observed in the ESR1m population.” Soft FLAG: in an exploratory subgroup of 159 patients with ESR1-mutated tumors, median PFS was 11.1 months (95% CI 7.4–13.7) on the combination versus 5.5 months (95% CI 3.8–7.2) on imlunestrant alone (HR 0.53, 95% CI 0.35–0.80); ORR 35% vs 15%. Soft FLAG: overall survival data were immature at interim analysis (35% of deaths in the ESR1-mutated subset).

Recommended dosage on the FDA page: imlunestrant 400 mg orally once daily on an empty stomach (at least two hours before food or one hour after); abemaciclib 150 mg orally twice daily with or without food, until progression or unacceptable toxicity. Soft FLAG: prescribing information carries warnings for embryo-fetal toxicity (imlunestrant) and for diarrhea, neutropenia, ILD/pneumonitis, hepatotoxicity, VTE and embryo-fetal toxicity (abemaciclib).

Named actors beyond the agency page: Eli Lilly manufactures both Inluriyo and Verzenio; Guardant Health’s Guardant360 CDx is the authorised companion diagnostic for ESR1 mutation detection in this indication, the FDA states. Soft FLAG: blood ctDNA analysis using Guardant360 CDx was limited to specific ESR1 mutations in the ligand-binding domain, per the FDA write-up.

Randomization strata in EMBER-3, as FDA lists them: previous CDK4/6-inhibitor treatment, presence of visceral metastasis, and geographic region. Soft FLAG: patients eligible for a PARP inhibitor were excluded. Soft FLAG: the major efficacy outcome for the combination was investigator-assessed PFS by RECIST v1.1 in the overall population comparing imlunestrant plus abemaciclib to imlunestrant monotherapy; OS and ORR were other measures.

Soft FLAG: this review used the Assessment Aid, a voluntary applicant submission to facilitate FDA assessment, the agency notes — process colour, not an efficacy claim.

Soft FLAG: Medscape (21 Sep) notes a rival camizestrant combination received accelerated approval about two weeks earlier and frames sequencing debates — competitive colour, attribute if used; not required for the FDA clearance fact pattern.

What to watch without mood: mature OS from EMBER-3; uptake of Guardant360 CDx ESR1 testing at progression; labelled use confined to the ESR1-mutated population as FDA framed it.

Floor: FDA 18 Sep 2026 — Inluriyo (imlunestrant) + Verzenio (abemaciclib) for ER+/HER2−/ESR1m advanced or metastatic breast cancer after ≥1 endocrine line; Guardant360 CDx companion; EMBER-3 exploratory ESR1m PFS 11.1 vs 5.5 mo (HR 0.53); OS immature (FDA).