Trial reportBreast cancer research : BCR2025
Palazestrant, a novel oral Complete Estrogen Receptor Antagonist (CERAN) and Selective Estrogen Receptor Degrader (SERD), in patients with ER+/HER2- advanced or metastatic breast cancer: phase 1/2 study results.
Trial report in Breast cancer research : BCR, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. It is linked to trial NCT04505826 (A Phase I Dose Escalation and Dose Expansion and Phase II Monotherapy Open-label, First-in-Human, Multicenter Study of OP-1250 in Adult Subjects With Advanced and/or Metastatic Hormone Receptor), which is not on this map. Cited by 6 papers.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
A Phase I Dose Escalation and Dose Expansion and Phase II Monotherapy Open-label, First-in-Human, Multicenter Study of OP-1250 in Adult Subjects With Advanced and/or Metastatic Hormone Receptor (HR)-Positive, HER2-negative Breast Cancer
Who cites it
6 citing papers in PubMed.
- Breast Cancer: Epidemiology, Molecular Classification, Diagnostics and Evolving Treatment Paradigms.Molecules (Basel, Switzerland) · 2026Review
- The use of pharmacodynamic results for recommended phase II decision making in oncology clinical trials.Cancer chemotherapy and pharmacology · 2026Review
- Review
- Caution over haste: why novel endocrine therapy in early lines should wait in Estrogen receptor positive human epidermal growth factor receptor 2 negative breast cancer.Breast cancer research : BCR · 2026Review
- Review
- OPERA-01: a phase III study of palazestrant for ER+, HER2- advanced breast cancer after CDK4/6 inhibitor therapy.Future oncology (London, England) · 2026Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
16 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundEndocrine resistance is a major challenge in treating patients with ER+ /HER2- metastatic breast cancer (MBC) necessitating a switch from endocrine therapy to more toxic therapies. Mutations in ESR1 constitute a key mechanism of resistance to endocrine therapy in ER+ /HER2- BC. Therapies that overcome endocrine resistance are needed. Palazestrant is a novel oral complete estrogen receptor (ER) antagonist (CERAN) and selective ER degrader (SERD) belonging to a new class of ER-targeting agents that completely blocks estrogen-induced transcriptional activity, regardless of ESR1 mutation status. This first-in-human, open-label, multicenter, phase 1/2 dose-escalation/expansion study was designed to determine the recommended phase 2 dose (RP2D) and to evaluate safety, pharmacokinetics, and antitumor activity of palazestrant in patients with ER+ /HER2- MBC with disease progression on prior treatment.
methodsAdults with ER+ /HER2‒ MBC who received ≥ 1 prior line of endocrine therapy for advanced disease and ≤ 2 prior chemotherapy regimens for metastatic disease were eligible. Patients received once-daily oral palazestrant (30-300 mg) in 28-day cycles until progression or intolerable toxicity.
resultsThis study enrolled 146 patients. No dose-limiting toxicities were observed at doses up to 300 mg/day palazestrant. Confirmed partial responses were observed with 60 and 120 mg/day palazestrant. Both doses showed similar and tolerable safety profiles, favorable pharmacokinetics, and steady-state plasma concentrations above the predicted threshold for complete ER inhibition. Greater clinical benefit at palazestrant 120 mg/day (46%) versus 60 mg/day (19%) led to selection of 120 mg/day as RP2D and study expansion dose. At 120 mg/day, the median progression-free survival was 4.8 months (95% CI, 3.5-7.1) overall and 5.6 months (95% CI, 4.8-NE) among patients with cancers with ESR1 mutations. Most treatment-emergent adverse events (TEAEs) were grade 1-2. The most common TEAEs were nausea (62.8%), vomiting (29.1%), and fatigue (25.6%). The most common grade ≥ 3 TEAE was transient neutropenia (10.5%) managed by dose interruption and reduction.
conclusionsPalazestrant demonstrated a manageable safety profile, with antitumor activity observed in patients with heavily pretreated cancers with wild-type and ESR1-mutated BC. These data support the ongoing phase 3 study evaluating palazestrant in patients with ER+ /HER2 - MBC.
trial registrationClinicalTrials.gov, NCT04505826 . Registered August 6, 2020.
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