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Palazestrant

Phase 3

Breast Cancer | Small molecule | Oncology |Olema Pharmaceuticals, Inc.|Last Updated: May 15, 2026

Success Probability
Approval Probability 71%
TA Base Rate26%
Adjusted LOA41%
ML RiskLOW_RISK
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Market & Valuation
rNPV $3.2B
Market Size $9.4B
Revenue Basis $1.6B
Competitors 6
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Trial Design
RandomizedDouble-BlindCONTROLLEDDMCBiomarker
Total Trials3
Total Enrollment1,570
FDA Designations
No designations recorded
Clinical Trials (3)
NCT IDTitlePhaseStatusEnrollmentVelocityDesignStartCompletionLast UpdatedSitesCountries
NCT07085767Palazestrant in Combination With Ribociclib for the First-line Treatment of ER+/HER2- Advanced Breast CancerPHASE3 RECRUITING 1,000 — — Nov 3, 2025Jan 1, 2032May 15, 2026124 United States, Australia +20
NCT06016738OP-1250 (Palazestrant) vs. Standard of Care for the Treatment of ER+/HER2- Advanced Breast CancerPHASE3 RECRUITING 510 — — Nov 16, 2023Sep 30, 2027Mar 13, 2026233 United States, Argentina +24
NCT05266105A Phase 1 Study of Oral OP-1250 in Combination With Palbociclib in HR+/HER2- Breast Cancer PatientsPHASE1 ACTIVE NOT_RECRUITING 60 — — Dec 10, 2021Mar 1, 2026Nov 24, 20258 Australia
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Study Endpoints
Primary Endpoints
Progression-Free Survival (PFS)
From Date of Randomization until Disease Progression or Death Due to Any Cause (estimated as up to 3.5 years)

To compare PFS, based on a local investigator assessment, between investigational (palazestrant with ribociclib + letrozole-matching placebo) and control (letrozole with ribociclib + palazestrant-matching placebo) arms.

Dose-Selection Part: Incidence of adverse events
From Date of Randomization up to 16 weeks

To evaluate the number of participants with adverse events

Dose-Selection Part: Incidence of dose reduction
From Date of Randomization up to 16 weeks

To evaluate the number of participants reducing the dose of palazestrant

Dose-Selection Part: Incidence of drug discontinuation
From Date of Randomization up to 16 weeks

To evaluate the number of participants discontinuing palazestrant

Trial: Progression-Free Survival (PFS)
From Date of Randomization until Disease Progression or Death Due to Any Cause (estimated as up to 2 years)

To compare PFS, based on a Blinded Independent Review Committee (BIRC) assessment, between arms of OP-1250 and standard-of-care treatment. This will be assessed separately in populations of ESR1-mutation detected and ESR1-mutation not detected participants.

Incidence of Dose Limiting Toxicities
From Cycle 1 Day 1 through C1 Day 28
Characterization and Incidence in Adverse Events and Serious Adverse Events
From initial inform consent date through 30 days post last dose
Plasma levels of OP-1250 and Palbociclib
Up to 9 months
Secondary Endpoints
Overall Survival (OS)
From Date of Randomization until Death Due to Any Cause (estimated as up to 5.5 years)
Progression Free Survival (PFS)
From Date of Randomization until Disease Progression or Death Due to Any Cause (estimated as up to 3.5 years)
Overall response Rate (ORR)
From Date of Randomization until Tumor Response (estimated as up to 3.5 years)
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Study Design & Arms
AllocationRANDOMIZED
MaskingTRIPLE
ModelPARALLEL
PurposeTREATMENT
Treatment Arms
ArmTypeDescription
PalazestrantEXPERIMENTALParticipants will receive palazestrant, ribociclib and letrozole-matching placebo
LetrozoleACTIVE_COMPARATORParticipants will receive letrozole, ribociclib and palazestrant-matching placebo
Palazestrant (OP-1250)EXPERIMENTALParticipants will receive Palazestrant
Standard of Care Endocrine TherapyACTIVE_COMPARATORParticipants will receive Investigator's choice of one of the Standard of Care drugs (fulvestrant, anastrozole, letrozole, or exemestane)
Dose EscalationEXPERIMENTALThis portion of the study will evaluate the safety and pharmacology of a range of OP-1250 doses administered daily with Palbociclib in subjects with advanced and/or metastatic hormone receptor (HR)-positive, HER2-negative breast cancer
Dose ExpansionEXPERIMENTALThis portion of the study further explores the clinical activity, safety and pharmacology of OP-1250 in combination with Palbociclib and estimates preliminary data of anti-tumor efficacy
Interventions
NameTypeDescription
PalazestrantDRUGParticipants will be treated with palazestrant 90 mg once daily on a 4-week (28-day) cycle.
Letrozole-matching placeboDRUGParticipants will be treated with letrozole-matching placebo once daily on a 4-week (28 day) cycle
RibociclibDRUGParticipants will be treated with ribociclib 600 mg once daily on Days 1-21 of a 4-week (28 day) cycle.
LetrozoleDRUGParticipants will be treated with letrozole 2.5 mg once daily on a 4-week (28-day) cycle
Palazestrant matching-placeboDRUGParticipants will be treated with palazestrant-matching placebo once daily on a 4-week (28-day) cycle
FulvestrantDRUGParticipants will be treated with fulvestrant on C1D1, C1D15, and then on Day 1 of every subsequent 4 week (28 day) cycle
AnastrozoleDRUGParticipants will be treated with anastrozole once daily on a 4 week (28 day) cycle
ExemestaneDRUGParticipants will be treated with exemestane once daily on a 4 week (28 day) cycle
PalbociclibDRUGPalbociclib is an approved CDK 4/6 Inhibitor drug
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Eligibility Criteria
Age Range18 Years — N/A
SexALL
Healthy VolunteersNo
Study Sites124

Inclusion Criteria: * Adult female or male participants. * ER+, HER2- locally advanced or metastatic breast cancer that is not amenable to curative therapy. * Evaluable disease (measurable disease per RECIST 1.1 or bone-only disease). * De novo advanced breast cancer or with disease recurrence occu...

Countries:United StatesAustraliaAustriaBelgiumCanadaCzechiaFranceGermanyGreeceHong KongHungaryItalyMalaysiaNetherlandsPolandPortugalRomaniaSouth KoreaSpainTaiwanThailandUnited KingdomArgentinaBrazilBulgariaMexicoPuerto Rico
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Competitive Landscape -Breast Cancer 408 trials
CompanyTickerTrialsLead PhaseDrugs
Merck & Co., Inc.MRK12PHASE3Pembrolizumab, Paclitaxel, Doxorubicin, Epirubicin, Cyclophosphamide
AstraZeneca PLCAZN47PHASE3Fulvestrant, Capivasertib, Trastuzumab Deruxtecan, Paclitaxel, Trastuzumab
Gilead Sciences, Inc.GILD13PHASE3Sacituzumab Govitecan-hziy, Eribulin, Capecitabine Product, Gemcitabine, Vinorelbine
Eli Lilly and CompanyLLY27PHASE3Abemaciclib, Standard Adjuvant Endocrine Therapy, Imlunestrant, Tamoxifen, Anastrozole
BioNTech SE Sponsored ADRBNTX7PHASE3DB-1303/BNT323, T-DM1, Capecitabine, Paclitaxel, Nab-paclitaxel
Novartis AG Sponsored ADRNVS30PHASE3Ribociclib, Alpelisib, Fulvestrant, Trastuzumab, Pertuzumab
Olema Pharmaceuticals, Inc.OLMA5PHASE3Palazestrant, Fulvestrant, Anastrozole, Letrozole, Exemestane
Pfizer Inc.PFE34PHASE3ARV-471, Fulvestrant, PF-07220060, letrozole, abemaciclib
BeOne Medicines Ltd. Sponsored ADRONC6PHASE3BGB-43395, Letrozole, Abemaciclib, Palbociclib, Ribociclib
Jazz Pharmaceuticals Public Limited CompanyJAZZ3PHASE3Zanidatamab, Trastuzumab, Eribulin, Vinorelbine, Gemcitabine
Celcuity Inc.CELC3PHASE3Gedatolisib, Palbociclib, Fulvestrant, Alpelisib, Arm A: Gedatolisib + Palbociclib + Fulvestrant
Relay Therapeutics, Inc.RLAY2PHASE3RLY-2608, Capivasertib, Fulvestrant, Palbociclib, Ribociclib
GSK plc Sponsored ADRGSK2PHASE3Niraparib
Greenwich LifeSciences, Inc.GLSI1PHASE3GLSI-100
Bristol-Myers Squibb CompanyBMY5PHASE2Iza-bren, Nab-paclitaxel, Paclitaxel, Capecitabine, Carboplatin
BriaCell Therapeutics CorpBCTX2PHASE3SV-BR-1-GM, Cyclophosphamide, Interferon infiltration of the inoculation site, Retifanlimab, Treatment of Physician's Choice
Incyte CorporationINCY4PHASE2Ruxolitinib, Capecitabine, Regorafenib, Pembrolizumab, Axatilimab
Natera, Inc.NTRA3PHASE2Discontinuation of the anti-HER2 maintenance therapy
Puma Biotechnology, Inc.PBYI3PHASE2Neratinib, Loperamide, Colesevelam, Alisertib, Endocrine therapy
Immutep Ltd Sponsored ADRIMMP1PHASE2eftilagimod alpha, Paclitaxel
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Recent Changes (Last 90 Days)
LOWMay 26, 2026NCT06016738primaryCompletionDate: changed
LOWMay 26, 2026NCT07085767primaryCompletionDate: changed
LOWMay 26, 2026NCT05266105primaryCompletionDate: changed
LOWMay 24, 2026NCT06016738studyFirstPostDate: changed
LOWMay 24, 2026NCT07085767studyFirstPostDate: changed
LOWMay 24, 2026NCT05266105studyFirstPostDate: changed