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Palazestrant

Phase 3

Breast Cancer | Small molecule | Oncology |Olema Pharmaceuticals, Inc.|Last Updated: Jul 17, 2026

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Trial Design
RandomizedDouble-BlindCONTROLLEDDMC
Total Trials3
Total Enrollment1,570
FDA Designations
No designations recorded
Clinical trial landscape

Palazestrant · 4 trials · 8 indications

Phase 3 2Phase 1 2
NCT07085767Palazestrant in Combination With Ribociclib for the First-line Treatment of ER+/HER2- Advanced Breast CancerBreast Cancer
RECRUITING1,000 Analytics
NCT06016738OP-1250 (Palazestrant) vs. Standard of Care for the Treatment of ER+/HER2- Advanced Breast CancerBreast Cancer
RECRUITING510 Analytics
PHASE3RECRUITING
Palazestrant in Combination With Ribociclib for the First-line Treatment of ER+/HER2- Advanced Breast Cancer
Breast CancerUnlock trial analytics
PHASE3RECRUITING
OP-1250 (Palazestrant) vs. Standard of Care for the Treatment of ER+/HER2- Advanced Breast Cancer
Breast CancerUnlock trial analytics
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.

Dose Limiting Toxicities (DLTs)
The first 28 days of treatment

To determine the maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D), and/ or recommended dose expansion (RDE) of palazestrant when administered with ribociclib (Treatment Group 1), alpelisib (Treatment Group 2), or everolimus (Treatment Group 3), or atirmociclib (Treatment Group 4). The incidence of DLTs will be assessed in the Dose Escalation part (Part 1) of the study.

Characterize the incidence, nature and severity of treatment emergent adverse events (TEAEs) and serious adverse events (SAEs) of palazestrant when administered with ribociclib, alpelisib, everolimus, or atirmociclib.
Up to 30 days after last dose of study drug(s) treatment

Characterize the incidence, nature and severity of TEAEs and SAEs of palazestrant when administered with ribociclib (Treatment Group 1), alpelisib (Treatment Group 2), everolimus (Treatment Group 3), or atirmociclib (Treatment Group 4) according to NCI-CTCAE version 5.0.

Pharmacokinetics (PK) of palazestrant when administered with ribociclib (Treatment Group 1) or alpelisib (Treatment Group 2), everolimus (Treatment Group 3), or atirmociclib (Treatment Group 4) .
Every 28 days

To assess the PK of palazestrant (and potential metabolites) in combination with ribociclib (Treatment Group 1), alpelisib (Treatment Group 2), everolimus (Treatment Group 3), or atirmociclib (Treatment Group 4). Plasma levels of palazestrant will be assessed at predefined intervals to establish PK parameters (including: Cmax, Cmin, Tmax, AUC, and t1⁄2 as data permit) and palazestrant trough concentration at steady state).

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)
Palazestrant with RibociclibEXPERIMENTALTreatment Group 1: Palazestrant in combination with ribociclib (KISQALI®, Novartis Pharmaceuticals Corporation).
Palazestrant with AlpelisibEXPERIMENTALTreatment Group 2: Palazestrant in combination with alpelisib (PIQRAY®, Novartis Pharmaceuticals Corporation)
Palazestrant with EverolimusEXPERIMENTALTreatment Group 3: Palazestrant in combination with everolimus
Palazestrant with AtirmociclibEXPERIMENTALTreatment Group 4: Palazestrant in combination with atirmociclib
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
AlpelisibDRUGAll subjects in Treatment Group 2 will receive palazestrant in combination with alpelisib.
EverolimusDRUGAll subjects in Treatment Group 3 will receive palazestrant in combination with everolimus.
AtirmociclibDRUGAll subjects in Treatment Group 4 will receive palazestrant in combination with atirmociclib.
PalbociclibDRUGPalbociclib is an approved CDK 4/6 Inhibitor drug
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Eligibility Criteria
Age Range18 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites167

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 404 trials

Top 20 of 97 competitors

CompanyTickerTrialsLead PhaseDrugs
AstraZeneca PLCAZN47PHASE3Fulvestrant, Capivasertib
Merck & Co., Inc.MRK12PHASE3Pembrolizumab, Paclitaxel, Doxorubicin, Epirubicin, Cyclophosphamide
Eli Lilly and CompanyLLY27PHASE3Abemaciclib, Standard Adjuvant Endocrine Therapy
BioNTech SE Sponsored ADRBNTX7PHASE3DB-1303/BNT323, T-DM1
Gilead Sciences, Inc.GILD13PHASE3Sacituzumab Govitecan-hziy, Eribulin, Capecitabine Product, Gemcitabine, Vinorelbine
Novartis AG Sponsored ADRNVS30PHASE3Ribociclib
Olema Pharmaceuticals, Inc.OLMA5PHASE3Palazestrant, Fulvestrant, Anastrozole, Letrozole, Exemestane
Pfizer Inc.PFE34PHASE3ARV-471, Fulvestrant
BeOne Medicines Ltd. Sponsored ADRONC5PHASE3BGB-43395, Letrozole, Abemaciclib, Palbociclib, Ribociclib
Jazz Pharmaceuticals Public Limited CompanyJAZZ3PHASE3Zanidatamab, Trastuzumab, Eribulin, Vinorelbine, Gemcitabine
Celcuity Inc.CELC3PHASE3Gedatolisib, Palbociclib, Fulvestrant, Alpelisib
Relay Therapeutics, Inc.RLAY2PHASE3RLY-2608, Capivasertib, Fulvestrant
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
Natera, Inc.NTRA3PHASE2Discontinuation of the anti-HER2 maintenance therapy
Puma Biotechnology, Inc.PBYI3PHASE2Neratinib, Loperamide, Colesevelam
Immutep Ltd Sponsored ADRIMMP1PHASE2eftilagimod alpha, Paclitaxel
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Recent Changes (Last 90 Days)
LOWJul 17, 2026NCT07085767lastUpdatePostDate: changed
LOWJul 17, 2026NCT07085767lastUpdatePostDate: changed
LOWJun 16, 2026NCT07085767lastUpdatePostDate: changed
LOWJun 16, 2026NCT07085767lastUpdatePostDate: changed
LOWJun 16, 2026NCT07085767lastUpdatePostDate: changed
LOWMay 26, 2026NCT06016738primaryCompletionDate: changed
LOWMay 26, 2026NCT05508906primaryCompletionDate: changed
LOWMay 26, 2026NCT07085767primaryCompletionDate: changed
LOWMay 26, 2026NCT05266105primaryCompletionDate: changed
LOWMay 24, 2026NCT05508906studyFirstPostDate: changed
LOWMay 24, 2026NCT07085767studyFirstPostDate: changed
LOWMay 24, 2026NCT06016738studyFirstPostDate: changed
LOWMay 24, 2026NCT05266105studyFirstPostDate: changed