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Phase 3 Study of RLY-2608 + Fulvestrant vs Capivasertib + Fulvestrant as Treatment for Locally Advanced or Metastatic PIK3CA-mutant HR+/HER2- Breast Cancer

A Phase 3 Open-Label Randomized Study Assessing the Efficacy and Safety of RLY-2608 + Fulvestrant Versus Capivasertib + Fulvestrant as Treatment for PIK3CA-mutant Hormone Receptor Positive, Human Epidermal Growth Factor Receptor 2 Negative (HR+/HER2-) Locally Advanced or Metastatic Breast Cancer Following Recurrence or Progression On or After Treatment With a CDK4/6 Inhibitor

Status
Recruiting
Phases
Phase 3
Study type
Interventional
Source
ClinicalTrials.gov
Registry ID
NCT06982521
Acronym
ReDiscover-2
Enrollment
540
Registered
2025-05-21
Start date
2025-08-26
Completion date
2031-12-31
Last updated
2026-04-02

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

PIK3CA Mutation, HER2- Negative Breast Cancer, Hormone Receptor Positive Tumor, Breast Cancer, Metastatic Breast Cancer, Advanced Breast Cancer

Brief summary

This is a global, multicenter, open-label, randomized Phase 3 study comparing the efficacy and safety of RLY-2608 + fulvestrant to capivasertib + fulvestrant for the treatment of patients with HR+/HER2- ABC with PIK3CA mutation following recurrence or progression on or after treatment with a CDK4/6 inhibitor.

Interventions

400 mg orally BID administered daily on a 28-day treatment cycle

DRUGCapivasertib

400mg orally BID administered on an intermittent weekly dosing schedule. Patients will dose on Days 1 through 4 each week of a 28-day treatment cycle

DRUGFulvestrant

500 mg intramuscularly administered on Cycle 1 Day 1, Day 15, and Day 1 of each subsequent cycle (28-day treatment cycle)

Sponsors

Relay Therapeutics, Inc.
Lead SponsorINDUSTRY

Study design

Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE

Eligibility

Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No

Inclusion criteria

* Patient has ECOG performance status of 0-1 * One or more known primary oncogenic PIK3CA mutation(s) * Adult females, pre- and/or post-menopausal, and adult males. Pre-menopausal (and peri-menopausal) women can be enrolled if amenable to treatment with a gonadotropin-releasing hormone (GnRH) agonist. Patients are to have commenced treatment with a GnRH agonist at least 4 weeks prior to randomization and must be willing to continue on it for the duration of the study. * Histologically or cytologically confirmed diagnosis of HR+/HER2- locally advanced or metastatic breast cancer (ABC) with radiological or objective evidence of recurrence or progression; locally advanced disease must not be amenable to resection with curative intent * Measurable disease per RECIST v1.1 or evaluable bone-only disease. * Must have radiological evidence of progression on or after previous treatment for HR+/HER2- ABC with: 1. At least 1 and no more than 2 lines of endocrine therapy (ET) in the (neo)adjuvant setting with recurrence on or within 12 months of completion or in the ABC setting 2. 1 prior line of CDK4/6 inhibitor therapy in one of the following settings: 1. CDK4/6 inhibitor + ET in the ABC setting 2. CDK4/6 inhibitor therapy in the adjuvant setting if progression occurred during or within 12 months of completion of adjuvant CDK4/6 inhibitor with ET 3. Patients who progressed during or within 12 months of completion of adjuvant CDK4/6 inhibitor and after receiving CDK4/6 inhibitor therapy in the advanced setting are considered to have had \>1 prior line of CDK4/6 inhibitor and are not eligible

Exclusion criteria

* Prior treatment with any of the following: 1. CDK2 or selective CDK4 inhibitors or any investigational therapies targeting cyclin dependent kinases 2. PIK3, AKT, or mTOR inhibitors or any agent whose mechanism of action is the inhibit the PIK3/AKT/mTOR pathway 3. Immunotherapy 4. Antibody drug conjugates * Type 1 diabetes, or Type 2 diabetes requiring antihyperglycemic medication, or fasting plasma glucose ≥ 140 mg/dL, or glycosylated hemoglobin (HbA1c) ≥7.0% (≥ 53 mmol/mol). * Clinically significant, uncontrolled cardiovascular disease * Any factors that increase the risk of QTc prolongation or risk of arrhythmic events * Known active uncontrolled or symptomatic CNS metastases associated with progressive neurological symptoms or requiring ongoing corticosteroids or anticonvulsants for symptomatic control * Past medical history of interstitial lung disease, drug-induced interstitial lung disease, radiation pneumonitis which required steroid treatment, or any evidence of clinically active interstitial lung disease * History of hypersensitivity to fulvestrant or drugs in a similar class as fulvestrant, RLY-2608, or capivasertib, including their excipients * Known activating AKT mutations, loss-of-function PTEN mutations, or loss of PTEN expression resulting in oncogenic pathway activation downstream of PI3K

Design outcomes

Primary

MeasureTime frame
Progression-Free Survival (PFS) within the overall and kinase population by blinded independent central review (BICR)The time from date of randomization until radiographic progression per RECIST v1.1, or death due to any cause, up to approximately 77 months

Secondary

MeasureTime frame
Overall Survival (OS) within the overall and kinase populationsThe time from randomization to the date of death by any cause, up to approximately 77 months
PFS by Investigator within the overall and kinase populationsThe time from date of randomization until radiographic progression per RECIST v1.1, or death due to any cause, up to approximately 77 months
Objective Response Rate (ORR) within the overall and kinase populationsUp to approximately 77 months
Duration of Response (DOR) within the overall and kinase populationsUp to approximately 77 months
Clinical Benefit Rate (CBR) within the overall and kinase populationsUp to approximately 77 months
Occurrence/frequency of Adverse Events (AEs) and its relationship to the study drugs (safety and tolerability) within the overall and kinase populationsUp to approximately 77 months
Plasma concentrations of RLY-2608 (and its metabolites as appropriate)Approximately every 2 weeks in Cycle 1 (4-week cycle) and during Cycles 2 and 3
European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire (EORTC QLQ-C30) scale/item scores including change from baseline and time to deterioration within overall and kinase populationsUp to approximately 77 months
EORTC Quality of Life Questionnaire Breast Cancer-Specific Module (EORTC QLQ-BR23) scale/item scores including change from baseline and time to deterioration within the overall and kinase populationsUp to approximately 77 months
Health state utility data for economic evaluation by EQ-5D-5L health state utility index within the overall and kinase populationsUp to approximately 77 months

Countries

Australia, Austria, Belgium, Brazil, Canada, Czechia, Denmark, France, Germany, Greece, Hong Kong, Italy, Netherlands, Poland, Singapore, South Korea, Spain, Taiwan, United States

Contacts

CONTACTRelay Therapeutics, Inc
ClinicalTrials@relaytx.com617-322-0731

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Apr 5, 2026