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RLY-2608

Phase 3

PIK3CA Mutation | Small molecule | Oncology |Relay Therapeutics, Inc.|Last Updated: May 8, 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
RandomizedCONTROLLEDDMCBiomarker
Total Trials2
Total Enrollment1,470
FDA Designations
No designations recorded
Clinical Trials (2)
NCT IDTitlePhaseStatusEnrollmentVelocityDesignStartCompletionLast UpdatedSitesCountries
NCT06982521Phase 3 Study of RLY-2608 + Fulvestrant vs Capivasertib + Fulvestrant as Treatment for Locally Advanced or Metastatic PIK3CA-mutant HR+/HER2- Breast CancerPHASE3 RECRUITING 540 — — Aug 26, 2025Dec 31, 2031May 8, 2026158 United States, Argentina +20
NCT05216432First-in-Human Study of Mutant-selective PI3Kα Inhibitor, RLY-2608, as a Single Agent in Patients With Advanced Solid Tumors and in Combination With Endocrine Therapy +/- a CDK4/6 or CDK4 Inhibitor in Patients With Advanced Solid Tumors or Advanced Breast CancerPHASE1 RECRUITING 930 — — Dec 8, 2021Apr 30, 2027Sep 22, 202537 United States, Australia +3
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Study Endpoints
Primary Endpoints
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
Determination of maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D) of RLY-2608 as a single agent
Cycle 1 (4-week cycle) of treatment for MTD and at the end of every cycle (4-week cycles) for RP2D until study discontinuation, approximately 24 months
Determination of maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D) of RLY-2608 in combination with fulvestrant
Cycle 1 (4-week cycle) of treatment for MTD and at the end of every cycle (4-week cycles) for RP2D until study discontinuation, approximately 24 months
Determination of maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D) of RLY-2608 in combination with fulvestrant and a CDK 4/6 inhibitor (palbociclib, ribociclib), and in combination with CDK4 inhibitor (PF-07220060) and fulvestrant
Cycle 1 (4-week cycle) of treatment for MTD and at the end of every cycle (4-week cycles) for RP2D until study discontinuation, approximately 24 months
Number of patients with adverse events and serious adverse events of RLY-2608 as a single agent
Every cycle (4-week cycles) until study discontinuation, approximately 24 months
Number of patients with adverse events and serious adverse events of RLY-2608 in combination with fulvestrant
Every cycle (4-week cycles) until study discontinuation, approximately 24 months
Number of patients with adverse events and serious adverse events of RLY-2608 in combination with fulvestrant and a CDK 4/6 inhibitor (palbociclib, ribociclib), and in combination with CDK4 inhibitor (PF-07220060) and fulvestrant
Every cycle (4-week cycles) until study discontinuation, approximately 24 months
Secondary Endpoints
Overall Survival (OS) within the overall and kinase populations
The time from randomization to the date of death by any cause, up to approximately 77 months
PFS by Investigator within the overall and kinase populations
The 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 populations
Up to approximately 77 months
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Study Design & Arms
AllocationRANDOMIZED
MaskingNONE
ModelPARALLEL
PurposeTREATMENT
Treatment Arms
ArmTypeDescription
RLY-2608 + fulvestrantEXPERIMENTALRLY-2608 + fulvestrant combination for participants with HR+/HER2- advanced breast cancer
capivasertib + fulvestrantACTIVE_COMPARATORcapivasertib + fulvestrant combination for participants with HR+/HER2- advanced breast cancer
RLY-2608 for patients with unresectable or metastatic solid tumorsEXPERIMENTALMultiple doses of RLY-2608 for oral administration.
RLY-2608 + fulvestrant combination for HR+ HER2- locally advanced or metastatic breast cancerEXPERIMENTALOral dose of RLY-2608 in addition to fulvestrant as determined during Part 1 Dose Escalation.
RLY-2608+fulvestrant+palbo125mg for HR+HER2- locally advanced metastatic breast cancerEXPERIMENTALOral dose of RLY-2608 in addition to fulvestrant and palbociclib 125mg as determined during Part 1 Dose Escalation.
RLY-2608+fulvestrant+ribo400mg for HR+HER2- locally advanced metastatic breast cancerEXPERIMENTALOral dose of RLY-2608 in addition to fulvestrant and ribociclib 400mg as determined during Part 1 Dose Escalation.
RLY-2608+fulvestrant+ribo600mg for HR+HER2- locally advanced metastatic breast cancerEXPERIMENTALOral dose of RLY-2608 in addition to fulvestrant and ribociclib 600mg as determined during Part 1 Dose Escalation.
RLY-2608+fulvestrant+PF-07220060 100 mg for HR+ HER2- locally advanced or metastatic breast cancerEXPERIMENTALOral dose of RLY-2608 in addition to fulvestrant and PF-07220060 100 mg as determined during Part 1 Dose Escalation
RLY-2608+fulvestrant+PF-07220060 300 mg for HR+ HER2- locally advanced or metastatic breast cancerEXPERIMENTALOral dose of RLY-2608 in addition to fulvestrant and PF-07220060 300 mg as determined during Part 1 Dose Escalation
Interventions
NameTypeDescription
RLY-2608DRUG400 mg orally BID administered daily on a 28-day treatment cycle
CapivasertibDRUG400mg 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
FulvestrantDRUG500 mg intramuscularly administered on Cycle 1 Day 1, Day 15, and Day 1 of each subsequent cycle (28-day treatment cycle)
Palbociclib 125mgDRUG125mg palbociclib is taken orally once daily for 28-day cycles that include 21 days of treatment followed by 7 days off treatment.
Ribociclib 400mgDRUG400mg ribociclib is taken orally once daily for 28-day cycles that include 21 days of treatment followed by 7 days off treatment.
Ribociclib 600mgDRUG600mg ribociclib is taken orally once daily for 28-day cycles that include 21 days of treatment followed by 7 days off treatment.
PF-07220060 100mgDRUGPF-07220060 100 mg is taken orally twice daily at the same time with RLY-2608 during each 28-day cycle.
PF-07220060 300 mgDRUGPF-07220060 300 mg is taken orally twice daily at the same time with RLY-2608 during each 28-day cycle.
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Eligibility Criteria
Age Range18 Years — N/A
SexALL
Healthy VolunteersNo
Study Sites158

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 ...

Countries:United StatesArgentinaAustraliaAustriaBelgiumBrazilBulgariaCanadaCzechiaDenmarkFranceGermanyGreeceHong KongItalyNetherlandsPolandPortugalSingaporeSouth KoreaSpainTaiwan
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Recent Changes (Last 90 Days)
LOWMay 26, 2026NCT05216432primaryCompletionDate: changed
LOWMay 26, 2026NCT06982521primaryCompletionDate: changed
LOWMay 24, 2026NCT05216432studyFirstPostDate: changed
LOWMay 24, 2026NCT06982521studyFirstPostDate: changed