Ph 3 Study: RLY-2608 + Fulvestrant vs. Capivasertib + Fulvestrant in PIK3CA-mutant HR+/HER2- ABC

• Research type

  Research Study

• Full title

  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

• IRAS ID

  1004610

• Contact name

  Sabrina Khalil

• Contact email

  Study-RLY-2608-102@relaytx.com

• Sponsor organisation

  Relay Therapeutics, Inc.

• Clinicaltrials.gov Identifier

  NCT06982521

• Research summary

  The study is designed to learn about the effectiveness and safety of the experimental (investigational) drug called RLY2608 in combination with fulvestrant compared to capivasertib in combination with fulvestrant when given to individuals who have been diagnosed with locally advanced or metastatic hormone receptor-positive, human epidermal growth factor 2-negative (HR+/HER2-) breast cancer and have at least one mutation in a gene called PIK3CA.

  RLY-2608 in combination with fulvestrant was tested in a previous study (ReDiscover) with a group of patients and has shown encouraging results. This new study aims to confirm the evidence of benefit seen in the ReDiscover study in a larger group of participants compared to standard therapy with capivasertib in combination with fulvestrant to find out which is better for treating this type of breast cancer.

  The study is being done to find answers to the following questions:
  • Can RLY-2608 combined with fulvestrant help patients with this type of cancer more than capivasertib combined with fulvestrant?
  • What are the side effects of RLY-2608 combined with fulvestrant compared to capivasertib combined with fulvestrant?

  This is a randomised, open-label study. Participants will be randomly assigned (like a coin toss) to receive either:
  • Group A: RLY-2608 in combination with fulvestrant
  • Group B: capivasertib in combination with fulvestrant
  Participants will have a 50% (1 in 2) chance of being assigned to Group A or Group B

• REC name

  London - Westminster Research Ethics Committee

• REC reference

  25/LO/0738

• Date of REC Opinion

  29 Oct 2025

• REC opinion

  Further Information Favourable Opinion