In short
RGT-419B is an investigational chemical substance being studied for locally advanced or metastatic estrogen receptor-positive, HER2-negative breast cancer that has progressed after a CDK4/6 inhibitor. One authorised trial in the EU registry is investigating it alone and in combination with giredestrant, compared against abemaciclib plus giredestrant. The trial is a Phase 1 study with a planned enrollment of 285 participants.
Key points
- RGT-419B is an investigational oral medicine with no marketing authorisation in the product records.
- It is being studied in estrogen receptor-positive, HER2-negative breast cancer that has progressed during or after a CDK4/6 inhibitor.
- The registered EU trial is a Phase 1 study with a planned enrollment of 285 participants.
- The trial compares RGT-419B alone and in combination with giredestrant against abemaciclib plus giredestrant.
- The primary measures include safety and side effects, dose-limiting toxicities, and progression-free survival.
- The trial is currently authorised in the EU Clinical Trials Information System.
What is RGT-419B?
RGT-419B is a chemically synthesised investigational substance. It is also known by the development code RO7840734. The product records in the EU Clinical Trials Information System (CTIS) show no marketing authorisation for RGT-419B, meaning it is not yet an approved medicine. The substance is supplied by Regor Pharmaceuticals, Inc. and appears as the test substance in two trial records.
How does RGT-419B work?
The registered trial does not describe the molecular mechanism of RGT-419B in detail. The trial is designed for breast cancer that has progressed during or after treatment with a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor, which suggests that RGT-419B is being studied in a setting where previous CDK4/6 inhibition has failed. The trial compares RGT-419B alone and in combination with giredestrant, an estrogen receptor–targeting medicine, against abemaciclib plus giredestrant. No further mechanistic detail is provided in the registry data.
Which conditions is RGT-419B studied for?
The registered trial studies RGT-419B in one condition:
- Locally advanced or metastatic estrogen receptor-positive, HER2-negative breast cancer — a type of breast cancer that has spread beyond the breast or nearby lymph nodes and has progressed during or after treatment with a CDK4/6 inhibitor.
How is RGT-419B given?
RGT-419B is given as a hard capsule taken by mouth (oral route). The trial also includes oral giredestrant and oral abemaciclib as comparison or combination treatments.
What do the clinical trials show?
One trial is registered in the EU CTIS for RGT-419B. It is a Phase 1 interventional study with a planned enrollment of 285 participants. The trial has two stages: a Phase Ib stage to evaluate the safety of RGT-419B alone and in combination with giredestrant, and a Phase II stage to compare the efficacy of two dose levels of RGT-419B in combination with giredestrant against abemaciclib in combination with giredestrant. The primary outcomes include the incidence and severity of adverse events, changes in vital signs and laboratory test results, dose-limiting toxicities, and progression-free survival. The trial is currently authorised.
What side effects are known?
The registry record does not list specific side effects for RGT-419B. The trial is designed to measure the incidence and severity of adverse events and dose-limiting toxicities, which means side effects are being actively collected as part of the study. No supplementary safety information is available in the provided data.