RGT-419B

Table of contents

• What is RGT-419B?
• How does RGT-419B work?
• Which conditions is RGT-419B studied for?
• How is RGT-419B given?
• What do the clinical trials show?
• What side effects are known?

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.^[1] The substance is supplied by Regor Pharmaceuticals, Inc. and appears as the test substance in two trial records.^[1]

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.^[1] The trial compares RGT-419B alone and in combination with giredestrant, an estrogen receptor–targeting medicine, against abemaciclib plus giredestrant.^[1] 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.^[1]

How is RGT-419B given?

RGT-419B is given as a hard capsule taken by mouth (oral route).^[1] The trial also includes oral giredestrant and oral abemaciclib as comparison or combination treatments.^[1]

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.^[1] 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.^[1] 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.^[1] The trial is currently authorised.^[1]

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.^[1] No supplementary safety information is available in the provided data.