FDA Clears IND of BTX-9341 in HR+/HER2- Breast Cancer


With the clearance of an investigational new drug application for BTX-9341 from the FDA, a phase 1 trial will evaluate the agent in HR-positive/HER2-negative breast cancer.

  • The FDA has granted clearance to the investigational new drug (IND) application for BTX-9341.
  • BTX-9341 is a novel cyclin-dependent kinase 4/6 (CDK4/6) bifunctional degrader being developed for the treatment of hormone receptor (HR)-positive/HER2-negative breast cancer.
  • A phase 1 trial will evaluate the agent for this indication and currently has plans to start the study in the second half of 2024.
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The FDA has cleared the IND application for BTX-9341, a novel CDK4/6 bifunctional degrader for the potential treatment of patients with HR-positive/HER2-negative breast cancer.1

"Securing FDA clearance for our BTX-9341 IND application marks a significant milestone for Biotheryx, affirming our commitment to advancing innovative, orally bioavailable targeted protein degraders. As we transition from promising preclinical data to clinical trials, we are poised to explore the potential of BTX-9341 in offering tangible clinical benefits to patients battling breast cancer," said Leah Fung, PhD, chief executive officer of Biotheryx, in a press release.

Plans are in place for a phase 1 clinical trial of BTX-9341 to begin in the second half of 2024. The study will evaluate the agent in patients with HR-positive/HER2-negative breast cancer that is resistant to CDK4/6 inhibitor therapies.

In the phase 1 trial, experts will utilize a dose-escalation portion to evaluate the initial monotherapy administration of BTX-9341 and a dose-expansion portion evaluating the combination of BTX-9341 with fulvestrant.

Breast Cancer: © SciePro - stock.adobe.com

Breast Cancer: © SciePro - stock.adobe.com

Initially, experts will assess the safety, biological activity, and preliminary efficacy of BTX-9341.

About BTX-9341’s Mechanism of Action

BTX-9341 represents a pioneering oral compound designed to degrade CDK4 and CDK6, crucial targets implicated in various cancer types. Its efficacy has been clinically affirmed, particularly in specified breast cancer scenarios.

The first-in-class, oral degrader of CDK4 and CDK6, BTX-9341, has previously shown superiority to CDK4/6 inhibitors in preclinical breast cancer models. Here, BTX-9341 demonstrated increased efficacy potential with potent and highly selective degradation of CDK4/6, as well as robust inhibition of cyclin E and CDK2 transcription and cell cycle arrest. Moreover, BTX-9341 had superior in vivo efficacy in breast cancer xenografts, superior blood-brain barrier penetration, and overall, was effective in models resistant to existing CDK4/6 inhibitors.2

Previously in April 2023, Biotheryx, Inc. nominated BTX-9341 as a development candidate for the CDK4/6 degrader program. With this, IND-enabling studies began.

1. Biotheryx announces U.S. FDA clearance of investigational new drug application for BTX-9341, a first-in-class, dual bifunctional degrader of CDK4/6. News release. Biotheryx, Inc. May 7, 2024. Accessed May 7, 2024. https://tinyurl.com/2t87wbh6
2. Biotheryx presents preclinical CDK4/6 and SOS1 protein degrader data at AACR 2023 annual meeting. News release. Biotheryx, Inc. April 17, 2023. Accessed May 7, 2024. https://tinyurl.com/37fha7ue

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