Regor Therapeutics Announces Promising Phase 1A Results for RGT-419B, a Next-Generation CDK4 Inhibitor, in Heavily Pretreated HR+/HER2- Advanced Breast Cancer Patients

Regor Therapeutics Announces Positive Safety and Monotherapy Efficacy Data for RGT-419B in HR+/HER2- Advanced Breast Cancer (ABC) Patients Previously Treated with CDK4/6 Inhibitors and Endocrine Therapy (ET).

● RGT-419B is a new generation of CDK4 inhibitors, demonstrating good safety and tolerability in the first-in-human Phase I single-agent dose escalation study.

● Preliminary efficacy of monotherapy was observed in HR+/HER2- ABC that had previously received CDK4/6 inhibitors and ET.

● Current data support the continued development of RGT-419B as a monotherapy or in combination with ET for the treatment of HR+/HER2- ABC.

Regor Therapeutics (hereinafter referred to as "Regor"), a global innovative company with top-tier drug discovery engines and a differentiated clinical development pipeline, announced preliminary results from the Phase I dose-escalation study of its next-generation CDK4 inhibitor RGT-419B in HR+/HER2-ABC patients previously treated with CDK4/6 inhibitors and ET (data cut-off date: September 26, 2023). The findings were selected for a poster (PO3-18-06) at the 2023 San Antonio Breast Cancer Symposium (SABCS). The title is "First-in-Human Phase 1A Study of the Next-Generation CDK4 Inhibitor RGT-419B in HR+/HER2-ABC Patients Previously Treated with CDK4/6 Inhibitors," with results as follows:

● The study enrolled a total of 12 HR+/HER2- ABC patients who had previously received CDK4/6 inhibitors and ET treatment. RGT-419B was administered orally on a continuous basis in 28-day cycles. RGT-419B demonstrated good safety and tolerability, with no dose-limiting toxicity (DLT) events observed, and no patients discontinued treatment due to adverse reactions.

● The exposure of RGT-419B increases proportionally with the dose, and it has a long half-life and a small peak-to-trough ratio at steady state.

● RGT-419B demonstrated preliminary efficacy in heavily pretreated HR+/HER2- ABC patients. Three patients achieved partial response (PR) and remain on treatment. Six patients have been on RGT-419B therapy for over 24 weeks.

● RGT-419B has demonstrated promising efficacy as a single agent, consistent with the preclinical data observed in CDK4/6 inhibitor-resistant breast cancer models.

"RGT-419B has demonstrated its potential to become the best-in-class next-generation CDK4 inhibitor for the treatment of HR+/HER2- ABC," said Dr. Xiayang Qiu, CEO of Regor Therapeutics. "The results published by Regor are encouraging, showing that RGT-419B is not only safe and well-tolerated but also exhibits monotherapy efficacy in HR+/HER2- ABC patients previously treated with CDK4/6 inhibitors and ET." These data suggest that RGT-419B has the potential to be used as a monotherapy for the treatment of HR+/HER2- ABC resistant to CDK4/6 inhibitors and ET. Based on its favorable safety profile and positive monotherapy efficacy, RGT-419B has best-in-class potential as either a monotherapy or combination therapy for HR+/HER2- breast cancer patients resistant to CDK4/6 inhibitors, as well as for earlier lines of treatment. Clinical studies of RGT-419B as a monotherapy expansion cohort and in combination with ET are currently ongoing.

This Phase I trial (NCT05304962) is a multicenter, open-label study designed to evaluate the safety, tolerability, pharmacokinetics, and preliminary antitumor activity of RGT-419B as a monotherapy or in combination with ET in HR+/HER2- ABC patients previously treated with CDK4/6 inhibitors and ET.

The poster can be viewed under the "Science" category on Regor Therapeutics' English website.

SABCS is the largest, highest-level, and most influential international academic conference in the field of breast cancer worldwide. Since 1977, it has developed into a symposium attended by researchers and physician representatives from over 90 countries and regions, aiming to provide the international academic community, physicians, and researchers with cutting-edge information on the experimental biology, etiology, prevention, diagnosis, and treatment of breast cancer and precancerous breast diseases.

Regor Therapeutics is a biopharmaceutical company founded in 2018, composed of a highly reputed team of scientists in the field of drug discovery and a senior management team covering the entire lifecycle of drug development. Leveraging its industry-leading rCARD™ (Computing Accelerated Rapid Drug Discovery) core advantage, Regor has successfully advanced 8 candidate drugs and submitted 5 clinical trial applications, demonstrating that its efficient R&D ecosystem can accelerate the discovery of innovative therapeutic drugs.

Regor's self-developed pipeline focuses on three major therapeutic areas: metabolism, oncology, and autoimmune diseases, including two industry-leading clinical assets: 1) RGT-075, an oral small molecule GLP1R receptor agonist with best-in-class drug potential for treating obesity and other diseases; 2) RGT-419B, a unique CDK4+ inhibitor demonstrating excellent monotherapy efficacy in refractory ER+/Her2- breast cancer patients.

Regor Therapeutics is focused on expanding its exceptional drug R&D capabilities and global competitiveness, committed to building a world-class innovative drug R&D engine that promotes a strong team culture of advanced science leadership, result-driven delivery, shared responsibility, and mutual success.