To Evaluate the Safety, Tolerability, Pharmacokinetics and Efficacy of HRS-6209 in Subjects With HR-Positive/HER2-Negative Solid Tumor

An Open-Label, Multi-Center Phase II Clinical Study Evaluating the Safety, Tolerability, Pharmacokinetics, and Preliminary Efficacy of HRS-6209 in Combination With Fulvestrant or Letrozole in Patients With Solid Tumor

To evaluate the Safety, Tolerability, Pharmacokinetics and Efficacy of HRS-6209 in Subjects with HR-Positive/HER2-Negative solid tumor.

Study Overview

• Status: Not yet recruiting
• Conditions: Breast Cancer
• Intervention / Treatment: Drug: HRS-6209 Capsules and fulvestrant injection

• Study Type: Interventional
• Enrollment (Estimated): 15
• Phase: Phase 1

Contacts and Locations

• Study Contact: Name: Kathy You; Phone Number: +61 02 9299 0433; Email: kathyyou@atridia.com
• Study Contact Backup: Name: Ravi Patel; Phone Number: +61 452 363 506; Email: ravi.patel@atridia.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria

1. Ability to understand the trial procedures and possible adverse events, voluntarily participate in the trial.
2. Adequate bone marrow and other vital organ functions
3. Adequate liver function tests
4. HR-positive or HER2-negative solid tumor patients

Exclusion Criteria

1. Plan to receive any other anti-tumor therapy during the study.
2. Active brain metastases .
3. Have poorly controlled or severe cardiovascular disease, including (1) congestive heart failure.
4. Previous use of fulvestrant
5. clinically significant endometrial abnormalities, including but not limited to endometrial hyperplasia and dysfunctional uterine bleeding.
6. With uncontrollable chronic systemic complications (such as severe chronic lung, liver, kidney, or heart disease).
7. With acute or active tuberculosis infection requiring medication.
8. Pregnant or lactating women, or females planning to become pregnant During the study.
9. Known history of clinically significant liver disease, untreated active hepatitis (hepatitis B, defined as hepatitis B virus surface antigen [HBsAg] or hepatitis B core antibody [HBcAb] positive

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: HRS-6209 Capsules and fulvestrant injection	Drug: HRS-6209 Capsules and fulvestrant injection; HRS-6209, 100mg BID for 4 weeks, and single dose of fulvestrant injection

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Safety by reporting incidence and severity of Adverse events (graded as per CTCAE V5.0) of adverse events (AEs) and serious adverse events (SAEs),	To safety and tolerability of HRS-6209 in combination with fulvestrant in patients with advanced unresectable or metastatic breast cancer	Screening up to study completion,, an average of 1 year.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Objective Response Rate (ORR)	ORR refers to the proportion of subjects with a complete response (CR) or partial response (PR) based on all soft tissue assessments recorded from the date of first drug administration to either the date of radiographic disease progression (including bone progression and soft tissue progression), death from any cause, or the initiation of a new antitumor therapy, whichever occurs first. For subjects with CR or PR at the first evaluation, the efficacy should be confirmed 4 weeks later or at the next tumor imaging evaluation. The numerator includes subjects with a confirmed CR/PR at least 4 weeks after the initial assessment. The denominator consists of subjects with measurable target lesions at baseline.	Screening up to study completion, an average of 2 years.
Concentration	Plasma concentrations of HRS-6209 during multiple dosing, directly observed from data.	From administration to C2, up to 4 months.
Cmax,ss	Css, max are steady-state maximum concentrations of HRS-6209 during multiple dosing, and are directly observed from data.	From administration to C2, up to 4 months.
Cmin,ss	Css, min are the steady-state trough concentrations of HRS-6209 during multiple dosing, and are directly observed from data.	From administration to C2, up to 4 months.
Best of Response (DoR)	BOR refers to the best response of tumor evaluation, including CR, PR, stable disease (SD), progressive disease (PD), and not evaluable for response (NE).	Screening up to study completion, an average of 2 years.
Disease Control Rate (DCR)	DCR refers to the time from the first occurrence of CR or PR to PD or death from any cause, whichever occurs first, in subjects with objective response. DCR will be recorded from baseline visit until the end of the study.	Screening up to study completion, an average of 2 years.
rPFS (radiographic progression-free survival	rPFS refers to the time from the first dose of investigational drug to the first radiographic PD or death from any cause (whichever occurs first) as assessed by the investigator. rPFS will be recorded from baseline visit until the end of the study.	Screening up to study completion, an average of 2 years.

Collaborators and Investigators

• Sponsor: Atridia Pty Ltd.

Study record dates

Study Major Dates

• Study Start (Estimated): March 15, 2026
• Primary Completion (Estimated): April 10, 2027
• Study Completion (Estimated): November 10, 2027

Study Registration Dates

• First Submitted: December 28, 2025
• First Submitted That Met QC Criteria: January 13, 2026
• First Posted (Actual): January 22, 2026

Study Record Updates

• Last Update Posted (Actual): January 22, 2026
• Last Update Submitted That Met QC Criteria: January 13, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Skin Diseases; Breast Diseases; Skin and Connective Tissue Diseases; Breast Neoplasms
• Other Study ID Numbers: HRS-6209-205

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No