A Study of A166 in Patients With HER2-Positive Unresectable or Metastatic Breast Cancer

May 5, 2026 updated by: Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd.

Phase 2 Study of A166 in HER2-positive Metastatic Breast Cancer Patients Who Were Previously Treated With TOP1-ADCs

Evaluation of the efficacy of A166 in Patients with HER2-Positive unresectable or metastatic breast cancer previously treated with TOP1 inhibitor Antibody-Drug Conjugates

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

This study will evaluate the efficacy of A166 in patients with HER2-positive unresectable or metastatic breast cancer previously treated with TOP1 inhibitor Antibody-Drug Conjugates.

A166 will be administered every 3 weeks (Q3W) intravenous (IV) infusion.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
40

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • China
    • Henan
      • Zhenzhou, Henan, China, 450000
        • Recruiting
        • Henan Provincial Cancer Hospital
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. Male or female patient ≥ 18 years and ≤ 75 years when signing the informed consent form.
  2. Breast cancer patients by histopathology and/or cytology documented.
  3. In the advanced or metastatic stage, having received no more than 5 lines of systemic therapy, one of which must include a HER2 ADC with a topoisomerase inhibitor payload.
  4. Patients must have experienced disease progression or intolerance during or after the most recent treatment prior to randomization.
  5. At least one measurable lesion according to RECIST 1.1 criteria.

Exclusion Criteria:

  1. Previous treatment with A166 or any HER2-targeted antibody-drug conjugate (ADC) with a microtubule inhibitor payload.
  2. Known history of severe hypersensitivity to other monoclonal antibodies, or allergy to A166 or their components.
  3. Permanent discontinuation of trastuzumab or its biosimilars due to any toxicity in prior treatments.
  4. Presence of severe corneal epithelial disease at baseline; or inability to perform daily activities without contact lenses.
  5. Presence of spinal cord compression or clinically active central nervous system (CNS) metastases.
  6. Other conditions considered by the investigator to make the patient unsuitable for participation in the study.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: A166
A166 is administered intravenously at a dose of 4.8 mg/kg every 21 (±3) days (q3w).
Drug: A166
intravenous(IV) infusion (Q3W)

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Objective response rate(ORR)
Time Frame: Within 24 months of last patient enrolled
ORR is defined as the percentage of patients who achieve complete response(CR) or partial response (PR), as assessed by investigator per RECIST 1.1
Within 24 months of last patient enrolled

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Progression-free survival (PFS)
Time Frame: Within 24 months of last patient enrolled
PFS, 6-month PFS, 12-month PFS.PFS as assessed by investigator according to RECIST v 1.1
Within 24 months of last patient enrolled
Overall survival (OS)
Time Frame: Within 48 months of last patient enrolled
OS, 1-year survival rate, 1.5-year survival rate, and 2-year survival rate.OS defined as time from inclusion until death
Within 48 months of last patient enrolled
Disease control rate(DCR)
Time Frame: Within 24 months of last patient enrolled
DCR is defined as the percentage of patients who achieve CR, PR or stable disease (SD), as assessed by investigator per RECIST 1.1
Within 24 months of last patient enrolled
Duration of response(DOR)
Time Frame: Within 24 months of last patient enrolled
DoR is defined as the time from the date of first documented CR or PR until date of documented disease progression per RECIST 1.1, as assessed by investigator or death due to any cause, whichever occurs first.
Within 24 months of last patient enrolled
Clinical Benefit Rate (CBR)
Time Frame: Within 24 months of last patient enrolled
CBR is defined as a patient having a best overall response of a complete response (CR), partial response (PR), or stable disease for at least 6 months.
Within 24 months of last patient enrolled

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
September 20, 2024

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
September 20, 2027

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 31, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
December 3, 2025

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
December 17, 2025

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
December 23, 2025

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
May 8, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 5, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
May 1, 2026

More Information

Terms related to this study

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • KL166-II-08

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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