HER2-positive Breast CancerPhase 3A166NCT06968585
A Study of A166 Versus Trastuzumab Emtansine (T-DM1) in Patients With HER2-Positive Unresectable or Metastatic Breast Cancer Previously Treated With Trastuzumab and Taxane Therapy
A Phase 3 study testing A166 and T-DM1 in people with HER2-positive Breast Cancer, run by Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. at 1 site in China.
Trial summary
Evaluation of the efficacy of A166 versus trastuzumab emtansine (T-DM1) in Patients with HER2-Positive unresectable or metastatic breast cancer previously treated with trastuzumab and taxane therapy Read more about this study
- Who is it for?
- Ages 18 to 75 years
- Conditions the study is for
- HER2-positive Breast Cancer
- What is being tested?
- A166 and T-DM1
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 365 participants
- Where
- 1 siteChina
- Study dates
- 18 Jul 2023to 31 Mar 2028
- Phase
- Phase 3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 75 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Male or female patient ≥ 18 years and ≤ 75 years when signing the informed consent form.
- Breast cancer patients by histopathology and/or cytology documented.
- Disease progression after receiving a trastuzumab-based regimen (or a commercially available trastuzumab biosimilar or inetetamab) in the advanced or metastatic setting, or disease progression/recurrence within 12 months during or after (neo)adjuvant therapy (with a trastuzumab-based regimen or commercially available trastuzumab biosimilar).
- Have previously received taxanes.
- Patients must have experienced disease progression or intolerance during or after the most recent treatment prior to randomization.
- At least one measurable lesion according to RECIST 1.1 criteria
Who cannot join
- Previous treatment with A166 or any HER2-targeted antibody-drug conjugate (ADC) with a microtubule inhibitor payload.
- Known history of severe hypersensitivity to other monoclonal antibodies, or allergy to A166 , T-DM1 (trastuzumab emtansine) or their components.
- Permanent discontinuation of trastuzumab or its biosimilars due to any toxicity in prior treatments.
- Presence of severe corneal epithelial disease at baseline; or inability to perform daily activities without contact lenses.
- Presence of spinal cord compression or clinically active central nervous system (CNS) metastases.
- Other conditions considered by the investigator to make the patient unsuitable for participation in the study
Trial locations and contacts
1 site in 1 country.
China1 site
Fudan University Shanghai Cancer Center
Shanghai, Shanghai Municipality, 200032
About this study
Official title: A Phase III,Multicenter,Randomized,Open-Label,Active-Controlled Trial of A166 Versus Trastuzumab Emtansine (T-DM1) in Patients With HER2-Positive Unresectable or Metastatic Breast Cancer Previously Treated With Trastuzumab and Taxane Therapy
Evaluation of the efficacy of A166 versus trastuzumab emtansine (T-DM1) in Patients with HER2-Positive unresectable or metastatic breast cancer previously treated with trastuzumab and taxane therapy
Read the detailed description
This study will evaluate the efficacy of A166 versus trastuzumab emtansine (T-DM1) in patients with HER2-positive unresectable or metastatic breast cancer previously treated with trastuzumab and taxane therapy
To further evaluate the efficacy of A166 versus T-DM1 in patients with HER2-positive unresectable or metastatic breast cancer, based on effectiveness endpoints including:
Overall survival (OS)
Progression-free survival (PFS) as assessed by investigators
Objective response rate (ORR), disease control rate (DCR), duration of response (DOR), and clinical benefit rate (CBR) assessed by both blinded independent central review (BICR) and investigators.
To assess the safety profile of A166 for injection in patients with HER2-positive unresectable or metastatic breast cancer.
To evaluate the immunogenicity of A166 for injection in patients with HER2-positive unresectable or metastatic breast cancer.
To characterize the pharmacokinetic (PK) profile of A166 for injection in patients with HER2-positive unresectable or metastatic breast cancer.
- Conditions
- HER2-positive Breast Cancer
- Being tested
- A166, T-DM1
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
A166Drug
intravenous(IV) infusion (Q3W)
T-DM1Drug
intravenous(IV) infusion (Q3W)
| Study group | Role | What they receive |
|---|---|---|
| A166 | Experimental | A166 is administered intravenously at a dose of 4.8 mg/kg every 21 (±3) days (q3w). Receives: Drug: A166 |
| T-DM1 | Active comparator | T-DM1 is administered intravenously at a dose of 3.6 mg/kg every 21 (±3) days (q3w). Receives: Drug: T-DM1 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Progression-free survival (PFS)
PFS as assessed by BICR according to RECIST v 1.1
Measured: Randomization up to approximately 39 months
Secondary outcomes (4)
Overall survival (OS)
OS, 1-year survival rate, 2-year survival rate, and 3-year survival rate.
Measured: Randomization up to approximately 48 months
Objective response rate(ORR)
ORR is defined as the percentage of patients who achieve complete response(CR) or partial response (PR), as assessed by BICR/investigator per RECIST 1.1
Measured: Randomization up to approximately 39 months
Disease control rate(DCR)
DCR is defined as the percentage of patients who achieve CR, PR or stable disease (SD), as assessed by BICR/investigator per RECIST 1.1
Measured: Randomization up to approximately 39 months
Duration of response(DOR)
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 BICR/investigator or death due to any cause, whichever occurs first.
Measured: Randomization up to approximately 39 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted13 May 2025
- Study start18 Jul 2023
- Primary completion30 Nov 2026 (estimated)
- Study completion31 Mar 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for HER2-positive Breast CancerStudies of the same condition, open and under way.
- More trials run by Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd.The sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 365 participants (actual)
Sponsor and investigators
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06968585
- Sponsor's protocol ID
- KL166-III-06
- Acronym
- A166
- Status last verified
- May 2026
- First submitted
- 26 Apr 2025
- Last updated
- 8 May 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Zhang J, Ouyang Q, Zhang Q, Li H, Wang X, Wang Y, Yin Y, Wang S, Gu Y, Sun T, Wang J, Wu X, Li F, Chen X, Li M, Yang J, Yang H, Sun Z, Nie J, Wang X, Liu J, Tang X, Wang H, Huang Z, Xie W, Chen W, Li F, Teng Y, Zhang S, Zeng R, Wang W, Ma L, Gao Y, Yu H, Cao X, Qing Y, Jin X, Ge J, Wang H, Hu X. Trastuzumab Botidotin Versus Trastuzumab Emtansine in Human Epidermal Growth Factor Receptor 2-Positive Advanced Breast Cancer: A Phase III, Open-Label, Randomized Controlled Trial. J Clin Oncol. 2026 Sep 11:JCO2600602. doi: 10.1200/JCO-26-00602. Online ahead of print.
PubMed 42727044
Study at a glance
From the registry record, last updated by the sponsor on 8 May 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase III,Multicenter,Randomized,Open-Label,Active-Controlled Trial of A166 Versus Trastuzumab Emtansine (T-DM1) in Patients With HER2-Positive Unresectable or Metastatic Breast Cancer Previously Treated With Trastuzumab and Taxane Therapy
- ClinicalTrials.gov ID
- NCT06968585
- Acronym / sponsor ID
- A166 / KL166-III-06
- Conditions
- HER2-positive Breast Cancer
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 365 participants (actual)
- Lead sponsor
- Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd.Industry (pharma, biotech, devices)
- Study start
- 18 Jul 2023 (actual)
- Primary completion
- 30 Nov 2026 (estimated)
- Study completion
- 31 Mar 2028 (estimated)
- First posted
- 13 May 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Evaluation of the efficacy of A166 versus trastuzumab emtansine (T-DM1) in Patients with HER2-Positive unresectable or metastatic breast cancer previously treated with trastuzumab and taxane therapy
Detailed description
This study will evaluate the efficacy of A166 versus trastuzumab emtansine (T-DM1) in patients with HER2-positive unresectable or metastatic breast cancer previously treated with trastuzumab and taxane therapy
To further evaluate the efficacy of A166 versus T-DM1 in patients with HER2-positive unresectable or metastatic breast cancer, based on effectiveness endpoints including:
Overall survival (OS)
Progression-free survival (PFS) as assessed by investigators
Objective response rate (ORR), disease control rate (DCR), duration of response (DOR), and clinical benefit rate (CBR) assessed by both blinded independent central review (BICR) and investigators.
To assess the safety profile of A166 for injection in patients with HER2-positive unresectable or metastatic breast cancer.
To evaluate the immunogenicity of A166 for injection in patients with HER2-positive unresectable or metastatic breast cancer.
To characterize the pharmacokinetic (PK) profile of A166 for injection in patients with HER2-positive unresectable or metastatic breast cancer.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| A166 | Experimental | Drug: A166A166 is administered intravenously at a dose of 4.8 mg/kg every 21 (±3) days (q3w). |
| T-DM1 | Active comparator | Drug: T-DM1T-DM1 is administered intravenously at a dose of 3.6 mg/kg every 21 (±3) days (q3w). |
Who may qualify
- Ages
- 18 to 75 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- Male or female patient ≥ 18 years and ≤ 75 years when signing the informed consent form.
- Breast cancer patients by histopathology and/or cytology documented.
- Disease progression after receiving a trastuzumab-based regimen (or a commercially available trastuzumab biosimilar or inetetamab) in the advanced or metastatic setting, or disease progression/recurrence within 12 months during or after (neo)adjuvant therapy (with a trastuzumab-based regimen or commercially available trastuzumab biosimilar).
- Have previously received taxanes.
- Patients must have experienced disease progression or intolerance during or after the most recent treatment prior to randomization.
Key exclusion criteria (6 listed)
- Previous treatment with A166 or any HER2-targeted antibody-drug conjugate (ADC) with a microtubule inhibitor payload.
- Known history of severe hypersensitivity to other monoclonal antibodies, or allergy to A166 , T-DM1 (trastuzumab emtansine) or their components.
- Permanent discontinuation of trastuzumab or its biosimilars due to any toxicity in prior treatments.
- Presence of severe corneal epithelial disease at baseline; or inability to perform daily activities without contact lenses.
- Presence of spinal cord compression or clinically active central nervous system (CNS) metastases.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| A166intravenous(IV) infusion (Q3W) | Drug | A166 |
| T-DM1intravenous(IV) infusion (Q3W) | Drug | T-DM1 |
Primary outcome
Progression-free survival (PFS)
Time frame: Randomization up to approximately 39 months
PFS as assessed by BICR according to RECIST v 1.1
4 secondary outcomes
Overall survival (OS)
Time frame: Randomization up to approximately 48 months
Objective response rate(ORR)
Time frame: Randomization up to approximately 39 months
Disease control rate(DCR)
Time frame: Randomization up to approximately 39 months
Duration of response(DOR)
Time frame: Randomization up to approximately 39 months
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 8 May 2026.
- Derived from this study: PubMed 42727044Zhang J, Ouyang Q, Zhang Q, Li H, Wang X, Wang Y, Yin Y, Wang S, Gu Y, Sun T, Wang J, Wu X, Li F, Chen X, Li M, Yang J, Yang H, Sun Z, Nie J, Wang X, Liu J, Tang X, Wang H, Huang Z, Xie W, Chen W, Li F, Teng Y, Zhang S, Zeng R, Wang W, Ma L, Gao Y, Yu H, Cao X, Qing Y, Jin X, Ge J, Wang H, Hu X. Trastuzumab Botidotin Versus Trastuzumab Emtansine in Human Epidermal Growth Factor Receptor 2-Positive Advanced Breast Cancer: A Phase III, Open-Label, Randomized Controlled Trial. J Clin Oncol. 2026 Sep 11:JCO2600602. doi: 10.1200/JCO-26-00602. Online ahead of print.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing A166 and T-DM1 in people with HER2-positive Breast Cancer, run by Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. at 1 site in China.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 6 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 8 May 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in China. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Progression-free survival (PFS) (time frame: Randomization up to approximately 39 months). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT06968585, which also lists 1 linked publication.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 8 May 2026.