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Hormone Receptor PositivePhase 1/2NCT07701941

A Study of Patritumab Deruxtecan (HER3-DXd) in Combination With Trastuzumab Deruxtecan (T-DXd) in Participants With HR-Positive, HER2-Low or HER2-Ultralow Unresectable or Metastatic Breast Cancer

A Phase 1/2 study testing Patritumab deruxtecan and Trastuzumab deruxtecan in people with Hormone Receptor Positive and HER2-low or HER2-ultralow, run by Daiichi Sankyo at 72 sites in 8 countries.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
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Trial summary

The primary purpose of the study is to assess the safety, tolerability, and anti-tumor activity of HER3-DXd and T-DXd in the combination dosing regimens in participants with hormone receptor positive, HER2-low or HER2-ultralow, unresectable, or metastatic breast cancer. Read more about this study

Who is it for?
Ages 18 years and older
What is being tested?
Patritumab deruxtecan and Trastuzumab deruxtecan
Type of treatment
Injection or infusion
Could I receive a placebo?
No, everyone receives an active treatment
How many people
220 participants
Where
72 sitesin 8 countries
Study dates
17 Sep 2026to 1 May 2032
Phase
Phase 1/2
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 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Pathologically documented breast cancer that meets the following:
  • Unresectable or metastatic.
  • HR+ based on testing performed locally. HR+ (estrogen receptor [ER] and/or progesterone receptor [PgR] positive [ER or PgR greater than equal to (≥)1 percent (%)] per American Society of Clinical Oncology [ASCO]/College of American Pathologists [CAP] 2020 guidelines) in the unresectable or metastatic setting.
  • Assessed as HER2-low (defined as Immunohistochemistry (IHC)2+/In-situ hybridization (ISH)- or IHC1+) or HER2-ultralow (defined as IHC 0 with any membrane staining in greater than (>) 0 and lesser than equal to (≤)10% of the cancer cells) locally for Part 1 and centrally for Part 2. The HER2 result must be from a tumor sample obtained in the unresectable or metastatic setting.
  • For Dose Regimen Determination (Part 1), HER2 status used for eligibility assessment must be determined locally (according to applicable regulations) using the PATHWAY anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody (Ventana Medical Systems, Inc.). Additional HER2 testing will be performed locally and according to applicable regulations using the prescribed test during Screening only if prior results obtained with this test are not available for eligibility assessment.
  • For Dose Expansion (Part 2), HER2 testing will be performed prospectively at a central laboratory using the pretreatment tumor tissue sample.
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  • Provides a pretreatment tumor tissue sample that meets one of the following collection requirements:
  • Tissue biopsy collected from ≥1 lesion not previously irradiated and performed since progression with the most recent systemic cancer therapy regimen and prior to signature of the Tissue Screening informed consent form (ICF) (ARCHIVAL PRETREATMENT sample).
  • OR
  • Newly obtained pretreatment tumor biopsy from ≥1 lesion not previously irradiated and amenable to sampling, after signature of the Tissue Screening ICF (FRESH PRETREATMENT sample).
  • Documented radiologic disease progression as per investigator assessment per RECIST v1.1 criteria (during or after most recent treatment).
  • Documented refractoriness to endocrine therapy, defined as disease progression on one or more line of endocrine therapy in the unresectable or metastatic setting and determined by the investigator that participant would no longer benefit from further treatment with endocrine therapy.
  • Prior treatment with a Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor in any setting. Subsequent endocrine therapies administered after progression on CDK4/6 inhibitor are allowed.
  • Participants with genomic alterations/mutations (Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Alpha (PIK3CA), phosphatase and tensin homolog (PTEN), AKT, or Breast Cancer gene (BRCA)1/2) who are eligible for approved targeted therapies in combination with endocrine therapy or as monotherapy (according to local label and availability) must have received the corresponding therapy prior to enrollment, unless contraindicated or not accessible in their country/region.
  • No prior chemotherapy for unresectable or metastatic breast cancer. Participants who have received chemotherapy in the neoadjuvant or adjuvant setting are eligible.
  • ECOG performance status 0 or 1 at the time of Screening.
  • Has ≥1 measurable lesion on CT or MRI per RECIST v1.1 by investigator assessment.
  • Has adequate bone marrow reserve and organ function based on local laboratory data within 7 days prior to the first dose as specified in the protocol.

Who cannot join

  • Prior treatment with an anti-HER3 antibody and/or antibody-drug conjugate (ADC) that consists of a topoisomerase I inhibitor (e.g., T-DXd) or any other topoisomerase I inhibitor therapy.
  • Has any history of interstitial lung disease (ILD)/pneumonitis irrespective of steroid use, or current ILD, or suspected ILD, or ILD that cannot be ruled out by imaging at Screening. Examples of suspected ILD/pneumonitis by imaging include the presence of lung parenchymal fibrosis, such as CPFE, and any radiographic features consistent with ILA, including but not limited to, extensive ground glass opacities, reticular opacities, traction bronchiectasis, and honeycombing. Participants may be eligible if they had history of radiation pneumonitis that did not require steroids.
  • Is receiving chronic systemic corticosteroids dosed at >10 mg prednisone daily or equivalent anti-inflammatory activity or any form of immunosuppressive therapy prior to randomization. Participants who require use of bronchodilators, inhaled or topical steroids, or local steroid injections may be included in the trial.
  • Evidence of spinal cord compression or brain metastases, defined as being clinically active and symptomatic, or requiring therapy with corticosteroids or anticonvulsants to control associated symptoms. Participants with clinically inactive or treated brain metastases who are asymptomatic (i.e., without neurologic signs or symptoms and do not require treatment with corticosteroids or anticonvulsants) may be included in the trial but must have a stable neurologic status for ≥4 weeks prior to Cycle 1 Day 1. Participants with asymptomatic brain metastases and treated with anticonvulsants as prophylaxis can enroll.
  • Inadequate washout period of prior treatment before randomization:
  • Whole brain radiation therapy less than (<)28 days.
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  • Monoclonal antibodies other than immune checkpoint inhibitors, such as anti-vascular endothelial growth factor (VEGF) (e.g., bevacizumab) and anti-epidermal growth factor receptor (EGFR) (e.g., cetuximab) < 28 days.
  • Immune checkpoint inhibitor therapy <21 days.
  • Major surgery (excluding placement of vascular access) <28 days.
  • Radiotherapy treatment to more than 30% of the bone marrow or wide field radiation or palliative stereotactic radiation to chest <28 days or palliative stereotactic radiation therapy to other anatomic areas <14 days.
  • Chloroquine or hydroxychloroquine ≤14 days.
  • Hormonal therapy <21 days prior to first dose of HER3-DXd.
  • Live or live attenuated virus vaccination <30 days.
  • Uncontrolled or significant cardiovascular disease, including any of the following:
  • QTcF prolongation interval >450 milliseconds (ms) (average of triplicate determinations at screening).
  • Left ventricular ejection fraction (LVEF) ≤50%.
  • Resting systolic blood pressure >160 millimeters of mercury (mmHg) or diastolic blood pressure >100 mmHg.
  • Myocardial infarction within 6 months.
  • New York Heart Association (NYHA) Classes 3 or 4 congestive heart failure.
  • Uncontrolled angina pectoris within 6 months.
  • Cardiac arrhythmia requiring ongoing antiarrhythmic treatment.
  • Diagnosed or suspected long QT syndrome or known family history of long QT syndrome.
  • History of clinically relevant ventricular arrhythmias, such as ventricular tachycardia, ventricular fibrillation, or Torsade de Pointes.
  • Bradycardia of <50 beats per minute (bpm) unless the participant has a pacemaker.
  • History of second- or third-degree heart block. Participants with a history of heart block may be eligible if they currently have pacemakers and have no history of fainting or clinically relevant arrhythmia with pacemakers.
  • Coronary/peripheral artery bypass graft within 6 months.
  • Complete left bundle branch block.
  • Has history of other active malignancy within 3 years prior to randomization, except the following:
  • Adequately resected nonmelanoma skin cancer.
  • Adequately treated intraepithelial carcinoma of the cervix.
  • Any other curatively treated in situ disease.
  • Prostate carcinoma with a prostate-specific antigen value <0.2 nanograms per milliliter (ng/mL).
  • Has unresolved toxicities from previous anticancer therapy, defined as toxicities (other than alopecia) not yet resolved to National Cancer Institute-Common Terminology Criteria for Adverse Events version 5.0 (NCI-CTCAE v5.0) Grade ≤1 or baseline.
  • Any known contraindication to treatment, including hypersensitivity to either the drug substances or inactive ingredients in the drug products.
  • Note: Other protocol specified inclusion/exclusion criteria may apply.

Trial locations and contacts

72 sites in 8 countries. Contact the study team or a site near you to ask about taking part.

Daiichi Sankyo Contact for Clinical Trial Information contact

9089926400

CTRinfo_us@daiichisankyo.com

72 sites in 8 countries

Spain17 sites, 17 recruiting

  • Institut Catala d'Oncologia - Badalona

    Badalona, 08916

    Not yet recruiting

  • NEXT Oncology Barcelona

    Barcelona, 08023

    Not yet recruiting

  • Hospital Universitari Quiron Dexeus Barcelona

    Barcelona, 08028

    Not yet recruiting

  • Hospital Universitario Vall d'Hebron

    Barcelona, 08035

    Not yet recruiting

  • Hospital Clinic Barcelona

    Barcelona, 08036

    Not yet recruiting

  • Hospital Universitario San Cecilio

    Granada, 18016

    Not yet recruiting

  • Hospital Beata Maria Ana

    Madrid, 28007

    Not yet recruiting

  • Clinica Universidad de Navarra - Madrid

    Madrid, 28017

    Not yet recruiting

  • Hospital Universitario Ramon y Cajal

    Madrid, 28034

    Not yet recruiting

  • South Texas Accelerated Research Therapeutics (START) Madrid - CIOCC

    Madrid, 28050

    Not yet recruiting

  • Hospital Regional Universitario de Malaga

    Málaga, 29010

    Not yet recruiting

  • Hospital Universitario Virgen de la Victoria

    Málaga, 29010

    Not yet recruiting

  • Clinica Universidad de Navarra - Pamplona

    Pamplona, 31008

    Not yet recruiting

  • NEXT Oncology Madrid

    Pozuelo de Alarcón, 28223

    Not yet recruiting

  • Hospital Universitario de Canarias

    Santa Cruz de Tenerife, 38320

    Not yet recruiting

  • Hospital Clinico Universitario de Santiago

    Santiago de Compostela, 15706

    Not yet recruiting

  • Hospital Universitario Virgen del Rocio

    Seville, 41013

    Not yet recruiting

Other trials in Spain

France14 sites, 14 recruiting

  • Centre Francois Baclesse

    Caen, 14076

    Not yet recruiting

  • Centre Georges Francois Leclerc

    Dijon, 21000

    Not yet recruiting

  • Centre Oscar Lambret

    Lille, 59020

    Not yet recruiting

  • Centre Leon Berard

    Lyon, 69008

    Not yet recruiting

  • Institut Paoli-Calmettes

    Marseille, 13009

    Not yet recruiting

  • ICM - Institut Regional du Cancer de Montpellier

    Montpellier, 34298

    Not yet recruiting

  • Centre Antoine-Lacassagne

    Nice, 06819

    Not yet recruiting

  • CHU de Nimes

    Nîmes, 30029

    Not yet recruiting

  • Institut Curie

    Paris, 75005

    Not yet recruiting

  • Centre Eugene Marquis

    Rennes, 35402

    Not yet recruiting

  • Institut de Cancerologie de l'Ouest - site St-Herblain

    Saint-Herblain, 44805

    Not yet recruiting

  • Oncopole Claudius Regaud

    Toulouse, 31059

    Not yet recruiting

  • Institut de Cancerologie de Lorraine - Alexis Vautrin

    Vandœuvre-lès-Nancy, 54511

    Not yet recruiting

  • Institut Gustave Roussy

    Villejuif, 94805

    Not yet recruiting

Other trials in France

United States12 sites, 12 recruiting

  • University of Colorado Denver - School of Medicine - Anschutz Medical Campus

    Aurora, Colorado, 80045

    Not yet recruiting

  • Massachusetts General Hospital

    Boston, Massachusetts, 02114

    Not yet recruiting

  • Dana-Farber Cancer Institute

    Boston, Massachusetts, 02216

    Not yet recruiting

  • University of Texas Southwestern

    Dallas, Texas, 75244

    Not yet recruiting

  • Cedars-Sinai Medical Center - Samuel Oschin Comprehensive Cancer Institute

    Los Angeles, California, 90048

    Not yet recruiting

  • The West Cancer Center

    Memphis, Tennessee, 38138

    Not yet recruiting

  • SCRI Oncology Partners

    Nashville, Tennessee, 37203

    Not yet recruiting

  • Yale University School of Medicine - Yale Cancer Center

    New Haven, Connecticut, 06510

    Not yet recruiting

  • David H. Koch Center for Cancer Care at Memorial Sloan Kettering Cancer Center

    New York, New York, 10065

    Recruiting

  • Virginia Oncology Associates

    Norfolk, Virginia, 23502

    Not yet recruiting

  • Compass Oncology - Rose Quarter Cancer Center

    Portland, Oregon, 97227

    Not yet recruiting

  • Stanford Medicine Cancer Center

    Stanford, California, 94305

    Not yet recruiting

Other trials in United States

Japan10 sites, 10 recruiting

  • National Cancer Center Hospital

    Chuo-ku, Tokyo, 104-0045

    Recruiting

  • National Hospital Organization Kyushu Cancer Center

    Fukuoka, 811-1395

    Not yet recruiting

  • Fukushima Medical University Hospital

    Fukushima, 960-1295

    Recruiting

  • Kansai Medical University Hospital

    Hirakata, Osaka, 573-1191

    Not yet recruiting

  • Tokai University Hospital

    Isehara, Kanagawa, 259-1193

    Recruiting

  • National Cancer Center Hospital East

    Kashiwa, Chiba, 277-8577

    Not yet recruiting

  • Cancer Institute Hospital of JFCR

    Koto-ku, Tokyo, 135-8550

    Recruiting

  • Osaka International Cancer Institute

    Osaka, 541-8567

    Not yet recruiting

  • Showa Medical University Hospital

    Shinagawa-ku, Tokyo, 142-8666

    Not yet recruiting

  • Kanagawa Cancer Center

    Yokohama, Kanagawa, 241-8515

    Not yet recruiting

Other trials in Japan

Italy7 sites, 7 recruiting

  • Centro Riferimento Oncologico - Aviano

    Aviano, 33081

    Not yet recruiting

  • IRCCS Istituto Romagnolo per lo Studio dei Tumori Dino Amadori - IRST S.r.l.

    Meldola, 47014

    Not yet recruiting

  • Fondazione IRCCS Istituto Nazionale dei Tumori

    Milan, 20133

    Not yet recruiting

  • Istituto Europeo di Oncologia

    Milan, 20141

    Not yet recruiting

  • Fondazione IRCCS San Gerardo dei Tintori

    Monza, 20900

    Not yet recruiting

  • Istituto Oncologico Veneto-I.R.C.C.S. - Ospedale Busonera

    Padova, 35128

    Not yet recruiting

  • Azienda Ospedaliero Universitaria Pisana

    Pisa, 56126

    Not yet recruiting

Other trials in Italy

South Korea5 sites, 5 recruiting

  • Seoul National University Bundang Hospital

    Seongnam-si, 13620

    Not yet recruiting

  • Seoul National University Hospital

    Seoul, 03080

    Not yet recruiting

  • Severance Hospital, Yonsei University Health System

    Seoul, 03722

    Not yet recruiting

  • Asan Medical Center

    Seoul, 05505

    Not yet recruiting

  • Samsung Medical Center

    Seoul, 06351

    Recruiting

Other trials in South Korea

Taiwan5 sites, 5 recruiting

  • Taichung Veterans General Hospital

    Taichung, 40705

    Recruiting

  • National Cheng Kung University Hospital

    Tainan, 704

    Not yet recruiting

  • National Taiwan University Hospital

    Taipei, 10016

    Not yet recruiting

  • Taipei Veterans General Hospital

    Taipei, 11217

    Not yet recruiting

  • Koo Foundation Sun Yat-Sen Cancer Center

    Taipei, 112

    Not yet recruiting

Other trials in Taiwan

Belgium2 sites, 2 recruiting

  • Cliniques Universitaires Saint-Luc

    Brussels, 1200

    Not yet recruiting

  • UZ Leuven

    Leuven, 3000

    Not yet recruiting

Other trials in Belgium

About this study

Official title: A Phase 1b/2, Multicenter, Open-label, Dose Regimen Determination and Dose Expansion Trial to Evaluate the Safety, Tolerability, Anti-tumor Activity, and an Optimal Dose Regimen of Patritumab Deruxtecan (HER3-DXd) With Trastuzumab Deruxtecan (T-DXd) in Participants With Hormone Receptor Positive, HER2-low or HER2-ultralow, Unresectable or Metastatic Breast Cancer (HERTHENA-Breast02)

The primary purpose of the study is to assess the safety, tolerability, and anti-tumor activity of HER3-DXd and T-DXd in the combination dosing regimens in participants with hormone receptor positive, HER2-low or HER2-ultralow, unresectable, or metastatic breast cancer.

Being tested
Patritumab deruxtecan, Trastuzumab deruxtecan
Medical subject headings
Breast Neoplasms

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Patritumab deruxtecanDrug

    Also called U31402, HER3-DXd

    Intravenous administration as determined by treatment arm.

  • Trastuzumab deruxtecanDrug

    Also called DS8201a, T-DXd

    Intravenous administration as determined by treatment arm.

Study groups in NCT07701941
Study groupRoleWhat they receive
Part 1: Arm 1: Dose Regimen DeterminationExperimentalParticipants with unresectable or metastatic breast cancer (mBC) will receive T-DXd and HER3-DXd in combination regimen A until disease progression, death, unacceptable toxicity, or trial close.
Receives: Drug: Patritumab deruxtecan; Drug: Trastuzumab deruxtecan
Part 1: Arm 2: Dose Regimen DeterminationExperimentalParticipants with unresectable or mBC will receive T-DXd and HER3-DXd in combination regimen B until disease progression, death, unacceptable toxicity, or trial close.
Receives: Drug: Patritumab deruxtecan; Drug: Trastuzumab deruxtecan
Part 2: Arm 3: Dose ExpansionExperimentalParticipants with unresectable or mBC will receive T-DXd and HER3-DXd in a combination regimen based on the available Part 1 data until disease progression, death, unacceptable toxicity, or trial close.
Receives: Drug: Patritumab deruxtecan; Drug: Trastuzumab deruxtecan
Part 2: Arm 4: MonotherapyActive comparatorParticipants with unresectable or mBC will receive T-DXd monotherapy until disease progression, death, unacceptable toxicity, or trial close.
Receives: Drug: Trastuzumab deruxtecan

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Part 1: Number of Participants With at Least One Treatment-emergent Adverse Event (TEAE) and Serious Adverse Event (SAE)

    Adverse event(AE): any untoward medical occurrence in a participant administered pharmaceutical product (PP) and which does not necessarily have a causal relationship with the treatment.AE can therefore be any unfavorable and unintended sign(including an abnormal laboratory finding, for example),symptom,or disease temporally associated with the use of PP, whether or not considered related to the PP.Pre-existing conditions which worsen during study are also considered as AEs.SAE:any AE that fulfilled any of following criteria:fatal,life-threatening,required inpatient hospitalisation or prolongation of existing hospitalization,resulted in persistent or significant disability/incapacity,was congenital anomaly/birth defect, medically significant or required intervention to prevent any of the other outcomes listed here. TEAEs:AEs with start or worsening date during the on-treatment period(from 1st dose date of trial intervention to 47 days after the last dose date of trial intervention).

    Measured: Up to approximately 4.5 years

  2. Part 2: Objective Response Per Response Evaluation Criteria in Solid Tumours Version 1.1 (RECIST v.1.1) as Assessed by the Investigator

    Objective response is defined as participants with a best overall response (BOR) of confirmed complete response (CR) or confirmed partial response (PR), as assessed by investigator per RECIST v1.1.

    Measured: Up to approximately 4.5 years

Secondary outcomes (25)

  1. Part 1: Objective Response Per RECIST v.1.1 as Assessed by the Investigator

    Objective response is defined as participants with a BOR of confirmed CR or confirmed PR, as assessed by investigator per RECIST v1.1.

    Measured: Up to approximately 6 years

  2. Part 2: Number of Participants With at Least One TEAE and SAE

    AE: any untoward medical occurrence in a participant administered pharmaceutical product (PP) and which does not necessarily have a causal relationship with the treatment.AE can therefore be any unfavorable and unintended sign(including an abnormal laboratory finding, for example),symptom,or disease temporally associated with the use of PP, whether or not considered related to the PP.Pre-existing conditions which worsen during study are also considered as AEs.SAE:any AE that fulfilled any of following criteria:fatal,life-threatening,required inpatient hospitalisation or prolongation of existing hospitalization,resulted in persistent or significant disability/incapacity,was congenital anomaly/birth defect, medically significant or required intervention to prevent any of the other outcomes listed here. TEAEs:AEs with start or worsening date during the on-treatment period(from 1st dose date of trial intervention to 47 days after the last dose date of trial intervention).

    Measured: Up to approximately 6 years

  3. Parts 1 and 2: Disease Control Per RECIST v.1.1 as Assessed by the Investigator

    Disease control is defined as participants with a BOR of confirmed CR, confirmed PR, or SD per RECIST v1.1.

    Measured: Up to approximately 6 years

  4. Parts 1 and 2: Duration of Response (DoR) Per RECIST v.1.1 as Assessed by the Investigator

    DoR is defined as the time (month) from date of initial response (CR or PR) to the earlier date of the first objective documentation of radiographic disease progression or death due to any cause.

    Measured: Up to approximately 6 years

  5. Parts 1 and 2: Clinical Benefit Per RECIST v.1.1 as Assessed by Investigator

    Clinical benefit is defined as participants with a BOR of confirmed CR, confirmed PR, or SD lasting ≥183 days, per RECIST v1.1.

    Measured: Up to approximately 6 years

  6. Parts 1 and 2: Progression-free Survival (PFS) Per RECIST v.1.1 as Assessed by Investigator

    PFS by investigator is defined as the time (month) from the date of randomization to the earlier date of the first objective documentation of radiographic disease progression as assessed by investigator per RECIST v1.1 or death due to any cause.

    Measured: Up to approximately 6 years

  7. Parts 1 and 2: Time to Response (TTR) Per RECIST v.1.1 as Assessed by Investigator

    TTR is defined as the time (months) from the start date of study treatment to the date of the first documentation of response (CR or PR). TTR will be calculated for responders only.

    Measured: Up to approximately 6 years

  8. Parts 1 and 2: Overall Survival (OS)

    OS is defined as the time (month) from the date of randomization to the date of death due to any cause.

    Measured: Up to approximately 6 years

  9. Part 1: Maximum Serum Concentration (Cmax) of Anti-HER3 Antibody Conjugate Deruxtecan (HER3-ac-DXd)

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  10. Part 1: Cmax of Total Anti-HER3 Antibody Liquid Chromatography-mass Spectrometry (LC-MS)

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  11. Part 1: Cmax of T-DXd

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  12. Part 1: Cmax of Total Anti-HER2 Antibody

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  13. Part 1: Cmax of Released Payload (DXd)

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  14. Part 1: Trough Serum Concentration (Ctrough) of Anti-HER3-ac-DXd

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  15. Part 1: Ctrough of Total Anti-HER3 antibody LC-MS

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  16. Part 1: Ctrough of T-DXd

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  17. Part 1: Ctrough of Total Anti-HER2 Antibody

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  18. Part 1: Ctrough of Released Payload (DXd)

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  19. Part 1: Time to Reach Maximum Serum Concentration (Tmax) of Anti-HER3-ac-DXd

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  20. Part 1: Tmax of Total Anti-HER3 Antibody LC-MS

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  21. Part 1: Tmax of T-DXd

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  22. Part 1: Tmax of Total Anti-HER2 Antibody

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  23. Part 1: Tmax of Released Payload (DXd)

    Measured: Pre-dose and post-dose at multiple timepoints during each cycle, up to approximately 6 years (Cycle length=21 days)

  24. Part 2: Correlation Between HER3 Protein Expression and Efficacy

    HER3 protein expression in tumor tissue as determined by immunohistochemistry (IHC) and correlation with ORR, DoR, and PFS.

    Measured: Up to approximately 6 years

  25. Part 2: Correlation Between HER2 Protein Expression and Efficacy

    HER2 protein expression in tumor tissue as determined by IHC and correlation with ORR, DoR, and PFS.

    Measured: Up to approximately 6 years

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted14 Jul 2026
  2. Study start17 Sep 2026
  3. Primary completion1 Jan 2031 (estimated)
  4. Study completion1 May 2032 (estimated)

Resources

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 1/2
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Masking
None (open label)
Enrolment
220 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT07701941
Sponsor's protocol ID
U31402-287
Other IDs
2024-517541-14-00
Status last verified
Sep 2026
First submitted
8 Jul 2026
Last updated
1 Oct 2026
Results posted
No
Data monitoring committee
No
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Yes: De-identified individual participant data (IPD) on completed studies and applicable supporting clinical trial documents may be available upon request at https://vivli.org/. In cases where clinical trial data and supporting documents are provided pursuant to our company policies and procedures, Daiichi Sankyo will continue to protect the privacy of our clinical trial participants. Details on data sharing criteria and the procedure for requesting access can be found at this web address: https://vivli.org/ourmember/daiichi-sankyo/

Questions about this trial

What is this clinical trial studying?

A Phase 1/2 study testing Patritumab deruxtecan and Trastuzumab deruxtecan in people with Hormone Receptor Positive and HER2-low or HER2-ultralow, run by Daiichi Sankyo at 72 sites in 8 countries.

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 18 inclusion and 35 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: looking for participants now, as of the sponsor's last update on 1 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 72 sites in Spain, France, United States, Japan, Italy and 3 more countries. 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 combined phase mean?

Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

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?

Contact Daiichi Sankyo Contact for Clinical Trial Information (9089926400, CTRinfo_us@daiichisankyo.com), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Part 1: Number of Participants With at Least One Treatment-emergent Adverse Event (TEAE) and Serious Adverse Event (SAE) (time frame: Up to approximately 4.5 years). The study lists 2 primary outcomes in all. 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 NCT07701941.

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 1 Oct 2026.

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