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RecruitingInterventionalPhase 1/Phase 2

LIGHTBEAM-U01 Substudy 01C: A Phase 1/2 Substudy to Evaluate the Safety and Efficacy of Patritumab Deruxtecan in Pediatric Participants With Relapsed or Refractory Solid Tumors

NCT ID: NCT06941272Sponsor: Merck Sharp & Dohme LLCLast updated: 2026-05-12

Summary

Researchers are looking for new ways to treat children with hepatoblastoma or rhabdomyosarcoma (RMS) that has relapsed or is refractory: * Hepatoblastoma is a common liver cancer in babies and very young children * RMS is a cancer that starts in muscle cells, often in a child's head and neck, bladder, arms, or legs * Relapsed means the cancer came back after treatment * Refractory means the cancer did not respond (get smaller or go away) to treatment The study treatment HER3-DXd (also known as MK-1022 or patritumab deruxtecan) is an antibody-drug conjugate (ADC). An ADC attaches to a protein on cancer cells and delivers treatment to destroy those cells. The goals of this study are to learn: * About the safety of HER3-DXd in children and if they tolerate it * What happens to HER3-DXd in children's bodies over time * If children who receive HER3-DXd have the cancer get smaller or go away

Detailed description

This study will have 2 parts: a safety lead-in to demonstrate a tolerable safety profile and confirm a preliminary recommended phase 2 dose (RP2D) (Part 1) followed by an efficacy evaluation (Part 2)

Arms & interventions

  • BiologicalPatritumab Deruxtecan

    IV Infusion

Outcome measures

Primary

  • Part 1: Percentage of Participants Who Experience Dose-limiting Toxicities (DLTs)

    A DLT is any of a prespecified list of adverse events (AEs) that occur during Cycle 1 (up to 21 days) if attributed to the study treatment and not attributed to any other clearly identifiable cause. The percentage of participants who experience DLTs will be reported. Each cycle is 21 days.

    Time frame: Cycle 1 (up to approximately 21 days); each cycle is 21 days

  • Part 1: Percentage of Participants Who Experience an Adverse Event (AE)

    An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The percentage of participants who experience AEs will be reported.

    Time frame: Up to approximately 5 years

  • Part 1: Percentage of Participants Who Discontinue Study Treatment Due to an AE

    An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. The percentage of participants who discontinue study treatment due to an AE will be reported.

    Time frame: Up to approximately 5 years

  • Part 1: Area Under the Curve (AUC) of total anti-HER3 antibody liquid chromatography-mass spectrometry (LC-MS) in plasma

    Blood samples will be collected at specified intervals for the determination of AUC.

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 1: AUC of anti-HER3 antibody-conjugated DXd (anti-HER3-ac-DXd) in plasma

    Blood samples will be collected at specified intervals for the determination of AUC.

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 1: AUC of DXd in plasma

    Blood samples will be collected at specified intervals for the determination of AUC.

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 1: Maximum Concentration (Cmax) of anti-HER3 antibody LC-MS in plasma

    Blood samples will be collected at specified intervals for the determination of Cmax.

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 1: Cmax of anti-HER3-ac-DXd in plasma

    Blood samples will be collected at specified intervals for the determination of Cmax.

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 1: Cmax of DXd in plasma

    Blood samples will be collected at specified intervals for the determination of Cmax.

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 1: Concentration Immediately Before the Next Dose is Administered (Ctrough) of anti-HER3 antibody LC-MS in plasma

    Blood samples will be collected at specified intervals for the determination of Ctrough.

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 1: Ctrough of anti-HER3-ac-DXd

    Blood samples will be collected at specified intervals for the determination of Ctrough.

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 1: Ctrough of DXd in plasma

    Blood samples will be collected at specified intervals for the determination of Ctrough.

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 1 and Part 2: Objective Response Rate (ORR)

    ORR is defined as the percentage of participants with Complete Response (CR: disappearance of all target lesions) or Partial Response (PR: at least a 30% decrease in the sum of diameters of target lesions) per Response Evaluation Criteria In Solid Tumors Version 1.1 (RECIST 1.1). The percentage of participants who experience CR or PR as assessed by the investigator will be presented.

    Time frame: Up to approximately 5 years

Secondary

  • Part 2: Percentage of Participants Who Experience an AE

    Time frame: Up to approximately 5 years

  • Part 2: Percentage of Participants Who Discontinue Study Treatment Due to an AE

    Time frame: Up to approximately 5 years

  • Part 1 and Part 2: Disease Control Rate (DCR)

    Time frame: Up to approximately 5 years

  • Part 1 and Part 2: Time to Response (TTR)

    Time frame: Up to approximately 5 years

  • Part 1 and Part 2: Duration of Response (DOR)

    Time frame: Up to approximately 5 years

  • Part 1 and Part 2: Progression-free Survival (PFS)

    Time frame: Up to approximately 5 years

  • Part 1 and Part 2: Overall Survival (OS)

    Time frame: Up to approximately 5 years

  • Part 2: AUC of total anti-HER3 antibody LC-MS in plasma

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 2: AUC of anti-HER3-ac-DXd in plasma

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 2: AUC of DXd in plasma

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 2: Cmax of anti-HER3 antibody LC-MS in plasma

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 2: Cmax of anti-HER3-ac-DXd in plasma

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 2: Cmax of DXd in plasma

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 2: Ctrough of anti-HER3 antibody LC-MS in plasma

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 2: Ctrough of anti-HER3-ac-DXd in plasma

    Time frame: At designated timepoints (up to approximately 5 years)

  • Part 2: Ctrough of DXd in plasma

    Time frame: At designated timepoints (up to approximately 5 years)

Eligibility criteria

Sex: AllAge: 1 Month to 17 YearsHealthy volunteers: No
The main inclusion criteria include but are not limited to the following: * Has one of the following histologically confirmed advanced or metastatic solid tumors: Rhabdomyosarcoma (RMS), or Hepatoblastoma * Has progressed after at least 1 prior systemic treatment for RMS or hepatoblastoma and who has no satisfactory alternative treatment option (ie, is ineligible for other standard treatment regimens) * Participants who have adverse events (AEs) due to previous anticancer therapies must have recovered to Grade ≤1 or baseline. Participants with endocrine-related AEs who are adequately treated with hormone replacement or participants who have Grade ≤2 neuropathy are eligible. Participants with Grade ≤2 alopecia are also eligible * Hepatitis B surface antigen (HBsAg) positive participants are eligible if they have received hepatitis B virus (HBV) antiviral therapy and have undetectable HBV viral load * Participants with a history of hepatitis C virus (HCV) infection are eligible if HCV viral load is undetectable The main exclusion criteria include but are not limited to the following: * Has a history of (noninfectious) interstitial lung disease (ILD)/pneumonitis that required steroids or has current ILD/pneumonitis, and/or suspected ILD/pneumonitis that cannot be ruled out by standard diagnostic assessments * Has clinically severe respiratory compromise resulting from intercurrent pulmonary illness * Has a history of solid organ transplant * Has a history of allogeneic stem cell transplant * Has clinically significant corneal disease * Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis/leptomeningeal disease; participants with previously treated brain metastases may participate provided they are radiologically stable (ie, without evidence of progression) for at least 4 weeks * Has uncontrolled or significant cardiovascular disorder * Has a history of clinically significant congenital cardiac syndrome * Has a history of human immunodeficiency virus (HIV) infection * Has a known additional malignancy that is progressing or has required active treatment within the past 1 year * Has an active infection requiring systemic therapy * Has concurrent active hepatitis B (HBsAg positive and/or detectable HBV deoxyribonucleic acid \[DNA\]) and HCV defined as anti-HCV antibody (Ab) positive and detectable HCV ribonucleic acid \[RNA\]) infection * Has not adequately recovered from major surgery or have ongoing surgical complications

Study locations (17)

Childrens Hospital Los Angeles ( Site 3006)

Los Angeles, California, 90027

Recruiting
Study Coordinator · Contact
323-361-2121

Children's Hospital Colorado-Center for Cancer and Blood Disorders ( Site 3016)

Aurora, Colorado, 80045

Recruiting
Study Coordinator · Contact
720-777-1234

Yale New Haven Hospital ( Site 3012)

New Haven, Connecticut, 06510

Recruiting
Study Coordinator · Contact
203-785-4640

Johns Hopkins All Children's Hospital ( Site 3025)

St. Petersburg, Florida, 33701

Recruiting
Study Coordinator · Contact
727-767-4176

University of Iowa Health Care Holden Comprehensive Cancer Center ( Site 3017)

Iowa City, Iowa, 52242

Recruiting
Study Coordinator · Contact
319-356-2296

Dana-Farber Cancer Institute ( Site 3013)

Boston, Massachusetts, 02215

Recruiting
Study Coordinator · Contact
617-632-4580

Corewell Health ( Site 3001)

Grand Rapids, Michigan, 49503

Recruiting
Study Coordinator · Contact
616-486-0746

Children's Mercy Hospital ( Site 3024)

Kansas City, Missouri, 64108

Recruiting
Study Coordinator · Contact
816-302-6808

Rutgers Cancer Institute of New Jersey ( Site 3008)

New Brunswick, New Jersey, 08901

Recruiting
Study Coordinator · Contact
732-235-2465

Memorial Sloan Kettering Cancer Center ( Site 3010)

New York, New York, 10065

Recruiting
Study Coordinator · Contact
888-492-8401

New York Medical College ( Site 3023)

Valhalla, New York, 10595

Recruiting
Study Coordinator · Contact
914-614-4270

Sanford Fargo Medical Center-Roger Maris Cancer Center ( Site 3003)

Fargo, North Dakota, 58102

Recruiting
Study Coordinator · Contact
701-234-2000

Oregon Health and Science University ( Site 3004)

Portland, Oregon, 97239

Recruiting
Study Coordinator · Contact
503-494-8311

Children's Hospital of Philadelphia (CHOP) ( Site 3021)

Philadelphia, Pennsylvania, 19104

Recruiting
Study Coordinator · Contact
267-425-5544

Sanford Children's Hospital ( Site 3015)

Sioux Falls, South Dakota, 57117

Recruiting
Study Coordinator · Contact
605-312-1000

University of Texas-MD Anderson Cancer Center ( Site 3007)

Houston, Texas, 77030

Recruiting
Study Coordinator · Contact
713-792-5410

Intermountain - Primary Children's Hospital ( Site 3014)

Salt Lake City, Utah, 84113

Recruiting
Study Coordinator · Contact
801-662-4700