Substudy 01A: Zilovertamab Vedotin in Pediatric and Young Adult Participants With Hematologic Malignancies or Solid Tumors (MK-9999-01A/LIGHTBEAM-U01)

BIOLOGICAL

Zilovertamab vedotin

Administered via IV infusion

Part 1: Number of Participants from 1 to <18 years of Age Who Experience a Dose-Limiting Toxicity (DLT)

Time frame: Up to 42 days

Number of participants experiencing toxicities that are possibly, probably, or definitely related to study therapy; that meet pre-defined severity criteria; and result in a change in the given dose.

Part 1: Number of Participants from 1 to <18 years of Age Who Experience One or More Adverse Events (AEs)

Time frame: Up to approximately 54 months

An AE is defined as any untoward medical occurrence associated with the use of a drug in a participant, whether or not considered drug related. 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 medicinal product and does not imply any judgment about causality. The number of participants in Part 1 who experience at least 1 AE will be presented.

Part 1: Number of Participants from 1 to <18 years of Age Who Discontinue Study Treatment Due to AEs

Time frame: Up to approximately 54 months

An AE is defined as any untoward medical occurrence associated with the use of a drug in a participant, whether or not considered drug related. 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 medicinal product and does not imply any judgment about causality. The number of participants in Part 1 who discontinue study treatment due to an AE will be presented.

Part 1: Number of Participants from 1 to <18 years of Age Who Receive Dose Modification Due to AEs

Time frame: Up to approximately 54 months

An AE is defined as any untoward medical occurrence associated with the use of a drug in a participant, whether or not considered drug related. 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 medicinal product and does not imply any judgment about causality. The number of participants in Part 1 who receive a dose modification due to an AE will be presented.

Part 1 and Part 2: Objective Response (OR) for Participants with B-Cell Acute Lymphoblastic Leukemia (B-ALL)

Time frame: Up to approximately 54 months

OR for participants with B-ALL is defined as complete response (CR) or complete response with incomplete hematologic recovery (CRi) based on investigator's assessment per Ponte-di-Legno Consortium criteria. For Part 1 and Part 2, the OR for participants with B-ALL as assessed by investigator will be presented.

Part 1 and Part 2: OR for Participants with Diffuse Large B-Cell Lymphoma (DLBCL)/Burkitt Lymphoma, Neuroblastoma, and Ewing Sarcoma

Time frame: Up to approximately 54 months

OR for participants with DLBCL/Burkitt lymphoma, neuroblastoma, and Ewing sarcoma is defined as complete response (CR) or partial response (PR) based on investigator's assessment per International Pediatric Non-Hodgkin Lymphoma (IPNHL) Response Criteria for participants with DLBCL/Burkitt lymphoma, per International Neuroblastoma Response Criteria (INRC) for neuroblastoma, and per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 for Ewing sarcoma. For Part 1 and Part 2, the OR for participants with DLBCL/Burkitt lymphoma, neuroblastoma, and Ewing sarcoma as assessed by investigator will be presented.

What is a clinical trial?

A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.

Is it safe to participate?

Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.

Will I be compensated?

Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.

Will I receive a placebo instead of treatment?

When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.

Can I leave a trial if I change my mind?

Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.

How long does a clinical trial last?

Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.