A Study of Ifinatamab Deruxtecan in Pediatric Participants With Relapsed or Refractory Solid Tumors (MK-9999-01D/LIGHTBEAM-U01)

Researchers are looking for new ways to treat children with relapsed or refractory solid tumors: * Relapsed means the cancer came back after treatment * Refractory means the cancer did not respond (get smaller or go away) to treatment * Solid tumors are cancers mostly in body organs and tissues, not in the blood or other body liquids The study treatment I-DXd (also known as MK-2400 or ifinatamab 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 I-DXd and if children younger than 12 years old tolerate it * How many children who receive I-DXd have the cancer get smaller or go away

NCT Number	NCT07630974
Lead Sponsor	Merck Sharp & Dohme LLC Collaborators: Daiichi Sankyo
Conditions	Malignant Neoplasm
Enrollment	134 participants
Start Date	2026-07-02
Primary Completion	2031-08-17 (estimated)
Study Completion	2031-08-17 (estimated)
Updated on ClinicalTrials.gov	2026-08-10