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NCT Number: NCT07700758

A Study of Belzutifan in Adolescent Participants With Solid Tumors (MK-9999-01E/LIGHTBEAM-U01)

Researchers are looking for new ways to treat adolescents with locally advanced, unresectable, or metastatic solid tumors. Participants were enrolled into pheochromocytoma/paraganglioma (PPGL), wild type gastrointestinal stromal tumor (wtGIST), and Von Hippel-Lindau (VHL) disease-associated localized tumors cohorts:

* PPGL are rare cancers that start in cells that make hormones in the adrenal glands * wtGIST is a less common type of cancer that starts in the digestive tract. Wild type means it does not have certain gene mutations (changes) * VHL disease-associated localized tumors are rare tumors caused by a certain gene mutation that may be passed down from parents to children * Locally advanced means the cancer has spread into nearby tissue * Unresectable means the cancer cannot be removed by surgery * Metastatic means the cancer has spread to other parts of the body

The goal of the study is to learn about the safety of belzutifan and if people tolerate it.

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Key information

Conditions

Malignant Neoplasm Neoplasms

Age range

12 year–17 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 2

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

The main inclusion criteria include but are not limited to the following:

  • Has a diagnosis of one of the following: locally advanced, unresectable, or metastatic pheochromocytoma/paraganglioma or wild-type gastrointestinal stromal tumors, or localized tumors associated with von Hippel-Lindau disease
  • Has measurable disease per RECIST 1.1

Exclusion criteria

The main exclusion criteria include but are not limited to the following:

  • Has a pulse oximeter reading <92% at rest, requires intermittent supplemental oxygen, or requires chronic supplemental oxygen
  • Has clinically significant cardiac disease or electrocardiogram indicating uncontrolled cardiac condition or has congenital long QT syndrome
  • Has a history of human immunodeficiency virus infection
  • Has received prior treatment with any hypoxia inducible factor-2α inhibitor, including belzutifan
  • Has had an allogenic tissue/solid organ transplant
  • Has a history of autologous stem cell transplant within 6 months of start of study intervention
  • Has known additional malignancy that is progressing or has required active treatment within the past 2 years
  • Has known active central nervous system metastases and/or carcinomatous meningitis
  • Has an active infection requiring systemic therapy

Treatment and study plan

Belzutifan

Drug

Administered once daily via oral tablet

Other names: MK-6482, PT2977, WELIREG®

Primary outcomes

  1. Number of Participants Who Experience One or More Adverse Events (AEs)

    Time frame: Up to approximately 5 years

    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 number of participants that experience AEs will be reported.

  2. Number of Participants Who Discontinue Study Intervention Due to an AE

    Time frame: Up to approximately 5 years

    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 number of participants that discontinue study intervention due to an AE will be reported.

Secondary outcomes

  1. Area Under the Concentration-Time Curve From Time 0 to 24 hours of Belzutifan

    Time frame: At designated timepoints (up to 5 weeks)

    Blood samples will be collected at specified intervals to determine the area under the concentration-time curve from time 0 to 24 hours of belzutifan.

  2. Minimum Plasma Concentration (Cmin) of Belzutifan

    Time frame: At designated timepoints (up to 5 weeks)

    Blood samples will be collected at specified intervals to determine the Cmin of belzutifan.

  3. Maximum Plasma Concentration (Cmax) of Belzutifan

    Time frame: At designated timepoints (up to 5 weeks)

    Blood samples will be collected at specified intervals to determine the Cmax of belzutifan.

  4. Objective Response Rate (ORR)

    Time frame: Up to approximately 5 years

    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 investigator will be reported.

  5. Duration of Response (DOR)

    Time frame: Up to approximately 5 years

    For participants who demonstrate a confirmed 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), DOR is defined as the time from first documented evidence of CR or PR until progressive disease (PD) or death. Per RECIST 1.1, PD is defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of at least 5 mm. The appearance of one or more new lesions is also considered PD. DOR as assessed by investigator will be reported.

Sponsors and collaborators

Lead sponsor

Merck Sharp & Dohme LLC

Industry

Registry information

Official study title

LIGHTBEAM-U01 Substudy 01E: A Phase 2 Substudy to Evaluate the Safety and Efficacy of Belzutifan in Participants With Solid Tumors

Important dates

Study start
2026
Primary completion
2034
Study completion
2034
First posted
Jul 14, 2026
Registry last updated
Jul 14, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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