Larotrectinib to Enhance RAI Avidity in Differentiated Thyroid Cancer

Phase 2

Recruiting

• Conditions: Pediatric Cancer; Differentiated Thyroid Cancer; Cancer, Thyroid; Cancer
• Interventions: Drug: Larotrectinib monotherapy; Radiation: 131I therapy

• Registration Number: NCT05783323
• Lead Sponsor: Children's Hospital of Philadelphia

Brief Summary

Papillary thyroid cancer (PTC) is the most common form of differentiated thyroid cancer (DTC). The traditional first line treatment for patients with advanced DTC after surgical resection is radioactive iodine (RAI) therapy. However, less than a quarter of patients with lung metastases will achieve a complete response to RAI therapy, and this therapy carries the risk of pulmonary fibrosis and an increasingly recognized risk of secondary malignancies.

Detailed Description

This is an open label, non-randomized study to evaluate the efficacy and safety of the combination of larotrectinib followed by 131I therapy for patients with NTRK fusion differentiated thyroid cancer. The primary Phase II objective will be to evaluate the pulmonary structural response rate at 18 months to the combination of larotrectinib given for 6-months followed by 131I therapy.

Study Timeline

• Study First Submitted: 2023-03-02
• Study First Submitted QC: 2023-03-13
• Study First Posted: 2023-03-24
• Study Start: 2024-02-14
• Status Verified: 2025-04
• Last Update Submitted: 2025-04-09
• Last Update Posted: 2025-04-10
• Primary Completion: 2026-10-01
• Study Completion: 2027-10-01

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 13

Inclusion Criteria

1. Age ≥ 1 year

2. Histologic diagnosis of a differentiated thyroid cancer, s/p thyroidectomy and adequate local therapy (e.g., lymph node dissection as per standard of care) for metastatic disease in the neck in the opinion of the treating investigator

3. Anatomically evaluable disease on chest CT meeting one of the following criteria (obtained within 90 days of enrollment):

   A. multiple (> 10) noncalcified solid pulmonary nodules visible on CT and/or

   B. enlarging, discrete pulmonary nodules visible on CT of any number consistent with metastatic disease

4. Identification of an neurotrophic tyrosine receptor kinase (NTRK) (NTRK1, NTRK2, or NTRK3) gene fusion in a CLIA/CAP accredited laboratory without known kinase domain resistance mutation

5. Lansky/Karnofsky performance status ≥ 50%

6. Adequate Organ Function

   A. Bone Marrow Function:

   • Peripheral absolute neutrophil count (ANC) ≥ 1000/mm3
   • Platelet count ≥ 100,000/mm3 (transfusion independent, defined as not receiving platelet transfusions for at least 7 days prior to enrollment)
   • Hemoglobin ≥ to 8.0 g/dL at baseline (may receive red blood cell (RBC) transfusions).

   B. Adequate Renal Function:

   Creatinine clearance or radioisotope glomerular filtration rate (GFR) ≥ 70 mL/min/1.73 m2 or a maximum serum creatinine based on age/gender as follows:

   Age Maximum Serum Creatinine (mg/dL) Male Female 1 to < 2 years 0.6 0.6 2 to < 6 years 0.8 0.8 6 to < 10 years 1 1 10 to < 13 years 1.2 1.2 13 to < 16 years 1.5 1.5

   ≥ 16 years 1.7 1.7

   C. Adequate Liver Function

   • Bilirubin (sum of conjugated + unconjugated) ≤ 1.5 x upper limit of normal (ULN) for age.
   • Serum glutamic-pyruvic transaminase (SGPT) (ALT) ≤ 135 U/L. For the purpose of this study, the ULN for SGPT is 45 U/L.
   • Serum albumin ≥ 2 g/dL

7. Female patients of reproductive potential must agree to use a highly effective contraceptive method for the duration of study therapy and for at least one month after the final dose of larotrectinib. Males of reproductive potential with a non-pregnant female partner of child-bearing potential must use a highly effective contraception for the duration of the study and for at least one month after the final dose of larotrectinib.

Exclusion Criteria

1. No prior systemic therapy for thyroid cancer, including tropomyosin receptor kinase (TRK) inhibitors or 131I.
2. Females who are pregnant or breastfeeding are excluded due to the potential risks of larotrectinib and RAI to the fetus/neonate.
3. Concurrent therapy: Patients currently receiving a strong CYP3A4 inducer or inhibitor are not eligible. Strong inducers or inhibitors of CYP3A4 should be avoided 14 days prior to treatment to the end of the study treatment.

Exclusion Criteria

Not provided

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
Larotrectinib monotherapy with 131I therapy	Larotrectinib monotherapy	Patients will receive larotrectinib monotherapy for 6 months at the FDA-approved dose. Patients will receive 131I therapy after 6 months of larotrectinib. Larotrectinib will be continued for 5 days after RAI therapy and then patients will enter a wait and see period off treatment. Patients who experience disease progression at any point while on larotrectinib will proceed to 131I therapy and discontinue larotrectinib.
Larotrectinib monotherapy with 131I therapy	131I therapy	Patients will receive larotrectinib monotherapy for 6 months at the FDA-approved dose. Patients will receive 131I therapy after 6 months of larotrectinib. Larotrectinib will be continued for 5 days after RAI therapy and then patients will enter a wait and see period off treatment. Patients who experience disease progression at any point while on larotrectinib will proceed to 131I therapy and discontinue larotrectinib.

Primary Outcome Measures

Name	Time	Method
Number of patients with complete pulmonary structural response	18 months	The primary endpoint is the complete pulmonary structural response rate to larotrectinib by modified Nies et al thyroid cancer response criteria.

Trial Locations

Locations (3)

Seattle Children's Hospital; 🇺🇸 Seattle, Washington, United States

Children's Hospital of Philadelphia; 🇺🇸 Philadelphia, Pennsylvania, United States

MD Anderson Cancer Center; 🇺🇸 Houston, Texas, United States