On December 1, the U.S. Food and Drug Administration (FDA) approved pralsetinib (Gavreto) for adult and pediatric patients 12 years of age and older with advanced or metastatic RET-mutant medullary thyroid cancer who require systemic therapy, or for patients with RET fusion–positive thyroid cancer who require systemic therapy and who are radioactive iodine–refractory (if radioactive iodine is appropriate).
ARROW Trial
Efficacy was investigated in the multicenter, open-label, multicohort ARROW clinical trial in patients whose tumors had RET gene alterations. Identification of RET gene alterations was prospectively determined in local laboratories using either next-generation sequencing, fluorescence in situ hybridization, or other tests.
The main efficacy outcome measures were overall response rate and response duration determined by a blinded independent review committee using Response Evaluation Criteria in Solid Tumors version 1.1. Efficacy for advanced or metastatic RET-mutant medullary thyroid cancer was evaluated in 55 patients who received prior treatment with cabozantinib or vandetanib. The overall response rate for these patients was 60% (95% confidence interval [CI] = 46%–73%); 79% of responding patients had responses lasting 6 months or longer. Efficacy was also evaluated in 29 patients with RET-mutant medullary thyroid cancer who did not receive prior treatment with cabozantinib or vandetanib. The overall response rate for these patients was 66% (95% CI = 46%–82%); 84% of patients had responses lasting 6 months or longer. Efficacy for patients with RET fusion–positive thyroid cancer was evaluated in nine patients who were radioactive iodine–refractory. The overall response rate was 89% (95% CI = 52%–100%); all responding patients had responses lasting 6 months or longer.
Adverse Events
The most common adverse reactions (≥ 25%) were constipation, hypertension, fatigue, musculoskeletal pain, and diarrhea. The most common grade 3–4 laboratory abnormalities (≥ 2%) were decreased lymphocytes, decreased neutrophils, decreased hemoglobin, decreased phosphate, decreased calcium, decreased sodium, increased aspartate aminotransferase, increased alanine aminotransferase, decreased platelets, and increased alkaline phosphatase.
The recommended pralsetinib dose in adults and pediatric patients 12 years and older is 400 mg orally once daily on an empty stomach, with no food intake for at least 2 hours before and at least 1 hour after taking pralsetinib.
