On December 1, 2020, the Food and Drug Administration approved pralsetinib for adult and paediatric patients 12 years of age and older with advanced or metastatic RET-mutant medullary thyroid cancer (MTC) who require systemic therapy or RET fusion-positive thyroid cancer who require systemic therapy and who are radioactive iodine-refractory (if radioactive iodine is appropriate).
Efficacy was investigated in a multicenter, open label, multi-cohort clinical trial (ARROW, NCT03037385) in patients whose tumours had RET gene alterations.
Identification of RET gene alterations was prospectively determined in local laboratories using either next generation sequencing, fluorescence in situ hybridisation, or other tests.
The main efficacy outcome measures were overall response rate (ORR) and response duration determined by a blinded independent review committee using RECIST 1.1. Efficacy for advanced or metastatic RET-mutant MTC was evaluated in 55 patients who received prior cabozantinib or vandetanib.
The ORR for these patients was 60% (95% CI: 46%, 73%); 79% of responding patients had responses lasting 6 months or longer.
Efficacy was also evaluated in 29 patients with RET-mutant MTC who did not receive prior cabozantinib or vandetanib.
The ORR 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 9 patients who were radioactive iodine-refractory. The ORR was 89% (95% CI: 52%, 100%); all responding patients had responses lasting 6 months or longer.
The most common adverse reactions (≥25%) were constipation, hypertension, fatigue, musculoskeletal pain, and diarrhoea.
The most common Grade 3-4 laboratory abnormalities (≥2%) were decreased lymphocytes, decreased neutrophils, decreased haemoglobin, decreased phosphate, decreased calcium (corrected), decreased sodium, increased aspartate aminotransferase (AST), increased alanine aminotransferase (ALT), decreased platelets, and increased alkaline phosphatase.
The recommended pralsetinib dose in adults and paediatric 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.