Abstract

Abstract Background This investigator-initiated phase II trial aimed to evaluate the efficacy of cabozantinib in combination with nivolumab and ipilimumab (CaboNivoIpi) in previously treated patients with radioactive iodine (RAI)-refractory differentiated thyroid cancer (DTC) (NCT03914300). Methods Eligible patients with RAI-refractory DTC who progressed on 1 prior line of VEGFR-targeted therapy received a 2-week run-in of cabozantinib monotherapy followed by CaboNivoIpi for 4 cycles (cycle length = 6 weeks), followed by cabozantinib plus nivolumab (cycle length = 4 weeks) until disease progression. The primary endpoint was objective response rate (ORR) within the first 6 months of treatment. A Simon optimal 2-stage design allowed for an interim analysis after accrual of 10 evaluable patients. At least 5 responses were needed to proceed to stage 2. Results Among 11 patients enrolled, the median age was 69 years. Prior VEGFR-targeted therapies included lenvatinib, pazopanib, and sorafenib plus everolimus. Median follow-up was 7.9 months. Among 10 evaluable patients, ORR within the first 6 months of treatment was 10% (1 partial response). Median progression-free survival was 9 months [95% CI: 3.0, not reached] and median overall survival was 19.2 months [(95% CI: 4.6, not reached]. Grade 3/4 treatment-related adverse events (AEs) were noted in 55% (6/11) and grade 5 AEs in 18% (2/11) of patients. The most common treatment-related AE was hypertension. The study did not reach its prespecified efficacy threshold. Conclusion CaboNivoIpi had low ORRs and a high rate of grade ≥3 treatment-related AEs. Clinical Trial Registration NCT03914300