A phase I/II trial of sapanisertib in advanced anaplastic and radioiodine refractory differentiated thyroid carcinoma.

ABSTRACT

BACKGROUND: There are limited therapeutic options for patients with recurrent/metastatic anaplastic thyroid carcinoma (ATC), and radioiodine refractory (RAIR) differentiated thyroid carcinoma (DTC) refractory to multi-kinase inhibitors. This multi-center trial evaluated sapanisertib, a next generation oral kinase inhibitor of mTOR complexes 1/2, in ATC and RAIR DTC. METHODS: A safety run-in phase I was followed by non-randomized phase II trial in ATC, with an exploratory cohort in RAIR DTC. Primary endpoint was proportion of patients with ATC who were without disease progression at 4 months. Safety and survival outcomes were key secondary endpoints. RESULTS: Forty-six patients (20 ATC; 26 DTC) were enrolled including 40 (18 ATC; 22 DTC) who received recommended phase II dose of 5 mg daily. Eleven percent (2/18, 95% C.I. 1.4-34.7%) of patients with ATC were progression-free at 4 months, 22.2% (4/18) had stable disease as best response. Enrollment in the ATC cohort stopped early with 18 patients out of proposed 23 due to overall futility. One confirmed partial response (4.5%, 1/22) occurred in RAIR DTC, with stable disease in 63.6% (14/22) patients. Median progression-free survival was 1.6 (95% C.I. 0.9-2.8) months and 7.8 (2.0-not reached) months in ATC and DTC, respectively. Grade 3 treatment related adverse events occurred in 30% of patients who received the phase II dose, most common being anorexia, nausea, diarrhea, fatigue, skin rash and hyperglycemia. Genomic alterations in the PI3 K/AKT/mTOR pathway were not associated with response or PFS. CONCLUSIONS: Sapanisertib monotherapy did not meet the primary endpoint of this trial (proportion progression-free at 4 months) in ATC, and did not show clinically meaningfully activity. Clinical trials with alternative therapeutic strategies are needed. CLINICAL TRIAL REGISTRATION NCT02244463.