Multikinase Inhibitors for the Treatment of Asymptomatic Radioactive Iodine-Refractory Differentiated Thyroid Cancer: Global Noninterventional Study (RIFTOS MKI).

Background: Sorafenib and lenvatinib are multikinase inhibitors (MKIs) approved for patients with radioactive iodine-refractory (RAI-R) differentiated thyroid cancer (DTC). There is no consensus on when to initiate MKI treatment. The objective of this study was to evaluate time to symptomatic progression (TTSP) in patients with RAI-R DTC for whom the decision to treat with an MKI was made at study entry. Methods: International, prospective, open-label, noninterventional cohort study (NCT02303444). Eligible patients had asymptomatic progressive RAI-R DTC, with ≥1 lesion ≥1 cm in diameter and life expectancy ≥6 months. The decision to treat with an MKI was at the treating physician's discretion. Primary endpoint was TTSP from study entry. Two cohorts were evaluated: patients for whom a decision to initiate an MKI was made at study entry (Cohort 1) and patients for whom there was a decision not to initiate an MKI at study entry (Cohort 2). Cohorts were compared descriptively. Results: The full analysis set (FAS) comprised 647 patients. The median duration of observation was 35.5 months (range <1-59.4). Of 344 MKI-treated patients, 209 received sorafenib, 191 received lenvatinib, and 19 received another MKI at some point. Median TTSP was 55.4 months (interquartile range [IQR] 18.6-not estimable [NE]) overall, 55.4 months (IQR 15.2-NE) in Cohort 1 (n = 169), and 51.4 months (IQR 20.0-NE) in Cohort 2 (n = 478). TTSP ≥36 months was achieved in 64.5% of patients overall, 59.5% of patients in Cohort 1, and 66.4% of patients in Cohort 2. Median overall survival from classification as RAI-R was 167 months and median progression-free survival from start of MKI therapy was 19.2 months and from start of sorafenib therapy 16.7 months. Among sorafenib-treated patients, 70% had dose modifications, 35% had a dose reduction, 89% experienced ≥1 treatment-emergent adverse event (TEAE), and 82% experienced ≥1 drug-related TEAE. Conclusions: This real-world study provides valuable insight into outcomes in patients with asymptomatic, progressive RAI-R DTC under observation or receiving MKI treatment. TTSP in the FAS provides insight into the current prognosis for patients with RAI-R DTC in the era of MKIs. Registration: NCT02303444.

Experience of sorafenib treatment in differentiated thyroid cancer from Taiwan.

BACKGROUND: Sorafenib has been shown to prolong the progression free survival (PFS) of advanced radioiodine (RAI) refractory differentiated thyroid cancer (DTC) and has been approved by the FDA as the result of the phase III DECISION trial. Sorafenib has been reimbursed for the treatment of RAI refractory DTC in Taiwan since Jan 2017. High percentage of adverse events (AE) was noted in DECISION trial. We conducted a study to show the real-world experience of sorafenib in Taiwan. METHODS: We retrospectively collected the clinical data, including dose, AE, and PFS of sorafenib, of the DTC patients who received sorafenib treatment in National Cheng Kung University Hospital and China Medical University Hospital by chart review from 2012 to 2018. RESULTS: Thirty-six advanced DTC patients with progression were included in this study. The starting dose of sorafenib in most patients was 200 mg twice daily and the mean daily maintenance dose was 433 mg. Five patients had partial response (13.9%) and 28 patients had stable disease (77.8%). The median PFS was 17.3 months (95% confidence interval: 11.9-33.6 months). Daily maintenance dose ≥ 600 mg was associated with better PFS (median PFS, not reached). The most common toxicity of sorafenib was hand foot skin reaction (69%), followed by diarrhea (42%), and skin rash (33%). Most of the toxicities were grade I/II. CONCLUSION: Higher maintenance dose of sorafenib is associated with longer PFS while starting from half dose is feasible to minimize the incidence of high grade toxicities in the real-world use of sorafenib.

Discovery of Conformational Control Inhibitors Switching off the Activated c-KIT and Targeting a Broad Range of Clinically Relevant c-KIT Mutants.

Drug resistance due to acquired mutations that constitutively activate c-KIT is a significant challenge in the treatment of patients with gastrointestinal stromal tumors (GISTs). Herein, we identified 1-(5-ethyl-isoxazol-3-yl)-3-(4-{2-[6-(4-ethylpiperazin-1-yl)pyrimidin-4-ylamino]-thiazol-5-yl}phenyl)urea (10a) as a potent inhibitor against unactivated and activated c-KIT. The binding of 10a induced rearrangements of the DFG motif, αC-helix, juxtamembrane domain, and the activation loop to switch the activated c-KIT back to its structurally inactive state. To the best of our knowledge, it is the first structural evidence demonstrating how a compound can inhibit the activated c-KIT by switching back to its inactive state through a sequence of conformational changes. Moreover, 10a can effectively inhibit various c-KIT mutants and the proliferation of several GIST cell lines. The distinct binding features and superior inhibitory potency of 10a, together with its excellent efficacy in the xenograft model, establish 10a as worthy of further clinical evaluation in the advanced GISTs.