NTRK kinase domain mutations in cancer variably impact sensitivity to type I and type II inhibitors

Tyrosine kinase domains dynamically fluctuate between two main structural forms that are referred to as type I (DFG-in) or type II (DFG-out) conformations. Comprehensive data comparing type I and type II inhibitors are currently lacking for NTRK fusion-driven cancers. Here we used a type II NTRK inhibitor, altiratinib, as a model compound to investigate its inhibitory potential for larotrectinib (type I inhibitor)-resistant mutations in NTRK. Our study shows that a subset of larotrectinib-resistant NTRK1 mutations (V573M, F589L and G667C) retains sensitivity to altiratinib, while the NTRK1V573M and xDFG motif NTRK1G667C mutations are highly sensitive to type II inhibitors, including altiratinib, cabozantinib and foretinib. Moreover, molecular modeling suggests that the introduction of a sulfur moiety in the binding pocket, via methionine or cysteine substitutions, specifically renders the mutant kinase hypersensitive to type II inhibitors. Future precision treatment strategies may benefit from selective targeting of these kinase mutants based on our findings.

Acute encephalopathy with combination dabrafenib/trametinib therapy

Biomarkers have improved the clinical application of numerous targeted agents used to treat solid tumors. In melanoma, the finding that approximately 60% of tumor cells harbor specific Val600 mutations of BRAF has increased the likelihood of response to certain agents aimed at inhibiting the mutant kinase. While dabrafenib is an effective anti-tumor agent with acceptable tolerability in patients with BRAF-mutated melanoma, we report the development (and outcome) of a previously unpublished acute toxic reaction observed in a patient receiving the drug.