Entrectinib, a potent oral inhibitor of the tyrosine kinases TRKA/B/C, ROS1, and ALK, was evaluated in two Phase 1 studies in patients with advanced or metastatic solid tumors, including patients with active CNS disease. Here we summarize the overall safety and report the antitumor activity of entrectinib in a cohort of patients with tumors harboring NTRK1/2/3, ROS1, or ALK gene fusions, naïve to prior TKI treatment targeting the specific gene, and who were treated at doses that achieved therapeutic exposures consistent with the RP2D. Entrectinib was well tolerated, with predominantly Grades 1/2 adverse events that were reversible with dose modification. Responses were observed in NSCLC, colorectal cancer, mammary analog secretory carcinoma, melanoma, and renal cell carcinoma, as early as 4 weeks after starting treatment and lasting as long as > 2 years. Notably, a complete CNS response was achieved in a patient with SQSTM1-NTRK1-rearranged lung cancer.
Here, we describe the dramatic response of a patient with an ETV6-NTRK3-driven mammary analogue secretory carcinoma to treatment with a pan-Trk inhibitor, and the development of acquired resistance linked to a novel NTRK3 mutation that interferes with drug binding. This case emphasizes how molecular profiling can identify therapies for rare diseases and dissect mechanisms of drug resistance.
Introduction:Chromosomal rearrangements involving neurotrophic tyrosine kinase 1 (NTRK1) occur in a subset of non-small cell lung cancers (NSCLCs) and other solid tumor malignancies, leading to expression of an oncogenic TrkA fusion protein. Entrectinib (RXDX-101) is an orally available tyrosine kinase inhibitor, including TrkA. We sought to determine the frequency of NTRK1 rearrangements in NSCLC and to assess the clinical activity of entrectinib.Methods:We screened 1378 cases of NSCLC using anchored multiplex polymerase chain reaction (AMP). A patient with an NTRK1 gene rearrangement was enrolled onto a Phase 1 dose escalation study of entrectinib in adult patients with locally advanced or metastatic tumors (NCT02097810). We assessed safety and response to treatment.Results:We identified NTRK1 gene rearrangements at a frequency of 0.1% in this cohort. A patient with stage IV lung adenocrcinoma with an SQSTM1-NTRK1 fusion transcript expression was treated with entrectinib. Entrectinib was well tolerated, with no grade 3–4 adverse events. Within three weeks of starting on treatment, the patient reported resolution of prior dyspnea and pain. Restaging CT scans demonstrated a RECIST partial response (PR) and complete resolution of all brain metastases. This patient has continued on treatment for over 6 months with an ongoing PR.Conclusions:Entrectinib demonstrated significant anti-tumor activity in a patient with NSCLC harboring an SQSTM1-NTRK1 gene rearrangement, indicating that entrectinib may be an effective therapy for tumors with NTRK gene rearrangements, including those with central nervous system metastases.
In metastatic colorectal cancer (CRC), actionable genetic lesions represent potential clinical opportunities. NTRK1, 2, and 3 gene rearrangements encode oncogenic fusions of the tropomyosin-receptor kinase (TRK) family of receptor tyrosine kinases in different tumor types. The TPM3-NTRK1 rearrangement is a recurring event in CRC that renders tumors sensitive to TRKA kinase inhibitors in preclinical models. We identified abnormal expression of the TRKA protein in tumor and liver metastases of a CRC patient refractory to standard therapy. Molecular characterization unveiled a novel LMNA-NTRK1 rearrangement within chromosome 1 with oncogenic potential, and the patient was treated with the pan-TRK inhibitor entrectinib, achieving partial response with decrease in hepatic target lesions from 6.8 and 8.2cm in longest diameter to 4.7 and 4.3cm, respectively. To our knowledge, this is the first clinical evidence of efficacy for therapeutic inhibition of TRKA in a solid tumor, illuminating a genomic-driven strategy to identify CRCs reliant on this oncogene to be clinically targeted with entrectinib.
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