NTRK FUSIONS: A pooled analysis of 3 clinical trials (n=50 total subjects) indicated ORR 79% for the NTRK inhibitor larotrectinib, with 16% CR


April 14, 2020


A pooled analysis of 3 clinical trials (n=50 total subjects) indicated ORR 79% for the NTRK inhibitor larotrectinib, with 16% CR. The drug was well-tolerated. These alterations are enriched in rare histologies and in cancers lacking other driver mutations with low tumour mutational burden. An exception is colorectal cancer where NTRK fusions are correlated with MSI+ disease (as are RET fusions).

Larotrectinib in patients with TRK fusion-positive solid tumours: a pooled analysis of three phase 1/2 clinical trials

Prof David S Hong, et al

The Lancet Oncology VOLUME 21, ISSUE 4, P531-540, APRIL 01, 2020



The selective TRK inhibitor larotrectinib was approved for paediatric and adult patients with advanced TRK fusion-positive solid tumours based on a primary analysis set of 55 patients. The aim of our analysis was to explore the efficacy and long-term safety of larotrectinib in a larger population of patients with TRK fusion-positive solid tumours.


Patients were enrolled and treated in a phase 1 adult, a phase 1/2 paediatric, or a phase 2 adolescent and adult trial. Some eligibility criteria differed between these studies. For this pooled analysis, eligible patients were aged 1 month or older, with a locally advanced or metastatic non-CNS primary, TRK fusion-positive solid tumour, who had received standard therapy previously if available. This analysis set includes the 55 patients on which approval of larotrectinib was based. Larotrectinib was administered orally (capsule or liquid formulation), on a continuous 28-day schedule, to adults mostly at a dose of 100 mg twice daily, and to paediatric patients mostly at a dose of 100 mg/m 2 (maximum of 100 mg) twice daily. The primary endpoint was objective response as assessed by local investigators in an intention-to-treat analysis. Contributing trials are registered with ClinicalTrials.gov, NCT02122913 (active not recruiting), NCT02637687 (recruiting), and NCT02576431 (recruiting).


Between May 1, 2014, and Feb 19, 2019, 159 patients with TRK fusion-positive cancer were enrolled and treated with larotrectinib. Ages ranged from less than 1 month to 84 years. The proportion of patients with an objective response according to investigator assessment was 121 (79%, 95% CI 72–85) of 153 evaluable patients, with 24 (16%) having complete responses. In a safety population of 260 patients treated regardless of TRK fusion status, the most common grade 3 or 4 larotrectinib-related adverse events were increased alanine aminotransferase (eight [3%] of 260 patients), anaemia (six, 2%), and decreased neutrophil count (five [2%]). The most common larotrectinib-related serious adverse events were increased alanine aminotransferase (two [<1%] of 260 patients), increased aspartate aminotransferase (two [<1%]), and nausea (two [<1%]). No treatment-related deaths occurred.


These data confirm that TRK fusions define a unique molecular subgroup of advanced solid tumours for which larotrectinib is highly active. Safety data indicate that long-term administration of larotrectinib is feasible.

TRK Fusions Are Enriched in Cancers with Uncommon Histologies and the Absence of Canonical Driver Mutations

Ezra Y. Rosen et al

Clinical Cancer Research DOI: 10.1158/1078-0432.CCR-19-3165 Published April 2020



TRK inhibitors achieve marked tumor-agnostic efficacy in TRK fusion–positive cancers and consequently are now an established standard of care. Little is known, however, about the demographics, outcomes, response to alternative standard therapies, or genomic characteristics of TRK fusion–positive cancers.

Experimental Design:

Utilizing a center-wide screening program involving more than 26,000 prospectively sequenced patients, genomic and clinical data from all cases with TRK fusions were extracted. An integrated analysis was performed of genomic, therapeutic, and phenomic outcomes.


We identified 76 cases with confirmed TRK fusions (0.28% overall prevalence) involving 48 unique rearrangements and 17 cancer types. The presence of a TRK fusion was associated with depletion of concurrent oncogenic drivers (P < 0.001) and lower tumor mutation burden (P < 0.001), with the exception of colorectal cancer where TRK fusions cooccur with microsatellite instability (MSI-H). Longitudinal profiling in a subset of patients indicated that TRK fusions were present in all sampled timepoints in 82% (14/17) of cases. Progression-free survival on first-line therapy, excluding TRK inhibitors, administered for advanced disease was 9.6 months [95% confidence interval (CI), 4.8–13.2]. The best overall response rate achieved with chemotherapy containing–regimens across all lines of therapy was 63% (95% CI, 41–81). Among 12 patients treated with checkpoint inhibitors, a patient with MSI-H colorectal cancer had the only observed response.


TRK fusion–positive cancers can respond to alternative standards of care, although efficacy of immunotherapy in the absence of other predictive biomarkers (MSI-H) appears limited. TRK fusions are present in tumors with simple genomes lacking in concurrent drivers that may partially explain the tumor-agnostic efficacy of TRK inhibitors.