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Amplifications versus Fusions: What’s the Difference?


Amplifications versus Fusions: What’s the Difference?


The NTRK gene provides instructions for producing proteins called neurotrophic tyrosine kinase
receptors (NTRK receptors) that play a vital role in cell growth and development.


NTRK fusions are a distinct type of gene alteration that occurs when all or a portion of the NTRK gene is
linked (or fused) to all or a portion of another gene. The fusion gene then produces an abnormal protein
that initiates or stimulates growth of the cancer.


NTRK amplifications, on the other hand, refer to a type of alteration in the NTRK gene where there is an
increase in the number of copies of the gene in the tumor. It can also mean an increase in the amount of
ribonucleic acid (RNA) that is made from the gene.


Different therapeutic approaches are required for NTRK amplifications and NTRK fusions. Amplifications
are targeted with drugs that inhibit the overactive NTRK receptors, while fusions are targeted with drugs
that specifically block the abnormal fusion proteins.


For people living with cancer that have a NTRK amplification, the TAPUR (Targeted Agent and Profiling
Utilization Registry) Study clinical trial may be a good resource. The TAPUR Study is a phase II,
nonrandomized clinical trial that includes a cohort that targets NTRK 1, 2, and 3 amplifications with the
FDA-approved oral drug, Larotrectinib (VITRAKVI). There are over 250 clinical sites across 28 states in
the United States. For more information on the TAPUR Study, visit the TAPUR website at If you would like to learn more, the study team recently held a virtual live Grand
Rounds which was recorded. The May 2023 TAPUR Grand Rounds recording is available for viewing and
can be found under the “Study Results” page of the TAPUR website.