Companion Diagnostics FoundationOne CDx and VITRAKVI Used to Treat Solid Tumors

In late October, molecular information company Foundation Medicine, Inc. (“Foundation”) shared that its diagnostic tool FoundationOne CDx was approved as a companion diagnostic for VITRAKVI (larotrectinib). While FoundationOne CDx will help diagnose patients with solid tumors caused by NTRK gene fusions, VITRAKVI serves to treat that same patient population.


Currently, VITRAKVI is indicated for the treatment of patients with solid tumors with a neurotrophic receptor tyrosine kinase (NTRK) gene fusion. According to the National Cancer Institute (NCI), fusion genes are:

made by joining parts of two different genes. Fusion genes, and the fusion proteins that come from them, may be made in the laboratory, or made naturally in the body when part of the DNA from one chromosome moves to another chromosome.

Fusion genes and fusion proteins can be linked to cancer. For example, the NTRK gene fusion results in solid tumors, particularly in rare cancers such as infantile fibrosarcoma, or other cancers such as thyroid carcinoma or melanoma. Meanwhile, BCR-ABL gene fusions can be found in patients with leukemia.

VITRAKVI is used for patients with NTRK fusions, metastatic cancers, or rare cancers with little to no other treatments. This therapy was approved following results from the LOXO-TRK-14001, NAVIGATE, and SCOUT clinical trials. Ultimately, it was effective in inhibiting tumor growth.

Now, the FDA approved the FoundationOne CDx as a companion diagnostic tool. Currently, it is the sole tool approved by the FDA for tissue-based comprehensive genomic profiling (CGP). According to Foundation Medicine:

CGP can analyze more than 300 genes across the four main classes of alterations: base substitutions, insertions and deletions, copy number alterations (CNAs), and rearrangements or fusions. This type of molecular testing produces comprehensive patient reports with a broad and deep assessment of possible underlying oncogenic drivers.

FoundationOne CDx is designed to identify NTRK1, NTRK2, and NTRK3 gene fusions in patients with solid tumors. Once it identifies these fusions, the program gives insight into whether a patient might respond to VITRAKVI.

NTRK Fusion+ Cancers

Cancers that are NTRK fusion+ occur when the part of the chromosome which contains the NTRK gene separates from its original chromosome and binds with another. Next, these fusions manufacture tropomyosin receptor kinase (TRK) fusion proteins. When activated, this protein prompts cancerous cell growth. According to Bayer:

TRK fusion cancer is a very unique and rare disease and is defined by this specific gene alteration. The cancer is not related to a certain type of tissue or the age of the patient; it can occur anywhere in the body, in both children and in adults.

Jessica Lynn

Jessica Lynn

Jessica Lynn has an educational background in writing and marketing. She firmly believes in the power of writing in amplifying voices, and looks forward to doing so for the rare disease community.

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