The FDA’s newly approved drug, larotrectinib (known by the brand name Vitrakvi), is the first genetics-based cancer drug that doesn’t treat just one specific form of cancer. That’s because this new drug focuses on TRK fusion genes, which occur in many different types of cancer, making it a potentially effective mesothelioma treatment.

How Larotrectinib Works

Larotrectinib, a form of targeted therapy, works as an inhibitor for TRK fusion genes.

Usually, TRK genes encourage the body’s cells to grow and heal. However, sometimes there can be a genetic error, and part of one TRK gene can merge with a different gene. This is called a TRK fusion gene. These fused genes can send out almost continuous signals encouraging the cells around them to grow and multiply contributing to the growth of solid tumors.

Some of the different types of cancers that TRK fusion genes can happen in are mesothelioma, infantile fibrosarcoma, breast cancer and lung cancer. While the mutation occurs in more than one type of mesothelioma, the majority of the patients who tested positive for TRK fusion cancer had biphasic mesothelioma (mixed cell type).

Larotrectinib stops TRK fusion genes from sending out those messages regardless of the type of cancer or the age of the patient in 75% of the cases. In fact, in two cases of infantile fibrosarcoma, the tumors shrank enough that the children were able to undergo curative limb-saving surgery.

“It is exciting to see larotrectinib deliver durable responses to patients in these studies with TRK fusion cancer, regardless of age, tumor site of origin, or CNS involvement,” said Ulrik Lassen, M.D., Ph.D., Department of Oncology, Rigshospitalet, Copenhagen. “The 67 new patients have nearly the same overall response rate as the first 55, and duration of response has actually improved with longer patient follow-up.”

Targeted Mesothelioma Treatment Explained

Targeted therapies are drugs that focus in on specific genes or proteins in the body. Some of these genes are associated with only one type of cancer, while others, like the TRK fusion gene, are associated with many different types of cancers.

Unlike chemotherapy, targeted therapy doesn’t try to kill the cancer cells. Usually, targeted therapies interact with proteins or molecules to prevent growth signals from being sent. These therapies are also different from chemotherapy because they only interact with specific targets.

In other words, larotrectinib will only communicate with TRK fusion genes—not other types of genes as well. The drugs used in chemotherapy are not that specific, which is why they attack any fast-growing cells like those in hair and nails, instead of just the fast-growing cancer cells.

Targeted therapies do have limitations because cancer cells can become resistant to treatment. In fact, scientists studying larotrectinib have already encountered this problem and created a workaround to allow their drug to continue to be successful. But that doesn’t mean their battle is over. There will be a constant back and forth scuffle between the researchers and the cells as both continue to learn and evolve.

Larotrectinib for Patients With Mesothelioma

Mesothelioma is one of the cancers that can have a TRK fusion gene, which means that this new drug can be used as a mesothelioma treatment.

However, before patients can start taking larotrectinib, they need to know whether or not they have TRK fusion cancer. Tests for TRK fusion genes are expensive. There are only a few types of gene testing methods that are specific and sensitive enough to detect TRK fusion genes.

TRK fusion gene testing options include next-generation sequencing (NGS), fluorescence in situ hybridization (FISH), and immunohistochemistry (IHC).

For patients who are eligible for larotrectinib, the side effects associated with larotrectinib are generally relatively mild. Some of the common ones are fatigue, vomiting or nausea, and dizziness. Talk to your doctor today about new mesothelioma treatment options like larotrectinib.

 

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Sources
  1. "Efficacy of Larotrectinib in TRK Fusion–Positive Cancers in Adults and Children" The New England Journal of Medicine. Retrieved from: https://www.nejm.org/doi/full/10.1056/NEJMoa1714448. Accessed December 19, 2018.
  2. "Loxo Oncology Announces Larotrectinib Clinical Update in Patients with TRK Fusion Cancers at the European Society for Medical Oncology 2018 Congress" LOXO Oncology. Retrieved from: https://ir.loxooncology.com/press-releases/2372560-Loxo-oncology-announces-larotrectinib-clinical-update-in-patients-with-trk-fusion-cancers-at-the-european-society-for-medical-oncology-2018-congress. Accessed December 19, 2018.
  3. "NTRK and ALK rearrangements in mesothelioma and lung carcinoid" Journal of Clinical Oncology. Retrieved from: http://ascopubs.org/doi/abs/10.1200/JCO.2018.36.15_suppl.e20558. Accessed December 19, 2018.
  4. "Targeted Cancer Therapies" National Cancer Institute. Retrieved from: https://www.cancer.gov/about-cancer/treatment/types/targeted-therapies/targeted-therapies-fact-sheet#q1. Accessed December 21, 2018.

Last modified: December 29, 2018