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FDA Approves Biomarker-Targeting Cancer Drug

DNA methylation illustration

(Christoph Bock, Wikimedia Commons)

27 Nov. 2018. The Food and Drug Administration yesterday approved a treatment for solid tumor cancers that focuses on specific cancer-causing genetic conditions rather than location of the cancer in the body. FDA approved the drug larotrectinib, developed and marketed as Vitrakvi by Loxo Oncology in Stamford, Connecticut, under its accelerated and orphan drug review processes. Loxo Oncology is developing Vitrakvi with drug maker Bayer.

Vitrakvi is an early example of so-called precision medicine drugs that address specific cancer-causing biomarkers, or molecular indicators of disease. In this case, the biomarker is neurotrophic receptor tyrosine kinase, or NTRK, a gene-fusion condition where chromosomes break apart and mismatched genes fuse back together. This fusion results in generation of cancer-causing TRK proteins that encourage solid tumor onset, growth, and development, in various parts of the body.

FDA approved Vitrakvi for treating solid-tumor cancers in adults and children expressing NTRK fusion, with no counterpart resistance mutation, where the cancer is spreading in the body, surgical removal of the cancer is not feasible, and the cancer does not respond to other treatments. Among these conditions are rare types of cancer which previously had no approved treatments, including mammary analogue secretory carcinoma, cellular or mixed congenital mesoblastic nephroma, and infantile fibrosarcoma.

The agency approved Vitrakvi based in part on results from 3 clinical trials testing the drug among 55 adults and children, diagnosed with 17 different types of cancer, but all expressing the same NTRK fusion condition. The results show a 75 percent response rate, including 22 percent with a complete response. In addition, more than 7 in 10 (73%) continued their responses for at least 6 months, and 4 in 10 (39%) continuing for a year or longer. Science & Enterprise reported on early results of the trials in February of this year.

Vitrakvi is taken as a capsule or oral solution. Common adverse effects include fatigue, nausea, cough, constipation, diarrhea, dizziness, and vomiting, as well as increased levels of AST and ALT liver enzymes in the blood stream, indicators of liver inflammation or injury. Women who are pregnant or breast feeding are discouraged from taking the drug due to potential harm to the fetus or newborn infant.

FDA approved Vitrakvi under its Priority Review and Breakthrough Therapy designations, which provide accelerated review and increased high-level management attention from FDA for treatments of serious unmet medical conditions. Because some of the cancers treated with Vitrakvi have small numbers of patients, it also qualified as an orphan drug treating rare diseases.

“Today’s approval marks another step in an important shift toward treating cancers based on their tumor genetics rather than their site of origin in the body,” says FDA commission Scott Gottlieb in an agency statement. “This new site-agnostic oncology therapy isn’t specific to a cancer arising in a particular body organ, such as breast or colon cancer. Its approval reflects advances in the use of biomarkers to guide drug development and the more targeted delivery of medicine. We now have the ability to make sure that the right patients get the right treatment at the right time.”

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