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Melanoma, BRAF V600E and V600K Mutation Analysis, THxID®

Test code(s) 92131

Question 1. What is a companion diagnostic assay?

A companion diagnostic assay is an in vitro diagnostic (IVD) assay that provides information essential for the safe and effective use of a corresponding therapeutic drug.

The use of an IVD companion diagnostic assay with a particular therapeutic drug is stipulated in the instructions for use in the FDA labeling (package insert) of both the diagnostic assay and corresponding therapeutic drug.

A list of FDA cleared or approved companion diagnostic assays can be viewed on the following link:

FDA cleared or approved companion diagnostic devices

Question 2. Is the bioMerieux THxID assay a companion diagnostic assay for all malignant melanoma therapies?

No. The FDA has approved two companion diagnostic assays to aid in treatment selection for a patient with malignant melanoma. These assays are designed to detect a specific BRAF mutation in formalin-fixed, paraffin embedded (FFPE) specimens.

  1. The bioMerieux THxID®-BRAF kit, which detects the codon 600 mutations V600E and V600K, serves as a companion diagnostic assay for Tafinlar® (dabrafenib) and/or Mekinist® (trametinib).
  2. The Roche Cobas®4800 BRAF V600 mutation test, which detects the V600E mutation and 50% of V600K mutations, is a companion diagnostic assay for Zelboraf® (vemurafenib).

Question 3. Which BRAF mutations does the bioMerieux THxID assay detect?

The bioMerieux THxID-BRAF is an IVD assay intended for the qualitative detection of BRAF V600E and V600K mutations in a DNA sample extracted from FFPE human melanoma tissue. It is a real-time PCR test performed on the ABI 7500 Fast Dx system and is labeled as a companion diagnostic device by the US FDA. Samples that are reported as BRAF mutation negative may harbor BRAF mutations not detected by the assay (for example V600R or V600D). Patients with V600R and V600D BRAF mutations have not been shown to be responsive to trametinib and or dabrafenib.

Approximately 50% of melanomas harbor activating BRAF mutations. Among the BRAF mutations observed in melanoma, over 90% are at codon 600, and, among these, over 90% are single nucleotide mutations resulting in substitution of glutamic acid for valine (BRAF V600E: nucleotide 1799 T>A; codon GTG>GAG). The second most common mutation is BRAF V600K (GTG>AAG), which substitutes lysine for valine; it accounts for 5% to 6% of melanoma BRAF mutations. Mutations occurring at lesser frequency include BRAF V600R (GTG>AGG), an infrequent two-nucleotide variation of the predominant mutation; BRAF V600 ′E2′ (GTG>GAA); and BRAF V600D (GTG>GAT).

Question 4. Which therapies are linked to the bioMerieux THxID assay?

The THxID-BRAF assay is intended to be used as an aid in selecting melanoma patients for treatment with Tafinlar®(dabrafenib). Patients eligible for treatment with dabrafenib test positive for the BRAF V600E mutation. The assay can also aid in the selection of melanoma patients for treatment with Mekinist® (trametinib).

Dabrafenib is a selective inhibitor of BRAF kinase activity, and trametinib is a selective inhibitor of MEK activity.

Question 5. Can any BRAF mutation assay serve as a companion diagnostic assay for targeted melanoma therapies?

No, only FDA cleared or approved assays can serve as companion diagnostic assays. Although non-FDA approved technologies, kits, or laboratory assays may identify the BRAF mutations of interest, they may not be used as a substitute for an FDA approved/cleared companion diagnostics assay for purposes of treatment selection.

Question 6. How can I differentiate an FDA cleared/approved BRAF assay from a non-FDA cleared/approved BRAF assay?

The FDA provides a list of approved or cleared companion diagnostics assays and their associated therapeutic agents.This list is available at: http://www.fda.gov/medicaldevices/productsandmedicalprocedures/invitrodiagnostics/ucm301431.htm .

Additionally, federal law requires laboratories to identify any non-FDA cleared or approved assays on the medical report.

Question 7. How is the Roche BRAF companion diagnostic assay different from the bioMerieux assay?

The Roche Cobas®4800 BRAF V600 companion diagnostic assay uses a different testing platform. It tests for BRAF V600 mutations but does not differentiate V600E from V600K. Results are reported as “mutation not detected” or “mutation detected.”

The bioMerieux THxID assay, on the other hand, tests for and distinguishes V600E and V600K mutations. The results are reported as “BRAF mutation negative,” “V600E mutation,” “V600K mutation,” or “V600E and V600K mutations.”

As indicated above, each of these tests is FDA approved only for a specific therapeutic agent(s).

Question 8. What other BRAF mutation assays do you offer?

16767: BRAF Mutation Analysis: Sanger sequencing method

90868: BRAF Mutation Analysis: allele-specific real-time PCR

90956: Melanoma, BRAF V600 Mutation, Cobas®: the Roche Cobas 4800 BRAF V600 test

91919: OncoVantage®: next generation sequencing panel for solid tumors

This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.

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