UPDATED: GlaxoSmithKline gains FDA OK on two genetically targeted melanoma drugs

Melanoma under a microscope--Courtesy of NIH

By John Carroll and Ryan McBride

In an important win for GlaxoSmithKline's R&D division, the FDA today announced that it has approved a pair of genetically targeted melanoma drugs--dabrafenib and trametinib--from the company, along with a diagnostic test that can be used to identify patients most likely to respond to the treatments.

Dabrafenib and trametinib will now go on to be sold as Tafinlar and Mekinist for advanced cases of melanoma. Tafinlar is a BRAF inhibitor designed to attack tumors that express the BRAF V600E gene mutation. Mekinist is a MEK inhibitor targeting tumors that express the BRAF V600E or V600K gene mutations. About half of all melanoma patients have a BRAF mutation. The genetic test approved today is called the THxID BRAF test, a companion diagnostic that will be used to determine if a patient's melanoma cells have the V600E or V600K mutation in the BRAF gene.

In the United States, the wholesale acquisition cost of Tafinlar is $7,600 for a 30-day supply and Mekinist will be $8,700 for a 30-day supply, according to a spokesperson for GlaxoSmithKline. 

GlaxoSmithKline ($GSK) had 5 drugs under regulatory review at the beginning of this year, including these two, giving the pharma giant some much-needed bragging rights for advancing new drugs after a turnaround was mounted in the R&D group more than three years ago. And its melanoma drugs, which follow the approval of Yervoy and Zelboraf in 2011, fit neatly into the FDA's comfort zone for genetically targeted therapies, particularly for melanoma.

"Advancements in our understanding of the biological pathways of a disease have allowed for the development of Tafinlar and Mekinist, the third and fourth drugs the FDA has approved for treating metastatic melanoma in the past two years," said Dr. Richard Pazdur, director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research (CDER).

These drugs were approved as single products, but the London-based drug giant has high hopes for ongoing studies that test how a combo approach could delay recurrence of cancer in high-risk patients. The trials come as GSK races with Roche/Genentech to advance combination therapies against melanoma, as FierceBiotech's Ryan McBride reported recently. Genentech, the U.S. biotech unit of Roche ($RHHBY), is doing late-stage testing of a rival dual therapy consisting of the experimental MEK inhibitor GDC-0973 from its partner Exelixis ($EXEL) and its approved BRAF inhibitor Zelboraf.

During the American Society for Clinical Oncology (ASCO) meeting in Chicago last year, GSK provided data from the two late-stage studies that compared each of its experimental treatments alone to standard chemotherapy in metastatic melanoma patients with BRAF mutations. In the BREAK3 study, patients on GSK's BRAF-blocking drug dabrafenib lived for 5.1 months without their cancer advancing compared with 2.7 months of PFS for patients on chemotherapy. And the METRIC study showed that patients on GSK's MEK inhibitor trametinib went 4.8 months without their cancer worsening, more than three times longer than patients who got chemo.

Some analysts have pegged potential peak sales for these drugs at about $350 million each. The National Cancer Institute says that about 76,690 Americans will be diagnosed with melanoma this year, with roughly 9,480 dying from the disease.

- here's the press release from the FDA
- read FierceMedicalDevices' story on the companion diagnostic