The US Food and Drug Administration (FDA) has approved the first cancer drug to inhibit a protein — called MEK — that acts in a pathway that fuels tumour growth. The drug, called Mekinist (trametinib), was approved on 29 May for use in advanced melanomas with specific mutations. Other MEK-targeting drugs are being studied in a wide range of tumours, including lung and thyroid cancers.

The FDA approved Mekinist together with another drug, called Tafinlar (dabrafenib), which targets cancer-driving mutant forms of a protein called BRAF. The agency also approved a medical test for those BRAF mutations. BRAF inhibitors, one of which is already on the market, elicit rapid and dramatic responses, in some cases wiping away nearly all signs of the disease. But the responses are short-lived, and the drugs boost survival by only a few months.

Hopes are high that Mekinist and Tafinlar, both made by GlaxoSmithKline, will eventually be approved for use in combination — and that the combination will lengthen patient survival more than either drug would individually. GlaxoSmithKline says that it will file for FDA approval of that combination in the coming months. Meanwhile, Mekinist will cost US$8,700 per month, and Tafinlar $7,600 per month, wholesale, putting both drugs just shy of the growing ‘$10,000-a-month club’ for cancer drugs.