Merck & Co hit a milestone late last week when it won approval in the USA for Zolinza, a new drug to treat cutaneous T cell lymphoma – the first new cancer drug to come out of the US drugmaker’s pipeline in two decades.

CTCL, an aggressive form of non-Hodgkin’s lymphoma that affects the skin, is rare and occurs in just three out of every million people in the USA, or around 20,000 cases in total. First-line treatment of the disease is typically with topical treatments such as ultraviolet or photodynamic therapy, and Zolinza is reserved for use when the disease persists, gets worse, or comes back during or after treatment with other medicines.

Although CTCL is a small indication for Zolinza (vorinostat), Merck is also developing the drug for other cancers, including breast cancer and lung cancer. Zolinza is the first of a new range of anticancer therapies that target the mechanism of histone deacetylation, thought to be involved in silencing genes linked to cell cycle progression and apoptosis.

Zolinza is orally-active and is approved as a once-daily dose, with a wholesale price of $240 a day, or $87,600 a year.

A response, defined by improvements on a scale that scores skin lesions, occurred in 30% of patients who received Zolinza and lasted an average of 168 days. The most common serious adverse events were pulmonary embolism, dehydration, deep vein thrombosis, and anaemia.

Other companies developing histone deacetylase inhibitors for cancer applications include: TopoTarget/Curagen, whose PXD101 is in Phase II testing for various harmatological malignancies and Phase I for solid tumours; and Pharmion/Methylgene with MGCD0103 (Phase I).