Sales of drugs to treat irritable bowel syndrome (IBS) in seven major markets are set to soar from a value of $610 million in 2010 to $2.7 billion by 2020, according to new forecasts.

The market entry of a few high-priced but much-needed first-in-class therapies will drive the fast growth in these markets - the US, France, Germany, Italy, Spain, the UK and Japan - says the study, from Decision Resources. It also points out that some of these new treatments affect not only motility but also pain, which remains one of the biggest unmet needs for IBS patients and the physicians who treat them.

The study forecasts that by 2020 the market leader in the treatment of IBS will be linaclotide, an investigational guanylate cyclase-C receptor agonist being developed by Ironwood Pharmaceuticals, Forest Laboratories, Almirall and Astellas Pharma.

"Owing to its superb efficacy, safety profile and anticipated launch in all major markets, linaclotide will achieve blockbuster sales by 2018," thus cementing its status as leader for the treatment of IBS by 2010, says the report. It adds that, in contrast, sales of Sucampo/Takeda/Abbott Laboratories' Amitiza (lubiprostone), the market leader in 2010, will suffer a sharp decline over the next decade as a result of its limited efficacy, loss of patent protection and competition from linaclotide.

"All emerging therapies are expected to launch in the US, where sales of IBS therapies will increase the most rapidly and account for a large majority of the market in 2020," comments Madhuri Borde, therapeutic area director at Decision Resources.

The research firm also reports that throughout leaders interviewed for the study have differing opinions on the utility of antibiotics in treating IBS. Last year, the US Food and Drug Administration (FDA) issued a complete response letter to Salix for its supplemental New Drug Application (sNDA) for Xifaxan (rifaximin), requesting data on re-treatment with the drug.

This development illustrates that, in addition to thought leaders, regulatory authorities also have reservations about the use of antibiotics in treating IBS, says Decision Resources.

- In October, Ironwood and Forest reported that the US FDA had accepted for review their NDA for linaclotide in the treatment of IBS with constipation (IBS-C) and chronic constipation (CC), with an anticipated action date of June 2012. The previous month, Almirall filed for the drug's approval, under the brand name Constella, in Europe, for the treatment of IBS-C.