GlaxoSmithKline and Adolor Corporation presented at the American pain society meeting in San Antonio, Texas, positive results from a phase 2b clinical study of alvimopan (Entereg), an orally administered investigational drug that blocks peripheral mu-opioid receptors. In this large study, evaluating alvimopan for the treatment of opioid-induced gastrointestinal side effects, patients reported a significant improvement in common and bothersome gastrointestinal (GI) symptoms associated with opioid use, including constipation, abdominal pain and bloating.

Alvimopan is an investigational peripherally acting mu-opioid receptor (PAM-OR) antagonist designed to inhibit the negative effects of opioids, like morphine or codeine, on the gastrointestinal system without interfering with the analgesic effects on the central nervous system. Alvimopan is the first of this new class of compounds with a NDA that has been accepted for review by the US FDA for postoperative ileus (POI).

Millions of people worldwide take opioids chronically to treat moderate to severe pain and about half of them will suffer from associated constipation, abdominal pain, discomfort and bloating. Constipation can lead to serious complications and in some cases can be life threatening. Often patients cannot receive enough opioid to manage their pain due to constipation. The findings from this study suggest that alvimopan may play an important role in treating these GI side effects in patients by blocking the effects opioids have on the gut without adversely impacting the effect on pain control," said Dr Lynn Webster, Lifetree Clinical Research and Pain Clinic, Salt Lake City, Utah, USA.

Opioids, such as morphine, are highly effective in the treatment of pain and are widely used to treat moderate to severe pain such as pain associated with or as a result of back pain, arthritis and other pain conditions. However, the use of opioids is associated with persistent GI side effects such as constipation, characterised by infrequent, difficult or incomplete bowel movements, abdominal pain and discomfort, and bloating. Other GI side effects related to opioids include acid reflux and loss of appetite.

Adolor Corporation and GlaxoSmithKline are collaborating on the worldwide development and commercialization of alvimopan for POI and gastrointestinal side effects associated with the use of opioids to treat persistent pain. As previously announced, GSK is conducting studies investigating efficacy and safety in non-cancer and cancer patients taking opioids for treatment of persistent pain.