AstraZeneca says it has begun enrolment of a late-stage trial for an investigational opioid-induced constipation treatment licensed from Nektar Therapeutics.

The drug in question is NKTR-118, a once-daily tablet that combines Nektar's small molecule polymer conjugate technology platform with naloxol, a derivative of the opioid antagonist naloxone. It is being studied for OIC, a common side effect of prescription opioids used for chronic pain management.

The Anglo-Swedish drugmaker noted that for those patients who take opiates for long-term pain management, 40%-50% will develop constipation. Only half of those experience effective relief from laxatives and stool softeners.

The first regulatory filings based on the programme are planned for 2013. AstraZeneca and Nektar teamed up in September 2009 and the deal includes the earlier-stage NKTR-119, which combines NKTR-118 and an opioid analgesic. When the pact was signed, AstraZeneca made a $125 million upfront payment and the deal could be worth $1.5 billion to Nektar.

Generic Vimovo threat

Meantime AstraZeneca and partner Pozen have been informed that India's Dr Reddy's Laboratories has filed an Abbreviated New Drug Application in the USA seeking regulatory approval to market a generic version of the pain drug Vimovo (naproxen/esomeparazole magnesium).

The drug was only approved last April by the US Food and Drug Administration to alleviate the signs and symptoms of osteoarthritis, rheumatoid arthritis and ankylosing spondylitis, as well as decrease the risk of developing gastric ulcers in patients prone to NSAID-associated stomach problems. Pozen and AstraZeneca are reviewing the case and say they intend to defend their patent from any infringement.