Pfizer Inc said it made an exclusive worldwide collaboration with Adolor Corporation to develop and commercialise novel compounds, ADL5859 and ADL5747, for the treatment of pain and inflammation.

Both compounds are proprietary Delta opioid receptor agonist candidates with the potential to treat a wide range of inflammatory, neuropathic and acute pain conditions.

Pfizer will pay its partner a $30 million upfront, plus $1.9 million reimbursement for prior phase II development costs. If certain regulatory milestones and development are met, Adolor will receive payments up to $232.5 million. More than 50 per cent of these milestones may be earned prior to regulatory approval of the compounds, with the first milestone payment available to be earned on commencement of phase IIb clinical studies.

The companies will form a Joint Steering Committee to guide the development and commercialisation of products resulting from the collaboration. Pfizer will be responsible for securing regulatory approvals and commercialisation on a worldwide basis.

The terms of the agreement provide for Pfizer and Adolor to share revenues and expenses 60/40 per cent in the United States. Outside the US, Pfizer will fund development activities and, on commercialisation, Adolor will receive royalties on Pfizer net sales.

"We are pleased to be partnering with Pfizer in this very exciting program," said Michael R. Dougherty, president and chief executive officer, Adolor Corporation. "Our vision for the Delta agonists has been to develop a new class of opioids, delivering analgesia without some of the complicating side effects of traditional mu agonists. Pfizer brings extensive pain management development and commercial expertise to this collaboration and we look forward to working with Pfizer in the pursuit of this vision."

ADL5859 is in a phase II development program exploring its analgesic efficacy in inflammatory pain associated with rheumatoid arthritis and acute post-dental surgery pain. Additional programs are planned to evaluate ADL5859 in patients with diabetic peripheral neuropathy and osteoarthritis. All future development work is subject to a Joint Development Committee. Adolor expects to begin phase I clinical testing of ADL5747 in the first quarter of 2008.

"This collaboration demonstrates our commitment to executing against the R&D plan we outlined, including expanding our phase II portfolio with a strong focus in our key therapeutic areas," said Dr. Martin Mackay, president, Global Research and Development, Pfizer. "Pfizer has a strong history in bringing to market novel pain solutions including Lyrica, Neurontin and Celebrex. However, there still remains a significant unmet medical need for patients suffering from a variety of debilitating pain conditions."

One of three opioid receptors, the Delta receptor has potential utility in a variety of indications, including the modulation of pain. Through a proprietary research platform based on cloned, human opioid receptors, Adolor has identified a series of novel, orally active Delta agonists - compounds that selectively stimulate the Delta opioid receptor. Delta compounds may have a number of potential advantages, including an improved side effect profile, as compared to mu opioid receptor agonists. On the basis of preclinical evaluation in animal models of human conditions, a Delta agonist may show effect in inflammatory pain, among other pain conditions. In addition, Delta agonists are thought to modulate other biological processes that may manifest themselves in disease states or conditions such as cardio-protection, overactive bladder, and depression. There are currently no selective Delta agonists approved by the FDA.