BioDelivery Sciences International announced Tuesday that it has extended the patent protection for its experimental treatment for chronic pain, which will result in the company receiving a $15 million milestone payment from partner Endo Pharmaceuticals.

BioDelivery's patent for BEMA Buprenorphine has been extended by seven years to 2027.

In January, BioDelivery announced that it had licensed BEMA to Pennsylvania-based Endo. The deal included a $30 million upfront fee and future payments totaling $150 million if certain milestones are met.

With this latest $15 million payment, BioDelivery has now received $45 million in payments from Endo.