Endo ($ENDP) and BioDelivery Sciences International ($BDSI) announced FDA approval of Belbuca, the first and only polymer strip for the delivery of the painkiller buprenorphine from the inside of the cheek. After Belbuca failed a Phase III trial in 2011, Endo provided product inventor BDSI with $30 million to earn approval in exchange for global rights to the drug. Its novel delivery method should help it stand out in the crowded market for painkillers, which mainly come in oral formulations. But a second-line label and a black box warning due describing its abuse potential and the risk of fatal respiratory failure will limit its appeal. Nomura analyst Shibani Malhotra said Belbuca has the potential for peak sales of $500 million per year. Regardless, BDSI has earned a $50 million milestone payment from Endo. More from FierceBiotech