Durect, Impax tie up for a shingles patch to last 6 times as long as Lidoderm

Impax Laboratories ($IPXL) is tapping Durect ($DRRX) for its mid-stage transdermal patch Eladur, which is designed to ease the pain associated with shingles. For exclusive rights to the delivery tech, Impax agreed to pay up to $63 million to Durect when all is said and done.

Eladur delivers the pain drug bupivacaine into the skin continuously for up to three days at a time, which is an improvement over the 12-hour wearing time of existing lidocaine patches, such as Lidoderm from Endo Pharmaceuticals ($ENDP).

The two California-based companies signed the agreement this week for $2 million paid up front to Durect as well as another $61 million in milestone payments for both the development and commercialization of the patch. Durect can also expect a royalty on sales, according to a release.

"Existing patches can be worn for 12 hours and then need to let the skin recover for 12 hours," Durect CFO Matthew Hogan told FierceDrugDelivery. "But some publications have shown that patients have pain start to come back during that time. Our patch is designed to wear for three days, and the hope is to reduce episodes of breakthrough pain during these rest periods."

In 2013, both companies suffered setbacks. For Impax, manufacturing issues scuttled a partnership with GlaxoSmithKline ($GSK). For Durect, major delays hit its lead painkiller candidate, Remoxy, under development in partnership with Pfizer ($PFE) and Pain Therapeutics ($PTIE).

Durect and Eladur have also walked a rocky road to get to this Impax partnership. In 2007, the company touted a successful Phase IIa trial of the patch in 60 patients, which led to a partnership with Alpharma Pharmaceuticals, later acquired by King Pharmaceuticals. King tried to develop the patch for chronic back pain, an indication that, in Phase II, failed to outdo the placebo.

Eladur is and always was a topical analgesic, not intended for deep delivery to muscles, Hogan said. "Eladur wasn't designed for back pain," he said. "It works near the surface of the skin, and if you have back pain, there's not as much of an impact."

When Pfizer acquired King in 2010, it sold the rights back to Durect. So it was back to the drawing board partnership-wise for the drug delivery company. With the Impax deal, Eladur is offered another lease on life, bringing it back to its original indication: skin-deep delivery for post-herpetic neuralgia, or shingles pain.

"What Impax has said is they plan to do a proof-of-concept study," Hogan said. "Then they propose to talk to the FDA for a Phase III program. Then I think they would like to start Phase III by the end of the year."

And Impax, despite the manufacturing snafu that brought a regulatory hammer down mid-year, gives Durect what it needs.

"At Impax, the products are all on neurology, and pain is a subset of that," Hogan said. "They have a specialty sales and development force, and it fits nicely."

Besides Eladur, Durect also has two late-stage treatments in tow. The first is Posidur, also delivering bupivacaine, which is intended as a local anesthetic for post-surgical pain. Posidur has a PDUFA date of Feb. 12. And Remoxy, a Pfizer-controlled tamper-resistant oxycodone gelatin capsule, is awaiting a complete response from the FDA by mid-2015. It has been plagued by delays in the drug approval process.

- here's the release