Adherex Licenses GSK’s Eniluracil, Estimates Oncologic’s Potential At $1 Bil.

Eniluracil has potential to make the chemotherapy staple 5-fluorouracil more effective, safer and orally active, Adherex maintains. Agent slated to enter new Phase III studies in 2007. Licensing pact valued at up to $220 mil. also gives GSK option on Adherex’ angiolytic agent Exherin.

Adherex gains rights to GlaxoSmithKline's oncology agent eniluracil in exchange for a GSK option on Adherex' lead biotechnology oncologic ADH-1 under a combined licensing agreement, announced July 15.

The deal is potentially worth up to $220 mil. to Adherex, plus royalties.

The firm's exclusive in-licensing of eniluracil includes development and sales milestones of up to $120 mil. plus double-digit royalties - if GSK exercises rights to buy back the chemotherapeutic compound at various stages of development.

If GSK exercises its option for an exclusive, worldwide license to Adherex' N-cadherin antagonist compound Exherin (ADH-1), Adherex would receive up to $100 mil. in upfront, development and sales milestones, plus double-digit royalties.

Exherin is in Phase Ib/II and Phase II trials after an initial Phase I study demonstrated "encouraging evidence of anti-tumor activity," Adherex said.

During a same-day conference call, Adherex highlighted eniluracil's potential to enhance the therapeutic and safety profile of the established chemotherapy agent 5-fluorouracil (5-FU).

Adherex estimates eniluracil's market potential at over $1 bil.

"The drug showed substantial promise and very good activity in Phase I and Phase II trials," Adherex CEO William Peters stated. However, "two Phase III trials failed and GSK stopped development," he added.

Peters explained the reasoning behind the eniluracil acquisition, given the agent's history of failed Phase III trials. The exec maintained that recently acquired data provides "both an explanation of why the prior trials had failed and presents a clear and accelerated clinical development strategy."

Adherex expects eniluracil to enter new Phase III trials in 2007.

Expanding on eniluracil's potential with 5-FU, Peters noted that "while 5-FU is a mainstay of contemporary oncology, it has some significant therapeutic limitations which eniluracil may improve."

5-FU "has variable pharmacology from patient to patient, and the use of eniluracil may significantly improve the consistency of the metabolism of 5-FU and could make it more predictable, uniform, safe and effective," Peters explained.

"The breakdown products of 5-FU can cause severe and often dose-limiting side effects such as hand-foot syndrome, which may be minimized or eliminated by the use of eniluracil."

Adherex also believes eniluracil could make 5-FU an orally active drug, and "substantially improve its half-life." 5-FU is currently given intravenously due to its short half-life.

If GSK does not exercise its eniluracil buy-back options, Adherex would be able to develop the agent on its own or with partners in exchange for milestone payments and double-digit royalties paid to GSK.

- Lee Szilagyi