Enanta Pharmaceuticals said today it agreed to regain full rights from Novartis to EDP-239, an NS5A inhibitor now in Phase I development for hepatitis C virus (HCV).

The action ends a 2–1/2 year collaboration between the companies following a licensing deal that once promised up to $440 million to Enanta from Novartis.

In February 2012, Novartis won an exclusive worldwide license from Enanta to develop, manufacture, and commercialize EDP-239 and other NS5A compounds. Novartis agreed to fund all costs associated with the development, manufacture, and commercialization of EDP-239, EDP-239-containing combinations and any follow-on NS5A inhibitors, as well as funding Enanta’s efforts to discover follow-on NS5A inhibitors at least through August 2013.

EDP-239 is Enanta’s internally-developed lead NS5A inhibitor for HCV infection, having shown positive results reducing replication of major HCV genotypes when tested via replicon assay.

According to Enanta, EDP-239 has also shown additive or synergistic antiviral activity when used in combination with other anti-HCV therapeutics (direct-acting antiviral and host-targeted antiviral) in reducing HCV replication.

The reversion of EDP-239 rights followed Novartis notifying Enanta that the pharma giant no longer considered HCV research within its areas of strategic focus, Jay R. Luly, Ph.D., Enanta’s president and CEO, said in a statement.

As a result, Enanta will take over two proof-of-concept studies now in progress—one involving EDP-239, and one that is assessing the combination of EDP-239 and Alisporivir, a cyclophilin inhibitor licensed by Novartis from Debiopharm. The latter study was set back by a clinical hold after several cases of pancreatitis were reported among patients, one of which died.

Over the past year, Novartis has restructured its R&D operations worldwide, in some cases shutting sites and in others, concentrating its employees in fewer but larger research hubs.

“We appreciate Novartis’ contributions to the clinical development of EDP-239 and its ready agreement to return the NS5A program to us. Enanta is now positioned with three wholly-owned HCV programs from which future drug combinations can be explored,” Dr. Luly stated.

These programs are based on inhibitors discovered, and in some cases developed by Enanta, against HCV. The inhibitors include NS5A and two other members of the direct-acting antiviral (DAA) inhibitor classes—protease and nucleotide polymerase—as well as a host-targeted antiviral inhibitor class targeted against cyclophilin.

Enanta has partnered with AbbVie and predecessor Abbott Laboratories since December 2006 to develop and commercialize HCV NS3 and NS3/4A protease inhibitors and HCV protease inhibitor-containing drug combinations.

Back then, Enanta won $57 million upfront and the potential for up to $250 million in clinical and regulatory milestone payments from Abbott and AbbVie, in return for gaining worldwide access to the biotech’s drug discovery capabilities for HCV NS3 and NS3/4A protease inhibitors. AbbVie funds all costs associated with the development, manufacture and commercialization activities of ABT-450 and other compounds under this agreement.

For any HCV protease inhibitor developed through the partnership, Enanta stands to gain from AbbVie double-digit royalties. Enanta holds an option to fund 40 percent of development costs and U.S. commercialization efforts (sales and promotion costs) in exchange for a 40% profit share in the U.S. on medicines developed with AbbVie that gain commercial approval.

The cyclophilin inhibitor and nucleotide polymerase inhibitor programs are both in preclinical development, Enanta said.

Enanta has also created a new class of antibiotics called Bicyclolides to treat multi-drug resistant bacteria, with a focus on developing an intravenous and oral treatment for hospital and community MRSA (methicillin-resistant Staphylococcus aureus) infections.

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