Gilead Sciences, Inc., a biopharmaceutical company that discovers, develops and commercializes innovative therapeutics in areas of unmet medical need, has signed a definitive agreement to acquire New Jersey-based clinical-stage pharmaceutical company, Pharmasset, Inc. for $137 per share in cash.

According to a Gilead Sciences press release, the transaction, which values Pharmasset at approximately $11 billion, was unanimously approved by Pharmasset's board of directors. Gilead plans to finance the transaction with cash on hand, bank debt and senior unsecured notes. The company expects the transaction, when completed, to be dilutive to Gilead's earnings through 2014 and accretive in 2015 and beyond. Further guidance will be provided when the transaction closes, which is expected to be in the first quarter of 2012.

Pharmasset currently has three clinical-stage product candidates for the treatment of chronic hepatitis C virus (HCV) advancing in trials in various populations. The company's lead product candidate, PSI-7977, an unpartnered uracil nucleotide analog, has recently been advanced into two phase 3 studies in genotype 2 and 3 patients. Both studies will utilize 12 weeks of treatment with PSI-7977 in combination with ribavirin. One study will compare this all-oral regimen against 24 weeks of the standard-of-care pegylated interferon/ribavirin in treatment-naïve patients, and the second study will compare the all-oral regimen to placebo in interferon-intolerant/ineligible patients. A third phase 3 study in genotype 1 patients will be initiated in the second half of 2012, the design of which is dependent on the outcome of phase 2 studies which are evaluating PSI-7977 in various combinations in genotype 1-infected patients. If successful, this strategy could lead to an initial US regulatory approval of PSI-7977 in 2014. PSI-938, an unpartnered guanosine nucleotide analog, is being tested in a phase 2b interferon-free trial as monotherapy and in combination with PSI-7977 in subjects with HCV of all viral genotypes. Mericitabine (RG7128), a cytidine nucleoside analog, is partnered with Roche and is being evaluated in three phase 2b trials. Roche is responsible for all aspects of the development of mericitabine.

"The acquisition of Pharmasset represents an important and exciting opportunity to accelerate Gilead's effort to change the treatment paradigm for HCV-infected patients by developing all-oral regimens for the treatment of the disease regardless of viral genotype," said John C. Martin, PhD, chairman and chief executive officer of Gilead. "Pharmasset presented compelling phase 2 data earlier this month further characterizing the strong efficacy and safety profile of PSI-7977. The compound, together with Pharmasset's other pipeline candidates, represents a strong strategic fit with Gilead's vision, pipeline and capabilities. This transaction will serve to drive the long-term growth of our business, and we look forward to working closely with the Pharmasset team to advance a broad clinical program in HCV to address the unmet needs of patients and the medical community."

Pharmasset president and chief executive officer Schaefer Price said, "We are excited to join together with Gilead, which shares our commitment to providing HCV patients with new, highly efficacious and safe oral therapies." "We are very encouraged by the data from our phase 2 studies of PSI-7977 and believe strongly in the potential of this compound to be a component in the transformation of the treatment of chronic HCV. Gilead's established expertise and leadership in the field of antiviral drug development and commercialization, coupled with the company's existing portfolio of promising compounds for HCV, make this partnership an ideal step to fully realize the potential of our promising molecules as part of future all-oral combination therapies for millions of patients in need around the world."

Gilead's research and development portfolio includes seven unique molecules in various stages of clinical development for the treatment of HCV. Pegylated interferon in combination with ribavirin is currently part of the standard of care treatment for patients with chronic hepatitis C. Gilead is focused on advancing multiple compounds with different mechanisms of action and resistance profiles in combinations that will support delivery of an all-oral regimen that would eliminate the need for pegylated interferon. Three separate all-oral phase 2 studies are currently ongoing, and Gilead expects clinical data from these studies to become available in 2012 and early 2013. Pharmasset's compounds are complementary to Gilead's existing HCV portfolio, and the transaction will help advance Gilead's effort to develop an all-oral regimen for the treatment of HCV.

Under the terms of the merger agreement, a wholly-owned subsidiary of Gilead will promptly commence a tender offer to acquire all of the outstanding shares of Pharmasset's common stock at a price of $137 per share in cash. Following successful completion of the tender offer, Gilead will acquire all remaining shares not tendered in the offer through a second step merger at the same price as in the tender offer.

The consummation of the tender offer is subject to various conditions, including a minimum tender of at least a majority of outstanding Pharmasset shares on a fully diluted basis, the expiration or termination of the waiting period under the Hart Scott Rodino Antitrust Improvements Act, and other customary conditions. The tender offer is not subject to a financing condition.

The $137 per share price in the transaction represents an 89% premium to Pharmasset's closing share price on Friday, November 18, 2011, the last trading day prior to announcement, and 59% to Pharmasset's all time high closing stock price.