NEW YORK ( TheStreet) -- Shares of SIGA Technologies ( SIGA) spiked higher in extended trades on Friday after the company said it's received a five-year contract from the federal government to provide two million courses of its smallpox antiviral medication ST-246.

The deal has a base value of $433 million, and includes options that could bring the value of the contract up to $2.8 billion if the maximum delivery of 12 million courses is exercised. SIGA was awarded the contract by the Biomedical Advanced Research and Development Authority of the Department of Health and Human Services.

The stock was last quoted at $15.88, up 12%, on volume of around 140,000, according to Based on a regular session close at $14.19, the shares had gained 3.4% so far in 2011.

"We believe that the funding to extend ST-246 to these vulnerable populations is critical to the future success of the U.S. government's smallpox biodefense efforts," said Eric Rose, the company's chairman and CEO, in a press release. "There are approximately 64 million children in the United States (through age 15), none of whom is currently vaccinated against this disease."

SIGA said ST-246 has been designated for "fast track" status by the Food and Drug Administration, "creating a path for expedited FDA review and eventual regulatory approval."

The four analysts covering the stock were already bullish ahead of the news with two rating the shares at strong buy, and two at buy. The median 12-month price target for the stock sits at $17.

Elsewhere in the after-hours session, Rambus ( RMBS) shares continued to sink, falling 2% to $15.50 on late volume of around 150,000. The move extended an 18% decline in the stock in the regular session after the company suffered a setback in its ongoing memory technology patent dispute with Micron Technology ( MU) and Hynix Semiconductor.

Also, Merck ( MRK) got a slight lift on news of that the company has received regulatory approval of its Victrelis hepatitis C drug.

Shares of the Dow component were last quoted at $37.30, up 22 cents, on extended volume of 155,000. Year-to-date, the stock has risen 3%.

The decision to approve Victrelis was widely expected following a positive recommendation from an outside advisory panel last month. Merck has not yet disclosed pricing for Victrelis, which is used in combination with long-acting interferon and ribavirin.

-- Written by Michael Baron in New York.

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