GlaxoSmithKline (NYSE: GSK) received an offer from Aspen Pharmacare Holdings Ltd. for branded heart medicines Arixtra and Fraxiparine and a related manufacturing site as it seeks to sell older medicines with declining sales.

The deal estimated to be worth $1 billion, according to Reuters.

If the deal goes through, a lot of GSK employees would be transferred to a new employer.

The products generated about 420 million pounds ($656 million) in global revenue in 2012 compared with 510 million pounds the previous year, Simon Steel, a spokesman for London- based Glaxo, said Tuesday The sale excludes rights to the products in China, India and Pakistan, Glaxo said in a statement.

Arixtra and Fraxiparine are part of a portfolio of more than 50 older products that Glaxo has carved out into a separate unit, according to Steel. The decision follows a similar move by Pfizer Inc., which is considering splitting its branded and generic-drug businesses into separate units.

“The proposed transaction is aligned to Glaxo’s strategy of focusing on products with the most growth potential and the delivery of its pipeline,” the company said.

Glaxo owns a 19 percent stake in Aspen, a Johannesburg- based maker and distributor of generic medicines. Aspen agreed to buy pharmaceutical and over-the-counter brands from Glaxo in two separate transactions last year to boost its expansion in Australia, South Africa and Brazil.

The manufacturing site tied to the sale of the drugs is located in Notre Dame de Bondeville in northern France, according to Glaxo, which declined to disclose the financial terms of the sale.

Reuters reported that the deal would be worth $1 billion or more if Aspen were to pay “twice this year’s estimated sales.”

The deal is subject to consultation with employees, Reuters added. 

Reuters added that “about 1,000” employees would transfer to Aspen.

GSK operates its North American headquarters in RTP.

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