NEW YORK – Swiss pharmaceutical company Roche Holding AG will suspend its HIV research because none of its pending medicines represents a significant improvement over existing drugs, a company spokeswoman said on Friday.

“Research scientists currently working in HIV will be reassigned to other activities,” Linda Dyson, a spokeswoman in Roche's U.S. office in New Jersey, said in an e-mail.

Dyson confirmed an e-mail sent on Wednesday to activists informing them of the decision. In that communication, the company said it “decided to refocus our resources within virology on diseases in which we can deliver substantial improvements over existing medications.”

Dyson declined to specify how much Roche has been investing in HIV research.

The company said in the e-mail to activists that it had initially been excited about the potential for drugs in preclinical testing, but it has “concluded that none would provide a true incremental benefit for patients compared to medicines currently on the market.”

The launch of new drugs and an uptick in HIV cases is set to make AIDS medicine a $10.6 billion market by 2015, according to a study published last year by independent market research firm Datamonitor.

Roche said if it identified a scientific breakthrough in HIV outside of its labs, it would reassess its involvement with the area.

Peter Staley, founder of AIDSmeds.com, which tracks HIV-related news, said Roche has never come up with an AIDS drug that has sold really well.

“Roche is a big company and they've been trying to get this right for many, many years.” Staley said.

“It is disappointing that there is one less big pharmaceutical company in this field,” he said, but added: “I don't think it's a sign of a serious problem in pharma's commitment.”

Roche said it would continue to support its molecular diagnostic tests and medications already on the market, including the fusion-inhibitor Fuzeon.

Roche has partnered with Morrisville, North Carolina-based biotech company Trimeris Inc , to sell Fuzeon, which netted $266.8 million in sales last year.

But the drug struggled because its cost – $25,000 for a year's supply – exceeded the price of other HIV drugs on the market, Staley said.

(Reporting by Deepa Seetharaman, editing by Gerald E. McCormick)