Pfizer Inc on Thursday named Martin Mackay, one of its senior research executives, as its new research chief, and selected a Merck & Co Inc research officer to head clinical development of its medicines.

The world's largest drugmaker, which has been unable in recent years to launch many big-selling drugs despite an annual $7 billion research budget, also said it is setting up a stand-alone biotherapeutics center in California to discover new biotech medicines and technologies.

Pfizer said the new biotherapeutics unit will be headed by Corey Goodman, a member of the National Academy of Sciences.

We are also today launching a new biotherapeutics and bioinnovation center with a unique structure to discover, license and acquire more new product candidates that we can put into development, Pfizer Chief Executive Officer Jeff Kindler said in a press release.

Mackay, a 12-year veteran of the company, most recently has served as vice president of global research and development. He is succeeding John LaMattina, who in May said he would retire by year-end as president of R&D after 30 years with the drugmaker.

Pfizer said its new head of clinical development, Briggs Morrison, most recently was senior vice president of research planning and integration at Merck. Previously, he was Merck's head of clinical development, the stage of research when medicines are tested in humans.

Revenues at Pfizer, whose shares are trading at levels seen in 1997, have fallen in the past two years due to generic competition for former blockbuster Pfizer drugs such as anti-depressant Zoloft and blood pressure treatment Norvasc.

Meanwhile, promising drugs in development have failed clinical trials, while approved products have failed to generate hoped-for sales. The company badly needs new medicines to return to the strong earnings growth of past years and satisfy frustrated stockholders.

Pfizer on Thursday said it aims to dramatically raise the bar on productivity within its research laboratories, and has begun to streamline and consolidate its operations, with hundreds of scientists having been relocated to different sites.

The company's biggest research setback to date came last December, when it halted clinical trials of its highest profile medicine in development, a cholesterol drug known as torcetrapib, due to safety concerns.

Pfizer and its investors were counting on the drug to generate annual sales of $10 billion or more and replace its best-selling drug, Lipitor, which is slated to lose patent protection as early as 2010.

In July 2006, Pfizer ousted CEO Hank McKinnell and replaced him with Kindler, the company's general counsel.

(Reporting by Ransdell Pierson)