AstraZeneca PLC reported mixed results for its new stroke drug Cerovive on Wednesday, finding that it helped patients recover from stroke as measured by one test but not by another.

AstraZeneca's Cerovive product director, Dr. Tomas Odergren, said he was "encouraged" by the data but that the drug's potential wouldn't be clear until other ongoing clinical trials were complete.

Analysts were cautious about interpreting the results. Previous attempts to develop similar drugs have failed.

"In our view, the data is likely to be viewed positively by the market which had very low expectations of success for the product," Merrill Lynch analyst Graham Parry said in a research note. "However, in our view the data remains inconclusive, [and] the product remains high risk."

The 1,700-patient study found that Cerovive, when taken within six hours of an ischemic stroke - those caused by a blood clot - increased recovery when measured by the modified Rankin scale. But patients saw no improvement when measured by a scale developed by the National Institutes of Health.

Stroke is the third-leading cause of death in the United States, behind heart disease and cancer, according to the National Stroke Association. There are about 750,000 strokes and 150,000 deaths every year, the association says. Most are ischemic strokes.

Analysts at Deutsche Bank, AstraZeneca's investment banker, estimate that Cerovive could produce more than $2 billion in sales globally.

Cerovive and diabetes drug Galida are AstraZeneca's only two major drugs nearing approval for sale. The drugmaker has its U.S. headquarters in Fairfax.