MINNEAPOLIS — Eli Lilly & Co. said its experimental Alzheimer’s treatment slowed the decline of cognition in some patients while failing to meet the primary goals of two large trials.

Lilly’s drug, solanezumab, delayed the worsening of mental loss in a subanalysis of patients with the earlier stage of the disease, the Indianapolis-based company wrote Friday. The medicine did not restore thinking, memory, or daily activities in any of the group’s studies.

The mixed finding was not expected by analysts, who had given the drug a less than 20 percent chance of showing any benefit. Still, doctors and investors said more study is needed to confirm the positive outcome. Earlier this month, a similar-acting medicine from Pfizer and Johnson & Johnson failed to help any group of Alzheimer’s patients in any way.

‘‘People expected nothing, and instead we have some hints of efficacy,’’ said Mike Krensavage, founder of New York-based Krensavage Asset Management who owns shares of Lilly. ‘‘The right thing now is probably to do another trial.’’

It is unclear whether the findings will be enough to get Food and Drug Administration approval since the drug did not meet its primary goal in either study. A benefit was seen only when the two trial results were combined and the company did an analysis looking just at patients with the mild and mild-to-moderate stage of the disease.

‘‘All these results ultimately will mean is that they have to do another study,’’ said David Knopman, a neurologist at the Mayo Clinic in Rochester, Minn., and head of the trials’ data safety monitoring board.

‘‘For patients and families, I don’t think this can be anything but mostly disappointing.’’

Lilly said it has not determined what steps it will take and is in talks with regulators.

An outside group of Alzheimer’s researchers will do their own analysis of the findings and the full data will be presented at two medical meetings in October, Lilly said.

The drugs now on the market only treat symptoms.