Cassava Sciences, a small biotechnology company based in Austin, Texas, announced it would stop the advanced clinical trial for an experimental Alzheimer’s drug, ending a long-contested bid for regulatory approval.

The company announced on Monday that the drug, simufilam, did not significantly reduce cognitive decline in people with mild to moderate Alzheimer’s disease in the trial, which enrolled more than 1,900 patients.

“The results are disappointing for patients and their families who are living with this disease and physicians who have been looking for novel treatment options,” the company’s chief executive, Richard J. Barry, said in a statement.

These results were unsurprising to many dementia researchers, who had questioned why the trial had been allowed to proceed in the first place, since much of the drug’s underlying science had been called into question.

Studies that once seemed to support the drug have been retracted from scientific journals. A consultant researcher who helped conduct some of the drug’s foundational studies was charged with fraud by a federal grand jury for allegedly falsifying data to obtain research grants.

In September, the company settled with the Securities and Exchange Commission over allegations that Cassava had made misleading statements about the results of earlier clinical trial data. However, the company neither admitted nor denied wrongdoing.

Even so, the company forged ahead with its Phase 3 clinical trial — typically the last evaluation before the Food and Drug Administration decides whether to approve a medication for public use — and maintained that there was still research and clinical results that suggested the drug could prove valuable.

Hopes in the drug’s efficacy were dashed by Monday’s results, though the company said the trial still showed the drug was safe.

Cassava’s future now appears to be in flux, as simufilam was the company’s only drug in clinical trials.

Following the company’s investor call Monday morning, Cassava’s stock price dropped more than 80 percent, a blow to the company’s loyal investors, who once valued the company at more than $5 billion.