A new drug for Alzheimer’s disease, called LMTX, has been found ineffective in its first large clinical trial to check the rate of progression of mental disability and daily functioning. The drug, however, may be effective for certain patients.

Developed by TauRx Therapeutics, LMTX tried to undo so-called tau tangles in the brain and the drug was the first one with its mode of action to reach the final stage of clinical trials. As the eagerly awaited results of the study appeared, all those concerned were left disappointed.

The study showed that patients who received LMTX did not have a slower rate of decline in mental ability or daily functioning than those in the control group. About 15% of the patients in the study were given LMTX as their only therapy while the remaining 85% were put on Alzheimer’s drug in addition to either LMTX or a placebo.

“There were highly significant, clinically meaningful, large effects in patients taking the drug as monotherapy, and no effect in patients taking it as an add-on”, said Claude Wischik, a founder and the chief executive of TauRx, while speaking from Toronto where the results were being presented at the Alzheimer’s Association International Conference.

Dr. Wischik said they found the same phenomenon in a second clinical trial, sponsored by the company, whose results were yet to be announced. TauRx Therapeutics now plans to apply for approval of LMTX for use by itself.

Some experts in the field, however, were skeptical about drawing conclusions from a small subset of patients, especially since there was no obvious explanation why LMTX would be expected to work only in patients not getting other drugs.

“I have to say that the results that we saw here were, to me, more disappointing than not,” Dr. David Knopman, a neurologist at the Mayo Clinic, said.