Jeffrey Bluestone, co-leader of the research at the University of California, San Francisco, said patients who benefited most were those who still had relatively good control of their blood sugar levels and only a moderate need for insulin injections when the trial began.
With the experimental drug, teplizumab, they study participants were able to maintain their level of insulin production for a full two years -- longer than with most other drugs tested against the disease, Bluestone said.
However, the treatment did not benefit all patients -- about half or more lost their ability to produce insulin -- a drop similar to many of the controls not receiving the drug.
Reasons for the different responses are unclear, but likely involve differences in the metabolic condition of the patients and in the severity of their disease at the trial's start, the researchers said.
"The benefits of treatment among the patients who still had moderately healthy insulin production suggests that the sooner we can detect the pre-diabetes condition and get this kind of drug onboard, the more people we can protect from the progressive damage caused by an autoimmune attack," Bluestone said in a statement.
Formerly referred to as juvenile diabetes because it disproportionately strikes children, type 1 diabetes is caused by an autoimmune condition in which the body's immune system destroys insulin-producing beta cells in the pancreas, Bluestone explained.
The findings were published in the journal Diabetes.