Medical researchers who sell secrets not only can taint ongoing research but — in the worst case — kill off a promising drug, doctors and drug-company executives say.

Dr. Stanley Crooke, the founder of Isis Pharmaceuticals, said leaking information can destroy clinical trials, which are designed to test whether a new drug works.

In most trials, doctors and patients are supposed to be "blinded" — meaning they don't know who gets the drug or the placebo. This keeps the research free of bias. By talking to doctors, investors are tearing away the blinds.

A doctor who hears from Wall Street that a drug is doing well might be tempted to select healthier patients with a better chance of benefiting from the study. That would distort the findings.

"How physicians feel can define what sorts of patients they actually put in clinical trials. How patients feel can influence a lot of the outcome," Crooke said. "I was deeply concerned and had been for a long time that practices like this risk the integrity of the clinical-trial process."

Dr. Drummond Rennie, deputy editor of The Journal of the American Medical Association, said simply, "When the data leaks out, it wrecks the trial."

Analyzing data is far more complicated than asking doctors for impressions. To do it right, companies must do time-consuming patient follow-up, record detailed health observations, crunch numbers from hundreds of patients, then fact-check it all, said Ben McGraw, chief executive of the California biotech company Valentis.

If Wall Street declares a drug dead before the study is complete, the company may run out of money before the drug is able to prove itself.

— Luke Timmerman