U.S. regulators are preparing guidelines telling drug makers how they can streamline the testing of experimental medicines by conducting more flexible clinical trials, a top official said on Monday.

The Food and Drug Administration wants to encourage “adaptive” clinical trials that change mid-way through, said Dr. Scott Gottlieb, deputy FDA commissioner for medical and scientific affairs.

The approach is a departure from the rigid structure of most drug studies required for FDA approval in which companies, patients and physicians do not know results until the research is completed. Such “blinding” is usually mandated to keep doctors or patients from acting in a way that could affect a study’s outcome.

But looking closely at results throughout a study could give an early sense of whether a drug works and which types of patients benefit most, Gottlieb said. The information could be used to modify trials mid-stream to include more of those patients, or to drop the study if a drug appears ineffective. Changes could help companies reduce the cost of bringing a drug to the market.

“These new approaches to clinical trials can result in trial designs that tell us more about safety and benefits of drugs, in potentially shorter time frames, exposing fewer people to experimental treatments,” Gottlieb said in remarks prepared for delivery at an adaptive trials conference.

Gottlieb acknowledged that such designs could lead to “complicated decisions and uncertainty about the best approach for data analysis.”

“It may also be true that making decisions during a trial’s course can increase the rate of making an erroneous decision,” he added.