In one of the most sweeping and rare bipartisan acts of this Congress, lawmakers will move this week on a $6.3 billion bill to increase funding for research into cancer and other diseases, address problems in the nation's mental health systems and enact potentially far-reaching regulatory changes for drugs and medical devices.

The bill, known as the 21st Century Cures Act, is the product of years of debates over health care policy issues, including how to track the federal drug regulatory structure with the fast-paced world of biotechnology, streamline the unwieldy mental health care system, and stem the widespread and intractable problem of opioid drug abuse.

But critics say the act contains a number of regulatory changes that could profoundly reshape the way some drugs and medical devices are approved in the United States, making the process less costly and time consuming for companies, but also potentially less safe for patients.

"This is all in the category of dumbing down the criteria for drug approval," said Dr. Jerry Avorn, a professor of medicine at Harvard. "It's a lower bar and shorter race."

Democrats, conceding the legislation makes more changes to regulations than they sought, note that the bill has fewer changes than an earlier version out of the House, and far fewer than they would expect in the next Congress. People who support the bill say it simply codifies quicker pathways that the Food and Drug Administration was already using.