The Food and Drug Administration will soon be alerting companies that certain gene therapies in development can qualify for less arduous review at the agency, Commissioner Scott Gottlieb said Tuesday.

Specifically, gene therapies for hemophilia, a rare disease in which blood doesn’t clot properly because it lacks certain proteins, could be evaluated based on whether therapy increases those proteins in the blood, regardless of whether the therapy actually causes the patient to bleed less.

Gottlieb said that hemophilia is the first disease the FDA will target with its new policy. An FDA spokesperson later said hemophilia was chosen because “it’s an area of a lot of development activity.”

Gottlieb made these remarks at the annual board meeting of the Alliance for Regenerative Medicine. It was part of a broad speech about the promise of cell and gene therapies, which he said “will soon become the mainstay of how we treat a wide range of illness.” He said that the agency will release a “comprehensive policy framework” to guide companies on how to evaluate therapies for different sorts of diseases.

Gene therapies modify an individual’s genetic material in an attempt to treat a disease. They fall into a broader category of cell therapies encompassing many different treatments involving living cells.

One challenge, Gottlieb said, is that the traditional clinical trials companies need to complete before bringing a drug to the market may not be able to fully determine the “durability of response.” In other words, the effectiveness of the therapy might change after the trial is over, and initial signs that the drug works might not pan out upon further scrutiny. But because some of these treatments address patients with few other options, it may be worth the risk for them to undergo a treatment with indirect evidence of a benefit—protein levels in the case of hemophilia—even if there are some unknown future risks.

“These products are initially being aimed at devastating diseases, many of which are fatal and lack available therapy,” Gottlieb said. “In these settings, we’ve traditionally been willing to accept more uncertainty to facilitate timely access to promising therapies.”

A company may be required to perform more studies after the drug is on the market to make sure that the initial sign of success actually pans out, Gottlieb said. In the hemophilia example, he said, a company might have to demonstrate, after a product is on the market, that it actually does reduce bleeding.

This story has been updated with more detail on FDA’s choice of hemophilia as the first disease it will address with its new policy.

Republished with permission from STAT. This article originally appeared on May 22, 2018