Senator Ron Johnson (R-Wis.) isn’t mincing words about his so-called “right to try” bill, signed into law by President Trump on Wednesday. In a feisty letter to Food and Drug Administration Commissioner Scott Gottlieb Thursday, Johnson put things bluntly: “this law intends to diminish the FDA’s power.”

The revelation substantiates a leading criticism of the law, which was otherwise pitched as a compassionate measure to help people suffering from life-threatening illnesses obtain easier access to experimental therapies. Critics feared it would simply undercut the agency’s regulatory power to ensure experimental treatments are used safely, while offering little aid to patients. After all, the FDA already has a prompt and lenient system for providing such patients access to experimental treatments, and 38 states already have similar “right to try” laws. Proponents, meanwhile, said the new federal law would give desperate patients hope and dismissed concerns that it would weaken the FDA.

But Johnson laid bare his regulatory intentions after being apparently infuriated by some of Gottlieb’s recent comments to reporters and on Twitter. Specifically, in a May 22 tweet, Gottlieb wrote, “When the House passes #RightToTry legislation I stand ready to implement it in a way that achieves Congress’ intent to promote access and protect patients; and build on #FDA’s longstanding commitment to these important goals #RTT.”

And in news articles, Gottlieb was quoted as saying he would work to “build in additional patient protections” alongside the law to ensure access but also safety.

Johnson is having none of that, according to his letter. “[This law] is not meant to grant FDA more power or enable the FDA to write new guidance, rules, or regulations that would limit the ability of an individual facing a life-threatening disease from accessing treatments.”

Johnson went on to request a meeting with Gottlieb as soon as possible in which he can further “discuss the law’s intent and FDA’s plans to implement the law consistent with that intent.”

Right to do what now?

As it stands, the right to try bill signed into law, which Johnson sponsored, will cut out the FDA’s role in approving and overseeing the use of experimental drugs in patients with life-threatening diseases. Such patients will be able to work directly with a doctor and a drug company to gain access—outside of a clinical trial—to an experimental therapy that has only made it through early clinical trials and not obtained FDA approval.

Prior to the new law, such patients in all states could do the same thing, but if their state didn't have its own “right to try” law, they had an added step of getting the FDA’s approval. That said, through the agency’s “expanded access” pathway, the FDA granted 99 percent of those requests and usually processed them in mere days. In emergency situations, the FDA granted them “immediately over the phone.”

In a recent commentary piece in the New England Journal of Medicine, medical ethicists raised concerns about cutting the FDA from the process. Namely, they noted that FDA sometimes gives guidance on how patients and doctors should go about their experimental treatment safely—and that guidance is sometimes based on undisclosed data to which the FDA has access.

Thus, the law “would cause patients to lose the benefit of meaningful safety-oriented changes that the agency recommends in 10 percent of expanded access approvals on the basis of confidential information that is often unavailable to treating physicians,” they wrote.

Other opponents fear that the law would leave patients vulnerable to less-than-scrupulous doctors or predatory drug developers, such as the hundreds of shady stem cell clinics that have popped up around the country.

“The agency has made substantial progress in balancing the needs of desperate patients and the principle that all patients deserve evidence that the benefits of medical products justify their risks,” the commentary authors conclude. “We upset that balance, and diminish the FDA’s public health mission, at our peril.”

Johnson, meanwhile, touts the new law as being “fundamentally about empowering patients.”