Some of the nation’s largest healthcare centers and insurers are refusing to use or cover a controversial new Alzheimer’s drug, positions that could limit how impactful it can be for patients as well as for its developer, Biogen.

First reported by The New York Times, the Cleveland Clinic and Mount Sinai have decided not to administer the drug, which was cleared for market in June and is sold under the brand name Aduhelm. Cleveland Clinic said its decision was based on available safety and efficacy data, while an official from Mount Sinai said the health system won’t consider giving Aduhelm until a federal investigation “affirms the integrity” of its approval.

At the same time, The Boston Globe reported Wednesday that six affiliates of Blue Cross Blue Shield won’t offer insurance coverage for Aduhelm, citing how, among other things, “a clinical benefit has not been established.” All six affiliates are located in populous states like New York, Florida and Pennsylvania.

And on Thursday, executives from the country’s biggest commercial health insurer, UnitedHealth Group, said it could take a while longer before they iron out Aduhelm coverage, as the company is waiting on guidance from Medicare, the government insurance program for people aged 65 and older.

“I think this has some way to go before we get to clarity, so I wouldn’t guide you to expect very rapid decision making on this,” said Andrew Witty, UnitedHealth’s CEO, on a conference call with analysts.

As most people with Alzheimer’s are older, Biogen expects most patients treated with Aduhelm would be covered by Medicare rather than through commercial insurance. The Centers for Medicare and Medicaid Services said this week it would weigh a single national policy for Aduhelm coverage.

Aduhelm is the first drug in nearly two decades cleared to treat Alzheimer’s. It’s also the first one ever approved that’s meant to slow the disease’s progression, rather than only alleviate symptoms.

While patients and their caregivers welcomed this treatment option, Aduhelm has been steeped in controversy. The two big clinical trials meant to show the drug works ended up with opposing results, which led the FDA’s own advisers and statisticians to conclude there wasn’t enough evidence to support an approval.

Despite the contradictory findings, the FDA not only approved Aduhelm, but put almost no restrictions in place for what kind of Alzheimer’s patient would be eligible to receive it. Notably, Biogen only tested Aduhelm in patients who were very early in the course of the disease.

Biogen made waves, too, by setting the drug’s initial price at $56,000, which experts fear could add tens of billions of dollars to Medicare spending.

What’s more, the FDA worked unusually closely with Biogen throughout the review process, a relationship that has since raised concerns about the agency’s objectivity regarding Aduhelm. Recent reporting from STAT News details how an off-the-books meeting between a top Biogen official and Billy Dunn, director of the FDA office that reviews brain drugs, got the ball rolling on a secret campaign by the drugmaker to get Aduhelm approved.

In an interview this week hosted by STAT, Janet Woodcock, the FDA’s acting leader, defended the decision her agency ultimately made. However, she did acknowledge that “it’s possible that the process could have been handled in a way that would have decreased the amount of controversy involved.”

“Was the process done exactly the best that it could be? Possibly not,” Woodcock added.

Last week, amid immense backlash for the Aduhelm approval, Woodcock asked the inspector general of the Department of Health and Human Services to review the interactions between Biogen and FDA officials and to determine whether they violated agency rules.

The FDA also revised the prescribing information for Aduhelm, instructing doctors to use it for patients with mild cognitive impairment or mild dementia.

For Biogen, these many moving parts further complicate an already challenging product launch.

The Cambridge, Massachusetts-based company had spent months preparing for Aduhelm’s debut, earmarking $600 million for commercialization expenses. By the time Aduhelm was approved, Biogen said 900 or so Alzheimer’s treatment centers appeared ready to administer the drug.

Now, though, big-name insurers and hospital systems are showing caution. Should that become a trend, it could create a significant problem for Biogen and the multibillion-dollar sales expectations that were set for Aduhelm.

At Mount Sinai, three issues are currently being worked through with regard to Aduhelm, according to a spokesperson. The first is a group of Alzheimer’s experts are establishing best practices for Aduhelm treatment. The second is a working group is creating formulary addition protocols. The third is the outcome of the inspector general investigation of Biogen and the FDA.

“Our local experts are continuing to work through those pieces but we will not infuse on our campuses until all our experts come to consensus after deliberating those three things,” the spokesperson wrote in an email to BioPharma Dive.

Similar processes are being carried out at other major medical centers around the country.

The Mass General Brigham in Massachusetts, for example, is not currently offering treatment with Aduhelm. A review by the hospital network’s pharmacy and therapeutics committee is expected to take three to four months, according to a statement on the system’s website. The Mayo Clinic, which has a partnership with Biogen on Alzheimer’s disease testing, is also still evaluating Aduhelm, Jonathan Graff-Radford, the institution’s division chair of behavioral neurology, said in an emailed statement.

Meanwhile, Cleveland Clinic physicians can prescribe Aduhelm, but patients must receive the drug elsewhere, according to The New York Times.