Dementia expert Dr. Jason Karlawish told CNBC he was skeptical of that Approved by the Food and Drug Administration of BiogenicAlzheimer’s drug Aduhelm said “the evidence to support the drug’s approval was insufficient”.

“Another study is needed to see if this drug is actually effective. Unfortunately, the FDA has approved the drug for marketing, although they also want another study,” said the co-director of the Penn Memory Center at the University of Pennsylvania on Monday after the agency’s formal OK.

The FDA approval marks that first new treatment for Alzheimer’s in almost two decades. Alzheimer’s is a progressive neurodegenerative disease that slowly destroys memory and thinking skills. More than 6 million Americans are reportedly living with the disease Alzheimer’s Association estimates.

Carlavian told “The News with Shepard Smith” that there are many promising Alzheimer’s drugs in the pipeline.

“I’m optimistic about the future here so I have hope. I just think this is not the drug we can put our hopes on,” he said. “Desperation should drive funding for Alzheimer’s research, not interpretation of scientific evidence.”

Clinical studies have found that some patients who received the approved dose of Aduhelm had painful brain swelling.

“What you are asking someone to do is risk an uncertain benefit but a known risk,” said Karlawish of prescribing the drug to patients.

The FDA said it would continue to monitor the drug when it hits the US market. The agency granted approval on the condition that Biogen conduct another clinical study.

Karlawish told host Shepard Smith that Biogen will face a challenge “how to conduct this study when the drug is also available for clinical prescription.”

Representatives from Biogen and the FDA did not immediately respond to requests for comment on Karlawish’s statements.