A new medication for A.L.S., the devastating neurological disorder that causes paralysis and death, will have a list price of fifteen grand a year.

The treatment, to be marketed as Relyvrio, is a combination of two drugs and will be available to patients in the United States in about four to six weeks.

The FDA approved Relyvrio on Thursday despite the fact that there wasn't enough evidence to show that the medication could help patients live longer or slow the rate at which they lose functions.

The F.D.A. decided to approve the drug instead of waiting for the results of a large clinical trial due to the fact that the treatment is considered to be safe. The agency said that given the serious and life threatening nature of A.L.S., this level of uncertainty is acceptable.

Patients with A.L.S., also known as Lou Gehrig's disease, often die within two to five years of being diagnosed. According to Amylyx, there are about 29,000 people living with the disease in the US.

Most patients will pay little or nothing for the treatment because the company expects insurers to cover it. Amylyx will give it away to uninsured patients.

The Institute for Clinical and Economic Review recommends a lower list price for medicines. There are clear benefits to patients with a rapidly fatal disease to have early access to a safe therapy, according to the group's chief medical officer.

Patients would benefit from a price closer to the price of production of Relyvrio rather than a price more than five times higher than the top of a value-based range.

The founder of Amylyx said on Friday that the price was chosen after meeting with insurers, patients, doctors and others. He said the company considered what would allow it to invest in new treatments so that A.L.S. first becomes a manageable chronic condition and eventually is cured.

Two other A.L.S. medications have been approved by the F.D.A.. It costs less than $10,000 a year to use riluzole and it can extend survival by several months. Symptom progression can be slowed by 33 percent with the aid of Edaravone. The oral form of radicava has a list price of $171,000 a year. In the company's clinical trials, many patients took Relyvrio, a powder mixed with water, along with one or both of the other medications.

Mr. Klee and Joshua Cohen were undergrad students at Brown University when they came up with the idea of Relyvrio. Combining a prescription medication and an over-the-counter supplement could protect the brain from diseases like A.L.S., according to a proposal.

Mr Klee said that the company expected private insurers to cover the drug with no co-payments for patients, and that Amylyx would work to make it affordable for people on Medicare or Medicaid who are financially struggling. Patients had been obtaining the ingredients on their own for some time, buying the supplement from Amazon and paying up to $11k a month for the phenylbutyrate.

"Now that our product is approved, we have to be laser focused on making sure that people can access it."

Patients who developed symptoms of A.L.S. within 18 months before the trial were affected in at least three body regions which is a sign of fast-progressing disease. The approval of the F.D.A. did not prevent patients from using the medication. According to Mr. Cohen, Amylyx didn't have a projection of how many would be.

He said that people in different circumstances are going to make different treatment decisions.

A small trial of Relyvrio was conducted in Alzheimer's patients.

He said that the drug was designed to target pathways of neuronal death, which is an important part of A.L.S.