Originally Published: 21 MAR 23 07:39 ET

By Jen Christensen, CNN

(CNN) -- Doctors across the United States who treat people with advanced prostate cancer can't find supplies of a medicine that may help them live longer.

Pluvicto, a drug to treat metastatic castration-resistant prostate cancer, also known as mCRPC, is in such short supply that its maker, Novartis, said it cannot allow further supply until it can produce more of the drug. It has also had to reschedule people who were about to get their first doses.

"We recognize that any rescheduled dose is distressing for patients and their loved ones and poses challenges for the treatment centers. We are striving to serve as many patients as possible as quickly as possible as we work through the current situation," Novartis said in a news release from March 9, which the company said is its most up-to-date information.

The Swiss company said it has been in touch with treatment centers and providers in the US and is "actively engaging with them to manage rescheduling of patient doses."

The problem is that Novartis' manufacturing facility in Ivrea, Italy, can't keep up with demand for the drug. In May, it had to suspend production at the facility due to what it said was "an abundance of caution" related to potential quality issues. It also paused production at a New Jersey plant that makes the drug for the Canadian market.

Novartis resumed production at both plants in June.

The company hopes to get the New Jersey plant authorized to produce the drug for the US market, but it's not clear when that might happen. Novartis said in early March that it had completed its filing for approval from the US Food and Drug Administration.

Someone who has a late-stage cancer that has spread to other parts of the body doesn't have a lot of time to wait for the company to make more, doctors say, nor do they have many other treatment options. So even if Novartis got approval for the New Jersey plant quickly, the help will come too late for many people, according to Dr. Daniel Spratt, chair of the Department of Radiation Oncology at University Hospitals Seidman Cancer Center in Cleveland.

Novartis said it is prioritizing people who are currently being treated with Pluvicto, which is given in six cycles. But Spratt said the supply has recently been too low even for some of these patients.

"Many patients are missing months of therapy," he said. "The real tragedy is the patients partially under treatment who have had great responses and we can't get them the rest of their therapy in a timely fashion."

Next to skin cancer, prostate cancer is the most common cancer in American men, according to the American Cancer Society. Most men do not die from prostate cancer, but about 34,700 people are expected to die from it this year. It's the second leading cause of cancer death for American men, behind only lung cancer.

Pluvicto is a targeted radioligand therapy, meaning it uses radioactive atoms to deliver radiation to targeted cells, fighting cancer while limiting damage to the surrounding tissues.

There is no cure for this advanced stage of cancer, but Pluvicto can help people live longer. When the drug got FDA approval in March 2022, Spratt said, there was a lot of excitement about its potential. His patients who had heard about the trials have been asking about it for years.

One study from Novartis' trials found that people who got the drug lived a median of about 15 months after diagnosis, four months longer than the median for people who didn't get the treatment. For a handful of people, the recovery is even more dramatic.

"There are some patients that really do have those sort of miraculous responses, so it does occasionally give us one of those 'wow' moments," said Dr. William Dahut, chief scientific officer at the American Cancer Society.

Dahut said doctors also like Pluvicto because, compared with other cancer treatments, it's easy to administer and has relatively few side effects, other than dry mouth.

Another side effect of the shortage is that it's slowing the progression of research. There is some indication that the drug could help people before their cancer reaches such a late stage.

"We're anxious to have greater supply to study it in broader populations," Dahut said.

Spratt said he is working closely with the medical oncologists in his health care system to try to find alternative treatment options, and he's been looking to get people into clinical trials so they can get access to the therapy.

"But there's really very few options available," he said.

Novartis said that if the FDA approves its plant in Milburn, New Jersey, it could supply more Pluvicto as early as this summer.

The agency told CNN that it "is not able to discuss details regarding any possible communications or actions with companies due to commercial confidential information."

"To be clear, FDA does not manufacture, produce, bottle, or ship drugs and cannot force companies to do so or make more of a drug. However, in general, the FDA works with firms making drugs in shortage to help them ramp up production if they are willing to do so. Often, they need new production lines approved or need new raw material sources approved to help increase supplies. FDA can and does expedite review of these to help resolve shortages of medically necessary drugs."

Novartis is also building a plant in Indianapolis where the drug will be produced, but that won't be up and running until the end of the year, the company said.

In the meantime, doctors will often have to tell their patients that they probably won't be able to help get them this life-extending drug for some time.

"Some men and their physicians will feel that some hope was taken from them," Spratt siad. "Cancer is the enemy here, not the company, but it's unfortunate to have that excitement that your physician will be able to prescribe it to you and just not be able to give it to them."