By Jen Christensen, CNN

(CNN) — Tim Andrews knew that he needed dialysis to manage his end-stage kidney disease, but over months of treatment, he started to wonder whether it was worth it. He was exhausted and hopeless. He missed his grandkids.

It kept him alive, but it didn’t feel like living.

Desperate for another option, he found a surprising alternative: an organ from a pig.

Andrews, 67, is a pioneer of a new kind of medicine. In January, he had an experimental cross-species transplant of a kidney from a genetically modified pig. He is one of only a handful of patients who have undergone the experimental procedure. For now, he’s the lone person in the United States known to be living with a pig kidney.

Andrews knew that there was a risk to trying something so new, but if the kidney gave him just one more day free from dialysis, it was worth it — for him and for fellow patients.

“This will do something for humanity,” Andrews said.

‘Pick a box’

Andrews had been living with diabetes since the 1990s, managing the condition with insulin. About 2½ years ago, he went to the doctor feeling unusually tired. Tests showed that he had stage 3 kidney failure — his kidneys were still working but less efficiently than they should. He was relieved to learn that it was manageable with medication, monitoring and lifestyle changes.

But about a month later, a doctor delivered more bad news: Andrews’ kidney disease had rapidly progressed to end-stage disease. Dialysis was the only option to keep him alive until he could get an organ transplant.

Dialysis is highly effective at cleaning the blood, but it places a “huge burden” on the body, Andrews’ doctors told CNN. At first, Andrews thought it was going well. But about six months in, he had a heart attack.

“It takes a toll on you, emotionally and physically,” said Andrews, who lives in New Hampshire.

He was tempted to forgo dialysis entirely until a doctor warned that if he did so, he should “pick a box.” With the state his kidneys were in, his body would be in it within a couple months.

For six hours, three days a week, he kept at it. On days off, he’d sleep. By the time he woke up, he’d have to start the process all over again.

When he thinks about his experience with dialysis, Andrews appreciates what the doctors and nurses did to keep him alive. But when he kept having to sit in that oversized green chair hooked up to the dialysis machine, the whole situation hurt his spirit, too.

He was too tired to walk or get groceries. He couldn’t eat. Even in the few hours he felt OK, his immune system was so weak that he had to avoid crowds. Dialysis meant no more Red Sox games, no more fun with grandchildren, no more travel.

As the hours ticked past, he couldn’t think about gratitude. All he could think about was death.

The dialysis side effects got so bad that he wanted to quit, but his wife, Karen, wouldn’t let him. He also kept hearing his father’s voice in his mind, telling him to stop complaining and start doing something about his situation.

‘I know what end-stage means’

Andrews learned that his odds of getting a human kidney donation were not good.

Nearly 90,0000 people are on the waiting list for a kidney in the US. Most don’t get a transplant because they become too sick or die while waiting for a match.

Andrews’ chances were slimmer than most because of his rare blood type. People typically wait about three to five years for a donor kidney. For him, it would likely be seven to 10 years. Doctors thought his body could take only five years of dialysis.

“I was a little short there,” Andrews said. “I know what end-stage means.”

But his research gave him hope. Massachusetts General Hospital was also investigating animal alternatives. He demanded that the hospital liaison put him in touch with one of the doctors from that project: Dr. Leonardo Riella, medical director of kidney transplantation at Mass General.

When they first met, Andrews was “very frail,” Riella said. He arrived in a wheelchair. But when Riella mentioned what’s known as xenotransplantation — transplants using genetically modified pig organs — Andrews’ eyes “sparked.”

“He said ‘Tell me what I need to do.’ ”

Riella told Andrews he’d need to get a lot stronger if he wanted a transplant of any kind.

“They said, ‘Prepare your body for battle,’ ” Andrews’ wife, Karen, remembered.

For the next few months, Andrews went to the gym and physical therapy, got his teeth fixed, got several vaccines and lost 22 pounds.

When he went back to the clinic a few months later, Riella said, Andrews was “almost running around the room.”

He talked to people about the procedure. He prayed. His wife, Karen, also had to agree: If they got the green light, she would need to sign consent papers. On the slim chance he got a virus from the organ, she’d be exposed to it, too.

“I was a little taken aback by that,” Karen said. But she didn’t have any doubt that this transplant, though unusual, was the right way to go.

“It has to be better than dialysis,” she said. “He was just feeling so awful all the time.”

A new birthday

In January, it was finally time.

On surgery day, his family hugged and kissed him good-bye. Karen gave him a high-five and wished him luck.

The procedure was supposed to take four hours, but only about two hours and 15 minutes in, Karen said, her phone rang. The doctors were done early and said it went “unbelievably well.”

A team of doctors told Karen that they had successfully attached the genetically modified pig kidney alongside Andrews’ nonfunctioning organ.

“They put the kidney on the table and started connecting him to the kidney, and he actually peed across the room,” Karen said, laughing. Everyone in the operating room started cheering.

“Of course, I started bawling like a baby,” Karen said.

It all happened so fast that even the doctors who did the surgery were surprised.

“It worked right away, and the numbers started getting better,” Riella said.

After waking up from surgery, Andrews felt “reenergized and revitalized.”

“I was alive, and I hadn’t been in a long time,” he said.

He hopped off the bed and tap-danced across the room, he said. His mind felt clear.

“It was a miracle,” Andrews said. So much so, he declared that he had a new birthday.

“I said ‘look at me, it’s like I’m like a new man,’ ” he said. “It’s like new birth. I said, ‘I’ve got a new birthday. 1/25/25 is my new birthday.’ ”

‘Now I can do anything I want’

After the transplant, Andrews spent a week in the hospital but only out of an abundance of caution.

In the months since, he’s had a few “small bumps in the road,” including a three-week hospital stay. But the pig kidney does what a kidney from a living human donor would do.

Life is returning to normal. Andrews cooks, vacuums and takes long walks with his dog, Cupcake.

He currently takes more than 50 pills every day as the doctors try to figure out the type of medications he’ll need with his new kidney. But living without dialysis has made such a difference.

“Basically, I was just sleeping, sick all the time. Now I can do anything I want,” Andrews said.

He even lets himself picture a future. He can’t wait to see his grandkids again.

“They saw me at the lowest, and now they’ll be able to see me alive and laughing and carrying on like Grandpa does,” Andrews said.

If all goes well, he hopes to take Karen to Europe in a year. He said they’ve put it off far too long.

‘It’s a learning curve’

Still, Andrews knows that the pig kidney may not work long-term. He’s still on the wait list for a human organ. If the pig kidney can act as a bridge that keeps him healthy enough to wait for a match from a human donor, that would be a medical first — and a success.

Andrews is the fourth living patient in the US to get a genetically modified pig kidney transplant, and he won’t be the last. In addition to the ongoing trial at Mass General in conjunction with biotech firm eGenesis, United Therapeutics Corp – the other main biotech company helping create the pig kidneys – announced in February that it would be allowed to start its own clinical trials with New York University.

In March 2024, Richard Slayman became the first living patient in the world to get a genetically modified pig kidney. The operation at Mass General went well, but he died two months later from causes not related to the transplant.

Doctors said they learned a lot from their experience with Slayman. He had scarring on his heart after eight years of dialysis, Riella said, and it’s probably important to get patients like Andrews, who haven’t needed dialysis as long.

In April 2024, Lisa Pisano became the first person to receive a mechanical heart pump as well as a gene-edited pig kidney. The organ failed due to limited blood flow and was removed the next month. She died in July 2024.

Then, in November 2024, NYU transplanted 53-year-old Towana Looney with a genetically modified pig kidney. It functioned for four months and nine days, the longest yet, but doctors had to remove it in April when her immune system started to reject it.

Figuring out how to manage rejection is going to be key, doctors say. The pig kidneys Andrews and Slayman got had 69 genomic edits, while Looney’s had fewer. Doctors say they still don’t know how many edits are necessary, but both versions of the modified pig kidneys had pig genes removed and human genes added to make the organ more compatible with the human body.

Patients also receive anti-rejection drugs and wearable remote monitoring tools. But doctors still are figuring out how much medicine and monitoring is needed.

“It is a learning curve,” Riella said.

Riella is hopeful xenotransplantation may one day solve the world’s organ shortage.

“I think patients like Tim will be remembered as heroes,” he said. “Without them willing to take the risk, we wouldn’t be able to move this to the clinic.”

Andrews remembers what it felt like to have to make the choice. But he also remembers what it was like to sit for hours at the dialysis center.

“It’s hard to come to terms with mortality. You think ‘ah, I can handle that’ and everything, but it’s tough,” he said recently, back in the green chair where he underwent dialysis. “It was very tough to realize that was it.

“I was going to die in this building.”

He found a way out. He hopes his story will inspire others to look for hope, too.

“I see way too many people give up,” Andrews said. “Don’t give up.”

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CNN’s Dr. Sanjay Gupta, Amanda Sealy, Nadia Kounang, Rayna Sims and Melissa Dunst Lipman contributed to this report.