New antiviral treatment rescues kitten from deadly feline illness

At the Virginia-Maryland College of Veterinary Medicine, veterinarians are using a drug related to the antiviral remdesivir to cure feline infectious peritonitis (FIP), a disease that until recently meant certain death.

For Lanala, a 6-month-old kitten who received the treatment, it's meant a second chance at life. 

A race against time 

"She wasn't moving at all. Her legs weren't working," said Lanala's owner Juan Carlos Arevalo, who watched their once-playful kitten deteriorate rapidly. "We thought she was going to die." 

The kitten arrived at the college's Veterinary Teaching Hospital with mounting neurological signs — twitching, a head tilt, and difficulty coordinating her front legs. Her condition was worsening by the day. 

Leanne Jankelunas, a second-year neurology and neurosurgery resident, remembers Lanala's arrival clearly. "She presented with incoordination and vertigo-like signs. Things had been progressing pretty rapidly. She had lost weight, wasn't eating, and was very lethargic and dull." 

The diagnosis challenge 

John Rossmeisl, the Dr. and Mrs. Dorsey Taylor Mahin Professor of Neurology and Neurosurgery, was brought in to consult. "Dr. Jankelunas and I made the diagnosis when the cat was first admitted," Rossmeisl said, reflecting on decades of experience with the disease. "FIP was a hopeless diagnosis for many, many years. Sadly, I've seen many cats suffer and die with FIP."

The statistics tell a devastating story: FIP affects approximately 1 to 2 percent of the cat population worldwide each year with an estimated 96 percent mortality rate without treatment. Historically, once clinical signs developed, affected cats had only weeks to live. 

"FIP is never an easy diagnosis because there's not a single test that's perfect for it," said Rossmeisl. "It's usually a combination of clinical findings and diagnostic findings. But Lanala had pretty classical clinical signs and MRI findings associated with FIP, so we were pretty confident with this one."  

An antibody test strongly supported their suspicions, with Lanala's score at 2,048 — far above the positive threshold of 128.

"It's particularly heartbreaking because she's just a kitten," said Rossmeisl. "And it's catastrophic because most of the time, all you can do is take some pills, but your cat's not going to live very long." 

Breaking new ground 

But on June 1, everything changed. A new oral medication called GS-441524 became available in the U.S., offering unprecedented hope. 

"Until recently, we had no effective treatments," Jankelunas said. "This is the first time we've been able to prescribe this drug, and it's been remarkable to see Lanala's positive response."

GS-441524 is closely related to remdesivir, the antiviral drug used to treat COVID-19 in humans. Both compounds work by inhibiting viral replication, interfering with the RNA-dependent RNA polymerase of coronaviruses.

"It's a great example of how translational medicine and research in human medicine can lead to breakthroughs in veterinary care, and vice versa," Jankelunas said.

The road to recovery 

Lanala's response to the new treatment was swift and dramatic. "I remember a day or two later, the owner reported improvement," Jankelunas said. "I saw her within five or six days of starting the drug, and I remember thinking, 'Oh my goodness, it’s working.”

The treatment requires careful monitoring for signs of medication resistance or decline and weight-based dosing. "We're using an antiviral agent, so it's very much weight dependent," Jankelunas said. "She was either coming to us or her local vet for weekly weigh-ins to ensure as she gained weight, her dose remained appropriate." 

After about eight weeks into a 12-week treatment, Lanala's progress has been remarkable. "Her neurologic signs as of today are completely resolved," Jankelunas said. "You wouldn't recognize her if you compared her to how she was initially." 

Arevalo watches in amazement as their kitten plays with toys she couldn't even look at weeks ago. "She's really good now. Every day, there's progress. She's moving, playing, and jumping. Before, we had to put food right in front of her. Now, she's acting like a normal cat." 

While GS-441524 shows great promise, the treatment typically lasts 12 weeks and can be costly. While related to Food and Drug Administration-approved remdesivir, the drug is still working through approval processes in most countries. 

A new chapter in feline medicine 

For cats like Lanala and owners willing to invest in their pets' health, the new treatment offers something previously unthinkable: a chance at survival. 

"At that point we would have done anything to help save her, and we are so glad things worked out so well." Arevalo said. "It's good to see the progress. Seeing her play and jump again — it's worth everything." 

"This new protocol is giving us hope for cats that previously had none," Jankelunas said. "It's not just treating a disease — it's giving beloved pets a second chance at life. It's a game-changer in feline medicine."