An illustration of tegoprubart, a drug designed to help the human body accept transplanted organs.

Illustration: Courtesy of Eledon

This Drug Enables Breakthrough Organ Transplants

A new drug developed by a BC alum’s biotech company helped facilitate the world’s first pig kidney transplant.

As sixty-two-year-old Rick Slayman recovered in March from the first-ever transplant of a genetically modified pig kidney into a human, the revolutionary procedure was making headlines around the world. Meanwhile, Slayman’s doctors at Massachusetts General Hospital relayed daily updates on his condition to scientists at Eledon Pharmaceuticals, a Burlington technology company about fifteen miles northwest.

Though Slayman would pass away two months later, the transplant has been hailed as a breakthrough, and Eledon, a biotech company founded in 2020 by Steven Perrin ’88, had an important role in it. The company developed tegoprubart, a drug that formed part of the cocktail of immunosuppressive medications given to Slayman to prevent his body from rejecting the new kidney. (Mass General has said there is no indication that Slayman’s death was related to the transplant.) Tegoprubart, which is in human clinical development and has not yet been approved by the US Food and Drug Administration, was made available to Slayman through the agency’s “compassionate use” program, in which patients with serious conditions gain access to such medical products. Slayman had end-stage kidney disease and was ineligible for a traditional kidney transplant.

Photo of Steve Perrin '88

Steve Perrin Photo: Courtesy of Eledon

Administered via intravenous infusion, tegoprubart is what’s known as an investigational antibody. It works by blocking communication between cells that could cause the immune system to reject the transplanted organ. “I don’t think that transplant could have happened and functioned without our drug,” said Perrin, Eledon’s president and chief scientific officer. “Everything had to come together.”

The drug can be used both in animal-to-human organ transplants—a process known as xenotransplantation—and in human-to-human transplants. 

Xenotransplantation might become more common. Some one hundred thousand Americans are awaiting a kidney transplant, with the average wait around three to five years. Once a patient does receive a kidney transplant, the organ usually lasts about a decade before another one is required and the process begins again. When it comes to kidneys for transplant, there is “an incredible unmet need,” Perrin said.

That’s where doctors and scientists think xenotransplantation, specifically genetically modified pig kidney transplants like the one Slayman received, can help. Pig kidneys are similar in size to human ones, and can perform all the essential functions of a normal human kidney. Scientists at the Cambridge-based biotechnology company eGenesis, which provided the kidney, use CRISPR gene editing—removing certain pig genes and adding some human genes—to increase the pigs’ organ compatibility with their human recipients.

Still, successful xenotransplantation requires a careful immunosuppressive regimen to prevent organ rejection, Perrin said. “You’re taking this huge piece of tissue from somebody else and putting it into the body,” he said. “The immune system goes absolutely crazy recognizing that’s not you and wants to kill it.” Research over the past decade indicated that the best way to prevent rejection of a pig kidney by a human recipient, Perrin said, was to target CD40 ligand, a protein that is expressed on immune cells and can create an inflammatory response to a foreign presence in the body. Tegoprubart blocks CD40 ligand, he said, creating a more hospitable environment for the new kidney.

Perrin developed his love for medical research as a pre-med biology major at BC, then earned his PhD in biochemistry at Boston University. “It became really apparent to me that what I was passionate about was wanting to develop drugs,” he said. “I jumped early in my career into the biotech space here.” He never found a reason to leave the Boston area. “Every time I wanted a new opportunity,” he said, “I would just pack up my office in a cardboard box and walk two blocks to my next job.”

Tegoprubart, Eledon’s lead drug, is being studied in a Phase 2 clinical trial projected to include more than one hundred human-to-human kidney transplants. Perrin said he expects the clinical trial will prove not only that tegoprubart has fewer side effects than the current standard of care, a drug that was approved in 1994, but that it also promotes superior kidney function. Data from the trial is expected in early 2026.

"We want to see this through in transplant,” he said. “We have incredible conviction and passion in the company that we are going to transform the immunosuppressive part of transplant rejection for the first time in thirty years.” ◽