Curt Krouse, seated, with his parents and younger son, Ryan, receives the first gene therapy for hemophilia B.
“Someday, there will be a cure!” For decades, ever since Curt Krouse was a young child with hemophilia B, those hopeful words rang out at the end of an annual fashion show that his mother, Sandy, co-hosted as part of a hard-working committee to benefit the local bleeding disorders foundation.
In October 2024, that day finally came. Krouse, now 57—with his parents by his side—was the first Penn Medicine patient to receive a new gene therapy for hemophilia B since it was approved by the FDA. It was the first FDA-approved gene therapy for the condition in adults.
“I’m not an emotional person, but I’m getting emotional,” Sandy Krouse said. “The thought that Curt won’t have to infuse anymore … and to know that children born with hemophilia will face a different kind of life ... it’s so exciting, not only for Curt, but for the whole hemophilia community.”
Decades with a disease, then life changes in 30 minutes
Curt Krouse with his two sons at a Philadelphia Eagles game, the Sunday after he received the first gene therapy for hemophilia B
Like other adults with the disorder, Krouse has a genetic mutation that makes the blood-clotting factor 9 gene nonfunctional. Through a one-time infusion, the new drug, Hemgenix, uses a harmless virus to deliver a working copy of the factor 9 gene into the liver, which then begins manufacturing the clotting factor to prevent bleeding.
When Hemgenix was approved by the Food and Drug Administration in November 2022, scientists had been working for decades to find a gene therapy to cure hemophilia. Immediately after the infusion, Krouse stopped regular prophylactic clotting factor injections.
“Living with this disease for 57 years, and then my life changes in 30 minutes. It’s hard to believe. I am grateful to have shared this experience with my family and medical team. The gene therapy injection was not just for me, but for everyone in my life that helped take care of me,” he said.
Throughout his lifetime, Krouse has seen the evolution of treatment for his severe hemophilia. As a baby, his parents would bring him to the hospital for treatment with clotting medication to stop bleeding. He, along with family members, then learned to administer at-home injections after bleeds. This meant regular prophylactic injections to maintain sufficient levels of the clotting factor to prevent bleeding.
Even with preventive injections, bleeds—both internal and external—were still possible. He wears ankle braces to control the pain from arthritis that developed after decades of internal bleeding into joints—a common problem in patients with severe hemophilia. Before the new therapy, he had to travel with extra clotting factors, packed on ice, when he was any significant distance from home, as well as be aware of the nearest hemophilia treatment center in case of a bleed.
The lightness of a ‘hemophilia-free mind’
Members of the Pharmacy team hand off the gene therapy for hemophilia B to nurse Carly Solipaca for the first infusion of a Penn Medicine patient outside of a clinical trial.
Then there was the emotional toll of always taking precautions to be careful, and even if he did, knowing that spontaneous bleeding incidents were possible.
“It’s not only physically a huge burden—it’s also a huge burden mentally,” Krouse said. “A lot of times that’s overlooked, but you are always thinking about your disease. You must take care of yourself. It is front and center in your mind.”
Adam Cuker, MD, MS, director of the Penn Comprehensive Hemophilia and Thrombosis Program and Krouse’s doctor, said he hoped that in time, Krouse would learn to release those fears.
“There’s a new concept that has come with gene therapy called the ‘hemophilia-free mind.’ When you have hemophilia, even when it’s well-managed, there’s still a mental burden: the fear of bleeding, the burden of needing to do frequent IV infusions, all the hassles with insurance, the fear that your product might not be covered,” Cuker said. “You can imagine how mentally straining that is. For the first time, this is a treatment that offers an opportunity to lift that.”
Curt Krouse, seated, with Adam Cuker, MD, MS, director of the Penn Comprehensive Hemophilia and Thrombosis Program.
Twelve weeks after the gene therapy infusion, Cuker reported that Krouse had experienced an “amazing response.” While Cuker cautioned that such a positive response to the therapy is not guaranteed, Krouse’s factor 9 level had risen from less than one percent of normal to normal; he had not had any bleeds nor required any factor infusions to prevent bleeds; and he had experienced no side effects.
As a young child, Krouse asked his parents not to baby him and assured them he knew his limitations. The greatest of those was not playing sports—it felt too risky—and free of those worries, Krouse said he looks forward to exercising and becoming more active.
“It is hard to explain the feeling. I bang my arm or scratch my leg and instead of infusing, I just watch the affected area clot normally,” Krouse said. “It’s like a science fiction movie, but it’s real.”
Gene therapy innovations at Penn Medicine
Just a handful of gene therapies have been approved for any diseases, including a second gene therapy for hemophilia B, called BEQVEZ, that was approved in April 2024, based on a study led by Cuker and others, and the first gene therapy ever approved by the FDA, also developed at Penn Medicine, for a form of inherited blindness. Penn Medicine offers access to numerous clinical trials for gene therapy as well as expertise in administering the existing FDA-approved therapies.