In Colorado and Wyoming, nearly every baby born since 2020 is tested for signs of a mutation in the SMN1 gene, an indicator of spinal muscular atrophy (SMA). And in 4 years, genetic counselor Melissa Gibbons has seen 24 positive results. She has prepped 24 different pediatricians and family doctors to deliver the news: A seemingly perfect newborn likely has a lethal genetic disease.
Most of these clinicians had never cared for a child with SMA before, nor did they know that lifesaving gene therapy for the condition now exists. Still, the physicians were foundational to getting babies emergency treatment and monitoring the child’s safety after the fact.
“They are boots on the ground for this kind of [work],” Ms. Gibbons, who is the newborn screen coordinator for SMA in both states, told this news organization. “I’m not even sure they realize it.” As of today, the U.S. Food and Drug Administration has approved 16 gene therapies for the treatment of rare and debilitating diseases once considered lethal, such as SMA and cerebral adrenoleukodystrophy.
The newest addition to the list of approvals is Elevidys, Sarepta’s gene therapy for Duchenne muscular dystrophy (DMD). These conditions can now be mitigated, abated for years at a time, and even cured using treatments that tweak a patient’s DNA or RNA.
Hundreds of treatments are under development using the same mechanism. Viruses, liposomes, and other vectors of all kinds are being used to usher new genes into cells, correcting faulty copies or equipping a cell to fight disease. Cells gain the ability to make lifesaving proteins – proteins that heal wounds, restore muscle function, and fight cancer.
Within the decade, a significant fraction of the pediatric population will have gone through gene therapy, experts told this news organization. And primary care stands to be a linchpin in the scale-up of this kind of precision genetic medicine. Pediatricians and general practitioners will be central to finding and monitoring the patients that need these treatments. But the time and support doctors will need to fill that role remain scarce.
“This is a world we are creating right now, quite literally,” said Stanley Nelson, MD, director of the center for Duchenne muscular dystrophy at the University of California, Los Angeles. These cases – some before gene therapy and some after – will show up in primary care offices before the textbook is written.
Unknown side effects, new diseases
Even now, gene therapy is sequestered away in large academic medical research centers. The diagnosis, decision-making, and aftercare are handled by subspecialists working on clinical trials. While the research is ongoing, trial sponsors are keeping a close eye on enrolled patients. But that’s only until these drugs get market approval, Phil Beales, MD, chief medical officer at Congenica, a digital health company specializing in genome analysis support, said. Afterward, “the trialists will no longer have a role in looking after those patients.”
At that point, the role of primary care clinicians will be critically important. Although they probably will not manage gene-therapy patients on their own – comanaging them instead with subspecialists – they will be involved in the ordering and monitoring of safety labs and other tests.
General practitioners “need to know side effects because they are going to deal with side effects when someone calls them in the middle of the night,” said Dr. Beales, who also is chief executive officer of Axovia Therapeutics, a biotech company developing gene therapies.
Some of the side effects that come with gene therapy are established. Adeno-associated virus (AAV) or AAV-mediated gene therapies carry an increased risk for damage to the heart and liver, Dr. Nelson said. Other side effects are less well known and could be specific to the treatment and the tissue it targets. Primary care will be critical in detecting these unexpected side effects and expediting visits with subspecialists, he said.
In rural Wyoming, pediatricians and family doctors are especially important, Ms. Gibbons said. In the 30-90 days after gene therapy, patients need a lot of follow-up for safety reasons.
But aftercare for gene therapy will be more than just monitoring and managing side effects. The diseases themselves will change. Patients will be living with conditions that once were lethal.
In some cases, gene therapy may largely eliminate the disease. The data suggest that thalassemia, for example, can be largely cured for decades with one infusion of a patient’s genetically modified hematopoietic stem cells made using bluebird bio’s Zynteglo, according to Christy Duncan, MD, medical director of clinical research at the gene therapy program at Boston Children’s Hospital.
But other gene therapies, like the one for DMD, will offer a “spectrum of benefits,” Dr. Nelson said. They will be lifesaving, but the signs of the disease will linger. Clinicians will be learning alongside specialists what the new disease state for DMD and other rare diseases looks like after gene therapy.
“As we get hundreds of such therapies, [post–gene therapy] will amount to a substantial part of the pediatric population,” Dr. Nelson said.