Duke/UNC Collaborations Score Big Wins for Biomedical Research

Pilot funding catalyzes progress on gene editing tools and algorithms to better predict pediatric drug safety

Thoughts of Duke and UNC-Chapel Hill often bring to mind the famous and longstanding rivalry between the two schools in the sports arena. But when biomedical researchers from the two campuses team up to turn basic scientific discoveries into advances with real potential to improve patient care, everyone wins.

That’s made clear by the rapid progress of two Duke/UNC research teams funded by a collaborative funding program started in 2015 by the Clinical and Translational Science Institutes at Duke and UNC-Chapel Hill. In its first year, the Duke/UNC Collaborative Funding program offered $50,000 to each of four teams, with each team having principal investigators from opposite ends of Tobacco Road.

Duke’s Charles Gersbach, PhD, and UNC’s Aravind Asokan lead one of those first four CTSA-funded Duke/UNC teams. They used the $50,000 to work together on a novel method to beat Duchenne muscular dystrophy using cutting edge gene-editing tools.

Despite the newness of the partnership, progress has been rapid because of the natural fit of the two investigators’ research interests.

Gersbach had been working for years to apply a tool known as CRISPR/Cas9 to edit disease-causing mutations out of the genome. His focus was on correcting the dystrophin mutation that causes Duchenne muscular dystrophy, a disorder characterized by progressive muscle degeneration and weakness in children. Gersbach had shown his approach worked in isolated patient cells cultured in lab dishes. He believed it had real potential to help patients, but he needed to find a way to safely deliver the CRISPR/Cas9 system precisely where it is needed -- in the muscles of living animals carrying the disease mutation.

That’s where Asokan came in. He had been developing and studying viral vectors for use in gene therapy approaches in which the goal isn’t to correct disease genes but to override them by inserting extra, healthy gene copies. Asokan had pioneered an approach to safely deliver genetic cargo to specific tissues, including muscle, with the help of specially engineered adeno-associated viruses or AAVs.

Gersbach and Asokan had attended each other’s presentations at conferences over the years and knew of each other’s work. The CTSA funding was just the catalyst they needed to join forces and find out where it could lead.

Finding Success

Within a year of the announcement of their CTSA award in January 2015, Gersbach and Asokan successfully demonstrated use of AAVs to deliver CRISPR/Cas9 gene-editing tools in mice with Duchenne muscular dystrophy. When injected into the bloodstream of a mouse, their CRISPR/AAV combination successfully corrected muscles throughout the body, including in the heart. That’s important because heart failure is a frequent cause of death for patients with Duchenne muscular dystrophy. The findings—which marked one of the first times that CRISPR/Cas9 had been successfully used to treat a genetic disease in an adult mammal—were featured online in the prestigious journal Science on New Year’s Eve, 2015. The advance made headlines in major news outlets around the world.

Gersbach and Asokan’s early CTSA-funded work also helped them land additional research funding from the National Institutes of Health (NIH).

With this additional funding, they are optimizing the approach and working to better understand its safety. While they’re beginning to think about what a clinical trial in patients might look like, for now they plan to test the CRISPR/AAV system in humanized mouse models and then, via additional collaborations, in larger animals whose muscles are more similar to human muscles. They also plan to test next-generation viral vectors produced in Asokan’s lab, which are designed to target muscle even more precisely.

“We are very confident this approach has the potential to prevent disease progression,” Gersbach said. “The key is to better understand safety and how it works in larger muscles. If we can make it safe in large enough doses, we should be able to prevent or slow the course of disease.”

Protecting Preemies

The CTSA-funding has also sparked a successful, ongoing collaboration between Daniel Gonzalez, PharmD, PhD, an assistant professor in the UNC Eshelman School of Pharmacy, and Christoph Hornik, MD, MPH, an assistant professor in the Duke School of Medicine. They are addressing an important gap in the understanding of potential harms associated with certain medications in premature babies.

Clinical trials in preemies are notoriously difficult to conduct. Those that succeed tend to include only small numbers of patients. Because of the lack of evidence from clinical trials done in preemies, physicians often treat these fragile patients with medications based on testing done in older children and/or adults. These studies generally include very little, if any, evidence about the safety of the medication in infants.

The CTSA Collaborative funding gave Hornik and Gonzalez a chance to change that by gathering evidence from different sources. Using Hornik’s expertise in drug use and outcomes research in pediatric populations, and Gonzalez’s knowledge of clinical pharmacology and pharmacokinetics in children, they developed a method that combines clinical data from small studies of premature infants with large stores of data from electronic medical records. These medical records represent thousands of young patients, drug doses, and their relationships to positive outcomes and/or adverse events.

The pair tested their approach first on sildenafil. Physicians commonly give this drug to premature infants to treat pulmonary hypertension, a type of high blood pressure that affects arteries of the heart and lungs. But babies given sildenafil sometimes suffer complications related to low blood pressure. Hornik and Gonzalez wanted to know whether those complications could be linked to greater sildenafil exposures.

The evidence suggests that the answer is no. “We did not find an association between adverse events and the predicted drug exposure nor the dose of drug given,” Gonzalez said.

Hornik and Gonzalez say the findings suggest that there is no clear relationship between sildenafil exposure and blood pressure drop in infants.

However, the lack of correlation between sildenafil exposures and complications is a positive step for the research team.

“We think this approach is feasible,” Gonzalez said. “It shows we can use models to predict drug exposure and then relate it to safety or efficacy events in electronic medical records.”

In fact, they’ve already moved on to apply their approach to questions about the use of two antibiotic drugs and the incidence of seizures in young children. In contrast to the findings on sildenafil, one of those studies did suggest that children with higher concentrations of the antibiotic ampicillin in their blood are at greater risk of seizures.

Let’s Work Together

Before they heard about the CTSA program, Hornik and Gonzalez had some collaborators in common, but it was the pilot funding that brought them together. “This project bridged our skills. It was an important first step and we’ll continue to work together,” said Gonzalez.

Hornik recently submitted an NIH Career Development award, which will in part allow him to continue on this line of research. The team has multiple papers submitted and under review for publication in peer-reviewed journals and they continue to look for additional funding opportunities.

As for Gersbach and Asokan, they “haven’t been to a Duke-Carolina game together yet,” Asokan said with a laugh. All kidding aside, he says, “the CTSA funding has seeded collaboration. We’ll continue to build on that, and hopefully there will be much more to come.”