Denmark-based LEO Pharma is developing a high-payload herpes simplex virus (HSV) gene therapy to treat a rare genetic skin disorder in children [1].
The development represents a potential shift in pediatric care by offering a non-injection treatment option for a condition that currently has an unmet medical need [2].
This initiative is led by scientist Suma Krishnan, who is in her late 40s [2]. Krishnan heads the Replay gene-therapy platform, which LEO Pharma acquired in 2025 [1]. The platform focuses on creating therapies capable of carrying larger genetic payloads than traditional methods, a necessity for treating certain complex genetic disorders.
The research teams are operating across the U.S. and Denmark to refine the HSV-based delivery system [1, 2]. By leveraging the Replay platform, the company aims to deliver functional genes directly to the skin cells of affected children. This approach is designed to address the root cause of the genetic disorder rather than managing symptoms through topical or systemic medications.
The acquisition of the Replay platform in 2025 allows LEO Pharma to integrate advanced gene-editing and delivery technologies into its existing dermatology portfolio [1]. The focus remains on the specific challenges of pediatric skin diseases, where traditional delivery methods can be invasive or ineffective.
Krishnan has been recognized as one of the greatest innovators in the U.S. for her work on this breakthrough therapy [2]. The project continues to move through development stages to determine the efficacy and safety of the high-payload delivery system in human subjects.
“A high-payload HSV gene therapy is being positioned as a breakthrough treatment for children.”
The move toward high-payload viral vectors like HSV addresses a primary limitation in gene therapy: the size of the genetic material that can be delivered to a cell. By overcoming this 'cargo' limit, LEO Pharma can target larger genes associated with rare skin disorders that were previously untreatable, potentially establishing a new standard for non-invasive pediatric genetic medicine.
