Actigen leads potential breakthrough in Hunter syndrome treatment

Actigen has initiated a clinical development programme for GNR-055, a potentially breakthrough treatment for the life-limiting, rare disease mucopolysaccharidosis II (MPS II) (also known as Hunter syndrome). Occurring in around one in 100,0000–170,000 births, MPS II presents almost exclusively in males and has a major impact on the physical and neurological health of those affected.


MPS II is one of more than 6,000 rare diseases affecting approximately 300 million people worldwide. Like many other orphan diseases, MPS II has limited treatment options due to a prior absence of resources needed to investigate the disease.

Actigen’s work

Actigen’s work focuses on identifying and developing biological medicines for human diseases with unmet medical needs. Actigen’s forthcoming clinical trial with GNR-055 presents an opportunity to find a more comprehensive treatment option for MPS II, which could significantly improve patient’s physical and cognitive functions, and enhance their quality of life.


This rare, debilitating disease is caused by a deficiency of the key enzyme responsible for breaking down sulfated sugar molecules called glycosaminoglycans (GAGs) in cells throughout the body.1,2 If left untreated, this leads to a progressive deterioration of organ systems across the body, including the heart, lungs, brains, bone and cartilage.1,2,3 Brain deterioration leads to cognitive and behavioural issues such as disturbed sleep, hyperactivity, poor concentration, disruptive behaviour and poor temper control.1,2,4,5

The current treatment options available, such as enzyme replacement therapy, only offer a partial solution. While they can help improve the functioning of internal organs and improve patients’ quality of life, their inability to cross the blood-brain barrier means that GAGs continue to build up in the brain, resulting in ongoing neurological issues.6

GNR-055 uses an innovative combination of the missing enzyme and an antibody fragment to access brain cells. The antibody has a particularly important function binding to the human insulin receptor on capillary cells to cross the brain-blood barrier. Once in the brain, GNR-055 is expected to break down the GAGs that cause the neurological issues. This novel treatment fulfils an unmet clinical need and could offer life-changing improvements for patients affected by MPS II.

Official comments

Actigen’s Managing Director, Michael Braunagel, said: “MPS II is just one of thousands of rare diseases that have lacked clinical awareness, resources and treatment options. At Actigen, it is our mission to improve the lives of individuals with rare diseases, and we hope that GNR-055 will be the start of many more trials. We are establishing an exciting approach to clinical trials with GNR-055 and are working with our partner to bring products to global markets. MPS II is a very debilitating condition for those affected and we are hopeful that the trial will establish the treatment’s efficacy. GNR-055 is the first therapeutic in our innovative development pipeline, and we are thrilled to be working on such an important treatment.”


  1. Da Silva et al. 2014
  2. NIHR Horizon Scanning Research & Intelligence Centre
  3. Cimaz and La Torre, 2014
  4. Mayo Clinic
  5. Hampe et al. 2021
  6. Boado et al 2014

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