The Sanfilippo Children’s Foundation has awarded funds to Dr. Maria Francisca Coutinho from Dr. Sandra Alves’ lab on Lysosomal Storage Diseases at the National Institute of Health Dr. Ricardo Jorge (INSA) in Portugal. The study will involve developing nanoparticles to deliver substrate reduction drugs to the brain.

Sanfilippo Syndrome results when an enzyme dedicated to the breakdown of a complex sugar molecule called heparan sulfate is faulty. Heparan sulfate then accumulates within the body, resulting in devastating effects especially in the brains of children with Sanfilippo.

A number of approaches are under investigation to develop therapies for the disease, and one of these is Substrate Reduction Therapy (SRT). In Sanfilippo, SRT aims to decrease the production of heparan sulfate so that there is less to build up inside the body. It is hoped that this will improve symptoms and slow disease progression.

One type of potential SRT for Sanfilippo utilises small molecules called small interfering RNA (siRNA). siRNAs are not your traditional drug; they are short pieces of genetic information that switch off or silence genes. For Sanfilippo the siRNA’s would be designed to switch off genes involved in the production of heparan sulfate, and thus help to prevent it’s accumulation. Dr Coutinho’s research has already developed siRNA’s that show potential for Sanfilippo.

While siRNA agents appear as promising therapeutics in a variety of diseases, there are known issues associated with their use: they can be unstable, and it is difficult to deliver them inside cells where they need to work. Before siRNA is considered as a viable treatment option in Sanfilippo, these issues must be addressed.

In this study, Dr. Coutinho and her colleagues will focus on the development of delivery vehicles to get siRNA into cells. These delivery vehicles, called nanoparticles, are essentially miniscule droplets of fat that will enclose the siRNAs, protecting them from degradation. Furthermore, they will be engineered to cross the blood-brain barrier to get them to the brain where they are needed most.

Nanoparticle containing siRNA

The team will make, characterise and compare different nanoparticles to determine which could be the most effective. They will then test the nanoparticles containing the siRNAs on human brain cells in the lab.

Ultimately, the results of this study could benefit not only children with Sanfilippo but also those with other similar conditions. Furthermore, it will help to advance the research landscape as a whole with regards to delivering siRNA into cells.

“This study will help to investigate new approaches to treatment delivery, with an emphasis on drug delivery to the brain. This represents an important step in the drug development process for Sanfilippo”, said Megan Donnell, Founder of Sanfilippo Children’s Foundation.

Project Update 

Dr Maria Francisca Coutinho and her colleagues have completed their Incubator grant awarded in 2019 from the Sanfilippo Children’s Foundation. In this project, the team aimed to develop a substrate reduction therapy that works by silencing the genes in the body that make heparan sulfate. They aimed to use nanoparticles to deliver the therapy to the brain.

Although their original gene-silencing approach used ‘small interfering RNA’ (siRNA), they widened their study design to include two other gene-silencing approaches that do not require nanoparticles for delivery. The team used these gene-silencing approaches to target two different genes that produce the enzymes that are involved in making heparan sulfate. They identified one gene in particular that produced the best result regardless of the gene-silencing approach used. Their preliminary results on gene-silencing approaches that do not require carriers are so promising that the team didn’t pursue the nanoparticle work in this project. 

Instead, they focused their efforts on developing a new cell model for testing their gene-silencing drug candidates. The cell model was developed from stem cells found in the dental pulp inside baby teeth after they fall out. Parents of children with Sanfilippo and other MPS with neurological symptoms, as well as parents of unaffected children, sent in baby teeth from around the world. The team extracted the stem cells from inside the baby teeth in the lab and re-programmed them into neurons. The team thoroughly examined the new cell model and confirmed low enzyme levels and heparan sulfate build-up in the cells from affected children, as seen in patients. 

With support from two grants received from the Portuguese government, the team will now continue to use the new cell models to test their lead drug candidates, which are being developed and evaluated under the scope of the grant won by their group leader, Dr Sandra Alves. 

Dr Coutinho, Dr Alves and their colleagues also published three review papers and presented their early findings at multiple conferences and scientific meetings. They are currently working on a manuscript for publication in a scientific journal to share their findings with other researchers in the field. 

As substrate reduction therapy helps to reduce heparan sulfate production, the technique has application not only for Sanfilippo but also for other similar diseases, including Hunter and Hurler syndromes.

Dr. Maria Francisca Coutinho is a geneticist who has been studying lysosomal storage diseases, including Sanfilippo, for over 10 years, and has particular interest in the development of Substrate Reduction Therapies for these diseases.

Project Summary

• Project title: Genetic Substrate Reduction Therapy for MPS III: Toward a siRNA-containing nanoparticle targeted to brain cells
• Chief investigator: Dr. Maria Francisca Coutinho
• Amount: $25,000
• Duration: 1 year
• Location: National Institute of Health Dr. Ricardo Jorge (INSA), Portugal
• Status: Completed
• Start date: January 2020 

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