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Safety of sirolimus in children under 2 years of age

About this study

In the last decade, the two mTOR inhibitor treatments everolimus and sirolimus have proven effective in reducing tumour size and improving seizure control for many people living with TSC. However, there is limited research on the use of mTOR inhibitors in very young children. The purpose of this study was to investigate the safety of sirolimus in children with TSC below the age of 2 years.

How the study was conducted

Researchers conducted a retrospective analysis of medical records from 21 young children with TSC under 2 years of age, who were treated with sirolimus. The study was conducted at two clinical centres in Poland that specialise in child neurology.

Outcomes of the study

The study found that all the children had at least one side effect from the medication. The most common side effects were anaemia, high platelet count, and high cholesterol. However, infections and mouth ulcers, which are common in older patients, were not as common in these younger children. The study concluded that adverse effects associated with sirolimus use in infants and young children with TSC are frequent but not life- or health-threatening.

Out of 21 patients, 18 (about 86%) continued taking their medication until the end of the study. None of the patients stopped taking their medication because of side effects.

Limitations of the study

This study has some limitations. The sample size was small, and the study was retrospective, meaning it looked back at past medical records. Additionally, the study did not examine the long-term safety of sirolimus. 

Implications of the study

In other studies, both everolimus and sirolimus caused low-grade side effects in children. This study is the first to report the side effects of sirolimus in children under two years of age. The study suggests that sirolimus is generally safe for young children with TSC. Although the side effects observed were not severe and did not require discontinuation of treatment, further research is necessary to understand the long-term safety of sirolimus. Future multicentre prospective clinical trials are needed.

Śmiałek, D., Jóźwiak, S., & Kotulska, K. (2023). Safety of Sirolimus in Patients with Tuberous Sclerosis Complex under Two Years of Age—A Bicenter Retrospective Study. Journal of Clinical Medicine, 12(1), Article 1.

Full article available at:

TSC-STEPS – a pioneering research study in Australia

In an exciting development, the team at the TSC Clinic at Sydney Children’s Hospital in Randwick, NSW is participating in a multicentre prospective clinical trial – TSC STEPS.  The TSC-STEPS study aims to investigate the safety and effectiveness of early sirolimus treatment in delaying or preventing seizures in infants diagnosed with TSC.

There is no financial compensation for participation, but TSA is able to provide some travel funding for those who need it, including for people outside of NSW.

If your baby is between 0 to 6 months old, is diagnosed with TSC, and has no history of seizures, they may be eligible to participate.

For more information, please:

visit (identifier NCT05104983)

contact Dr Denise Chan at [email protected] or (+61) 2 9382 5523.


This information is intended to provide some insights into recent TSC-related research.  It is not intended to, and it should not, constitute medical or other advice.  Readers are warned not to take any action without first seeking medical advice.