This clinical trial is focused on studying a condition called Indolent Systemic Mastocytosis (ISM), which is a type of disease where certain cells in the body, known as mast cells, grow uncontrollably and cause various symptoms. The trial is testing a medication called Avapritinib, which is a type of drug known as a tyrosine kinase inhibitor. This medication is designed to target specific mutations in the KIT gene that are often found in patients with ISM. The study also involves the use of a placebo, which is a substance with no active medication, to compare the effects of Avapritinib.
The purpose of the study is to evaluate the safety and effectiveness of Avapritinib in patients with ISM whose symptoms are not adequately controlled with standard treatments. The study is divided into three parts. In the first part, the appropriate dose of Avapritinib will be determined. The second part will compare the change in symptoms from the start of the study to a specific point in time between those taking Avapritinib and those taking a placebo. The third part will assess the long-term safety and effectiveness of Avapritinib in these patients.
Participants in the study will take Avapritinib in the form of film-coated tablets, which are taken orally. The study will monitor changes in symptoms, the burden of mast cells in the body, and the overall quality of life of the participants. Safety will be closely monitored through regular assessments, including checking vital signs, conducting electrocardiograms (ECGs), and performing laboratory tests. The study aims to provide valuable information on how well Avapritinib works in managing ISM and its long-term safety for patients.



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