Continuation Study of Avapritinib in Adult Patients with Systemic Mastocytosis Previously Enrolled in Avapritinib Clinical Trials

The primary objective of this study is to provide continued access to **avapritinib** for patients with Systemic Mastocytosis who have participated in a Blueprint Medicines sponsored study and continue to derive clinical benefit from the treatment, as assessed by the Investigator. This is clinically relevant as it ensures ongoing therapeutic support for patients until the commercial availability of avapritinib, potentially improving patient outcomes and quality of life.

The secondary objective is to evaluate the long-term safety of avapritinib. This assessment is crucial for understanding the extended safety profile of the drug, which can inform future treatment protocols and patient management strategies.

The clinical trial involves a total of **34 participants** diagnosed with **Systemic Mastocytosis**. The study population includes both male and female subjects, with an age range of 18 to 65 years. Participants were selected based on their prior involvement in a Blueprint Medicines sponsored avapritinib clinical study, where they demonstrated compliance with study requirements and continued clinical benefit from the treatment. The trial includes a vulnerable population, indicating that special considerations are in place to protect these participants. Lifestyle factors such as diet and physical activity are not specified, but participants are required to use highly effective contraception. Female participants of childbearing potential must have a negative pregnancy test before receiving the study treatment. The trial aims to provide continued access to avapritinib until its commercial availability for those who benefit from the treatment, as assessed by the Investigator.

The clinical trial is designed as an **open-label**, multicenter, rollover study aimed at providing continued access to **avapritinib** for patients with **systemic mastocytosis** who have previously participated in a Blueprint Medicines sponsored study. The trial will continue until the commercial availability of avapritinib, with an estimated end date of December 31, 2027. The study will not have primary or secondary endpoints, as its main objective is to ensure ongoing treatment for patients who continue to benefit from avapritinib, as determined by the investigator.

Participants eligible for this study must have completed the end-of-treatment or end-of-study visit in the parent study and demonstrated compliance with its requirements. They must also continue to clinically benefit from avapritinib treatment. The study involves oral administration of avapritinib in the form of film-coated tablets. The maximum treatment period is set at 39 weeks, with the possibility of early termination if the participant no longer benefits from the treatment or if the investigator deems it necessary.

The sequence of study visits includes an initial screening visit to confirm eligibility, followed by regular follow-up visits to monitor the patient's condition and response to treatment. The end-of-study visit will conclude the participant's involvement in the trial. Participants are expected to remain in the study for the duration of the treatment period unless they meet criteria for early withdrawal, such as adverse effects or lack of clinical benefit. The trial is categorized as a Phase 4 study, focusing on long-term safety and tolerability data collection.

The clinical trial involves the administration of **Avapritinib**, a chemical compound developed by Blueprint Medicines. Avapritinib is provided in the form of a **film-coated tablet**. The active substance in this medication is avapritinib, which is chemically synthesized. The pharmaceutical form is designed for **oral use**. The trial does not specify a maximum daily dose or total dose amount, indicating that dosing may be adjusted based on individual patient needs and clinical judgment. The maximum treatment period for participants is set at 39 weeks. The medication is identified by the sponsor product code BLU-285 and is not formulated for pediatric use.

In this study, no non-experimental treatments such as standard-of-care therapy, placebo, or comparator treatments are mentioned. The focus is solely on providing continued access to avapritinib for patients who have previously participated in a Blueprint Medicines-sponsored study and continue to benefit clinically from the treatment. Participant compliance with the dosing schedule will be monitored throughout the trial to ensure adherence to the treatment regimen. The study aims to maintain the therapeutic benefits of avapritinib until it becomes commercially available.

The clinical trial aims to provide continued access to **avapritinib** for patients who have participated in a Blueprint Medicines sponsored study and continue to benefit from the treatment. The study is designed as an open-label, multicenter, rollover study. The primary objective is to ensure the availability of avapritinib until its commercial availability, while also collecting long-term safety and tolerability data. The trial does not specify primary or secondary efficacy endpoints, as its main focus is on providing access to the medication and monitoring safety.