Key inclusion criteria:

   - Patients ≥ 18 years of age who provided written informed consent, Eastern Cooperative
   Oncology Group (ECOG) performance status of 0-3 and a life expectancy of >12 weeks,
   electrocardiogram with a QTcF of ≤ 450 ms, with a diagnosis of SM and sub-variants
   based on WHO criteria.

   - Patients with ASM or MCL were to have one or more measurable clinical findings (termed
   "C-findings") and defined as those attributable to the mast cell disease component and
   not to AHNMD or any other cause.

   - Patients with MCL were to have BM aspirate smears with ≥ 20% immature MCs. Patients
   with AHNMD were eligible if it was not life-threatening or in an acute stage.

Key exclusion criteria:

   - Patients with cardiovascular disease including congestive heart failure class III or
   IV according to the New York Heart Association classification, left ventricular
   ejection fraction (LVEF) of <50%, myocardial infarction within the previous 6 months,
   or poorly controlled hypertension.

   - Patients with a heart block of any degree at screening (for Canada only).

   - Patients with an AHNMD who required immediate cytoreductive therapy or targeted
   therapy (other than midostaurin).

   - Patients who had demonstrated relapse after 3 or more prior regimens of SM treatment
   regardless of treatment regimen for supportive care (e.g., symptom-limiting
   therapies).

   - Patients who had received any investigational agent, targeted therapy, chemotherapy,
   interferon-α, or 2 chlorodeoxyadenosine within 30 days prior to start of midostaurin
   treatment.

   - Patients who had ASM with eosinophilia and known positivity for the FIP1L1- PDGFRα
   fusion unless they had demonstrated relapse or disease progression on prior imatinib
   therapy.

   - Patients who had received any treatment with midostaurin prior to study entry.

   - Patients who had received hematopoietic growth factor support within 14 days of Day 1
   of midostaurin treatment.

   - Patients who had any surgical procedure, excluding central venous catheter placement
   or other minor procedures (e.g. skin biopsy) within 14 days of Day 1 of midostaurin
   treatment.

   - Patients with any pulmonary infiltrate, including those suspected to be of infectious
   origin. In particular, patients with resolution of clinical symptoms of pulmonary
   infection but with residual pulmonary infiltrates on chest x-ray were not eligible
   until the pulmonary infiltrates had completely resolved. Exception: patients with
   ASM/MCL ± AHNMD-related pleural effusion as judged by the Investigator and approved by
   the SSC Chairperson or designee were permitted to enter the study.