Retrospective Study Assessing the Effect of Avapritinib Versus Best Available Therapy in Patients With AdvSM

Inclusion Criteria for Patients in the External Control Arm:

1. Diagnosed with AdvSM, with known subtype including SM-AHN, ASM, or MCL

2. Received at least one line of systemic therapy for AdvSM, which may include but not
limited to regimens containing:

Midostaurin Cytoreductive therapy: cladribine, interferon alpha, azacitidine,
decitabine Selective TKIs: imatinib, nilotinib, dasatinib Hydroxyurea Antibody
therapy: brentuximab vedotin

3. Adult (≥18 years of age) at the initiation of first systemic line of therapy at the
participating site

4. Had an index date at least 3 months prior to the start of data collection (in order to
include patients with at least 3 months of follow-up after index date), unless date of
death occurred less than three months from index date

5. Had an approved waiver of informed consent or signed informed consent for
participation in the retrospective chart review study, if no institutional waiver from
the site was granted

Exclusion Criteria for Patients in the External Control Arm

1. Malignancy that is not in remission at time of SM diagnosis, or new non-hematological
malignancy diagnosed after SM diagnosis, except for: completely resected basal cell
and squamous cell skin cancer, curatively treated localized prostate cancer, and
completely resected carcinoma in situ of any site

2. Among patients with SM-AHN, presence of either of the following:

- Patients in whom the SM component is consistent with an indolent systemic
mastocytosis (ISM) or SSM or,

- the AHN component is a lymphoid malignancy, or one of the following myeloid
malignancies: acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) that
is very high-or high-risk as defined by the IPSS-R, or a Philadelphia chromosome
positive malignancy or,

- there is a known FIP1L1/PDGFRA fusion gene (including those with CHIC-2 deletion
and partial deletion of PDGFRA), independent of KIT mutational status

3. Received avapritinib as the first line of systemic therapy for AdvSM at participating
site, or prior to initiation of first systemic therapy at participating site.