A Safety, Tolerability and PK Study of DCC-2618 in Patients With Advanced Malignancies

Inclusion Criteria (Escalation and Expansion Phases)

Patients must meet the following criteria to be eligible to enroll in the study:

1. Male or female patients ≥18 years of age.

2. Patients must have histologically confirmed solid tumors or hematologic malignancies.
Eligible patients include the following:

1. GIST patients must have a KIT and PDGFRA mutation and must have progressed on or
had an intolerability to at least 1 line of systemic anticancer therapy.

2. SM patients must have a confirmed diagnosis of advanced SM according to 2016
World Health Organization (WHO) criteria for SM and must have documented KIT
mutant disease.

Advanced SM includes: ASM, SM with associated hematologic neoplasm (SM-AHN), wherein
the AHN does not require immediate alternative therapy. AHNs that are eligible
include: low grade myelodysplastic syndrome (MDS) with a high SM burden who require
treatment for SM only, myeloproliferative neoplasms (MPN), MDS/MPN, and HES/CEL, and
MCL.

i. Patients with advanced SM must present with at least 1 eligible C-Finding (organ
damage) per 2013 International Working Group-Myeloproliferative Neoplasms Research and
Treatment (IWG-MRT) & European Competence Network on Mastocytosis consensus response
criteria.

ii. Patients with imatinib-sensitive KIT mutations must have progressed on or were
intolerant to a tyrosine kinase inhibitor.

iii. Patients with histopathologically-confirmed MCL without a C-finding are eligible.

iv. Patients with symptomatic smoldering systemic mastocytosis (SSM) are eligible.

v. Patients with hematologic malignancies featuring clonal expansion of eosinophils
driven by genomic alterations of KIT or PDGFRA (eg, HES or CEL) are eligible if they
have progressed on or are intolerant of imatinib therapy. Patients with de novo
imatinib resistant mutations, such as but not limited to KIT D816V or PDGFRA D842V,
are eligible without prior imatinib therapy.

c. Malignant glioma patients with genomic alterations potentially conferring
sensitivity to DCC-2618 including, but not limited to, amplification and/or mutations
of PDGFRA and/or KIT.

d. Other solid tumor patients that have alterations in genes encoding kinases that are
targets of DCC-2618. This includes:

- Melanoma

- Soft tissue sarcoma patients (including but not limited to: malignant peripheral
nerve sheath tumors (MPNST), desmoplastic small round cell tumors (DSRCT), and
dermatofibrosarcoma protuberans tumors (DFSP)

- Other solid tumor patients (non-melanoma, non-STS; specifically germ-cell,
penile, and non-small cell lung carcinoma)

- Renal impairment cohort

3. Eastern Cooperative Oncology Group (ECOG) performance status (PS) of ≤2.

4. Adequate organ function and bone marrow function.

Exclusion Criteria (Escalation and Expansion Phases)

Patients meeting any of the following criteria will be excluded from the study:

1. GIST patients with wild type or unknown KIT or PDGFRA status.

2. Patients with SM or other hematologic malignancies will be excluded if the following
apply:

1. SM patients with wild type KIT mutational status.

2. SM patients with neutropenia accompanied by fever or infection, or
thrombocytopenia associated with clinically significant bleeding.

• Patients with an infection that is well controlled with antibiotics are
eligible if there is an immediate need for treatment.

3. SM-AHN patients diagnosed with:

i. SM with MDS who require treatment for MDS. ii. Patients requiring immediate
treatment for AHN.

d. Patients with leukemias, with the exception of MCL and CEL, that have progressed
after imatinib.

e. Eosinophilic myeloproliferative neoplasm patients: i. Lacking a mutation that is a
known target of DCC-2618.

3. Has a known additional malignancy that is progressing or required active treatment
within 3 years of the first dose of study treatment. Exceptions include basal cell
carcinoma of the skin, squamous cell carcinoma of the skin that has undergone
potentially curative therapy, or other in situ cancers.

4. New York Heart Association class III and IV heart disease, active ischemia or any
other uncontrolled cardiac condition such as angina pectoris, clinically significant
cardiac arrhythmia requiring therapy, uncontrolled hypertension or congestive heart
failure.

5. Arterial thrombotic or embolic events such as cerebrovascular accident (including
ischemic attacks) or hemoptysis within 6 months before start of study drug.

6. Venous thrombotic events (eg, deep vein thrombosis) or pulmonary arterial events (eg,
pulmonary embolism) within the 3 months before start of study drug. Patients with
venous thrombotic events ≥3 months before start of study drug on stable
anticoagulation therapy are eligible.

7. Baseline prolongation of the rate-corrected QT interval based on repeated
demonstration of QT interval corrected by Fridericia's formula (QTcF) >450 ms in males
or >470 ms in females or history of long QT interval corrected (QTc) syndrome.

8. Left ventricular ejection fraction (LVEF) <50% or below the lower limit of normal
(whichever is higher).

9. Major surgery within 4 weeks of the first dose of study drug; following major
surgeries >4 weeks prior to the first dose of study drug, all surgical wounds must be
healed and free of infection or dehiscence.

10. Any other clinically significant comorbidities.

11. Illnesses that could affect oral absorption.

12. Known human immunodeficiency virus or active hepatitis C infection only if the patient
is taking per protocol prohibited medications, active hepatitis B, or active hepatitis
C infection.

13. If female, the patient is pregnant or lactating.

14. Known allergy or hypersensitivity to any component of the investigational drug
product. Patients with history of Stevens-Johnson syndrome on a prior tyrosine kinase
inhibitor (TKI) are excluded.