Clinical Trial of SP-2577 (Seclidemstat) in Patients With Relapsed or Refractory Ewing Sarcoma

This phase 1 study is an open-label, non-randomized dose escalation study of SP-2577
administered orally in patients with refractory or recurrent Ewing sarcoma. The study design
is based on a Simon's 4B design.

Inclusion Criteria:

- Patients must have a histologic confirmed diagnosis of Ewing sarcoma that is
refractory or recurrent and must have received at least one prior course of therapy
for Ewing sarcoma. For the purposes of this study, refractory disease is defined as
metastatic or unresectable disease that has either progressed or is stable at
completion of planned therapy.

- Patients must have radiographic evidence of disease. Patients must have disease
evaluable by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. Bone only
disease that has been biopsy-proven is acceptable during dose escalation but not
expansion phase.

- Patients must have had prior camptothecin-based regimen, have a contraindication to
camptothecin-based regimen, or declined treatment with a camptothecin-based regimen.

- Age ≥ 12 years and weight ≥ 40 kg.

- Karnofsky ≥70% for over ≥16 years old and Lansky ≥70% for under 16 years old, see
Appendix A, equivalent to Eastern Cooperative Oncology Group (ECOG) performance status
grade 0 or 1

- Life expectancy of greater than 4 months.

- Patients must have normal organ and marrow function

- Archival tumor tissue available for translocation analysis or willingness to provide
tumor biopsy during screening.

- Willingness to provide tumor biopsies on and off treatment (Tier 2: Dose expansion
cohort only). Optional for patients <18 years of age.

- Ability to understand and the willingness to sign a written informed consent document.

Exclusion Criteria:

- Patients who have not recovered to grade 1 or baseline from adverse events related to
prior therapy excluding lymphopenia, alopecia, peripheral neuropathy and ototoxicity,
which are excluded if ≥ CTCAE grade 3.

- Patients who are receiving any other investigational agents.

- Prior therapy with LSD1 targeted agents including monoamine oxidases for cancer
therapy.

- Prior systemic anti-cancer treatment (chemotherapy, biologic therapy [ie. small
molecular inhibitors, monoclonal antibodies]) within 21 days prior to Cycle 1 Day 1.
For agents that have known adverse events occurring beyond 21 days after
administration, this period must be extended beyond the time during which adverse
events are known to occur. The duration of this interval must be discussed with the
study chair.

- Prior therapy with immunotherapy such as a checkpoint inhibitor, cellular therapy or
vaccine within 42 days prior to Cycle 1 Day 1

- Prior small port palliative radiotherapy within 14 days or 42 days from definitive
local control radiation (any dose greater than 50Gy).

- Prior therapy with long acting myeloid growth factor within 14 days or 7 days from a
short acting myeloid growth factor.

- Evidence of graft versus host disease or prior allo- or auto-bone marrow transplant
(BMT) or stem cell infusion within 84 days from Cycle 1 Day 1 or receiving
immunosuppression following a stem cell procedure.

- Participation in a prior investigational study within 30 days prior to Cycle 1 Day 1
or within 5-half-lives of the investigational product, whichever is longer.

- Patients with progressive or symptomatic brain metastases. Patients with brain
metastases may be included in this trial as long as the brain metastases have received
definitive treatment and are stable (i.e., no evidence of progression). The brain
metastases must be stable for a minimum of 6 weeks.

- Patients currently receiving any of the following substances and cannot be
discontinued 14 days prior to Cycle 1 Day 1:

- Moderate or strong inhibitors or inducers of major CYP isoenzymes, including
grapefruit, grapefruit hybrids, pomelos, star-fruit, and Seville oranges

- Moderate or strong inhibitors or inducers of major drug transporters

- Substrates of CYP3A4/5 with a narrow therapeutic index

- Uncontrolled concurrent illness including, but not limited to:

- ongoing or active infection

- transfusion dependent thrombocytopenia or anemia

- psychiatric illness/social situations that would limit compliance with study
requirements

- Clinically significant, uncontrolled heart disease and/or cardiac repolarization
abnormality, including any of the following:

- symptomatic congestive heart failure

- Left Ventricular Ejection Fraction (LVEF) ≤ 50%

- unstable angina pectoris or cardiac arrhythmia

- baseline QTc ≥ 450 milliseconds

- Long QT syndrome or family history of idiopathic sudden death or congenital long
QT syndrome

- Any major surgery within 21 days prior to Cycle 1 Day 1.

- Pregnant and breastfeeding women are excluded from this study. The effects of SP-2577
on the developing human fetus have the potential for teratogenic or abortifacient
effects. There is an unknown but potential risk for adverse events in nursing infants
secondary to treatment of the mother with SP-2577.

- Women of child-bearing potential and men must agree to use adequate contraception
(hormonal or barrier method of birth control; abstinence) prior to study entry and for
the duration of study participation. Should a woman become pregnant or suspect she is
pregnant while she or her partner is participating in this study, she should inform
her treating physician immediately. Men treated or enrolled on this protocol must also
agree to use adequate contraception prior to the study, for the duration of study
participation, and 4 months after completion of SP-2577 administration.

- HIV-positive patients on combination antiretroviral therapy are ineligible because of
the potential for pharmacokinetic interactions with SP-2577. In addition, these
patients are at increased risk of lethal infections when treated with
marrow-suppressive therapy.