A Phase 1 Study of SY-1365 in Adult Patients With Advanced Solid Tumors

This study will consist of two parts. Part 1 is a dose-escalation/safety evaluation to
identify a dose and regimen for further evaluation in Part 2. SY-1365 will be administered
intravenously weekly & twice weekly for 3 weeks of each 4 week cycle. Dose escalation will
proceed until the determination of the maximum tolerated dose (MTD) or a recommended dose and
regimen for evaluation in Part 2 of the study. Approximately 35 patients may be enrolled into
Part 1, with the ultimate number based on the safety (DLTs).

Following the identification of a recommended dose and regimen from Part 1, the study will
enter Part 2 to further evaluate safety and the antitumor activity of SY-1365 in patients
with select solid tumors, and to confirm target engagement and downstream pathway impact in
patients with any solid tumor histology.

Preliminary anti-tumor activity will be evaluated in approximately 102 patients in 5 cohorts
of Part 2, with SY-1365 administered alone, in combination with carboplatin, or in
combination with fulvestrant. Part 2 will consist of five cohorts:

- Cohort 1: approximately 24 patients with advanced ovarian cancer with 3+ previous lines
of treatment. Monotherapy

- Cohort 2: approximately 24 patients with relapsed ovarian cancer with previous platinum
therapy. SY-1365 + Carboplatin

- Cohort 3: approximately 12 patients with primary platinum refractory ovarian cancer.
Monotherapy

- Cohort 4: approximately 20-30 patients with biopsy-accessible, advanced solid tumors of
any histology. Monotherapy.

- Cohort 5: approximately 12 patients with HR+ metastatic breast cancer post CDK4/6 +
aromatase inhibitor treatment. SY-1365 + fulvestrant.

Overall, the study may enroll approximately 137 patients across dose escalation (Part 1) and
expansion cohorts (Part 2, Cohorts 1, 2, 3, 4, and 5).

Inclusion Criteria:

- 18 years of age or older

- Disease status

- Part 1: any histologically-confirmed metastatic or unresectable solid tumor for
which standard curative or palliative measures do not exist or are no longer
effective

- Part 2, Cohorts 1-3, all patients must have a histologically-confirmed diagnosis
of high grade serous ovarian cancer (including fallopian tube cancer and/or
primary peritoneal cancer)

- Part 2, Cohort 1, Patients must have received ≥ 3 prior treatment regimens for
ovarian cancer including a platinum-based regimen. Patients whose OC harbors a
mutation in breast cancer gene (BRCA), either germline or somatic, must have been
previously treated with a poly(ADP ribose) polymerase (PARP) inhibitor, or be
considered unwilling or ineligible for treatment with a PARP inhibitor

- Part 2, Cohort 2, Must have received ≥ 1 prior treatment regimen for ovarian
cancer, at least 1 of which is a platinum-based regimen

- Part 2,Cohort 3, Must have received only 1 prior platinum-based regimen. Patient
must have primary platinum refractory OC (defined as progression either while on
initial treatment with the platinum-based therapy or within 1 month following the
last dose of treatment)

- Part 2, Cohort 4, Any histologically-confirmed metastatic or unresectable solid
tumor for which standard curative or palliative measures do not exist or are no
longer effective. Must have accessible tumor tissue and be willing to undergo
tumor tissue sampling (biopsies/aspirates) pre- and post-treatment

- Part 2, Cohort 5, Postmenopausal women with hormone receptor (HR)-positive, human
epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast
cancer who have failed prior treatment with a CDK 4/6 inhibitor in combination
with an aromatase inhibitor (AI) as initial endocrine-based therapy.

- At least 1 measurable lesion by RECIST 1.1

- All toxicities (except alopecia) from prior cancer treatments must have resolved to ≤
Grade 1 or returned to baseline levels prior to enrollment

- Eastern Cooperative Oncology Group (ECOG) performance status of 0-1

- Life expectancy > 3 months

- absolute neutrophil count: ≥ 1.5 x 109/L

- platelets: ≥ 100 x 109/L

- hemoglobin: ≥ 9 g/dL

- total bilirubin ≤ 1.5 institutional upper limit of normal [ULN])

- AST (SGOT)/ ALT (SGPT): ≤ 3.0 x institutional ULN

- Creatinine ≤ 1.5 x institutional ULN OR creatinine clearance ≥ 60 mL/min by
Crockoft-Gault for participants with creatinine levels above institutional normal

- Negative pregnancy test for women of child bearing potential

Exclusion Criteria:

- Chemotherapy or limited field radiotherapy within 2 weeks, wide field radiotherapy
within 4 weeks, or nitrosoureas or mitomycin C within 6 weeks prior to entering the
study

- Major surgery within 2 weeks of starting the study treatment, or not recovered to
baseline status from the effects of surgery received > 2 weeks prior

- Received any other investigational agents within 4 weeks prior to enrollment, or < 5
half-lives since completion of previous investigational therapy, whichever is shorter

- Received previous non-cytotoxic, FDA-approved anticancer agent within previous 2
weeks, or < 5 half-lives since completion of previous therapy, whichever is shorter

- Prior exposure to transcriptional kinase family CDK inhibitors, such as the CDK7 and
CDK9 inhibitors alvocidib (Flavopiridol), dinaciclib, and seliciclib. Exception:
previous exposure to cell cycle CDK inhibitors such as CDK4 and CDK6 (eg, palbociclib)
is allowed

- Known brain metastases or carcinomatous meningitis. Exception: previously treated
brain metastatic disease that remains stable on MRI ≥ 4 weeks prior to enrollment,
without steroids or anti-epileptic medications

- History of allergic reactions attributed to compounds of similar chemical composition
to SY-1365

- Immunocompromised patients with increased risk of opportunistic infections, including
known HIV-positive patients

- Patients with known active Hepatitis B or Hepatitis C infection

- Prior treatment (< 2 weeks before start of SY-1365) with moderate or strong CYP3A4
inducers or strong CYP3A4 inhibitors. See list in Appendix 3

- Baseline QT interval corrected with Fridericia's method (QTcF) > 480 ms

- Significant cardiac risk, including: History of clinically significant cardiac disease
or clinically relevant uncontrolled cardiac risk factors

Part 2 Only:

- Cohorts 1, 2, and 3: Patients with low-grade ovarian cancer (eg, low grade serous,
mucinous carcinoma) are not eligible

- Cohort 2: Prior adverse reaction(s) to carboplatin

- Cohort 5: Prior treatment with fulvestrant; Prior treatment with chemotherapy for
advanced/metastatic disease; Any line(s) of therapy following treatment failure with a
CDK 4/6 inhibitor in combination with an AI; Prior treatment with chemotherapy in the
advanced/metastatic setting or with fulvestrant; Advanced/metastatic disease that is
symptomatic and/or with visceral spread