Study of TTC-352 in Patients With Metastatic Breast Cancer Progressing on Endocrine Therapy

This is open-label, accelerated dose escalation study of TTC 352, a selective human ER
partial agonist for treatment of metastatic ER+ breast cancer in patients who received and
progressed on at least two lines of endocrine therapy with one that included a CDK4/CDK6
inhibitor.

The primary objective of this study is to determine the maximum tolerated dose (MTD) of
TTC-352 for the treatment of metastatic ER+ breast cancer progressing after endocrine
therapy.

The maximum tolerated dose (MTD) of TTC-352 will be determined using initial single-patient
cohort escalations until grade 2 toxicity, then expansion to a modified-Fibonacci
dose-escalation 3+3 design. Patients enrolled at each dose escalation step must complete the
first 28-day cycle of treatment without a dose-limiting toxicity (DLT), or be withdrawn
because of a DLT, before additional patients may be enrolled for the next dose escalation
step. The MTD dose level cohort will be expanded to a total of 9 patients, to further
evaluate safety. In each cohort pharmacokinetics of TTC-352 will be evaluated.

Inclusion Criteria:

1. be ≥18 years of age;

2. have a diagnosis of metastatic ER+ breast cancer in patients who received and
progressed on at least two lines of endocrine therapy, with one that included a
CDK4/CDK6 inhibitor (e.g., palbociclib or ribociclib);

3. have metastatic disease evaluable on imaging studies;

4. have a histologically confirmed diagnosis of ER+ breast cancer;

5. have an Eastern Cooperative Oncology Group (ECOG) performance status of ≤1 (Appendix
II);

6. have adequate hepatic function, defined as having a serum total bilirubin
concentration ≤1.5mg/d, or ≤2 x the upper limit of normal (ULN) if associated with
hepatobiliary metastases or Gilbert syndrome, and having serum aspartate
aminotransferase (AST) and alanine aminotransferase (ALT) concentrations ≤2.5 × ULN,
or ≤5 x ULN for patients with known hepatic metastases;

7. have adequate renal function, defined as having a serum creatinine ≤1.5 × ULN and a
creatinine clearance ≥40mL/min (estimated using the Cockcroft-Gault formula);

8. have adequate hematologic function, defined as having a hemoglobin ≥8g/dL, an absolute
neutrophil count (ANC) ≥1.0 × 109/L, and platelet count ≥75.0 x 109/L;

9. be willing and able to comply with study visits and procedures;

10. have read, understood and signed the informed consent form (ICF) approved by the
Institutional Review Board (IRB);

11. if a woman of childbearing potential (WOCP), not be pregnant (confirmed by a negative
serum pregnancy test within 14 days of study entry and re-confirmed by a urine
pregnancy test on the morning of Study Day 1, prior to the start of study treatment)
and/or not be breast-feeding; [Note: Women who are postmenopausal for at least 1 year
or surgically sterile (bilateral tubal ligation, bilateral oophorectomy or
hysterectomy) are not considered to be a WOCP.]

12. If a WOCP, agree to use during the study and for at least one month after the last
dose of study drug a medically acceptable method of birth control [such as an oral,
implantable, injectable, or transdermal hormonal contraceptive, an intrauterine device
(IUD), a double barrier method (condoms, sponge, diaphragm, or vaginal ring with
spermicidal jellies or cream), or total abstinence.];

13. if male (and whether or not surgically or medically sterile), agree to use during the
study and for at least one month after the last dose of study drug a double barrier
method of birth control (in addition to any other birth control method practiced by
his partner) while engaging in sexual intercourse with a partner who is pregnant,
possibly pregnant or able to become pregnant.

Exclusion Criteria:

1. have received chemotherapy, hormonal therapy, biologic therapy, immunotherapy or
radiation therapy within 14 days prior to the planned start of study treatment.

2. have inadequate recovery* from adverse events resulting from previously-administered
anti-cancer therapies; [*Note: Unless more specifically defined in Inclusion Criteria
6, 7 and 8 above, adequate recovery is defined as improvement to ≤ Grade 2 for any
other hematologic toxicity and for peripheral neuropathy, and improvement to ≤ Grade 1
for any other non-hematologic toxicity.]

3. have a history of venous thromboembolism, including deep vein thrombosis, pulmonary
embolism or retinal vein thrombosis, unless currently on anticoagulant therapy;

4. have impending visceral crisis that requires chemotherapy;

5. have known uncontrolled or symptomatic CNS metastases;

6. have any clinically significant infection, defined as any acute viral, bacterial, or
fungal infection that requires systemic treatment or have received any anti-infective
treatment within 7 days prior to the screening visit;

7. have any other severe, uncontrolled medical condition, including unstable congestive
heart failure (Stage III-IV of the New York Heart Association Functional
Classification (Appendix III))

8. have a known or suspected allergy to the study drug or any study drug component;

9. have any other medical or psychiatric condition or laboratory abnormality that may
increase the risk associated with study participation, that may interfere with the
interpretation of study results or that otherwise would, in the opinion of the
Investigator, make study participation inappropriate;

10. have any non-healing wound, fracture, or ulcer within 28 days prior to the planned
start of study treatment;

11. have received any other investigational drug within 28 days (or 5 half-lives, if
longer) prior to the start of study screening.