Ribociclib and Doxorubicin in Treating Patients With Metastatic or Advanced Soft Tissue Sarcomas That Cannot Be Removed by Surgery

This is a dose-escalation study of the CDK4/6 inhibitor ribociclib in combination with
standard-dose doxorubicin.

PRIMARY OBJECTIVES:

I. To determine the recommended phase 2 dose (RP2D) of ribociclib in combination with
doxorubicin in subjects with advanced soft tissue sarcomas.

SECONDARY OBJECTIVES:

I. To assess preliminary anti-tumor activity of ribociclib in combination with doxorubicin in
subjects with advanced soft tissue sarcomas (Progression-Free Survival and Overall Response
Rate).

II. To characterize the safety and tolerability of ribociclib in combination with
doxorubicin.

A mandatory biopsy will be obtained after 7 days of ribociclib treatment.

TREATMENT: Patients receive ribociclib orally (PO) daily on days 1-7, and doxorubicin
intravenously (IV) on day 10. Treatment repeats every 21 days for up to 6 courses in the
absence of disease progression or unacceptable toxicity. After 6 courses, patients may
receive maintenance treatment with ribociclib PO daily on days 1-21. Courses repeat every 28
days in the absence of disease progression or unacceptable toxicity.

STARTING DOSE COHORT: Ribociclib 400 mg with doxorubicin 75 mg/m2.

FOLLOW-UP: After completion of study treatment, patients are followed up at 30 days and then
every 12 weeks for 12 months.

RATIONALE: Over-expression of CDK4 or loss of the CDK4 inhibitor p16 are common in sarcomas
and result in a selective growth advantage by bypassing normal cell cycle checkpoints. Intact
pRb is required for CDK4/6 inhibition to be effective, therefore all eligible subjects must
have documented pRb expression by IHC on archival tissue. Synergy between CDK4 inhibition and
chemotherapy has been documented in preclinical models when given sequentially, suggestion a
role for cell cycle synchronization.

Inclusion Criteria:

- Pathologically confirmed diagnosis of intermediate or high-grade soft tissue sarcoma
for which single-agent doxorubicin is appropriate therapy, including but not limited
to:

- Synovial sarcoma

- Fibrosarcoma

- Undifferentiated sarcoma

- Liposarcoma

- Leiomyosarcoma

- Angiosarcoma

- Malignant peripheral nerve sheath tumor

- Pleomorphic rhabdomyosarcoma

- Myxofibrosarcoma

- Epithelioid sarcoma

- Undifferentiated pleomorphic sarcoma

- Locally advanced unresectable or metastatic disease with no standard curative therapy
available

- Archival tumor tissue retinoblastoma-associated protein (pRb) positive by
immunohistochemistry (IHC)

- Measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1
criteria

- All races and ethnic groups will be included; for subjects between the ages of 15-18
years only, body surface area (BSA) must be >= 1.5 m^2

- Ejection fraction of >= 50% by echocardiogram or multi-gated acquisition (MUGA) scan

- Female subjects of childbearing potential must have a negative urine beta-human
chorionic gonadotropin (beta-hCG) pregnancy test at time of screening and within 14
days prior to planned first dose of ribociclib

- Willing to use adequate contraception throughout the study and for 3 weeks after study
drug discontinuation

- Meets the following standard 12-lead electrocardiography (ECG) parameters at screening
(defined as the mean of the triplicate ECGs):

- Corrected QT using Fridericia's correction formula (QTcF) interval at screening <
450 msec for males and < 470 msec for females

- Resting heart rate =< 100 beats per minute (bpm)

- Absolute neutrophil count (ANC) >= 1.5 K/cu mm

- Platelets (no transfusion within prior 7 days) >= 100 K/cu mm

- Hemoglobin (no transfusion within prior 7 days) >= 9.0 g/dL

- Total bilirubin < institutional upper limit of normal (ULN), except for subjects with
documented Gilbert's syndrome, for which =< 3.0 x ULN or direct bilirubin =< 1.5 x ULN

- Aspartate aminotransferase (AST) (serum glutamic-oxaloacetic transaminase [SGOT]) and
alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT) in the
absence of liver metastases: =< 2.5 x ULN; if the subject has liver metastases: < 5 x
ULN

- Serum creatinine < 1.7 mg/dL

- Potassium within institutional normal limit (WNL)

- Corrected calcium WNL

- Magnesium WNL

- International normalized ratio (INR) =< 1.5

- Use of rivaroxaban, apixaban, edoxaban or warfarin is an exclusion criteria;
therapy with heparin, low molecular weight heparin (LMWH), dabigatran or
fondaparinux is allowed

- All prior treatment-related toxicities resolved to =< grade 1 or are determined to be
clinically stable by the investigator

- Has completed prior therapies according to the criteria below:

- Cytotoxic chemotherapy - at least 21 days since last dose prior to first dose of
ribociclib

- Small molecule inhibitors - at least 14 days since last dose prior to first dose
of ribociclib

- Monoclonal antibodies - at least 3 half-lives since last dose prior to first dose
of ribociclib; exception: denosumab for bony metastases is allowable

- Immunotherapy (e.g. tumor vaccines) - at least 42 days since last dose prior to
first dose of ribociclib

- Radiation - at least 14 days since last dose prior to first dose of ribociclib

- Able to swallow capsules

- Eastern Cooperative Oncology Group (ECOG) performance status =< 2 (Karnofsky >= 60%)

- Life expectancy > 3 months

- Ability to understand and the willingness to sign a written informed consent document;
subject has signed the informed consent (ICF) prior to any screening procedures being
performed and is able to comply with protocol requirements

Exclusion Criteria:

- Subjects with low grade tumors (histologic grade 1/3)

- Histologic diagnosis for which single-agent doxorubicin is NOT appropriate therapy,
including but not limited to:

- Alveolar or embryonal rhabdomyosarcoma

- Ewings sarcoma or primitive neuroectodermal tumor (PNET)

- Osteosarcoma

- Gastrointestinal stromal tumor (GIST)

- Prior systemic therapy with an anthracycline for any indication

- Known hypersensitivity to any of the excipients of ribociclib or doxorubicin

- Currently receiving any of the following that cannot be discontinued at least 7 days
prior to starting study drug:

- Known strong inducers or inhibitors of CYP3A4/5, including grapefruit, grapefruit
hybrids, pummelos, star-fruit, and Seville oranges

- Medications with a narrow therapeutic window that are predominantly metabolized
through CYP3A4/5

- Herbal supplements, such as St. John's wort; the use of marijuana or its
derivatives is allowed in States with statutes permitting the use of recreational
or medical marijuana

- Uncontrolled intercurrent medical condition including, but not limited to:

- Uncontrolled infection

- Symptomatic congestive heart failure (New York Heart Association [NYHA] class
III-IV)

- Acute coronary syndromes (including myocardial infarction, unstable angina,
coronary artery bypass grafting, coronary angioplasty, or stenting) or
symptomatic pericarditis within 6 months prior to screening

- Uncontrolled cardiac arrhythmia or arrhythmia requiring medication other than
beta blocker

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

- Any other concurrent severe and/or uncontrolled medical condition that would, in
the investigator's judgment, cause unacceptable safety risks or compromise
compliance with the protocol (e.g. chronic pancreatitis, chronic active
hepatitis, etc.)

- Concurrent malignancy or malignancy within 3 years prior to starting study drug, with
the exception of malignancies that have completed therapy and are considered by their
physician to be at less than 30% risk of relapse

- Central nervous system (CNS) involvement unless they meet ALL of the following
criteria:

- At least 4 weeks from prior therapy completion (including radiation and/or
surgery) to starting the study treatment

- Clinically stable CNS tumor at the time of screening and not receiving steroids
and/or enzyme-inducing anti-epileptic medications for brain metastases

- Impairment of gastrointestinal (GI) function or GI disease that may significantly
alter the absorption of the study drugs (e.g., ulcerative diseases, uncontrolled
nausea/vomiting/diarrhea, malabsorption syndrome, or major small bowel resection)

- Known history of human immunodeficiency virus (HIV) infection (testing not mandatory);
NOTE: HIV-positive subjects on combination antiretroviral therapy are ineligible
because of the potential for pharmacokinetic interactions with ribociclib; in
addition, these subjects are at increased risk of lethal infections when treated with
marrow suppressive therapy; appropriate studies will be undertaken in subjects
receiving combination antiretroviral therapy when indicated

- Systolic blood pressure (SBP) > 160 mmHg or < 90 mmHg at screening; if initial
screening SBP is outside of the eligible range, blood pressure may be re-checked after
intervention; SBP must be documented as stable and within the eligible range prior to
starting study drug

- Currently receiving rivaroxaban, apixaban, endoxaban, warfarin or other warfarin
derived anticoagulant; therapy with heparin, low molecular weight heparin (LMWH),
dabigatran or fondaparinux is allowed; if transitioning from a prohibited
anticoagulant, a minimum washout of 7 days from last dose of the prohibited medication
is required prior to ribociclib start

- Participation in a prior investigational interventional study within 30 days prior to
enrollment or within 5 half-lives of the investigational product, whichever is longer

- Major surgery within 14 days prior to starting study drug or has not recovered from
surgical complications (tumor biopsy is not considered as major surgery)

- History of congenital long QT syndrome or torsades de pointes

- History of non-compliance to medical regimen or inability to grant consent

- Pregnant or nursing (lactating) women; breastfeeding should be discontinued