A Phase 2 Study of LY3023414 and Abemaciclib With or Without Letrozole in Endometrial Cancer

This is a Phase II clinical trial with a safety lead-in.The safety lead-in will test the
safety of a combination of investigational drugs and also try to define the appropriate dose
of the combination to use for further studies. "Investigational" means that the drugs are
being studied.

The FDA (the U.S. Food and Drug Administration) has not approved LY3023414 as a treatment for
any disease. The FDA has not approved abemaciclib or letrozole for this specific disease, but
both drugs have been approved for other uses.

Abemaciclib is a cyclin-dependent kinase (CDK) inhibitor and LY3023414 is a phosphoinositide
3-kinase (PI3K) inhibitor. Both PI3K and CDK inhibitors work to stop cancer cell growth.
Letrozole is a hormonal therapy that works by lowering the production of estrogen in the
body. Estrogen may help to stimulate cancer cells to grow, so lowering the levels of estrogen
in the body may work to slow cancer cell growth. In this research study, the investigators
are hoping to learn whether the combination of LY3023414, abemaciclib, and letrozole is
effective at slowing or stopping endometrial cancer cell growth.

Inclusion Criteria:

- Participants must have cytologically or histologically confirmed endometrial cancer
that is recurrent or metastatic and/or resistant to standard therapies, or for which
no standard therapy is available.

- For enrollment to Cohort 1: Participants must have ER-positive disease, defined as ≥ 1
percent of tumor cell nuclei being immunoreactive by immunohistochemistry (IHC). If
multiple analyses have been performed, judgment should be based on the most recent
biopsy or pathology specimen analyzed in a CLIA-certified laboratory.

- For enrollment to Cohort 2: Participants must have ER-negative disease, defined as < 1
percent of tumor cell nuclei being immunoreactive by IHC. If multiple analyses have
been performed, judgment should be based on the most recent biopsy or pathology
specimen analyzed in a CLIA-certified laboratory.

- For enrollment to Cohort 2: Documented evidence of PI3K pathway dependence including
PIK3CA, PIK3R1, PTEN hotspot mutations, PTEN loss, or other (unlisted) alterations as
agreed upon with the overall principal investigator. Analysis must have been performed
on a tumor tissue specimen in a CLIA-certified laboratory. All genetic findings must
be reviewed and approved by the overall principal investigator prior to study entry.

- Participants must have measurable disease, defined as at least one lesion that can be
accurately measured in at least one dimension (longest diameter to be recorded for
non-nodal lesions and short axis for nodal lesions) as ≥20 mm with conventional
techniques or as ≥10 mm with spiral CT scan, MRI, or calipers by clinical exam. See
Section 11 for the evaluation of measurable disease.

- Age ≥ 18 years

- ECOG performance status of 0 or 1(see Appendix A)

- Participants must have normal organ and bone marrow function as defined below:

- Absolute neutrophil count ≥ 1,500/mcL

- Platelets ≥ 100,000/mcL

- Total bilirubin ≤ 1.5 × institutional upper limit of normal (ULN)

- AST(SGOT)/ALT(SGPT) ≤ 2.5 × institutional ULN, OR

- 5 × institutional ULN if liver metastases are present

- Creatinine ≤ 1.5 × institutional ULN, OR

- Creatinine clearance ≥ 60 mL/min/1.73 m2 for participants with creatinine levels
above institutional normal.

- The effects of the study agents on the developing human fetus are unknown. For this
reason, women of child-bearing potential must agree to use a medically approved
contraceptive method during the treatment period and for 3 months following the last
dose of study agent. Contraceptive methods may include an intrauterine device (IUD) or
barrier method. If condoms are used as a barrier method, a spermicidal agent should be
added as a double barrier protection. Should a woman become pregnant or suspect she is
pregnant while she is participating in this study, she should inform her treating
physician immediately. A negative serum pregnancy test is required for study entry
from women of childbearing potential.

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

- Ability to swallow and retain oral medication.

- Participants must have a documented baseline hemoglobin A1c (HbA1c) < 7%. Participants
with non-insulin dependent diabetes mellitus are eligible if adequate control of blood
glucose level is obtained by oral anti-diabetic agents.

- Participants must have archival tissue available for analysis in the form of a
formalin-fixed paraffin embedded (FFPE) block or unstained slides. Note: confirmation
of availability of archival tissue is the only requirement for eligibility, archival
tissue does not need to be received by the study team prior to enrollment

Exclusion Criteria:

- Participants who have had chemotherapy, immune therapy, other investigational therapy,
or major surgery within 4 weeks (6 weeks for nitrosoureas or mitomycin C) prior to the
first dose of study medication. Previous hormonal therapy, including prior letrozole,
is allowed and there is no required washout period for hormonal therapy.

- Participants who have had tyrosine kinase inhibitor (TKI) therapy within 5 half-lives
of study entry.

- Participants who have had radiation therapy within 2 weeks of the first dose of study
medication.

- Participants who have received previous treatment with CDK4/6 inhibitors, including
but not limited to previous abemaciclib therapy.

- Participants who have received previous treatment with PI3K inhibitors, including but
not limited to previous LY3023414 therapy.

- Participants with known brain metastases should be excluded from this clinical trial
because of their poor prognosis and because they often develop progressive neurologic
dysfunction that would confound the evaluation of neurologic and other adverse events.

- History of allergic reactions attributed to compounds of similar chemical or biologic
composition to the study agents that the participant will be administered.

- Participants with insulin-dependent diabetes mellitus or histories of gestational
diabetes mellitus.

- Participants who at the time of study enrollment are known to require concomitant
therapy with moderate or strong CYP3A4 inducers, or strong inhibitors of CYP3A4. Due
to potential drug interactions, concomitant use of these medications is not permitted
for the duration of treatment on trial. Participants are eligible for study entry if
an appropriate substitution is made prior to the first dose of study medication.

- Uncontrolled intercurrent illness including, but not limited to, ongoing or active
infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
arrhythmia, or psychiatric illness/social situations that would limit compliance with
study requirements.

- Participants with histories or evidence of cardiovascular risk including any of the
following: acute coronary syndromes (i.e. myocardial infarction or angina), coronary
angioplasty, or stenting within 6 months prior to study enrollment.

- Pregnant women are excluded from this study because the study agents are anti-cancer
agents with the potential for teratogenic or abortifacient effects. Because there is
an unknown but potential risk for adverse events in nursing infants secondary to
treatment of the mother with the study agents, breastfeeding must be discontinued if
the mother is treated on trial.

- Individuals with a history of a different malignancy are ineligible with the following
exceptions: individuals who have been treated and are disease-free for a minimum of 5
years prior to study enrollment, or individuals who are deemed by the treating
investigator to be at low risk for disease recurrence. Additionally, individuals with
the following cancers are eligible if diagnosed and treated within the past 5 years:
basal or squamous cell carcinomas of the skin, and breast or cervical carcinomas in
situ.

- Known HIV-positive participants are ineligible because of the increased risk of lethal
infections when treated with marrow-suppressive therapy.

- Participants with a history of atrial fibrillation or atrial flutter.

- Participants with a history of uncontrolled hypertension despite optimal medical
management, defined as systolic blood pressure > 150 mmHg or diastolic blood pressure
> 90 mmHg