- Pre or postmenopausal women with stage IV hormone receptor-positive breast cancer by
histological or cytological confirmation
- Be willing and able to provide written informed consent/assent for the trial
- Progression after 1 or more lines of any systemic therapy (endocrine, HER2-targeted or
chemotherapy) in the metastatic setting
- Be over 19 years of age on day of signing informed consent
- 70 or more nonsynonymous mutations per tumor by WES
- Subject who has biopsy-accessible tumor for WES. Biopsy on breast tumor or axillary
nodes is acceptable if locoregional recurrence after primary surgery occurs or de novo
stage IV breast cancer is diagnosed
- Have measurable disease based on RECIST 1.1. Biopsied tumor may be counted a
measurable lesion if it is not excised
- Documented disease progression on the most recent therapy
- Life expectancy of > 12 weeks
- Have a performance status of 0 or 1 on the ECOG Performance Scale.
- Demonstrate adequate organ function as defined in Table 3, all screening labs should
be performed within 10 days of treatment initiation.
- Female subject of childbearing potential should have a negative urine or serum
pregnancy within 72 hours prior to receiving the first dose of study medication. If
the urine test is positive or cannot be confirmed as negative, a serum pregnancy test
will be required.
- Female subjects of childbearing potential (Section 5.5.2) must be willing to use an
adequate method of contraception as outlined in Section 5.7.2 - Contraception, for the
course of the study through 120 days after the last dose of study medication.
Note: Abstinence is acceptable if this is the usual lifestyle and preferred contraception
for the subject.
- Is currently participating and receiving study therapy or has participated in a study
of an investigational agent and received study therapy or used an investigational
device within 4 weeks of the first dose of treatment.
- Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any
other form of immunosuppressive therapy within 7 days prior to the first dose of trial
- Has a known history of active TB (Bacillus Tuberculosis)
- Hypersensitivity to pembrolizumab or any of its excipients.
- Has had a prior anti-cancer monoclonal antibody (mAb) within 4 weeks prior to study
Day 1 or who has not recovered (i.e., ≤ Grade 1 or at baseline) from adverse events
due to agents administered more than 4 weeks earlier.
- Has had prior chemotherapy, targeted small molecule therapy, or radiation therapy
within 2 weeks prior to study Day 1 or who has not recovered (i.e., ≤ Grade 1 or at
baseline) from adverse events due to a previously administered agent. Note: Subjects
with irreversible toxicity that is not reasonably expected to be exacerbated by the
investigational product may be included (e.g., ≤ Grade 2 neuropathy; hair loss, et
al.), Note: If subject received major surgery, they must have recovered adequately
from the toxicity and/or complications from the intervention prior to starting
- Has a known additional malignancy that is progressing or requires active treatment.
However, malignancies that have been curatively treated >5 years prior to study entry
can be included. Exceptionally, cervical cancer in-situ, basal cell carcinoma or
squamous cell carcinoma of the skin, papillary thyroid carcinoma and superficial
bladder tumors (T1a and Tis) can be included anytime after potentially curative
- Has known active central nervous system (CNS) metastases and/or carcinomatous
meningitis. Subjects with previously treated brain metastases may participate provided
they are stable (without evidence of progression by imaging for at least four weeks
prior to the first dose of trial treatment and any neurologic symptoms have returned
to baseline), have no evidence of new or enlarging brain metastases, and are not using
steroids for at least 7 days prior to trial treatment. This exception does not include
carcinomatous meningitis which is excluded regardless of clinical stability.
- Has active autoimmune disease that has required systemic treatment in the past 2 years
(i.e. with use of disease modifying agents, corticosteroids or immunosuppressive
drugs). Replacement therapy (eg., thyroxine, insulin, or physiologic corticosteroid
replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a
form of systemic treatment.
- Has known history of or any evidence of active, non-infectious pneumonitis.
- Evidence of interstitial lung disease.
- Has an active infection requiring systemic therapy.
- Has a history or current evidence of any condition, therapy, or laboratory abnormality
that might confound the results of the trial, interfere with the subject's
participation for the full duration of the trial, or is not in the best interest of
the subject to participate, in the opinion of the treating investigator.
- Has known psychiatric or substance abuse disorders that would interfere with
cooperation with the requirements of the trial.
- Is pregnant or breastfeeding, or expecting to conceive or father children within the
projected duration of the trial, starting with the pre-screening or screening visit
through 120 days after the last dose of trial treatment.
- Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent.
- Has a known history of Human Immunodeficiency Virus (HIV) (HIV 1/2 or HTLV-1
- Has known active Hepatitis B (e.g., HBsAg reactive) or Hepatitis C (e.g., anti-HCV
antibody detected or HCV RNA [qualitative] detected).
- Has received a live vaccine within 30 days of planned start of study therapy. Note:
Seasonal influenza vaccines for injection are generally inactivated flu vaccines and
are allowed; however intranasal influenza vaccines (e.g., Flu-Mist®) are live
attenuated vaccines, and are not allowed.