Trilaciclib, a CDK4/6 Inhibitor, in Patients With Early-Stage Triple Negative Breast Cancer

Inclusion Criteria:

* Suitability of therapy and patient intends to undergo curative surgery
* Documented diagnosis of estrogen receptor (ER)-negative and progesterone receptor (PR)-negative tumor
* Primary tumor ≥ 1.5 cm with any nodal status
* Provide archival tissue for the baseline tissue sample
* ECOG performance status of 0 or 1
* Demonstrates adequate organ function
* Research tumor biopsies including at least one on-treatment biopsy (and additional biopsy at baseline, if required)
* Participants of child bearing potential must be willing to use 2 forms of contraception during the study and for 6 months following study treatment

Exclusion Criteria:

* Prior systemic therapies or radiation for current breast cancer
* History of invasive malignancy ≤3 years prior to signing informed consent except for adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer
* History of breast cancer including ipsilateral ductal carcinoma in situ (DCIS) treated with radiotherapy at any time
* Previous exposure to doxorubicin of more than 200 mg/m2 (as lifetime exposure to doxorubicin is not to exceed 450 mg/m2)
* For patients who will receive pembrolizumab:

  * History of active autoimmune disease that has required systemic treatment in past 2 years (i.e., with use of disease modifying agents, corticosteroids, or immunosuppressive drugs). Replacement therapy is not considered a form of systemic treatment
  * 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 study drugs
* History of (non-infectious) pneumonitis that required steroids or current pneumonitis
* Known history of active tuberculosis (Bacillus Tuberculosis)
* History of severe hepatic impairment
* Uncontrolled ischemic heart disease or uncontrolled symptomatic congestive heart failure (Class II-IV as defined by the New York Heart Association \[NYHA\] functional classification system)
* Known history of stroke, cerebrovascular accident, severe/unstable angina, myocardial infarction, or coronary angioplasty/stenting/bypass grafting within 6 months prior to enrollment
* Known serious active infection (e.g., human immunodeficiency virus \[HIV\], hepatitis B or C, tuberculosis).
* Women who are pregnant or breastfeeding
* Participation in other studies involving active treatment with investigational drug(s)
* Prior hematopoietic stem cell or bone marrow transplantation