Inclusion Criteria:
1. Willing and able to provide written informed consent prior to study entry
2. Female ≥ 18 years of age
3. Eastern Cooperative Oncology Group (ECOG) Performance Status 0 to 1
4. Histologically confirmed TNBC
5. Node-positive (cT1-4 cN1-2 M0) and/or tumour size ≥2 cm (cT2-T4 cN0-2 M0) with no prior treatment
6. Adequate haematologic and end-organ function .
7. Patients of childbearing potential are eligible provided they have a negative serum or urine pregnancy test. Patients must agree to use adequate contraception
8. Ability to comply with the protocol
9. Representative formalin-fixed paraffin embedded breast tumour samples with an associated pathology report, determined to be available and sufficient for central testing OR tumour accessible for biopsy
Exclusion Criteria:
1. Evidence of metastatic breast cancer.
2. Any systemic therapy (e.g. chemotherapy, targeted therapy, immune-therapy) or radiotherapy for current breast cancer disease before study entry
3. Prior exposure to any CD137 agonists or immune checkpoint blockade therapies, including antiCTLA-4, anti-PD-1 or anti-PD-L1 antibody
4. Concurrent bilateral invasive breast cancer
5. Inflammatory breast cancer
6. Active malignancy (except for non-melanoma skin cancer, or histologically confirmed complete excision of carcinoma in-situ) within the past 36 months prior to study entry
7. Major surgery within the last 28 days or anticipation of the need for major surgery during study treatment
8. Known intolerance to any of the study drugs (ie, paclitaxel, doxorubicin, epirubicin, cyclophosphamide) or any of their excipients
9. Pre-existing peripheral neuropathy grade ≥ 2
10. History of autoimmune disease
11. History of Type I or Type II diabetes mellitus requiring insulin. Patients who are on a stable dose of oral diabetes medication ≥ 2 weeks prior to initiation of study treatment are eligible for enrolment
12. History of idiopathic pulmonary fibrosis or organising pneumonia
13. History of HIV infection
14. Known active hepatitis infection or hepatitis C.
15. Active tuberculosis
19\. Current treatment with anti-viral therapy for HBV
20\. Treatment with systemic immunostimulatory agents within 4 weeks or 5 half-lives of the drug (whichever is longer) prior to initiation of study treatment
21\. Patients receiving concomitant immunosuppressive agents or chronic systemic corticosteroids (≥10 mg prednisolone or an equivalent dose of other anti-inflammatory corticosteroids) use for ≥28 days at the time of study entry.
22\. Significant cardiovascular disease
16\. Severe infection within 4 weeks prior to initiation of study treatment
23\. Any other disease, metabolic dysfunction, physical examination finding, or clinical laboratory finding that, in the investigator's opinion, gives reasonable suspicion of a disease or condition that contraindicates the use of an investigational drug, may affect the interpretation of the results, render the patient at high risk from treatment complications or interferes with obtaining informed consent
24\. Psychological, familial, sociological or geographical conditions that do not permit compliance with the study protocol
25\. Concurrent treatment with other experimental drugs. Participation in another clinical trial with any investigational drug within 30 days prior to study entry
26\. Treatment with strong CYP3A inhibitors or strong CYP3A inducers within 2 weeks or 5 drug-elimination half-lives, whichever is longer, prior to initiation of study drug
27\. Persistent toxicities (≥CTCAE grade 2) caused by previous cancer therapy, excluding alopecia and peripheral neuropathy
28\. Pregnant or nursing women
29\. Inability to swallow medication or malabsorption condition that would alter the absorption of orally administered medications
30\. Clinically significant abnormalities of glucose metabolism
31\. History of or active inflammatory bowel disease or active bowel inflammation
