First-Line Sacituzumab Govitecan in Advanced Untreated Triple-Negative Breast Cancer Patients.

Inclusion Criteria: Participants must meet all the following criteria to be eligible for participation in this study: 1. Willing and able to provide informed consent. 2. Age \>18 years old at the time of informed consent and has signed informed consent before any trial related activities are conducted according to local guidelines. 3. For participants of child-bearing potential (menstruation within \<2 years): negative serum pregnancy test within 14-days prior to enrollment and must be willing to use Health Canada-approved effective contraception methods (e.g., hormonal contraceptives, intrauterine device or system, tubal ligation, or double barrier method) starting 1 week prior to study treatment, throughout the study, and for 6 months following the last dose of SG. 4. For participants considered not of child-bearing potential (postmenopausal): must meet one of the following criteria at the time of study entry: i. Prior bilateral oophorectomy ii. Age \> 60 iii. Age \< 60 with \>12 months of spontaneous amenorrhea (not due to chemotherapy, tamoxifen, toremifene, or ovarian suppression) and laboratory confirmation of postmenopausal FSH and estradiol levels per local postmenopausal reference ranges iv. Ovarian suppression with gonadotropin-releasing hormone (GnRH) agonist (e.g., goserelin) initiated \>28 days before Cycle 1 Day 1 5. Advanced (locoregionally recurrent and non-operable, or metastatic) triple-negative breast cancer patients not amenable to curative therapy (surgery and/or radiotherapy), including those who are PDL1 negative (combined positive score \[cps\] \<10), immuno-oncology therapy ineligible, or who had early-relapse after neoadjuvant therapy and not eligible for immuno-oncology in the first-line setting. 6. Histologically and/or cytologically confirmed diagnosis of estrogen-receptor negative breast cancer by local laboratory testing (based on most recently analyzed biopsy). 7. HER2-negative breast cancer (based on most recently analyzed biopsy) defined as negative in situ hybridization test or an immunohistochemistry (IHC) status of 0, 1+ or 2+. If IHC is 2+, a negative in situ hybridization (FISH, CISH, SISH) test is required by local laboratory testing, as defined in the relevant American Society of Clinical Oncology / College of American Pathologists Guidelines. 8. Not previously received systemic therapy in the advanced setting. 9. Participants can have measurable or non-measurable disease by CT or MRI as per RECIST Version 1.1 criteria as evaluated locally. Tumour lesions situated in a previously irradiated area are considered measurable if unequivocal progression has been documented in such lesions since radiation. All radiology studies must be performed within 28-days of Day 1 Cycle 1. 10. Eastern Cooperative Oncology Group (ECOG) performance status 0-1. 11. Life expectancy \> 3 months. 12. Acceptable bone marrow and organ function defined by the following laboratory values without transfusion or growth factor support within 2 weeks of treatment initiation: a. Absolute neutrophil count \> 1.0 x 109/L i. Platelets \> 100 x 109/L ii. Hemoglobin \> 90 g/dL iii. Potassium, sodium, calcium (corrected for serum albumin), and magnesium within normal limits. iv. INR \< 1.5 v. Serum creatinine \<1.5 x upper limit of normal (ULN) or calculated (Cockroft-Gault) or measured creatinine clearance ≥50 mL/min/1.73 m2 b. In absence of liver metastases, ALT and AST should be below \<3.0 x ULN. If the participant has liver metastases, ALT and AST should be \< 5.0 x ULN. c. In absence of liver metastases, total serum bilirubin \< ULN; If the participant has liver metastases, total bilirubin \< 3.0 x ULN with direct bilirubin \< 1.5 x ULN. 13. Consents to allow access and provision of pre- and post-treatment biopsy specimens for study purposes. 14. Able to communicate with the Investigator and comply with the requirements of the study procedures. 15. Controlled brain metastasis (as per clinical determination) is allowed in the study at least 4 weeks before treatment. Controlled brain metastasis is defined as asymptomatic brain metastasis or no longer requiring high doses of corticosteroids (\>10 mg Dexamethasone per day) for central nervous system (CNS) symptom management. Anticonvulsants and stable corticosteroids dose can be included in the study. Waivers to the inclusion criteria will NOT be allowed. Exclusion Criteria: Participants are excluded from the study if any of the following criteria apply: 1. Are within 4 weeks of participating in any other type of medical research judged by the Investigator to not be scientifically or medically compatible with this study. 2. Tumour not accessible or not safe to perform biopsies. 3. Has a known hypersensitivity to SG, irinotecan or its active metabolite SN-38. 4. Has received prior antibody-drug conjugate containing a topoisomerase 1 inhibitor. 5. Has a history of significant cardiovascular diseases, such as congestive heart failure greater than New York Heart Association (NYHA) Class II, unstable angina, myocardial infarction, serious cardiac arrhythmia, clinically significant electrocardiogram (ECG) findings or any other clinically significant cardiovascular condition, as determined by the Investigator. 6. Has a history or evidence of any condition or laboratory abnormality that would place the participant at undue risk, as determined by the Investigator. 7. Currently active Hepatitis B virus (HBV) or active Hepatitis C virus (HCV). 1. For participants with a history of HBV infection, a hepatitis B core antibody test should be conducted at screening. If positive, hepatitis B DNA testing will be performed and if active HBV infection is ruled out, the participant may be eligible. 2. Those who are HCV antibody positive with undetectable HCV viral load may be eligible. 8. Has an active human immunodeficiency virus (HIV) infection (e.g., with detectable viral load). a. Participants positive for HIV-1 or