Inclusion Criteria for Trial Registration:

          1. Signed Informed Consent Form (ICF) for Trial Registration;

          2. Aged ≥18 years old;

          3. Histologically confirmed invasive triple negative breast cancer (TNBC). TNBC defined
             as ER negative, PgR negative (ER and PgR negative as defined by Allred score 0/8, 1/8
             or 2/8 or stain in <1% of cancer cells) or PgR unavailable, and HER2 negative
             (immunohistochemistry 0/1+ or negative in situ hybridization) as determined by local
             laboratory and recorded in the patients notes;

          4. Planned definitive surgical treatment after at least 6 cycles of neoadjuvant
             chemotherapy (NACT);

          5. Radiographically measurable tumour mass assessable for new distinct radio-opaque
             marker insertion and repeated biopsies on the NACT mid-assessment standard of care
             imaging modality (MRI or USS); or clinically thought to be >5cm in diameter (T3);

          6. Eastern Oncology Cooperative Group (ECOG) performance status 0-1;

          7. Considered fit enough to have breast cancer surgery with curative intent;

          8. Considered fit to complete at least 2 weeks of pre-operative trial treatment in the
             WOP;

          9. Patients must be suitable for a mandatory pre-treatment baseline biopsy performed Day
             -1 or 1 of the window of opportunity (WOP) and a post-treatment biopsy performed on
             Day 14 of the WOP. Registered patients who are approached for trial entry will be
             required to consent to the pre- and post- WOP treatment biopsy. If it is deemed unsafe
             to proceed with biopsy upon Trial Entry the patient will not be eligible for Trial
             Registration.

         10. Patients with clinical stage II disease or clinical suspicion of metastatic disease
             must have staging studies as per standard of care to exclude metastatic disease
             (axillary lymph nodes or internal mammary node involvement will not be regarded as
             evidence of metastatic disease);

         11. Patients with stage III disease must have staging studies as per standard of care at
             any point after diagnosis but before Trial Registration, to exclude metastatic disease
             (axillary lymph nodes or internal mammary node involvement will not be regarded as
             evidence of metastatic disease), even if asymptomatic.

         12. Patients with previous invasive cancers (including breast cancer) are eligible if the
             treatment was completed >5 years prior to Trial Registration, and there is no evidence
             of recurrent disease;

         13. Absence of any psychological, familial, sociological or geographical condition
             potentially hampering compliance with the trial protocol and follow-up schedule; those
             conditions should be discussed with the patient before Trial Registration;

         14. Patients must be a) surgically sterile (i.e. if female have undergone a hysterectomy,
             bilateral salpingectomy or bilateral oophorectomy; if male have undergone a bilateral
             orchidectomy);; b) have a sterilised sole partner; or c) be post-menopausal; or d)
             must agree to practice total/true abstinence; or e) use two highly effective forms of
             contraception in combination during the period of trial treatment and be willing to do
             so for a period of 3 months following the end of trial treatment. Please refer to
             Section 6.4 Lifestyle Guidance for the definition of total/true abstinence and
             acceptable non-hormonal and hormonal birth control methods for the trial.

        Post-menopausal is defined by at least one of the following criteria:

          1. Amenorrheic for 1 year or more following cessation of exogenous hormonal treatments

          2. Luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels in the
             post-menopausal range for the institution for women < 50 years of age not using
             hormonal contraception or hormonal replacement therapy. Please note: in absence of
             amenorrhea for 1 year, a single LH and/or FSH measurement is insufficient.

          3. Radiation-induced oophorectomy with last menses >1 year ago

          4. Chemotherapy-induced menopause with >1 year interval since last menses

          5. Surgical sterilisation (hysterectomy, bilateral salpingectomy or bilateral
             oophorectomy)

        Exclusion Criteria for Trial Registration:

          1. Definitive evidence of metastatic disease (axillary lymph nodes or internal mammary
             node involvement will not be regarded as evidence of metastatic disease);

          2. Patients with bilateral tumour;

          3. History of another primary malignancy within the last 5 years prior to Trial
             Registration, except for:

               1. Adequately treated non-melanoma skin cancer or lentigo maligna without evidence
                  of disease;

               2. Adequately treated carcinoma in situ without evidence of disease;

          4. Patients with myelodysplastic syndrome (MDS)/acute myeloid leukaemia (AML) or with
             features suggestive of MDS/AML;

          5. Severe concurrent disease, infection or co-morbidity that, in the judgment of the
             local Investigator, would make the patient inappropriate for Trial Registration;

          6. Resting ECG with QTc>470msec for females and > 450 msec for men on 2 or more time
             points within a 24 hour period, factors which increase the risk of QTc prolongation or
             family history of long QT syndrome;

          7. A diagnosis of ataxia telangiectasia;

          8. Patients unable to swallow orally administered medication;

          9. Patients receiving formal anti-coagulation treatment (including warfarin, novel oral
             anti-coagulants and LMWH).

         10. Patients with gastrointestinal disorder affecting absorption (e.g. gastrectomy, active
             peptic ulcer disease within last 3 months);

         11. History of seizure or any condition that may predispose to seizure.

         12. Other non-malignant systemic disease that would preclude trial treatment or would
             prevent required follow-up;

         13. Pregnant or breast-feeding;

         14. Prior exposure to ATR inhibitor (including AZD6738), PARP inhibitor (including
             olaparib), anti-PD-1 or anti-PDL1 immunotherapy (including durvalumab);

         15. Any other disease(s), psychiatric condition, metabolic dysfunction, or findings from a
             physical examination or clinical laboratory test result that in the investigators
             opinion would cause reasonable suspicion of a disease or condition, that
             contraindicates the use of trial treatment, that may increase the risk associated with
             trial participation, that may affect the interpretation of the results, or that would
             make this trial inappropriate for the patient;

         16. Patients with a known hypersensitivity to the trial treatments or any excipients of
             the products;

         17. Previous allogenic bone marrow transplant or double umbilical cord blood
             transplantation (dUCBT);

         18. Active or prior documented autoimmune or inflammatory disorders (including
             inflammatory bowel disease (e.g., colitis or Crohn's disease), diverticulitis (with
             the exception of diverticulosis), systemic lupus erythematosus, Sarcoidosis syndrome,
             or Wegener syndrome (granulomatosis with polyangiitis, Graves' disease, rheumatoid
             arthritis, hypophysitis, uveitis, etc.). The following are exceptions to this
             criterion:

               1. Patients with vitiligo or alopecia;

               2. Patients with hypothyroidism (e.g. following Hashimoto syndrome) stable on
                  hormone replacement;

               3. Any chronic skin condition that does not require systemic therapy;

               4. Patients without active disease in the last 5 years prior to Trial Registration
                  may be included but only after consultation with the CI or Coordinating
                  Investigator;

               5. Patients with coeliac disease controlled by diet alone;

         19. Active infection including tuberculosis (TB) (clinical evaluation that includes
             clinical history, physical examination and radiographic findings, and TB testing in
             line with local practice), hepatitis B (HBV; known positive HBV surface antigen
             (HBsAg) result), hepatitis C (HCV), or human immunodeficiency virus (HIV; positive HIV
             1/2 antibodies). Patients with a past or resolved HBV infection (defined as the
             presence of hepatitis B core antibody [anti-HBc] and absence of HBsAg) are eligible.
             Patients positive for HCV antibody are eligible only if polymerase chain reaction is
             negative for HCV RNA.

         20. Patients with a history of non-infectious pneumonitis.

        Inclusion Criteria for Trial Entry:

          1. Signed Informed Consent Form (ICF) for Trial Entry;

          2. Residual disease is confirmed as at least one viable disease focus ≥ 2cm on
             trial-specific dynamic contrast enhanced MRI scan performed 1 week following day 1 of
             the final cycle of NACT.

          3. Recovery from all acute adverse events of prior NACT to baseline or NCI CTCAE Grade
             ≤1, except for alopecia. Patients with irreversible toxicity not reasonably expected
             to be exacerbated by trial treatment may be included only after consultation with the
             CI or Coordinating Investigator

          4. Patients must have adequate haematological, renal and hepatic function as defined by:

               -  Haemoglobin (Hb) ≥ 10 g/dL (≥ 100 g/L) with no blood transfusion or
                  erythropoietin in the past 28 days

               -  Absolute neutrophil count (ANC) ≥ 1500/mm3 (≥ 1.5 x 109/L)

               -  Platelet count ≥100,000/mm3 (≥ 100 x 109/L)

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

               -  Aspartate aminotransferase (AST) (Serum Glutamic Oxaloacetic Transaminase (SGOT))
                  / Alanine aminotransferase (ALT) (Serum Glutamic Pyruvate Transaminase (SGPT)) ≤
                  2.5 x institutional ULN

               -  Calculated creatinine clearance ≥51 mL/min using the Cockcroft-Gault equation
                  (please refer to Appendix 4) or based on a 24 hour urine test

          5. Women of childbearing potential must have a confirmed menstrual period and a negative
             urinary or serum pregnancy test prior to trial entry. This should be repeated as
             applicable to ensure a negative pregnancy test is performed within 3 days prior to
             commencing trial treatment (or on the day of planned treatment for cohort C).

          6. Confirmation that all Trial Registration inclusion criteria remain satisfied.

        Exclusion Criteria for Trial Entry:

          1. History of clinically significant or uncontrolled cardiovascular disease including:

               -  Myocardial infarction within 6 months prior to Trial Entry;

               -  Uncontrolled angina within 3 months prior to Trial Entry;

               -  Congestive heart failure New York Heart Association (NYHA) class III or IV, or
                  patients with history of congestive heart failure NYHA class III or IV in the
                  past, unless an echocardiogram (ECHO) or multi-gated acquisition (MUGA) scan
                  performed within 3 months prior to Trial Entry results in a left ventricular
                  ejection fraction that is 45%;

               -  History of clinically significant ventricular arrhythmias (e.g. ventricular
                  tachycardia, ventricular fibrillation, torsades de pointes);

               -  History of Mobitz II second degree or third degree heart block without a
                  permanent pacemaker in place;

               -  Consistent evidence of hypotension as indicated by systolic blood pressure < 90
                  millimeters of mercury (mm Hg) prior to Trial Entry;

               -  Consistent evidence of bradycardia as indicated by a heart rate of < 50 beats per
                  minute on the ECG prior to Trial Entry;

               -  Consistent evidence of uncontrolled hypertension as indicated by systolic blood
                  pressure > 170 mm Hg or diastolic blood pressure > 105 mm Hg prior to Trial
                  Entry.

             Patients with a history of any of the above listed cardiac conditions judged not to be
             clinically significant by the local Investigator must be notified to the trial team at
             the ICR-CTSU;

          2. History of loss of consciousness or transient ischemic attack within 12 months prior
             to Trial Entry;

          3. Patients with Grade ≥2 neuropathy, as defined by the National Cancer Institute (NCI)'s
             Common Terminology Criteria for Adverse Events Version 5.0 (CTCAE v5.0) will be
             evaluated on a case-by-case basis after consultation with the CI or Coordinating
             Investigator;

          4. Major surgery (excluding minor procedures, e.g. placement of vascular access) within 2
             weeks prior to Trial Entry. Patients must have recovered from any effects of any major
             surgery prior to commencing trial treatment.

          5. Use of any investigational agent within 30 days prior to commencing trial treatment.

          6. Concomitant use of known strong CYP3A inhibitors (e.g. itraconazole, telithromycin,
             clarithromycin, protease inhibitors boosted with ritonavir or cobicistat, indinavir,
             saquinavir, nelfinavir, boceprevir, telaprevir) or moderate CYP3A inhibitors (eg.
             ciprofloxacin, erythromycin, diltiazem, fluconazole, verapamil). The required washout
             period prior to commencing trial treatment is 5 weeks;

          7. Concomitant use of known strong (eg. phenobarbital, enzalutamide, phenytoin,
             rifampicin, rifabutin, rifapentine, carbamazepine, nevirapine and St John's Wort) or
             moderate (eg. bosentan, efavirenz, modafinil) CYP3A inducers. The required washout
             period prior to commencing trial treatment is 5 weeks;

          8. Whole blood transfusions in the last 4 months prior to commencing trial treatment
             (packed red blood cells and platelet transfusions are acceptable, with no blood
             transfusion or erythropoietin in the past 28 days prior to trial entry);

          9. Current or prior use of immunosuppressive medication within 14 days prior to
             commencing trial treatment, with the exception of intranasal and inhaled
             corticosteroids or systemic corticosteroids at physiological doses, which are not to
             exceed 10 mg/day of prednisolone, or an equivalent corticosteroid.

         10. Receipt of live attenuated vaccine within 30 days prior to commencing trial treatment.

         11. Confirmation that none of the Trial Registration exclusion criteria listed in Section
             5.3.2 are met.