To Assess Safety and Efficacy of Agents Targeting DNA Damage Repair With Olaparib Versus Olaparib Monotherapy.

This is a prospective, open label, randomised, multi-centre Phase 2 study that will assess the efficacy and safety of olaparib monotherapy versus olaparib in combination with an inhibitor of ATR (Ceralasertib) and olaparib monotherapy versus olaparib in combination with an inhibitor of WEE1 (adavosertib) in second or third line setting in patients with TNBC prospectively stratified by presence/absence of qualifying tumour mutation in genes involved in the HRR pathway. Eligible patients will be randomised by a ratio 1:1:1 to treatment Arm 1: olaparib continuous in a 28-day cycle, Arm 2: Ceralasertib Days 1-7 with olaparib continuous in a 28-day cycle or Arm 3: adavosertib Days 1-3 and 8-10 with olaparib continuous in a 21-day cycle. Following the ISRC meeting on 17 April 2019 a recommendation was made to close the adavosertib+olaparib treatment arm across all biomarker strata. Following closure of this arm the randomisation ratio will be 1:1 to olaparib monotherapy or Ceralasertib+olaparib. Patients who were receiving treatment with adavosertib+olaparib treatment were offered the opportunity to continue treatment on olaparib monotherapy at the approved dose (300 mg bd). The study subject population will be divided into Stratum A (patients with mutations in BRCA1 or BRCA2 (Breast cancer susceptible gene mutation (BRCAm)), Stratum B (patients with mutations in any of the other genes involved in the HRR pathway and no mutation in BRCA1 and no mutation in BRCA2), and Stratum C (patients with no detected tumour mutations in any of the HRR genes). Within each stratum A, B and C, there will be further stratification by whether the patient received prior platinum-based therapy. In the olaparib monotherapy treatment arm as well as in the Ceralasertib+olaparib treatment arm, patients will be administered olaparib bd at 300 mg continuously. Two (2) 150 mg olaparib tablets will be taken at the same time each day, approximately 12 hours apart with one glass of water (approximately 250 mL). In the adavosertib+olaparib treatment arm, patients will be given olaparib 200 mg bd (2 x 100 mg tablets twice a day) and adavosertib 150 mg bd from Day 1 to Day 3 (inclusive) and Day 8 to Day 10 (inclusive) of every 21-day cycle. Ceralasertib will be supplied as 20 mg, 80 mg, or 100 mg film coated tablets. Patients will be administered Ceralasertib od at 160 mg from Day 1 to Day 7 (inclusive) of every 28-day cycle. A total of 160 mg of Ceralasertib tablets will be taken at the same time on each day of dosing with approximately 250 mL of water. Adavosertib will be supplied as capsules containing 25 mg, 50 mg, 75 mg, 100 mg, or 200 mg of drug substance. Adavosertib will be taken with approximately 250 mL of water approximately 2 hours before or 2 hours after food. Olaparib, Ceralasertib and adavosertib will be provided by AstraZeneca. Primary outcome measures (progression free survival \[PFS\]) will be analysed for the 3 patient populations BRCAm, Non BRCAm HRRm (Homologous Recombination Repair gene mutation) and Non HRRm. Secondary outcome measures will be analysed in 2 patient populations HRRm and All for PFS, Objective response rate (ORR) and overall survival (OS) will be analysed in all 5 patient populations. DoR, and tumour change will be analysed in BRCAm, Non BRCAm HRRm, and Non HRRm patient populations. Tumour and germline mutation status will be analysed only in the all patient population. PK outcome measures will be analysed only in the all patient population. Blinded Independent Central Review (BICR) of radiological imaging data will be carried out using RECIST version 1.1 and Investigator assessments will also be analysed for sensitivity purposes.