Background: Paclitaxel is commonly used as first-line chemotherapy for HER2-negative metastatic breast cancer (MBC) patients. However, with response rates of 21.5-53.7% and significant risk of peripheral neuropathy, there is need for better chemotherapy. Patients and methods: This open-label phase II/III trial randomised HER2-negative MBC patients 1:1 to either 6 cycles of three-weekly cabazitaxel (25 mg/m2), or, weekly paclitaxel (80 mg/m2) over 18 weeks. The primary endpoint was progression free survival (PFS). Secondary endpoints included objective response rate (ORR), time to response (TTR), overall survival (OS), safety and tolerability and quality of life (QoL). Results: 158 patients were recruited. Comparing cabazitaxel to paclitaxel, median PFS was 6.7 vs 5.8 months (HR 0.87; 80%CI 0.70-1.08, P = 0.4). There was no difference in median OS (20.6 vs 18.2 months, HR 1.00; 95%CI 0.69-1.45, P = 0.99), ORR (41.8% vs 36.7%) or TTR (HR 1.09; 95%CI 0.68-1.75, P = 0.7). Grade & GE;3 adverse events occurred in 41.8% on cabazitaxel and 46.8% on paclitaxel; the most common being neutropenia (16.5%) and febrile neutropenia (12.7%) cabazitaxel and neutropenia (8.9%) and lung infection (7.6%) paclitaxel. Peripheral neuropathy of any grade occurred in 54.5% paclitaxel vs 16.5% cabazitaxel. Mean EQ-5D-5L single index utility score (+0.05; 95%CI 0.004-0.09, P = 0.03) and visual analogue scale score (+7.7; 95%CI 3.1-12.3, P = 0.001) were higher in cabazitaxel vs paclitaxel. Conclusions: Three-weekly cabazitaxel in HER2-negative MBC does not significantly improve PFS compared to weekly paclitaxel, although it has a lower risk of peripheral neuropathy with better patient reported QoL outcomes. It is well tolerated and requires fewer hospital visits.

1024 Background: The plasmaMATCH trial was an open label platform trial, consisting of circulating tumour DNA (ctDNA) testing in ̃1000 patients with advanced breast cancer (ABC) linked to parallel treatment cohorts with therapies matched to mutations identified in ctDNA. Cohorts A-D have already reported (Turner N et al, Lancet Oncol 2020). Cohort E recruited patients with triple negative breast cancer (TNBC) without a targetable mutation identified at ctDNA screening, treating with olaparib (PARP inhibitor) plus ceralasertib (ATR inhibitor). Methods: Patients with TNBC who had received 1 or 2 lines of chemotherapy for advanced disease or relapsed within 12 months of (neo)adjuvant chemotherapy were eligible. Treatment was olaparib 300mg b.i.d continuously and ceralasertib 160mg qd on days 1–7 on a 28 day cycle, until disease progression. The primary endpoint was confirmed objective response rate by RECIST v1.1. Secondary endpoints included clinical benefit rate, progression-free survival (PFS) and safety. Biomarker analysis included response according to BRCA and somatic DNA repair gene status and ATM loss. Using a two-stage design with a target response rate of 25%, unacceptable response rate of 10%, alpha=2% and power=90%, ≥13 responses out of 69 evaluable stage 2 patients were required to infer efficacy (5/37 stage 1). Results: Between 17/09/18 and 5/10/20 75 patients enrolled in Cohort E of whom 70 were evaluable for response. The median age was 55.6 years. 42 (56%) patients had 1 and 13 (17.3%) had 2 prior line(s) of chemotherapy for metastatic disease. Efficacy is shown in Table. The most common grade ≥3 adverse events were: hypertension 12 (17%) and anaemia 9 (13%). Dose reductions and interruptions occurred in 19 (26.4%) and 34 (47.2%) patients respectively. Conclusions: The response rate to olaparib and ceralasertib did not meet pre-specified criteria for efficacy in the overall evaluable population. Responses were observed in patients without germline or somatic BRCA1/2 mutations. Translational analyses are underway to identify potential biomarkers of response in this population and will be presented at the meeting. Clinical trial information: ISRCTN16945804. [Table: see text]

1008 Background: Paclitaxel is commonly used as first line chemotherapy for HER2 negative MBC. However, with response rates of 21.5-53.7% and a significant risk of peripheral neuropathy there is a need for more effective and better tolerated chemotherapy (CCT). Methods: This open label randomised (1:1) phase 2 trial compared 6 cycles of cabazitaxel (25 mg/m2) every 3 weeks, with weekly paclitaxel (80mg/m2) over 18 weeks as first line CCT. HER2 negative and performance status ≤1 patients were eligible. Patients on cabazitaxel received GCSF prophylaxis. Primary endpoint was Progression Free Survival (PFS) with 127 events required to detect a hazard ratio (HR) of 0.65 with 85% power. Secondary endpoints included objective response rate (ORR; RECIST 1.1), time to response (TTR), overall survival (OS), safety and tolerability and quality of life (QoL). Results: 158 patients were recruited from 14 UK hospitals (79 in each arm). Median age (range) was 56(34-81) in the cabazitaxel arm and 61(34-79) in the paclitaxel arm. 61% of patients were performance status 0. Median time on treatment was 15 weeks for both arms, but more patients on paclitaxel had a treatment delay (61% vs 39%) or dose reduction (37% vs 24%). Comparing cabazitaxel to paclitaxel after 146 PFS events, median PFS was 6.7 vs 5.8 months (HR 0.84; 95%CI 0.60–1.18, P = 0.3). There was no difference in OS, median 19.3 vs 20.0 months (HR 0.94; 95%CI 0.63-1.40, P = 0.7), ORR (42% vs 37%) or TTR (HR 1.09; 95%CI 0.68–1.74, P = 0.7). Grade ≥3 adverse events occurred in 42% of patients on cabazitaxel and 48% on paclitaxel. Diarrhoea, febrile neutropenia and nausea were the most common grade ≥3 events in the cabazitaxel arm with rates of 11%, 11% and 10% respectively compared to 1%, 1% and 0% in the paclitaxel arm. In the paclitaxel arm the top grade ≥3 events were lung infection and peripheral neuropathy, 6% and 5% respectively compared to 2.5% and 0% in the cabazitaxel arm. Peripheral neuropathy of any grade was reported by 55% of patients treated with paclitaxel vs 17% on cabazitaxel. Alopecia occurred in 41% of patients on paclitaxel compared to 27% on cabazitaxel. Adverse events leading to discontinuation were more frequent with paclitaxel (22%) than cabazitaxel (14%). Over the course of treatment, mean EQ5D single index utility score (+0.05; 95%CI 0.004-0.09, P = 0.03) and visual analogue scale score (+7.7; 95%CI 3.1-12.3, P = 0.001) were higher in the cabazitaxel arm compared to paclitaxel suggestive of better QoL on Cabazitaxel. Conclusions: 3 weekly cabazitaxel as first line chemotherapy in HER2 negative MBC does not significantly improve PFS compared to weekly paclitaxel, though it has a lower risk of peripheral neuropathy with better patient reported overall health outcomes. Cabazitaxel is safe and well tolerated for MBC and requires fewer hospital visits, an important consideration in the COVID pandemic and beyond. Clinical trial information: NCT03048942 .

Background: Ligand binding domain ESR1 mutations are acquired in ER positive cancers during prior aromatase inhibitor therapy for advanced ER positive breast cancer (BC). ESR1 mutant cancer models are sensitive to fulvestrant at high concentrations, however standard dose fulvestrant may not achieve the concentration required to fully inhibit mutant ESR1 in the clinic. The plasmaMATCH trial Cohort A assessed the efficacy of extended-dose fulvestrant (double the current standard dose achieved by doubling the frequency of administration) in patients with an ESR1 mutation identified via ctDNA testing. Methods: The plasmaMATCH trial was an open-label, multi-centre, multi-cohort platform trial, consisting of ctDNA testing in ~1000 patients with advanced BC. Patients with an ESR1 mutation identified in ctDNA testing were potentially eligible to enter Cohort A. Patients were treated with fulvestrant 500mg intramuscularly on Cycle 1 Days 1, 8 and 15 of a 28 day cycle, and from Cycle 2 onwards every 15 days. Pharmacokinetics samples were collected pre-dose on Day 1 of Cycles 2, 3 and 4. The primary endpoint for Cohort A was confirmed objective response rate as defined by RECIST v1.1. The original planned sample size was 40 patients, to detect a 25% response rate, assuming predominantly clonally dominant mutations. As the trial progressed it became apparent that ctDNA screening may also detect sub clonal ESR1 mutations, which were expected to have a lower response rate. Using a single-stage A’Hern design with a target response rate of 20%, unacceptable response rate of 10%, alpha=5%, power=80, the sample size was increased to 78 evaluable patients with 13 or more responses required to infer efficacy. Results: Following ctDNA testing, 84 patients enrolled in Cohort A (38% of patients with ESR1 mutations identified in ctDNA testing). All were ER positive, seven were HER2 amplified, 78 (93%) had visceral metastases. The most common ESR1 mutations detected in baseline plasma were D538G (52.4%), Y537S (35.7%), E380Q (33.3%). In the 74 evaluable patients, confirmed response rate was 8.1% (95%CI 3.0-16.8%, 6/74). One additional patient had an unconfirmed partial response. Median progression free survival was 2.2 months (IQR 1.7-5.3 months) and median duration of response was 7.0 months (IQR 3.7-8.3 months) with 4 patients continuing on treatment. In exploratory analysis, 39 patients had clonally dominant ESR1 mutations in baseline ctDNA analysis whilst 25 patients had subclonal mutations and 10 had unknown clonality. The response rate in those with clonally dominant ESR1 mutations was 10% (95%CI: 2.9-24.2%, 4/39) with no confirmed responses in those with subclonal mutations. The most common clinically significant grade 3 or 4 adverse event was hypertension (13%). Pharmacokinetic analysis was consistent with elevated fulvestrant exposure compared to approved 500mg PopPk model (pre-dose Cycle 3, 71% increase, and pre-dose Cycle 4 66% increase). Conclusion: In the pre-treated population studied, the response rate of extended-dose fulvestrant did not meet pre-specified criteria for efficacy in patients with ESR1 mutations identified in ctDNA testing. Extended-dose fulvestrant was well tolerated and enhanced exposure was observed. Assessment of clonal dominance of ESR1 mutations in ctDNA may identify patients who are more likely to benefit from extended-dose fulvestrant therapy. Citation Format: Iain Macpherson, Lucy Kilburn, Sarah Kernaghan, Andrew M Wardley, Richard D Baird, Rebecca Roylance, Peter Stephens, Olga Oikonomidou, Jeremy P Braybrooke, Mark Tuthill, Jacinta Abraham, Matthew C Winter, Belinda Kingston, Katie Wilkinson, Alistair Ring, Judith M Bliss, Nicholas Turner, on behalf of the plasmaMATCH Trial Management Group. Results from plasmaMATCH trial treatment cohort A: A phase II trial of extended-dose fulvestrant in patients with an ESR1 mutation identified via ctDNA screening (CRUK/15/010) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-04.

Background Circulating tumour DNA (ctDNA) testing might provide a current assessment of the genomic profile of advanced cancer, without the need to repeat tumour biopsy. We aimed to assess the accuracy of ctDNA testing in advanced breast cancer and the ability of ctDNA testing to select patients for mutation-directed therapy. Methods We did an open-label, multicohort, phase 2a, platform trial of ctDNA testing in 18 UK hospitals. Participants were women (aged >= 18 years) with histologically confirmed advanced breast cancer and an Eastern Cooperative Oncology Group performance status 0-2. Patients had completed at least one previous line of treatment for advanced breast cancer or relapsed within 12 months of neoadjuvant or adjuvant chemotherapy. Patients were recruited into four parallel treatment cohorts matched to mutations identified in ctDNA: cohort A comprised patients with ESR1 mutations (treated with intramuscular extended-dose fulvestrant 500 mg); cohort B comprised patients with HER2 mutations (treated with oral neratinib 240 mg, and if oestrogen receptor-positive with intramuscular standard-dose fulvestrant); cohort C comprised patients with AKT1 mutations and oestrogen receptor-positive cancer (treated with oral capivasertib 400 mg plus intramuscular standard-dose fulvestrant); and cohort D comprised patients with AKT1 mutations and oestrogen receptor-negative cancer or PTEN mutation (treated with oral capivasertib 480 mg). Each cohort had a primary endpoint of confirmed objective response rate. For cohort A, 13 or more responses among 78 evaluable patients were required to infer activity and three or more among 16 were required for cohorts B, C, and D. Recruitment to all cohorts is complete and long-term follow-up is ongoing. This trial is registered with ClinicalTrials.gov, NCT03182634; the European Clinical Trials database, EudraCT2015-003735-36; and the ISRCTN registry, ISRCTN16945804. Findings Between Dec 21, 2016, and April 26, 2019, 1051 patients registered for the study, with ctDNA results available for 1034 patients. Agreement between ctDNA digital PCR and targeted sequencing was 96-99% (n=800, kappa 0.89-0.93). Sensitivity of digital PCR ctDNA testing for mutations identified in tissue sequencing was 93% (95% CI 83-98) overall and 98% (87-100) with contemporaneous biopsies. In all cohorts, combined median follow-up was 14.4 months (IQR 7.0-23.7). Cohorts B and C met or exceeded the target number of responses, with five (25% [95% CI 9-49]) of 20 patients in cohort B and four (22% [6-48]) of 18 patients in cohort C having a response. Cohorts A and D did not reach the target number of responses, with six (8% [95% CI 3-17]) of 74 in cohort A and two (11% [1-33]) of 19 patients in cohort D having a response. The most common grade 3-4 adverse events were raised gamma-glutamyltransferase (13 [16%] of 80 patients; cohort A); diarrhoea (four [25%] of 20; cohort B); fatigue (four [22%] of 18; cohort C); and rash (five [26%] of 19; cohort D). 17 serious adverse reactions occurred in 11 patients, and there was one treatment-related death caused by grade 4 dyspnoea (in cohort C). Interpretation ctDNA testing offers accurate, rapid genotyping that enables the selection of mutation-directed therapies for patients with breast cancer, with sufficient clinical validity for adoption into routine clinical practice. Our results demonstrate clinically relevant activity of targeted therapies against rare HER2 and AKT1 mutations, confirming these mutations could be targetable for breast cancer treatment. Copyright (C) 2020 The Author(s). Published by Elsevier Ltd.

Background: Activation of the AKT pathway can result from diverse rare genetic events, including mutation of AKT1, AKT2/3 E17K, and through inactivating mutation or homozygous deletion of PTEN. AKT1 mutations and genetic loss of PTEN are associated with activation of AKT signalling and selective sensitivity to AKT inhibition in pre-clinical models. Capivasertib is a potent catalytic inhibitor of AKT1, AKT2 and AKT3 with activity both in vivo and in the clinic. The plasmaMATCH trial assessed the efficacy of capivasertib in BC patients with rare AKT activating mutations. Methods: The plasmaMATCH trial is an open-label, multi-centre, multi-cohort platform trial, consisting of ctDNA testing in ~1000 patients with advanced BC. Patients with AKT1 mutations in ER negative BC; or AKT2/3 E17K mutations, PIK3R1 or PTEN inactivating mutations orhomozygous deletion of PTEN in both ER positive and ER negative BC were recruited. Mutations were identified in ctDNA testing in plasmaMATCH or in prior tumour sequencing. Patients were treated with capivasertib 480mg BID 4 days on - 3 days off. The primary endpoint for Cohort D is confirmed objective response rate as defined by RECIST v1.1. Using a single stage A’Hern design with a target response rate of 25%, unacceptable response rate of 5%, alpha=5% and power=80%, at least 3 responses out of 16 evaluable patients were required to infer efficacy for capivasertib. Results: In total 19 patients were recruited in Cohort D, 12 following ctDNA testing and 7 on tumour testing. Fifteen (79%) were ER positive, all were HER2 non-amplified, and 14 (74%) had visceral metastases. Mutations were AKT1 E17K (5 patients), AKT1 L52R (1), PTEN inactivating mutation (12), and PTEN homozygous deletion (1). All patients were evaluable with overall confirmed response rate of 10.5% (95%CI 1.3-33.1%, 2/19) (first 16 evaluable patients: 2/16, 12.5% (95%CI 1.6-38.3)). Two further patients had unconfirmed responses. Median progression free survival was 3.4 months (IQR 1.8-5.5 months) and median duration of response 3.9 months (IQR 3.7-4.2 months) with 1 patient continuing treatment. In patients with AKT1 mutations there was a 33% response rate (2/6) with 2 further unconfirmed responses. There were no responses in patients with PTEN mutations (0/13). The most common clinically significant grade 3 or 4 adverse events were rash (26%), hypertension (11%), transaminase increase (11%) and vomiting (11%). Conclusions: Capivasertib monotherapy did not meet pre-specified criteria for efficacy in this group of patients with a range of AKT pathway activating mutations. In exploratory analysis, capivasertib was active in patients with AKT1 mutations. Citation Format: Richard D Baird, Lucy Kilburn, Sarah Kernaghan, Andrew M Wardley, Iain Macpherson, Rebecca Roylance, Peter Stephens, Olga Oikonomidou, Jeremy P Braybrooke, Mark Tuthill, Jacinta Abraham, Matthew C Winter, Belinda Kingston, Katie Wilkinson, Nicholas Turner, Alistair Ring, Judith M Bliss, on behalf of the plasmaMATCH Trial Management Group. Results from plasmaMATCH trial treatment cohort D: A phase II trial of capivasertib in patients with an AKT activation basket mutation identified via ctDNA testing or tumour sequencing (CRUK/15/010) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-14.

Abstract Background: HER2 mutations occur in approximately 3% of HER2 non-amplified cancers and include missense substitutions and indels within the tyrosine kinase domain resulting in oncogenic HER2 activation. Neratinib, an irreversible EGFR, HER2 and ERBB4 tyrosine kinase inhibitor, has demonstrated activity in pre-clinical HER2 mutant models, and in a prior phase I trial with HER2 mutations identified through tumour testing. The plasmaMATCH trial Cohort B assessed the efficacy of neratinib in BC patients with a HER2 mutation identified in ctDNA testing. Methods: The plasmaMATCH trial was an open-label, multi-centre, multi-cohort platform trial, consisting of ctDNA testing in ~1000 patients with advanced BC. Patients with a HER2 mutation identified via ctDNA testing were registered to Cohort B. Patients were treated with 240mg neratinib once daily. Patients with ER positive BC were also treated with fulvestrant 500mg intramuscularly on Cycle 1 Days 1 and 15, and Cycle 2 onwards every 28 days. The primary endpoint for Cohort B was confirmed objective response rate as defined by RECIST v1.1. Using a single stage A’Hern design with a target response rate of 25%, unacceptable response rate of 5%, alpha=5% and power=80%, at least 3 responses out of 16 evaluable patients were required to infer efficacy. Results: Following ctDNA testing, 21 patients enrolled in Cohort B (58% of patients with HER2 mutations identified in ctDNA testing). Eighteen (86%) were ER positive, 2 (10%) were HER2 amplified, and 18 (86%) had visceral metastases. The most common HER2 mutations detected in baseline plasma were L755S (47.6%), V777L (19%), and S310F (14.3%). In the 20 evaluable patients, confirmed response rate was 25.0% (95%CI 8.7-49.1%, 5/20) (first 16 evaluable patients: 4/16, 25.0% (95%CI 7.3-52.4)). One patient had a complete response, ongoing at 29 months duration, and three additional patients had unconfirmed partial responses. Median progression free survival was 5.4 months (IQR 3.4-9.1) and median duration of response was 5.7 months (IQR 3.7-9.7 months) with 3 patients continuing on treatment. The most common clinically significant grade 3 or 4 adverse events were diarrhoea (20%) and hypertension (15%). Conclusions: Neratinib, with or without fulvestrant, was active in advanced BC patients with HER2 mutations identified in ctDNA testing, meeting the pre-specified threshold for efficacy. Citation Format: Andrew M Wardley, Lucy Kilburn, Sarah Kernaghan, Iain Macpherson, Richard D Baird, Rebecca Roylance, Peter Stephens, Olga Oikonomidou, Jeremy P Braybrooke, Mark Tuthill, Jacinta Abraham, Matthew C Winter, Belinda Kingston, Katie Wilkinson, Judith M Bliss, Alistair Ring, Nicholas Turner, on behalf of the plasmaMATCH Trial Management Group. Results from plasmaMATCH trial treatment cohort B: A phase II trial of neratinib plus fulvestrant in ER positive breast cancer or neratinib alone in ER negative breast cancer in patients with a HER2 mutation identified via ctDNA screening (CRUK/15/010) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-07.

Abstract Background: Circulating tumour DNA (ctDNA) testing may provide a more current assessment of the genetic profile of advanced breast cancer (BC) compared with analysis of the primary tumour, with repeat advanced disease biopsy conducted infrequently in routine clinical practice. The plasmaMATCH trial was designed to assess the clinical utility of using ctDNA testing to select patients for targeted therapies. Methods: The plasmaMATCH trial was an open-label, multi-centre, multi-cohort platform trial, consisting of ctDNA testing in ~1000 patients with advanced BC, with patients recruited into four parallel treatment cohorts with therapies matched to mutations identified in ctDNA (A: ESR1 mutation - extended-dose fulvestrant 500mg every 2 weeks, B: HER2 mutation - neratinib +/- fulvestrant (standard dosing), C: AKT1 in ER positive BC -capivasertib + fulvestrant (standard dosing), D: AKT1 in ER negative BC or PTEN inactivating mutation - capivasertib). A fifth cohort (E) recruited patients with triple negative BC with no actionable mutation to receive olaparib + AZD6738, and will be reported separately. Each cohort had a specific phase II single arm design. ctDNA testing was conducted with two technologies: digital droplet PCR (ddPCR) at a central laboratory prospectively in all patients, and error corrected sequencing with Guardant360 prospectively from part-way through recruitment and retrospectively for the remaining patients. Tumour sequencing from an advanced disease biopsy was conducted retrospectively, not influencing cohort entry. The primary endpoint for Cohorts A-D is confirmed objective response rate by RECIST v1.1. Secondary endpoints include clinical benefit rate, progression-free survival, safety and frequency of mutations identified in ctDNA screening. Results: Entry into ctDNA testing for Cohorts A-D was closed on 26/Apr/2019 with 1044 patients registered. ctDNA screening results were received for 1033 patients (99%), with 142 patients entered into Cohorts A-D (A 84, B 21, C 18, D 19). Agreement between ctDNA digital PCR and sequencing results was high (individual gene level agreement 95.5%-99.4%, kappa 0.89-0.93). Predefined efficacy criteria were met in Cohorts B (neratinib for HER2 mutations) and C (capivasertib for AKT mutations), with exploratory analysis of Cohort D identifying activity of capivasertib in AKT1 mutations (Table 1). Efficacy criteria were not met in Cohort A (extended-dose fulvestrant for ESR1 mutations). Adverse events were consistent with prior reports, with extended-dose fulvestrant well tolerated. Table 1: Efficacy results from plasmaMATCHMutationCohortConfirmed response rate, % (95%CI; n/N)Median PFS (IQR), monthsAll patientsFirst 16 evaluable patients*ESR1A8.1% (3.0-16.8; 6/74)-2.2 (1.7-5.3)HER2B25.0% (8.7-49.1; 5/20)25.0% (7.3-52.4; 4/16)5.4 (3.4-9.1)AKT1C22.2% (6.4-47.6; 4/18)18.8% (4.0-45.6; 3/16)10.2 (3.2-18.2)AKT basketD10.5% (1.3-33.1; 2/19)12.5% (1.6-38.3; 2/16)3.4 (1.8-5.5)AKT133.3% (4.3-77.7; 2/6)--PTEN0 % (0/13)--*Predefined cohort efficacy thresholds for response were set: 13/78 (A); 3/16 (B, C, D) Conclusion: Circulating tumour DNA testing offers accurate tumour genotyping, sufficient for routine clinical practice. This approach can be used to identify patients with rare HER2 and AKT1 mutations, who have clinically relevant response rates with matched targeted therapies. Citation Format: Nicholas Turner, Belinda Kingston, Lucy Kilburn, Sarah Kernaghan, Andrew M Wardley, Iain Macpherson, Richard D Baird, Rebecca Roylance, Peter Stephens, Olga Oikonomidou, Jeremy P Braybrooke, Mark Tuthill, Jacinta Abraham, Matthew C Winter, Hannah Bye, Michael Hubank, Claire Snowdon, Daniel Rea, David Cameron, Abeer Shaaban, Katrina Randle, Katie Wilkinson, Laura Moretti, Judith M Bliss, Alistair Ring, on behalf of the plasmaMATCH Trial Management Group. Results from the plasmaMATCH trial: A multiple parallel cohort, multi-centre clinical trial of circulating tumour DNA testing to direct targeted therapies in patients with advanced breast cancer (CRUK/15/010) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr GS3-06.

Abstract Background: AKT1 mutation occurs in approximately 3% of breast cancer (BC), enriched in advanced BC. The AKT1 E17K mutation results in constitutive activation of AKT1, associated with sensitivity to AKT inhibitor capivasertib in pre-clinical models, and in a prior phase I trial with AKT1 mutations identified through tumour testing. The plasmaMATCH trial Cohort C assessed the efficacy of capivasertib and fulvestrant in ER positive BC patients with an AKT1 mutation in ctDNA testing. Methods: The plasmaMATCH trial was an open-label, multi-centre, multi-cohort platform trial, consisting of ctDNA testing in ~1000 patients with advanced BC. Patients with an AKT1 mutation identified via ctDNA testing were registered to Cohort C. Patients were treated with capivasertib 400mg BID 4 days on - 3 days off, plus fulvestrant 500mg intramuscularly on Cycle 1 Days 1 and 15, and Cycle 2 onwards every 28 days. The primary endpoint for Cohort C was confirmed objective response rate as defined by RECIST v1.1. Using a single stage A’Hern design with a target response rate of 25%, unacceptable response rate of 5%, alpha=5% and power=80%, at least 3 responses out of 16 evaluable patients were required to infer efficacy. Results: Following ctDNA testing, 18 patients enrolled in Cohort C (42% of patients with AKT1 mutations identified in ctDNA testing). All were ER positive, 1 (5.6%) was HER2 amplified, and 17 (94%) had visceral metastases. Mutation was AKT1 E17K in 17 patients and AKT1 L52R in 1 patient. All patients were evaluable with a confirmed response rate of 22.2% (95%CI 6.4-47.6%, 4/18) (first 16 evaluable patients: 3/16, 18.8% (95%CI 4.0-45.6)). A further 4 patients had an unconfirmed partial response. Median progression free survival was 10.2 months (IQR 3.2-18.2 months) and the median duration of response was 7.5 months (IQR 4.1-9.8 months) with 4 patients continuing on treatment. The most common clinically significant grade 3 or 4 adverse events were fatigue (22%), rash (17%), diarrhoea (11%) and hyperglycaemia (11%). Conclusions: Capivasertib plus fulvestrant was active in patients with ER positive breast cancer and AKT1 mutations identified in ctDNA testing, meeting the pre-specified threshold for efficacy Citation Format: Rebecca Roylance, Lucy Kilburn, Sarah Kernaghan, Andrew M Wardley, Iain Macpherson, Richard D Baird, Peter Stephens, Olga Oikonomidou, Jeremy P Braybrooke, Mark Tuthill, Jacinta Abraham, Matthew C Winter, Belinda Kingston, Katie Wilkinson, Alistair Ring, Judith M Bliss, Nicholas Turner, on behalf of the plasmaMATCH Trial Management Group. Results from plasmaMATCH trial treatment cohort C: A phase II trial of capivasertib plus fulvestrant in ER positive breast cancer patients with an AKT1 mutation identified via ctDNA screening (CRUK/15/010) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-11.

Background: Circulating tumor DNA (ctDNA) testing may provide a contemporary assessment of the genomic profile of advanced cancer, without need to repeat tumor biopsy. The plasmaMATCH trial was designed to assess the clinical utility of using ctDNA testing to select advanced breast cancer patients for targeted treatment. Methods: plasmaMATCH is an open label, multi-center, multi-cohort platform trial of ctDNA testing in ~1000 patients with advanced breast cancer, with patients recruited into four parallel treatment cohorts matched to mutations identified in ctDNA: A:ESR1 mutation, B:HER2 mutation, C:AKT1 mutation (ER-positive cancer), D:AKT activation basket (AKT1 mutation ER-negative cancer or PTEN mutation). ctDNA testing was conducted with digital PCR and error-corrected targeted sequencing. Tumour sequencing from an advanced disease biopsy was conducted retrospectively, not influencing cohort entry. Each cohort had a phase II single-arm design with primary endpoint of confirmed objective response rate using RECISTv1.1 in evaluable patients. Findings: 1051 patients registered, with ctDNA testing results available for 1034 patients. Agreement between ctDNA digital PCR and targeted sequencing was 95.5%-99.4% (n=800, kappa 0.89-0.93). ctDNA testing had 93-98% sensitivity for mutations identified in tissue sequencing. In patients with HER2 mutations, response rate with neratinib, plus fulvestrant in ER-positive cancer, was 25.0% (5/20, 95%CI 8.7-49.1%). In patients with AKT1 mutations and ER-positive cancer, response rate with capivasertib plus fulvestrant was 22.2% (4/18, 95%CI 6.4-47.6%). In patients with AKT1 mutations and ER-negative cancer, 33.3% (2/6, 95%CI,4.3-77.7) responded to capivasertib, although 0/13 patients with PTEN mutation responded. Response rate of ESR1 mutations with extended-dose fulvestrant was 8.1% (6/74, 95%CI 3.0-16.8%). Adverse events were consistent with prior reports. Interpretation: ctDNA testing offers accurate, rapid genotyping that enables the selection of patients for mutation-directed therapies. Our results demonstrate clinically relevant activity of targeted therapies against rare HER2 and AKT1 mutations.Trial Registration: ISRCTN16945804 ClinicalTrials.gov Identifier: NCT03182634 Funding: Cancer Research UK (CRUK/15/010,C30746/A19505), AstraZeneca, and Puma Biotechnology.Declaration of Interests: NCT, AR, JMB, LSK, CS, LM, SK, KW, SM, HB, MH, BK and RC report grants from Cancer Research UK, grants and non-financial support in the form of study drug provision from AstraZeneca and Puma Biotechnology and non-financial support in the form of ctDNA sequencing from Guardant Health and provision of reagents from BioRad during the conduct of the study. NCT also reports grants and personal fees from AstraZeneca, Pfizer, and Roche/Genentech, personal fees from Bristol-Myers Squibb, Lilly, MSD, Novartis, Bicycle Theraputics, Taiiho, Zeno Pharmaceuticals and Repare Therapeutics and grants from BioRad, Clovis, Merck Sharpe and Dohme, and Guardant Health outside the submitted work. BK also reports personal fees from Guardant Health outside the submitted work. AMW reports personal fees from Roche, personal fees and other support from Novartis, Pfizer, Lilly, Daiichi-Sankyo, MSD, AstraZeneca, Athenex and other support from Seattle Genetics, Andrew Wardley Ltd, Manchester Cancer Academy and Outreach Research and Innovation Group Limited outside the submitted work. IRM reports personal fees and non-financial support from Roche Products UK Ltd, Eli Lilly and Eisai and personal fees from Novartis, Pfizer, Daichi Sankyo, Genomic Health, Pierre Fabre and MSD outside the submitted work. RDB reports grants from AstraZeneca and Roche/Genentech outside the submitted work. RR reports personal fees from Novartis, Eli-Lilly and Pfizer, personal fees and non-financial support from Daiichi Sankyo and G1Therapeutics and non-financial support from Roche and AstraZeneca outside the submitted work. PS reports personal fees from Novartis, Eisai and Daiichi Sankyo outside the submitted work.OO reports grants and personal fees from Pfizer and Eisai, personal fees from Roche/GNE and Tesaro, non-financial support from AstraZeneca, personal fees and non-financial support from Eli Lilly, grants from Novartis outside the submitted work. MT reports personal fees from Pfizer, Novartis, Roche, Vaccitech, Oxford Vacmedix, Lilly, Astellas, Genomic Health and Esai, personal fees and non-financial support from Janssen, BMS, Ipsen and non-financial support from EUSA Pharma outside the submitted work. JA reports grant and personal fees from Eisai and personal fees from Merck outside the submitted work. MCW reports personal fees and non-financial support from Easai, Lilly and Roche and personal fees from Pfizer, Genomic Health and Novartis outside the submitted work. HB also reports personal fees from AstraZeneca outside of the submitted work. MH also reports personal fees from Bristol Myers Squibb, Boehringer Ingelheim, Roche Diagnostics and Eli Lilly during the conduct of the study. AS reports grants from Ventana Roche and Genomic Heath, personal fees from Daiichi Sankyo, Hologic, Genomic Health and Ventana Roche outside the submitted work. JMB also reports grants and non-financial support from AstraZeneca, Novartis, Janssen-Cilag, Merck Sharpe & Dohme, Pfizer, Roche, and Clovis Oncology and grants from Medivation outside the submitted work. AR also reports personal fees from Roche Products Limited, Pfizer, Novartis, Lilly and MSD outside the submitted work. JPB, HG, DR, DC and KR have nothing to disclose.Ethics Approval Statement: The study was co-sponsored by The Institute of Cancer Research and the Royal Marsden NHS Foundation Trust and approved by a Research Ethics Committee (16/SC/0271). All participants gave written informed consent prior to registration for ctDNA testing, and again prior to treatment cohort entry. Safety and efficacy data were reviewed regularly by an Independent Data Monitoring Committee (IDMC). Trial oversight was provided by an independent Trial Steering Committee.

Background This phase 1 study examined the safety, maximum-tolerated dose (MTD) and antitumour activity of E7449, a novel PARP 1/2 and tankyrase 1/2 inhibitor. Methods E7449 was orally administered once daily in 28-day cycles to patients with advanced solid tumours (50–800-mg doses). Archival tumour samples from consenting patients were evaluated for the expression of 414 genes in a biomarker panel (2X-121 drug-response predictor [DRP]) found to be predictive of the response to E7449 in cell lines. Results Forty-one patients were enrolled (13 pancreatic, 5 ovarian, 4 each with breast, lung or colorectal cancer and 11 with other tumour types). The most common grade ≥3 treatment-related adverse event was fatigue ( n = 7, 17.1%). Five patients experienced a dose-limiting toxicity (fatigue, n = 4, 800 mg; anaphylaxis, n = 1, 600 mg) for an MTD of 600 mg. E7449 exhibited antitumour activity in solid tumours, including 2 partial responses (PRs), and stable disease (SD) in 13 patients, which was durable (>23 weeks) for 8 patients. In 13 patients, the 2X-121 DRP identified those achieving PR and durable SD. E7449 showed good tolerability, promising antitumour activity and significant concentration-dependent PARP inhibition following 50–800-mg oral dosing. Conclusion The results support further clinical investigation of E7449 and its associated biomarker 2X-121 DRP. Clinical trial registration www.ClinicalTrials.gov code: NCT01618136.

2505 Background: A phase I study was done to establish the safety, MTD and anti-tumour efficacy of the novel PARP 1/2 and Tankyrase 1/2 inhibitor, 2X-121 (E7449). A novel tumor agnostic molecular biomarker, 2X-121 DRP, was developed to identify responders and non-responders. Methods: Patients (pts) with advanced solid tumors were eligible. 2X-121 was administered orally, once daily (QD), continuously. Archival tumor samples were obtained from consenting patients. Following completion of the study the 2X-121 DRP was applied in a blinded manner following a pre-specified analysis plan. This biomarker is based on expression of 414 genes predictive of response to 2X-121. Results: 41 pts were treated at 6 dose levels: 50, 100, 200, 400, 800 and 600 mg QD. Tumor types were pancreatic (n = 13), ovarian (n = 5), breast (4), lung (n = 4), colorectal (n = 4) and other (n = 11). Fatigue is the dose limiting toxicity. The MTD is 600 mg QD. The most frequently reported ( > 30% of pts) TEAEs were fatigue, chromaturia, decreased appetite, nausea, diarrhea, constipation, and vomiting. No significant hematological toxicity and no Gr4 or 5 AEs were reported. Two pts had partial response (PR, both ovarian cancer), 13 pts had stable disease (SD), with 8 of these > 24 weeks; 7/8 were pancreatic cancer pts. Sustained PARP inhibition of ~90% is seen at doses over 600mg QD in PBMCs. The 2X-121 DRP was applied to 13 patients from which adequate biopsy material was available evaluating the 414 gene signature. Patients with PR and durable SD were correctly identified. It divided patients in two groups, sensitive (N = 6) or resistant (N = 7) to 2X-121. The median time to progression was 296 and 155 days, respectively (HR = 0.29, P = 0.14). Overall survival (OS) differed between the two groups, with a median survival in excess of 800 days and 208 days, respectively (HR = 0.26, P = 0.07). Conclusions: 2X-121 was generally well tolerated at the MTD of 600 mg QD, with evidence of antitumor activity. The 2X-121 DRP predicted the responders irrespective of BRCA mutation status. Clinical trial information: NCT01618136.

The manufacturer of olaratumab (Lartruvo®), Eli Lilly & Company Limited, submitted evidence for the clinical and cost effectiveness of this drug, in combination with doxorubicin, for untreated advanced soft tissue sarcoma (STS) not amenable to surgery or radiotherapy, as part of the National Institute for Health and Care Excellence (NICE) Single Technology Appraisal process. The Peninsula Technology Assessment Group, commissioned to act as the Evidence Review Group (ERG), critically reviewed the company’s submission. Clinical effectiveness evidence for the company’s analysis was derived from an open-label, randomised controlled trial, JGDG. The analysis was based on a partitioned survival model with a time horizon of 25 years, and the perspective was of the UK National Health Service (NHS) and Personal Social Services. Costs and benefits were discounted at 3.5% per year. Given the available evidence, olaratumab is likely to meet NICE’s end-of-life criteria. To improve the cost effectiveness of olaratumab, the company offered a discount through a Commercial Access Agreement (CAA) with the NHS England. When the discount was applied, the mean base-case and probabilistic incremental cost-effectiveness ratios (ICERs) for olaratumab plus doxorubicin versus the standard-of-care doxorubicin were £46,076 and £47,127 per quality-adjusted life-year (QALY) gained, respectively; the probability of this treatment being cost effective at the willingness-to-pay threshold of £50,000 per QALY gained, applicable to end-of-life treatments, was 0.54. The respective ICERs from the ERG’s analysis were approximately £60,000/QALY gained, and the probability of the treatment being cost effective was 0.21. In August 2017, the NICE Appraisal Committee recommended olaratumab in combination with doxorubicin for this indication for use via the UK Cancer Drugs Fund under the agreed CAA until further evidence being collected in the ongoing phase III trial—ANNOUNCE—becomes available in December 2020.

Radiation‐induced DNA damage activates the DNA damage response (DDR). DDR up‐regulation may predict radio‐resistance and increase the risk of early local recurrence despite radiotherapy in early stage breast cancers. In 1755 early stage breast cancers, DDR signalling [ATM, ATR, total Ckh1, Chk1 phosphorylated at serine345 (pChk1), Chk2, p53], base excision repair [PARP1, POLβ, XRCC1, FEN1, SMUG1], non‐homologous end joining (Ku70/Ku80, DNA‐PKcs) and homologous recombination [RAD51, BRCA1, γH2AX, BLM, WRN, RECQL5, PTEN] protein expression was correlated to time to early local recurrence. Pre‐clinically, radio‐sensitization by inhibition of Chk1 activation by ATR inhibitor (VE‐821) and inhibition of Chk1 (V158411) were investigated in MDA‐MB‐231 (p53 mutant) and MCF‐7 (p53 wild‐type) breast cancer cells. In the whole cohort, 208/1755 patients (11.9%) developed local recurrence of which 126 (61%) developed local recurrence within 5 years of initiation of primary therapy. Of the 20 markers tested, only pChk1 and p53 significantly associated with early local recurrence (p value = 0.015 and 0.010, respectively). When analysed together, high cytoplasmic pChk1‐nuclear pChk1 (p = 0.039), high cytoplasmic pChk1‐p53 (p = 0.004) and high nuclear pChk1‐p53 (p = 0.029) co‐expression remain significantly linked to early local recurrence. In multivariate analysis, cytoplasmic pChk1 level independently predicted early local recurrence (p = 0.025). In patients who received adjuvant local radiotherapy (n = 949), p53 (p = 0.014) and high cytoplasmic pChk1‐p53 (p = 0.017) remain associated with early local recurrence. Pre‐clinically, radio‐sensitisation by VE‐821 or V158411 was observed in both MCF‐7 and MDA‐MB‐231 cells and was more pronounced in MCF‐7 cells. We conclude that pChk1 is a predictive biomarker of radiotherapy resistance and early local recurrence.

Background: Chk1 inhibitors are currently under clinical evaluation as single agents and in combination with cytotoxic chemotherapy. Understanding determinants of sensitivity and novel combinations is critical for further clinical development. Potentiation of mTOR inhibitor cytotoxicity by the Chk1 inhibitor V158411 was determined in p53 mutant colon cancer cells. DNA damage response, expression levels of repair proteins, cell cycle effects and the contribution of alternative DSB repair pathways were further evaluated by western blotting and high content analysis. Results: mTOR inhibitors AZD8055, RAD‐001, rapamycin and BEZ235 induced synergistic cytotoxicity with the Chk1 inhibitor V158411 in p53 mutant colon cancer cells. Reduced FANCD2, RAD51 and RPA70, core proteins in homologous recombination repair (HRR) and interstrand crosslink repair (ICLR), following inhibition of mTOR was associated with increased V158411 induced DSBs and caspase 3‐independent cell death. Dual mTOR and Chk1 inhibition activated DNA‐PKcs. Cells defective in DNA‐PKcs exhibited increased resistance to V158411 with Chk1 expression closely correlated to DNA‐PKcs expression in various types of cancer. Conclusions: Down regulation of proteins involved in HRR or ICLR by mTOR inhibitors is associated with increased sensitivity of human tumours to Chk1 inhibitors such as V158411. High levels of DNA‐PKcs may be a potential biomarker to stratify patients to Chk1 inhibitor therapy alone or in combination with mTOR inhibitors.

Aim: E7449 is an orally bioavailable, brain penetrable, potent small-molecule inhibitor of poly (ADP-ribose) polymerase (PARP) 1 and PARP 2 with an IC50 of 1.0 and 1.2 nmol/L respectively. E7449 is a poor P-gp substrate. Preclinically, E7449 potentiates the antitumour activity of chemotherapy and radiotherapy and has activity as a single-agent in BRCA-deficient and other tumours. A Phase 1 study of E7449 as a single agent is underway to determine the MTD, safety, PK, PD, preliminary activity and perform exploratory biomarker analysis.

PM00104 (Zalypsis®) is a new synthetic alkaloid with potent cytotoxic activity against tumor cell lines. This phase I clinical trial determined the maximal tolerated dose (MTD) and recommended dose (RD) for phase II trials of PM00104 administered as a 1-hour intravenous (i.v.) infusion weekly for three consecutive weeks resting every fourth week (d1,8,15 q4wk). Forty-nine patients with advanced solid malignancies received PM00104 following a toxicity-guided, accelerated, dose-escalation design. Doses evaluated ranged from 0.07 to 3.0 mg/m2. Dose-limiting toxicities (DLTs) appeared at the highest doses tested and comprised grade 3 diarrhea and grade 4 lipase increase at 2.0 mg/m2; grade 1 thrombocytopenia and grade 2 neutropenia with two infusion omissions, grade 3 fatigue and grade 4 febrile neutropenia at 2.5 mg/m2; and grade 3/4 fatigue, grade 4 neutropenia lasting >5 days and grade 4 thrombocytopenia at 3.0 mg/m2. RD was established at 2.0 mg/m2. PM00104-related adverse events at the RD were mostly grade 1/2, with fatigue, nausea and vomiting as the most common. Transient and manageable myelosuppression and transaminase increases were also reported. Main pharmacokinetic parameters increased linearly with dose. Disease stabilization lasting ≥3 months was found in 4 patients with cervical carcinoma, colorectal adenocarcinoma, lachrymal adenoid carcinoma, and bladder carcinoma (n = 1 each). In conclusion, PM00104 2.0 mg/m2 1-hour, d1,8,15 q4wk showed a positive risk-benefit ratio, which has supported its further evaluation in three ongoing phase II clinical trials.