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Metabolite changes that constitute the Venn diagram in Figure 2. Significant changes listed are reductions (labelled "-1") or increases (labelled "1") in concentrations relative to the relevant controls.

Summary of baseline reproducibility of candidate plasma metabolite biomarkers (n=17 patients).

Characteristics of dose-dependent changes in candidate plasma metabolite pharmacodynamic biomarker concentrations in 41 patients, as determined on day 1 of pictilisib clinical trial. Cells with p-values

Changes in candidate plasma metabolite pharmacodynamic biomarker concentrations over first 2 weeks in 17 patients treated with {greater than or equal to}330 mg once-daily of pictilisib. Cells with p-values

Heat map of changes (relative to vehicle control) in candidate plasma and tumor metabolite biomarkers at 8 hours post-dosing of mice bearing U87MG xenografts with pictilisib 75mg/kg or buparlisib 60mg/kg (a, acyl; aa, acyl-acyl; ae, acyl-alkyl; Cx:y, where x is the number of carbons in the fatty acid side chain; y is the number of double bonds in the fatty acid side chain; AC, acylcarnitine; DC, decarboxyl; M, methyl; OH, hydroxyl; PC, phosphatidylcholine)

Changes in plasma metabolites across timepoints by patient/sample.

PK parameters for M3 following a single dose (Day 1) and multiple doses (Day 15)

GAZD9496 metabolite, M3 (Panel A) and M5 (Panel C), geometric mean plasma concentration following a single dose of AZD9496 on Day 1 (semi-log scale). AZD9496 metabolite, M3 (Panel B) and M5 (Panel D), geometric mean plasma concentration following multiple doses of AZD9496 on Day 15 (semi-log scale). On Day 15 at all doses except 20 mg, the 24 h time point is the 12 h trough concentration following the evening dose of AZD9496 and therefore not shown. aPooled data from dose escalation and expansion groups. BID=twice daily; QD=once daily; EXP=expansion cohort.

Background: High circulating tumor cell (CTC) counts are associated with poor prognosis in several cancers. Enrollment of patients on phase I oncology trials requires a careful assessment of the potential risks and benefits. Many patients enrolled on such trials using established eligibility criteria have a short life expectancy and are less likely to benefit from trial participation. We hypothesized that the incorporation of CTC counts might improve patient selection for phase I trials.Methods: This retrospective analysis evaluated patients who had baseline CTCs enumerated prior to their starting on a phase I trial. CTCs were enumerated using the CellSearch System.Results: Between January 2006 and December 2009 a total of 128 patients enrolled in phase I trials had CTC counts evaluated. Higher CTC counts as a continuous variable independently correlated with risk of death in this patient population (P = 0.006). A multivariate point-based risk model was generated using CTCs as a dichotomous variable (≥3 or 2 metastatic sites. Comparison of receiver operating characteristic curves demonstrated that the addition of baseline CTC counts improved the performance of the prospectively validated Royal Marsden Hospital phase I prognostic score, which now identifies three risk groups (P < 0.0001): good prognosis [score 0–1, median overall survival (OS) 63.7 weeks], intermediate prognosis (score 2–3, median OS 37.3 weeks), and poor prognosis (score 4, median OS 13.4 weeks).Conclusion: CTC enumeration improved the performance of a validated prognostic score to help select patients for phase I oncology trials. Clin Cancer Res; 17(15); 5188–96. ©2011 AACR.

PDF file - 1129K, Baseline duplicate CTC counts correlation

A dose-escalation, phase I study evaluated the safety, pharmacokinetics, pharmacogenomics, and efficacy of ES-285, a novel agent isolated from a marine mollusc, in adult cancer patients. Patients received a 24-hour i.v. infusion of ES-285 once every 3 weeks until disease progression or unacceptable toxicity. The starting dose was 4 mg/m2. Dose escalation in cohorts of at least three patients proceeded according to the worst toxicity observed in the previous cohort. Twenty-eight patients were treated with 72 courses of ES-285 across eight dose levels. No dose-limiting toxicities were seen between 4 and 128 mg/m2. Two of four patients treated at 256 mg/m2 had dose-limiting reversible grade 3 transaminitis; one patient at 256 mg/m2 also had transient grade 3 central neurotoxicity. One of three patients subsequently treated at 200 mg/m2 died following drug-related central neurotoxicity. Other toxicities included phlebitis, nausea, fatigue, and fever. Pharmacokinetic studies indicated dose proportionality with high volume of distribution (median Vss at 256 mg/m2 was 2,389 liters; range, 1,615–4,051 liters) and long elimination half life (median t1/2 at 256 mg/m2 was 28 h; range, 21–32 h). The three patients with dose-limiting toxicity had the highest drug exposure. Pharmacogenomic studies of paired surrogate tissue samples identified changes in gene expression following treatment that correlated with increasing dose. Disease stabilization for 6 to 18 weeks was recorded in nine patients. Using this schedule, 128 mg/m2 was considered safe and feasible. At this dose, pharmacologically relevant concentrations of the drug were safely achieved with pharmacogenomic studies indicating changes in the expression of genes of potential mechanistic relevance. [Mol Cancer Ther 2009;8(6):1430–7]

Supplementary Table S3 from Phase I safety, pharmacokinetic, and pharmacogenomic trial of ES-285, a novel marine cytotoxic agent, administered to adult patients with advanced solid tumors

Pharmacokinetics: Z-endoxifen levels per taselisib dose level

Supplementary Figure from A Phase I Study Investigating AZD8186, a Potent and Selective Inhibitor of PI3Kβ/δ, in Patients with Advanced Solid Tumors

Supplementary Tables S1-S4 and Figures S1-S3. Tables S1/S2: % tumor response in mice with HCT116 and A2058 tumor xenografts following treatment; Table S3: Diagram showing dose-decision guidelines utilized in the MK-2206 clinical study based on observed toxicities; Table S4: number of patients with drug-related AEs in all courses of treatment; Figure S1/S2: Line graph showing the relative tumor volume and body weight observed in patients over time expressed in terms of days following treatment; Figure S3: Patient presenting with Grade III rash

Purpose:The strategy of combining endocrine therapy with PI3K-mTOR inhibition has shown promise in estrogen receptor (ER)–positive breast cancer, but new agents and combinations with a better therapeutic index are urgently needed. Taselisib is a potent, selective, beta-isoform–sparing PI3 kinase inhibitor.Patients and Methods:30 patients with ER-positive, metastatic breast cancer who had failed prior endocrine therapy were treated with escalating doses of taselisib (2 or 4 mg in an intermittent or continuous schedule) combined with tamoxifen 20 mg once daily in this phase 1b study using a “rolling six” design.Results:Taselisib combined with tamoxifen was generally well tolerated, with treatment-emergent adverse events as expected for this class of drugs, including diarrhea (13 patients, 43%), mucositis (10 patients, 33%), and hyperglycemia (8 patients, 27%). No dose-limiting toxicities were observed. Objective responses were seen in 6 of 25 patients with RECIST-measurable disease (ORR 24%). Median time to disease progression was 3.7 months. Twelve of 30 patients (40%) had disease control for 6 months or more. Circulating tumor (ct)DNA studies using next-generation tagged amplicon sequencing identified early indications of treatment response and mechanistically relevant correlates of clinical drug resistance (e.g., mutations in KRAS, ERBB2) in some patients.Conclusions:Taselisib can be safely combined with tamoxifen at the recommended phase 2 dose of 4 mg given once daily on a continuous schedule. Preliminary evidence of antitumor activity was seen in both PIK3CA mutant and wild-type cancers. The randomized phase 2 part of POSEIDON (testing tamoxifen plus taselisib or placebo) is currently recruiting.

Supplementary Fig. S1 from Phase I safety, pharmacokinetic, and pharmacogenomic trial of ES-285, a novel marine cytotoxic agent, administered to adult patients with advanced solid tumors

Purpose:To characterize safety and tolerability of the selective PI3Kβ inhibitor AZD8186, identify a recommended phase II dose (RP2D), and assess preliminary efficacy in combination with abiraterone acetate or vistusertib.Patients and Methods:This phase I open-label study included patients with advanced solid tumors, particularly prostate cancer, triple-negative breast cancer, and squamous non–small cell lung cancer. The study comprised four arms: (i) AZD8186 monotherapy dose finding; (ii) monotherapy dose expansion; (iii) AZD8186/abiraterone acetate (with prednisone); and (iv) AZD8186/vistusertib. The primary endpoints were safety, tolerability, and identification of the RP2D of AZD8186 monotherapy and in combination. Secondary endpoints included pharmacokinetics (PK), pharmacodynamics, and tumor and prostate-specific antigen (PSA) responses.Results:In total, 161 patients were enrolled. AZD8186 was well tolerated across all study arms, the most common adverse events being gastrointestinal symptoms. In the monotherapy dose-finding arm, four patients experienced dose-limiting toxicities (mainly rash). AZD8186 doses of 60-mg twice daily [BID; 5 days on, 2 days off (5:2)] and 120-mg BID (continuous and 5:2 dosing) were taken into subsequent arms. The PKs of AZD8186 were dose proportional, without interactions with abiraterone acetate or vistusertib, and target inhibition was observed in plasma and tumor tissue. Monotherapy and combination therapy showed preliminary evidence of limited antitumor activity by imaging and, in prostate cancer, PSA reduction.Conclusions:AZD8186 monotherapy had an acceptable safety and tolerability profile, and combination with abiraterone acetate/prednisone or vistusertib was also tolerated. There was preliminary evidence of antitumor activity, meriting further exploration of AZD8186 in subsequent studies in PI3Kβ pathway–dependent cancers.

Purpose: KRAS is the most commonly mutated oncogene in human tumors. KRAS-mutant cells may exhibit resistance to the allosteric MEK1/2 inhibitor selumetinib (AZD6244; ARRY-142886) and allosteric AKT inhibitors (such as MK-2206), the combination of which may overcome resistance to both monotherapies.Experimental Design: We conducted a dose/schedule-finding study evaluating MK-2206 and selumetinib in patients with advanced treatment-refractory solid tumors. Recommended dosing schedules were defined as MK-2206 at 135 mg weekly and selumetinib at 100 mg once daily.Results: Grade 3 rash was the most common dose-limiting toxicity (DLT); other DLTs included grade 4 lipase increase, grade 3 stomatitis, diarrhea, and fatigue, and grade 3 and grade 2 retinal pigment epithelium detachment. There were no meaningful pharmacokinetic drug–drug interactions. Clinical antitumor activity included RECIST 1.0–confirmed partial responses in non–small cell lung cancer and low-grade ovarian carcinoma.Conclusion: Responses in KRAS-mutant cancers were generally durable. Clinical cotargeting of MEK and AKT signaling may be an important therapeutic strategy in KRAS-driven human malignancies (Trial NCT number NCT01021748). Clin Cancer Res; 21(4); 739–48. ©2014 AACR.

Supplementary Methods Text

Supplementary Data from A Phase I Study Investigating AZD8186, a Potent and Selective Inhibitor of PI3Kβ/δ, in Patients with Advanced Solid Tumors

Purpose: AZD9496 is an oral nonsteroidal, small-molecule inhibitor of estrogen receptor alpha (ERα) and a potent and selective antagonist and degrader of ERα. This first-in-human phase I study determined the safety and tolerability of ascending doses of oral AZD9496 in women with estrogen receptor (ER)+/HER2− advanced breast cancer, characterized its pharmacokinetic (PK) profile, and made preliminary assessment of antitumor activity.Patients and Methods: Forty-five patients received AZD9496 [20 mg once daily (QD) to 600 mg twice daily (BID)] in a dose-escalation, dose-expansion “rolling 6” design. Safety, tolerability, and PK activity in each cohort were reviewed before escalating to the next dose. PK was determined by mass spectrometry. Adverse events (AEs) were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v4.0. Objective tumor response was evaluated by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1.Results: Most common causally related AEs were diarrhea (35.6%), fatigue (31.1%), and nausea (22.2%), and seven patients had grade ≥3 AEs. Three patients experienced a dose-limiting toxicity: one each at 150 mg BID (abnormal hepatic function), 400 mg BID (diarrhea and elevated liver function tests), and 600 mg BID (diarrhea), and all were reversible. The maximum tolerated dose was not reached. Partial response was confirmed in one patient, who also had decreased tumor marker Ca15.3. Four patients had stable disease at 12 months' follow-up.Conclusions: AZD9496 is well tolerated with an acceptable safety profile, showing evidence of prolonged disease stabilization in heavily pretreated patients with ER+/HER2− advanced breast cancer. Clin Cancer Res; 24(15); 3510–8. ©2018 AACR.See related commentary by Jordan, p. 3480

A total of 45 patients were recruited and four to six patients were allocated to cohorts to receive escalating doses of AZD9496. In the BID cohorts, patients received QD dosing on Day 1 and BID dosing thereafter. Six patients entered the expansion cohort, receiving AZD9496 250 mg BID. BID=twice daily, DLT=dose-limiting toxicity; n=number of patients included; LFT=liver function tests; QD=once daily.

Background: SERENA-1 (NCT03616587) is a Phase 1, multi-part, open-label study of camizestrant in women with ER+/HER2− advanced breast cancer. Parts A/B and C/D (escalation/expansion) examined camizestrant as monotherapy and in combination with palbociclib respectively and have been presented previously.1,2 Here we present data from parts G/H which examined camizestrant in combination with abemaciclib. Methods: The primary objective was to determine the safety and tolerability of camizestrant 75 mg once daily (QD) in combination with abemaciclib 150 mg twice daily (BID). Secondary objectives included investigation of anti-tumor response and pharmacokinetics (PK). Participants were previously treated women of any menopausal status (pre-menopausal women received this combination alongside ongoing ovarian function suppressors). Prior treatment with ≤2 lines of chemotherapy in the advanced setting was permitted. There was no limit on the number of lines of prior endocrine treatment in the advanced setting; previous treatment with CDK4/6 inhibitors (CDK4/6i) and fulvestrant was permitted. Results: As of 1st June 2022, 24 patients had received camizestrant in combination with abemaciclib with a median 7.7 month follow up. Tolerability of the combination of camizestrant and abemaciclib was consistent with that of each drug individually. No patient required camizestrant dose reduction. All camizestrant-related heart rate decreases were Grade 1 (asymptomatic). PK data for camizestrant in combination with abemaciclib were consistent with camizestrant as monotherapy and published abemaciclib steady-state PK data, indicating no clinically relevant drug-drug interaction. In these heavily pre-treated patients (46% prior chemotherapy, 75% prior CDK4/6i, 54% prior fulvestrant; all in the advanced disease setting) and of whom 67% had visceral metastases, the objective response rate was 5/19 (26.3%), the clinical benefit rate at 24 weeks was 16/24 (66.7%) and the median progression-free survival had not been reached, with 8/24 patients experiencing a progression event. These data support the use of camizestrant 75 mg QD combined with the approved abemaciclib dose. Conclusions: Camizestrant 75 mg QD in combination with abemaciclib 150 mg BID was well tolerated with encouraging clinical activity. The inclusion of this regimen in the ongoing Phase 3, SERENA-6 trial 3, of camizestrant combined with CDK4/6i versus an aromatase inhibitor, will further clarify the role of this combination in the treatment of patients with ER+/HER2− advanced breast cancer with tumors expressing ESR1 mutations. References 1. Baird R, Oliveira M, Ciruelos Gil EM, et al. SABCS 2020 Virtual Meeting. Abstract PS11-05. 2. Oliveira M, Hamilton EP, Incorvati J, et al. J Clin Oncol 40, 2022 (suppl 16; abstr 1032). 3. SERENA-6 trial. Available at https://clinicaltrials.gov/ct2/show/NCT04964934 We acknowledge Helen Heffron, PhD, from InterComm International who provided medical writing support funded by AstraZeneca. Citation Format: Nicholas Turner, Christos Vaklavas, Emiliano Calvo, Javier Garcia-Corbacho, Jason Incorvati, Manuel Ruiz Borrego, Chris Twelves, Anne Armstrong, Begoña Bermejo, Erika Hamilton, Mafalda Oliveira, Eva Ciruelos, Peter Kabos, Manish R Patel, Maria Borrell, Howard Burris, Bruno de Paula, Alejandro Falcon, Cristina Hernando, Irene Moreno, Ciara S. O’Brien, Elena Shagisultanova, Ivan Victoria Ruiz, Judy S. Wang, Mei Wei, Tim Brier, Danielle Carroll, Carmela Ciardullo, Lisa Gibbons, itziar irurzun-Arana, Tony Jack, bistra kirova, Teresa Klinowska, Justin Lindemann, Julie Maidment, Alastair Mathewson, Rhiannon Maudsley, Robert McEwen, Christopher Morrow, Andy Sykes, Richard D. Baird. SERENA-1: Updated analyses from a Phase 1 study of the next generation oral selective estrogen receptor degrader camizestrant (AZD9833) combined with abemaciclib, in women with ER-positive, HER2-negative advanced breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-07-28.

Background: More than two thirds of patients with advanced breast cancer (ABC) have estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2−) tumors. In most countries, current standard-of-care first-line treatments include an aromatase inhibitor or fulvestrant, a selective ER degrader, combined with cyclin-dependent kinase 4/6 inhibitors. Concurrent use of luteinizing hormone-releasing hormone agonists is recommended for men and premenopausal women with ABC. Nevertheless, almost all ABCs eventually become resistant to endocrine therapy and the disease is incurable in these cases. New therapies are needed to combat endocrine therapy resistance, maintain patient health-related quality-of-life, and delay the need for chemotherapy. AZD9833 (camizestrant) is a highly potent, next-generation selective ER degrader and pure ER antagonist that has demonstrated anticancer properties across a range of preclinical models, including those with ER-activating mutations (Scott et al, AACR 2020). A Phase I dose-escalation and expansion study (SERENA-1) has demonstrated that AZD9833 is well tolerated and has a promising antitumor activity when administered alone or in combination with the cyclin-dependent kinase 4/6 inhibitor palbociclib (Baird et al, SABCS 2020). SERENA-4 (NCT04711252) is a randomized, multicenter, double-blind, Phase III trial to evaluate the safety and efficacy of AZD9833 in combination with palbociclib for patients with ER+/HER2− ABC who have not received systemic treatment in the advanced disease setting. Methods: SERENA-4 will enroll 1342 patients with de novo or recurrent ER+/HER2− ABC who have not previously received systemic treatment for their locoregionally recurrent or metastatic disease. Patients with recurrent disease must have received adjuvant aromatase inhibitor or tamoxifen therapy for at least 24 months without relapse. Patients will be randomized 1:1 to receive oral treatment with either (a) AZD9833 75 mg once daily, palbociclib 125 mg once daily for 21 days followed by 7 days off treatment and a placebo for anastrozole 1 mg once daily or (b) anastrozole 1 mg once daily, palbociclib (same as active arm) and a placebo for AZD9833 75 mg once daily. Men and premenopausal women will also receive a luteinizing hormone-releasing hormone agonist. The primary endpoint is progression-free survival (PFS; up to 5 years). Secondary endpoints include overall survival (up to 8 years), second PFS, time to chemotherapy, objective response rate, and changes in health-related quality-of-life measures. Enrollment began in January 2021. As of 02 July 2021, the number of open sites is 57 across 15 countries. Acknowledgments: We thank Julia Mawer, PhD, of Oxford PharmaGenesis, Oxford, UK, for providing medical writing support funded by AstraZeneca Funding: The SERENA-4 trial is funded and overseen by AstraZeneca. © 2021 American Society of Clinical Oncology, Inc. Reused with permission. This abstract was accepted and previously presented at the 2021 ASCO Annual Meeting. All rights reserved. Citation Format: Fabrice André, Seock-Ah Im, Patrick Neven, Richard D Baird, Johannes Ettl, Matthew P Goetz, Erika Hamilton, Hiroji Iwata, Zefei Jiang, Anil Abraham Joy, Vincent Haddad, Andrew Walding, Manuel Selvi Miralles, Cynthia Huang Bartlett, Antonio Llombart-Cussac. SERENA-4: A Phase III comparison of AZD9833 (camizestrant) plus palbociclib, versus anastrozole plus palbociclib, for patients with ER-positive/HER2-negative advanced breast cancer who have not previously received systemic treatment for advanced disease [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-11-06.

The human epidermal growth factor receptor 2 (HER2, ERBB2) is amplified or overexpressed in approximately 20% of breast cancers. HER2 amplification results in increased homodimerization and HER3 heterodimerization, with HER2/HER3 heterodimers promoting cell proliferation via the mitogen-activated protein kinase/AKT pathway and also evasion of apoptosis via the phosphatidylinositol 3-kinase (PI3K) signaling cascade. Oncogenic mutations in PI3KCA render tumor cells resistant to drugs that block HER2 dimerization, thereby promoting cell survival. Although several approved HER2-directed agents have shown significant survival improvements for HER2-positive patients, in the metastatic setting, nearly all of these patients will ultimately progress and die of their disease.

Background: In the PAKT study, addition of the oral AKT inhibitor capivasertib to 1st-line paclitaxel therapy for metastatic TNBC resulted in significantly longer progression-free survival (PFS; primary endpoint; Schmid, J Clin Oncol 2020). The stratified PFS hazard ratio was 0.74 (95% CI, 0.50-1.08; one-sided P=0.06; predefined significance level of 0.10, one-sided; median PFS 5.9 vs 4.2 months with capivasertib vs placebo). Overall survival (OS) results were immature at the primary analysis with 53% of events but suggested long OS with capivasertib (HR, 0.61; 95% CI, 0.37-0.99; two-sided P=0.04). Here we report final results. Methods: This double-blind, placebo-controlled, randomised phase II trial, recruited women with untreated, metastatic TNBC. Total of 140 patients were randomly assigned (1:1) to paclitaxel 90mg/m2 (days 1, 8, 15) with either capivasertib (400mg twice daily) or placebo (days 2-5, 9-12, 16-19) every 28 days until disease progression or unacceptable toxicity. The primary endpoint was PFS. Secondary endpoints included OS in the ITT population and in patients with and without PIK3CA/AKT1/PTEN-alterations. Results: With a median F/U of 40.0 months, median OS was longer in the capivasertib arm (19.1 vs 13.5 months, stratified HR 0.70, 95% CI 0.47-1.05, p=0.085). In contrast to the earlier analysis, no meaningful differences were seen in terms of benefit with capivasertib between patients with or without alterations of PIK3CA/AKT1/PTEN. Median OS numerically favoured capivasertib vs placebo both in the PIK3CA/AKT1/PTEN-altered (stratified HR 0.58, 95% CI 0.21-1.58, p=0.290) and PIK3CA/AKT1/PTEN non-altered subgroup (stratified HR 0.74, 95% CI 0.47-1.18, p=0.207). The safety profile of capivasertib plus paclitaxel was unchanged. Conclusions: Final OS results show a numerical trend favouring capivasertib; effects were observed regardless of PIK3CA/AKT1/PTEN alterations. Consistent with the previously observed PFS benefit, these findings support further evaluation of first-line Capivasertib plus paclitaxel for metastatic TNBC in the ongoing Capitello290 randomised phase III trial in patients with and without PIK3CA/AKT1/PTEN alterations. Citation Format: Peter Schmid, Jacinta Abraham, Stephen Chan, Adrian Murray Brunt, Gia Nemsadze, Richard D Baird, Yeon Hee Park, Peter Hall, Timothy Perren, Robert C Stein, László Mangel, Jean-Marc Ferrero, Melissa Phillips, John Conibear, Javier Cortes, Andrew Foxley, Elza de Bruin, Robert McEwen, Myria Nikolaou, Daniel Stetson, Brian Dougherty, Aaron Prendergast, Max McLaughlin-Callan, Matthew Burgess, Cheryl Lawrence, Hayley Cartwright, Kelly Mousa, Nicholas Turner, Duncan Wheatley. Mature survival update of the double-blind placebo-controlled randomised phase II PAKT trial of first-line capivasertib plus paclitaxel for metastatic triple-negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD1-11.

Background: AZD9833 is an oral selective estrogen receptor (ER) antagonist and degrader (SERD) in Phase 2 clinical development for the treatment of ER+ HER2− breast cancer. Here we report data from Parts C and D of the ongoing Phase 1 study (SERENA-1) examining AZD9833 in combination with palbociclib, together with updated data from Parts A and B examining AZD9833 monotherapy. Methods: SERENA-1 (NCT03616587) is an ongoing open-label Phase 1 study of AZD9833 in pre- and post-menopausal women with ER+, HER2− advanced breast cancer who have previously received ≥1 endocrine therapy and ≤2 prior chemotherapies. Prior treatment with fulvestrant and/or CDK4/6 inhibitors was permitted. The primary objective is to determine the safety and tolerability of once daily (QD) AZD9833, with dose-limiting toxicities (DLTs) in the first 28 days defining the maximum tolerated dose. Secondary objectives include anti-tumor response (including circulating tumor [ct] DNA response) and pharmacokinetics. Parts A (escalation) and B (expansion) assess AZD9833 as a monotherapy, and Parts C (escalation) and D (expansion) assess AZD9833 in combination with palbociclib. Results: At a data cut-off of March 24 2020, 17 patients had received either 150 mg or 300 mg AZD9833 in combination with palbociclib, given according to its product labeling. Eighty patients had received AZD9833 monotherapy at doses of 25, 75, 150, 300, and 450 mg QD. In patients treated with AZD9833 and palbociclib, treatment-related adverse events (AEs; experienced by ≥10% of patients) included visual disturbances*, bradycardia*, asthenia, anemia, QTcF prolongation, nausea, neutropenia, decreased white blood cell count, and vomiting (*combined terms). All instances of AZD9833-related bradycardia were Grade 1. One DLT was observed in the 150 mg cohort: CTCAE Grade 2 visual disturbances, which began on Cycle 1 Day 8 and resolved by Cycle 1 Day 9 following dose interruption. The patient restarted treatment on Cycle 1 Day 15 at 75 mg and continued this dose until data cut-off. No causally related AEs led to discontinuation of AZD9833. The tolerability of AZD9833 with palbociclib was consistent with the observed tolerability profile of AZD9833 monotherapy, and the known tolerability profile of palbociclib. Pharmacokinetic analysis showed similar AZD9833 exposure for monotherapy and palbociclib combination therapy. Similarly, palbociclib exposure was comparable with simulations using a published population pharmacokinetic model. In Part A, ESR1 hotspot mutations were detected in ctDNA at baseline in 26/56 (46%) patients; 13/26 (50%) of these patients achieved a partial response or stable disease at 24 weeks, including 5/10 (50%) with a Y537S ESR1 mutation. Further, in patients with ESR1 mutations and samples available for longitudinal ctDNA analysis, 17/20 (85%) exhibited a reduction or loss of mutant ESR1 on treatment with AZD9833. Efficacy data to be presented include objective response rate and clinical benefit rate at 24 weeks. Of note, unconfirmed partial responses have been observed in Part C after the data cut-off for this abstract. Conclusions: AZD9833 continues to show an encouraging efficacy and dose-dependent safety profile as a monotherapy or in combination with palbociclib. A Phase 2 study comparing the efficacy and safety of three doses of AZD9833 versus fulvestrant (NCT04214288), and a Phase 2 pre-surgical ‘window of opportunity’ study (EUDRA-CT; 2019-003706-2) are ongoing. Citation Format: Richard Baird, Mafalda Oliveira, Eva Maria Ciruelos Gil, Manish R Patel, Begoña Bermejo de las Heras, Manuel Ruiz-Borrego, Javier García-Corbacho, Anne Armstrong, Udai Banerji, Chris Twelves, Valentina Boni, Jason Incorvati, Peter Kabos, Adam L Cohen, Bruno de Paula, Marta Capelán Rodríguez, Judy S Wang, Christina Hernando, Alejandro Falcón Gonzalez, Ivan Victoria Ruiz, Julia Lai-Kwon, Anosheh Afghani, Christos Vaklavas, Tim Brier, Steven Fox, Bistra Kirova, Teresa Klinowska, Chris Leach, Justin PO Lindemann, Richard Mather, Rhiannon Maudsley, Christopher J Morrow, Nitharsan Sathiyayogan, Andy Sykes, Li Zhang, Erika Hamilton. Updated data from SERENA-1: A Phase 1 dose escalation and expansion study of the next generation oral SERD AZD9833 as a monotherapy and in combination with palbociclib, in women with ER-positive, HER2-negative advanced breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS11-05.

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.FUNDING: Cancer Research UK, AstraZeneca, and Puma Biotechnology.

Current evidence suggests that plasma cell-free DNA (cfDNA) is fragmented around a mode of 166 bp. Data supporting this view has been mainly acquired through the analysis of double-stranded cfDNA. The characteristics and diagnostic potential of single-stranded and damaged double-stranded cfDNA in healthy individuals and cancer patients remain unclear. Here, through a combination of high-affinity magnetic bead–based DNA extraction and single-stranded DNA sequencing library preparation (MB-ssDNA), we report the discovery of a large proportion of cfDNA fragments centered at ∼50 bp. We show that these “ultrashort” cfDNA fragments have a greater relative abundance in plasma of healthy individuals (median = 19.1% of all sequenced cfDNA fragments, n = 28) than in plasma of patients with cancer (median = 14.2%, n = 21, P < 0.0001). The ultrashort cfDNA fragments map to accessible chromatin regions of blood cells, particularly in promoter regions with the potential to adopt G-quadruplex (G4) DNA secondary structures. G4-positive promoter chromatin accessibility is significantly enriched in ultrashort plasma cfDNA fragments from healthy individuals relative to patients with cancers (P < 0.0001), in whom G4-cfDNA enrichment is inversely associated with copy number aberration-inferred tumor fractions. Our findings redraw the landscape of cfDNA fragmentation by identifying and characterizing a novel population of ultrashort plasma cfDNA fragments. Sequencing of MB-ssDNA libraries could facilitate the characterization of gene regulatory regions and DNA secondary structures via liquid biopsy. Our data underline the diagnostic potential of ultrashort cfDNA through classification for cancer patients.

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.

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.

Background: Circulating tumor DNA (ctDNA) is found in the plasma of over 90% of patients with advanced breast cancer (BC). ctDNA analysis can establish the current genomic profile of an individual’s cancer and identify potentially targetable mutations. The genomic landscape of advanced BC and clinical associations has yet to be fully defined. This analysis describes the genomic landscape of ctDNA in patients screened for the UK plasmaMATCH study. Methods: The plasmaMATCH trial was an open-label, multi-centre, multi-cohort platform trial, consisting of ctDNA testing in ~1000 patients with advanced BC. The trial consists of parallel treatment cohorts (Cohorts A-E) with therapies matched to mutations identified in ctDNA testing. The genomic landscape of ctDNA in advanced BC was prospectively analysed for hotspot PIK3CA,AKT1, HER2 and ESR1 mutations using digital droplet PCR (ddPCR, Bio-Rad), and using an error-corrected 73-gene targeted panel (Guardant360, Guardant Health) prospectively from part-way through the trial, and retrospectively for the remaining patients. Results: Entry into ctDNA testing for Cohorts A-D was closed on 26/Apr/2019, at which time 1044 patients had been registered and 1025 tested with ddPCR. 800 patients had targeted panel ctDNA sequencing (364 prospective, 436 retrospective) (Table 1). Targeted sequencing identified a somatic alteration in 92.9% of patients (743/800). The most frequent mutations were TP53 (44.1%), PIK3CA (34.9%), ESR1 (33.1%), GATA3 (11.0%) and ARID1A (7.8%). ESR1 (33.1%) and KRAS (4.1%) alterations occurred at higher frequency in ctDNA compared to a metastatic tissue sequencing series (q Genomic AlterationddPCR*Targeted Panel**All % n = 1025HR+ HER2-% n = 658HR+ HER2+ % n = 62HR- HER2+ % n = 36TNBC % n = 172All % n = 800HR+ HER2- % n = 515HR+ HER2+ % n = 48HR- HER2+ % n = 26TNBC % n = 136PIK3CA mutation25.829.933.919.49.334.939.041.734.614.7ESR1 mutation27.737.819.40033.143.522.900.7AKT1 mutation4.24.01.604.75.05.22.104.4ERBB2 mutation2.73.208.31.26.46.612.515.42.2PTEN mutationNANANANANA6.98.54.23.84.4ERBB2 amplificationNANANANANA5.81.931.357.71.5MSI highNANANANANA1.10.42.101.5* Phenotype data based on 928 patients with known phenotype tested by ddPCR for targetable hotspot mutations.** Phenotype data based on 725 patients with known phenotype sequenced by targeted panel. All pathogenic mutations are shown, including mutations not tested by ddPCR. Citation Format: Belinda Kingston, Hannah Bye, Michael Hubank, Giselle Walsh, Claire Swift, Matthew Beaney, Lucy Kilburn, Sarah Kernaghan, Andrew M Wardley, Iain Macpherson, Richard D Baird, Rebecca Roylance, Katie Wilkinson, Isaac Garcia-Murillas, Judith M Bliss, Nicholas Turner, Alistair Ring, on behalf of the plasmaMATCH Trial Management Group. The genomic landscape of breast cancer based on ctDNA analysis: Data from the plasmaMATCH trial [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 GS3-07.

Approved CDK4/6 inhibitors have demonstrated significant improvements in progression free survival when combined with fulvestrant in patients with HR+/HER2- advanced breast cancer, though limited by neutropenia and gastrointestinal side effects. Lerociclib is a potent selective CDK4/6 inhibitor with a differentiated PK/PD profile from currently approved CDK4/6 inhibitors that has demonstrated clinical proof-of-concept (Phase 1b data ASCO 2018). This Phase 1b/2a study assesses lerociclib dose escalation in combination with 500 mg fulvestrant using a 3+3 design followed by dose expansion in patients with metastatic or locally advanced HR+/HER2- breast cancer that had progressed following endocrine therapy. Up to two prior chemotherapies in Phase 1b and one prior in Phase 2a in the advanced setting are allowed. Prior fulvestrant was excluded for all patients; prior CDK4/6 inhibitors were excluded in Phase 2a only. Lerociclib is administered daily without a drug holiday. The objectives are to evaluate DLTs, safety, tolerability, PK, and tumor response and to determine the recommended dose and schedule (QD or BID) of lerociclib administered with fulvestrant for randomized trials. The BID dosing regimen demonstrated optimal safety, tolerability, and antitumor activity. To date, 35 patients (6 patients @ 100 mg BID, 9 patients @ 150 mg BID, 17 patients @ 200 mg BID, and 3 patients @ 250 mg BID) with mean age of 54 years, ECOG of 0 (86%) or 1 (14%), and a median of two prior anticancer therapies in the advanced setting have received lerociclib + fulvestrant for up to 804 days. A dose proportional increase in drug exposure has been observed. The most common lerociclib-related adverse events were neutropenia (63%), leukopenia (57%), nausea (37%), anemia (29%), diarrhea (20%), and thrombocytopenia (20%). The rates of lerociclib-related Grade 3 and Grade 4 neutropenia were 29% and 9%, respectively. Following an initial decline, ANC plateaued beginning at week 4. There were no reports of Grade 3 or greater nausea, vomiting, or diarrhea. One DLT of dose interruption due to Grade 2 fatigue and nausea was observed at 200 mg BID. There have been no reports of venous thromboembolism, QT prolongation or drug-induced liver injury. Twenty patients were evaluable for tumor response based on RECIST v1.1. Five patients (25%) had a confirmed PR; 8 patients (40 %) had stable disease; 6 patients (30 %) had PD. The CBR (CR + PR + SD ≥ 24 weeks) was 67% (12 of 18 patients either had SD at the week 24 tumor assessments or achieved an objective response). A population PK/PD/efficacy model was developed, and simulation data are concordant with existing clinical results. Additional patients are being enrolled at 150 mg BID and 200 mg BID, and updated data will be presented. Lerociclib, dosed BID with no drug holiday, has a favorable safety profile with low rates of gastrointestinal AEs and Grade 3/4 neutropenia, as well as encouraging antitumor activity in patients with HR+/HER2- advanced breast cancer. Phase 2b is ongoing to confirm the BID dose (150 mg or 200 mg) for randomized clinical trials. Clinical trial information: NCT02983071. Citation Format: Iurie Bulat, Marina Maglakelidze, Carmen Murias, Boris Krastev, Richard D Baird, Andrew M Wardley, Rebecca Roylance, Adrian Crijanovschi, Maia Gogiladze, Yili Pritchett, Amy McCullough, Chao Li, Jessica A Sorrentino, Rajesh Malik, Andrew P Beelen. Dose escalation and expansion study of lerociclib (G1T38), an oral CDK4/6 inhibitor, dosed with no drug holiday in combination with fulvestrant in patients with HR+/HER2- advanced breast cancer [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 P1-19-17.

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.

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.

Radiotherapy is a fundamental component of treatment for the majority of patients with cancer. In recent decades, technological advances have enabled patients to receive more targeted doses of radiation to the tumor, with sparing of adjacent normal tissues. There had been hope that the era of precision medicine would enhance the combination of radiotherapy with targeted anticancer drugs; however, this ambition remains to be realized. In view of this lack of progress, the FDA–AACR–ASTRO Clinical Development of Drug–Radiotherapy Combinations Workshop was held in February 2018 to bring together stakeholders and opinion leaders from academia, clinical radiation oncology, industry, patient advocacy groups, and the FDA to discuss challenges to introducing new drug–radiotherapy combinations to the clinic. This Perspectives in Regulatory Science and Policy article summarizes the themes and action points that were discussed. Intelligent trial design is required to increase the number of studies that efficiently meet their primary outcomes; endpoints to be considered include local control, organ preservation, and patient-reported outcomes. Novel approaches including immune-oncology or DNA-repair inhibitor agents combined with radiotherapy should be prioritized. In this article, we focus on how the regulatory challenges associated with defining a new drug–radiotherapy combination can be overcome to improve clinical outcomes for patients with cancer.

Purpose: The vast majority of advanced ER POS breast cancers eventually cease responding to endocrine (ET) and other therapies leading to evolution of lethal disease. However, timely monitoring of the molecular events associated with response/progression in tissue biopsies is logistically difficult. The use of liquid biopsies, such as CTC and ctDNA, in this context has been of recent interest. Patients and Methods: Individual CTC and ctDNA were obtained at different time points from patients with advanced ER POS/HER2 NEG breast cancer enrolled in a Phase I trial of AZD9496, an oral selective estrogen receptor degrader (SERD) ET. The CTC, purified using tandem CellSearch®/DepArray™ technologies, were genomically profiled by DNA single cell next generation sequencing (scNGS). Plasma ctDNA was isolated from blood collected in Streck BCT tubes. Genomic profiling was performed by targeted gene panel scNGS for CTC and ddPCR for ERα gene (ESR1) mutations in ctDNA. Results: 123 high-quality CTCs from 12 patients profiled by scNGS showed 100% concordance with ctDNA in detection of driver ESR1 somatic mutations. CTC scNGS additionally revealed extensive intra-patient heterogeneity of driver alterations, that would have been unresolvable by bulk ctDNA profiling, including separate subclonal CTC populations emerging within the same patient. ScNGS revealed potential opportunities for targeted therapies in 73% of patients, directed at alterations in PIK3CA, FGFR2, KIT and BRAF, at times present as 2 or more targets in the same or different cell populations. In one patient, an emergent, distinct, BRAF p.V600E targetable alteration was detected in a subpopulation of CTCs collected at the progression time point but not at baseline. Conclusion: Serial monitoring of CTC and ctDNA genomic alterations is feasible and should enable real-time tracking of response/progression, tumor evolution and opportunities for precision medicine interventions. Citation Format: Andi K. Cani, Emily M. Dolce, Elizabeth P. Darga, Kevin Hu, Martha Brown, Chia-Jen Liu, Jackie Pierce, Kieran Bradbury, Kimberly Aung, Gaia Schiavon, Danielle Carroll, T. H. Carr, Teresa Klinowska, Justin Lindemann, Gayle Marshall, Vicky Rowlands, Elizabeth A. Harrington, J. Barrett, Anne Armstrong, Richard Baird, Erika Hamilton, Seock-Ah Im, Komal Jhaveri, Manish R. Patel, Caroline Dive, Scott A. Tomlins, Aaron M. Udager, Daniel F. Hayes, Costanza Paoletti. Monitoring circulating tumor cell (CTC) and circulating tumor DNA (ctDNA) genomic alterations in ER positive (POS)/HER2 negative (NEG) advanced breast cancer during endocrine therapy: correlative study of AZD9496 oral SERD phase I trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3143.

The genomics of advanced breast cancer (ABC) has been described through tumour tissue biopsy sequencing, although these approaches are limited by geographical and temporal heterogeneity. Here we use plasma circulating tumour DNA sequencing to interrogate the genomic profile of ABC in 800 patients in the plasmaMATCH trial. We demonstrate diverse subclonal resistance mutations, including enrichment of HER2 mutations in HER2 positive disease, co-occurring ESR1 and MAP kinase pathway mutations in HR + HER2− disease that associate with poor overall survival (p = 0.0092), and multiple PIK3CA mutations in HR + disease that associate with short progression free survival on fulvestrant (p = 0.0036). The fraction of cancer with a mutation, the clonal dominance of a mutation, varied between genes, and within hotspot mutations of ESR1 and PIK3CA. In ER-positive breast cancer subclonal mutations were enriched in an APOBEC mutational signature, with second hit PIK3CA mutations acquired subclonally and at sites characteristic of APOBEC mutagenesis. This study utilises circulating tumour DNA analysis in a large clinical trial to demonstrate the subclonal diversification of pre-treated advanced breast cancer, identifying distinct mutational processes in advanced ER-positive breast cancer, and novel therapeutic opportunities., Circulating tumour DNA can provide useful information on disease burden. Here, the authors analysed circulating tumour DNA from 800 patients from a breast cancer clinical trial and investigate the subclonal nature of the disease, and identify DNA mutations associated with resistance and poor survival.

There is a growing need for systems that efficiently support the work of medical teams at the precision oncology point-of-care. Here we present the implementation of the Molecular Tumor Board Portal (MTBP), an academic clinical decision support system that creates a unified legal, scientific and technological platform to share and harness next-generation sequencing data across the Cancer Core Europe network. Automating the interpretation and reporting of sequencing results decreased drastically the need for manual procedures that are time consuming and prone to errors. In addition, the adoption of an expert-agreed process to systematically link tumor molecular profiles with clinical actions promoted consistent decision-making and structured data capture across centers. Finally, the use of information-rich patient reports with interactive content facilitated collaborative discussion of complex cases during virtual molecular tumor board meetings. Overall, we believe that streamlined digital systems like the MTBP are crucial to better address the challenges brought by precision oncology and accelerate the use of emerging biomarkers.

There is a growing need for systems that efficiently support the work of medical teams at the precision-oncology point of care. Here, we present the implementation of the Molecular Tumor Board Portal (MTBP), an academic clinical decision support system developed under the umbrella of Cancer Core Europe that creates a unified legal, scientific and technological platform to share and harness next-generation sequencing data. Automating the interpretation and reporting of sequencing results decrease the need for time-consuming manual procedures that are prone to errors. The adoption of an expert-agreed process to systematically link tumor molecular profiles with clinical actions promotes consistent decision-making and structured data capture across the connected centers. The use of information-rich patient reports with interactive content facilitates collaborative discussion of complex cases during virtual molecular tumor board meetings. Overall, streamlined digital systems like the MTBP are crucial to better address the challenges brought by precision oncology and accelerate the use of emerging biomarkers.

1032 Background: SERENA-1 (NCT03616587) is a Phase 1, multi-part, open-label study of camizestrant in women with ER+, HER2− advanced breast cancer (ABC). Parts A/B (escalation/expansion) assessed camizestrant monotherapy and have been presented previously. Parts C/D examine camizestrant in combination with palbociclib; here we present mature data from camizestrant 75 mg in combination with palbociclib; 75 mg being the camizestrant dose currently under investigation in the Phase 3 studies SERENA-4 (NCT04711252) and SERENA-6 (NCT04964934). Methods: The primary objective was to determine the safety and tolerability of camizestrant once daily (QD) with palbociclib. Secondary objectives included anti-tumor response and pharmacokinetics (PK). Prior treatment with < 2 lines of chemotherapy in the advanced setting was permitted. There was no limit on the number of lines of prior endocrine treatment in the advanced setting; prior treatment with CDK4/6 inhibitors and fulvestrant (F) was permitted. Results: As of 9 September 2021, 25 patients had received camizestrant 75 mg QD in combination with palbociclib. Tolerability of the combination of camizestrant 75 mg and palbociclib was consistent with that of each drug individually. No patient required camizestrant dose interruption/reduction/discontinuation due to a camizestrant-related adverse event (AE); moreover, none experienced a Grade ≥3 camizestrant-related AE. All camizestrant-related heart rate reductions were Grade 1 (asymptomatic). All camizestrant-related visual effects were Grade 1 (mild), apart from one patient who experienced transient Grade 2 (moderate) visual effects that resolved to Grade 1 without dose modification. Camizestrant-related gastrointestinal disorders were all Grade 1, except one instance of Grade 2 nausea lasting one day. PK data for camizestrant 75 mg QD and palbociclib combined were broadly consistent with camizestrant as monotherapy and published palbociclib steady-state PK data, further supporting the use of camizestrant 75 mg QD (Phase 3 dose) in combination with the approved palbociclib doses. In these heavily pre-treated patients (48% prior chemotherapy, 80% prior CDK4/6i, 68% prior F; all in advanced disease setting) and of whom 60% had visceral metastases, the clinical benefit rate at 24 weeks was 7/25 (28%). Conclusions: The PK and safety profile of camizestrant 75 mg QD in combination with palbociclib is favorable in this mature Phase 1 dataset. Despite extensive pre-treatment - including chemotherapies, CDK4/6i, and F - camizestrant 75 mg QD in combination with palbociclib exhibits encouraging clinical activity. The results from the ongoing Phase 3 studies, SERENA-4 and SERENA-6, will further elucidate the role of this combination in the treatment of patients with HR+/HER2− ABC. Clinical trial information: NCT03616587.

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]