Capivasertib in Hormone Receptor-Positive Advanced Breast Cancer.

BACKGROUND: AKT pathway activation is implicated in endocrine-therapy resistance. Data on the efficacy and safety of the AKT inhibitor capivasertib, as an addition to fulvestrant therapy, in patients with hormone receptor-positive advanced breast cancer are limited. METHODS: In a phase 3, randomized, double-blind trial, we enrolled eligible pre-, peri-, and postmenopausal women and men with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer who had had a relapse or disease progression during or after treatment with an aromatase inhibitor, with or without previous cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor therapy. Patients were randomly assigned in a 1:1 ratio to receive capivasertib plus fulvestrant or placebo plus fulvestrant. The dual primary end point was investigator-assessed progression-free survival assessed both in the overall population and among patients with AKT pathway-altered (PIK3CA, AKT1, or PTEN) tumors. Safety was assessed. RESULTS: Overall, 708 patients underwent randomization; 289 patients (40.8%) had AKT pathway alterations, and 489 (69.1%) had received a CDK4/6 inhibitor previously for advanced breast cancer. In the overall population, the median progression-free survival was 7.2 months in the capivasertib-fulvestrant group, as compared with 3.6 months in the placebo-fulvestrant group (hazard ratio for progression or death, 0.60; 95% confidence interval [CI], 0.51 to 0.71; P<0.001). In the AKT pathway-altered population, the median progression-free survival was 7.3 months in the capivasertib-fulvestrant group, as compared with 3.1 months in the placebo-fulvestrant group (hazard ratio, 0.50; 95% CI, 0.38 to 0.65; P<0.001). The most frequent adverse events of grade 3 or higher in patients receiving capivasertib-fulvestrant were rash (in 12.1% of patients, vs. in 0.3% of those receiving placebo-fulvestrant) and diarrhea (in 9.3% vs. 0.3%). Adverse events leading to discontinuation were reported in 13.0% of the patients receiving capivasertib and in 2.3% of those receiving placebo. CONCLUSIONS: Capivasertib-fulvestrant therapy resulted in significantly longer progression-free survival than treatment with fulvestrant alone among patients with hormone receptor-positive advanced breast cancer whose disease had progressed during or after previous aromatase inhibitor therapy with or without a CDK4/6 inhibitor. (Funded by AstraZeneca and the National Cancer Institute; CAPItello-291 ClinicalTrials.gov number, NCT04305496.).

A View on Drug Development for Cancer Prevention.

Despite some notable successes, there are still relatively few agents approved for cancer prevention. Here we review progress thus far in the development of medicines for cancer prevention, and we outline some key concepts that could further enable or accelerate drug development for cancer prevention in the future. These are summarized under six key themes: (i) unmet clinical need, (ii) patient identification, (iii) risk stratification, (iv) pharmacological intervention, (v) clinical trials, and (vi) health care policy. These concepts, if successfully realized, may help to increase the number of medicines available for cancer prevention. SIGNIFICANCE: The huge potential public health benefits of preventing cancer, combined with recent advances in the availability of novel early detection technologies and new treatment modalities, has caused us to revisit the opportunities and challenges associated with developing medicines to prevent cancer. Here we review progress in the field of developing medicines to prevent cancer to date, and we present a series of ideas that might help in the development of more medicines to prevent cancer in the future.

Using qualitative interviews to identify patient-reported clinical trial endpoints and analyses that are the most meaningful to patients with advanced breast cancer.

BACKGROUND: Designing clinical trials with the emphasis on the patient-centered approach and focusing on clinical outcomes that are meaningful to patients is viewed as a priority by drug developers, regulatory agencies, payers, clinicians, and patients. This study aimed to capture information on clinical trial endpoints that would be most important and relevant for patients with advanced breast cancer, based on patient-reported outcomes. METHODS: Patients with either advanced triple-negative breast cancer [TNBC] and a maximum of two lines of systemic therapy or hormone receptor-positive/human epidermal growth factor receptor 2-negative [HR+/HER2-] breast cancer and a maximum of three lines of systemic therapy, participated in semi-structured concept elicitation interviews. Concept saturation was assessed. A sign, symptom, or impact was defined as "salient" if mentioned by ≥ 60% of participants, with an average bother rating of ≥ 5 (0-10 Scale). Participants were also asked about treatment priorities and to evaluate hypothetical scenarios showing different health-related functioning and quality-of-life treatment outcomes, using graphical representations. RESULTS: Thirty-two participants (97% women; aged 29+ years) with TNBC (n = 17) or HR+/HER2- breast cancer (n = 15) provided generally similar reports on symptom experience, with fatigue and pain being most salient, though importance of certain treatment-related symptoms varied between the two groups. Patients reported consistent perspectives on the importance of treatment outcomes: when considering a new treatment, they prioritized efficacy of the therapy, acceptable tolerability, stability, predictability of symptoms over time, and the duration of preserved health-related quality of life and physical functioning. The meaningful difference in preserved physical functioning was 2-3 months for 46% of participants with TNBC, whereas for most participants with HR+/HER2- breast cancer it started from 6-7 months. Both groups of participants found it easier to accept some toxicity at the beginning of therapy if it was followed by improvement, as opposed to improvement followed by deterioration. CONCLUSION: The results may help to inform the design of patient-centered clinical trials, to interpret health-related quality of life and/or patient-reported outcomes, and to optimize care for patients with advanced breast cancer.

Fulvestrant plus capivasertib versus placebo after relapse or progression on an aromatase inhibitor in metastatic, oestrogen receptor-positive, HER2-negative breast cancer (FAKTION): overall survival, updated progression-free survival, and expanded biomarker analysis from a randomised, phase 2 trial.

BACKGROUND: Capivasertib, an AKT inhibitor, added to fulvestrant, was previously reported to improve progression-free survival in women with aromatase inhibitor-resistant oestrogen receptor (ER)-positive, HER2-negative advanced breast cancer. The benefit appeared to be independent of the phosphoinositide 3-kinase (PI3K)/AKT/phosphatase and tensin homologue (PTEN) pathway alteration status of tumours, as ascertained using assays available at the time. Here, we report updated progression-free survival and overall survival results, and a prespecified examination of the effect of PI3K/AKT/PTEN pathway alterations identified by an expanded genetic testing panel on treatment outcomes. METHODS: This randomised, multicentre, double-blind, placebo-controlled, phase 2 trial recruited postmenopausal adult women aged at least 18 years with ER-positive, HER2-negative, metastatic or locally advanced inoperable breast cancer and an Eastern Cooperative Oncology Group performance status of 0-2, who had relapsed or progressed on an aromatase inhibitor, from across 19 hospitals in the UK. Participants were randomly assigned (1:1) to receive intramuscular fulvestrant 500 mg (day 1) every 28 days (plus a 500 mg loading dose on day 15 of cycle 1) with either capivasertib 400 mg or matching placebo, orally twice daily on an intermittent weekly schedule of 4 days on and 3 days off, starting on cycle 1 day 15. Treatment continued until disease progression, unacceptable toxicity, loss to follow-up, or withdrawal of consent. Treatment was allocated by an interactive web-response system using a minimisation method (with a 20% random element) and the following minimisation factors: measurable or non-measurable disease, primary or secondary aromatase inhibitor resistance, PIK3CA status, and PTEN status. The primary endpoint was progression-free survival in the intention-to-treat population. Secondary endpoints shown in this Article were overall survival and safety in the intention-to-treat population, and the effect of tumour PI3K/AKT/PTEN pathway status identified by an expanded testing panel that included next-generation sequencing assays. Recruitment is complete. The trial is registered with ClinicalTrials.gov, number NCT01992952. FINDINGS: Between March 16, 2015, and March 6, 2018, 183 participants were screened for eligibility and 140 (77%) were randomly assigned to receive fulvestrant plus capivasertib (n=69) or fulvestrant plus placebo (n=71). Median follow-up at the data cut-off of Nov 25, 2021, was 58·5 months (IQR 45·9-64·1) for participants treated with fulvestrant plus capivasertib and 62·3 months (IQR 62·1-70·3) for fulvestrant plus placebo. Updated median progression-free survival was 10·3 months (95% CI 5·0-13·4) in the group receiving fulvestrant plus capivasertib compared with 4·8 months (3·1-7·9) for fulvestrant plus placebo (adjusted hazard ratio [HR] 0·56 [95% CI 0·38-0·81]; two-sided p=0·0023). Median overall survival in the capivasertib versus placebo groups was 29·3 months (95% CI 23·7-39·0) versus 23·4 months (18·7-32·7; adjusted HR 0·66 [95% CI 0·45-0·97]; two-sided p=0·035). The expanded biomarker panel identified an expanded pathway-altered subgroup that contained 76 participants (54% of the intention-to-treat population). Median progression-free survival in the expanded pathway-altered subgroup for participants receiving capivasertib (n=39) was 12·8 months (95% CI 6·6-18·8) compared with 4·6 months (2·8-7·9) in the placebo group (n=37; adjusted HR 0·44 [95% CI 0·26-0·72]; two-sided p=0·0014). Median overall survival for the expanded pathway-altered subgroup receiving capivasertib was 38·9 months (95% CI 23·3-50·7) compared with 20·0 months (14·8-31·4) for those receiving placebo (adjusted HR 0·46 [95% CI 0·27-0·79]; two-sided p=0·0047). By contrast, there were no statistically significant differences in progression-free or overall survival in the expanded pathway non-altered subgroup treated with capivasertib (n=30) versus placebo (n=34). One additional serious adverse event (pneumonia) in the capivasertib group had occurred subsequent to the primary analysis. One death, due to atypical pulmonary infection, was assessed as possibly related to capivasertib treatment. INTERPRETATION: Updated FAKTION data showed that capivasertib addition to fulvestrant extends the survival of participants with aromatase inhibitor-resistant ER-positive, HER2-negative advanced breast cancer. The expanded biomarker testing suggested that capivasertib predominantly benefits patients with PI3K/AKT/PTEN pathway-altered tumours. Phase 3 data are needed to substantiate the results, including in patients with previous CDK4/6 inhibitor exposure who were not included in the FAKTION trial. FUNDING: AstraZeneca and Cancer Research UK.

Serial monitoring of genomic alterations in circulating tumor cells of ER-positive/HER2-negative advanced breast cancer: feasibility of precision oncology biomarker detection.

Nearly all estrogen receptor (ER)-positive (POS) metastatic breast cancers become refractory to endocrine (ET) and other therapies, leading to lethal disease presumably due to evolving genomic alterations. Timely monitoring of the molecular events associated with response/progression by serial tissue biopsies is logistically difficult. Use of liquid biopsies, including circulating tumor cells (CTC) and circulating tumor DNA (ctDNA), might provide highly informative, yet easily obtainable, evidence for better precision oncology care. Although ctDNA profiling has been well investigated, the CTC precision oncology genomic landscape and the advantages it may offer over ctDNA in ER-POS breast cancer remain largely unexplored. Whole-blood (WB) specimens were collected at serial time points from patients with advanced ER-POS/HER2-negative (NEG) advanced breast cancer in a phase I trial of AZD9496, an oral selective ER degrader (SERD) ET. Individual CTC were isolated from WB using tandem CellSearch® /DEPArray™ technologies and genomically profiled by targeted single-cell DNA next-generation sequencing (scNGS). High-quality CTC (n = 123) from 12 patients profiled by scNGS showed 100% concordance with ctDNA detection of driver estrogen receptor α (ESR1) mutations. We developed a novel CTC-based framework for precision medicine actionability reporting (MI-CTCseq) that incorporates novel features, such as clonal predominance and zygosity of targetable alterations, both unambiguously identifiable in CTC compared to ctDNA. Thus, we nominated opportunities for targeted therapies in 73% of patients, directed at alterations in phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), fibroblast growth factor receptor 2 (FGFR2), and KIT proto-oncogene, receptor tyrosine kinase (KIT). Intrapatient, inter-CTC genomic heterogeneity was observed, at times between time points, in subclonal alterations. Our analysis suggests that serial monitoring of the CTC genome is feasible and should enable real-time tracking of tumor evolution during progression, permitting more combination precision medicine interventions.

Concentration-QT modelling shows no evidence of clinically significant QT interval prolongation with capivasertib at expected therapeutic concentrations.

Pharmacokinetics-matched digital electrocardiogram data (n = 503 measurements from 180 patients) collected in a first-in-human, multi-part, dose-escalation (from 80 to 800 mg) and dose expansion (at 480 mg) phase 1 study in patients with advanced solid malignancies, were used to assess potential risk of QT prolongation associated with the AKT inhibitor capivasertib. The relationship between plasma drug concentrations and baseline-adjusted Fridericia-corrected QT (ΔQTcF) values was estimated using a prespecified linear mixed-effects model. The model provided an unbiased reproduction of the experimental data set, estimating a small but positive correlation between capivasertib concentration and ΔQTcF. At the expected therapeutic dose (400 mg twice daily) the predicted mean ΔQTcF at the steady state maximum concentration was 3.97 ms with an upper limit of the 90% CI of 5.07 ms; below the 10 ms limit proposed by ICH E14 guidance. This analysis suggests that capivasertib is not expected to present a clinically significant risk for QT prolongation that is associated with pro-arrhythmic effects.

Utility of Serial cfDNA NGS for Prospective Genomic Analysis of Patients on a Phase I Basket Study.

PURPOSE: Cell-free DNA (cfDNA) analysis offers a noninvasive means to access the tumor genome. Despite limited sensitivity of broad-panel sequencing for detecting low-frequency mutations in cfDNA, it may enable more comprehensive genomic characterization in patients with sufficiently high disease burden. We investigated the utility of large-panel cfDNA sequencing in patients enrolled to a Phase I AKT1-mutant solid tumor basket study. METHODS: Patients had AKT1 E17K-mutant solid tumors and were treated on the multicenter basket study (ClinicalTrials.gov identifier: NCT01226316) of capivasertib, an AKT inhibitor. Serial plasma samples were prospectively collected and sequenced using exon-capture next-generation sequencing (NGS) analysis of 410 genes (Memorial Sloan Kettering [MSK]-Integrated Molecular Profiling of Actionable Cancer Target [IMPACT]) and allele-specific droplet digital polymerase chain reaction (ddPCR) for AKT1 E17K. Tumor DNA (tDNA) NGS (MSK-IMPACT) was also performed on available pretreatment tissue biopsy specimens. RESULTS: Among 25 patients, pretreatment plasma samples were sequenced to an average coverage of 504×. Somatic mutations were called in 20/25 (80%), with mutant allele fractions highly concordant with ddPCR of AKT1 E17K (r 2 = 0.976). Among 17 of 20 cfDNA-positive patients with available tDNA for comparison, mutational concordance was acceptable, with 82% of recurrent mutations shared between tissue and plasma. cfDNA NGS captured additional tumor heterogeneity, identifying mutations not observed in tDNA in 38% of patients, and revealed oncogenic mutations in patients without available baseline tDNA. Longitudinal cfDNA NGS (n = 98 samples) revealed distinct patterns of clonal dynamics in response to therapy. CONCLUSION: Large gene panel cfDNA NGS is feasible for patients with high disease burden and is concordant with single-analyte approaches, providing a robust alternative to ddPCR with greater breadth. cfDNA NGS can identify heterogeneity and potentially biologically informative and clinically relevant alterations.

Selective AKT kinase inhibitor capivasertib in combination with fulvestrant in PTEN-mutant ER-positive metastatic breast cancer.

Five to ten percent of ER+ metastatic breast cancer (MBC) tumors harbor somatic PTEN mutations. Loss of function of this tumor-suppressor gene defines a highly aggressive, treatment-refractory disease for which new therapies are urgently needed. This Phase I multipart expansion study assessed oral capivasertib with fulvestrant in patients with PTEN-mutant ER+ MBC. Safety and tolerability were assessed by standard methods. Plasma and tumor were collected for NGS and immunohistochemistry analyses of PTEN protein expression. In 31 eligible patients (12 fulvestrant naive; 19 fulvestrant pretreated), the 24-week clinical benefit rate was 17% in fulvestrant-naive and 42% in fulvestrant-pretreated patients, with objective response rate of 8% and 21%, respectively. Non-functional PTEN was centrally confirmed in all cases by NGS or immunohistochemistry. Co-mutations occurred in PIK3CA (32%), with less ESR1 (10% vs 72%) and more TP53 (40% vs 28%) alterations in fulvestrant-naive versus fulvestrant-pretreated patients, respectively. PTEN was clonally dominant in most patients. Treatment-related grade ≥3 adverse events occurred in 32% of patients, most frequently diarrhea and maculopapular rash (both n = 2). In this clinical study, which selectively targeted the aggressive PTEN-mutant ER+ MBC, capivasertib plus fulvestrant was tolerable and clinically active. Phenotypic and genomic differences were apparent between fulvestrant-naive and -pretreated patients.Trial registration number for the study is NCT01226316.

ESR1 Mutations and Overall Survival on Fulvestrant versus Exemestane in Advanced Hormone Receptor-Positive Breast Cancer: A Combined Analysis of the Phase III SoFEA and EFECT Trials.

PURPOSE: ESR1 mutations are acquired frequently in hormone receptor-positive metastatic breast cancer after prior aromatase inhibitors. We assessed the clinical utility of baseline ESR1 circulating tumor DNA (ctDNA) analysis in the two phase III randomized trials of fulvestrant versus exemestane. EXPERIMENTAL DESIGN: The phase III EFECT and SoFEA trials randomized patients with hormone receptor-positive metastatic breast cancer who had progressed on prior nonsteroidal aromatase inhibitor therapy, between fulvestrant 250 mg and exemestane. Baseline serum samples from 227 patients in EFECT, and baseline plasma from 161 patients in SoFEA, were analyzed for ESR1 mutations by digital PCR. The primary objectives were to assess the impact of ESR1 mutation status on progression-free (PFS) and overall survival (OS) in a combined analysis of both studies. RESULTS: ESR1 mutations were detected in 30% (151/383) baseline samples. In patients with ESR1 mutation detected, PFS was 2.4 months [95% confidence interval (CI), 2.0-2.6] on exemestane and 3.9 months (95% CI, 3.0-6.0) on fulvestrant [hazard ratio (HR), 0.59; 95% CI, 0.39-0.89; P = 0.01). In patients without ESR1 mutations detected, PFS was 4.8 months (95% CI, 3.7-6.2) on exemestane and 4.1 months (95% CI, 3.6-5.5) on fulvestrant (HR, 1.05; 95% CI, 0.81-1.37; P = 0.69). There was an interaction between ESR1 mutation and treatment (P = 0.02). Patients with ESR1 mutation detected had 1-year OS of 62% (95% CI, 45%-75%) on exemestane and 80% (95% CI, 68%-87%) on fulvestrant (P = 0.04; restricted mean survival analysis). Patients without ESR1 mutations detected had 1-year OS of 79% (95% CI, 71%-85%) on exemestane and 81% (95% CI, 74%-87%) on fulvestrant (P = 0.69). CONCLUSIONS: Detection of ESR1 mutations in baseline ctDNA is associated with inferior PFS and OS in patients treated with exemestane versus fulvestrant.

Capivasertib, an AKT Kinase Inhibitor, as Monotherapy or in Combination with Fulvestrant in Patients with AKT1 E17K-Mutant, ER-Positive Metastatic Breast Cancer.

PURPOSE: The activating mutation AKT1 E17K occurs in approximately 7% of estrogen receptor-positive (ER+) metastatic breast cancer (MBC). We report, from a multipart, first-in-human, phase I study (NCT01226316), tolerability and activity of capivasertib, an oral AKT inhibitor, as monotherapy or combined with fulvestrant in expansion cohorts of patients with AKT1 E17K-mutant ER+ MBC. PATIENTS AND METHODS: Patients with an AKT1 E17K mutation, detected by local (next-generation sequencing) or central (plasma-based BEAMing) testing, received capivasertib 480 mg twice daily, 4 days on, 3 days off, weekly or 400 mg twice daily combined with fulvestrant at the labeled dose. Study endpoints included safety, objective response rate (ORR; RECIST v1.1), progression-free survival (PFS), and clinical benefit rate at 24 weeks (CBR24). Biomarker analyses were conducted in the combination cohort. RESULTS: From October 2013 to August 2018, 63 heavily pretreated patients received capivasertib (20 monotherapy, 43 combination). ORR was 20% with monotherapy, and within the combination cohort was 36% in fulvestrant-pretreated and 20% in fulvestrant-naïve patients, although the latter group may have had more aggressive disease at baseline. AKT1 E17K mutations were detectable in plasma by BEAMing (95%, 41/43), droplet digital PCR (80%, 33/41), and next-generation sequencing (76%, 31/41). A ≥50% decrease in AKT1 E17K at cycle 2 day 1 was associated with improved PFS. Combination therapy appeared more tolerable than monotherapy [most frequent grade ≥3 adverse events: rash (9% vs. 20%), hyperglycemia (5% vs. 30%), diarrhea (5% vs. 10%)]. CONCLUSIONS: Capivasertib demonstrated clinically meaningful activity in heavily pretreated patients with AKT1 E17K-mutant ER+ MBC, including those with prior disease progression on fulvestrant. Tolerability and activity appeared improved by the combination.

A Randomized, Open-label, Presurgical, Window-of-Opportunity Study Comparing the Pharmacodynamic Effects of the Novel Oral SERD AZD9496 with Fulvestrant in Patients with Newly Diagnosed ER+ HER2- Primary Breast Cancer.

PURPOSE: Fulvestrant, the first-in-class selective estrogen receptor (ER) degrader (SERD), is clinically effective in patients with ER+ breast cancer, but it has administration and pharmacokinetic limitations. Pharmacodynamic data suggest complete ER degradation is not achieved at fulvestrant's clinically feasible dose. This presurgical study (NCT03236974) compared the pharmacodynamic effects of fulvestrant with AZD9496, a novel, orally bioavailable, nonsteroidal, potent SERD, in treatment-naïve patients with ER+ HER2- primary breast cancer awaiting curative intent surgery. PATIENTS AND METHODS: Patients were randomized 1:1 to receive AZD9496 250 mg twice daily from day 1 for 5-14 days, or fulvestrant 500 mg on day 1. On-treatment imaging-guided core tumor biopsies were taken between day 5 and 14 and compared with pretreatment diagnostic biopsies. The primary objective was to compare the effects of AZD9496 and fulvestrant on ER expression. Secondary objectives included changes in progesterone receptor (PR) and Ki-67 pharmacokinetic/pharmacodynamic relationships and safety. RESULTS: Forty-six women received treatment (AZD9496 n = 22; fulvestrant n = 24); 35 paired biopsies were evaluable (AZD9496 n = 15; fulvestrant n = 20). The least square mean estimate for ER H-score reduction was 24% after AZD9496 versus 36% after fulvestrant treatment (P = 0.86). AZD9496 also reduced PR H-scores (-33.3%) and Ki-67 levels (-39.9%) from baseline, but was also not superior to fulvestrant (PR: -68.7%, P = 0.97; Ki-67: -75.4%, P = 0.98). No new safety findings were identified. CONCLUSIONS: This was the first presurgical study to demonstrate that an oral SERD affects its key biological targets. However, AZD9496 was not superior to fulvestrant at the dose tested.

Mapping the breast cancer metastatic cascade onto ctDNA using genetic and epigenetic clonal tracking.

Circulating tumour DNA (ctDNA) allows tracking of the evolution of human cancers at high resolution, overcoming many limitations of tissue biopsies. However, exploiting ctDNA to determine how a patient's cancer is evolving in order to aid clinical decisions remains difficult. This is because ctDNA is a mix of fragmented alleles, and the contribution of different cancer deposits to ctDNA is largely unknown. Profiling ctDNA almost invariably requires prior knowledge of what genomic alterations to track. Here, we leverage on a rapid autopsy programme to demonstrate that unbiased genomic characterisation of several metastatic sites and concomitant ctDNA profiling at whole-genome resolution reveals the extent to which ctDNA is representative of widespread disease. We also present a methylation profiling method that allows tracking evolutionary changes in ctDNA at single-molecule resolution without prior knowledge. These results have critical implications for the use of liquid biopsies to monitor cancer evolution in humans and guide treatment.

Genetic Alterations in the PI3K/AKT Pathway and Baseline AKT Activity Define AKT Inhibitor Sensitivity in Breast Cancer Patient-derived Xenografts.

PURPOSE: AZD5363/capivasertib is a pan-AKT catalytic inhibitor with promising activity in combination with paclitaxel in triple-negative metastatic breast cancer harboring PI3K/AKT-pathway alterations and in estrogen receptor-positive breast cancer in combination with fulvestrant. Here, we aimed to identify response biomarkers and uncover mechanisms of resistance to AZD5363 and its combination with paclitaxel. EXPERIMENTAL DESIGN: Genetic and proteomic markers were analyzed in 28 HER2-negative patient-derived xenografts (PDXs) and in patient samples, and correlated to AZD5363 sensitivity as single agent and in combination with paclitaxel. RESULTS: Four PDX were derived from patients receiving AZD5363 in the clinic which exhibited concordant treatment response. Mutations in PIK3CA/AKT1 and absence of mTOR complex 1 (mTORC1)-activating alterations, for example, in MTOR or TSC1, were associated with sensitivity to AZD5363 monotherapy. Interestingly, excluding PTEN from the composite biomarker increased its accuracy from 64% to 89%. Moreover, resistant PDXs exhibited low baseline pAKT S473 and residual pS6 S235 upon treatment, suggesting that parallel pathways bypass AKT/S6K1 signaling in these models. We identified two mechanisms of acquired resistance to AZD5363: cyclin D1 overexpression and loss of AKT1 p.E17K. CONCLUSIONS: This study provides insight into putative predictive biomarkers of response and acquired resistance to AZD5363 in HER2-negative metastatic breast cancer.

Proliferation and AKT Activity Biomarker Analyses after Capivasertib (AZD5363) Treatment of Patients with ER+ Invasive Breast Cancer (STAKT).

PURPOSE: The STAKT study examined short-term exposure (4.5 days) to the oral selective pan-AKT inhibitor capivasertib (AZD5363) to determine if this drug can reach its therapeutic target in sufficient concentration to significantly modulate key biomarkers of the AKT pathway and tumor proliferation. PATIENTS AND METHODS: STAKT was a two-stage, double-blind, randomized, placebo-controlled, "window-of-opportunity" study in patients with newly diagnosed ER+ invasive breast cancer. Stage 1 assessed capivasertib 480 mg b.i.d. (recommended monotherapy dose) and placebo, and stage 2 assessed capivasertib 360 and 240 mg b.i.d. Primary endpoints were changes from baseline in AKT pathway markers pPRAS40, pGSK3ß, and proliferation protein Ki67. Pharmacologic and pharmacodynamic properties were analyzed from blood sampling, and tolerability by adverse-event monitoring. RESULTS: After 4.5 days' exposure, capivasertib 480 mg b.i.d. (n = 17) produced significant decreases from baseline versus placebo (n = 11) in pGSK3ß (H-score absolute change: -55.3, P = 0.006) and pPRAS40 (-83.8, P < 0.0001), and a decrease in Ki67 (absolute change in percentage positive nuclei: -9.6%, P = 0.031). Significant changes also occurred in secondary signaling biomarker pS6 (-42.3, P = 0.004), while pAKT (and nuclear FOXO3a) also increased in accordance with capivasertib's mechanism (pAKT: 81.3, P = 0.005). At doses of 360 mg b.i.d. (n = 5) and 240 mg b.i.d. (n = 6), changes in primary and secondary biomarkers were also observed, albeit of smaller magnitude. Biomarker modulation was dose and concentration dependent, and no new safety signals were evident. CONCLUSIONS: Capivasertib 480 mg b.i.d. rapidly modulates key biomarkers of the AKT pathway and decreases proliferation marker Ki67, suggesting future potential as an effective therapy in AKT-dependent breast cancers.

Prognostic role of serum thymidine kinase 1 activity in patients with hormone receptor-positive metastatic breast cancer: Analysis of the randomised phase III Evaluation of Faslodex versus Exemestane Clinical Trial (EFECT).

BACKGROUND: Thymidine kinase 1 (TK1) plays a critical role in DNA synthesis and cell proliferation. Recent studies have shown potential for serum TK1 activity (sTKa) as a prognostic marker and indicator of early response to endocrine therapy in advanced breast cancer. The aim of this study is to assess the correlation between sTKa and patient outcome. PATIENTS AND METHODS: The Evaluation of Faslodex versus Exemestane Clinical Trial (EFECT) was a double-blind, double-dummy, randomised trial of fulvestrant versus exemestane after progression on non-steroidal aromatase inhibitor therapy, in postmenopausal women with advanced breast cancer. Retrospective analyses of serum archived from EFECT were conducted. sTKa was assessed using the DiviTum® assay on samples collected at baseline, after three and six months of endocrine therapy, and at disease progression. RESULTS: The median time to progression (mTTP) for patients with low baseline sTKa levels was 5.03 months (95% confidence interval [CI]: 3.91-5.89) versus 2.57 months (95% CI: 2.04-3.52) in patients with high sTKa baseline levels (P < 0.0001). On treatment, patients whose sTKa increased from baseline had a significantly shorter mTTP (3.39 months, 95% CI: 2.14-4.11) than those without an sTKa increase (5.39 months, 95% CI: 4.01-6.68) (P = 0.0045). Similar results were observed in the separate EFECT treatment arms. After adjusting for major prognostic factors, sTKa remained an independent marker. CONCLUSION: sTKa is a potential circulating prognostic marker in patients with advanced breast cancer treated with endocrine therapy. It may also represent a tool for upfront identification of endocrine therapy resistance and early positive response to therapy. Independent validation of these results is warranted.

Author Correction: The Rho GTPase Rnd1 suppresses mammary tumorigenesis and EMT by restraining Ras-MAPK signalling.

In the version of this Article originally published the same blot was inadvertently presented as both p-Rb and Cyclin A in Fig. 2a. This blot corresponds to the p-Rb panel, as can be seen in the unprocessed version of these blots in Supplementary Fig. 9. The corrected version of the panel is shown below, together with a completely uncropped image of both blots. In addition, in the 'Viral transduction' section of the Methods, the pLKO.1 plasmids encoding short hairpin RNAs targeting human Rnd1 were incorrectly listed as clones TRCN0000018338 and TRCN0000039977. The correct clone numbers are TRCN0000047434 and TRCN0000047435.

Circulating Biomarkers and Resistance to Endocrine Therapy in Metastatic Breast Cancers: Correlative Results from AZD9496 Oral SERD Phase I Trial.

PURPOSE: Common resistance mechanisms to endocrine therapy (ET) in estrogen receptor (ER)-positive metastatic breast cancers include, among others, ER loss and acquired activating mutations in the ligand-binding domain of the ER gene (ESR1LBDm). ESR1 mutational mediated resistance may be overcome by selective ER degraders (SERD). During the first-in-human study of oral SERD AZD9496, early changes in circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) were explored as potential noninvasive tools, alongside paired tumor biopsies, to assess pharmacodynamics and early efficacy. EXPERIMENTAL DESIGN: CTC were enumerated/phenotyped for ER and Ki67 using CellSearch in serial blood draws. ctDNA was assessed for the most common ESR1LBDm by droplet digital PCR (BioRad). RESULTS: Before starting AZD9496, 11 of 43 (25%) patients had ≥5 CTC/7.5 mL whole blood (WB), none of whom underwent reduction to <5 CTC/7.5 mL WB on C1D15. Five of 11 patients had baseline CTC-ER+, two of whom had CTC-ER+ reduction. CTC-Ki67 status did not change appreciably. Patients with ≥5 CTC/7.5 mL WB before treatment had worse progression-free survival (PFS) than patients with <5 CTC (P = 0.0003). Fourteen of 45 (31%) patients had ESR1LBDm + ctDNA at baseline, five of whom had ≥2 unique mutations. Baseline ESR1LBDm status was not prognostic. Patients with persistently elevated CTC and/or ESR1LBDm + ctDNA at C1D15 had worse PFS than patients who did not (P = 0.0007). CONCLUSIONS: Elevated CTC at baseline was a strong prognostic factor in this cohort. Early on-treatment changes were observed in CTC-ER+ and ESR1LBDm + ctDNA, but not in overall CTC number. Integrating multiple biomarkers in prospective trials may improve outcome prediction and ET resistance mechanisms' identification over a single biomarker.