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Among persons with breast cancer previously treated with hormonal therapy, the AKT pathway inhibitor capivasertib when added to fulvestrant significantly prolonged progression-free survival as compared with fulvestrant alone.

PIK3CA mutations occur in approximately 40% of patients with hormone receptor–positive breast cancer. A PI3K inhibitor, alpelisib, combined with fulvestrant led to a median progression-free survival of 11 months, as compared with 5.7 months with placebo plus fulvestrant. Hyperglycemia, rash, and diarrhea were more common with alpelisib.

Approximately 75% of all breast cancers express the oestrogen and/or progesterone receptors. Endocrine therapy is usually effective in these hormone-receptor-positive tumours, but primary and acquired resistance limits its long-term benefit 1 , 2 . Here we show that in mouse models of hormone-receptor-positive breast cancer, periodic fasting or a fasting-mimicking diet 3 – 5 enhances the activity of the endocrine therapeutics tamoxifen and fulvestrant by lowering circulating IGF1, insulin and leptin and by inhibiting AKT–mTOR signalling via upregulation of EGR1 and PTEN. When fulvestrant is combined with palbociclib (a cyclin-dependent kinase 4/6 inhibitor), adding periodic cycles of a fasting-mimicking diet promotes long-lasting tumour regression and reverts acquired resistance to drug treatment. Moreover, both fasting and a fasting-mimicking diet prevent tamoxifen-induced endometrial hyperplasia. In patients with hormone-receptor-positive breast cancer receiving oestrogen therapy, cycles of a fasting-mimicking diet cause metabolic changes analogous to those observed in mice, including reduced levels of insulin, leptin and IGF1, with the last two remaining low for extended periods. In mice, these long-lasting effects are associated with long-term anti-cancer activity. These results support further clinical studies of a fasting-mimicking diet as an adjuvant to oestrogen therapy in hormone-receptor-positive breast cancer. In mice, periodic fasting or a fasting-mimicking diet enhances the efficacy of endocrine therapy for breast cancer and delays acquired resistance to it; in patients with breast cancer, a fasting-mimicking diet recreates the metabolic changes observed in mice.

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. 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. 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). 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. Cancer Research UK, AstraZeneca, and Puma Biotechnology.

CAPItello-291 is an ongoing phase 3 trial in which capivasertib–fulvestrant significantly improved progression-free survival versus placebo–fulvestrant in patients with hormone receptor-positive, HER2-negative advanced breast cancer who had relapse or disease progression during or after aromatase inhibitor treatment, in both the overall population and in patients with PIK3CA, AKT1, or PTEN-altered tumours. This study further explored patient-reported health-related quality of life (HRQOL), functioning, symptoms, and symptom tolerability in CAPItello-291. This phase 3, randomised, double-blind, placebo-controlled trial, which was conducted across 193 hospitals and cancer centres in 19 countries, enrolled women with any menopausal status or men, aged ≥18 years (≥20 years in Japan), with hormone receptor-positive, HER2-negative locally advanced or metastatic breast cancer who had relapse or disease progression during or after treatment with an aromatase inhibitor, with or without previous cyclin-dependent kinase (CDK) 4 or 6 inhibitor therapy. Patients had an Eastern Cooperative Oncology Group/WHO performance score of 0 or 1 and could have received up to two previous lines of endocrine therapy and up to one previous line of chemotherapy for advanced disease. Patients were randomly assigned (1:1) using block randomisation (stratified according to the presence or absence of liver metastases, previous use of a CDK4/6 inhibitor [yes vs no], and geographical region) to receive oral capivasertib 400 mg (twice daily for 4 days, followed by 3 days off) plus intramuscular fulvestrant 500 mg (every 14 days for the first three injections, then every 28 days) or placebo with matching fulvestrant dosing. The dual primary endpoint of the trial was investigator-assessed progression-free survival assessed both in the overall population and among patients with PIK3CA, AKT1, or PTEN-altered tumours. The EORTC Quality of Life Questionnaire 30-item core module (QLQ-C30) and breast module (QLQ-BR23), Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE), and Patient Global Impression of Treatment Tolerability (PGI-TT) questionnaires were used to assess patient-reported outcomes. Evaluation of EORTC QLQ-C30 and EORTC QLQ-BR23 were secondary endpoints and evaluation of PRO-CTCAE and PGI-TT were pre-defined exploratory endpoints, and these endpoints are the subject of analysis in this Article. Data were collected at baseline and prespecified timepoints. Patient-reported outcomes were analysed in all randomly assigned patients with an evaluable baseline assessment and at least one evaluable post-baseline assessment. Change from baseline was assessed using mixed model with repeated measures for EORTC QLQ-C30 and summarised for QLQ-BR23. Time to deterioration was described using the Kaplan–Meier method. PGI-TT and PRO-CTCAE responses were summarised at each treatment cycle. Patient-reported outcomes were not prospectively powered for statistical comparison. The trial is registered with ClinicalTrials.gov, NCT04305496. Between June 2, 2020, and Oct 13, 2021, 901 patients were enrolled, of whom 708 patients were randomly assigned to receive capivasertib–fulvestrant (n=355) or placebo–fulvestrant (n=353). The median age of the patients was 59 years (IQR 51–67) in the capivasertib–fulvestrant group and 58 years (IQR 49–66) in the placebo–fulvestrant group. At data cutoff (Aug 15, 2022), the median duration of follow-up for progression-free survival in censored patients was 13·0 months (IQR 9·1–16·7) for capivasertib–fulvestrant and 12·7 months (IQR 2·0–16·4) for placebo–fulvestrant in the overall population. EORTC QLQ-C30 global health status/quality of life (GHS/QOL) scores were maintained from baseline and were similar between treatment groups throughout the study period (difference in mean change from baseline of −2·5 [95% CI −4·5 to −0·6] with capivasertib–fulvestrant vs −5·6 [−7·9 to −3·4] with placebo–fulvestrant; treatment difference 3·1 [95% CI 0·2 to 6·0]). Median time to deterioration in EORTC QLQ-C30 GHS/QOL was 24·9 months (95% CI 13·8 to not reached) in the capivasertib–fulvestrant group and 12·0 months (10·2 to 15·7) in the placebo–fulvestrant group (hazard ratio [HR] 0·70, 95% CI 0·53 to 0·92). Time to deterioration HRs for all EORTC QLQ-C30 and QLQ-BR23 subscale scores showed little difference between the treatment groups, except for diarrhoea, which was worse in the capivasertib–fulvestrant group than in the placebo–fulvestrant group (HR 2·75, 95% CI 2·01–3·81). In PRO-CTCAE symptom assessment, the proportion of patients reporting loose and watery stools “frequently” or “almost constantly” was 29% higher at cycle 1, day 15 in the capivasertib–fulvestrant group than in the placebo–fulvestrant group, decreasing at subsequent cycles. Other PRO-CTCAE-reported symptoms (rash, mouth or throat sores, itchy skin, and numbness or tingling in hands or feet) were absent or mild in most patients in both groups throughout treatment. According to the PGI-TT, most patients in both groups reported “not at all” or “a little bit” of bother from treatment side-effects. Patient-reported outcomes from CAPItello-291 demonstrated that capivasertib–fulvestrant delayed time to deterioration of GHS/QOL and maintained other dimensions of HRQOL (except symptoms of diarrhoea) similarly to fulvestrant. With the clinical efficacy and manageable safety profile, these exploratory results further support the positive benefit–risk profile of capivasertib–fulvestrant in this population. AstraZeneca.

Blockade of the cyclin-dependent kinase 4 and 6 pathway has been shown to be effective in the treatment of hormone receptor-positive advanced breast cancer (ABC). We report the interim results of DAWNA-1 ( NCT03927456 ), a double-blind, randomized, phase 3 trial of dalpiciclib (a new cyclin-dependent kinase 4 and 6 inhibitor) plus fulvestrant in hormone receptor-positive, HER2-negative ABC with disease progression after endocrine therapy. A total of 361 patients were randomized 2:1 to receive dalpiciclib plus fulvestrant or placebo plus fulvestrant. The study met the primary end point, showing significantly prolonged investigator-assessed progression-free survival with dalpiciclib plus fulvestrant versus placebo plus fulvestrant (median = 15.7, 95% confidence interval (CI) = 11.1–not reached versus 7.2, 95% CI = 5.6–9.2 months; hazard ratio = 0.42, 95% CI = 0.31–0.58; one-sided P  < 0.0001 (boundary was P ≤ 0.008)). The most common grade 3 or 4 adverse events with dalpiciclib plus fulvestrant were neutropenia (84.2%) and leukopenia (62.1%). The incidence of serious adverse events was 5.8% with dalpiciclib plus fulvestrant versus 6.7% with placebo plus fulvestrant. Our findings support dalpiciclib plus fulvestrant as a new treatment option for pretreated hormone receptor-positive, HER2-negative ABC. In the multicenter, phase 3 DAWNA-1 trial, the combination of dalpiciclib, a new cyclin-dependent kinase 4 and 6 inhibitor, with fulvestrant, in patients with HR + HER2 − advanced breast cancer who progressed or relapsed on endocrine therapy, improved progression-free survival with manageable safety and may represent a new treatment option.

Cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) in combination with endocrine therapy improve the outcomes of patients with hormone-receptor (HR)-positive, HER2-negative advanced breast cancer and can be used early as first-line treatment or deferred to second-line treatment 1 , 2 , 3 , 4 , 5 , 6 – 7 . Randomized data comparing the use of CDK4/6i in the first- and second-line setting are lacking. The phase 3 SONIA trial (NCT03425838) randomized 1,050 patients who had not received previous therapy for advanced breast cancer to receive CDK4/6i in the first- or second-line setting 8 . All of the patients received the same endocrine therapy, consisting of an aromatase inhibitor for first-line treatment and fulvestrant for second-line treatment. The primary end point was defined as the time from randomization to disease progression after second-line treatment (progression-free survival 2 (PFS2)). We observed no statistically significant benefit for the use of CDK4/6i as a first-line compared with second-line treatment (median, 31.0 versus 26.8 months, respectively; hazard ratio = 0.87; 95% confidence interval = 0.74–1.03; P  = 0.10). The health-related quality of life was similar in both groups. First-line CDK4/6i use was associated with a longer CDK4/6i treatment duration compared with second-line use (median CDK4/6i treatment duration of 24.6 versus 8.1 months, respectively) and more grade ≥3 adverse events (2,763 versus 1,591, respectively). These data challenge the need for first-line use of a CDK4/6i in all patients. The phase 3 SONIA trial challenges the benefits of using cyclin-dependent kinase 4 and 6 inhibitors as a first-line compared with second-line treatment.

The BRIGHT-2 study (NCT05077449) is a randomized, double-blind, placebo-controlled, phase 3 trial evaluating the efficacy and safety of bireociclib plus fulvestrant (BF) vs. placebo plus fulvestrant (F) in Chinese female patients with hormone receptor-positive (HR+)/HER2-negative (HER2-) advanced breast cancer (ABC) who had progressed on or after prior endocrine therapy (ET). Interim results were analyzed after 70% of progression-free survival (PFS) events across 64 centers in China between December 8, 2021, and March 28, 2023. Patients were randomized (2:1) to receive BF or F, with stratification based on visceral involvement (yes/no) and resistance to prior primary or secondary ET. As the primary outcome, PFS was significantly prolonged in the BF group ( n  = 204) (12.94 months; 95% CI: 11.07–not reached) compared to 7.29 months (95% CI: 5.45–11.04) in the F group ( n  = 101) (hazard ratio, 0.56; 95% CI: 0.39–0.80; p  = 0.001). The objective response rate in the BF group was 39.7% in the intention-to-treat population. Grade ≥3 adverse events were more frequent in the BF group (64.7%) than in the F group (18.8%), with neutropenia, leukopenia, and anemia being the most common. These findings suggest that BF is a promising therapeutic option for patients with HR+/HER2- ABC following ET failure. While CDK4/6 inhibitors have become standard of care in patients with HR+/HER2- advanced breast cancer (ABC), selecting the optimal inhibitor could improve care further. Here, the authors report planned interim analysis of the BRIGHT-2 study, a randomised phase 3 trial comparing bireociclib (CDK4/6i) and fulvestrant (ET) against placebo and fulvestrant in female HR + /HER2- ABC patients.

Inhibition of histone lysine acetyltransferases (KATs) KAT6A and KAT6B has shown antitumor activity in estrogen receptor-positive (ER + ) breast cancer preclinical models. PF-07248144 is a selective catalytic inhibitor of KAT6A and KAT6B. In the present study, we report the safety, pharmacokinetics (PK), pharmacodynamics, efficacy and biomarker results from the first-in-human, phase 1 dose escalation and dose expansion study ( n  = 107) of PF-07248144 monotherapy and fulvestrant combination in heavily pretreated ER + human epidermal growth factor receptor-negative (HER2 − ) metastatic breast cancer (mBC). The primary objectives of assessing the safety and tolerability and determining the recommended dose for expansion of PF-07248144, as monotherapy and in combination with fulvestrant, were met. Secondary endpoints included characterization of PK and evaluation of antitumor activity, including objective response rate (ORR) and progression-free survival (PFS). Common treatment-related adverse events (any grade; grades 3–4) included dysgeusia (83.2%, 0%), neutropenia (59.8%, 35.5%) and anemia (48.6%, 13.1%). Exposure was approximately dose proportional. Antitumor activity was observed as monotherapy. For the PF-07248144–fulvestrant combination ( n  = 43), the ORR (95% confidence interval (CI)) was 30.2% (95% CI = 17.2–46.1%) and the median PFS was 10.7 (5.3–not evaluable) months. PF-07248144 demonstrated a tolerable safety profile and durable antitumor activity in heavily pretreated ER + HER2 − mBC. These findings establish KAT6A and KAT6B as druggable cancer targets, provide clinical proof of concept and reveal a potential avenue to treat mBC. clinicaltrial.gov registration: NCT04606446 . In this phase 1 trial, treatment of patients with ER + HER2 − metastatic breast cancer with a selective catalytic inhibitor of the lysine acetyltransferase KAT6 shows a manageable safety profile and encouraging preliminary clinical efficacy.

Background Endocrine therapy remains the mainstay of treatment for estrogen receptor-positive (ER+) breast cancer. Constitutively active mutations in the ligand binding domain of ERα render tumors resistant to endocrine agents. Breast cancers with the two most common ERα mutations, Y537S and D538G, have low sensitivity to fulvestrant inhibition, a typical second-line endocrine therapy. Lasofoxifene is a selective estrogen receptor modulator with benefits on bone health and breast cancer prevention potential. This study investigated the anti-tumor activity of lasofoxifene in breast cancer xenografts expressing Y537S and D538G ERα mutants. The combination of lasofoxifene with palbociclib, a CDK4/6 inhibitor, was also evaluated. Methods Luciferase-GFP tagged MCF7 cells bearing wild-type, Y537S, or D538G ERα were injected into the mammary ducts of NSG mice (MIND model), which were subsequently treated with lasofoxifene or fulvestrant as single agents or in combination with palbociclib. Tumor growth and metastasis were monitored with in vivo and ex vivo luminescence imaging, terminal tumor weight measurements, and histological analysis. Results As a monotherapy, lasofoxifene was more effective than fulvestrant at inhibiting primary tumor growth and reducing metastases. Adding palbociclib improved the effectiveness of both lasofoxifene and fulvestrant for tumor suppression and metastasis prevention at four distal sites (lung, liver, bone, and brain), with the combination of lasofoxifene/palbociclib being generally more potent than that of fulvestrant/palbociclib. X-ray crystallography of the ERα ligand binding domain (LBD) shows that lasofoxifene stabilizes an antagonist conformation of both wild-type and Y537S LBD. The ability of lasofoxifene to promote an antagonist conformation of Y537S, combined with its long half-life and bioavailability, likely contributes to the observed potent inhibition of primary tumor growth and metastasis of MCF7 Y537S cells. Conclusions We report for the first time the anti-tumor activity of lasofoxifene in mouse models of endocrine therapy-resistant breast cancer. The results demonstrate the potential of using lasofoxifene as an effective therapy for women with advanced or metastatic ER+ breast cancers expressing the most common constitutively active ERα mutations.