Datopotamab Deruxtecan Versus Chemotherapy in Previously Treated Inoperable/Metastatic Hormone Receptor-Positive Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer: Primary Results From TROPION-Breast01.

PURPOSE: The global, phase 3, open-label, randomized TROPION-Breast01 study assessed the trophoblast cell surface antigen 2-directed antibody-drug conjugate datopotamab deruxtecan (Dato-DXd) versus investigator's choice of chemotherapy (ICC) in hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer. METHODS: Adult patients with inoperable/metastatic HR+/HER2‒ breast cancer, who had disease progression on endocrine therapy, for whom endocrine therapy was unsuitable, and had received one to two previous lines of chemotherapy in the inoperable/metastatic setting, were randomly assigned 1:1 to Dato-DXd (6 mg/kg once every 3 weeks) or ICC (eribulin/vinorelbine/capecitabine/gemcitabine). Dual primary end points were progression-free survival (PFS) by blinded independent central review (BICR) and overall survival (OS). RESULTS: Patients were randomly assigned to Dato-DXd (n = 365) or ICC (n = 367). Dato-DXd significantly reduced the risk of progression or death versus ICC (PFS by BICR hazard ratio [HR], 0.63 [95% CI, 0.52 to 0.76]; P < .0001). Consistent PFS benefit was observed across subgroups. Although OS data were not mature, a trend favoring Dato-DXd was observed (HR, 0.84 [95% CI, 0.62 to 1.14]). The rate of grade ≥3 treatment-related adverse events (TRAEs) with Dato-DXd was lower than ICC (20.8% v 44.7%). The most common TRAEs (any grade; grade ≥3) were nausea (51.1%; 1.4%) and stomatitis (50%; 6.4%) with Dato-DXd and neutropenia (grouped term, 42.5%; 30.8%) with ICC. CONCLUSION: Patients receiving Dato-DXd had statistically significant and clinically meaningful improvement in PFS and a favorable and manageable safety profile, compared with ICC. Results support Dato-DXd as a novel treatment option for patients with inoperable/metastatic HR+/HER2‒ breast cancer who have received one to two previous lines of chemotherapy in this setting.

Imlunestrant, an Oral Selective Estrogen Receptor Degrader, as Monotherapy and in Combination With Targeted Therapy in Estrogen Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Advanced Breast Cancer: Phase Ia/Ib EMBER Study.

PURPOSE: Imlunestrant is a next-generation oral selective estrogen receptor (ER) degrader designed to deliver continuous ER target inhibition, including in ESR1-mutant breast cancer. This phase Ia/b trial determined the recommended phase II dose (RP2D), safety, pharmacokinetics, and efficacy of imlunestrant, as monotherapy and in combination with targeted therapy, in ER-positive (ER+) advanced breast cancer (ABC) and endometrial endometrioid cancer. The ER+/human epidermal growth factor receptor 2-negative (HER2-) ABC experience is reported here. METHODS: An i3+3 dose-escalation design was used, followed by dose expansions of imlunestrant as monotherapy or in combination with abemaciclib with or without aromatase inhibitor (AI), everolimus, or alpelisib. Imlunestrant was administered orally once daily and with the combination partner per label. RESULTS: Overall, 262 patients with ER+/HER2- ABC were treated (phase Ia, n = 74; phase Ib, n = 188). Among patients who received imlunestrant monotherapy (n = 114), no dose-limiting toxicities or discontinuations occurred. At the RP2D (400 mg once daily), patients (n = 51) reported grade 1-2 nausea (39.2%), fatigue (39.2%), and diarrhea (29.4%). Patients at RP2D had received previous cyclin-dependent kinase 4/6 inhibitor (CDK4/6i; 92.2%), fulvestrant (41.2%), and chemotherapy (29.4%) for ABC and achieved a median progression-free survival (mPFS) of 7.2 months (95% CI, 3.7 to 8.3). Among patients who received imlunestrant + abemaciclib (n = 42) and imlunestrant + abemaciclib + AI (n = 43), most (69.4%) were treatment-naïve for ABC; all were CDK4/6i-naïve. Patients treated with imlunestrant + everolimus (n = 42)/alpelisib (n = 21) had received previous CDK4/6i (100%), fulvestrant (34.9%), and chemotherapy (17.5%) for ABC. No new safety signals or interactions with partnered drugs were observed. The mPFS was 19.2 months (95% CI, 13.8 to not available) for imlunestrant + abemaciclib and was not reached for imlunestrant + abemaciclib + AI. The mPFS with imlunestrant + everolimus/alpelisib was 15.9 months (95% CI, 11.3 to 19.1)/9.2 months (95% CI, 3.7 to 11.1). Antitumor activity was evident regardless of ESR1 mutation status. CONCLUSION: Imlunestrant, as monotherapy or in combination with targeted therapy, had a manageable safety profile with evidence of preliminary antitumor activity in ER+/HER2- ABC.

Trastuzumab Deruxtecan after Endocrine Therapy in Metastatic Breast Cancer.

BACKGROUND: Outcomes in patients with hormone receptor-positive metastatic breast cancer worsen after one or more lines of endocrine-based therapy. Trastuzumab deruxtecan has shown efficacy in patients with metastatic breast cancer with low expression of human epidermal growth factor receptor 2 (HER2) after previous chemotherapy. METHODS: We conducted a phase 3, multicenter, open-label trial involving patients with hormone receptor-positive metastatic breast cancer with low HER2 expression (a score of 1+ or 2+ on immunohistochemical [IHC] analysis and negative results on in situ hybridization) or ultralow HER2 expression (IHC 0 with membrane staining) who had received one or more lines of endocrine-based therapy and no previous chemotherapy for metastatic breast cancer. Patients were randomly assigned in a 1:1 ratio to receive trastuzumab deruxtecan or the physician's choice of chemotherapy. The primary end point was progression-free survival (according to blinded independent central review) among the patients with HER2-low disease. Secondary end points included progression-free survival among all the patients who had undergone randomization, overall survival, and safety. RESULTS: Of the 866 patients who underwent randomization, 713 had HER2-low disease, and 153 had HER2-ultralow disease. Among the patients with HER2-low disease, the median progression-free survival was 13.2 months (95% confidence interval [CI], 11.4 to 15.2) in the trastuzumab deruxtecan group and 8.1 months (95% CI, 7.0 to 9.0) in the chemotherapy group (hazard ratio for disease progression or death, 0.62; 95% CI, 0.51 to 0.74; P<0.001); the results were consistent in the exploratory HER2-ultralow population. Data for overall survival were immature. Adverse events of grade 3 or higher occurred in 52.8% of the patients in the trastuzumab deruxtecan group and in 44.4% of those in the chemotherapy group. Adjudicated interstitial lung disease or pneumonitis occurred in 49 patients (11.3%; three events were grade 5 in severity) and in 1 patient (0.2%; grade 2), respectively. CONCLUSIONS: Among patients with hormone receptor-positive, HER2-low or HER2-ultralow metastatic breast cancer who had received one or more lines of endocrine-based therapy, treatment with trastuzumab deruxtecan resulted in longer progression-free survival than chemotherapy. No new safety signals were identified. (Funded by AstraZeneca and Daiichi Sankyo; DESTINY-Breast06 ClinicalTrials.gov number, NCT04494425.).

Precision therapeutics and emerging strategies for HR-positive metastatic breast cancer.

Anti-oestrogen-based therapies, often combined with a CDK4/6 inhibitor, are the current standard-of-care first-line therapy for patients with advanced-stage hormone receptor-positive (HR+) breast cancer. Resistance to anti-oestrogen agents inevitably occurs, mediated by oestrogen receptor (ER)-dependent or ER-independent mechanisms that drive tumour progression. Emerging endocrine therapies include, but are not limited to, next-generation oral ER degraders and proteolysis targeting chimeras, which might be particularly effective in patients with ESR1-mutant breast cancer. Furthermore, cancers harbouring driver alterations in oncogenic signalling pathways, including AKT and PI3K, might be susceptible to novel combination strategies involving targeted inhibitors. Next-generation CDK2/4 inhibitors are an area of active clinical investigation, and efforts are ongoing to evaluate the role of sequential CDK inhibition. Approved and emerging antibody-drug conjugates exploiting novel target antigens have also demonstrated promising clinical activity. These novel agents, as well as further identification and characterization of predictive biomarkers, will hopefully continue to improve clinical outcomes, reduce the incidence of toxicities, and limit the extent of overtreatment in this population. In this Review, we describe the evolving treatment paradigm for patients with metastatic HR+ breast cancer in light of the growing armamentarium of drugs and biomarkers that will help to shape the future therapeutic landscape. These strategies are expected to involve tumour molecular profiling to enable the delivery of precision medicine.

Elacestrant in ER+, HER2- Metastatic Breast Cancer with ESR1-Mutated Tumors: Subgroup Analyses from the Phase III EMERALD Trial by Prior Duration of Endocrine Therapy plus CDK4/6 Inhibitor and in Clinical Subgroups.

PURPOSE: Elacestrant significantly prolonged progression-free survival (PFS) with manageable safety versus standard-of-care (SOC) endocrine therapy (ET) in patients with estrogen receptor-positive (ER+), HER2- metastatic breast cancer and tumors harboring estrogen receptor 1 (ESR1) mutation following ET plus a cyclin-dependent kinase 4/6 inhibitor (ET+CDK4/6i). In patients with ESR1-mutated tumors, we evaluated the efficacy and safety of elacestrant versus SOC based on prior ET+CDK4/6i duration and in clinical subgroups with prior ET+CDK4/6i ≥12 months. PATIENTS AND METHODS: EMERALD, an open-label phase III trial, randomly assigned patients with ER+, HER2- metastatic breast cancer who had received 1-2 prior lines of ET, mandatory CDK4/6i, and ≤1 chemotherapy to elacestrant (345 mg daily) or SOC (aromatase inhibitor or fulvestrant). PFS was assessed across subgroups in post hoc exploratory analyses without adjustment for multiple testing. RESULTS: In patients with ESR1-mutated tumors and prior ET+CDK4/6i ≥12 months, the median PFS for elacestrant versus SOC was 8.6 versus 1.9 months (HR, 0.41; 95% confidence interval, 0.26-0.63). In this population, the median PFS (in months) for elacestrant versus SOC was 9.1 versus 1.9 (bone metastases), 7.3 versus 1.9 (liver and/or lung metastases), 9.0 versus 1.9 (<3 metastatic sites), 10.8 versus 1.8 (≥3 metastatic sites), 5.5 versus 1.9 (PIK3 catalytic subunit α mutation), 8.6 versus 1.9 (tumor protein p53 gene mutation), 9.0 versus 1.9 (HER2-low), 9.0 versus 1.9 (ESR1D538G-mutated tumors), and 9.0 versus 1.9 (ESR1Y537S/N-mutated tumors). Subgroup safety was consistent with the overall population. CONCLUSIONS: The duration of prior ET+CDK4/6i ≥12 months in metastatic breast cancer was associated with a clinically meaningful improvement in PFS for elacestrant compared with SOC and was consistent across all subgroups evaluated in patients with ER+, HER2-, ESR1-mutated tumors.

Randomized Phase III Study of Amcenestrant Plus Palbociclib Versus Letrozole Plus Palbociclib in Estrogen Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Advanced Breast Cancer: Primary Results From AMEERA-5.

PURPOSE: AMEERA-5 investigated amcenestrant (oral selective estrogen receptor [ER] degrader) plus palbociclib versus letrozole plus palbociclib as first-line treatment for ER-positive/human epidermal growth factor receptor 2-negative (ER+/HER2-) advanced/metastatic breast cancer (aBC). MATERIALS AND METHODS: In AMEERA-5 (ClinicalTrials.gov identifier: NCT04478266), a double-blind, double-dummy, international phase III trial, adult pre-/post-menopausal women and men without previous systemic therapy for ER+/HER2- aBC were randomly assigned 1:1 to amcenestrant 200 mg once daily + standard palbociclib dosage (125 mg once daily, 21 days on/7 days off) or letrozole 2.5 mg once daily + standard palbociclib dosage, stratified by de novo metastatic disease, postmenopausal women, and visceral metastasis. The primary end point was progression-free survival (PFS), compared using a stratified log-rank test with one-sided type I error rate of 2.5%. Secondary end points included overall survival (key secondary), pharmacokinetics, and safety. RESULTS: Between October 14, 2020, and December 2, 2021, 1,068 patients were randomly assigned to amcenestrant + palbociclib (N = 534) or letrozole + palbociclib (N = 534). At the interim analysis (median follow-up 8.4 months), the stratified hazard ratio for PFS was 1.209 (95% CI, 0.939 to 1.557; one-sided P value = .9304); therefore, the study was stopped for futility. The 6-month PFS rate was 82.7% (95% CI, 79.0 to 85.8) with amcenestrant + palbociclib versus 86.9% (95% CI, 83.5 to 89.6) with letrozole + palbociclib. In the amcenestrant + palbociclib versus letrozole + palbociclib groups, treatment-emergent adverse events (any grade) occurred in 85.6% versus 85.4% of patients and grade ≥3 events in 46.3% versus 60.8%, respectively. CONCLUSION: The AMEERA-5 study was discontinued on the basis of the recommendation of the data monitoring committee at the interim futility analysis. No new safety signals were identified.

Mechanisms of sensitivity and resistance to CDK4/CDK6 inhibitors in hormone receptor-positive breast cancer treatment.

Cell cycle dysregulation is a hallmark of cancer that promotes eccessive cell division. Cyclin-dependent kinase 4 (CDK4) and cyclin-dependent kinase 6 (CDK6) are key molecules in the G1-to-S phase cell cycle transition and are crucial for the onset, survival, and progression of breast cancer (BC). Small-molecule CDK4/CDK6 inhibitors (CDK4/6i) block phosphorylation of tumor suppressor Rb and thus restrain susceptible BC cells in G1 phase. Three CDK4/6i are approved for the first-line treatment of patients with advanced/metastatic hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) BC in combination with endocrine therapy (ET). Though this has improved the clinical outcomes for survival of BC patients, there is no established standard next-line treatment to tackle drug resistance. Recent studies suggest that CDK4/6i can modulate other distinct effects in both BC and breast stromal compartments, which may provide new insights into aspects of their clinical activity. This review describes the biochemistry of the CDK4/6-Rb-E2F pathway in HR+ BC, then discusses how CDK4/6i can trigger other effects in BC/breast stromal compartments, and finally outlines the mechanisms of CDK4/6i resistance that have emerged in recent preclinical studies and clinical cohorts, emphasizing the impact of these findings on novel therapeutic opportunities in BC.

CDK4/6 Inhibitor Efficacy in ESR1-Mutant Metastatic Breast Cancer.

BACKGROUND: In estrogen receptor-positive metastatic breast cancer, ESR1 mutations (ESR1m) are a common mechanism of acquired resistance to aromatase inhibitors (ArIh). However, the impact ESR1 alterations have on CDK4/6 inhibitor (CDK4/6i) sensitivity has not been established. Analyses of CDK4/6i trials suggest that the endocrine therapy partner and specific ESR1 allele may affect susceptibility. We analyzed a real-world data set to investigate CDK4/6i efficacy in ESR1m metastatic breast cancer and associated clinical factors. METHODS: ESR1m were identified by analysis of circulating-tumor deoxyribonucleic acid. The GuardantINFORM database contains genomic information from tumors linked with claims data. Patients who started a CDK4/6i within 30 days of sequencing were categorized as having ESR1m or non-ESR1-mutant (non-ESR1m) breast cancer. Data were analyzed to determine the real-world time-to-next-treatment, defined as the start of a breast cancer treatment to initiation of the subsequent treatment. RESULTS: One hundred forty-five patients with ESR1m and 612 with non-ESR1m metastatic breast cancer were analyzed. ESR1m and non-ESR1m tumors had similar real-world time-to-next-treatment on CDK4/6i regimens (hazard ratio, 1.02; 95% confidence interval, 0.82 to 1.23). Duration on therapy in the first-line and second-line plus treatment settings were comparable regardless of ESR1 status. We stratified treatment duration by concurrent endocrine therapy, and patients with ESR1m had worse outcomes on ArIh but comparable real-world time-to-next-treatment on fulvestrant. CONCLUSIONS: These data suggest ESR1 variants are not associated with pan-CDK4/6i resistance and are consistent with the hypothesis that CDK4/6 blockade combined with a selective estrogen receptor degrader is potentially an effective option for ESR1m metastatic breast cancer.

Trastuzumab deruxtecan in patients with solid tumours harbouring specific activating HER2 mutations (DESTINY-PanTumor01): an international, phase 2 study.

BACKGROUND: Trastuzumab deruxtecan is a HER2-directed antibody-drug conjugate approved by the US Food and Drug Administration and the European Medicines Agency for HER2-mutant non-small-cell lung cancer. Few treatment options exist for patients with HER2-mutant solid tumours beyond lung cancers. We investigated trastuzumab deruxtecan in metastatic solid tumours with specific activating HER2 mutations. METHODS: In this open-label, phase 2, basket study done in 29 centres in Asia, Europe, and North America, we investigated trastuzumab deruxtecan (5·4 mg/kg every 3 weeks by intravenous infusion) in patients aged 18 years or older with unresectable or metastatic solid tumours with specific activating HER2 mutations, an Eastern Cooperative Oncology Group performance status of 0 or 1, and disease progression following previous treatment (previous HER2-targeted therapy was permitted) or with no satisfactory alternative treatment options. The primary endpoint was confirmed objective response rate by independent central review. Anti-tumour activity and safety were analysed in all patients who received at least one dose of trastuzumab deruxtecan. This trial is registered with ClinicalTrials.gov, NCT04639219, and is active but no longer recruiting. FINDINGS: Between Dec 30, 2020, and Jan 25, 2023, 102 patients (62 [61%] female and 40 [39%] male; median age 66·5 years [IQR 58-72]; 51 [50%] White, two [2%] Black or African American, 38 [37%] Asian, and 11 [11%] did not have race information reported) with solid tumours with activating HER2 mutations received trastuzumab deruxtecan and were included in the anti-tumour activity and safety analyses sets. Patients had a median of three (IQR 2-4) previous treatment regimens. The median duration of follow-up was 8·61 months (IQR 3·71-12·68). The objective response rate by independent central review was 29·4% (95% CI 20·8-39·3; 30 of 102 patients). 52 (51%) patients had a treatment-emergent adverse event of grade 3 or worse; the most common events (in ≥5% of patients) were anaemia (16 [16%]) and neutrophil count decreased (eight [8%]). Drug-related treatment-emergent serious adverse events occurred in ten (10%) patients. Adjudicated drug-related interstitial lung disease or pneumonitis of any grade occurred in 11 patients (11%; three grade 1, five grade 2, one grade 3, and two grade 5); there were two (2%) cases of fatal adjudicated drug-related interstitial lung disease or pneumonitis. INTERPRETATION: Trastuzumab deruxtecan showed anti-tumour activity and durable responses in heavily pretreated patients across multiple tumour types with activating HER2 mutations, with no new safety signals. Prespecified HER2 mutations might be targeted by HER2-directed antibody-drug conjugates and our findings support further investigation of trastuzumab deruxtecan in the pan-tumour setting. FUNDING: AstraZeneca and Daiichi Sankyo.

Antibody-Drug Conjugate Sacituzumab Govitecan Enables a Sequential TOP1/PARP Inhibitor Therapy Strategy in Patients with Breast Cancer.

PURPOSE: The antibody-drug conjugate (ADC) sacituzumab govitecan (SG) comprises the topoisomerase 1 (TOP1) inhibitor (TOP1i) SN-38, coupled to a monoclonal antibody targeting trophoblast cell surface antigen 2 (TROP-2). Poly(ADP-ribose) polymerase (PARP) inhibition may synergize with TOP1i and SG, but previous studies combining systemic PARP and TOP1 inhibitors failed due to dose-limiting myelosuppression. Here, we assess the proof-of-mechanism and clinical feasibility for SG and talazoparib (TZP) employing an innovative sequential dosing schedule. PATIENTS AND METHODS: In vitro models tested pharmacodynamic endpoints, and in a phase 1b clinical trial (NCT04039230), 30 patients with metastatic triple-negative breast cancer (mTNBC) received SG and TZP in a concurrent (N = 7) or sequential (N = 23) schedule. Outcome measures included safety, tolerability, preliminary efficacy, and establishment of a recommended phase 2 dose. RESULTS: We hypothesized that tumor-selective delivery of TOP1i via SG would reduce nontumor toxicity and create a temporal window, enabling sequential dosing of SG and PARP inhibition. In vitro, sequential SG followed by TZP delayed TOP1 cleavage complex clearance, increased DNA damage, and promoted apoptosis. In the clinical trial, sequential SG/TZP successfully met primary objectives and demonstrated median progression-free survival (PFS) of 7.6 months without dose-limiting toxicities (DLT), while concurrent dosing yielded 2.3 months PFS and multiple DLTs including severe myelosuppression. CONCLUSIONS: While SG dosed concurrently with TZP is not tolerated clinically due to an insufficient therapeutic window, sequential dosing of SG followed by TZP proved a viable strategy. These findings support further clinical development of the combination and suggest that ADC-based therapy may facilitate novel, mechanism-based dosing strategies.

Health-related quality of life with sacituzumab govitecan in HR+/HER2- metastatic breast cancer in the phase III TROPiCS-02 trial.

BACKGROUND: The TROPiCS-02 study (NCT03901339) demonstrated that sacituzumab govitecan (SG) has superior clinical outcomes over treatment of physician's choice (TPC) chemotherapy in patients with hormone receptor-positive, human epidermal growth factor 2 receptor-negative (HR+/HER2-) metastatic breast cancer (mBC). Here, we present health-related quality of life (HRQoL) patient-reported outcome (PRO) findings from this study. PATIENTS AND METHODS: Eligible adults with HR+/HER2- mBC who previously received a taxane, endocrine-based therapy, a CDK4/6 inhibitor, and 2-4 lines of chemotherapy were randomized 1:1 to receive SG or TPC until progression or unacceptable toxicity. PROs were assessed at baseline and on day 1 of each cycle, using the European Organization for Research and Treatment of Cancer Quality-of-Life Core 30 (EORTC QLQ-C30), EQ-5D-5L, and PRO Common Terminology Criteria for Adverse Events (PRO-CTCAE). RESULTS: Compared to TPC, overall least square mean change from baseline was significantly better for SG for physical functioning and dyspnea, but worse for diarrhea. Time to first clinically meaningful worsening or death was significantly longer for SG in global health status/quality of life, physical functioning, fatigue, emotional functioning, dyspnea, insomnia, and financial difficulties of the EORTC QLQ-C30 and the EQ-VAS, but longer for TPC in diarrhea. Few patients in both arms reported experiencing any worsening to level 3 or 4 treatment-related symptomatic events during treatment, as assessed by 16 PRO-CTCAE items, except for diarrhea frequency and amount of hair loss, which favored TPC. CONCLUSIONS: SG was associated with an HRQoL benefit in most symptoms and functioning, compared with TPC. This supports the favorable profile of SG as a treatment option for patients with pretreated HR+/HER2- mBC.

Subgroup analyses from the phase 3 ASCENT study of sacituzumab govitecan in metastatic triple-negative breast cancer.

In this post hoc analysis of the ASCENT study, we compared outcomes with sacituzumab govitecan (SG) vs single-agent chemotherapy in clinically important subgroups of patients with metastatic triple-negative breast cancer (mTNBC). Patients with mTNBC refractory to/relapsing after ≥2 prior chemotherapies (≥1 in the metastatic setting) were randomized 1:1 to receive SG or treatment of physician's choice (TPC) until unacceptable toxicity/progression. The primary endpoint was progression-free survival (PFS) per RECIST 1.1 by central review in patients without brain metastases. Patients with brain metastases were allowed if metastases were stable ≥4 weeks. In the intention-to-treat (ITT) population, 19% of patients were age ≥65 years; 12% were Black, and 12% had brain metastases. SG improved PFS and overall survival (OS), respectively, vs TPC in patients age ≥65 years (7.1 vs 2.4 months and 14.7 vs 8.9 months), or of Black race (5.4 vs 2.2 months and 13.8 vs 8.5 months), consistent with outcomes in the ITT population. Patients with brain metastases had numerically higher median PFS with SG vs TPC, but median OS was similar between treatment groups. SG was well tolerated and had a manageable safety profile consistent with the full safety population across all subgroups; neutropenia and diarrhea were the most common treatment-emergent adverse events. These findings confirm the meaningful clinical benefit of SG vs standard chemotherapy in patient subgroups with high unmet needs. SG should be considered an effective and safe treatment option for patients with mTNBC eligible for second-line or later therapy. ClinicalTrials.gov Number: NCT02574455.

Tumor cell-based liquid biopsy using high-throughput microfluidic enrichment of entire leukapheresis product.

Circulating Tumor Cells (CTCs), interrogated by sampling blood from patients with cancer, contain multiple analytes, including intact RNA, high molecular weight DNA, proteins, and metabolic markers. However, the clinical utility of tumor cell-based liquid biopsy has been limited since CTCs are very rare, and current technologies cannot process the blood volumes required to isolate a sufficient number of tumor cells for in-depth assays. We previously described a high-throughput microfluidic prototype utilizing high-flow channels and amplification of cell sorting forces through magnetic lenses. Here, we apply this technology to analyze patient-derived leukapheresis products, interrogating a mean blood volume of 5.83 liters from patients with metastatic cancer, with a median of 2,799 CTCs purified per patient. Isolation of many CTCs from individual patients enables characterization of their morphological and molecular heterogeneity, including cell and nuclear size and RNA expression. It also allows robust detection of gene copy number variation, a definitive cancer marker with potential diagnostic applications. High-volume microfluidic enrichment of CTCs constitutes a new dimension in liquid biopsies.

Novel oral selective estrogen receptor degraders (SERDs) to target hormone receptor positive breast cancer: elacestrant as the poster-child.

INTRODUCTION: Estrogen receptor positive (ER+) breast cancer is the most common breast cancer subtype, and therapeutic management relies primarily on inhibiting ER signaling. In the metastatic setting, ER signaling is typically targeted by selective estrogen receptor degraders (SERDs) or aromatase inhibitors (AIs), the latter of which prevent estrogen production. Activating ESR1 mutations are among the most common emergent breast cancer mutations and confer resistance to AIs. AREAS COVERED: Until 2023, fulvestrant was the only approved SERD; fulvestrant is administered intramuscularly, and in some cases may also have limited efficacy in the setting of certain ESR1 mutations. In 2023, the first oral SERD, elacestrant, was approved for use in ESR1-mutated, ER+/HER2- advanced breast cancer and represents a new class of therapeutic options. While the initial approval was as monotherapy, ongoing studies are evaluating elacestrant (as well as other oral SERDs) in combination with other therapies including CDK4/6 inhibitors and PI3K inhibitors, which parallels the current combination uses of fulvestrant. EXPERT OPINION: Elacestrant's recent approval sheds light on the use of biomarkers such as ESR1 to gauge a tumor's endocrine sensitivity. Ongoing therapeutic and correlative biomarker studies will offer new insight and expanding treatment options for patients with advanced breast cancer.

Datopotamab Deruxtecan in Advanced or Metastatic HR+/HER2- and Triple-Negative Breast Cancer: Results From the Phase I TROPION-PanTumor01 Study.

PURPOSE: Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate consisting of a humanized antitrophoblast cell-surface antigen 2 (TROP2) monoclonal antibody linked to a potent, exatecan-derived topoisomerase I inhibitor payload via a plasma-stable, selectively cleavable linker. PATIENTS AND METHODS: TROPION-PanTumor01 (ClinicalTrials.gov identifier: NCT03401385) is a phase I, dose-escalation, and dose-expansion study evaluating Dato-DXd in patients with previously treated solid tumors. The primary study objective was to assess the safety and tolerability of Dato-DXd. Secondary objectives included evaluation of antitumor activity and pharmacokinetics. Results from patients with advanced/metastatic hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer (BC) or triple-negative BC (TNBC) are reported. RESULTS: At data cutoff (July 22, 2022), 85 patients (HR+/HER2- BC = 41, and TNBC = 44) had received Dato-DXd. The objective response rate by blinded independent central review was 26.8% (95% CI, 14.2 to 42.9) and 31.8% (95% CI, 18.6 to 47.6) for patients with HR+/HER2- BC and TNBC, respectively. The median duration of response was not evaluable in the HR+/HER2- BC cohort and 16.8 months in the TNBC cohort. The median progression-free survival in patients with HR+/HER2- BC and TNBC was 8.3 and 4.4 months, respectively. All-cause treatment-emergent adverse events (TEAEs; any grade, grade ≥3) were observed in 100% and 41.5% of patients with HR+/HER2- BC and 100% and 52.3% of patients with TNBC. Stomatitis was the most common TEAE (any grade, grade ≥3) in both HR+/HER2- BC (82.9%, 9.8%) and TNBC (72.7%, 11.4%) cohorts. CONCLUSION: In patients with heavily pretreated advanced HR+/HER2- BC and TNBC, Dato-DXd demonstrated promising clinical activity and a manageable safety profile. Dato-DXd is currently being evaluated in phase III studies.

Genomic spectrum of actionable alterations in serial cell free DNA (cfDNA) analysis of patients with metastatic breast cancer.

We aimed to study the incidence and genomic spectrum of actionable alterations (AA) detected in serial cfDNA collections from patients with metastatic breast cancer (MBC). Patients with MBC who underwent plasma-based cfDNA testing (Guardant360®) between 2015 and 2021 at an academic institution were included. For patients with serial draws, new pathogenic alterations in each draw were classified as actionable alterations (AA) if they met ESCAT I or II criteria of the ESMO Scale for Clinical Actionability of Molecular Targets (ESCAT). A total of 344 patients with hormone receptor-positive (HR+)/HER2-negative (HER2-) MBC, 95 patients with triple-negative (TN) MBC and 42 patients with HER2-positive (HER2 + ) MBC had a baseline (BL) cfDNA draw. Of these, 139 HR+/HER2-, 33 TN and 13 HER2+ patients underwent subsequent cfDNA draws. In the HR+/HER2- cohort, the proportion of patients with new AA decreased from 63% at BL to 27-33% in the 2nd-4th draws (p < 0.0001). While some of the new AA in subsequent draws from patients with HR+/HER2- MBC were new actionable variants in the same genes that were known to be altered in previous draws, 10-24% of patients had new AA in previously unaltered genes. The incidence of new AA also decreased with subsequent draws in the TN and HER2+ cohorts (TN: 25% to 0-9%, HER2 + : 38% to 14-15%). While the incidence of new AA in serial cfDNA decreased with subsequent draws across all MBC subtypes, new alterations with a potential impact on treatment selection continued to emerge, particularly for patients with HR+/HER2- MBC.

TROPION-Breast03: a randomized phase III global trial of datopotamab deruxtecan ± durvalumab in patients with triple-negative breast cancer and residual invasive disease at surgical resection after neoadjuvant therapy.

Background: Despite advances in the treatment of early triple-negative breast cancer (TNBC), patients with residual invasive disease after neoadjuvant therapy have a high risk of disease recurrence and worse survival outcomes than those who have pathological complete response (pCR). Improving outcomes in early TNBC remains an unmet need requiring new adjuvant treatment approaches. Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate comprising a humanized anti-trophoblast cell-surface antigen 2 immunoglobulin G1 (IgG1) monoclonal antibody attached via a plasma-stable, cleavable linker to a potent topoisomerase I inhibitor payload, with activity observed in advanced TNBC. Objectives: TROPION-Breast03 is an ongoing phase III study evaluating the efficacy and safety of Dato-DXd alone or combined with durvalumab versus standard-of-care therapy as adjuvant treatment in patients with stage I-III TNBC with residual invasive disease at surgical resection following neoadjuvant treatment. Methods and design: Eligible patients, aged ⩾18 years, will be randomized in a 2:1:2 ratio to receive Dato-DXd [6 mg/kg intravenously (IV) every 3 weeks (Q3W); eight cycles] and durvalumab (1120 mg IV Q3W; nine cycles), Dato-DXd monotherapy (6 mg/kg IV Q3W), or investigator's choice of therapy (ICT; capecitabine, pembrolizumab, or capecitabine and pembrolizumab). The primary endpoint is invasive disease-free survival (iDFS) for Dato-DXd and durvalumab versus ICT. Key secondary endpoints include safety, distant disease-free survival, and overall survival for Dato-DXd and durvalumab versus ICT and iDFS for Dato-DXd monotherapy versus ICT. Ethics: TROPION-Breast03 will be approved by the independent ethics committees or institutional review boards at each study site. All study participants will provide written informed consent. Discussion: TROPION-Breast03 will help define the potential role of Dato-DXd in the treatment of patients with early-stage TNBC who do not have pCR after neoadjuvant therapy. Trial registration: ClinicalTrials.gov identifier: NCT05629585 (registration date: 29 November 2022).

TROPION-Breast03: a clinical trial designed to assess the effectiveness and safety of Dato-DXd, alone or in combination with durvalumab, in patients with triple-negative breast cancer who have cancer cells remaining at the time of surgery after initial systemic therapy Triple-negative breast cancer (TNBC), in which cells do not have estrogen or progesterone receptors or high levels of human epidermal growth factor receptor 2, is the most aggressive breast cancer subtype. TNBC is difficult to treat and associated with high risk of recurrence despite standard systemic therapy (treatment targeting the entire body), which can include chemotherapy alone or in combination with immunotherapy (treatment targeting the immune system). To reduce the risk of recurrence, standard systemic treatment is often followed by surgical removal of the patient's tumors and additional systemic treatment. Dato-DXd is an antibody-drug conjugate, which is an anticancer drug (DXd) connected to an antibody (datopotamab) by a stable linker. Datopotamab binds to TROP2, a protein found on breast cancer cells, and is taken into the tumor cell where the linker breaks, releasing DXd to kill the cell. By delivering DXd directly to cancer cells, Dato-DXd reduces exposure in the rest of the body, reducing the risk of side effects. Since Dato-DXd can recruit immune cells to cancer sites, it may work better combined with durvalumab, a drug that blocks the activity of a protein called PD-L1, making cancer cells more susceptible to being killed by immune cells. The TROPION-Breast03 study will compare Dato-DXd, alone or combined with durvalumab, with standard-of-care therapy in patients with TNBC that has not spread to parts of the body away from the original tumor site(s), but with cancer cells remaining at the time of surgery after initial systemic therapy. It will assess how well each treatment works and describe any side effects. We plan to recruit 1,075 eligible adults who will be randomly assigned in a 2:1:2 ratio to: • Dato-DXd + durvalumab • Dato-DXd alone • Standard-of-care therapy • Patients will receive treatment until they complete the planned course of therapy (8 or 9 cycles), their cancer returns, side effects become unacceptable, or they choose to stop.