HER2 Therapy Research Articles

Abstract A039: Carnitine palmitoyltransferase IA: an emerging potential metabolic target to counteract HER2-targeted therapy resistance in HER2-positive breast cancer

Abstract HER2 overexpression/amplification (HER2+) occurs in 15-20% of breast cancer (BC) and identifies a clinically aggressive BC subtype. Although the introduction of effective anti-HER2 drugs remarkably improved the prognosis of HER2+ BC patients, primary and acquired tumor resistance to anti-HER2 treatments underscores the need for novel therapies for HER2+ BC patients. Tumor cells exhibit unique metabolic alterations that are responsible for primary or acquired tumor resistance to standard therapies, and which are increasingly emerging as potential targets for novel treatment strategies. In particular, the dysregulation of fatty acid β-oxidation (FAO), a catabolic process that produces energy (ATP and NADPH production) to sustain cancer growth, survival and aggressiveness, is associated with therapy resistance in diverse malignancies including BC. Specifically, carnitine palmitoyltransferase 1A (CPT1A), the key rate-limiting enzyme of mitochondrial FAO, facilitates cancer metabolic adaptation, thus representing a promising target for cancer therapy. In this context, gene set enrichment analysis of profiled matched HER2+ BC samples (n=33) collected before and after trastuzumab-based neo-adjuvant biochemotherapy (trastuzumab plus taxanes) revealed that the Fatty Acids (FA) metabolism gene set was one of the most significantly Hallmark enriched pathway (NES=1.57; FDR=0.0039) in post- compared with pre-treated HER2+ BC samples, implying that trastuzumab plus chemotherapy treatment induces an enhancement of FAO activity. Accordingly, CPT1A transcript levels were found to be inversely associated with lapatinib (L) susceptibility in HER2+ BC cell lines and patient-derived organoids resistant to anti-HER2 therapy versus L-sensitive cell models. Additionally, Seahorse Analysis revealed higher baseline oxidation of the FA palmitate in intrinsically L-resistant HER2+ BC cells as compared with L-sensitive cells, thus supporting the hypothesis that FAO could represent the major lipid metabolic pathway sustaining the energetic needs of HER2+ BC cells resistant to anti-HER2 therapy for survival and growth. Further, the pharmacological dual blockade of HER2 and CPT1A significantly increases cytotoxicity of L-resistant cell models versus single agents, corroborating the candidacy of CPT1A as a potential metabolic vulnerability to be targeted to overcome refractoriness to HER2-targeted therapy in HER2+ BC. Our data support the hypothesis that the inhibition of FAO sensitizes HER2+ BC cells to anti-HER2 drugs, thus representing a potential strategy to overcome drug resistance in HER2+ BC and paving the way to investigate CPT1A inhibitors with anti-HER2 drugs to improve the clinical outcomes of HER2+ BC patients with acquired resistance to standard anti-HER2 therapies. Citation Format: Alma Franceschini, Lorenzo T Castagnoli, Tiziana IINDT Triulzi, Paola Antonia Corsetto, Matteo Dugo, Antonino Belfiore, Andrea Vingiani, Lorena Signati, Serena Mazzucchelli, Fabio Corsi, Francesca Ligorio, Elda Tagliabue, Claudio Vernieri, Serenella M. Pupa. Carnitine palmitoyltransferase IA: an emerging potential metabolic target to counteract HER2-targeted therapy resistance in HER2-positive breast cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A039.

Protein signaling and drug target activation signatures to guide therapy prioritization: Therapeutic resistance and sensitivity in the I-SPY 2 Trial

Molecular subtyping of breast cancer is based mostly on HR/HER2 and gene expression-based immune, DNA repair deficiency, and luminal signatures. We extend this description via functional protein pathway activation mapping using pre-treatment, quantitative expression data from 139 proteins/phosphoproteins from 736 patients across 8 treatment arms of the I-SPY 2 Trial (ClinicalTrials.gov: NCT01042379). We identify predictive fit-for-purpose, mechanism-of-action-based signatures and individual predictive protein biomarker candidates by evaluating associations with pathologic complete response. Elevated levels of cyclin D1, estrogen receptor alpha, and androgen receptor S650 associate with non-response and are biomarkers for global resistance. We uncover protein/phosphoprotein-based signatures that can be utilized both for molecularly rationalized therapeutic selection and for response prediction. We introduce a dichotomous HER2 activation response predictive signature for stratifying triple-negative breast cancer patients to either HER2 or immune checkpoint therapy response as a model for how protein activation signatures provide a different lens to view the molecular landscape of breast cancer and synergize with transcriptomic-defined signatures.

The impact of metastatic breast cancer (mBC) treatment on patient reported productivity loss among patients with HER2+ mBC in the U.S.

352 Background: Little is known about the impact of treatments and other factors on productivity loss among HER2+ mBC patients. This study aimed to assess the work productivity and activity impairment among employed women with HER2+ mBC. Methods: A cross-sectional survey was completed by the members of two patient advocacy organizations in the U.S. Those who were employed for paid work (≥20 hours/week) and receiving systemic treatments for HER2+ mBC for the past 3-months were recruited. Participants self-reported their sociodemographic, clinical and treatment history, time burden related to disease management, and completed the work productivity and activity impairment (WPAI) and Functional Assessment of Cancer Therapy Breast (FACT-B) quality of life (QoL) questionnaires. Patients were grouped based on their current regimen: (1) Oral only, (2) one parenteral drug (1 IV), (3) 2 IVs, (4) 3+ IVs. Association between WPAI scores and sociodemographic and clinical characteristics was assessed using simple linear regression. Results: A total of 118 HER2+ mBC patients participated [mean (SD) age 47.2 (9.5) years, 69.5% were employed full-time and 30.5% part-time, 89% were White, 13.6% resided in rural area]. Among 118 patients, 38 (32.2%) were on 1 IV, 38 (32.2%) on 2 IVs, 31 (26.6%) on 3+ IVs and 11 (9.3%) on oral only regimen. The median travel time (4 hrs vs. 6 hrs) and time spent at healthcare visits (7.3 hrs vs.13.4 hrs) was numerically higher among those on 3+ IVs than those on 1 IV. The median percent work time missed (7.7% vs. 5.8%), overall work impairment (38.2% vs.31.3%) and activity impairment (40.0% vs. 30.0%) in the past 7 days was numerically higher in patients on 3+ IVs than on 1 IV. Working part-time, residing in rural area, having low household income (<25K vs. >75K) and non-commercial insurance was associated with greater overall work impairment (all p-values <0.05). Longer time since mBC diagnosis, longer time on treatment and higher QoL score were associated with lower overall work impairment (all p-values <0.05). Working part-time, low household income, non-commercial insurance, longer time on treatment and higher QoL score were similarly associated with activity impairment (all p-values <005). Conclusions: Socioeconomic and geographical factors were important determinants of work productivity loss among HER2+ mBC patients. IV treatment is the mainstay of therapy for HER2+ mBC patients and being on a simpler regimen for a longer time is likely to reduce work productivity loss and activity impairment. Improving access to novel monotherapy infusion treatment in rural community oncology practices may offer an opportunity to reduce patient time burden and work productivity loss among HER2+ mBC patients and improve health-related quality of life. Additional research from a larger diverse sample is warranted to further understand health disparities in HER2+ mBC patients.

Correlation of High-Sensitivity Cardiac Troponin I Values and Cardiac Radiation Doses in Patients with Left-Sided Breast Cancer Undergoing Hypofractionated Adjuvant Radiotherapy with Concurrent Anti-HER2 Therapy.

Anti HER2 therapy and left breast adjuvant radiation therapy (RT) can both result in cardiotoxicity. The aim of this study was to evaluate the influence of radiation dose on cardiac structures on the values of the early cardiotoxicity marker high-sensitivity cardiac troponin I (hscTnI) in patients with HER2-positive left breast cancer undergoing adjuvant concomitant antiHER2 therapy and radiotherapy, and to establish a correlation between the hscTnI values and cardiac radiation doses. Sixty-one patients underwent left breast hypofractionated radiotherapy in parallel with anti-HER2 therapy: trastuzumab, combined trastuzumab-pertuzumab or trastuzumab emtansine (T-DM1). The hscTnI values were measured prior to and upon completion of radiotherapy. A significant increase in hscTnI was defined as >30% from baseline, with the second value being 4 ng/L or higher. Dose volume histograms (DVH) were generated for the heart, left ventricle (LV) and left anterior descending artery (LAD). The hscTnI levels were corelated with radiation doses on cardiac structures. An increase in hscTnI values was observed in 17 patients (Group 1). These patients had significantly higher mean radiation doses for the heart (p = 0.02), LV (p = 0.03) and LAD (p = 0.04), and AUC for heart and LV (p = 0.01), than patients without hscTnI increase (Group 2). The patients in Group 1 also had larger volumes of heart and LV receiving 2 Gy (p = 0.01 for both) and 4 Gy (p = 0.02 for both). LAD differences were observed in volumes receiving 2 Gy (p = 0.03), 4 Gy (p = 0.02) and 5 Gy (p = 0.02). The increase in hscTnI observed in patients receiving anti-HER2 therapy after adjuvant RT was positively associated with radiation doses on the heart, LV and LAD.

169P Integration of metabolomics and transcriptomics to reveal potential biomarkers associated with treatment response of neoadjuvant therapy in HER2+ breast cancer

169P Integration of metabolomics and transcriptomics to reveal potential biomarkers associated with treatment response of neoadjuvant therapy in HER2+ breast cancer

Deep (phospho)proteomics profiling of pre- treatment needle biopsies identifies signatures of treatment resistance in HER2+ breast cancer

Patients with early-stage HER2-overexpressing breast cancer struggle with treatment resistance in 20%-40% of cases. More information is needed to predict HER2 therapy response and resistance invivo. In this study, we perform (phospho)proteomics analysis of pre-treatment HER2+ needle biopsies of early-stage invasive breast cancer to identify molecular signatures predictive of treatment response to trastuzumab, pertuzumab, and chemotherapy. Our data show that accurate quantification of the estrogen receptor (ER) and HER2 biomarkers, combined with the assessment of associated biological features, has the potential to enable better treatment outcome prediction. In addition, we identify cellular mechanisms that potentially precondition tumors to resist therapy. We find proteins with expression changes that correlate with resistance and constitute to a strong predictive signature for treatment success in our patient cohort. Our results highlight the multifactorial nature of drug resistance invivo and demonstrate the necessity of deep tumor profiling.

Association of Left Anterior Descending Coronary Artery Calcium Progression and Radiation Dose with Major Adverse Cardiac Events in Breast Cancer

Coronary artery calcium (CAC) is associated with increased risk of major adverse cardiac events (MACE). Accelerated CAC progression has been observed in patients with breast cancer after radiotherapy (RT) and there is a relationship between left anterior descending (LAD) coronary artery RT dose and the risk of coronary events. However, there is lack of consensus on LAD dose constraints for breast RT and limited data on the extent and impact of CAC progression. Our objective was to evaluate the association of LAD dose exposure and CAC progression with the risk of MACE in patients with breast cancer following RT. Retrospective analysis of 181 patients with breast cancer treated with RT between 2008 and 2019. CAC was manually measured on RT planning and follow-up CTs (with at least one-year interval) using the Agatston method. Coronary arteries were segmented using a deep learning-based automated algorithm and dosimetric parameters collected. MACE cumulative incidence was estimated, and Fine and Gray regressions performed, accounting for non-cardiac death as a competing risk. The median follow-up following RT was 70 months (interquartile range [IQR], 53-86). The median age was 63 years (IQR, 53-72), 43% had hypertension, 40% hyperlipidemia, 8% coronary heart disease (CHD). Most had pathologic stage I-II disease (76%). RT was targeted to breast/chest wall only in 60% and included regional nodes in 40% (internal mammary chain in 4%). The most common dose/fractionation was 48-50.4 Gy/25-28 fractions (67%) and 42.6-42.7 Gy/16 fractions (30%). At the time of RT, 68 (38%) had at least moderate CAC burden (CAC >100; statin-therapy indicated), but only 29 (43%) were on statin therapy. At a median interval of 44 months (IQR, 26-63), 55% (n = 84) had CAC progression, with a median increase of 52%/year (IQR, 18-193). The median time to MACE was 68 months (IQR, 53-85), with a 5-year cumulative incidence of 7.3% (15 MACE overall). Accounting for age and CHD, there was an increased risk of MACE with LAD CAC progression (subdistribution hazard ratio [SHR] 1.02/10 CAC points; 95% confidence interval [CI] 1.01 = 1.03; p = .007) and the volume of LAD receiving 15 Gy (LAD V15 Gy; SHR 1.03/%; 95% CI, 1.01-1.06; p = .004). There was no association between mean heart dose, chemotherapy, or Her2 therapy exposure and MACE (p>.05). LAD CAC progression and LAD V15 Gy dose exposure were associated with an increased risk of MACE following RT. Accelerated CAC progression was commonly observed, however most patients were under-optimized for cardiovascular (CV) risk, with less than half of statin-eligible patients with at least moderate CAC burden on statin therapy. Together, these data support more aggressive cardiac risk mitigation approaches, including guidelines-based CV risk factor modification and optimized sparing of LAD radiation dose.

Exosomes modified with anti-MEK1 siRNA lead to an effective silencing of triple negative breast cancer cells

Triple negative breast cancer (TNBC) is a highly heterogenous disease not sensitive to endocrine or HER2 therapy and standardized treatment regimens are still missing. Therefore, development of novel TNBC treatment approaches is of utmost relevance. Herein, the potential of MAPK/ERK downregulation by RNAi-based therapeutics in a panel of mesenchymal stem-like TNBC cell lines was uncovered. Our data revealed that suppression of one of the central nodes of this signaling pathway, MEK1, affects proliferation, migration, and invasion of TNBC cells, that may be explained by the reversion of the epithelial-mesenchymal transition phenotype, which is facilitated by the MMP-2/MMP-9 downregulation. Moreover, an exosome-based system was successfully generated for the siRNA loading (iExoMEK1). Our data suggested absence of modification of the physical properties and general integrity of the iExoMEK1 comparatively to the unmodified counterparts. Such exosome-mediated downregulation of MEK1 led to a tumor regression accompanied by a decrease of angiogenesis using the chick chorioallantoic-membrane model. Our results highlight the potential of the targeting of MAPK/ERK cascade as a promising therapeutic approach against TNBC.

Predictive modelling of response to neoadjuvant therapy in HER2+ breast cancer

HER2-positive (HER2+) breast cancer accounts for 20–25% of all breast cancers. Predictive biomarkers of neoadjuvant therapy response are needed to better identify patients with early stage disease who may benefit from tailored treatments in the adjuvant setting. As part of the TCHL phase-II clinical trial (ICORG10–05/NCT01485926) whole exome DNA sequencing was carried out on normal-tumour pairs collected from 22 patients. Here we report predictive modelling of neoadjuvant therapy response using clinicopathological and genomic features of pre-treatment tumour biopsies identified age, estrogen receptor (ER) status and level of immune cell infiltration may together be important for predicting response. Clonal evolution analysis of longitudinally collected tumour samples show subclonal diversity and dynamics are evident with potential therapy resistant subclones detected. The sources of greater pre-treatment immunogenicity associated with a pathological complete response is largely unexplored in HER2+ tumours. However, here we point to the possibility of APOBEC associated mutagenesis, specifically in the ER-neg/HER2+ subtype as a potential mediator of this immunogenic phenotype.

PR status is a more decisive factor in efficacy of adding pertuzumab into neoadjuvant therapy for HER2-positive and lymph node-positive breast cancer than ER status: a real-world retrospective study in China

BackgroundAlthough neoadjuvant trastuzumab and pertuzumab (HP)-based regimens are recommended for human epidermal receptor-positive (HER2 +)/lymph node-positive (N +) breast cancer (BC) patients according to NCCN guidelines, it is undeniable that many patients achieved pathological complete response (pCR) after trastuzumab (H)-based regimens without adding pertuzumab to treatment. Patients who specifically benefit from pertuzumab must be identified. The aim of this retrospective study was to evaluate progesterone receptor (PR) status as a predictor of response to the addition of pertuzumab in HER2 + /N + breast cancer.MethodsOne hundred forty-two patients who were diagnosed as HER2 + /N + BC without distant metastasis and followed by neoadjuvant HP-based or H-based therapy were retrospectively included. The endpoints were pCR and disease-free survival (DFS) times.ResultsIn total, the pCR occurred in 25 of 87 patients (28.74%) in group H compared with 32 of 55 (58.18%) in group HP. The results revealed that hormone receptor (HR) status was significantly different on pCR in group HP. The odds of pCR for patients who have HR-positive tumors were 0.160 times (P = 0.011) that for patients with HR-negative tumors by multivariable analysis. Moreover, a similar probability of PR-positive (PR +) patients, whatever estrogen receptor (ER) status was, achieving pCR in group HP was observed. The ROC curves showed different anti-HER2 regimens provide worst predictive value in the PR + cohort (N = AUC = 0.521, 95% CI: 0.348–0.694, P = 0.813) compared with the overall cohort (AUC = 0.644, 95% CI: 0.550–0.738, P = 0.004) and ER + cohort (AUC: 0.559, 95% CI: 0.405–0.713, P = 0.451). And PR status (AUC = 0.760, 95% CI: 0.626–0.894, P = 0.001) had a greater predictive value than ER status (AUC = 0.658, 95% CI: 0.508–0.807, P = 0.048) in group HP. DFS analyses were done on 141 patients. Although ER and PR status did not show significant difference in group HP (P = 0.789 and 0.088, respectively), HP-based therapy contributed to better DFS in the ER − and PR − cohorts (P = 0.035 and 0.015, respectively).ConclusionsCompared with ER status, PR status might be a more valuable factor predicting the efficacy of adding pertuzumab into neoadjuvant therapy for HER2 + /N + BC. PR + patients benefit little from the addition of pertuzumab.

Geospatial availability of breast cancer treatment modalities and hypothetical access improvement in Ghana: A nationwide survey.

Breast cancer in Ghana is a growing public health problem with increasing incidence and poor outcomes. Lack of access to comprehensive treatment in Ghana may be a contributing factor to its high mortality. The purpose of this study was to evaluate the availability of treatments nationwide and systematically identify high yield areas for targeted expansion. We conducted a cross-sectional, nationwide hospital-based survey from November 2020-October 2021. Surveys were conducted in person with trained research assistants and described hospital availability of all breast cancer treatments and personnel. All individual treatment services were reported, and hospitals were further stratified into levels of multi-modal treatment modeled after the National Comprehensive Cancer Network (NCCN) Framework treatment recommendations for low-resource settings. Level 3 included Tamoxifen and surgery (mastectomy with axillary lymph node sampling); Level 2 included Level 3 plus radiation, aromatase inhibitors, lumpectomy, and sentinel lymph node biopsy; Level 1 included Level 2 plus Her2 therapy and breast reconstruction. Hospitals were identified that could expand to these service levels based on existing services, location and personnel. The distance of the total population from treatment services before and after hypothetical expansion was determined with a geospatial analysis. Of the 328 participating hospitals (95% response rate), 9 hospitals had Level 3 care, 0 had Level 2, and 2 had Level 1. Twelve hospitals could expand to Level 3, 1 could expand to Level 2, and 1 could expand to Level 1. With expansion, the population percentage within 75km of Level 1, 2 and 3 care would increase from 42% to 50%, 0 to 6% and 44% to 67%, respectively. Multi-modal breast cancer treatment is available in Ghana, but it is not accessible to most of the population. Leveraging the knowledge of current resources and population proximity provides an opportunity to identify high-yield areas for targeted expansion.

Correlation of SUV on Early Interim PET with Recurrence-Free Survival and Overall Survival in Primary Operable HER2-Positive Breast Cancer (the TBCRC026 Trial).

Predictive biomarkers of response to human epidermal growth factor receptor 2 (HER2)-directed therapy are essential to inform treatment decisions. The TBCRC026 trial reported that early declines in tumor SUVs corrected for lean body mass (SULmax) on 18F-FDG PET/CT predicted a pathologic complete response (pCR) to HER2 therapy with neoadjuvant trastuzumab and pertuzumab (HP) without chemotherapy in estrogen receptor (ER)-negative, HER2-positive breast cancer. We hypothesized that 18F-FDG PET/CT SULmax parameters would predict recurrence-free survival (RFS) and overall survival (OS). Methods: Patients with stage II/III ER-negative, HER2-positive breast cancer received neoadjuvant HP (n = 88). pCR after HP alone was 22% (18/83), additional nonstudy neoadjuvant therapy was administered in 28% (25/88), and the majority received adjuvant therapy per physician discretion. 18F-FDG PET/CT was performed at baseline and at cycle 1, day 15 (C1D15). RFS and OS were summarized using the Kaplan-Meier method and compared between subgroups using logrank tests. Associations between 18F-FDG PET/CT (≥40% decline in SULmax between baseline and C1D15, or C1D15 SULmax ≤ 3) and pCR were evaluated using Cox regressions, where likelihood ratio CIs were reported because of the small numbers of events. Results: Median follow-up was 53.7 mo (83/88 evaluable), with 6 deaths and 14 RFS events. Estimated RFS and OS at 3 y was 84% (95% CI, 76%-92%) and 92% (95% CI, 87%-98%), respectively. A C1D15 SULmax of 3 or less was associated with improved RFS (hazard ratio [HR], 0.36; 95% CI, 0.11-1.05; P = 0.06) and OS (HR, 0.14; 95% CI, 0.01-0.85; P = 0.03), the latter statistically significant. The association of an SULmax decline of at least 40% (achieved in 59%) with RFS and OS did not reach statistical significance. pCR was associated with improved RFS (HR, 0.25; 95% CI, 0.01-1.24; P = 0.10) but did not reach statistical significance. Conclusion: For the first time, we report a potential association between a C1D15 SULmax of 3 or less on 18F-FDG PET/CT and RFS and OS outcomes in patients with ER-negative, HER2-positive breast cancer receiving neoadjuvant HP alone. If confirmed in future studies, this imaging-based biomarker may facilitate early individualization of therapy.

TIPS-19 TRIAL IN PROGRESS: SECONDARY BRAIN METASTASES PREVENTION AFTER ISOLATED INTRACRANIAL PROGRESSION ON TRASTUZUMAB/PERTUZUMAB OR T-DM1 IN PATIENTS WITH ADVANCED HUMAN EPIDERMAL GROWTH FACTOR RECEPTOR 2+ BREAST CANCER WITH THE ADDITION OF TUCATINIB (BRIDGET)

Abstract Despite trastuzumab-based therapy, up to half of patients with HER2+ metastatic breast cancer (MBC) will develop brain metastases (BrM). First-line therapy for HER2+ MBC, taxane/trastuzumab/pertuzumab (TP), demonstrates poor brain permeability. Isolated brain relapse with stable/absent extracranial disease remains a clinical problem in both the adjuvant and metastatic settings, and current guidelines recommend continuing current systemic therapy following local therapy. Tucatinib, a brain-penetrable HER2-inhibitor, when added to trastuzumab and capecitabine improves intracranial PFS and OS in patients with stable/active HER2+ BrMs. We hypothesize that adding tucatinib to TP or T-DM1 in patients with HER2+ MBC with isolated brain relapse or progression could delay or prevent the development of further intracranial lesions and improve OS. BRIDGET (NCT05323955) is a single arm, phase II study of tucatinib added to TP or T-DM1 after local therapy in patients with isolated brain relapse or progression. A total of 48 patients at 9 U.S. sites through HCRN with HER2+ MBC will be enrolled after 1st or 2nd BrM relapse/progression within 8 weeks of local therapy. Patients must currently be receiving TP or T-DM1 in the metastatic setting, or adjuvant trastuzumab-based or T-DM1 therapy with isolated brain recurrence. Extracranial disease must be stable per RECISTv1.1 or absent. Patients will receive tucatinib added to their current therapy. The primary objective is intracranial PFS compared to a historical control (H0: historical iPFS <5 months (mos), HA: iPFS >8 mos) of the HER2CLIMB trial. In these patients, median time from brain progression to second progression/death was 7.6 mos with tucatinib versus 3.1 mos in the control arm. Secondary endpoints include PFS by RECISTv1.1, PFS of extracranial disease, locally treated versus new distant intracranial metastasis PFS, site of first progression, OS, and toxicity. Collection of correlative specimens and patient-reported outcomes (FACT-BR, FACIT-Fatigue) are also included.

Zanidatamab (zani), a HER2-targeted bispecific antibody, in combination with docetaxel as first-line therapy (1L) for patients (pts) with advanced HER2-positive breast cancer (BC): Updated results from a phase Ib/II study.

1 Background: Despite HER2-targeted agents improving outcomes in HER2-positive (+) BC, some pts develop resistance, relapse, or do not respond to current 1L therapies. Zani, also known as ZW25, is a novel HER2-targeted bispecific antibody that binds to two distinct extracellular domains of HER2. Preliminary results from this Phase Ib/II trial (NCT04276493) showed that zani plus docetaxel had a manageable safety profile and demonstrated promising antitumor activity in pts with advanced HER2+ BC; here we present the updated data following enrollment completion. Methods: Cohort 1 of this open-label study is evaluating zani in combination with docetaxel as a 1L therapy in adult females with advanced HER2+ BC who may have received prior neoadjuvant/adjuvant therapy. Cohort 1a pts received zani 30 mg/kg intravenously (IV), Cohort 1b pts received zani 1800 mg IV, both with docetaxel 75 mg/m2 IV every 3 weeks. The primary endpoints were safety and investigator (INV)-assessed objective response rate (ORR) per RECIST v1.1. Secondary endpoints included INV-assessed duration of response (DoR) and disease control rate (DCR). Results: As of Nov 22, 2022, 37 pts(median age 55.0 years [range: 33-80]) were assigned to Cohort 1a (n=10) or 1b (n=27). Median study follow-up was 15.5 months (range: 1.1-29.3); patients received a median of 13 treatment cycles (range 1-37) and 18 (48.6%) pts remained on treatment. Of the 33-efficacy evaluable (EE) pts, confirmed ORR was 90.9% (95% confidence interval [CI]: 75.7, 98.1). Efficacy data are summarized in the table. In total, 36 (97.3%) pts experienced ≥1 treatment-related adverse event (TRAE); 25 (67.6%) pts experienced ≥grade 3 TRAEs. The most common ≥grade 3 TRAEs were decreased neutrophil count, experienced by 18 (48.6%) pts, and decreased white blood cell count, experienced by 7 (18.9%) pts. Serious TRAEs occurred in 6 (16.2%) pts; no TRAEs led to death. Conclusions: Zani combined with docetaxel demonstrated promising antitumor activity as 1L therapy for advanced HER2+ BC, with a manageable safety profile. Clinical trial information: NCT04276493 . [Table: see text]

A Prognostic Model Based on Residual Cancer Burden and Tumor-Infiltrating Lymphocytes on Residual Disease after Neoadjuvant Therapy in HER2+ Breast Cancer.

We aim to evaluate the prognostic significance of tumor-infiltrating lymphocyte on residual disease (RD-TIL) in HER2+ patients with breast cancer who failed to achieve pathologic complete response (pCR) after anti-HER2+ chemotherapy (CT)-based neoadjuvant treatment (NAT). We assessed the feasibility of combining the prognostic information provided by residual cancer burden (RCB) and RD-TILs into a composite score (RCB+TIL). HER2+ patients with breast cancer treated with CT+anti-HER2-based NAT at three institutions were retrospectively included. RCB and TIL levels were evaluated on hematoxylin and eosin-stained slides from surgical samples according to available recommendations. Overall survival (OS) was used as an outcome measure. A total of 295 patients were included, of whom 195 had RD. RCB was significantly associated with OS. Higher RD-TILs were significantly associated with poorer OS as compared with lower RD-TILs (15% cutoff). In multivariate analysis, both RCB and RD-TIL maintained their independent prognostic value. A combined score, RCB+TIL, was calculated from the estimated coefficient of RD-TILs and the RCB index in a bivariate logistic model for OS. The RCB+TIL score was significantly associated with OS. The C-index for OS of the RCB+TIL score was numerically higher than that of RCB and significantly higher than that of RD-TILs. We have reported an independent prognostic impact of RD-TILs after anti-HER2+CT NAT, which might underlie an imbalance of the RD microenvironment towards immunosuppressive features. We provided a new composite prognostic score based on RCB+TIL, which was significantly associated with OS and proved to be more informative than the isolated evaluation of RCB and RD-TILs.

The effect of the alpha-specific PI3K inhibitor alpelisib combined with anti-HER2 therapy in HER2+/PIK3CA mutant breast cancer.

HER2 is amplified or overexpressed in around 20% of breast cancers (BC). HER2-targeted therapies have significantly improved the prognosis of patients with HER2+ BC, however, de novo and acquired resistance to anti-HER2 treatment is common. Activating mutations in the PIK3CA gene are reported in ∼30% of HER2+ BC and are associated with resistance to anti-HER2 therapies and a poor prognosis. Here, we investigated the in vitro and in vivo antitumor efficacy of the alpha-specific PI3K inhibitor alpelisib alone or in combination with anti-HER2 therapy using a panel of HER2+ BC cell lines. We also generated models of acquired resistance to alpelisib to investigate the mechanisms underlying resistance to alpha-specific PI3K inhibition. PIK3CA mutant (HCC1954, KPL4 and JMT1) and wild-type (BT474 and SKBR3) HER2+ BC cell lines were used. The HCC1954 and KPL4 cells were chronically exposed to increasing concentrations of alpelisib or to alpelisib + trastuzumab in order to generate derivatives with acquired resistance to alpelisib (AR) and to alpelisib + trastuzumab (ATR). The transcriptomic profiles of HCC1954, KPL4 and their AR and ATR derivatives were determined by RNA sequencing. Cell growth was assessed by MTT assay. Changes in the protein levels of key PI3K pathway components were assessed by Western blotting. Gene expression, cellular and patients' data from the Cancer Dependency Map (DepMap) and KMPlot datasets were interrogated. HER2+ BC cell lines harboring activating mutations in PIK3CA were less sensitive to single or dual anti-HER2 blockade compared to PIK3CA wild-type cells. Alpelisib treatment resulted in dose-dependent inhibition of the growth of cells with or without PIK3CA mutations and enhanced the antitumor efficacy of anti-HER2 therapies in vitro. In addition, alpelisib greatly delayed tumor growth of HCC1954 xenografts in vivo. Functional annotation of the significantly differentially expressed genes suggested the common activation of biological processes associated with oxidation reduction, cell proliferation, immune response and RNA synthesis in alpelisib-resistant models compared with native cells. Eight commonly upregulated genes (log2 fold-change >1, False Discovery Rate [FDR] <0.05) in models with acquired resistance to alpelisib or alpelisib + trastuzumab were identified. Among these, AKR1C1 was associated with alpelisib-resistance in vitro and with a poor prognosis in patients with HER2+ BC. Our findings support the use of an alpha-selective PI3K inhibitor to overcome the therapeutic limitations associated with single or dual HER2 blockade in PIK3CA-mutant HER2+ breast cancer. Future studies are warranted to confirm the potential role of candidate genes/pathways in resistance to alpelisib.

Intrathecal trastuzumab versus alternate routes of delivery for HER2-targeted therapies in patients with HER2+ breast cancer leptomeningeal metastases.

Patients with HER2+ breast cancer (BC) frequently develop leptomeningeal metastases (LM). While HER2-targeted therapies have demonstrated efficacy in the neoadjuvant, adjuvant, and metastatic settings, including for parenchymal brain metastases, their efficacy for patients with LM has not been studied in a randomized controlled trial. However, several single-armed prospective studies, case series and case reports have studied oral, intravenous, or intrathecally administered HER2-targeted therapy regimens for patients with HER2+ BC LM. We conducted a systematic review and meta-analysis of individual patient data to evaluate the efficacy of HER2-targeted therapies in HER2+ BC LM in accordance with PRISMA guidelines. Targeted therapies evaluated were trastuzumab (intrathecal or intravenous), pertuzumab, lapatinib, neratinib, tucatinib, trastuzumab-emtansine and trastuzumab-deruxtecan. The primary endpoint was overall survival (OS), with CNS-specific progression-free survival (PFS) as a secondary endpoint. 7780 abstracts were screened, identifying 45 publications with 208 patients, corresponding to 275 lines of HER2-targeted therapy for BC LM which met inclusion criteria. In univariable and multivariable analyses, we observed no significant difference in OS and CNS-specific PFS between intrathecal trastuzumab compared to oral or intravenous administration of HER2-targeted therapy. Anti-HER2 monoclonal antibody-based regimens did not demonstrate superiority over HER2 tyrosine kinase inhibitors. In a cohort of 15 patients, treatment with trastuzumab-deruxtecan was associated with prolonged OS compared to other HER2-targeted therapies and compared to trastuzumab-emtansine. The results of this meta-analysis, comprising the limited data available, suggest that intrathecal administration of HER2-targeted therapy for patients with HER2+ BC LM confers no additional benefit over oral and/or IV treatment regimens. Although the number of patients receiving trastuzumab deruxtecan in this cohort is small, this novel agent offers promise for this patient population and requires further investigation in prospective studies.

A systematic review and meta-analysis of intrathecal versus alternate routes of delivery for HER2-targeted therapies in patients with HER2+ breast cancer leptomeningeal metastases.

2034 Background: Patients with HER2+ breast cancer (BC) frequently develop leptomeningeal metastases (LM). While HER2-targeted therapies have demonstrated efficacy in the neoadjuvant, adjuvant, and metastatic settings, including for parenchymal brain metastases, their efficacy for patients with LM has not been studied in a randomized controlled trial. However, several single-armed prospective studies, case series and case reports have studied oral, intravenous (IV), or intrathecally (IT) administered HER2-targeted therapy regimens for patients with HER2+ BCLM. Methods: We conducted a systematic review and meta-analysis of individual patient data to evaluate the efficacy of HER2-targeted therapies in HER2+ BCLM in accordance with PRISMA guidelines. Targeted therapies evaluated were trastuzumab (IT or IV), pertuzumab, lapatinib, neratinib, tucatinib, trastuzumab-emtansine (T-DM1) and trastuzumab-deruxtecan (TDXd). The primary endpoint was overall survival (OS), with progression-free survival (PFS) as a secondary endpoint. To assess differences between groups, shared frailty Cox regression models were used to estimate the hazard ratio (HR), 95% confidence interval (CI) and p-value. Results: 7780 abstracts were screened, identifying 44 publications with 200 patients, corresponding to 257 lines of HER2-targeted therapy for BC LM which met inclusion criteria. In univariable (OS: HR=0.9, 95% CI: 0.64-1.4, P=0.76; PFS: HR=0.8, 95% CI: 0.57-1.2, P=0.35) and multivariable (OS: HR=1.4, 95% CI: 0.68-3.1, P=0.4; PFS: HR=0.8, 95% CI: 0.41-1.7, P=0.6) analyses, we observed no significant difference between IT, oral or IV administration of HER2-targeted therapy. Meanwhile, ECOG performance status remained independently associated with prolonged OS (HR=2.2, 95% CI: 1.5-3.2, P&lt;0.001) and PFS (HR=2.2, 95% CI: 1.5-3.2, P&lt;0.001 and HR=1.9, 95% CI: 1.4-2.8, P&lt;0.001) in the final multivariable model. ECOG status was not associated with route of trastuzumab delivery (P&gt;0.40). Anti-HER2 monoclonal antibody-based regimens did not demonstrate superiority over HER2 tyrosine kinase inhibitors (OS: P=0.647; PFS: P=0.983). In a cohort of 7 patients, TDXd demonstrated improved OS compared to other HER2-targeted therapies and compared to T-DM1 (P&lt;0.05). Conclusions: The results of this meta-analysis suggest that IT administration of HER2-targeted therapy for patients with HER2+ BCLM confers no additional benefit over oral and/or IV treatment regimens. We also present the first evidence supporting the efficacy of TDXd compared to alternative strategies for this patient population. Although the number of patients receiving TDXd in this cohort is small, this novel agent offers promise for this patient population and requires further investigation in prospective studies.

Preliminary analysis of pyrotinib and dalpiciclib-based therapy in HER2-positive advanced breast cancer (ABC).

e13027 Background: The efficacy of cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) and HER2 target agents combined with endocrine treatment (ET) has been demonstrated in hormone receptor (HR)-positive and HER2+ ABC, while little was known about the role of CDK4/6i in HR-/HER2+ ABC. In this prospective, multi-center, multi-cohort, phase 2 study (NCT04095390), we assessed the efficacy and safety of pyrotinib (P) and a CDK4/6i, dalpiciclib (D)-based therapy in HER2+ ABC with disparate HR statuses. Methods: HER2+ ABC females with known HR status were eligible if previously treated with trastuzumab (T). No more than one prior systemic regimen in advanced setting was allowed. Cohort A: HR+ pts received P (320 mg QD) and D (125 mg QD, 21 days on and 7 days off) combined with letrozole (2.5 mg QD). Cohort B or C: HR- pts were randomized to receive P and D combined with or without capecitabine (500 mg TID). Pts were treated until progression or unaccepted toxicity. The primary endpoint was objective response rate (ORR) per RECIST 1.1. Results: As of Jan. 16, 2023, 33 pts were enrolled. We describe pts' distribution and characteristics. 26 pts had at least one efficacy assessment, and 17 (65.4%) achieved confirmed objective responses. ORR was 66.7% (10/15), 80% (4/5), and 50% (3/6) in cohort A, B, and C, respectively. Among the ITT population, the estimated median PFS was 24.9 mo. (24.9 mo., NR, and 20.2 mo. in cohort A, B, and C, respectively). 32 (97.0%) pts experienced treatment-related adverse events (TRAEs). Grade (G) 3-4 TRAEs occurred in 81.8% of pts, and the most frequent (≥ 10%) ones were neutropenia (72.7%), leukopenia (57.6%), diarrhea (21.2%), and mucositis (12.1%). Safety profiles were similar among cohorts, except more G3-4 mucositis, hand-foot syndrome and thrombocytopenia in cohort B. Two in cohort B discontinued due to toxicity (1 rash, and 1 neutropenia). One death was reported after withdrawal and unrelated to the study. Median OS was not reached. Conclusions: Our study shows P and D combined with ET is effective in HR+/HER2+ ABC, providing a chemo-free option to these pts. In HR-/HER2+ ABC, we preliminarily observed that the addition of chemotherapy could improve effectiveness of P and D, but also increase toxicities. Due to the limited sample, the findings need further confirmation. Clinical trial information: NCT04095390 . [Table: see text]

Use of PARPi among patients with HER2+ve MBC: Results from a real world dataset.

e13044 Background: Among individuals with germline mutations in BRCA1/ BRCA2 genes, life-time risk of developing breast cancer is approximately 50%. The majority of these cancers are HER2-ve with a low frequency of HER2+ve breast cancer (2.1%-10% in pts with BRCA1 mutations and 6.8%-13% of pts with BRCA2 mutations) with co-occurrence of BRCA mutation and HER2+ve status being a poor prognostic factor. PARPi have been shown in phase III trials to be effective in HER2-ve BRCA mutation MBC. The objective of this retrospective analysis was to look at the prognostic outcome associated with use of PARPi among pts with HER2 +ve BRCA mutated MBC in the real-world setting. Methods: We utilized a federated network of de-identified health data representing approximately 107 million pt lives available through the TriNetX Research Network. We identified patients with MBC who were treated with PARPi, and pts were assumed to have BRCA mutated MBC if they were recorded with a PARPi. Overall survival (OS) was computed using the Kaplan Meier product limit method. Pts with MBC were defined as having HER2+ve status if they received an anti-HER2 therapy after metastasis, HR+ve if they received endocrine therapy after metatstasis, and triple negative (TNBC) if they did not receive anti-HER2 therapy or endocrine therapy. Results: 1369pts with MBC were treated with PARPi, of whom 77.9%received olaparib. Mean age of pts was 57ys. 546(39.9%), 521(38.1%) and 73(5.3%) pts had TNBC, HR+ve/HER2-ve, and HER2+ve MBC, respectively. Among pts with HER2+ve disease, 35.2% and 74.0% had HR-ve and HR+ve MBC, respectively. Median time to use of PARPi was 7.1m, 15.1m, and 24.0m among pts with TNBC, HR+ve/HER2-ve, and HER2 +ve MBC respectively. Median OS was 44.4m, 47.0m, and 46.7m among pts with TNBC, HR+ve/HER2-ve and HER2+ve MBC respectively. Among pts with HER2+ve disease, median OS was 74.5m and 31.5m among pts with HR+ve and HER-ve disease, respectively (HR=0.27, p=0.0001). 321(23.4%) pts had brain metastases of whom 36.8%, 36.4% and 8.1% had TNBC, HR+ve/HER2-ve and HER2+ve MBC respectively. Among pts with HER2+ve MBC,38.3% received anti HER2 therapy before PARPi, 24.7% received anti HER2 therapy after PARPi and 37.0% received PARPi and anti HER2 therapy concurrently. Among pts with HER2+ve disease, median OS was 44.4m among those who received anti -HER2 therapy on or before PARPi and 93.8m among those who received anti-HER2 therapy after PARPi (HR 0.83, p=0.64).Among pts with brain metastases, median OS was 23.9m, 40.0m and 40.2m among pts with TNBC, HR+ve/HER-ve and HER2+ve MBC respectively. Conclusions: To our knowledge this is the first real world data set to report on the prognostic outcome of pts with HER2+ve BRCA mutated MBC. When PARPi inhibitors are given median OS is similar among the three subtypes of breast cancer. Although not significant, there appears to be a trend towards improved OS with earlier use of PARPi among patients with HER2+ve BRCA mutated MBC.