anti-HER2 Treatment Research Articles

Abstract PO3-22-06: Safety and efficacy of trastuzumab deruxtecan and concomitant radiation therapy in patients with metastatic HER2-positive breast cancer

Abstract Background Trastuzumab deruxtecan (T-DXd) currently represents the standard of care for the treatment of patients with metastatic HER2-positive (HER2+) breast cancer (BC) after disease progression in the first line, which includes taxanes and trastuzumab. This recommendation is based on the results of the DESTINY-Breast03 trial, which demonstrated improved efficacy compared to trastuzumab emtansine (T-DM1). Radiation therapy (RT) is frequently required in the metastatic setting, either for palliative purposes or with ablative intent in cases of oligometastatic or oligoprogressive disease. The aim of our study is to evaluate the safety of using T-DXd and concomitant radiation therapy (RT) in a consecutive series of HER2+ BC patients. Methods We conducted a retrospective evaluation of patients diagnosed with metastatic HER2+ BC who initiated treatment with T-DXd between May 2021 and May 2023 at our institution, with or without receiving RT. We collected clinical data pertaining to the diagnosis of metastatic disease, T-DXd treatment, acute toxicities, survival data, and biological characteristics of both the primary tumor and metastases. The primary objective of this study was to assess the association between RT and any adverse events greater than grade (G) 2. Results We retrospectively evaluated data from 30 consecutive patients who were treated with T-DXd, with or without RT. Among these patients, ten received RT either immediately before (within a month) or during T-DXd treatment, while the remaining 20 did not. The median age of the patients was 72 years (range 34-88), and the median follow-up period was 9 months. Thirteen patients received T-DXd as the fourth or subsequent line of systemic anti-HER2 treatment, eight patients received it as the third line, and seven patients received it as the second line. Two patients, who experienced early metastatic disease relapse (< 6 months after completion of adjuvant anti-HER2 therapy), received T-DXd as their first-line treatment. The median prescribed total dose of RT was 34 Gy (range 20-48), with a median number of fractions of 4 (range 2-10). The median equivalent dose in 2 Gy fractions (EQD2) was 64 Gy (range 23.3-104), and the median biologically effective dose (BED) was 76 Gy (range 28-125). The most commonly treated sites were bone (70% of cases), followed by brain (20%) and liver (10%). A chi-square test of independence was conducted to examine the relationship between the administration of RT and the development of toxicity exceeding G2. However, this analysis did not reveal a significant relationship (p = .27). Regarding the specific toxicities of interest associated with T-DXd, three cases of grade 3 fatigue were reported in the group that did not receive RT, while one case was observed in the RT group. Overall, only one case of grade 3 nausea was reported, and it occurred in the group that did not receive RT. G2 interstitial lung disease, which led to discontinuation of T-DXd, was observed in one case in the RT group and one case in the no-RT group. Conclusions Our initial data is promising regarding the potential safety of this combination, as it indicates that concurrent RT did not lead to an increase in severe acute toxicity. However, larger series of data are required to validate and confirm these findings. Citation Format: Luca Visani, Carlotta Becherini, Niccolo' Bertini, Ilaria Bonaparte, Luca Burchini, Carolina Orsatti, Marianna Valzano, Marco Banini, Viola Salvestrini, Erika Scoccimarro, Vieri Scotti, Isacco Desideri, Giulio Francolini, Lorenzo Orzalesi, Marco Bernini, Cinzia Tommasi, Jacopo Nori, Simonetta Bianchi, Icro Meattini, Lorenzo Livi. Safety and efficacy of trastuzumab deruxtecan and concomitant radiation therapy in patients with metastatic HER2-positive breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-22-06.

Abstract PO4-26-08: Prevalence of HER2-low and IHC >0 to < 1+ in breast cancer and its concordance between historical and rescored results: a multi-center, retrospective study in China

Abstract Background: With Trastuzumab deruxtecan (T-DXd) changing the anti-HER2 treatment paradigm, HER2-low (defined as IHC2+/ISH- and IHC1+) breast cancer patients have emerged as a new targetable population. The lower threshold for HER2 expression that can benefit from HER2-directed antibody-drug conjugates (ADCs) is still being investigated, such as HER2 immunohistochemistry (IHC) >0 to < 1+ (defined as IHC 0 with incomplete and faint staining in ≤10% of tumor cells) in the DESTINY-Breast06 trial. Accurate determination of HER2 scores has become a critical topic in clinical discussions, given its clinical relevance to HER2-directed treatment strategies. Hence, we conduct this study (HER2-PATH, NCT05203458) to evaluate the distribution of HER2 status including HER2 IHC >0 to < 1+ in Chinese patients with breast cancer. Concordance between rescored and historical results was also analyzed. Methods: A retrospective study was conducted in breast cancer patients who underwent surgery at 10 sites in China between July 2021 and July 2022. Archived HER2 IHC slides from these patients were subjected to rescoring by a review committee comprising two readers and one adjudicator. The two readers independently evaluated each slide blinded to the historical scores. If their results matched, the recorded outcome was considered final. In cases of disagreement, the adjudicator made the final judgment. All slides were stained using Ventana 4B5 and scored following the ASCO/CAP 2018 guidelines, including the addition of the IHC >0< 1+ as defined in the DESTINY-Breast06 trial. The prevalence of the rescored HER2 status was calculated, and the concordance between the historical and rescored HER2 status was assessed using the Cohen's Kappa coefficient. Results: A total of 2868 patients were included in the analysis. The rescored results categorized 682 (23.8%) patients as HER2 IHC 0, 871 (30.4%) patients as IHC 1+, 800 (27.9%) patients as IHC 2+, and 515 (18.0%) patients as IHC 3+. The rates of HER2-positive, HER2-low, and HER2 IHC 0 (including HER2 null and HER2 IHC >0 to < 1+) were 21.8%, 54.3% and 23.9%, respectively. Notably, the prevalence of HER2-low was numerically higher in the HR-positive subgroup compared to the HR-negative subgroup (60.2% vs 30.6%). Furthermore, the prevalence of HER2 IHC >0 to < 1+ and HER2 null was 10.6% and 13.2% among all patients, respectively. Among the HR-positive subgroup, the prevalence of HER2 IHC >0 to < 1+ was 10.9%, while the rate was 9.1% among the HR-negative subgroup. Overall, there was an 83.1% concordance between the historical and rescored results for HER2 IHC scores. The concordance rate for IHC 1+ was numerically lower (74.5%) compared to IHC 0 (85.2%), IHC 2+ (81.4%), and IHC 3+ (98.6%). However, considering that 12.0% of IHC 1+ patients turned into IHC 2+ with limited impact on HER2-low diagnosis, the concordance rate for HER2-low remained as 91.6%. Conclusion: HER2-low prevalence in Chinese breast cancer patients was found to be consistent with global data, while additional 10.6% of patients were identified as HER2 IHC >0 to < 1+, which is currently being investigated in a randomized controlled trial comparing T-DXd with SoC. To our knowledge, this is the first study to report the prevalence of HER2-low, including HER2 IHC >0 to < 1+, in the Chinese breast cancer population based on rescored results. The concordance of HER2-low between the historical and rescored results was 91.6%, indicating that most cases could be reproducibly classified. Table: Rescored HER2 Expression Level Citation Format: Hong Lv, Junqiu Yue, Qingfu Zhang, Fangping Xu, Jianming Li, Lingfei Kong, Peng Gao, Guanjun Zhang, Haifeng Yang, Xiu Nie, Wen-Tao Yang. Prevalence of HER2-low and IHC >0 to < 1+ in breast cancer and its concordance between historical and rescored results: a multi-center, retrospective study in China [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-26-08.

Abstract PO2-20-01: The STOP-HER2 Trial: A Phase 2 Study of Stopping Trastuzumab - Outcomes in Patients with HER2+ Metastatic Breast Cancer (TBCRC 062)

Abstract BACKGROUND: Anti-HER2 therapies have transformed the trajectory for patients with HER2-positive (HER2+) MBC. A subset of patients with HER2+ MBC do exceptionally well and remain on maintenance anti-HER2 therapy for many years. However, current therapy is non-curative and patients are treated indefinitely. While these therapies often are well-tolerated, they may cause significant toxicities, are expensive, and typically require frequent infusion and provider visits. Case reports and retrospective series demonstrate that some patients may do well after stopping anti-HER2 treatment. We currently lack prospective data on the likelihood of clinical impact of successful treatment discontinuation, outcomes among patients who progress and restart HER2-directed therapy, and tools to predict who may safely stop therapy. In this study, we will enroll pts with an exceptional response to anti-HER2 therapy. Pts may elect to either continue or stop anti-HER2 therapy and will be followed clinically and radiographically on a protocol-specified schedule. Considering the central role of patients in choosing the study intervention arm, and the unique nature of stopping therapy as a treatment intervention, patient advocates have been deeply involved in the study design to ensure patient concerns are being heard and addressed. We will retrospectively assess minimal residual disease (MRD), measured in plasma, as a biomarker of ongoing response, in a step toward shifting the treatment paradigm for pts with HER2+ MBC. METHODS: STOP-HER2 is a prospective, non-randomized, phase II, multicenter study of either continuation (cohort 1) or cessation (cohort 2) of anti-HER2 therapy in exceptional responders with HER2+ MBC. Eligible patients must have biopsy-proven HER2+ MBC by ASCO/CAP guidelines and must have been receiving first-line anti-HER2 therapy for MBC for at least 3 years without evidence of progressive disease (PD) as determined by the treating investigator. Patients with prior brain-only PD or oligo-PD outside the brain are eligible at least 2 years after local treatment to the central nervous system (CNS) and in absence of subsequent PD. Up to fifty-two participants will be enrolled into cohort 2, and an additional thirty participants enrolled into the cohort 1, at 10 US sites within the Translational Breast Cancer Research Consortium. Co-primary endpoints are the 1-year progression-free survival (PFS) in cohorts 2 and 1, separately. Secondary endpoints include the clinical benefit rate upon re-initiation of anti-HER2 therapy for patients in cohort 2 experiencing PD after treatment discontinuation; and 3-year overall survival in both cohorts. Correlative endpoints include MRD status at baseline and the correlation between MRD dynamics and outcomes. Patient-reported outcomes will be collected and analyzed, including quality of life, illness intrusiveness, financial toxicity, anxiety, and decision regret. The study will use a two-stage design to assess the primary objective of estimating the rate of participants who are free of progression at one year after discontinuing anti-HER2 therapy. If 50% or less are free of progression at one year, stopping HER2 therapy would not be considered a viable treatment plan (null hypothesis). The study is designed to have 80% power to reject the null hypothesis at the 10% type I error rate when 68% of exceptional responders are free of progression at one year after stopping HER2 therapy. STOP-HER2 began enrollment in Q2 2023 (NCT05721248). Citation Format: Heather Parsons, Kathryn Ruddy, Stefania Morganti, Karen Smith, Victoria Attaya, Eliza Kallfelz, Michelle DeMeo, Jamie LaScala, Shirley Mertz, Teri Pollastro, Patricia Spears, Adam Brufsky, Chau Dang, Susan Dent, Ahmed Elkhanany, WIlliam Gwin, Ciara O'Sullivan, Kathy Miller, Sara Nunnery, Elaine Walsh, Anna Maria Storniolo, Sara Tolaney, Nabihah Tayob, Antonio Wolff, Eric Winer, Mothaffar Rimawi, Ian Krop, Nancy Lin. The STOP-HER2 Trial: A Phase 2 Study of Stopping Trastuzumab - Outcomes in Patients with HER2+ Metastatic Breast Cancer (TBCRC 062) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-20-01.

Abstract PO3-16-12: European real-world experience of patients with HER2+ advanced/metastatic breast cancer accessing trastuzumab deruxtecan through a named patient program: first interim analysis of EUROPA T-DXd

Abstract Background: In 2021, trastuzumab deruxtecan (T-DXd) monotherapy was conditionally approved in the EU for adult patients with human epidermal growth factor receptor 2-positive (HER2+) advanced/metastatic breast cancer (mBC). A named patient program (NPP) was initiated (March 2021) to enable eligible patients with an unmet medical need to gain access to T-DXd when not yet available locally, either commercially or through an appropriate clinical trial. Centers that treated/are treating patients under this NPP were invited to participate in EUROPA T-DXd real-world data (RWD) collection. Methods: EUROPA T-DXd is an ongoing, multicenter (Ireland, Italy, and Spain), observational (retro- and prospective) study of RWD from approximately 200 adult patients with HER2+ advanced/mBC who had received ≥2 prior anti-HER2 regimens and for whom T-DXd was initiated through the NPP. Collection of RWD is optional and independent of eligibility for the NPP. The primary objective is to estimate real-world time to treatment discontinuation (rwTTD). Secondary objectives include real-world progression-free survival (rwPFS), reasons for T-DXd discontinuation, safety, and prior anti-HER2 treatment patterns. Results: This first interim analysis included 84 evaluable patients. Patients had a mean (standard deviation) age of 53.4 (11.1) years; most were female (97.6%) and had HER2 immunohistochemistry 3+ (70.2%), and 44% had received >3 prior lines of anti-HER2 therapy in the metastatic setting (Table). At data cutoff (June 5, 2023), 50 (59.5%) patients were still receiving T-DXd. In total, 34 patients (40.5%) discontinued T-DXd (death, n=1 [1.2%]; adverse event, n=3 [3.6%]; disease progression, n=26 [31%]; or other, n=4 [4.8%]). Median rwTTD was 21.4 months (95% confidence interval 17.6, not estimated), and median rwPFS was not reached. The results of the wider cohort will be presented at the meeting, including adverse events. Conclusion: Results from this first interim analysis confirm the efficacy of T-DXd in heavily pretreated patients with HER2+ mBC. Baseline characteristics and demographics are comparable to the clinical trial setting. Analyses are ongoing and will provide more mature rwTTD and rwPFS. XX XX Citation Format: Michelino De Laurentiis, José Ángel García-Sáenz, Giampaolo Bianchini, Cristina Saura, Hans Wildiers, Arthur Allignol, Amanda Logue, Markus Lucerna, Sabine Stamenitis. European real-world experience of patients with HER2+ advanced/metastatic breast cancer accessing trastuzumab deruxtecan through a named patient program: first interim analysis of EUROPA T-DXd [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-16-12.

Abstract PO4-04-07: Efficacy, safety and translational study of pyrotinib combined with albumin-bound paclitaxel as firstline treatment of HER-2 positive metastatic breast cancer

Abstract Objective: Breast Cancer is one of the most common malignant tumors in women. HER-2 is a driver gene for poor prognosis in breast cancer. Anti-HER-2 drugs have significantly improved the prognosis of patients with HER-2 positive metastatic breast cancer. There is still a lack of exploration of first-line anti-HER2 treatment options and translational studies only for patients with metastases after adjuvant and/or neoadjuvant trastuzumab therapy. This study is based on our previous clinical trial of pyrotinib in combination with albumin-bound paclitaxel in first line for patients with HER-2-positive metastatic breast cancer after adjuvant and/or neoadjuvant trastuzumab therapy, with the aim of exploring the efficacy and adverse events in the enrolled patients. And to explore the markers associated with Progression Free Survival (PFS) by using Olink technique to detect blood samples from patients. To provide a better screening of the benefit population and provide guidance for the treatment of HER-2 positive metastatic breast cancer. Methods: From December 2019 to July 2023, our previous clinical trial prospectively enrolls 27 patients with HER-2-positive metastatic breast cancer after adjuvant and/or neoadjuvant trastuzumab therapy. Pyrotinib (400 mg, po, qd) combined with albumin-bound paclitaxel (200 mg, ivdrip, d1, d8, q21d) was used as the first-line treatment regimen. Patients were evaluated for efficacy. Survival analysis was performed by using the Kaplan-Meier method. Blood samples were collected during treatment. We selected 21 blood samples from patients, and dynamically detected plasma protein changes by Olink technique. Differential protein analysis between groups according to hormone receptor status, trastuzumab primary/secondary resistance, and the presence of visceral metastases. And the proteins associated with PFS were analyzed. Results: Among the 27 patients whose efficacy had been evaluated, 7 patients were evaluated as CR, 18 patients as PR, and 2 patients as SD. The objective response rate was 92.6%, and the disease control rate was 100%. The median follow-up was 17.8 months and the median PFS has not yet been reached. Diarrhea is the most common adverse event. Grade 3 or higher adverse events include diarrhea, leukocytopenia, neutropenia, and hand-foot syndrome. The progression free survival was significantly worse in patients with visceral metastases (P=0.01). Results of Olink protein dynamic assay showed a significant downregulation of CEACAM5, TXLNA, PVRL4and ERBB2. Differential proteins between groups showed that there were no significant differential proteins between the hormone receptor-positive and negative groups at the baseline node, but 7 proteins were upregulated in the hormone receptor-positive group compared with the negative group at the progression node, with EMS-1, WIF-1, and hK14 being the most significant. Compared to primary resistance, trastuzumab secondary resistance appeared 4 proteins upregulated at the baseline node, with hK14 and CYR61 being the most significantly; and 33 proteins were upregulated at the progression node, with CYR61, CXL17, FURIN, and ABL1 being the most significantly. Patients with high expression of TLR3 and low expression of RET at the baseline node had longer PFS. Conclusions: This study demonstrates that pyrotinib in combination with albumin-bound paclitaxel as a first-line treatment regimen shows good efficacy and a manageable safety for patients with HER-2-positive metastatic breast cancer after adjuvant and/or neoadjuvant trastuzumab therapy. PFS was shorter in patients with visceral metastases. TLR3 and RET were the proteins that significantly associated with PFS in patients. Citation Format: Huihui Li, Xiaochu Man, Sha Yin, Dongdong Zhou, Baoxuan Zhang, Shu Fang, Fangchao Zheng, Chao Li, Xinzhao Wang, Wei Huang, Linlin Wang, Qingqing He, Hui Fu, Yan Zhang, Changrui Liu, Lin Dong, Xianguang Zhao, Liang Xu, Xiao Sun, Bingjie Fan, Lihua Song, Zhengbo Zhou, Qiaorui Tan, Jinming Yu. Efficacy, safety and translational study of pyrotinib combined with albumin-bound paclitaxel as firstline treatment of HER-2 positive metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-04-07.

Efficacy and safety of pyrotinib combined with albumin-bound paclitaxel as first-line treatment for HER2-positive metastatic breast cancer in patients previously treated with adjuvant and/or neoadjuvant trastuzumab therapy: The stage 1 results of a single-arm, phase 2 prospective clinical trial.

It has been observed that the prognosis of patients with HER2-positive metastatic breast cancer has improved significantly with HER2-targeted agents. However, there is still a lack of evidence regarding first-line anti-HER2 treatment options for patients who have received adjuvant and/or neoadjuvant trastuzumab for HER2-positive metastatic breast cancer. Besides, there are no reliable markers that can predict the efficacy of anti-HER2 treatment in these patients. Patients who have received adjuvant and/or neoadjuvant trastuzumab for HER2-positive metastatic breast cancer were enrolled. Pyrotinib plus albumin-bound paclitaxel were used as first-line treatment. The primary endpoint was the objective response rate (ORR). The safety profile was also assessed. In order to explore predictive biomarkers using Olink technology, blood samples were collected dynamically. From December 2019 to August 2023, the first stage of the study involved 27 eligible patients. It has not yet reached the median PFS despite the median follow-up being 17.8 months. Efficacy evaluation showed that the ORR was 92.6%, and the DCR was 100%. Adverse events of grade 3 or higher included diarrhoea (29.6%), leukopenia (11.1%), neutropenia (25.9%), oral mucositis (3.7%), and hand-foot syndrome (3.7%). Toll-like receptor 3 (TLR3) and Proto-oncogene tyrosine-protein kinase receptor (RET) were proteins with significant relevance to PFS in these patients. This study demonstrates that pyrotinib plus albumin-bound paclitaxel as a first-line treatment regimen shows good efficacy and manageable safety for patients who have received adjuvant and/or neoadjuvant trastuzumab for HER2-positive metastatic breast cancer. Besides, a significant association was identified between the expression levels of TLR3 and RET and the PFS in patients.

Perspectives on shorter durations of anti-HER2 therapy in early-stage HER2-positive breast cancer: a patient survey.

Despite previous studies proposing shorter durations of anti-HER2 therapy for selected patients with HER2-positive early breast cancer (EBC), 12-months remains standard of care. A survey was performed to assess patient perspectives and willingness to participate in studies evaluating shorter durations of anti-HER2 therapy. Patients with HER2-positive EBC completing or having previously completed anti-HER2 therapy, were recruited by healthcare professionals at The Ottawa Hospital Cancer Centre to participate in an anonymous online survey. The primary objective was to learn about patients' perspectives on shorter durations (less than 12-months) of anti-HER2 therapy. Secondary objectives were to explore patients' interest in clinical trials of shorter durations of anti-HER2 therapy and the degree of increased breast cancer risk they would accept with a shorter treatment duration. Responses were received from 94 eligible patients. Most patients received Trastuzumab alone (78%, 73/94), while 13% (12/94) received trastuzumab and pertuzumab. Side effects were experienced by 52% (46/89), the most common being; fatigue (61%, 28/46), myalgia (37%, 17/46), and diarrhea (24%, 11/46). Most patients (88%, 78/89) did not find treatment bothersome. Regarding perspectives on shorter durations of anti-HER2 therapy, most (79%, 74/94) respondents stated they would agree to less treatment if it were possible to receive fewer treatments with the same cancer benefits. 56% of patients were interested in clinical trials, however, about half stated they would not be accepting of any increase in breast cancer recurrence risk. Trials to investigate who can safely and effectively be treated with shorter durations of anti-HER2 therapy are needed. This study provides important insights to patients' perspectives on shorter durations of anti-HER2 treatment, and their concerns regarding potential increased cancer risk with less treatment.

Identification of ADME genes polymorphic variants linked to trastuzumab-induced cardiotoxicity in breast cancer patients: Case series of mono-institutional experience

BackgroundLong-term survival induced by anticancer treatments discloses emerging frailty among breast cancer (BC) survivors. Trastuzumab-induced cardiotoxicity (TIC) is reported in at least 5% of HER2+BC patients. However, TIC mechanism remains unclear and predictive genetic biomarkers are still lacking. Interaction between systemic inflammation, cytokine release and ADME genes in cancer patients might contribute to explain mechanisms underlying individual susceptibility to TIC and drug response variability. We present a single institution case series to investigate the potential role of genetic variants in ADME genes in HER2+BC patients TIC experienced. MethodsWe selected data related to 40 HER2+ BC patients undergone to DMET genotyping of ADME constitutive variant profiling, with the aim to prospectively explore their potential role in developing TIC. Only 3 patients (“case series”), who experienced TIC, were compared to 37 “control group” matched patients cardiotoxicity-sparing. All patients underwent to left ventricular ejection fraction (LVEF) evaluation at diagnosis and during anti-HER2 therapy. Each single probe was clustered to detect SNPs related to cardiotoxicity. ResultsIn this retrospective analysis, our 3 cases were homogeneous in terms of clinical-pathological characteristics, trastuzumab-based treatment and LVEF decline. We identified 9 polymorphic variants in 8 ADME genes (UGT1A1, UGT1A6, UGT1A7, UGT2B15, SLC22A1, CYP3A5, ABCC4, CYP2D6) potentially associated with TIC. ConclusionReal-world TIC incidence is higher compared to randomized clinical trials and biomarkers with potential predictive value aren’t available. Our preliminary data, as proof of concept, could suggest a predictive role of pharmacogenomic approach in the identification of cardiotoxicity risk biomarkers for anti-HER2 treatment.

Hormone Receptor-Positive/HER2-Positive Breast Cancer: Hormone Therapy and Anti-HER2 Treatment: An Update on Treatment Strategies.

Hormone receptor (HR)-positive/HER2-positive breast cancer represents a distinct subtype expressing estrogen and progesterone receptors with an overexpression of HER2. Approximately 14% of female breast cancer cases are HER2-positive, with the majority being HR-positive. These tumors show a cross-talk between the hormonal and HER2 pathways; the interaction has implications for the treatment options for the disease. In this review, we analyze the biology of HR-positive/HER2-positive breast cancer and summarize the evidence concerning the standard of care options both in neoadjuvant/adjuvant settings and in advanced disease. Additionally, we focus on new trials and drugs for HR-positive/HER2-positive breast cancer and the new entity: HER2-low breast cancer.

Abstract 6314: Potent inhibition of tumor relapse after anti-HER2 affibody tagged with cotinine (switch) plus anti-cotinine switchable CAR T cell therapy by repeated re-injection of the switch

Abstract Chimeric antigen receptor (CAR) T cells targeting CD19 or the B cell maturation antigen (BCMA) have demonstrated impressive initial clinical responses. However, on follow-up assessment, a notable fraction of the patients with significant initial clinical response eventually experienced relapse. CAR T cell therapies targeting solid tumors have shown an even lower rate of clinical response as well as shorter remission periods. A prior study has shown that re-injection of the anti-HER2 CAR T cells was effective in a rhabdomyosarcoma relapse patient (Cancer Res 79, LB147 (2019)), but the repeated production of CAR T cells is costly, thus raising questions about its feasibility in practice. Previously, we developed a cotinine-based CAR T cell system (zCART) comprised of a tumor antigen-specific affibody conjugated with cotinine and an anti-cotinine scFv CAR, and demonstrated the anti-tumor activity of an anti-HER2 zCART treatment in both in vitro and in vivo settings. In this study, we tested the efficacy of anti-HER2 zCART treatment in vivo using an intraperitoneal (IP) tumor model with a single infusion of zCART cells. The anti-HER2 switch was injected daily for 7 days. When the HER2 positive tumor relapsed, the mice were re-treated with the same dose of anti-HER2 switch treatment for an additional 7 days. We observed that re-injection of only the anti-HER2 switch and not combined with zCART cells effectively and potently inhibited relapse of HER2 positive tumors. Furthermore, the efficacy of the anti-HER2 switch re-injection treatment was maintained in one additional relapse. In summary, the zCART system has potential to treat cancer relapse following CAR T cell therapy without the need for an additional production round of CAR T cells. Citation Format: Ki Hyun Kim, Soohwan Kim, Eun-Hoe Lee, Soo-Yoon Lim, Sung Min Kim, E-Young Kim, Hyun-Jong Lee, Seong Yeol Kim, Min Yoon, Young-Ha Lee, In-Sik Hwang, Yoon Lee, Jong-Hoon Kim, Jong-Seo Lee, Junho Chung. Potent inhibition of tumor relapse after anti-HER2 affibody tagged with cotinine (switch) plus anti-cotinine switchable CAR T cell therapy by repeated re-injection of the switch [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6314.

Abstract 1711: Rearranged active enhancers and promoter-enhancer contacts promote lipid metabolic reprogramming during secondary trastuzumab adaptation of HER2 positive breast cancer

Abstract Background: The development of secondary trastuzumab resistance signifies an evolutionary adaptation within HER2-positive breast cancer during anti-HER2 treatment. Our research reveals a comprehensive metabolic reprogramming, with a particular emphasis on the synthesis of unsaturated fatty acids and the degradation of arachidonic acid, accompanying this adaptation. Non-mutational epigenetic variations, particularly alterations in active enhancers, coupled with the rearrangement of enhancer-promoter contacts, demonstrate robust correlations with lipid metabolic reprogramming. These findings suggest that non-mutational epigenetic variations play a crucial role in driving the adaptation to trastuzumab. Materials and Methods: In a prior investigation, we successfully generated secondary trastuzumab-resistant SKBR3_HR cells. In our current study, total RNA was extracted from both trastuzumab-resistant SKBR3_HR and trastuzumab-sensitive SKBR3 cells for transcriptome analysis. Additionally, mass spectrometry was employed to analyze cellular metabolism in both resistant and sensitive cell populations. Simultaneously, we utilized the CUT&Tag kit with an anti-H3K27ac antibody to create a sequencing library for active enhancer measurement. Furthermore, the Micro-C kit was applied to generate a sequencing library for genome contact measurement. Results: In our study, secondary trastuzumab-adaptive SKBR3_HR cells demonstrated a reduction in cellular unsaturated fatty acids, with more than 110 UFAs or UFA-containing lipids showing decreases, while only 36 exhibited increases. This phenomenon may be attributed to the downregulation of SCD, FADS2, and HACD2. Simultaneously, the upregulation of PTGS1 and PTGES may contribute to a higher conversion of arachidonic acid to prostaglandin E2 (PGE2), resulting in immune inhibition. In SKBR3 and SKBR3_HR cells, 10,955 and 10,889 non-promoter H3K27me3 peaks, respectively, were identified as active enhancer regions. Among them, 379 enhancers became silent, and 313 transitioned into an active state during the formation of trastuzumab adaptation. Trastuzumab adaptation led to an increase in intra-chromosomal interactions, particularly short-distance contacts (< 1MB). By employing the activity-by-contact (ABC) algorithm, we observed significant variant contacts between PTGES and SCD promoters and enhancers within 1MB genomic regions in SKBR3_HR cells compared to SKBR3 cells. Conclusion: The formation of secondary trastuzumab adaptation involves the rearrangement of active enhancers and promoter-enhancer contacts, serving as an effective force to drive lipid metabolic reprogramming, especially the synthesis of unsaturated fatty acids and PGE2 production, reshaping the cellular fatty acid composition and anti-tumor immunity. Citation Format: Ningjun Duan, Yijia Hua, Yongmei Yin. Rearranged active enhancers and promoter-enhancer contacts promote lipid metabolic reprogramming during secondary trastuzumab adaptation of HER2 positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1711.

Abstract 6981: p38-mediated EZH2 phosphorylation at T367 regulates HER2 pathway in triple negative breast cancer

Abstract Background: Triple negative breast carcinomas (TNBC) are highly aggressive tumors with limited effective treatments. Clinical studies showed that targeting low HER2 levels in TNBC with anti-HER2 agents has survival benefit. Enhancer of Zeste Homolog 2 (EZH2) is a lysine methyltransferase component of the Polycomb Repressive Complex2 that regulates differentiation genes in normal and neoplastic cells. EZH2 phosphorylation at T416 was shown to maintain the TNBC phenotype. We have reported that p38-induced EZH2-T367 phosphorylation enhances metastasis and that high pEZH2-T367 expression is significantly associated with human TNBC tumors compared to other breast cancer subtypes. In this study we tested the hypothesis that pEZH2-T367 may regulate the HER2 pathway in TNBC and that inhibition of pEZH2-T367 may upregulate HER2 signaling, with clinical implications. Methods: MDA-MB-231 (mesenchymal-like TNBC) and CCN6KO cells derived from MMTV-Cre;Ccn6fl/fl (CCN6KO) TNBC mouse model generated in our lab were transduced with vector or EZH2 shRNA knockdown (KD). MDA-MB-231 EZH2 KD cells were rescued with lentivirus containing EZH2-wild-type (WT) or T367A phosphorylation-deficient mutant. Gene and protein expression was analyzed by RNA sequencing, q-RT-PCR, immunoblot and immunohistochemistry. Vector and EZH2-KD rescue MDA-MB-231 cells were treated with anti-HER2 (trastuzumab or pertuzumab 100 ug/ml) followed by Hoestch proliferation assays. TNBC cells were treated with vehicle, EZH2 inhibitor (EPZ-6438, 20uM), p38 inhibitor (p38i, SB202190, 20uM), EPZ+p38i, anti-HER2 (100 ug/ml), and EPZ+p38i+anti-HER2, followed by Hoestch cell proliferation assays. Results: EZH2-T367A deregulates the expression of a 94-gene network of HER2 pathway genes including EREG, SERPINB5, MERTK, IL6R, SOCS3, and FASCN1 compared to EZH2-WT. EZH2-T367A increased protein levels of HER2, EREG, and PP2AB, a major HER2 regulator and was sufficient to sensitize TNBC cells to the anti-proliferative effects of anti-HER2. Supporting the role of pEZH2-T367, we found that the combination of p38i and EPZ significantly sensitizes TNBC cells to anti-HER2 therapies. Conclusions: We demonstrate that T367 phosphorylation mediates the effect of EZH2 on HER2 signaling in TNBC. Our data support a role for pEZH2-T367 in maintaining the HER2-negative phenotype in and suggest that blocking this phosphorylation event may render TNBC tumors amenable to anti-HER2 treatment strategies. Citation Format: Maria E. Gonzalez, Ahmad Eido, Celina G. Kleer. p38-mediated EZH2 phosphorylation at T367 regulates HER2 pathway in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6981.

HER2-Positive Early Breast Cancer: Time for Ultimate De-Escalation?

De-escalation is currently taking place in both the surgical and systemic treatment of breast cancer. The introduction of trastuzumab, the first monoclonal antibody against the HER2 receptor, over 20 years ago was a milestone in the treatment of HER2-positive breast cancer and marked the beginning of a new era in targeted tumor therapy. In the sense of de-escalation, omitting non-targeted cytotoxic chemotherapy altogether is often hailed as the ultimate goal of oncological research. Especially in cases of small, node-negative, HER2-positive early breast cancer, it remains a challenge for clinicians to establish the safest and most efficient treatment plan while considering the significant potential for toxic side effects associated with chemotherapy and HER2-targeted therapy, and the generally excellent prognosis. In this context, several ongoing studies are currently assessing chemotherapy-free regimens as part of strategies aimed at de-escalating therapy in the field of HER2-positive early breast cancer. Despite the promising early results of these studies, the combination of anti-HER2 treatment with a chemotherapy backbone remains the standard of care.

Unveiling Alterations of Epigenetic Modifications and Chromatin Architecture Leading to Lipid Metabolic Reprogramming during the Evolutionary Trastuzumab Adaptation of HER2-Positive Breast Cancer.

Secondary trastuzumab resistance represents an evolutionary adaptation of HER2-positive breast cancer during anti-HER2 treatment. Most current studies have tended to prioritize HER2 and its associated signaling pathways, often overlooking broader but seemingly less relevant cellular processes, along with their associated genetic and epigenetic mechanisms. Here, transcriptome data is not only characterized but also examined epigenomic and 3D genome architecture information in both trastuzumab-sensitive and secondary-resistant breast cancer cells. The findings reveal that the global metabolic reprogramming associated with trastuzumab resistance may stem from genome-wide alterations in both histone modifications and chromatin structure. Specifically, the transcriptional activities of key genes involved in lipid metabolism appear to be regulated by variant promoter H3K27me3 and H3K4me3 modifications, as well as promoter-enhancer interactions. These discoveries offer valuable insights into how cancer cells adapt to anti-tumor drugs and have the potential to impact future diagnostic and treatment strategies.

Elucidating molecular mechanisms and therapeutic synergy: irreversible HER2-TKI plus T-Dxd for enhanced anti-HER2 treatment of gastric cancer

BackgroundHER2-targeted therapies have improved the outcomes of HER2-positive gastric cancer (GC), yet resistance remains a challenge. We sought to explore the effects of reversible and irreversible HER2 tyrosine kinase inhibitors (TKIs) alone or in combination with the HER2-targeting antibody drug conjugate trastuzumab deruxtecan (T-Dxd).MethodsThe effects of HER2-TKIs on HER2 and downstream signaling were evaluated via Western blotting. Proteasomal inhibitors and co-immunoprecipitation assays were performed to explore the role of proteasomal degradation in HER2 expression modulation, and immunofluorescence assays were employed to explore mechanisms of HER2 internalization. The synergistic potential of the irreversible HER2-TKI pyrotinib in combination with T-Dxd was validated using growth and viability assays in anti-HER2-positive GC cell cultures and tumor growth and immunohistochemical staining assays in a mouse xenograft model.ResultsOur study revealed that reversible HER2-TKIs elevated HER2 protein levels, whereas irreversible HER2-TKIs decreased them. Pyrotinib triggered HER2 degradation within the proteasome by promoting ubiquitination and dissociation from HSP90. Furthermore, pyrotinib substantially induced HER2 internalization, which led to improved cellular uptake of T-Dxd. The increased T-Dxd uptake was accompanied by greater efficacy in suppressing the growth of GC cells and enhanced anti-tumor effects in an animal model.ConclusionIn summary, our research reveals the molecular mechanisms of irreversible HER2-TKIs in regulating HER2 protein expression by promoting HER2 internalization. These findings advance our comprehension of targeted therapy for GC and provide a promising therapeutic combination strategy with enhanced efficacy against HER2-positive GC.

Anti-HER2 therapy response assessment for guiding treatment (de-)escalation in early HER2-positive breast cancer using a novel deep learning radiomics model

ObjectivesAnti-HER2 targeted therapy significantly reduces risk of relapse in HER2 + breast cancer. New measures are needed for a precise risk stratification to guide (de-)escalation of anti-HER2 strategy.MethodsA total of 726 HER2 + cases who received no/single/dual anti-HER2 targeted therapies were split into three respective cohorts. A deep learning model (DeepTEPP) based on preoperative breast magnetic resonance (MR) was developed. Patients were scored and categorized into low-, moderate-, and high-risk groups. Recurrence-free survival (RFS) was compared in patients with different risk groups according to the anti-HER2 treatment they received, to validate the value of DeepTEPP in predicting treatment efficacy and guiding anti-HER2 strategy.ResultsDeepTEPP was capable of risk stratification and guiding anti-HER2 treatment strategy: DeepTEPP-Low patients (60.5%) did not derive significant RFS benefit from trastuzumab (p = 0.144), proposing an anti-HER2 de-escalation. DeepTEPP-Moderate patients (19.8%) significantly benefited from trastuzumab (p = 0.048), but did not obtain additional improvements from pertuzumab (p = 0.125). DeepTEPP-High patients (19.7%) significantly benefited from dual HER2 blockade (p = 0.045), suggesting an anti-HER2 escalation.ConclusionsDeepTEPP represents a pioneering MR-based deep learning model that enables the non-invasive prediction of adjuvant anti-HER2 effectiveness, thereby providing valuable guidance for anti-HER2 (de-)escalation strategies. DeepTEPP provides an important reference for choosing the appropriate individualized treatment in HER2 + breast cancer patients, warranting prospective validation.Clinical relevance statementWe built an MR-based deep learning model DeepTEPP, which enables the non-invasive prediction of adjuvant anti-HER2 effectiveness, thus guiding anti-HER2 (de-)escalation strategies in early HER2-positive breast cancer patients.Key Points• DeepTEPP is able to predict anti-HER2 effectiveness and to guide treatment (de-)escalation.• DeepTEPP demonstrated an impressive prognostic efficacy for recurrence-free survival and overall survival.• To our knowledge, this is one of the very few, also the largest study to test the efficacy of a deep learning model extracted from breast MR images on HER2-positive breast cancer survival and anti-HER2 therapy effectiveness prediction.

An Open-Label Study of Subcutaneous CpG Oligodeoxynucleotide (PF03512676) in Combination with Trastuzumab in Patients with Metastatic HER2+ Breast Cancer.

CpG ODN is a Toll-like receptor 9 agonist with immunotherapeutic potential for many cancer types, including aggressive breast cancers. There is strong interest in utilizing CpG ODN as an adjuvant to improve clinical efficacy of current treatments and immunogenicity of breast cancers not traditionally responsive to active immunotherapy, such as those that are human epidermal growth factor receptor 2 (HER2)-positive. This study aimed to study the efficacy and safety of combination CpG ODN plus anti-HER2 antibody trastuzumab treatment in patients with advanced/metastatic breast cancer. This single-arm, open-label phase II clinical trial treated patients (n = 6) with advanced/metastatic HER2-positive breast cancer with weekly subcutaneous CpG ODN and trastuzumab. Patients may have received any number of prior therapies to be enrolled (most enrolled at median 1 prior line of chemotherapy). Peripheral blood was collected at baseline and weeks 2, 6, 12, and 18 for immune analyses. Six patients were enrolled and 50% achieved stable disease (SD) response. Median PFS was 8.3 months. Three of the six patients enrolled opted to stop treatment due to tolerability issues. Multiplex assay for cytokine measurements revealed significantly higher VEGF-D levels at week 2 compared to baseline. Peripheral blood mononuclear cells analyzed by flow cytometry showed a significant increase in monocytic MDSC between weeks 6 and 12. Patients with progressive disease tended to have higher levels of week 6 monocytic MDSC and PD-1+ T cells than patients with SD. NK cell populations did not significantly change throughout treatment. CpG ODN and trastuzumab treatment of metastatic HER2 + breast cancer was safe but was not tolerable for all patients. This combination did induce potentially predictive immune profile changes in treated patients with metastatic HER2 + breast cancer, the significance of which needs to be further explored.

NK cell-triggered CCL5/IFNγ-CXCL9/10 axis underlies the clinical efficacy of neoadjuvant anti-HER2 antibodies in breast cancer

BackgroundThe variability in responses to neoadjuvant treatment with anti-HER2 antibodies prompts to personalized clinical management and the development of innovative treatment strategies. Tumor-infiltrating Natural Killer (TI-NK) cells can predict the efficacy of HER2-targeted antibodies independently from clinicopathological factors in primary HER2-positive breast cancer patients. Understanding the mechanism/s underlying this association would contribute to optimizing patient stratification and provide the rationale for combinatorial approaches with immunotherapy.MethodsWe sought to uncover processes enriched in NK cell-infiltrated tumors as compared to NK cell-desert tumors by microarray analysis. Findings were validated in clinical trial-derived transcriptomic data. In vitro and in vivo preclinical models were used for mechanistic studies. Findings were analysed in clinical samples (tumor and serum) from breast cancer patients.ResultsNK cell-infiltrated tumors were enriched in CCL5/IFNG-CXCL9/10 transcripts. In multivariate logistic regression analysis, IFNG levels underlie the association between TI-NK cells and pathological complete response to neoadjuvant treatment with trastuzumab. Mechanistically, the production of IFN-ɣ by CD16+ NK cells triggered the secretion of CXCL9/10 from cancer cells. This effect was associated to tumor growth control and the conversion of CD16 into CD16-CD103+ NK cells in humanized in vivo models. In human breast tumors, the CD16 and CD103 markers identified lineage-related NK cell subpopulations capable of producing CCL5 and IFN-ɣ, which correlated with tissue-resident CD8+ T cells. Finally, an early increase in serum CCL5/CXCL9 levels identified patients with NK cell-rich tumors showing good responses to anti-HER2 antibody-based neoadjuvant treatment.ConclusionsThis study identifies specialized NK cell subsets as the source of IFN-ɣ influencing the clinical efficacy of anti-HER2 antibodies. It also reveals the potential of serum CCL5/CXCL9 as biomarkers for identifying patients with NK cell-rich tumors and favorable responses to anti-HER2 antibody-based neoadjuvant treatment.

Pyrotinib is effective in both trastuzumab-sensitive and primary resistant HER2-positive breast tumors.

Primary resistance to trastuzumab frequently occurs in human epidermal growth factor receptor 2 (HER2)-positive (+) breast cancer patients and remains a clinical challenge. Pyrotinib is a novel tyrosine kinase inhibitor that has shown efficacy in the treatment of HER2+ breast cancer. However, the efficacy of pyrotinib in HER2+ breast cancer with primary trastuzumab resistance is unknown. HER2+ breast cancer cells sensitive or primarily resistant to trastuzumab were treated with trastuzumab, pyrotinib, or the combination. Cell proliferation, migration, invasion, and HER2 downstream signal pathways were analyzed. The effects of pyrotinib plus trastuzumab and pertuzumab plus trastuzumab were compared in breast cancer cells in vitro and a xenograft mouse model with primary resistance to trastuzumab. Pyrotinib had a therapeutic effect on trastuzumab-sensitive HER2+ breast cancer cells by inhibiting phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) and rat sarcoma virus (RAS)/rapidly accelerated fibrosarcoma (RAF)/mitogen-activated protein kinase (MAPK)/extracellular-signal regulated kinase (ERK) pathways. In primary trastuzumab-resistant cells, pyrotinib inhibited cell growth, migration, invasion, and HER2 downstream pathways, whereas trastuzumab had no effects. The combination with trastuzumab did not show increased effects compared with pyrotinib alone. Compared with pertuzumab plus trastuzumab, pyrotinib plus trastuzumab was more effective in inhibiting cell proliferation and HER2 downstream pathways in breast cancer cells and tumor growth in a trastuzumab-resistant HER2+ breast cancer xenograft model. Pyrotinib-containing treatments exhibited anti-cancer effects in HER2+ breast cancer cells sensitive and with primary resistance to trastuzumab. Notably, pyrotinib plus trastuzumab was more effective than trastuzumab plus pertuzumab in inhibiting tumor growth and HER2 downstream pathways in HER2+ breast cancer with primary resistance to trastuzumab. These findings support clinical testing of the therapeutic efficacy of dual anti-HER2 treatment combining an intracellular small molecule with an extracellular antibody.

The tumor immune microenvironment remodeling and response to HER2-targeted therapy in HER2-positive advanced gastric cancer.

Combination therapy with anti-HER2 agents and immunotherapy has demonstrated significant clinical benefits in gastric cancer (GC), but the underlying mechanism remains unclear. In this study, we used multiplex immunohistochemistry to assess the changes of the tumor microenvironment in 47 advanced GC patients receiving anti-HER2 therapy. Additionally, we performed single-cell transcriptional sequencing to investigate potential cell-to-cell communication and molecular mechanisms in four HER2-positive GC baseline samples. We observed that post-treated the infiltration of NK cells, CD8+ T cells, and B lymphocytes were significantly higher in patients who benefited from anti-HER2 treatment than baseline. Further spatial distribution analysis demonstrated that the interaction scores between NK cells and CD8+ T cells, B lymphocytes and M2 macrophages, B lymphocytes and Tregs were also significantly higher in benefited patients. Cell-cell communication analysis from scRNA sequencing showed that NK cells utilized CCL3/CCL4-CCR5 to recruit CD8+ T cell infiltration. B lymphocytes employed CD74-APP/COPA/MIF to interact with M2 macrophages, and utilized TNF-FAS/ICOS/TNFRSR1B to interact with Tregs. These cell-cell interactions contribute to inhibit the immune resistance of M2 macrophages and Tregs. Our research provides potential guidance for the use of anti-HER2 therapy in combination with immune therapy.