Search

Background: Varying levels of HER2 expression without ERBB2 gene amplification can be detected by immunohistochemistry (IHC) in approximately 60% of all invasive breast cancers (BCs). HER2-low-expressing BCs have recently been shown to respond to novel anti-HER2 antibody drug conjugates. Several studies have demonstrated that HER2-low BCs do not seem to constitute a distinct clinical and transcriptomic subtype as compared to HER2-0 BCs. Here we sought to define the clinicopathologic features and repertoire of somatic genetic alterations in HER2-low BCs. Methods: We retrieved clinical, pathological, and genomic data of BCs that were subjected to targeted sequencing using the FDA-cleared MSK-IMPACT assay from April 2014 to December 2021. After removing cases where any available biopsy had HER2 3+ and/or positive ERBB2 fluorescence in situ hybridization (FISH), 3608 samples (primary=1347; post-treatment/metastatic=2261) were included. Tumors were classified as HER2-low if they had an HER2 IHC score of 1+ or 2+ with a non-amplified FISH assay and HER2-0 if they had an HER2 IHC score of 0. Somatic mutations and DNA copy number alterations from MSK-IMPACT were analyzed. Multiple testing correction using the Benjamini-Hochberg method was applied to control for the false discovery rate (q). Q values < 0.1 were considered significant. Results: Among 3608 HER2- BCs, 1460 (40%) and 2148 (60%) were HER2-0 and HER2-low, respectively. Hormone receptor (HR) expression was significantly higher in HER2-low than HER2-0 tumors in both primary (781 [68.3%] vs 362 [31.7%]; p< 0.001) and metastatic (1031 [60.5%] vs 673 [39.5%]; p< 0.001) samples. A higher proportion of HER2-low tumors was found in metastatic than primary samples (59% vs 41%; p< 0.001) in this cohort. No difference in histology subtype, tumor grade, disease stage (among primary tumors), mutational signatures, and tumor mutational burden was found overall and when cases were stratified by HR expression. In HR-positive BCs, HER2-0 BCs harbored higher frequency of TP53 (33% vs 25%; odds ratio [OR] 1.49, 95% confidence interval [CI] 1.25-1.78, q< 0.001) and CDKN1A (1% vs 0%; OR 17.47, 95% CI 2.48-756.37, q=0.02) alterations than HER2-low BCs. Similar findings were observed in metastatic but not in primary HR-positive BCs. No differences were detected in HR-negative BCs stratified into HER2-low and HER2-0. Given the potential misclassification that exists between IHC HER2-0 and HER2-1+, we then conducted an exploratory analysis splitting the HER2-low group into HER2 1+ and 2+. TP53 alterations remained significantly enriched in HER2-0 compared to HER2-1+ HR-positive tumors (33% vs 24%; OR 1.55, 95% CI 1.28-1.87, q< 0.001). In HR-positive BCs, HER2-2+ displayed a higher frequency of genetic alterations in genes encoding for transcription factors, such as MYC (14.2% vs 7.3%; OR 2.09, 95% CI 1.44-3.04, q=0.02) and YAP1 (2% vs 0.3%; OR 6.86, 95% CI 1.7-39.57, q=0.1), and DNA damage response, such as FAM175A (1.6% vs 0%; OR 18.23, 95% CI 2.43-807.73, q=0.03) and BRCA2 (4% vs 1%; OR 3.09, 95% CI 1.49-6.55, q=0.1), than HER2-0 tumors. In HR-negative HER2-2+ tumors, a higher frequency of PIK3CA mutations was observed in comparison to HER2-0 (36.9% vs 19.5%; OR 2.41, 1.4-4.1, q=0.1), overall and in the metastatic setting. Conclusions: HER2-low BCs seem not to represent a distinct pathologic subtype. At the genomic level, however, some differences were identified and these became more conspicuous upon subclassification of HER2 IHC expression into 1+ and 2+. Further investigation into methods that more accurately detect and quantify low levels of HER2 expression in BC samples as well as better characterize the biology behind the HER2-low/ultralow expression is warranted. Citation Format: Antonio Marra, Anton Safonov, Joshua Drago, Emanuela Ferraro, Pier Selenica, Andrea Gazzo, Giuseppe Curigliano, Shanu Modi, Pedram Razavi, Jorge Reis-Filho, Sarat Chandarlapaty. HER2-07 Genomic Characterization of Primary and Metastatic HER2-low Breast Cancers [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr HER2-07.

Background In DESTINY-Breast04, the HER2-targeted antibody drug conjugate trastuzumab deruxtecan (T-DXd) demonstrated significant survival benefit vs treatment of physician’s choice (TPC) in patients (pts) with HER2-low unresectable or metastatic breast cancer (mBC) (Modi et al. N Engl J Med 2022). These results emphasize the importance of accurately identifying HER2 expression in breast tumor tissue. Here, we describe concordance between previously determined (historical) HER2 scores and central HER2 scores, and tumor sample characteristics for pts with mBC screened and enrolled in DESTINY-Breast04. Methods DESTINY-Breast04 was a randomized, open-label, phase 3 study in pts with centrally determined HER2-low (immunohistochemistry [IHC] 1+ or IHC 2+ with negative in situ hybridization [ISH]) mBC who had previously received 1-2 lines of chemotherapy. Pts were randomized 2:1 to T-DXd or TPC. HER2 scores were determined via central testing of tumor specimens by the investigational Ventana PATHWAY 4B5 IHC assay, using the 2018 American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) testing guidelines HER2 scoring algorithm, and Ventana INFORM HER2 dual ISH assay (as applicable). Results 1340 pts identified as having HER2-low mBC per historical data submitted tumor samples for central HER2-low testing. Of those, 557 pts met all eligibility criteria and were enrolled in DESTINY-Breast04. The proportion of samples from metastatic vs primary tumors was 59% vs 41% for all submitted tumor samples and 65% vs 35% for enrolled patients. Of those with available data, most were biopsy specimens (995 [74%] vs 344 [26%] resection/excisions) and were submitted as archived formalin-fixed, paraffin-embedded tissue (1183 [88%] vs 157 [12%] freshly collected samples); historical testing dates ranged from 2000-2020. Of samples with data on the historical HER2 IHC test used (31%), most were scored using local Ventana 4B5 (63%) or Agilent HercepTest (32%) assays. Tumor distribution characteristics were similar between screened and enrolled pts. For samples with historical and central HER2 results (N = 1108), 849/1108 (77%) were centrally scored as HER2-low. Of the samples that were not centrally scored as HER2-low, 88% were scored as HER2 IHC 0. Historical and central HER2 score concordance was assessed by sample region of origin (North America, Europe, China, or Asia without China) and collection date (2013 or earlier, 2104-2018, or 2019 or after) and scoring agreement was associated with these factors. Efficacy of T-DXd vs TPC for pts in DESTINY-Breast04 was consistent across all tumor sample characteristics (primary vs metastatic, specimen type, archival vs fresh, and tissue collection date). Conclusions Despite the lack of prior clinical utility and training in distinguishing HER2 IHC 0 from HER2-low (IHC 1+, 2+/ISH–), evolving guidelines since historical HER2 status provision, differences in local testing methods, and differences in key sample characteristics (primary vs metastatic; archived vs fresh; widely variable sample biopsy and testing dates), there was a 77% agreement between historical and central HER2-low status using the Ventana PATHWAY 4B5 IHC assay and Ventana INFORM HER2 Dual ISH assay. This rate is comparable to the reported initial concordance rates for HER2 overexpression IHC testing (range 74-82%; Roche J. Natl Cancer Inst 2002, Perez. J Clin Oncol 2006). Moreover, consistent benefit of T-DXd vs TPC was generally seen across patient groups with various tumor sample characteristics in DESTINY-Breast04. Determination of HER2-low status using the Ventana PATHWAY 4B5 IHC assay (and ISH when applicable) demonstrated the ability of the test, analyzed by pathologists using current ASCO/CAP guidelines, to identify pts who benefit from T-DXd. Funding This study was funded by Daiichi Sankyo and AstraZeneca. Citation Format: Aleix Prat, Shanu Modi, Junji Tsurutani, David Cameron, Nadia Harbeck, Charo Garrido, Maha Karnoub, Ching Hsu, Wenquin Feng, Lotus Yung, Yibin Wang, Dhiraj Gambhire, Shirin K. Ford, Patrik Vitazka, Naoto T. Ueno. HER2-18 Determination of HER2-low status in tumors of patients with unresectable and/or metastatic breast cancer in DESTINY-Breast04 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr HER2-18.

Background: DESTINY-Breast04 demonstrated that the HER2 targeting antibody–drug conjugate trastuzumab deruxtecan (T-DXd) significantly prolonged progression-free survival (PFS) and overall survival (OS) vs treatment of physician’s choice (TPC) in patients (pts) with HER2-low (immunohistochemistry [IHC] 1+ or IHC 2+/in situ hybridization negative) metastatic breast cancer (mBC) in pts in the hormone receptor−positive (HR+) cohort and all pts (HR+ and HR-; median PFS, 9.9 vs 5.1 months [mo], hazard ratio: 0.50; median OS, 23.4 vs 16.8 mo, hazard ratio: 0.64; both P < 0.0001; Modi et al. N Engl J Med 2022). Objective response rate (ORR) with T-DXd was ≥50% across cohorts. These subgroup analyses examine pt history and disease characteristics that may correlate with response to therapy. Methods: N = 557 pts with centrally confirmed HER2-low mBC were randomized 2:1 to T-DXd or TPC. Randomization was stratified by HER2 status (IHC 1+ vs 2+), 1 vs 2 prior lines of chemotherapy, and HR+ (with vs without prior treatment with cyclin-dependent kinase 4/6 inhibitor [CDK4/6i]) vs HR−. With the exception of the PFS and OS analyses by prior CDK4/6i use, all other described efficacy analyses were assessed post-hoc. Results: Benefit of T-DXd vs TPC was consistent in pts with or without prior CDK4/6i use (Table 1). Pts with high disease burden (ie, ≥3 metastatic sites) also benefited from T-DXd vs TPC (Table 2). There was a small subgroup (n = 22) among all pts (HR+ [n = 18] and HR− disease [n = 4]) with rapid progression prior to enrollment (disease progression within 6 mo of concluding a prior course of chemotherapy in early breast cancer). T-DXd showed responses in 7/14 (50%) pts in this subgroup vs 0/8 with TPC; this subgroup also had prolonged median PFS with T-DXd vs TPC (Table 3). Efficacy data for HER2 IHC 1+ vs 2+ and prior chemotherapy subgroups will be presented. Median OS was not reached for many subgroups (insufficient events in each group [data not shown]); however, subgroups in general showed OS benefit consistent with the primary analysis. With T-DXd, rates of interstitial lung disease/pneumonitis were similar in pts with/without prior CDK4/6i use. Conclusions: T-DXd treatment for HER2-low mBC in the phase 3 study DESTINY-Breast04 showed consistent efficacy independent of disease burden, prior CDK4/6i treatment, or rapid progression status. ILD is an important identified risk and requires proactive monitoring and management. These data continue to support the use of T-DXd as the new standard of care across subgroups of pts with HER2-low mBC. Editorial Acknowledgment Under guidance of the authors, assistance in medical writing and editorial support was provided by Eileen McIver, PhD, and Soniya Patel, PhD, of ApotheCom, and was funded by Daiichi Sankyo. Funding This study was funded by Daiichi Sankyo and AstraZeneca. Table 1. Efficacy by Prior CDK4/6i Treatment in Pts With HER2-Low Breast Cancer, HR+ Cohort. Table 2. Efficacy by Disease Burdena in Pts With HER2-Low Breast Cancer, ITT. Table 3. Efficacy by Rapid Progressor Statusa in Pts With HER2-Low Breast Cancer, ITT. Citation Format: Nadia Harbeck, Shanu Modi, William Jacot, Toshinari Yamashita, Joo Hyuk Sohn, Maria Vidal, Junji Tsurutani, Naoto T. Ueno, Aleix Prat, Naoki Niikura, Binghe Xu, Hope Rugo, Konstantinos Papazisis, Javier Cortés, Ian Krop, Dhiraj Gambhire, Lotus Yung, Yibin Wang, Jasmeet Singh, David Cameron. Trastuzumab deruxtecan vs treatment of physician’s choice in patients with HER2-low unresectable and/or metastatic breast cancer: Subgroup analyses from DESTINY-Breast04 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-11-01.

Purpose The combination of trastuzumab and pertuzumab (HP) as part of a taxane-based regimen has shown benefit in the adjuvant and metastatic HER2+ breast cancer setting. In the CLEOPATRA trial, pruritus was reported in 11-17.6% of patients. The clinical phenotype and potential treatment strategies for this event have not been reported. Methods A retrospective review of 2583 patients receiving trastuzumab and pertuzumab for the treatment of HER2+ breast cancer from 11/23/2011 to 6/21/2021 was performed at Memorial Sloan Kettering Cancer Center (MSKCC). Patient demographics, pruritus characteristics, and treatments as documented in the electronic medical record (EMR) were included in this analysis. Results Of 2583 pts treated with HP, 122 (4.72%) with pruritus were identified. On average, patients experienced pruritus 319.0 days (8-3171) after initiation of HP. The upper extremities (67.4%), back (29.3%), lower extremities (17.4%), and shoulders (14.1%) were the most commonly affected regions. Grade 1/2 pruritus (97.6%) occurred in most cases. Patients responded primarily to treatment with topical steroids (52.2%), antihistamines (29.9%), emollients (20.9%), and gabapentinoids (16.4%). Of those with pruritus, 4 patients (3.3%) required treatment interruption or discontinuation. Conclusions Pruritus is uncommon in patients on trastuzumab and pertuzumab, generally a chronic condition, with gabapentinoids or antihistamines representing effective therapies.

DESTINY-Breast01 (NCT03248492) evaluated trastuzumab deruxtecan (T-DXd; DS-8201) in patients with heavily pretreated HER2-positive metastatic breast cancer (mBC). We present a subgroup of 24 patients with a history of treated brain metastases (BM), a population with limited treatment options. In patients with BMs, the confirmed objective response rate (cORR) was 58.3% [95% confidence interval (CI), 36.6%–77.9%], and the median progression-free survival (mPFS) was 18.1 months (95% CI, 6.7–18.1 months). In patients without BMs (n = 160), cORR was 61.3% and mPFS was 16.4 months. Eight patients (47.1%) experienced a best overall intracranial response of partial response or complete response. Seven patients (41.2%) had a best percentage change in brain lesion diameter from baseline consistent with stable disease. Two patients (8.3%) with BMs and two (1.3%) without BMs experienced progression in the brain. The safety profile of T-DXd was consistent with previous studies. The durable clinical activity of T-DXd in this population warrants further investigation.Significance:Advances in treating HER2-positive metastatic breast cancer have greatly improved patient outcomes, but intracranial progression remains an important risk for which few therapeutic options are currently available. T-DXd demonstrated durable efficacy in patients with stable, treated BMs.This article is highlighted in the In This Issue feature, p. 2711

Supplementary Data from Trastuzumab Deruxtecan in HER2-Positive Metastatic Breast Cancer Patients with Brain Metastases: A DESTINY-Breast01 Subgroup Analysis

PDF file - 76K, Additional Patient Characteristics.

Supplemental Tables

Malignant pleural diseases, comprising metastatic lung and breast cancers and malignant pleural mesothelioma (MPM), are aggressive solid tumors with poor therapeutic response. We developed and conducted a first-in-human, phase I study of regionally delivered, autologous, mesothelin-targeted chimeric antigen receptor (CAR) T-cell therapy. Intrapleural administration of 0.3M to 60M CAR T cells/kg in 27 patients (25 with MPM) was safe and well tolerated. CAR T cells were detected in peripheral blood for >100 days in 39% of patients. Following our demonstration that PD-1 blockade enhances CAR T-cell function in mice, 18 patients with MPM also received pembrolizumab safely. Among those patients, median overall survival from CAR T-cell infusion was 23.9 months (1-year overall survival, 83%). Stable disease was sustained for ≥6 months in 8 patients; 2 exhibited complete metabolic response on PET scan. Combination immunotherapy with CAR T cells and PD-1 blockade agents should be further evaluated in patients with solid tumors.Significance:Regional delivery of mesothelin-targeted CAR T-cell therapy followed by pembrolizumab administration is feasible, safe, and demonstrates evidence of antitumor efficacy in patients with malignant pleural diseases. Our data support the investigation of combination immunotherapy with CAR T cells and PD-1 blockade agents in solid tumors.See related commentary by Aldea et al., p. 2674.This article is highlighted in the In This Issue feature, p. 2659

Supplementary Data from Increased Levels of Urinary PGE-M, a Biomarker of Inflammation, Occur in Association with Obesity, Aging, and Lung Metastases in Patients with Breast Cancer

Supplemental Figures

Supplemental Material

Background: Membrane HER2 expression levels strongly influence the activity of anti-HER2 therapies directed at the HER2 extracellular domain (1,2). Tumoral cell-surface caveolin-1 (CAV-1) regulates receptor tyrosine kinase membrane trafficking mechanisms (1,3). In xenograft models, CAV-1 can be modulated with cholesterol-depleting drugs, such as statins. We hypothesized that preclinical and clinical use of statins might influence the expression of CAV-1 and thereby affect the efficacy of anti-HER2 antibody-drug conjugates (ADCs) in breast cancer. Methods: Preclinically, statins were given alone and in combination with HER2 antibody drug conjugates such as T-DM1 to assess HER2 levels, drug uptake, and antitumor efficacy in HER2-positive cancer models. Mice received an intravenous injection of T-DM1, oral doses of lovastatin, or a combination of T-DM1 and lovastatin, for 5 weeks. Clinically, we performed retrospective analyses of HER2-positive MBC patients at MSKCC who received T-DM1 and consented to molecular profiling and clinical data abstraction. Progression-free survival (PFS) on T-DM1 was estimated using Kaplan Meyer methods and compared using the log rank test. Univariable and multivariable Cox proportional hazards models were constructed using relevant clinical covariates. Results: Tumor models with high levels of CAV-1 exhibit low HER2 density on the cell surface and show low T-DM1 targeted immunoPET binding when compared with CAV-1-low tumors. Mechanistic studies showed that CAV-1 depletion in HER2-positive BC cells temporally stabilizes HER2 on the surface and delays T-DM1 recycling. In preclinical BC models, CAV-1 depletion induced by synthetic oligonucleotides or statins enhances T-DM1 binding and efficacy in tumors with incomplete HER2 membranous reactivity. For clinical analyses, a total of 164 patients who received T-DM1 were included in the final analysis. Twenty-one (12.8%) of these patients were recorded to be taking statins concurrently with T-DM1, as part of their routine clinical care. Compared with patients with no recorded statin use, patients receiving statins were older on average (median age 58 vs. 50 years, p = 0.007), but did not differ in their race, histologic breast cancer type, ER status, or T-DM1 treatment line. Median PFS on T-DM1 in the overall cohort was 5.5 months. Median PFS in patients who received statins was 14 months vs. 5.4 months in patients who had no recorded statin use (p = 0.1). In univariable Cox analysis, the association between statin use and PFS did not reach statistical significance (p=0.119). In a multivariable analysis including age, ER status, treatment line, and breast cancer histology, no variable reached statistical significance. However, statin use had the greatest observed degree of association with PFS (p = 0.17). Conclusions: Statins modulate surface HER2 levels and T-DM1 efficacy preclinically via CAV-1. Although only a numerical difference in outcomes was observed in the MSKCC cohort, the effect appeared meaningful and therefore assessment in larger patient cohorts is now underway. Based on the results of these forthcoming analyses, prospective trials may be justified that integrate these well-tolerated and low-cost agents into HER2 ADC treatment regimens. References:1-Pereira P. et al Nat Commun 9, 5137 (2018)2-Chew H.Y. et al Cell 180, 895 (2020)3-Pereira P. et al Clin Cancer Res 26, 6215 (2020) Citation Format: Joshua Z Drago, Patricia R Pereira, Anton Safonov, Antonio Marra, Yi Rao, Bo Liu, Mehnaj Ahmed, Shanu Modi, Jorge Reis-Filho, Mark Robson, Filippo Montemurro, Pedram Razavi, Jason S Lewis, Sarat Chandarlapaty. Statin modulation of antibody drug conjugate activity in breast cancer models and patients [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-19.

Background: Chemotherapy remains the mainstay of treatment for early-stage triple negative breast cancer (TNBC), yet targetable drivers of interest are under investigation. A subset of TNBCs express the androgen receptor (AR) and exhibit androgen-dependent growth. The AR-antagonist enzalutamide (ENZA) has shown activity in patients with metastatic AR+ TNBC. In this study, the feasibility of adjuvant ENZA in early-stage, AR+ TNBC was assessed (NCT02750358). As reported previously, this study met its primary endpoint of feasibility (Traina et al., ASCO 2019). Here we report secondary survival endpoints. Methods: In this single-arm, open-label, multi-center trial, patients with stage I-III, AR≥1% TNBC (ER/PR Citation Format: Elaine M Walsh, Ayca Gucalp, Sujata Patil, Marcia Edelweiss, Dara S Ross, Pedram Razavi, Shanu Modi, Neil M Iyengar, Rachel Sanford, Tiffany Troso-Sandoval, Mila Gorsky, Jackie Bromberg, Pamela Drullinsky, Diana Lake, Serena Wong, Patricia DeFusco, Nicholas Lamparella, Ranja Gupta, Tasmila Tabassum, Leigh Ann Boyle, Artavazd Arumov, Tiffany A Traina. Adjuvant enzalutamide for the treatment of early-stage androgen-receptor positive, triple negative breast cancer: A feasibility study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-14-03.

Background: Despite the success of multiple HER2-targeted agents in HER2+ breast cancer (BC), resistance remains a challenge and novel therapies are needed. DHES0815A is a THIOMABTM antibody-drug conjugate consisting of a humanized IgG1 anti-HER2 monoclonal antibody (mAb) conjugated to the DNA alkylating agent PBD-MA. The reduced potency of PBD-MA compared to PBD dimers and the stability of the conjugation site and linker were designed to improve tolerability, whereas the binding of the mAb to a HER2 epitope distinct from trastuzumab and pertuzumab was designed to enable combination therapy with existing HER2 therapies. Methods: This first-in-human, Phase I, open-label, multicenter, dose escalation study used a 3+3 dose escalation design to assess the safety, pharmacokinetics (PK), and preliminary anti-tumor activity of DHES0815A in patients with metastatic HER2-positive BC refractory to established therapies (NCT03451162). DHES0815A (0.6-6.0 mg/kg) was administered intravenously every 3 weeks (Q3W) until intolerable toxicity or disease progression. Results: A total of 14 patients were treated with DHES0815A; all had ≥3 prior lines of therapy. Thirteen patients discontinued treatment due to progressive disease (43%), adverse events (AE; [29%]) symptomatic deterioration (14%) or other (7%); 1 patient remains on treatment. DHES0815A was initially well-tolerated for doses up to 2.4 mg/kg. At 4.0 mg/kg and 6.0 mg/kg, the first dose was also well-tolerated with no dose limiting toxicities, however, following 3 or more cycles at 4.0 mg/kg or 2 or more cycles at 6.0 mg/kg, safety events involving skin, eyes, and lung emerged. Skin events were reported in 50% of patients (all doses) and related events occurring in n≥2 patients included pruritus (36%), rash (36%), and skin hyperpigmentation (21%). Ocular toxicities were reported in 57% and related events occurring in n≥2 patients included photophobia (21%), conjunctivitis, eye pain, and dry eye (each 14%). Lung toxicities were reported in 36% of patients; events occurring in n≥2 included pneumonitis (14%). Other related skin, ocular, and pulmonary events occurring in 1 patient (7%) included palmar-plantar erythrodysaesthesia, macular rash, blurred vision, eyelid edema, periorbital edema, blepharitis, punctate keratitis, wheezing, allergic rhinitis, and pneumothorax. Most events were grade 1 or 2 although 3 patients experienced grade 3 ocular events (blepharitis, eye pain, photophobia). Due to these AEs, DHES0815A dose was decreased to 2.4 mg/kg Q3W for all enrolled patients and accrual was stopped. All 5 patients receiving doses of 4.0 mg/kg and 6.0 mg/kg discontinued due to AEs. At lower doses, 1 patient receiving 2.4 mg/kg developed grade 2 rash at Cycle 21 and 1 patient receiving 1.2 mg/kg developed grade 1 rash, pruritis, and skin hyperpigmentation between Cycles 28-30. Nonlinear PK of antibody-conjugated PBD-MA (acPBD-MA) was observed due to target mediated drug disposition at 0.6, 1.2, and 2.4 mg/kg; PK approached linear at 4.0 mg/kg. Minimal systemic exposure of unconjugated PBD-MA was observed. Overall, 1 patient (7%) in the 1.2 mg/kg cohort achieved a confirmed complete response. As of 10Jun21, this patient remains on study after more than 32 months on treatment. Ten patients (86%) showed a confirmed best overall response of stable disease (86%). Conclusion: Despite some anti-tumor activity observed with DHES0815A, development in HER2-positive BC has been discontinued due to safety concerns and the narrow therapeutic window. Toxicities observed in skin, lung, and eyes are clinically apparent only after repeated dose administration. If future exploration of PBD-MA-based constructs is performed in the clinic, close monitoring for delayed toxicities is warranted. Citation Format: Ian Krop, Erika Hamilton, Kyung Hae Jung, Shanu Modi, Kevin M Kalinsky, Gail Phillips, Rong Shi, Sharareh Monemi, Michael Mamounas, Ola Saad, Voleak Choeurng, Renee Commerford, Eunpi Cho, Alexander Ungewickell, Patricia LoRusso. A phase I dose-escalation study of DHES0815A, a HER2-targeting antibody-drug conjugate with a DNA monoalkylator payload, in patients with HER2-positive breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-25.

Background: Patients with early HER2-positive breast cancer (BC) and residual disease after HER2-targeted neoadjuvant chemotherapy (NAC) are at high risk of recurrence. It is estimated that 10-30% of HER2-positive breast cancers change HER2 status after trastuzumab alone, but the effects of adding pertuzumab on this phenomenon and clinical outcomes remain unclear. We previously reported a high rate (~50%) of HER2 status change after HP in a small subset of patients. Herein, we present an updated analysis incorporating pathological review of additional cases.Methods: We identified patients with HER2-positive BC who received NAC with pertuzumab and trastuzumab (NAC-HP) followed by surgery at our institution between September 1, 2013 to November 1, 2019. Patients with HER2 status performed either at MSKCC or outside institutions were included. Change in HER2 status on residual disease from baseline was evaluated. We defined HER2 positivity as immunohistochemistry (IHC) IHC3+ or IHC0-2+ FISH amplified (ratio ≥ 2 or ratio < 2 and HER2 copy number ≥ 6 signals/cell). HER2-low was defined as IHC 1+ or 2+, FISH non-amplified. Disease free survival (DFS) and overall survival (OS) were analyzed using the Kaplan-Meier method. Differences between patients with concordant and discordance HER2 status were assessed using the log-rank test.Results: Of 525 patients receiving NAC with HP, 229 (44%) patients had residual disease post NAC-HP. Among these 229 patients, 141 had both pre and post NAC-HP HER2 status available and were included in this analysis. HER2 status on biopsy specimens was determined at MSKCC in 35/141 (25%) and at external institution in 106/141 (75%). The majority of patients (84%) received dose-dense AC-THP; the remainder received TCHP or other HP-based regimens. Most (96%) of patients continued HP after surgery, and 2 patients received T-DM1. Of the 141 patients, 84/141(60%) were found to be HER2 concordant, while 57 (40%) were found to be HER2 discordant. In 13/57 (23%) patients, HER2 expression was lost (IHC 0), while in 44/57 (77%) patients, HER2-low profile was detected (IHC 1+ in 31, and IHC 2+, FISH non-amplified in 13). Further details are reported in the table. Patients with HER2 discordance after NAC-HP had similar survival outcome compared with patients who remained HER2 concordant (5-years DFS: 92.3% versus 88.7%, p=0.49 and 5-yr OS 93.6% versus 88.4%, p=0.70).Conclusions: In a single center cohort, discordant HER2 status after NAC-HP appeared frequently without statistically significant impact on survival outcome, although this finding may be due to the small size and hence low statistical power. Of these, HER2-low profile is the most frequent post treatment HER2 status change. This raises the possibility that patients with change in HER2 status may have heterogenous expression of HER2 at baseline, and HER2-loss or low sub-clones survive as residual disease due to the selection pressure of HP. Alternatively, anti-HER2 therapy may suppress HER2 expression in surviving cells. These findings could inform studies of tailored approaches in the post-neoadjuvant setting based on the biological profile of residual disease. Pre NAC-HP HER2 statusNPost NAC-HP HER2 statusNDiscordantN=57IHC 3+: 19IHC0: 4IHC1+: 9IHC2+ FISH not ampl: 6IHC 0-2+ FISH ampl: 38IHC0: 9IHC1+: 22IHC2+ FISH not ampl: 7Concordant N= 84IHC 3+: 59IHC 3+: 47IHC 0- 2+ FISH ampl: 12IHC 0-2+ FISH ampl: 25IHC 3+: 4IHC 0- 2+ FISH ampl: 21 Citation Format: Emanuela Ferraro, Anton Safonov, Hanna Y Wen, Edi Brogi, Mithat Gonan, Andrea V. Barrio, Pedram Razavi, Sarat Chandarlapaty, Shanu Modi, Andrew D. Seidman, Larry Norton, Mark E. Robson, Chau T. Dang. Clinical implication of HER2 status change after neoadjuvant chemotherapy with Trastuzumab and Pertuzumab (HP) in patients with HER2-positive breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-06.

Background: The current standard of care (SOC) for neoadjuvant treatment of human epidermal growth factor receptor 2 (HER2)-positive early-stage breast cancer (EBC) consists of trastuzumab + pertuzumab and polychemotherapy. These multiagent regimens expose patients to short- and long-term toxicities, and many patients, particularly those with locally advanced or inflammatory disease, still experience relapse and/or death. In the phase 2 DESTINY-Breast01 study, T-DXd monotherapy demonstrated efficacy, with a confirmed objective response rate of 61.4% (complete response, 6.5%), median time to response of 1.6 months, and median progression-free survival of 19.4 months in patients with previously treated HER2-positive unresectable/metastatic breast cancer (Modi et al. SABCS 2020. Abstract PD3-06). Given the efficacy of T-DXd monotherapy, it is anticipated that replacing all or part of these SOC regimens with T-DXd could benefit patients with high-risk HER2-positive EBC. Here, we describe a phase 3 trial evaluating the efficacy, safety, and tolerability of T-DXd monotherapy or T-DXd followed by paclitaxel + trastuzumab + pertuzumab (THP) vs dose-dense doxorubicin + cyclophosphamide followed by THP (ddAC-THP) in patients with high-risk HER2-positive EBC. Methods: DESTINY-Breast11 is a phase 3, global, open-label, multicenter trial to determine the efficacy and safety of T-DXd monotherapy or T-DXd followed by THP as neoadjuvant treatment vs ddAC-THP in patients with high-risk (T stage ≥3 and/or node positive or inflammatory) HER2-positive EBC. Approximately 624 patients will be randomized 1:1:1 into 3 arms (arm A: T-DXd monotherapy every 3 weeks [q3w] for eight 3-week cycles; arm B: T-DXd [q3w for four 3-week cycles] followed by THP [paclitaxel every week + trastuzumab + pertuzumab q3w for four 3-week cycles]; arm C: ddAC-THP [ddAC every 2 weeks for four 2-week cycles followed by THP for four 3-week cycles]), stratified by hormone receptor status (positive vs negative) and central HER2 immunohistochemical score (IHC; IHC 3+ vs other). Patients should undergo breast or axillary surgery 3 to 6 weeks after administration of the last cycle of assigned treatment. After surgery, patients will receive treatment per local clinical standards. For patients who achieve a pathological complete response (pCR), adjuvant HER2-directed therapy for up to 1 year is recommended. For patients who do not achieve a pCR, therapy with up to 14 cycles of trastuzumab emtansine is recommended. Radiotherapy and endocrine therapy should be administered per local clinical standards. After the last dose of study treatment, patients will be assessed for survival and recurrence every 3 months for the first 3 years and every 6 months in years 4 and 5. The primary endpoint is pCR (ypT0/Tis ypN0) (defined as absence of invasive cancer in the breast and sampled regional lymph nodes) by central review. Secondary endpoints include pCR (ypT0 ypN0) (defined as absence of invasive and in situ cancer in the breast and sampled regional lymph nodes) by central review as well as 3-year event-free survival, 3-year invasive disease-free survival, overall survival, patient-reported tolerability, physical functioning, immunogenicity, pharmacokinetics, and safety. Exploratory endpoints include 3-year distant metastasis-free survival, objective response rate, rate of breast-conserving surgery, biomarkers, patient-reported outcomes, and healthcare resource utilization. Citation Format: Nadia Harbeck, Jean-François Boileau, Shanu Modi, Catherine M Kelly, Shinji Ohno, Jiong Wu, Mark Brekenridge, Pia Herbolsheimer, Tinghui Yu, Lajos Pusztai. A phase 3, open-label trial of neoadjuvant trastuzumab deruxtecan (T-DXd) monotherapy or T-DXd followed by THP compared with ddAC-THP in patients with high-risk HER2-positive early-stage breast cancer (DESTINY-Breast11) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT1-12-04.

Purpose: HER2-amplified breast cancer is sometimes clinically insensitive to HER2-targeted treatment with trastuzumab. Laboratory models of resistance have causally implicated changes in HER2 expression and activation of the phosphoinositide 3-kinase (PI3K)–AKT pathway. We conducted a prospective tissue acquisition study to determine if there is evidence for these lesions in metastatic tumors that have progressed on trastuzumab-containing therapy.Experimental Design: From 2/2007 to 11/2011, 63 patients with HER2-amplified breast cancer with recurrence of disease after adjuvant trastuzumab therapy or World Health Organization–defined progression of metastatic disease on a trastuzumab-containing regimen were prospectively enrolled and underwent tumor biopsy. Specimens were analyzed for activating mutations in PIK3CA and HER2 by Sequenom and analyzed for HER2 and PTEN status by immunohistochemistry.Results: In 53/60 cases (88%, 3 cases not evaluable for HER2), HER2 overexpression persisted in the metastatic tumor following trastuzumab exposure. Among the 7 cases lacking HER2 overexpression, repeat analysis of the pretreatment tumor failed to confirm HER2 overexpression in five cases. Among cases evaluable for PTEN (56) or PI3K mutation (45), absent or significantly diminished PTEN expression was noted in 33 (59%) and activating mutations in PIK3CA in 13 (29%). The combined rate of PTEN loss and PIK3CA mutation in the trastuzumab-refractory tumors was 71% compared with 44% (P = 0.007) in an unexposed cohort of 73 HER2-amplified tumors.Conclusions: In this series of prospectively collected trastuzumab-refractory human breast cancers, loss of HER2 overexpression was rare, whereas activation of the PI3K-AKT pathway through loss of PTEN or PIK3CA mutation was frequently observed. Clin Cancer Res; 18(24); 6784–91. ©2012 AACR.

Dose selection details, T cell activation/exhaustion flow assay and multiplex cytokine measurements.

Purpose:Report results of the phase Ib dose-escalation/expansion study of triplet therapy with cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor (ribociclib), mTOR inhibitor (everolimus), and endocrine therapy (exemestane).Patients and Methods:Postmenopausal women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−), pretreated, advanced breast cancer (ABC) were enrolled. The primary objective of the dose-escalation phase was to estimate the MTD and recommended phase II dose (RP2D) of triplet therapy through evaluation of the incidence of dose-limiting toxicities. Safety, tolerability, and efficacy of the RP2D were evaluated in the dose-expansion phase in patients naïve or refractory to CDK4/6 inhibitor therapy.Results:Patients (N = 116) received triplet therapy (n = 83 in the dose-escalation phase; n = 33 in the dose-expansion phase). A dose-dependent drug–drug interaction was observed for everolimus, with exposure increasing two- to fourfold in the presence of ribociclib. The RP2D was determined to be ribociclib 300 mg once daily, 3 weeks on/1 week off in a 4-week cycle, plus everolimus 2.5 mg once daily, plus exemestane 25 mg once daily taken with food. The safety profile was consistent with the known profiles of the combination partners, and preliminary evidence of antitumor activity was observed. Higher ESR1 gene expression trended with better treatment response to triplet therapy; higher gene expression of MAPK pathway genes trended with worse treatment response.Conclusions:Triplet therapy with endocrine therapy and mTOR and CDK4/6 inhibition provides clinical benefit and an acceptable safety profile in previously treated postmenopausal women with HR+, HER2− ABC.

PDF file - 66K

Best overall response by RECIST 1.1 and PCWG2 for bone.

Purpose: HSP90 is a chaperone protein required for the stability of a variety of client proteins. 17-Demethoxygeldanamycin (17-AAG) is a natural product that binds to HSP90 and inhibits its activity, thereby inducing the degradation of these clients. In preclinical studies, HER2 is one of the most sensitive known client proteins of 17-AAG. On the basis of these data and activity in a phase I study, we conducted a phase II study of 17-AAG (tanespimycin) with trastuzumab in advanced trastuzumab-refractory HER2-positive breast cancer.Experimental Design: We enrolled patients with metastatic HER2+ breast cancer whose disease had previously progressed on trastuzumab. All patients received weekly treatment with tanespimycin at 450 mg/m2 intravenously and trastuzumab at a conventional dose. Therapy was continued until disease progression. The primary endpoint was response rate by Response Evaluation Criteria in Solid Tumors (RECIST) criteria.Results: Thirty-one patients were enrolled with a median age of 53 years and a median Karnofsky performance status (KPS) of 90%. The most common toxicities, largely grade 1, were diarrhea, fatigue, nausea, and headache. The overall response rate was 22%, the clinical benefit rate [complete response + partial response + stable disease] was 59%, the median progression-free survival was 6 months (95% CI: 4–9), and the median overall survival was 17 months (95% CI: 16–28).Conclusions: This is the first phase II study to definitively show RECIST-defined responses for 17-AAG in solid tumors. Tanespimycin plus trastuzumab has significant anticancer activity in patients with HER2-positive, metastatic breast cancer previously progressing on trastuzumab. Further research exploring this therapeutic interaction and the activity of HSP90 inhibitors is clearly warranted. Clin Cancer Res; 17(15); 5132–9. ©2011 AACR.

Supplemental Figure 2. Tumor PU-H71 retention at 24 hours post-injection (quantified by standard uptake value) is not explained by plasma radiotracer exposure (quantified by plasma AUC from 10 min to 4 h post-injection, see Methods), as indicated by Spearman Test R-value.

Tumor PU-H71 retention at 24 hours post-injection (quantified by standard uptake value) is not explained by plasma radiotracer exposure (quantified by plasma AUC from 10 min to 4 h post-injection, see Methods), as indicated by Spearman Test R-value.

Purpose:DLYE5953A is an antibody–drug conjugate consisting of an anti-LY6E antibody covalently linked to the cytotoxic agent monomethyl auristatin E. This study characterized the safety, pharmacokinetics, immunogenicity, potential biomarkers, and antitumor activity of DLYE5953A in patients with metastatic solid tumors.Patients and Methods:This was a phase I, open-label, 3+3 dose-escalation, and dose-expansion study of DLYE5953A administered intravenously every 21 days (Q3W) in patients with locally advanced or metastatic solid malignancies.Results:Sixty-eight patients received DLYE5953A (median, four cycles; range, 1–27). No dose-limiting toxicities were identified during dose escalation (0.2–2.4 mg/kg; n = 20). The recommended phase II dose (RP2D) of 2.4 mg/kg Q3W was based on overall safety and tolerability. Dose-expansion cohorts for HER2-negative metastatic breast cancer (HER2-negative MBC; n = 23) and non–small cell lung cancer (NSCLC; n = 25) patients were enrolled at the RP2D. Among patients receiving DLYE5953A 2.4 mg/kg (n = 55), the most common (≥30%) related adverse events (AEs) included alopecia, fatigue, nausea, and peripheral neuropathy. Grade ≥3 related AEs occurred in 14 of 55 (26%) patients, with neutropenia being the most common (13%). DLYE5953A demonstrated linear total antibody pharmacokinetics at doses of ≥0.8 mg/kg with low unconjugated monomethyl auristatin E levels in blood. Partial response was confirmed in eight of 68 (12%) patients, including three of 29 patients with MBC (10%) and five of 25 patients with NSCLC (20%) at the RP2D. Stable disease was the best response for 37 of 68 (54%) patients.Conclusions:DLYE5953A administered at 2.4 mg/kg has acceptable safety. Preliminary evidence of antitumor activity in patients with HER2-negative MBC and NSCLC supports further investigation of LY6E as a therapeutic target.

Supplemental Figure 1. Tumor retention of PU-H71 tracer varied considerably between patients. Tumor retention expressed as tumor:bloodpool SUV ratio (y-axis) measured on PET at 4 and 24 hours post tracer-injection.

Purpose:Tumor-associated macrophages correlate with increased invasiveness, growth, and immunosuppression. Activation of the colony-stimulating factor-1 receptor (CSF-1R) results in proliferation, differentiation, and migration of monocytes/macrophages. This phase I study evaluated the immunologic and clinical activity, and safety profile of CSF-1R inhibition with the mAb LY3022855.Patients and Methods:Patients with advanced refractory metastatic breast cancer (MBC) or metastatic castration-resistant prostate cancer (mCRPC) were treated with LY3022855 intravenously in 6-week cycles in cohorts: (A) 1.25 mg/kg every 2 weeks (Q2W); (B) 1.0 mg/kg on weeks 1, 2, 4, and 5; (C) 100 mg once weekly; (D)100 mg Q2W. mCRPC patients were enrolled in cohorts A and B; patients with MBC were enrolled in all cohorts. Efficacy was assessed by RECIST and Prostate Cancer Clinical Trials Working Group 2 criteria.Results:Thirty-four patients (22 MBC; 12 mCRPC) received ≥1 dose of LY3022855. At day 8, circulating CSF-1 levels increased and proinflammatory monocytes CD14DIMCD16BRIGHT decreased. Best RECIST response was stable disease in five patients with MBC (23%; duration, 82–302 days) and three patients with mCRPC (25%; duration, 50–124 days). Two patients with MBC (cohort A) had durable stable disease >9 months and a third patient with MBC had palpable reduction in a nontarget neck mass. Immune-related gene activation in tumor biopsies posttreatment was observed. Common any grade treatment-related adverse events were fatigue, decreased appetite, nausea, asymptomatic increased lipase, and creatine phosphokinase.Conclusions:LY3022855 was well tolerated and showed evidence of immune modulation. Clinically meaningful stable disease >9 months was observed in two patients with MBC.

Assessment of tumor associated macrophage depletion using macrophage gene signature. The downward trend (pre vs post, indicating depletion of TAMs) of the gene signature did not appear pronounced in any of the patient samples except for patient C.

Supplementary Fig 2

Supplementary figures and methods

PDF file - 1392K, PTEN IHC changes from pre-trastuzumab to post-trastuzumab samples. Depicted are photomicrographs of PTEN change from reduced to loss of expression: a) PTEN expression by IHC in the primary breast invasive carcinoma with reduced nuclear and cytoplasmic staining as compared to the adjacent normal stroma (200X); b) HE staining of the primary lesion (200X); c) PTEN complete loss of expression in the secondary invasive carcinoma with absence of any staining in the lesion as compared to the adjacent normal stroma (200X); d) HE staining of the secondary lesion (200X)

Purpose:Activating mutations in PIK3CA promote resistance to HER2-targeted therapy in breast cancer; however, inhibition of PI3K alone leads to escape via feedback upregulation of HER3. Combined inhibition of HER2, HER3, and PI3K overcomes this mechanism preclinically.Patients and Methods:This phase I study investigated the MTD of alpelisib given in combination with trastuzumab and LJM716 (a HER3-targeted antibody) in patients with PIK3CA-mutant HER2-positive (HER2+) metastatic breast cancer (MBC) using the continual reassessment method. Secondary analyses included efficacy and exploratory correlative studies.Results:Ten patients were treated initially with daily alpelisib (arm A). Grade ≥3 adverse events seen in ≥2 patients included diarrhea (n = 6), hypokalemia (n = 3), abnormal liver enzymes (n = 3), hyperglycemia (n = 2), mucositis (n = 2), and elevated lipase (n = 2). The MTD of alpelisib in arm A was 250 mg daily. This prompted the opening of arm B in which 11 patients received intermittently dosed alpelisib. Grade ≥3 adverse events seen in ≥2 patients included diarrhea (n = 5), hypokalemia (n = 3), and hypomagnesemia (n = 2). The MTD of alpelisib in arm B was 350 mg given 4 days on, 3 days off. Among 17 patients assessed, 1 had a partial response, 14 had stable disease, and 2 had disease progression at best response. Five patients had stable disease for >30 weeks. mRNA profiling of pre- and on-treatment tissue demonstrated PIK3CA target engagement by alpelisib via induction of downstream signaling and feedback pathways.Conclusions:Combination treatment with alpelisib, trastuzumab, and LJM716 was limited by gastrointestinal toxicity. Further efforts are warranted to target the PI3K pathway in HER2+ MBC.

PET detects subcentimeter PU-H71 retention by breast cancer metastases. 65-year-old female with stage IV breast cancer, off-treatment. 124I-PU-H71 PET (right), CT (left), and fusion PET/CT (middle) images show corresponding axial planes of chest, obtained 24 hours post-injection. Tracer has cleared from blood (asterisk, aorta) with sustained PU-H71 retention by biopsy-proven subcentimeter pulmonary metastasis (arrow) and left internal mammary and mediastinal nodal metastases (arrowheads).

Supplementary Appendix

PDF file, 37K, Human PBMCs Sample Preparation, Western Blot assay for Hsp90 Client Proteins, Luminex Assay for Hsp90 Client Proteins.