Search

Background: CTX + dual HER2-targeting monoclonal antibodies (mAb) remains a standard of care for treatment (Tx) of both HER2+ early-stage and MBC. However, when the SOPHIA trial was launched, limited Tx options existed after progression on T, pertuzumab (P), and ado-trastuzumab emtansine. M, an Fc-engineered anti-HER2 mAb, targets the same epitope as T and exerts similar antiproliferative effects. M enhances CD16A-mediated ADCC compared to T. Furthermore, M treatment is associated with increased HER2-specific T- and B-cell responses and increased T-cell clonality compared to baseline. The phase 3 SOPHIA (NCT02492711) study demonstrated PFS benefit of M vs T, both + CTX, in HER2+ MBC pts. M improved PFS over T, with a 24% relative risk reduction (HR .76; 95% CI .59-.98; P=.033; median, 5.8 [95% CI 5.5-7.0] months (mo) vs 4.9 [95% CI 4.2-5.6] mo (Rugo HS, et al. JAMA Oncol 2021), resulting in FDA approval. Median OS after 270 mortality events (2nd interim analysis) was 21.6 mo with M vs 19.8 mo with T (HR .89; 95% CI .69-1.13; P=.33). Here we report final OS after 385 events, as well as updated safety.Methods: Pts with disease progression after ≥2 lines of anti-HER2 Tx, including P, and 1-3 lines of Tx for HER2+ MBC were randomized 1:1 to CTX + either M (15 mg/kg) or T (8 mg/kg loading dose, then 6 mg/kg), both given IV every 3 weeks. Randomization was stratified by number of metastatic sites (≤2, >2), lines of Tx for MBC (≤2, >2), and CTX choice (capecitabine, eribulin, gemcitabine, or vinorelbine). Sequential primary end points were central-blinded review of PFS and OS.Results: The intent-to-treat (ITT) population comprised 536 pts (M, 266; T, 270). At the median follow-up of 20.2 mo among all ITT pts, pts received a median of 7 cycles of M + CTX vs 6 cycles of T + CTX. Median OS after 385 events in the ITT population was 21.6 mo with M vs 21.9 mo with T (HR .95; 95% CI .77-1.17; P=.62; Table). Based on a prespecified, non-α-allocated exploratory analysis, a numerical OS advantage in favor of the M arm was observed in the subgroup of pts homozygous for the CD16A-158F low-affinity allele (median OS, 23.6 vs 19.2 mo; HR .72; 95% CI .52-1.00; nominal P=.05). In contrast, in the small subgroup of CD16A-158V homozygotes, median OS was longer for T vs M (31.1 mo vs 22.0 mo; HR 1.77; 95% CI 1.01-3.12; nominal P=.04). Grade ≥3 adverse events (AE) occurred in 146 pts (55.3%) receiving M vs 141 pts (53.0%) receiving T. Serious AEs were seen in 47 pts (17.8%) receiving M vs 51 pts (19.2%) receiving T. Incidence of infusion-related reactions was higher with M (36 [13.6%]) vs T (9 [3.4%]). Left ventricular dysfunction requiring delay or cessation of M/T administration occurred in 4 pts (1.5%) receiving M and in 7 pts (2.6%) receiving T. Conclusions: The median OS in the ITT population was not statistically different between the 2 arms. An exploratory analysis of CD16A genotyping indicates a numerical OS advantage in favor of M in F homozygous pts, along with a numerical OS advantage in favor of T in V homozygous pts. Safety of M + CTX was similar to previous reports and consistent with M FDA-approved label. Studies of M in HER2+ breast cancer pts with different CD16A allelic variants are warranted, including MARGOT, the neoadjuvant investigator-initiated study on the efficacy of M vs T in pts carrying F-allelic variants of CD16A. Median OSITT analysisPrespecified, non-α-allocated exploratory analysis (n=506)N=536CD16A-158F carriers (F/F and F/V)(n=437)CD16A-158F homozygotes (F/F)(n=192)CD16A-158F/V heterozygotes(n=245)CD16A-158V homozygotes (V/V)(n=69)aM + CTX, mo21.6 (n=266)23.3 (n=221)23.6 (n=102)21.3 (n=119)22.0 (n=37)T + CTX, mo21.9 (n=270)20.8 (n=216)19.2 (n=90)22.0 (n=126)31.1 (n=32)HR (95% CI)0.95 (0.77-1.17)0.86 (0.69-1.08)0.72 (0.52-1.00)0.96 (0.71-1.30)1.77 (1.01-3.12)P value0.620.19b0.05b0.78b0.04bAbbreviations: CTX, chemotherapy; HR, hazard ratio; ITT, intent to treat; M, margetuximab; mo, months; OS, overall survival; T, trastuzumab. Cutoff date: June 14, 2021. aThis subgroup was characterized by an imbalance in poor prognostic features. bNominal P value. Citation Format: Hope Rugo, Seock-Ah Im, Fatima Cardoso, Javier Cortes, Giuseppe Curigliano, Antonino Musolino, Mark D. Pegram, Thomas Bachelot, Gail S. Wright, Cristina Saura, Santiago Escrivá-de-Romaní, Michelino De Laurentiis, Gary N. Schwartz, Timothy Pluard, Francesco Ricci, William Gwin, III, Christelle Levy, Ursa Brown-Glaberman, Jean-Marc Ferrero, Maaike de Boer, Sung-Bae Kim, Katarína Petráková, Denise A. Yardley, Orit Freedman, Erik H. Jakobsen, Einav Nili Gal-Yam, Rinat Yerushalmi, Peter A. Fasching, Emily Ashley, Shengyan Hong, Minori Rosales, William J. Gradishar. Phase 3 SOPHIA study of margetuximab (M) + chemotherapy (CTX) vs trastuzumab (T) + CTX in patients (pts) with HER2+ metastatic breast cancer (MBC) after prior anti-HER2 therapies: Final overall survival (OS) analysis [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 PD8-01.

Background Resected HER2 breast cancer patients treated with adjuvant trastuzumab and chemotherapy have superior survival compared to patients treated with chemotherapy alone. We previously showed that trastuzumab and chemotherapy induce HER2-specific antibodies which correlate with improved survival in HER2 metastatic breast cancer patients. It remains unclear whether the generation of immunity required trastuzumab and whether endogenous antibody immunity is associated with improved disease-free survival in the adjuvant setting. In this study, we addressed this question by analyzing serum anti-HER2 antibodies from a subset of patients enrolled in the NCCTG trial N9831, which includes an arm (Arm A) in which trastuzumab was not used. Arms B and C received trastuzumab sequentially or concurrently to chemotherapy, respectively. Methods Pre-and post-treatment initiation sera were obtained from 50 women enrolled in N9831. Lambda IgG antibodies (to avoid detection of trastuzumab) to HER2 were measured and compared between arms and with disease-free survival. Results Prior to therapy, across all three arms, N9831 patients had similar mean anti-HER2 IgG levels. Following treatment, the mean levels of antibodies increased in the trastuzumab arms but not the chemotherapy-only arm. The proportion of patients who demonstrated antibodies increased by 4% in Arm A and by 43% in the Arms B and C combined (p = 0.003). Cox modeling demonstrated that larger increases in antibodies were associated with improved disease-free survival in all patients (HR = 0.23; p = 0.04). Conclusions These results show that the increased endogenous antibody immunity observed in adjuvant patients treated with combination trastuzumab and chemotherapy is clinically significant, in view of its correlation with improved disease-free survival. The findings may have important implications for predicting treatment outcomes in patients treated with trastuzumab in the adjuvant setting. Trial registration ClinicalTrials.gov, NCT00005970. Registered on July 5, 2000. Electronic supplementary material The online version of this article (10.1186/s13058-018-0989-8) contains supplementary material, which is available to authorized users.

Metastatic breast cancer continues to be a life-threatening diagnosis that impacts hundreds of thousands of patients around the world. Targeted therapies are usually associated with less toxicity compared with cytotoxic chemotherapies and often induce response or durable disease control in estrogen receptor (ER) and/or HER2+ breast cancers. Drugs that target CDK 4/6 either alone or in combination with endocrine therapy have demonstrated substantial improvements in progression-free survival (PFS) compared with endocrine monotherapy. Most recently, PARP inhibitors have shown longer PFS compared with physician’s choice of chemotherapy in BRCA-associated cancers, leading to the first U.S. Food and Drug Administration (FDA) approval of a targeted therapy with the potential to benefit a subgroup of patients with triple-negative breast cancer (TNBC). Finally, newer drug delivery strategies using antibody drug conjugates have also allowed a “targeted approach” to deliver moderate to extremely potent cytotoxins directly to sites of metastatic disease, with less toxicity.

Background: To date, anti-HER2 monoclonal antibodies are the only immune therapies approved for treating pts with HER2-over-expressing cancers. Intratumoral delivery of immunostimulatory adjuncts such as toll-like receptor (TLR) 7/8 agonists can activate tumor resident antigen-presenting cells (APCs) to promote antitumor immunity. To optimize intratumoral delivery while leveraging favorable preclinical biology we developed a novel, systemically delivered ISAC (BDC-1001). BDC-1001 consists of an investigational trastuzumab biosimilar chemically conjugated to a TLR 7/8 agonist (payload) with an intervening non-cleavable linker. BDC-1001 activates human myeloid APCs and retains antibody-mediated effector functions such as antibody-dependent cellular cytotoxicity/phagocytosis. Our trastuzumab-based ISACs seem to elicit potent and durable immune-mediated antitumor efficacy including tumor regression in a TLR- and Fc receptor-dependent manner in xenograft and syngeneic tumor resistant models (Ackerman et al. Nat Cancer 2020). BDC-1001 did not induce interstitial lung disease, cytokine release syndrome, or thrombocytopenia in non-human primate studies. A four-part phase 1/2, first-in-human study was initiated in 2020 to evaluate BDC-1001 with or without (±) pembro in pts with HER2-overexpressing or amplified advanced solid tumors. Methods: This phase 1/2 dose-escalation/expansion study will enroll up to 390 pts with HER2-overexpressing (IHC2+ or 3+) or HER2-amplified (by in situ hybridization or next-generation sequencing) advanced solid tumors. Patients may have received prior anti-HER2 therapies. Primary objectives of dose-escalation are safety and tolerability, and establishing a recommended phase 2 dose of BDC-1001 alone administered IV q3w (Part 1) and combined with pembro (Part 2). Primary endpoints of Parts 1 & 2 include assessment of safety and tolerability; dose-limiting immune-related toxicities in a 3+3 design. The dose-expansion phase 2 portion will evaluate preliminary antitumor activity of BDC-1001 alone (Part 3) and with pembro (Part 4) using RECIST v1.1 and iRECIST. The primary endpoint of the phase 2 is best\ overall response rate; with secondary endpoints of duration of response, disease control rate, and progression-free survival. Exploratory objectives include pharmacokinetic parameters and pharmacodynamic biomarkers associated with drug exposure to help elucidate mechanism of action and identify biomarkers to improve selection of pts most likely to benefit from the single therapy or combination. Recruitment is ongoing (NCT04278144). Citation Format: Manish R. Sharma, Richard D. Carvajal, Daniel Catenacci, Leisha A. Emens, Glenn J. Hanna, Dejan Juric, Yoon-Koo Kang, Jeeyun Lee, Keun-Wook Lee, Bob T. Li, Kathleen Moore, Mark D. Pegram, Paula R. Pohlmann, Drew Rasco, Alexander Spira, Arielle L. Heeke, Ding Wang, Lawrence Garbo, Sudhir Manda, Jasgit Sachdev, Shelley E. Ackerman, Heidi LeBlanc, David Dornan, Marcin Kowanetz, Michael N. Alonso, Amreen Husain, Edith A. Perez, Ecaterina Ileana Dumbrava. Phase 1/2 study of a novel HER2 targeting TLR7/8 immune-stimulating antibody conjugate (ISAC), BDC-1001, alone and in combination with pembrolizumab (pembro) in patients (pts) with HER2-expressing advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT218.

Introduction: The irreversible pan-HER inhibitor NER showed modest single agent activity for HER2mut MBC in Part I of MutHER trial. In Part II, we hypothesized that (1) N+F would improve activity in estrogen receptor positive (ER+) HER2mut MBC due to ER-HER2 crosstalk and (2) dual HER2 blockade by adding trastuzumab at disease progression (PD) could overcome resistance. Methods: Pts with ER+HER2mut MBC were enrolled to 2 cohorts (FUL treated or naive) to receive N+F with diarrhea prophylaxis. ER- pts received NER in an exploratory ER- cohort. Trastuzumab was added at PD if approved by insurance. Simon's Minimax 2-stage phase II design with the primary endpoint of clinical benefit rate (CBR: rates of complete/partial response [CR/PR] plus stable disease [SD] >24 weeks [wks]), with anticipated vs null hypothesis being CBR of 55% vs 35% (FUL treated) or 65% vs 40% (FUL naïve) with 80% power, 1 sided 0.05 alpha, was used. Secondary endpoints included progression free survival (PFS) and adverse events (AEs). Serial blood samples were analyzed for circulating tumor DNA (ctDNA) by Guardant360 for concomitant mutations, HER2mut variant allele frequency (VAF) dynamics, and resistance mechanisms. Results: Between Sep. 2015 and Oct. 2020, 40 pts with HER2mut MBC were enrolled, completing the 1st stage of each ER+ cohort. 35 pts (21 FUL treated, 10 FUL naïve, 4 ER-) were evaluable for response, with median age 63 (35-82) years, 3 (0-12) prior MBC regimen, lobular BC in 13 (37%) and visceral mets in 32 (91%) pts. 21 (68%) ER+ pts had prior CDK4/6 inhibitor. All but 1 pt has come off study due to PD. Table 1 shows the efficacy by cohort. Further enrollment is closed per protocol. Adding trastuzumab at PD induced CB in 4 (3 PR, 1 SD≥24 wks) of 5 pts (1 ER-, 4 ER+), with PFS 28 (95% CI 18~NA) wks. Common AEs across cohorts were diarrhea (G3 21%) and fatigue (G3 5%). No G4 AEs. ctDNA HER2mut was detected in 72% (23/32) baseline (BL) samples tested. In pts with paired samples, HER2mut VAF decreased at C1D15/C2D1 from BL in 75% (15/20) and rose in 89% (16/18) at PD. Acquired HER2mut, including the T798I gatekeeper mutation, were detected in 2 pts at PD. Mutations in TP53 (53%), PIK3CA (43%), and CDH1 (35%) were common, but none significantly associated with PFS in all or ER+ pts. Conclusions: NER, or N+F, is active for HER2mut MBC with good tolerability. Adding trastuzumab at PD induced further response, supporting dual HER2 blockade for HER2mut MBC. Table 1.EfficacyCohortFUL treatedFUL naïveER-Best Response, n evaluablen = 21n = 10n = 4CR, n100PR, n431SD (≥ 24 wks), n300SD (< 24 wks), n1030PD, n343CBR, n with CB/total n evaluable, % (95% CI)8 of 20*, 40% (19~64%)3 of 10, 30% (7~65%)1 of 4, 25% (0.6~81%)mPFS (95% CI), wks, ITT (n)24 (16~31) wks, (n = 24)20 (8~NA) wks, (n = 11)8.5 (8~NA) wks, (n = 5)*20 of 21 pts are evaluable for CBR in the FUL treated Cohort as 1 pt had SD as best response and treatment is still ongoing. ITT (intent to treat) population is used for mPFS estimate. Citation Format: Cynthia X. Ma, Jingqin Luo, Rachel A. Freedman, Timothy Pluard, Julie Nangia, Janice Lu, Frances Valdez-Albini, Melody Cobleigh, Jason Jones, Nancy U. Lin, Eric Winer, P. Kelly Marcom, Shana Thomas, Jill Anderson, Brittney Haas, Kimberly M. Hamann, Richard Bryce, Alshad S. Lalani, Lisa Carey, Matthew Goetz, Feng Gao, Gretchen Kimmick, Mark Pegram, Matthew J. Ellis, Ron Bose. A phase II trial of neratinib (NER) or NER plus fulvestrant (FUL) (N+F) in HER2 mutant, non-amplified (HER2mut) metastatic breast cancer (MBC): Part II of MutHER [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT026.

Purpose: Based on promising preclinical data, we conducted a single-arm phase II trial to assess the clinical benefit rate (CBR) of neratinib, defined as complete/partial response (CR/PR) or stable disease (SD) ≥24 weeks, in HER2mut nonamplified metastatic breast cancer (MBC). Secondary endpoints included progression-free survival (PFS), toxicity, and circulating tumor DNA (ctDNA) HER2mut detection. Experimental Design: Tumor tissue positive for HER2mut was required for eligibility. Neratinib was administered 240 mg daily with prophylactic loperamide. ctDNA sequencing was performed retrospectively for 54 patients (14 positive and 40 negative for tumor HER2mut). Results: Nine of 381 tumors (2.4%) sequenced centrally harbored HER2mut (lobular 7.8% vs. ductal 1.6%; P = 0.026). Thirteen additional HER2mut cases were identified locally. Twenty-one of these 22 HER2mut cases were estrogen receptor positive. Sixteen patients [median age 58 (31–74) years and three (2–10) prior metastatic regimens] received neratinib. The CBR was 31% [90% confidence interval (CI), 13%–55%], including one CR, one PR, and three SD ≥24 weeks. Median PFS was 16 (90% CI, 8–31) weeks. Diarrhea (grade 2, 44%; grade 3, 25%) was the most common adverse event. Baseline ctDNA sequencing identified the same HER2mut in 11 of 14 tumor-positive cases (sensitivity, 79%; 90% CI, 53%–94%) and correctly assigned 32 of 32 informative negative cases (specificity, 100%; 90% CI, 91%–100%). In addition, ctDNA HER2mut variant allele frequency decreased in nine of 11 paired samples at week 4, followed by an increase upon progression. Conclusions: Neratinib is active in HER2mut, nonamplified MBC. ctDNA sequencing offers a noninvasive strategy to identify patients with HER2mut cancers for clinical trial participation. Clin Cancer Res; 23(19); 5687–95. ©2017 AACR.

Summary Background The antibody–drug conjugate trastuzumab emtansine is indicated for the treatment of patients with HER2-positive metastatic breast cancer previously treated with trastuzumab and a taxane. Approval of this drug was based on progression-free survival and interim overall survival data from the phase 3 EMILIA study. In this report, we present a descriptive analysis of the final overall survival data from that trial. Methods EMILIA was a randomised, international, open-label, phase 3 study of men and women aged 18 years or older with HER2-positive unresectable, locally advanced or metastatic breast cancer previously treated with trastuzumab and a taxane. Enrolled patients were randomly assigned (1:1) via a hierarchical, dynamic randomisation scheme and an interactive voice response system to trastuzumab emtansine (3·6 mg/kg intravenously every 3 weeks) or control (capecitabine 1000 mg/m 2 self-administered orally twice daily on days 1–14 on each 21-day cycle, plus lapatinib 1250 mg orally once daily on days 1–21). Randomisation was stratified by world region (USA vs western Europe vs or other), number of previous chemotherapy regimens for unresectable, locally advanced, or metastatic disease (0 or 1 vs >1), and disease involvement (visceral vs non-visceral). The coprimary efficacy endpoints were progression-free survival (per independent review committee assessment) and overall survival. Efficacy was analysed in the intention-to-treat population; safety was analysed in all patients who received at least one dose of study treatment, with patients analysed according to the treatment actually received. On May 30, 2012, the study protocol was amended to allow crossover from control to trastuzumab emtansine after the second interim overall survival analysis crossed the prespecified overall survival efficacy boundary. This study is registered with ClinicalTrials.gov, number NCT00829166. Findings Between Feb 23, 2009, and Oct 13, 2011, 991 eligible patients were enrolled and randomly assigned to either trastuzumab emtansine (n=495) or capecitabine and lapatinib (control; n=496). In this final descriptive analysis, median overall survival was longer with trastuzumab emtansine than with control (29·9 months [95% CI 26·3–34·1] vs 25·9 months [95% CI 22·7–28·3]; hazard ratio 0·75 [95% CI 0·64–0·88]). 136 (27%) of 496 patients crossed over from control to trastuzumab emtansine after the second interim overall survival analysis (median follow-up duration 24·1 months [IQR 19·5–26·1]). Of those patients originally randomly assigned to trastuzumab emtansine, 254 (51%) of 495 received capecitabine and 241 [49%] of 495 received lapatinib (separately or in combination) after study drug discontinuation. In the safety population (488 patients treated with capecitabine plus lapatinib, 490 patients treated with trastuzumab emtansine), fewer grade 3 or worse adverse events occurred with trastuzumab emtansine (233 [48%] of 490) than with capecitabine plus lapatinib control treatment (291 [60%] of 488). In the control group, the most frequently reported grade 3 or worse adverse events were diarrhoea (103 [21%] of 488 patients) followed by palmar–plantar erythrodysaesthesia syndrome (87 [18%]), and vomiting (24 [5%]). The safety profile of trastuzumab emtansine was similar to that reported previously; the most frequently reported grade 3 or worse adverse events in the trastuzumab emtansine group were thrombocytopenia (70 [14%] of 490), increased aspartate aminotransferase levels (22 [5%]), and anaemia (19 [4%]). Nine patients died from adverse events; five of these deaths were judged to be related to treatment (two in the control group [coronary artery disease and multiorgan failure] and three in the trastuzumab emtansine group [metabolic encephalopathy, neutropenic sepsis, and acute myeloid leukaemia]). Interpretation This descriptive analysis of final overall survival in the EMILIA trial shows that trastuzumab emtansine improved overall survival in patients with previously treated HER2-positive metastatic breast cancer even in the presence of crossover treatment. The safety profile was similar to that reported in previous analyses, reaffirming trastuzumab emtansine as an efficacious and tolerable treatment in this patient population. Funding F Hoffmann-La Roche/Genentech.

Background: Human epidermal growth factor receptor 2 (HER2)-targeting monoclonal antibodies (mAb) are the standard of care in early-to-advanced HER2+ breast cancer. However, for relapsed/refractory disease, limited options exist after progression on trastuzumab (T), pertuzumab (P), and ado-trastuzumab emtansine. Margetuximab (M) is an Fc-engineered anti-HER2 mAb that targets the same epitope as T and exerts similar antiproliferative effects. Compared with T, M has higher affinity for both 158V (high binding) and 158F (low binding) alleles of the activating Fc receptor, CD16A. M enhances innate immunity, including CD16A-mediated antibody-dependent cellular cytotoxicity, more effectively than T. M also potentiates adaptive immunity in treated patients (pts), including enhanced clonality of the T-cell repertoire and induction of HER2-specific T- and B-cell responses. SOPHIA (NCT02492711) is a phase 3 trial that demonstrated the benefit of M vs T, both with chemotherapy, in pts with HER2+ metastatic breast cancer (MBC). This trial is the first prospective analysis of the effect of CD16A genotype on anti-HER2 antibody efficacy. Methods: Pts with disease progression after at least 2 lines of anti-HER2 therapy, including P, and 1-3 lines of therapy for HER2+ MBC were randomized 1:1 to chemotherapy + either M (15 mg/kg intravenously every 3 wk) or T. Randomization was stratified by number of metastatic sites (≤2, >2), lines of treatment for MBC (≤2, >2), and chemotherapy choice (capecitabine, eribulin, gemcitabine, or vinorelbine). Primary endpoints were central-blinded review of progression-free survival (PFS) and overall survival (OS). The first interim OS analysis at time of PFS analysis (October 10, 2018) was immature, with 158 of 385 deaths (41%) needed for final OS analysis. The stopping boundary was not crossed. A second interim OS analysis was planned after 270 deaths and will be reported here. Results: The intent-to-treat (ITT) population comprised 536 pts (M, 266; H, 270). M + chemotherapy prolonged PFS vs T + chemotherapy (median PFS, 5.8 vs 4.9 mo; hazard ratio [HR], 0.76; 95% confidence interval [CI]: 0.59-0.98; P=0.033). Results were more pronounced in pts with CD16A genotypes containing a 158F allele (median PFS, 6.9 vs 5.1 mo; HR, 0.68; 95% CI: 0.52-0.90; nominal P=0.005). OS at the first interim analysis demonstrated a HR (95% CI) of 0.95 (0.69-1.31) for the ITT population (n=536) and an HR of 0.82 (95% CI: 0.58-1.17) for the CD16A/FF or FV genotype population (n=457). Grade ≥3 adverse events (AEs) occurred in 138 pts (52%) receiving M vs 128 pts (48%) receiving T. Serious AEs were seen in 39 (15%) receiving M vs 46 (17%) receiving T. The second planned interim analysis of OS (at n=270), as well as updated safety, will be presented. Conclusions: M + chemotherapy in pts with treated HER2+ MBC improves PFS vs T. Safety was comparable. CD16A genotyping suggests a greater benefit in pts with a 158F allele. Maturing data comparing the OS of pts treated with M vs T with chemotherapy will provide important new insights in characterizing clinical activity of this regimen in pts with MBC. Citation Format: Hope S. Rugo, Seock-Ah Im, Fatima Cardoso, Javier Cortes, Giuseppe Curigliano, Mark D. Pegram, Antonino Musolino, Thomas Bachelot, Gail S. Wright, Michelino De Laurentiis, Peter A. Kaufman, Timothy Pluard, Francesco Ricci, Lupe G. Salazar, Denise A. Yardley, Sutton Edlich, Shengyan Hong, Edwin Rock, William J. Gradishar, SOPHIA Study Group. Phase 3 SOPHIA study of margetuximab + chemotherapy vs trastuzumab + chemotherapy in patients with HER2+ metastatic breast cancer after prior anti-HER2 therapies: second interim overall survival analysis [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr GS1-02.

Background We assessed long-term cardiac safety and efficacy in patients with human epidermal growth factor receptor 2–positive early breast cancer treated with a trastuzumab biosimilar (SB3) or its reference product, trastuzumab (TRZ), in a phase 3 study. Methods Patients who completed the phase 3 study could be enrolled in this extension study. The outcomes included the incidence of symptomatic congestive heart failure (CHF), asymptomatic significant left ventricular ejection fraction (LVEF) decrease, incidence of other cardiac events, event-free survival (EFS), and overall survival. In post hoc analysis, the Cox proportional hazards regression model was used to assess factors associated with EFS. Results A total of 367 patients were enrolled in the study (SB3, n = 186; TRZ, n = 181). The median follow-up duration from the main study enrolment was 40.8 and 40.5 months for SB3 and TRZ, respectively. During the two-year follow-up after adjuvant therapy, incidence of asymptomatic significant LVEF decrease was rare (SB3, n = 1; TRZ, n = 2), with all patients recovering with LVEF ≥ 50%, and no cases of symptomatic CHF or other cardiac events were reported. At 3 years, the EFS was 91.9% with SB3 and 85.2% with TRZ. The number of patients with events was 17 (9.1%) with SB3 and 31 (17.1%) with TRZ [hazard ratio: 0.47, 95% confidence interval: 0.26–0.87]. Antibody-dependent cell-mediated cytotoxicity (ADCC) activity and the breast pathologic complete response rate were the factors associated with EFS. Conclusion Cardiotoxicity was rare in this extension study. EFS was higher with SB3 versus TRZ, with post hoc analysis suggesting that a downward drift in ADCC activity was a contributing factor. Clinical trial registration numbers NCT02771795 (EudraCT 2015-005663-17).

PURPOSE To evaluate the safety, pharmacokinetics, and pharmacodynamics of Hu5F9-G4 (5F9), a humanized IgG4 antibody that targets CD47 to enable phagocytosis. PATIENTS AND METHODS Adult patients with solid tumors were treated in four cohorts: part A, to determine a priming dose; part B, to determine a weekly maintenance dose; part C, to study a loading dose in week 2; and a tumor biopsy cohort. RESULTS Sixty-two patients were treated: 11 in part A, 14 in B, 22 in C, and 15 in the biopsy cohort. Part A used doses that ranged from 0.1 to 3 mg/kg. On the basis of tolerability and receptor occupancy studies that showed 100% CD47 saturation on RBCs, 1 mg/kg was selected as the priming dose. In subsequent groups, patients were treated with maintenance doses that ranged from 3 to 45 mg/kg, and most toxicities were mild to moderate. These included transient anemia (57% of patients), hemagglutination on peripheral blood smear (36%), fatigue (64%), headaches (50%), fever (45%), chills (45%), hyperbilirubinemia (34%), lymphopenia (34%), infusion-related reactions (34%), and arthralgias (18%). No maximum tolerated dose was reached with maintenance doses up to 45 mg/kg. At doses of 10 mg/kg or more, the CD47 antigen sink was saturated by 5F9, and a 5F9 half-life of approximately 13 days was observed. Strong antibody staining of tumor tissue was observed in a patient at 30 mg/kg. Two patients with ovarian/fallopian tube cancers had partial remissions for 5.2 and 9.2 months. CONCLUSION 5F9 is well tolerated using a priming dose at 1 mg/kg on day 1 followed by maintenance doses of up to 45 mg/kg weekly.

1043 Background: Tucatinib (TUC) is an oral tyrosine kinase inhibitor (TKI) highly specific for HER2. TUC is approved for use in combination with trastuzumab (T) and capecitabine (C) in patients (pts) with and without brain metastases (BM) who have received 1 or more prior anti-HER2–based regimens in the metastatic setting. In the primary analysis from the pivotal HER2CLIMB trial, the addition of TUC to T and C in pts with HER2+ metastatic breast cancer showed a statistically significant and clinically meaningful prolongation of progression-free (PFS) (HR = 0.54 [95% CI: 0.42, 0.71]; P < 0.001) and overall survival (OS) (HR = 0.66 [95% CI: 0.50, 0.88]; P = 0.005) (Murthy, et al. NEJM 2020). TUC in combination with T and C was well tolerated with few discontinuations other than for disease progression. Based on these data, the protocol was amended for unblinding of sites to treatment assignment to allow for crossover from the placebo arm to receive TUC in combination with T and C. Methods: HER2CLIMB (NCT02614794) is a global, randomized, double-blind, placebo-controlled trial in pts with unresectable locally advanced or metastatic HER2+ breast cancer previously treated with T, pertuzumab, and T-emtansine (T-DM1), including pts with untreated, treated stable, or treated and progressing BM. Overall 612 pts were randomized 2:1 to receive TUC 300 mg BID or placebo, each in combination with T and C. Randomization was stratified by BM, ECOG performance status, and geographic region. Protocol prespecified analysis of OS, PFS (by investigator assessment) and safety in the total study population will be performed at approximately 2 years from the last patient randomized. Results: Updated Kaplan-Meier time-to-event analysis of OS and PFS with hazard ratios and 95% confidence intervals for TUC arm vs placebo arm will be presented overall, as well as for OS in the prespecified subgroups reported previously (Murthy, et al. NEJM 2020). Safety and tolerability assessments will include frequency of adverse events by severity, dose modifications and discontinuation of study medications. Conclusions: Conclusions will be presented in the presentation. Clinical trial information: NCT02614794 .

1063 Background: Rintodestrant, a potent, oral selective estrogen receptor degrader, competitively binds and degrades the estrogen receptor (ER), thus blocking ER signaling in tumors resistant to other endocrine therapies (ET). Results from parts 1 and 2 dose-escalation/expansion indicate that once-daily (QD) rintodestrant has a favorable safety profile and antitumor activity in patients (pts) with heavily pretreated ER+/HER2– advanced breast cancer (ABC), including those with ESR1 variants (Aftimos et al. SABCS 2020 [PS12-04, PD8-07]). The optimal dose of rintodestrant was 800 mg. Here, we present part 3, combining rintodestrant with the CDK4/6 inhibitor palbociclib. Methods: This open-label study evaluated rintodestrant in pts with ER+/HER2– ABC after progression on ET (NCT03455270). Part 3 assessed rintodestrant 800 mg QD + palbociclib 125 mg QD for 21 days every 28 days. Key eligibility criteria included ≤1 line of chemotherapy and/or ≤1 line of ET in the advanced setting, with ≥6 months of ET in the advanced setting and/or ≥24 months in the adjuvant setting. Prior CDK4/6 inhibitor therapy was not allowed. Primary objectives included safety and efficacy. Secondary objectives included pharmacokinetics and antitumor activity (RECIST v1.1). Exploratory objectives included mutation profiling (cell-free DNA) at baseline and cycle 1 day 15. Results: Enrollment occurred Jul–Oct 2020. As of Dec 9, 2020, 40 pts were treated, with a median age of 58 years (35–76) and ECOG PS of 0 (70%) or 1 (30%); 20% had de novo stage 4 disease, 10% bone-only, and 68% visceral metastases. Median number of visceral sites was 1 (0–3): 30% of pts with lung and 40% with liver involvement. Median number of prior lines in the advanced setting was 1 (0–2), including chemotherapy (48%), fulvestrant (15%), and aromatase inhibitors (50%). Most recent ET was given in the adjuvant and metastatic settings in 28% and 73% of pts, respectively. Rintodestrant-related adverse events (AEs) were reported in 8% of pts—all nonserious and grade 2—and included nausea (3%), vomiting (3%), and neutropenia (3%). The most common (≥10%) treatment-related AEs (rintodestrant and/or palbociclib) were neutropenia (88%), leukopenia (45%), anemia (10%), and thrombocytopenia (10%); grade 3/4 neutropenia was 38%/15%, in line with the safety profile of palbociclib. No deaths or treatment discontinuations due to AEs were reported. At data cutoff (median treatment duration of 3 months [1.5–4.6]), 28 pts (70%) remained on study treatment, 2 (5%) had a confirmed partial response, and 27 (68%) had stable disease. Additional efficacy and pharmacodynamic data will be presented. Conclusions: Rintodestrant, as monotherapy or combined with palbociclib, continues to demonstrate an excellent safety/tolerability profile with promising antitumor activity in pts with ER+/HER2– ABC, including those with ESR1 variants. Clinical trial information: NCT03455270 .

2549 Background: BDC-1001 is a novel ISAC consisting of an investigational trastuzumab biosimilar chemically conjugated to a TLR 7/8 agonist with a non-cleavable linker. BDC-1001 was designed to activate the innate immune system, eliciting antibody-mediated effector functions (eg, antibody-dependent cellular phagocytosis) and a durable adaptive immune response. In preclinical tumor models resistant to anti-HER2 treatments, BDC-1001 demonstrated potent and durable immune-mediated antitumor efficacy. Methods: A 4-part, phase 1/2 dose-escalation/expansion study was initiated to evaluate BDC-1001 ± PD1 inhibitor pembrolizumab in pts with HER2-expressing solid tumors who had progressive disease on standard of care (NCT04278144). Preliminary results of the monotherapy dose escalation (Part 1) are reported. Pts with advanced metastatic HER2-expressing (IHC2/3+) or amplified solid tumors received BDC-1001 IV q3w in a 3+3 design w/ 12 pts/cohort backfill allowed. Primary objectives were to evaluate safety, tolerability, dose-limiting toxicities (DLTs) and determine a phase 2 dose; secondary objectives were to assess pharmacokinetics (PK), pharmacodynamics and preliminary anti-tumor activity. Results: As of Jan 29, 2021, 20 pts w/ a median age of 65 (46-85) have enrolled in 4 dose levels (0.15mg/kg to 5 mg/kg). Cancer types include breast, biliary, cervical, colorectal (CRC), lung, gastroesophageal, salivary, urinary tract and endometrial. Pts had received a median of 4 (1-7) prior therapies; 65% received >1 prior anti-HER2 therapy. All pts completed the 21-day DLT period; no DLTs or drug-related serious adverse events (AEs) have been observed. AEs deemed related to BDC-1001 have been mild to moderate including infusion-related reactions. The MTD has not been reached (treatment duration 5-17+wk); enrollment is ongoing. PK evaluations showed Cmax levels consistent with predicted modeling based on non-human primates (NHP). One pt with microsatellite stable (MSS) HER2+ CRC with lung metastases had a confirmed partial response after 4 cycles and remains on study; 2 additional pts with metastatic MSS HER2+ CRC had stable disease (SD) and a pt with heavily pretreated MSS endometrial cancer with lung metastases had confirmed SD and remains on treatment 17+ wk; 3 of these pts had received 2 prior anti-HER2 therapies. Conclusions: In this first-in-human study, BDC-1001 appears to be well-tolerated up to the dose tested to date (5 mg/kg), with Cmax levels achieved as predicted by NHP modeling. Evidence of clinical activity have been observed, including in pts previously treated with anti-HER2 therapy. Dose escalation is ongoing and will be followed by combination dosing with CPI and the phase 2 component in selected tumors. Clinical trial information: NCT04278144.

Background: The DNA-sensing nucleotidyl transferase enzyme cyclic GMP-AMP synthase (cGAS), its second-messenger product cyclic GMP-AMP (cGAMP), and the cGAMP sensor Stimulator of interferon Genes (STING) form a major cytoplasmic DNA-sensing mechanism in human cells [Barber GN. Nat Rev Immunol, 2015]. cGAMP-activated STING oligomers bind TANK-binding kinase 1 (TBK1), translocate from the endoplasmic reticulum to perinuclear vesicles, and phosphorylate transcription factor interferon (IFN) regulatory factor 3 (IRF3), resulting in IRF3 nuclear translocation to induce expression of type I IFNs such as IFNβ. This pathway is critical for controlling innate antiviral immune responses, and is implicated in anti-tumor adaptive immunity, yet little is known regarding its function in human primary breast cancer (BC). Methods: Immunohistochemistry (IHC) staining for cGAS (ab224144), STING (CST13647), TBK1 (HPA045797), IRF3 (ab25950) and IFNβ (ab238675) was performed on tissue microarrays constructed from 18 normal human breast tissue samples and 197 primary BC samples to characterize in-situ protein expression. Positive controls were normal colon, MCF10A cells, testis tissue, MCF-7 cells and normal colon for cGAS, STING, TBK1, IRF3 and IFNβ, respectively. Substitution of primary antibodies with 0.5% normal goat serum served as negative controls. Scoring of extent of the IHC-stained area was 0 for no IHC signal, 1 for 50% of tumor cells. IHC intensity was scored as 0 for no IHC signal, 1 for weak, 2 for moderate, and 3 for strong. A final IHC score was the product of extent score and intensity score, as described [Xia T, et al. Cell reports, 2016]. Categorical classification of high versus low final IHC scores was determined using the median as an unbiased cutoff. Associations between cGAS-STING pathway protein constituents was interrogated by Pearson’s test, and associations between STING pathway IHC expression and breast tumor clinicopathological features were by Chi-square. Results: Among 197 primary BCs, 51.5% were estrogen receptor (ER) positive/ human epidermal growth factor receptor 2 (HER2) negative, 28.4% were HER2 positive and 19.8% were triple negative BC (TNBC). Distinct cGAS-STING pathway expression patterns were observed among three BC subtypes (Table 1). Frequent high expression of cGAS-STING pathway constituents was observed in ER+/HER2- BC. By contrast, high cGAS expression was not associated with high STING expression or effector protein IFNβ in either HER2+ BC, or in TNBC. IRF3 and IFNβ expression was significantly positively associated with hormone receptor status (both P< .001); IFNβ expression was significantly inversely associated with higher grade (P=0.008) and higher mean Ki67 index (18 vs 10, P=0.005). High expression of IFNβ was positively correlated with higher levels of TBK1 and IRF3 (R=0.262 P Citation Format: Yu Zong, Xiaofei Liu, Glen N Barber, Mark D Pegram. cGAS-STING pathway protein expression in human primary breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-17.

Background: Rintodestrant is an orally bioavailable, potent and selective estrogen receptor degrader (SERD) that inhibits estrogen receptor (ER) gene transcription, degrades the ER, and delays tumor proliferation in preclinical models. Preliminary results from Part 1 dose escalation (200-1000 mg once daily) demonstrated that rintodestrant has a favorable safety profile and encouraging antitumor activity in patients (pts) with heavily pretreated ER+/HER2- advanced breast cancer (ABC) (Dees et al., ESMO 2019 [abstract #3587]). Here, we report the pharmacodynamic (PD) analysis in peripheral blood and tumor biopsies from pts who received rintodestrant in Part 1 and 2 (600 and 1000 mg dose expansion) to characterize the pt population and mechanisms of response. Methods: This Phase 1, first-in-human, open-label study evaluated rintodestrant in women with ER+/HER- ABC after progression on endocrine therapy. PD analysis included inhibition of ER target engagement with 18F-fluoroestradiol positron emission tomography (FES-PET), mutational profiling (cell-free DNA [cfDNA]), and circulating tumor cell (CTC) enumeration. Tumor biopsies sampled at baseline and 6 weeks on treatment were evaluated for ER degradation (immunohistochemistry [IHC]) and proliferation (Ki67, IHC) to understand the on-target effects of rintodestrant. Results: As of May 13, 2020, 67 pts had been treated. FES-PET data were obtained in 14 pts and showed a decrease in all pts, with maximum standard uptake values (SUVmax) ranging from 70% to 98% after 4 weeks of rintodestrant monotherapy across all doses. Fifty-nine pts were tested for cfDNA at baseline; 95% (n = 56) harbored ≥1 somatic variant (median = 3 mutations per pt). Among pts with somatic variants, 41% had ESR1 mutations, with D538G being the most common (58%). Additionally, 46% and 42% of pts harbored mutations in TP53 and PIK3CA, respectively, and 10% had mutations in both ESR1 and PIK3CA. Similar clinical benefit rates were observed in wild-type vs ESR1 and/or PIK3CA mutant tumors. An analysis of change of variant allele fraction (VAF) in 55 pts between baseline and 2 weeks of treatment revealed that 58% had a decrease in mean VAF, with a decrease in ESR1 VAF in 16/20 pts that had ESR1 mutations at baseline. Furthermore, of 24 pts who had samples collected at baseline and progression, 16 (67%) developed additional variants (median [range]: 2 [1, 15]), including EGFR, ERBB2, TP53, and ESR1. CTC analysis (n = 45) showed the mean value of Epi+CD45- CTCs decreased from 2.8 cells/mL to 1.8 cells/mL after 8 weeks of treatment. Tumor biopsies were collected in 9 pts (5 received 600 mg and 4 received 1000 mg) at baseline and 6 weeks on treatment. Of the 7/9 pts that had a decrease in the ER H-score (median [range]: -27.8% [-33.8%, -3.4%]), 4 had ≥1 variant in ESR1 at baseline. Overall, 4 pts had a decrease in Ki67, with reductions mostly observed in pts who received 600 mg rintodestrant. Additional analyses, including correlations with clinical response, are ongoing and will be presented. Conclusions: Rintodestrant demonstrated robust ER target engagement on FES-PET, as well as substantial decreases in ER H-score, cfDNA VAF, and Epi+CD45- CTCs. These data, along with promising clinical benefit in pts with heavily pretreated ER+/HER2- ABC, regardless of ESR1 or PIK3CA mutation status, warrant additional investigation of rintodestrant (NCT03455270). Citation Format: Philippe Aftimos, Marina Maglakelidze, Andor WJM Glaudemans, Erika Hamilton, Linnea Chap, Elisabeth de Vries, Catharina Willemien Menke-van der Houven van Oordt, Agnes Jager, E. Claire Dees, Massimo Cristofanilli, Mark Pegram, Susanna Ulahannan, Patrick Neven, Iurie Bulat, Ruhi Rai, Wenli Tao, Sarika Jain, Andrew P Beelen, Jessica A Sorrentino. Pharmacodynamic analysis from a phase 1 study of rintodestrant (G1T48), an oral selective estrogen receptor degrader, in ER+/HER2- locally advanced or metastatic breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD8-07.

Background: Cancer cells overexpress CD47 to evade phagocytic programmed cell removal (PrCR) by macrophages of the innate immune system. Blocking CD47 using magrolimab (Hu5F9-G4), an anti-CD47 humanized monoclonal antibody, works via preventing CD47 signaling via macrophage Sirpα to allow PrCR, as well as using an Fc-receptor mechanism to encourage macrophage-mediated phagocytosis. We have previously shown that magrolimab in combination with tumor-targeting antibodies (e.g. rituximab) further enhances magrolimab’s anti-cancer effects in preclinical models and in the clinic [Advani R, et al. N Engl J Med 2018; 379:1711-1721]. We therefore hypothesized that magrolimab combined with anti-HER2 monoclonal antibody would synergize to promote ADCP in vitro, and HER2+ breast xenograft growth inhibition in vivo. Methods: To test this hypothesis, 1 x 105 CFSE-labeled HER2+ BT474 and SKBR3 cells were plated in 96-well ultra-low attachment plates in serum-free media. Isotype control antibody, trastuzumab, magrolimab, and trastuzumab + magrolimab combination (10µg/ml) were added, and allowed to incubate at 37°C for 30 mins. 5 x 104 human macrophages were then added each well, and were co-cultured for 2 hours. Human macrophages were stained with anti-CD11b, and phagocytosis was determined as the percentage of cells that were CD11b+ and CSFE+ using a BD LSR Fortessa Analyzer. For in vivo tumor xenograft growth kinetics, GFP+/Luciferase+ BT474 cells (1X105) were implanted with 25% Matrigel into the mammary fat pads of 4-8 week-old NOD scid gamma (NSG) female mice. Twenty-five days after engraftment, trastuzumab (100ug) was administered via intraperitoneal (IP) injection weekly, magrolimab 250ug IP was administered every other day, and PBS control was administered IP at 100uL once weekly, and tumor growth was monitored for 17 weeks by bioluminescence (IVIS) after D-luciferin injection, and quantified using Image 4.0. Results: SKBR3 and BT474 parental and Trastuzumab-resistant lines demonstrated significantly increased susceptibility to ADCP when opsonized with combination treatment of trastuzumab + magrolimab (15.34, 95%CI= 12.2 to 16.6) compared to trastuzumab (9.66, 95%CI=1.861 to 7.7579, p = 0.034), or magrolimab alone (10.23, 95%CI=1.254 to 7.037, p = 0.0083). Treatment with magrolimab maintained tumor burden within the starting range but further progressed upon treatment cessation (2.09x109, CI95% = 2801531434 to 15343840962, p = 0.0006). Trastuzumab treatment resulted in lower starting range tumor burden, but also demonstrated progression once treatment was stopped (1.72x106, CI95% = -695208489 to -86402608, p = 0.0052). However, in the combinatorial treatment arm, tumors were significantly below the starting range and did not show signs of tumor progression within the 10-week non-treatment period (8.51x105, CI95%= -311406356 to -66914472, p = < 0.0001). Conclusion: We conclude magrolimab plus trastuzumab cooperate to inhibit HER2+ xenograft growth in vivo, and that treatment effect persists even after treatment is stopped. Our ex vivo data suggests one mechanism to explain the observed tumor growth inhibition is increased susceptibility to ADCP when HER2+ tumors are opsonized by the combination of trastuzumab + magrolimab. Future clinical translation of this combination is warranted. Citation Format: Rosalynd Upton, Dongdong Feng, Allison M Banuelos, Tanuka Biswas, Stephen Willingham, Kevin S Kao, Kelly McKenna, Benyamin Rosenthal, Michal C Tal, Jens-Peter Volkmer, Mark D Pegram, Irving L Weissman. Humanized anti-CD47 monoclonal antibody magrolimab (Hu5F9-G4) plus trastuzumab potentiates antibody-dependent cellular phagocytosis (ADCP), and cooperate to inhibit human HER2+ breast cancer (BC) xenografts growth in vivo [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-06.

Objectives: The key objectives of CONTESSA are to evaluate the efficacy and safety of tesetaxel plus a reduced dose of capecitabine as an all-oral regimen versus capecitabine alone in patients with HER2-, HR+ MBC previously treated with a taxane. Rationale: Tesetaxel is a novel, oral taxane with several properties that make it unique, including: oral administration with a low pill burden; a long (8-day) terminal plasma half-life in humans, enabling infrequent, once-every-3 weeks (Q3W) dosing; no observed hypersensitivity reactions; and significant activity against chemotherapy-resistant breast cancer cell lines. More than 1,000 patients have been treated with tesetaxel in clinical studies. Tesetaxel had encouraging monotherapy activity in a Phase 2 study in 38 patients with HER2-, HR+ MBC, with a confirmed objective response rate (ORR) per RECIST 1.1 of 45% and median progression-free survival (PFS) of 5.4 months (Seidman et al, 2018 ASCO Annual Meeting). Methodology: CONTESSA is a multinational, multicenter, randomized (1:1), Phase 3 registration study comparing tesetaxel (27 mg/m2 on Day 1 of a 21-day cycle) plus a reduced dose of capecitabine (1,650 mg/m2/day on Days 1-14 of a 21-day cycle) to the approved dose of capecitabine alone (2,500 mg/m2/day on Days 1-14 of a 21-day cycle) in patients with HER2-, HR+ MBC who have received no more than one chemotherapy regimen for advanced disease and have received a taxane in the (neo)adjuvant setting. There was no restriction on the disease-free interval following taxane therapy. The primary endpoint is PFS assessed by an Independent Radiologic Review Committee (IRC). CONTESSA was designed with 90% power to detect a 2.5-month improvement in median PFS (HR=0.71). Secondary endpoints are overall survival (OS), ORR and disease control rate. Results: CONTESSA, which enrolled 685 patients, met the primary endpoint of improved PFS as assessed by the IRC. Median PFS was 9.8 months for tesetaxel plus a reduced dose of capecitabine versus 6.9 months for capecitabine alone, an improvement of 2.9 months [HR=0.716 (95% CI: 0.573-0.895); p=0.003]. ORR was 57% for tesetaxel plus a reduced dose of capecitabine versus 41% for capecitabine alone (p=0.0002). OS data are immature. Tesetaxel plus capecitabine was associated with a manageable side effect profile consistent with previous clinical studies. Grade ≥3 treatment-emergent adverse events (TEAEs) that occurred in ≥5% of patients (tesetaxel plus capecitabine vs. capecitabine alone) were: neutropenia (71.2% vs. 8.3%); diarrhea (13.4% vs. 8.9%); hand-foot syndrome (6.8% vs. 12.2%); febrile neutropenia (12.8% vs. 1.2%); fatigue (8.6% vs. 4.5%); hypokalemia (8.6% vs. 2.7%); leukopenia (10.1% vs. 0.9%); and anemia (8.0% vs. 2.1%). TEAEs resulting in treatment discontinuation in ≥1% of patients (tesetaxel plus capecitabine vs. capecitabine alone) were: neutropenia or febrile neutropenia (4.2% vs. 1.5%); neuropathy (3.6% vs. 0.3%); diarrhea (0.9% vs. 1.5%); and hand-foot syndrome (0.6% vs. 2.1%). Treatment discontinuation due to any adverse event occurred in 23.1% of patients treated with tesetaxel plus capecitabine versus 11.9% of patients treated with capecitabine alone. Grade 2 alopecia occurred in 8.0% of patients treated with tesetaxel plus capecitabine versus 0.3% of patients treated with capecitabine alone. Grade ≥3 neuropathy occurred in 5.9% of patients treated with tesetaxel plus capecitabine versus 0.9% of patients treated with capecitabine alone. Conclusion: An all-oral regimen of tesetaxel plus a reduced dose of capecitabine significantly improved PFS versus capecitabine alone. Neutropenia was the most frequent Grade ≥3 TEAE. Rates of clinically significant alopecia and neuropathy were low. Citation Format: Joyce O'Shaughnessy, Lee Schwartzberg, Martine Piccart, Hope S. Rugo, Denise A Yardley, Javier Cortes, Michael Untch, Nadia Harbeck, Gail S. Wright, Igor Bondarenko, John Glaspy, Zbigniew Nowecki, Fadi Kayali, Arlene Chan, Christelle Levy, Mei-Ching Liu, Sung-Bae Kim, Julie Lemieux, Alexey Manikhas, Sara Tolaney, Elaine Lim, Andrea Gombos, Agostina Stradella, Mark Pegram, Peter Fasching, Laszlo Mangel, Vladimir Semiglazov, Veronique Dieras, Luca Gianni, Michael A Danso, Jeff Vacirca, Stew Kroll, Joseph O'Connell, Kevin Tang, Thomas Wei, Andrew Seidman. Results from CONTESSA: A phase 3 study of tesetaxel plus a reduced dose of capecitabine versus capecitabine alone in patients with HER2-, hormone receptor + (HR+) metastatic breast cancer (MBC) who have previously received a taxane [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr GS4-01.

Introduction T-DM1 is indicated for the treatment of advanced HER2-positive MBC in patients who previously received trastuzumab and a taxane (separately or in combination) based on data from the phase 3 EMILIA study (BO21977/TDM4370g; NCT00829166). In the primary PFS and second interim OS analyses, respectively, T-DM1 significantly improved PFS (median 9.6 vs 6.4 months; HR=0.65; 95% CI, 0.55–0.77; p Methods EMILIA was a randomized, open-label study of patients with centrally confirmed HER2-positive (IHC3+ and/or FISH amplification ratio ≥2.0), unresectable, locally advanced or MBC, previously treated with trastuzumab and a taxane. Patients were randomized 1:1 to T-DM1 (3.6 mg/kg IV every 3 weeks) or X (1000 mg/m2 PO twice daily, days 1–14 every 3 weeks) plus L (1250 mg PO daily). The final OS analysis was to be conducted following 632 events, and these results are descriptive only. Since the OS efficacy boundary (HR Results From Feb 2009 to Oct 2011, 991 patients were randomized to T-DM1 (n=495) or XL (n=496). Patient disposition by the data cutoff (31 Dec 2014) is shown in Table 1. OS was longer with T-DM1 vs XL (median OS 29.9 vs 25.9 months; HR=0.75; 95% CI, 0.64–0.88; p=0.0003). In a sensitivity analysis, which censored crossover patients at the time of switching from XL to T-DM1, the HR was 0.69 (95% CI, 0.59–0.82; p Table 1. Patient disposition. T-DM1 (n=495)XL (n=496)Median treatment duration, months7.6X: 5.3 L: 5.5Median duration of follow-up, months47.841.9Discontinued study, n (%)364 (74)404 (82)Crossover, n (%) Per protocolaNot applicable136 (27)Non-protocol therapybX: 252 (54)X: 53 (11) L: 224 (48)L: 74 (15)aMedian duration of follow-up among per-protocol crossover patients was 24.1 months.bBy investigator choice after study treatment discontinuation; X or L could be given in combination with each other or other agents after progression. Table 2. Safety summary in patients who received ≥1 dose of study treatment.n (%)T-DM1 (n=490)XL (n=488)Grade ≥3 AEs233 (47.6)291 (59.6)Serious AEs91 (18.6)99 (20.3)AEs leading to dose reduction91 (18.6)X: 205 (42.0) L: 98 (20.1) Conclusions This final analysis of EMILIA shows an OS benefit of T-DM1 compared with XL. While median drug exposure was longer with T-DM1 than XL, T-DM1 was associated with fewer grade ≥3 AEs and AEs leading to dose reduction compared with XL. These final OS results confirm that T-DM1 treatment improved survival, even in the presence of treatment crossover, and reaffirm T-DM1 as the standard of care in patients with previously treated HER2-positive MBC. Citation Format: Diéras V, Miles D, Verma S, Pegram M, Welslau M, Baselga J, Krop I, Blackwell K, Kang B, Xu J, Green M, Gianni L. Trastuzumab emtansine improves overall survival versus capecitabine plus lapatinib in patients with previously treated HER2-positive advanced breast cancer: Final results from the phase 3 EMILIA study. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-14-01.

Women with triple-negative breast cancer have worse prognosis compared to other breast cancer subtypes. Acquired drug resistance remains to be an important reason influencing triple-negative breast cancer treatment efficacy. A prevailing theory postulates that the cancer resistance and recurrence results from a subpopulation of tumor cells with stemness program, which are often insensitive to cytotoxic drugs such as cisplatin. Recent studies suggested that niclosamide, an anti-helminthic drug, has potential therapeutic activities against breast cancer stem cells, which prompts us to determine its roles on eliminating cisplatin-resistant cancer cells. Hence, we established a stable cisplatin-resistant MDA-MB-231 cell line (231-CR) through continuously exposure to increasing concentrations of cisplatin (5-20 μmol/l). Interestingly, 231-CR exhibited properties associated to epithelial-mesenchymal transition with enhanced invasion, preserved proliferation, increased mammosphere formation, and reduced apoptosis compared to naive MDA-MB-231 sensitive cells (231-CS). Importantly, niclosamide or combination with cisplatin inhibited both 231-CS and 231-CR cell proliferation in vitro. In addition, niclosamide reversed the EMT phenotype of 231-CR by downregulation of snail and vimentin. Mechanistically, niclosamide treatment in combination with or without cisplatin significantly inhibited Akt, ERK, and Src signaling pathways. In vivo study showed that niclosamide or combination with cisplatin could repress the growth of xenografts originated from either 231-CS or 231-CR cells, with prominent suppression of Ki67 expression. These findings suggested that niclosamide might serve as a novel therapeutic strategy, either alone or in combination with cisplatin, for triple-negative breast cancer treatment, especially those resistant to cisplatin.

1040 Background: Despite advances, pretreated HER2+ MBC remains incurable with ongoing need for new therapies. Investigational M has similar HER2 binding and antiproliferative effects as T. Relative to T, M Fc engineering increases binding affinity for both variants of activating Fc receptor (FcR) CD16A and decreases affinity for inhibitory FcR CD32B, coordinately activating innate and adaptive immunity. In a Phase 3 (P3) trial, M prolonged PFS over T (Table). Second interim OS results from Sept 2019 also favor M (hazard ratio [HR], 0.89; 95% CI 0.69–1.13; nominal P=0.326). Methods: SOPHIA (NCT02492711), an open-label P3 trial, enrolled pts with HER2+ MBC after pertuzumab and 1–3 lines of prior treatment (Tx) for MBC. Randomization was 1:1 to M (15 mg/kg IV q3w + Ctx) or T (6 [8 for loading dose] mg/kg IV q3w + Ctx), stratified by met sites (≤2, >2), lines of Tx for met disease (≤2, >2), and Ctx choice, including capecitabine (Cap), eribulin (Eri), gemcitabine (Gem), or vinorelbine (Vin). Primary endpoints were central blinded PFS and OS, assessed sequentially using the stratified log-rank test. Results: Investigator chemotherapy choices and results by chemotherapy are shown in the table. Subjects receiving Eri and Gem had the lowest PFS hazards ratios (HRs), favoring M over T, although no statistical significance of individual chemotherapy subgroups was seen. There was variable toxicity among Ctx subgroups, and fewer subjects receiving Cap had Ctx related Grade 3 or higher (>=Gr 3) AEs. In this unblinded study, more subjects on M than T in all subgroups discontinued Ctx while continuing study antibody. Conclusions: In combination with chemotherapy in pretreated HER2+ MBC, M improved PFS over T. Safety was manageable in all Ctx subgroups. Differences among HRs for chemotherapy subgroups may be driven by selection bias and/or sensitivity differences. Clinical trial information: NCT02492711 . [Table: see text]

578 Background: SB3 was approved in the US and EU as a biosimilar of reference trastuzumab (TRZ). Here, we report 4-year cardiac safety and survival outcomes. Methods: After completing neoadjuvant-adjuvant therapy in patients with HER2 positive early breast cancer, patients from selected countries participated in a 5-year follow-up study of a phase III trial (Pivot et al. Eur J Cancer 2019). The aim was to observe long-term cardiac safety and survival. EFS and OS were analyzed in subgroups by ADCC status within TRZ in ad-hoc analyses. Results: Of 875 patients randomized in the phase III trial, 367 patients (SB3, N=186; TRZ, N=181) were enrolled in the follow-up study. The median follow-up was 53 months. During the follow-up, the incidence of asymptomatic significant left ventricular ejection fraction (LVEF) decrease was low (SB3, n=1; TRZ, n=2), with all patients recovering with LVEF ≥ 50%. No cases of symptomatic congestive heart failure, cardiac death, or other significant cardiac condition were reported. 4-year EFS rates were 83.4% for SB3 and 80.7% for TRZ with a HR of 0.77 [95% CI 0.47, 1.27]. 4-year OS rates were 94.3% for SB3 and 89.6% for TRZ with a HR of 0.53 [95% CI 0.24, 1.16]. From ad-hoc analysis, a difference in EFS and OS was seen between Non-drifted TRZ and Drifted TRZ; Difference between SB3 and Non-drifted TRZ was not statistically significant. Conclusions: In a subset of patients from the phase III trial, comparable long-term cardiac safety and survival at 4-year supports biosimilarity between SB3 and TRZ. Ad-hoc analysis results by ADCC status suggest a possible correlation between ADCC and clinical efficacy. Further follow-up is needed. Clinical trial information: NCT02771795 . [Table: see text]

To provide an overview of clinical data supporting the use of cyclin-dependent kinases 4 and 6 (CDK 4/6) inhibitors in the treatment of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−), metastatic breast cancer (mBC), from the perspective of the practicing oncologist community. A recent roundtable discussion was convened by The Breast Cancer Therapy Expert Group (BCTEG) to review existing data on this topic and its impact on their current practice. Level 1 evidence now supports use of a CDK 4/6 inhibitor in combination with endocrine therapy for patients with HR+, HER2−, mBC. Currently, there are no biomarkers that reliably define patients who will, or will not, benefit from the addition of a CDK 4/6 inhibitor to their endocrine therapy. Additional research is needed to identify the optimal sequencing of CDK 4/6 inhibitors in relation to other therapies as well as the optimal duration of therapy; at present, evidence suggests that use in the upfront setting is better than waiting for a later line of therapy, or adding after endocrine therapy has started. Thus far, three CDK 4/6 inhibitors—palbociclib, ribociclib, and more recently, abemaciclib—have been approved for use in the setting of HR+, HER2−, mBC. The degrees to which these agents differ in terms of CDK4/6 affinity, side-effect profiles, dosing, degree of central nervous system (CNS) penetration, optimal use in combination with antiestrogen therapy, and across other subsets of breast cancer, remain an active area of investigation.

In addition to canonical oncoproteins, truncated isoforms and proteolysis products are implicated in both drug resistance and disease progression. In HER2-positive breast tumors, expression of truncated HER2 isoforms resulting from alternative translation and/or carboxy-terminal fragments (CTFs) resulting from proteolysis (collectively, t-erbB2) have been associated with shortened progression-free survival of patients. Thus, to advance clinical pathology and inform treatment decisions, we developed a high-selectivity cytopathology assay capable of distinguishing t-erbB2 from full-length HER2 expression without the need for isoform-specific antibodies. Our microfluidic, single-cell western blot, employs electrophoretic separations to resolve full-length HER2 from the smaller t-erbB2 in each ~28 pL single-cell lysate. Subsequently, a pan-HER2 antibody detects all resolved HER2 protein forms via immunoprobing. In analysis of eight breast tumor biopsies, we identified two tumors comprised of 15% and 40% t-erbB2-expressing cells. By single-cell western blotting of the t-erbB2-expressing cells, we observed statistically different ratios of t-erbB2 proteins to full-length HER2 expression. Further, target multiplexing and clustering analyses scrutinized signaling, including ribosomal S6, within the t-erbB2-expressing cell subpopulation. Taken together, cytometric assays that report both protein isoform profiles and signaling state offer cancer classification taxonomies with unique relevance to precisely describing drug resistance mechanisms in which oncoprotein isoforms/fragments are implicated., Breast cancer: A precision test for truncated oncoproteins in single cells A single-cell western blot provides a simple way of studying whether a cancer-related protein found in breast tumors has transcriptionally or post-translationally modified to a truncated form, which is implicated in resistance to targeted therapies. The microfluidic assay, developed by Amy E. Herr from the University of California, Berkeley, USA, and colleagues at Stanford University, involves first dissociating a breast tumor, then isolating each tumor cell in cell-sized well on a microscope slide. Isolated in the well, each cell is broken up and HER2 proteins are size-separated via single-cell electrophoresis, before being immobilized and finally detected with a fluorescent probe that binds to both the full-length and truncated HER2 proteins. Herr’s team assayed eight patient samples and identified two tumor samples with mixed populations of full-length and truncated HER2 proteins, a finding with therapeutic and prognostic relevance for patients.

This paper deals with specific targeting of the prodrug/enzyme regimen, CNOB/HChrR6, to treat a serious disease, namely HER2+ human breast cancer with minimal off-target toxicity. HChrR6 is an improved bacterial enzyme that converts CNOB into the cytotoxic drug MCHB. Extracellular vesicles (EV) were used for mRNA-based HchrR6 gene delivery: EVs may cause minimal immune rejection, and mRNA may be superior to DNA for gene delivery. To confine HChrR6 generation and CNOB activation to the cancer, the EVHB chimeric protein was constructed. It contains high-affinity anti-HER2 scFv antibody (ML39) and is capable of latching on to EV surface. Cells transfected with EVHB-encoding plasmid generated EVs displaying this protein (“directed EVs”). Transfection of a separate batch of cells with the new plasmid, XPort/HChrR6, generated EVs containing HChrR6 mRNA; incubation with pure EVHB enabled these to target the HER2 receptor, generating “EXO-DEPT” EVs. EXO-DEPT treatment specifically enabled HER2-overexpressing BT474 cells to convert CNOB into MCHB in actinomycin D–independent manner, showing successful and specific delivery of HChrR6 mRNA. EXO-DEPTs—but not undirected EVs—plus CNOB caused near-complete growth arrest of orthotopic BT474 xenografts in vivo, demonstrating for the first time EV-mediated delivery of functional exogenous mRNA to tumors. EXO-DEPTs may be generated from patients' own dendritic cells to evade immune rejection, and without plasmids and their potentially harmful genetic material, raising the prospect of clinical use of this regimen. This approach can be used to treat any disease overexpressing a specific marker. Mol Cancer Ther; 17(5); 1133–42. ©2018 AACR.

Purpose: Management of breast cancer is a rapidly evolving field, and, although evidence-based guidelines are available for clinicians to provide direction on critical issues in patient care, clinicians often left to address these issues in the context of community practice situations with their patients. These include the patient’s comorbid conditions, actual versus perceived benefit of treatments, patient’s compliance as well as financial/reimbursement issues, and long-term tolerability of therapy. Methods: A meeting of global oncology experts was convened in January 2017 with the belief that there is a gap in clinical practice guidance on several fundamental issues in breast cancer care, particularly in the community setting, where oncologists may encounter multiple tumor types. The goal was to discuss some of the most important questions in this area and provide some guidance for practicing oncologists. Results: Topics addressed included risk of contralateral breast cancer recurrence in patients with estrogen receptor-positive early breast cancer who have undergone 5 years of adjuvant endocrine therapy, adverse events associated with endocrine therapy and their management, emergent data on adjuvant bisphosphonate therapy and its apparent benefit in reducing breast cancer recurrence, recent findings of extended adjuvant endocrine therapy trials, and the use of currently available genomic biomarker tests as a means of further informing treatment decisions. Conclusions: A summary of the discussion on these topics and several ‘expert opinion statements’ are provided herein in an effort to convey the collective insights of the panel as it relates to current standard practice.

Background The SERD fulvestrant is a well-established therapy for ER+/HER2- ABC. However, its intramuscular route of administration may be painful and limits systemic exposure. G1T48 is a highly potent and efficacious oral SERD in both mutant and WT ESR1 preclinical models with the potential to achieve higher exposure and provide clinical benefit in patients with ER+ ABC. Methods Postmenopausal women with ER+/HER2- ABC following progression on endocrine therapy are eligible for this 3 + 3 dose escalation and expansion study. Patients receive G1T48 QD until disease progression or unacceptable toxicity. The objectives are to evaluate DLTs, safety, tolerability, PK, ER target engagement via [18F] FES-PET, and anti-tumor efficacy, and to determine the recommended phase 2 dose. Results Currently, 11 patients (mean age 64 years) have received G1T48 doses ranging from 200-800 mg QD for up to 7 months. Prior lines (median of 3) included chemotherapy in 45%, fulvestrant in 91%, and CDK4/6i in 54% of patients. G1T48 is well tolerated: no DLTs, G1T48-related SAEs, or withdrawals due to an AE have occurred. The most common Gr 1/2 G1T48-related TEAEs are diarrhea, headache, hot flush, and nausea (27% each) with a single Gr 3 TEAE (fatigue) and no Gr 4 TEAEs. G1T48 exposure increased with dose (200 to 800 mg), and minimum to moderate accumulation of G1T48 was observed following repeated doses. Median maximum standard tumor [18F] FES-PET uptake values decreased (ranging from 70% (200 mg) to 88% (600 mg)) after 4 weeks of treatment. Of 6 response evaluable patients (RECIST v1.1), 1 patient had a PR (600 mg, prior palbociclib/fulvestrant) and 1 patient had SD ≥ 24 weeks (200 mg, prior abemaciclib/fulvestrant). Conclusions The oral SERD G1T48 is well tolerated with no DLTs reported to date in patients with ER+/HER2- ABC. Early efficacy, safety, PK, and FES-PET data are encouraging, and support continued dose escalation followed by expansion. Updated safety, anti-tumor activity, and cfDNA data will be presented (NCT#03455270). Clinical trial identification NCT03455270. Legal entity responsible for the study G1 Therapeutics, Inc. Funding G1 Therapeutics. Disclosure E.C. Dees: Research grant / Funding (institution): G1 Therapeutics; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Merck; Research grant / Funding (institution): H3Biosciences; Research grant / Funding (institution): Lilly; Research grant / Funding (institution): Cerulean; Research grant / Funding (institution): Meryx; Advisory / Consultancy, Research grant / Funding (institution): Novartis. P.G. Aftimos: Advisory / Consultancy: Boehringer Ingleheim; Advisory / Consultancy: Macrogenics; Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Roche; Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Novartis; Advisory / Consultancy: Amcure; Honoraria (self), Research grant / Funding (institution): Synthon; Honoraria (self), Travel / Accommodation / Expenses: Amgen; Research grant / Funding (institution), Travel / Accommodation / Expenses: MSD; Research grant / Funding (institution), Travel / Accommodation / Expenses: Pfizer; Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Lilly; Research grant / Funding (institution): Radius; Research grant / Funding (institution): Servier. C.W. Menke-van der Houven van Oordt: Advisory / Consultancy: G1 Therapeutics; Advisory / Consultancy: Novartis. E.G..E. De Vries: Research grant / Funding (institution): G1 Therapeutics; Advisory / Consultancy: NSABP; Advisory / Consultancy: Sanofi; Advisory / Consultancy: Daiichi Sankyo; Advisory / Consultancy: Pfizer; Research grant / Funding (institution): Amgen; Research grant / Funding (institution): Genentech; Research grant / Funding (institution): Roche; Research grant / Funding (institution): Chugai; Research grant / Funding (institution): CytomX Therapeutics; Research grant / Funding (institution): Nordic Nanovector; Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Bayer; Research grant / Funding (institution): Synthon. M.D. Pegram: Advisory / Consultancy: G1 Therapeutics. J. Xiao: Full / Part-time employment: G1 Therapeutics. C. Sipes: Full / Part-time employment: G1 Therapeutics. C. Li: Full / Part-time employment: G1 Therapeutics. J.A. Sorrentino: Full / Part-time employment: G1 Therapeutics. R. Malik: Full / Part-time employment: G1 Therapeutics. A.P. Beelen: Full / Part-time employment: G1 Therapeutics. All other authors have declared no conflicts of interest.

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Pore-gradient microgel arrays enable thousands of parallel high-resolution single-cell protein electrophoresis separations for targets accross a wide molecular mass (25-289 kDa), yet within 1 mm separation distances. Dual crosslinked hydrogels facilitate gel-pore expansion after electrophoresis for efficient and uniform immunoprobing. The photopatterned, light-activated, and acid-expandable hydrogel underpins single-cell protein analysis, here for oncoprotein-related signaling in human breast biopsy.

ABSTRACT Kyoto Breast Cancer Consensus Conference, Kyoto, Japan, 18–20 February 2014 The loco-regional management of breast cancer is increasingly complex with application of primary systemic therapies, oncoplastic techniques and genetic testing for breast cancer susceptibility. Personalization of loco-regional treatment is integral to optimization of breast cancer care. Clinical and pathological tumor stage, biological features and host factors influence loco-regional treatment strategies and extent of surgical procedures. Key issues including axillary staging, axillary treatment, radiation therapy, primary systemic therapy (PST), preoperative hormonal therapy and genetic predisposition were identified and discussed at the Kyoto Breast Cancer Consensus Conference (KBCCC2014). In the first of a two part conference scene, consensus recommendations for axillary management are presented and focus on the following topics: indications for completion axillary lymph node dissection in primary surgical patients with ≤2 macrometastases or any sentinel nodal deposits after PST; the timing of sentinel lymph node biopsy in the context of PST; use of axillary irradiation as a component of primary treatment plans and the role of intraoperative node assessment in the post-Z0011 era.

ABSTRACT Kyoto Breast Cancer Consensus Conference, Kyoto, Japan, 18–20 February 2014 The loco-regional management of breast cancer is increasingly complex with application of primary systemic therapies, oncoplastic techniques and genetic testing for breast cancer susceptibility. Personalization of loco-regional treatment is integral to optimization of breast cancer care. Clinical and pathological tumor stage, biological features and host factors influence loco-regional treatment strategies and extent of surgical procedures. Key issues including axillary staging, axillary treatment, radiation therapy, primary systemic therapy (PST), preoperative hormonal therapy and genetic predisposition were identified and discussed at the Kyoto Breast Cancer Consensus Conference (KBCCC2014). In the second of a two part conference scene, consensus recommendations for radiation treatment, primary systemic therapies and management of genetic predisposition are reported and focus on the following topics: influence of both clinical response to PST and stage at presentation on recommendations for postmastectomy radiotherapy; use of regional nodal irradiation in selected node-positive patients and those with adverse pathological factors; extent of surgical resection following downstaging of tumors with PST; use of preoperative hormonal therapy in premenopausal women with larger, node-negative luminal A-like tumors and managing increasing demands for contralateral prophylactic mastectomy in patients with a unilateral sporadic breast cancer.

Patients with HER2+ breast cancer treated with trastuzumab and chemotherapy have superior survival compared with patients treated with chemotherapy alone. Polymorphisms within FCGR2A and FCGR3A are associated with binding affinity of natural killer cells to the IgG1 portion of trastuzumab, and a polymorphism in FCGR2B (I232T) is associated with impaired regulatory activity. The association of these polymorphisms with clinical response among trastuzumab-treated patients is equivocal, with both positive and negative associations. We performed genotyping analysis on the FCGR3A V158F, FCGR2A R131H, and FCGR2B I232T polymorphisms in 1,325 patients from the N9831 clinical trial. Patients in arm A (N = 419) received chemotherapy only. Patients in arms B (N = 469) and C (N = 437) were treated with chemotherapy and trastuzumab (sequentially in arm B and concurrently in arm C). Using log-rank test and Cox proportional hazard models, we compared disease-free survival (DFS) among genotypic groups within pooled arms B/C. We found no differences in DFS between trastuzumab-treated patients who had the FCGR3A 158 V/V and/or FCGR2A 131 H/H high-affinity genotypes and patients without those genotypes. Furthermore, there was no significant interaction between FCGR3A and FCGR2A and treatment. However, there was a difference in DFS for FCGR2B I232T, with I/I patients deriving benefit from trastuzumab (P < 0.001), compared with the T carriers who did not (P = 0.81). The interaction between FCGR2B genotype and treatment was statistically significant (P = 0.03). Our analysis did not reveal an association between FcγR high-affinity genotypes and outcomes. However, it seems that the FCGR2B inhibitory gene may be predictive of adjuvant trastuzumab benefit. Cancer Immunol Res; 2(10); 962–9. ©2014 AACR.

Breast cancer is the most common malignancy in women in the United States and is second only to lung cancer as a cause of cancer death. The overall management of breast cancer includes the treatment of local disease with surgery, radiation therapy, or both, and the treatment of systemic disease with cytotoxic chemotherapy, endocrine therapy, biologic therapy, or combinations of these. The NCCN Guidelines specific to management of large clinical stage II and III tumors are discussed in this article. These guidelines are the work of the members of the NCCN Breast Cancer Panel. Expert medical clinical judgment is required to apply these guidelines in the context of an individual patient to provide optimal care. Although not stated at every decision point of the guidelines, patient participation in prospective clinical trials is the preferred option of treatment for all stages of breast cancer.

580 Background: SB3 is an approved biosimilar of reference trastuzumab (TRZ). At additional 2-year follow-up after completing neoadjuvant and adjuvant treatment, there was a difference in event-free survival (EFS), but no difference in overall survival (OS) between SB3 and TRZ. Upon monitoring quality attributes of TRZ, a marked downward shift in antibody-dependent cell-mediated cytotoxicity activities (ADCC) was observed in TRZ lots with expiry dates from Aug 2018 to Dec 2019. Some of the lots were used in the Phase III study. This is a post-hoc analysis of EFS and OS by ADCC status from a 3-year follow-up to investigate the difference in EFS between SB3 and TRZ. Methods: After completion of neoadjuvant and adjuvant therapy in patients with HER2 positive early breast cancer, patients from selected countries participated in a 5-year follow-up study (NCT02771795). Within the TRZ group, patients exposed to at least one shifted ADCC lot and those never exposed to shifted ADCC lot during neoadjuvant period were considered as “Exposed” and “Unexposed,” respectively. EFS and OS after 3-year follow-up was analyzed by ADCC status in the long-term follow-up set. Results: 367 patients (SB3, N = 186; TRZ, N = 181) were enrolled in the follow-up study. Within TRZ, 55 patients were Unexposed and 126 patients were Exposed. At a median follow-up duration of 40.8 months in SB3 and 40.5 months in TRZ, 3-year EFS rates were 92.5% in SB3, 94.5% in Unexposed, and 82.5% in Exposed and OS rates were 97.0%, 100%, and 90.6%, respectively. Exposed was associated with decreased EFS compared to Unexposed (HR 0.14, 95% CI 0.04-0.51, p= 0.003). There was a trend of decreased OS in Exposed compared to Unexposed, however, there was no significant difference (HR 0.14, 95% CI 0.02-1.15, p= 0.068). Between SB3 and Unexposed, no difference was observed in EFS (HR 1.06, 95% CI 0.33-3.44, p= 0.923), or OS (HR 0.54, 95% CI 0.05-5.44, p= 0.600). Conclusions: Within the TRZ group, Exposed showed significantly lower EFS compared to Unexposed, and a similar trend was observed in OS with no statistical significance. Between SB3 and Unexposed, no significant difference in EFS or OS was observed. Clinical trial information: NCT02771795.

1000 Background: Pretreated HER2+ MBC lacks a defined standard of care, although T is commonly used. M has similar HER2 binding and antiproliferative effects as T. By contrast, M’s Fc region is engineered to increase affinity for both alleles of the activating Fc receptor (FcR), CD16A, and decrease affinity for the inhibitory FcR, CD32B. The low affinity CD16A-158F allele (~85% of population) has been associated with diminished clinical response to T. In a Phase 1 trial, M demonstrated acceptable safety, anti-tumor activity, and evidence of HER2-specific antibody and T-cell responses. Methods: SOPHIA (NCT02492711), a randomized, open-label P3 trial, enrolled pts with HER2+ MBC after pertuzumab and 1–3 lines of prior Tx for MBC. Pts were randomized 1:1 to M (15 mg/kg IV q3w + C) or T (6 [8 for loading dose] mg/kg IV q3w + C), stratified by met sites (≤2, > 2), lines of Tx for met disease (≤2, > 2), and C choice (standard dose capecitabine, eribulin, gemcitabine, or vinorelbine). Primary endpoints are central blinded PFS and OS, assessed sequentially using the stratified log-rank test. Objective response rate (ORR) was a secondary endpoint. 257 PFS events were required to provide 90% power to show PFS superiority at 2-sided α = 0.05. Results: Intent-to-treat analysis (536 pts: M 266; T 270) occurred after 265 PFS events. M prolonged PFS over T (median 5.8 vs 4.9 mo, hazard ratio [HR], 0.76; 95% CI, 0.59–0.98; P= 0.033). Treatment effects were more pronounced in pts with CD16A genotypes containing a 158F allele (median PFS 6.9 vs 5.1 mo, HR, 0.68; 95% CI, 0.52–0.90; P= 0.005). In 524 pts with baseline measurable disease (M 262; T 262), ORR was higher with M (22%; 95% CI, 17.3-27.7%) vs T (16%; 95% CI 11.8-21.0%). Safety profiles were comparable in 529 pts who received study therapy. Grade ≥3 AEs and serious AEs occurred in 138 (52%) and 39 (15%) vs 128 (48%) and 46 (17%) pts on M vs T, respectively. PFS data cutoff: 10/10/18. Conclusions: In combination with chemotherapy in pretreated HER2+ MBC, M improves PFS over T with comparable safety. CD16A genotyping suggests a differential benefit in patients with a 158F allele. OS data are maturing. Clinical trial information: NCT02492711.

TPS1107 Background: Chemotherapy treatments with robust efficacy that preserve quality of life are needed. Tesetaxel (T) is a novel, oral taxane that has potential advantages over currently available taxanes, including: oral administration with a low pill burden and Q3W dosing regimen; no observed hypersensitivity reactions; preclinical evidence of CNS penetration; and improved activity against chemotherapy-resistant tumors. Over 600 pts have been treated with T in clinical studies. T had robust monotherapy activity in a Phase 2 study in 38 pts with HER2-, HR+ MBC who received T Q3W, with a confirmed ORR per RECIST 1.1 of 45% and median PFS of 5.4 mo. The confirmed ORR in taxane-pretreated pts was 45%. Preclinical and clinical studies suggest that reducing the dose of capecitabine (C) in combination with a taxane may result in reduced toxicity without reduction in efficacy. Preclinical data also suggest that T may penetrate the brain at clinically relevant concentrations. CONTESSA investigates T plus a reduced dose of C as an all-oral regimen in HER2-, HR+ LA/MBC, with revised eligibility criteria to allow inclusion of pts with CNS metastases. Methods: CONTESSA is a 600-pt, multinational, multicenter, randomized (1:1), Phase 3 registration study comparing T (27 mg/m2 on Day 1 of a 21-day cycle) plus a reduced dose of C (1,650 mg/m2/day on Days 1-14 of a 21-day cycle) to the approved dose of C alone (2,500 mg/m2/day on Days 1-14 of a 21-day cycle) in pts with HER2-, HR+ LA/MBC previously treated with a taxane in the (neo)adjuvant setting. The protocol was newly amended to allow pts with known CNS metastases. The primary endpoint is PFS assessed by an Independent Radiologic Review Committee (IRC). CONTESSA is 90% powered to detect a 42% improvement in PFS (HR = 0.71). Secondary endpoints are OS, ORR, and disease control rate. Enrollment began in Dec 2017. Following review in Jan 2019, the Independent Data Monitoring Committee recommended that the Study continue as planned. Clinical trial information: NCT03326674.

Introduction The antibody-drug conjugate trastuzumab emtansine (T-DM1) combines the antitumor properties of trastuzumab (H) with the cytotoxic agent DM1 via a stable linker. T-DM1 prolonged PFS and OS vs standard therapy in a phase 3 study of patients (pts) with HER2-positive metastatic breast cancer (MBC) previously treated with H and a taxane. Preclinical data suggest synergy when T-DM1 is combined with paclitaxel (T) or pertuzumab (P). In the phase 1b study TDM4652g, the maximum tolerated doses of T-DM1 + T ± P were defined. Here we present results from the phase 2a expansion, which further explored feasibility and safety. Methods TDM4652g is a phase 1b/2a open-label study of pts with HER2-positive locally advanced or MBC. Pts had no prior T-DM1 or P, no baseline peripheral neuropathy (PN; phase 2a only), and had LVEF ≥50%. Pts in phase 2a were randomized to T-DM1 3.6 mg/kg q3w + T 80 mg/m2 qw ± P 840 mg loading dose [LD], then 420 mg q3w. The primary objective, feasibility, was assessed by the percent of evaluable pts receiving ≥12 doses of T within 15 weeks of cycle 1, day 1, and those receiving 12 consecutive weeks of T. Results Forty-four pts were enrolled (T-DM1 + T, n = 22; T-DM1 + T + P, n = 22); the data snapshot date was May 23, 2013. Median age was 52.5 years (range, 35–81); median number of prior agents for MBC was 6 (range, 0–12). 43 (98%) pts had previously received H, and 36 (82%) pts had received taxane therapy. Median dose intensities were T-DM1, 94% (range 54–105); T, 50% (range 9–100) and P, 100% (range 67–100). 2 pts were not evaluable for feasibility (progressive disease [PD] before receiving 12 doses of T). 21/42 (50%) pts received ≥12 doses of T within 15 weeks; 6/42 (14%) pts received 12 consecutive doses by week 12, and 33/42 (79%) pts received ≥8 doses within 12 weeks. Grade 3/4 adverse events (AEs) were reported for 18 (82%) and 17 (77%) pts in the T-DM1 + T and T-DM1 + T + P groups, respectively (see Table for AEs and best responses). Ten pts discontinued early due to PD (n = 6), PD-related death (n = 2), AEs (n = 1), or withdrawal from the study (n = 1). 21 pts discontinued T due to AEs, most commonly PN (n = 12). Grade 3/4 AEs occurring in >1 patientAE, n (%)All patients (N = 44)TDM1 3.6 mg/kg q3w + T 80 mg/m2 qw (n = 22)TDM1 3.6 mg/kg q3w + T 80 mg/m2 qw + P 840 mg LD, 420 mg q3w (n = 22)Neutropenia10 (23)6 (27)4 (18)Peripheral neuropathy9 (20)3 (14)6 (27)Fatigue6 (14)3 (14)3 (14)Thrombocytopenia6 (14)5 (23)1 (5)Anemia3 (7)2 (9)1 (5)Abdominal pain2 (5)2 (9)0Decreased hemoglobin2 (5)1 (5)1 (5)Muscosal inflammation2 (5)1 (5)1 (5)Muscular weakness2 (5)02 (9)Nausea2 (5)1 (5)1 (5)Best response,* n (%)CR2 (5)1 (5)1 (5)CR confirmed1 (2)1 (5)0PR27 (61)13 (59)14 (64)PR confirmed8 (18)3 (14)5 (23)SD10 (23)6 (27)4 (18)PD3 (7)1 (5)2 (9)*At any time point with responses ordered CR>PR>SD>PD. Conclusions Overall, 50% of pts received ≥12 doses of T within 15 weeks. Adding P to the combination of T-DM1 + T did not appear to increase the incidence of grade 3/4 AEs. Data support further investigation of T-DM1 + T ± P in larger studies in early breast cancer. Final data from all phase 2a patients will be available for the full report. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-12-09.

ERBB2 gene amplification occurs in ∼20% of human breast cancers (BC) and is associated with an adverse clinical prognosis, indicating that it may be playing a critical role in disease pathogenesis. Therapeutic strategies targeting pathologic ERBB2 overexpression have revolutionized the diagnosis and treatment of BC. Indeed, humanized anti-ERBB2 antibodies, small molecule ERBB2 kinase inhibitors and ERBB2-targeting antibody-drug conjugates have proven safety and efficacy based upon evidence from randomized phase III clinical trials. Recent progress in targeting ERBB2 alteration will be reviewed, with focus on data that has informed changes in clinical practice for the treatment of BC.

Triple-negative breast cancers comprise about 20 % of breast cancers. They have poor prognosis and have no standard therapy. The aim of this study was to evaluate pathologic complete response (pCR), progression-free survival (PFS), and overall survival (OS) in patients with TNBC treated with neoadjuvant platinum-based chemotherapy. This is a retrospective study of one hundred and forty-four women with TNBC treated with neoadjuvant platinum-containing chemotherapy for locally advanced breast cancer at the University of Miami between January 1, 1999, and January 1, 2011. The medical record was reviewed to obtain data on clinical characteristics, including ethnicity, race, age, clinical stage, treatment regimen, and vital status. This study was approved by the University of Miami IRB. All patients had locally advanced breast cancer with at least one of the following features at presentation: T3, T4, N2, and N3. The mean tumor size by palpation was 9.4 cm. The clinical T-stage at presentation was 1.4 % T1, 8.3 % T2, 52.8 % T3, and 37.5 % T4 (19.4 % T4d). The nodal status by physical exam at presentation was 23 % N0, 37.5 % N1, 34 % N2, and 5.5 % N3. pCR in breast and axilla was seen in 31 %. PFS and OS were 55 and 59 %, respectively, at 7 years. Cisplatin offered a survival advantage over carboplatin in both PFS (P = 0.007) and OS (P = 0.018). Node positivity was the most important predictor of survival. Cisplatin/docetaxel neoadjuvant therapy was well tolerated and an effective therapy in locally advanced TNB.

The addition of trastuzumab to chemotherapy extends survival among patients with HER2+ breast cancer. Prior work showed that trastuzumab and chemotherapy augments HER2 extracellular domain (ECD)-specific antibodies. The current study investigated whether combination therapy induced immune responses beyond HER2-ECD and, importantly, whether those immune responses were associated with survival. Pretreatment and posttreatment sera were obtained from 48 women with metastatic HER2+ breast cancer on NCCTG (now Alliance for Clinical Trials in Oncology) studies, N0337 and N983252. IgG to HER2 intracellular domain (ICD), HER2-ECD, p53, IGFBP2, CEA, and tetanus toxoid were examined. Sera from 25 age-matched controls and 26 surgically resected HER2+ patients were also examined. Prior to therapy, some patients with metastatic disease had elevated antibodies to IGFBP2, p53, HER2-ICD, HER2-ECD, and CEA, but not to tetanus toxin, relative to controls and surgically resected patients. Treatment augmented antibody responses to HER2-ICD in 69% of metastatic patients, which was highly associated with improved progression-free survival (PFS; HR = 0.5, P = 0.0042) and overall survival (OS; HR = 0.7, P = 0.038). Augmented antibody responses to HER2-ICD also correlated (P = 0.03) with increased antibody responses to CEA, IGFBP2, and p53, indicating that treatment induces epitope spreading. Paradoxically, patients who already had high preexisting immunity to HER2-ICD did not respond to therapy with increased antibodies to HER2-ICD and demonstrated poorer PFS (HR = 1.6, P < 0.0001) and OS (HR = 1.4, P = 0.0006). Overall, the findings further demonstrate the importance of the adaptive immune system in the efficacy of trastuzumab-containing regimens. Cancer Res; 76(13); 3702–10. ©2016 AACR.

Circulating tumor cells (CTCs) are emerging as rare but clinically significant non-invasive cellular biomarkers for cancer patient prognosis, treatment selection, and treatment monitoring. Current CTC isolation approaches, such as immunoaffinity, filtration, or size-based techniques, are often limited by throughput, purity, large output volumes, or inability to obtain viable cells for downstream analysis. For all technologies, traditional immunofluorescent staining alone has been employed to distinguish and confirm the presence of isolated CTCs among contaminating blood cells, although cells isolated by size may express vastly different phenotypes. Consequently, CTC definitions have been non-trivial, researcher-dependent, and evolving. Here we describe a complete set of objective criteria, leveraging well-established cytomorphological features of malignancy, by which we identify large CTCs. We apply the criteria to CTCs enriched from stage IV lung and breast cancer patient blood samples using the High Throughput Vortex Chip (Vortex HT), an improved microfluidic technology for the label-free, size-based enrichment and concentration of rare cells. We achieve improved capture efficiency (up to 83%), high speed of processing (8 mL/min of 10x diluted blood, or 800 μL/min of whole blood), and high purity (avg. background of 28.8±23.6 white blood cells per mL of whole blood). We show markedly improved performance of CTC capture (84% positive test rate) in comparison to previous Vortex designs and the current FDA-approved gold standard CellSearch assay. The results demonstrate the ability to quickly collect viable and pure populations of abnormal large circulating cells unbiased by molecular characteristics, which helps uncover further heterogeneity in these cells.

ERBB receptors and their cognate ligands provide a rich and complex multilayered network of signaling control. Multiple layers of control act to safeguard against unwanted ERBB receptor activation, including the “closed” conformations of ligand-unbound EGFR, ERBB3, and ERBB4, auto-inhibited interactions among “open” conformation extracellular domains (ECDs), a vast repertoire of receptor-specific ligands (with, in some cases, a myriad of isoforms), the potential to form high-order complexes with associated proxy phosphorylation, and receptor-mediated endocytosis with associated recycling and degradation pathways. Despite these extensive safeguards, the deregulation of ERBB receptors is observed in multiple tumor types. In the case of ERBB2, the use of therapeutic antibodies aimed at distinct epitopes within the extracellular domain has resulted in marked improvements in clinical efficacy, and greater understanding of biology of ERBB2 receptor trafficking following receptor-mediated endocytosis has led to important insights in the development of an antibody-drug conjugate targeting this receptor. The multilayered nature of ERBB signaling offers a broad spectrum of future points for consideration of therapeutic interventions.

Background Trastuzumab emtansine (T-DM1) is an antibody–drug conjugate incorporating the human epidermal growth factor receptor 2 (HER2)–targeted antitumor properties of tras tuz u mab with the cytotoxic activity of the microtubule-inhibitory agent DM1. The antibody and the cytotoxic agent are conjugated by means of a stable linker. Methods We randomly assigned patients with HER2-positive advanced breast cancer, who had previously been treated with tras tuz u mab and a taxane, to T-DM1 or la pa ti nib plus cap e ci ta bine. The primary end points were progression-free survival (as assessed by independent review), overall survival, and safety. Secondary end points included progression-free survival (investigator-assessed), the objective response rate, and the time to symptom progression. Two interim analyses of overall survival were conducted. Results Among 991 randomly assigned patients, median progression-free survival as assessed by independent review was 9.6 months with T-DM1 versus 6.4 months with la pa ti nib plus cap e ci ta bine (hazard ratio for progression or death from any cause, 0.65; 95% confidence interval [CI], 0.55 to 0.77; P

Therapies targeting the ERBB2 receptor, including the kinase inhibitor lapatinib (Tykerb, GlaxoSmithKline), have improved clinical outcome for women with ERBB2-amplified breast cancer. However, acquired resistance to lapatinib remains a significant clinical problem, and the mechanisms governing resistance remain poorly understood. We sought to define molecular alterations that confer an acquired lapatinib resistance phenotype in ER-/ERBB2+ human breast cancer cells. ERBB2-amplified SKBR3 breast cancer cells were rendered resistant to lapatinib via culture in increasing concentrations of the drug, and molecular changes associated with a resistant phenotype were interrogated using a collaborative enzyme-enhanced immunoassay platform and immunoblotting techniques for detection of phosphorylated signaling cascade proteins. Interestingly, despite apparent inactivation of the PI3K/AKT signaling pathway, resistant cells exhibited constitutive activation of mammalian target of rapamycin complex 1 (mTORC1) and were highly sensitive to mTOR inhibition with rapamycin and the dual PI3K/mTOR inhibitor NVP-BEZ235. These data demonstrate a role for downstream activation of mTORC1 in the absence of molecular alterations leading to PI3K/AKT hyperactivation as a potential mechanism of lapatinib resistance in this model of ERBB2+ breast cancer and support the rationale of combination or sequential therapy using ERBB2 and mTOR-targeting molecules to prevent or target resistance to lapatinib. Moreover, our data suggest that assessment of mTOR substrate phosphorylation (i.e., S6) may serve as a more robust biomarker to predict sensitivity to mTOR inhibitors in the context of lapatinib resistance than PI3K mutations, loss of PTEN and p-AKT levels.

Cancer is caused by mutations in oncogenes and tumor suppressor genes, resulting in the deregulation of processes fundamental to the normal behavior of cells. The identification and characterization of oncogenes and tumor suppressors has led to new treatment strategies that have significantly improved cancer outcome. The advent of next generation sequencing has allowed the elucidation of the fine structure of cancer genomes, however, the identification of pathogenic changes is complicated by the inherent genomic instability of cancer cells. Therefore, functional approaches for the identification of novel genes involved in the initiation and development of tumors are critical. Here we report the first whole human genome in vivo RNA interference screen to identify functionally important tumor suppressor genes. Using our novel approach, we identify previously validated tumor suppressor genes including TP53 and MNT, as well as several novel candidate tumor suppressor genes including leukemia inhibitory factor receptor (LIFR). We show that LIFR is a key novel tumor suppressor, whose deregulation may drive the transformation of a significant proportion of human breast cancers. These results demonstrate the power of genome wide in vivo RNAi screens as a method for identifying novel genes regulating tumorigenesis.

Trastuzumab improves response rate, time to progression, and overall survival when combined with first-line chemotherapy in patients with human epidermal growth factor receptor 2-positive (HER2-positive) metastatic breast cancer (MBC). However, the benefits of continuing trastuzumab beyond disease progression have not been clearly established. The literature was reviewed to obtain data on trastuzumab use beyond disease progression. In general, data from retrospective and observational studies suggest that there may be clinical benefit when trastuzumab is used beyond disease progression. These results are supported by prospective non-randomized studies. Response rates and survival outcomes have generally been superior in patients who have continued trastuzumab after disease progression compared with those who have not. Moreover, recent data from two prospective randomized phase III trials have shown that adding trastuzumab to the treatment regimen in patients with MBC who have progressed on trastuzumab-based therapy significantly prolongs progression-free survival. Emerging evidence from randomized controlled trials supports the potential clinical utility of continuing trastuzumab-based therapy beyond progression and supports the National Comprehensive Cancer Network recommendation to consider this treatment approach. Future treatment of HER2-positive MBC may involve trastuzumab being used in successive regimens in combination with other targeted therapies.

Background: HER2 overexpression is associated with unfavorable prognosis and is reported in 18–25% of breast cancers (BC). HER2 testing is often performed using immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH). Because of the significant benefit of HER2−directed therapies, it is critical to accurately identify women whose tumors are HER2+. Reports have noted discordance between HER2+ test results from local vs. large reference labs in patients with HER2+ BC evaluated for trastuzumab-based clinical studies. There are little published data on central testing of BC found to be negative locally. Patients and Methods: VIRGO is an observational cohort of N=1,287 women with primarily HER2−negative metastatic BC. An optional tissue collection substudy was conducted, and 776 patient samples were received and centrally retested. Central testing was performed at 2 reference labs and tumors were deemed HER2+ if IHC 3+ and/or FISH positive (HER2:CEP17 ratio ≥2.0). Tumors with unknown/missing local HER2 status (n=68) were excluded from primary analyses. Number of patients potentially affected based on BC incidences from the American Cancer Society (ACS) 2011 estimates and the World Health Organization (WHO) 2008 report were calculated. Testing on the remainder of the HER2−negative cohort is in process. Results: Central retesting has been performed on tumor samples from n=373 patients to date: HER2−negative locally evaluable tumors (n=301), n=4 HER2−negative locally with no evaluable tumor, and HER2 unknown (n=68). A total of 301 unique patient samples were included in the primary analysis. Of these, 15 (4.98% [95% CI (2.7%, 7.9%)] were found to be HER2+ by central testing (Table). Based on sensitivity analyses assuming all 68 tumors with unknown HER2 status to be negative locally, 4.07%(15 /369) would be centrally HER2+. Of the 15 HER2+ tumors, 4 tumors tested positive centrally by both IHC and FISH; 6 IHC positive/FISH negative; and 5 FISH positive/IHC negative. 14/15 tumors were tested locally by only one testing methodology, and 11/15 were determined to be HER2+ centrally based on the testing methodology not performed locally. Investigators for all 15 patients have been notified of central HER2 testing results. Conclusion: Based on ACS estimates of 232,620 new cases of invasive BC diagnosed in the US in 2011 (assuming 80% testing HER2−negative); a discordance rate of 4–5% equates to 7,444 - 9,305 patients’ tumors diagnosed as HER2+ by central testing. Based on WHO global BC incidence estimates, 44,274 - 55,342 patients could be impacted worldwide as reported in this study. Inaccurate HER2 testing has significant clinical impact, both in denying appropriate treatment or leading to inappropriate use of HER2−targeted therapies. This study suggests testing by both IHC and FISH may be of benefit to accurately identify HER2 status, consistent with the Herceptin® USPI. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-07-02.

Purpose: AS1402 is a humanized immunoglobulin G1 antibody that targets the aberrantly glycosylated antigen MUC1, which is overexpressed in 90% of breast tumors and contributes to estrogen-mediated growth and survival of breast cancer cells in vitro by modulating estrogen receptor (ER) activity. Aromatase inhibitors have been reported to enhance antibody-dependent cell-mediated cytotoxicity elicited by antibodies in vitro. We compared the outcomes of patients with breast cancer treated with letrozole with or without AS1402. Experimental Design: The study population included 110 patients with locally advanced or metastatic hormone receptor–positive breast cancer randomized to receive 2.5 mg letrozole only once daily or with a weekly 9 mg/kg AS1402 infusion. The primary endpoint was overall response rate. Secondary endpoints included progression-free survival, time to progression, and safety. AS1402 exposure and influence of allotypes of FcγRIIIa, FcγRIIa, and MUC1 were evaluated. Results: The study was stopped early because of a trend toward worse response rates and a higher rate of early disease progression in the AS1402 + letrozole arm. Final analysis revealed no significant difference in efficacy between the study arms. Evaluated gene polymorphisms did not define patient subgroups with improved outcomes. Addition of AS1402 to letrozole was associated with manageable toxicity. Conclusions: Because adding AS1402 to letrozole did not improve outcomes compared with letrozole only, blocking ER may be a better strategy for harnessing MUC1 modulation of the ER to a clinical advantage. FcγRIIIa, FcγRIIa, and MUC1 allotype did not predict outcome for patients treated with letrozole with or without AS1402. Clin Cancer Res; 17(21); 6822–30. ©2011 AACR.