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ExteNET showed that neratinib, an irreversible pan-HER tyrosine ki- nase inhibitor, given for 1 year after trastuzumab-based therapy significantly improved inva- sive disease-free survival in women with early-stage HER2-positive breast cancer. We report the final analysis of overall survival in ExteNET.

Background: OP-1250 is a small molecule oral complete estrogen receptor antagonist (CERAN) that binds the ligand binding domain of the ER and completely blocks ER-driven transcriptional activity. CDK4/6 inhibitors in combination with endocrine therapy have improved progression free survival and overall survival for patients (pts) with metastatic breast cancer (MBC) in the first- and second-line settings. However, most patients will progress and newer combinations such as with OP-1250 may provide improved clinical outcome. OP-1250 potently inactivates both wild-type ER and mutant forms of ER. The latter confers ligand independent activity and is a mechanism of resistance to standard of care endocrine therapies. In preclinical studies, OP-1250 in combination with palbociclib demonstrated synergistic activity in models of wild-type ER and those containing ESR1 activating mutations, and in models of brain metastasis. A Phase 1/2 monotherapy study of OP-1250 is ongoing in MBC subjects who have received 1 or more prior endocrine therapies (NCT04505826). Monotherapy is well tolerated and the recommended phase 2 dose is 120 mg QD. The aim of this combination trial is to define the maximum tolerated dose (MTD), safety, tolerability, and pharmacokinetics (PK) of OP-1250 in combination with palbociclib. Methods: Eligibility criteria include pts with MBC or locally advanced breast cancer who have received no more than 1 prior line of endocrine therapy (prior CDK4/6 inhibitors and one line of chemotherapy are permitted) and measurable or non-measurable disease. Using a 3+3 design, cohorts are sequentially enrolled, and pts receive escalating doses of OP-1250 orally QD continuously in combination with 125 mg of palbociclib orally for 21 of 28 days. Pts are evaluable for dose limiting toxicities (DLTs) if >75% of both treatments were administered within the first 28-day treatment cycle. Blood is collected for PK on cycle 1 days 1, 2 and cycle 2 days 15, 16 for OP-1250 and cycle 1 day 15 for palbociclib. PK profiles, exposure parameters, and drug-drug interactions (DDIs) are assessed. Pts are monitored for adverse events (AE) and tumor assessments (RECIST 1.1) are conducted every two cycles. Results: As of July 7, 2022, 9 pts were evaluable for DLTs after 28 days of treatment in dose levels 30 mg, 60 mg, and 90 mg of OP-1250 in combination with palbociclib. No DLTs occurred at any of the dose levels. As of May 13, 2022, of the 7 pt safety data set, the most common Grade 1/2 treatment emergent adverse events (TEAE), which occurred in 2 patients, were nausea, gastroesophageal reflux, vomiting, and fatigue. Grade 3 neutropenia occurred in 4 pts and all were attributed to palbociclib by the investigator. No Grade 4 events were observed. OP-1250 was highly bioavailable and showed dose proportional exposure in combination with palbociclib. The single and multiple dose exposure of OP-1250 was consistent with that observed in the monotherapy study, indicating an absence of effect of palbociclib on OP-1250 PK. 90 mg steady-state evaluation is ongoing. Palbociclib concentrations at steady state did not demonstrate a meaningful difference from published exposure parameters for the three dose levels evaluated, indicating an absence of DDI. Conclusions: In the first three cohorts of OP-1250 and palbociclib, the combination was well tolerated and no DLTs occurred. There were no clinically significant DDIs observed between OP-1250 and palbociclib at the doses evaluated and exposure of each drug was consistent with observed monotherapy exposure levels. Dose escalation of OP-1250 continues to 120 mg, to be followed by dose expansion. Updated data will be presented. (NCT05266105) Citation Format: Arlene Chan, Daphne Day, Rina Hui, Nicole McCarthy, Rosalind Wilson, Demiana Faltaos, Morena Shaw, Caitlin Murphy. Preliminary data from a Phase 1b dose escalation study of OP-1250, an oral CERAN, in combination with palbociclib in patients with advanced and/or metastatic estrogen receptor (ER)-positive, HER2-negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-07-15.

Objectives This review discusses key oestrogens associated with the circulating pre- and post-menopausal milieu and how they may impact intratumoral oestrogen levels and breast cancer (BC) metastasis. It also identifies critical steps in BC metastasis to bone from the viewpoint of pigment epithelium-derived factor (PEDF) function, and discusses the role of several associated pro-metastatic biomarkers in BC bone metastasis. Key findings PEDF is regulated by oestrogen in a number of oestrogen-sensitive tissues. Changes in circulating oestrogen levels associated with menopause may enhance the growth of BC bone metastases, leading to the establishment of a pre-metastatic niche. The establishment of such a pre-metastatic niche is driven by several key mediators, with pro-osteoclastic and pro-metastatic function which are upregulated by BC cells. These mediators appear to be regulated by oestrogen, as well as differentially affected by menopausal status. PEDF interacts with several pro-metastatic, pro-osteoclastic biomarkers, including C-X-C motif chemokine receptor 4 (CXCR4) and nuclear factor kappa B (NFκB) in BC bone metastasis. Conclusion Mediators such as CXCR4 and MT1-MMP underpin the ability of PEDF to function as an antimetastatic in other cancers such as osteosarcoma, highlighting the possibility that this serpin could be used as a therapeutic against BC metastasis in future.

Supplementary Figure S1-S6 and Supplementary Tables S1-S8

Purpose:The primary objective was to evaluate intracranial objective response rate (iORR) in patients receiving abemaciclib with brain or leptomeningeal metastases (LM) secondary to hormone receptor–positive (HR+) metastatic breast cancer (MBC). Secondary objectives evaluated extracranial response, abemaciclib pharmacokinetics, brain metastases tissue exposure, and safety.Patients and Methods:This nonrandomized, phase II study (NCT02308020) enrolled patients in tumor subtype–specific cohorts A–D: A (HR+, HER2− MBC), B (HR+, HER2+ MBC), C (HR+ MBC LM), and D (brain metastases surgical resection). Abemaciclib 200 mg was administered twice daily as monotherapy or with endocrine therapy, or 150 mg twice daily with trastuzumab. Cohorts A and B used a Simon two-stage design.Results:In cohort A (n = 58), 3 patients were confirmed responders resulting in an iORR of 5.2% [95% confidence interval (CI), 0.0–10.9], and the intracranial clinical benefit rate (iCBR) was 24% (95% CI, 13.1–35.2). Median overall survival (OS) was 12.5 months (95% CI, 9.3–16.4). A volumetric decrease in target intracranial lesions was experienced by 38% of patients. In cohort B (n = 27), there were no confirmed intracranial responses. An iCBR of 11% (95% CI, 0.0–23.0) was observed. Median OS was 10.1 months (95% CI, 4.2–14.3). A volumetric decrease in target intracranial lesions was experienced by 22% of patients. In cohort C (n = 10), one confirmed complete parenchymal response was observed. In cohort D (n = 9), unbound brain metastases concentrations of total active abemaciclib analytes were 96- [cyclin-dependent kinase 4 (CDK4)] and 19-fold (CDK6) above in vitro IC50. Safety was consistent with prior studies.Conclusions:This study did not meet its primary endpoint. Abemaciclib was associated with an iCBR of 24% in patients with heavily pretreated HR+, HER2− MBC. Abemaciclib achieved therapeutic concentrations in brain metastases tissue, far exceeding those necessary for CDK4 and CDK6 inhibition. Further studies are warranted, including assessing novel abemaciclib-based combinations.

Supplementary Figure 4. Multivariable Cox proportional hazards regression analyses for disease free survival (DFS; left panel) and corresponding forest plots (Right panel).

Change in parenchymal intracranial (Panel A1) and extracranial (Panel B) tumor size and best overall response, and duration of exposure to abemaciclib (Panel C) in cohort C (HR+, HER2- and HR+, HER2+ MBC with LM). 1Panel A is only for patients with HR+, HER2- MBC with LM, as the patients with HR+, HER2+ MBC had no intracranial parenchymal lesions or post-baseline scans. Note: Patients who did not have an intracranial or extracranial lesion or a post-baseline scan are not shown on waterfall plots. oIndicates patient received prior whole brain radiotherapy. +Indicates patient received prior stereotactic radiosurgery. #Indicates patient received concomitant endocrine therapy. Abbreviations: CR, complete response; HER2+/â^', human epidermal growth factor receptor-2 positive/negative; HR+, hormone receptor positive; MBC, metastatic breast cancer; LM, leptomeningeal metastases; NE, not estimable; PD, progressive disease; PR, partial response; SD, stable disease.

Supplementary Figure 2. Receiver operating characteristic (ROC) analysis of pathological complete response (pCR), revised pathological TNM stage (yp-TNM stage), Clinical-Pathologic Scoring System (CPS) score and CPS-Oestrogen receptor-histological grade (CPS-EG) were performed for predicting breast cancer specific survival in the training (A), internal validation (B), external validation (C) and combined three cohorts (D).

supplemental figure legend.

Supplementary Figure 5. Kaplan Meier curves and lifetime table showing disease free survival (DFS) in the training (A), internal validation (B), and external validation (C) cohorts stratified according to Nottingham clinicopathological response index prognostic groups (NPRI-PGs).

Supplementary Figure 1. Kaplan Meier curves showing disease free survival (DFS) in the training (upper panels), internal validation (middle panels) and external validation (lower panels) cohorts stratified according to the number of lymph node (LN) metastases (i), presence of lympho-vascular invasion (LVI; ii), absence of fibrosis (iii) the percentage reduction in primary tumour size (iv).

Supplementary Tables 1 to 5. Table (S1): Clinico-pathological characteristics of all three individual cohorts and the sum of all three together. Table (S2): Summery of pathological features that have been reviewed Table (S3): Univariate and multivariate backward step-wise analysis for factors associated with disease free survival (DFS) in the training cohort. Table (S4): Summery of the code system that has been used for calculation of Nottingham clinico-pathological response index (NPRI) Table (S5): Univariate analysis for clinicopathological features associated with disease free survival (DFS) and breast cancer specific survival (BCSS) in the training, internal and external validation cohorts.

Purpose: There is a need to identify more sensitive clinicopathologic criteria to assess the response to neoadjuvant chemotherapy (Neo-ACT) and guide subsequent adjuvant therapy.Experimental Design: We performed a clinicopathologic assessment of 426 patients who had completed Neo-ACT for locally advanced breast cancer (LABC) with a median follow-up of 70 months. Patients were divided into a training set treated with anthracycline combination chemotherapy (n = 172); an internal validation set treated with anthracycline and taxane (n = 129); and an external validation set treated with anthracycline with or without taxane (n = 125).Results: A multivariate Cox regression model demonstrated the absence of fibrosis, presence of lymphovascular invasion, increasing number of lymph node metastases, and administration of hormone therapy were significantly associated with short breast cancer–specific survival (BCSS) and disease-free survival (DFS); Ps < 0.01, while reduction of tumor size was associated with DFS (P = 0.022). Nottingham Clinico-Pathological Response Indexes (NPRI) were calculated, and four prognostic groups (NPRI-PG) were identified. Patients in prognostic group 2 (NPRI-PG2) for BCSS (66 of 172; 38.4%) have the same prognosis as those who achieved pathologic complete response (pCR; NPRI-PG1; 15%). Receiver-operating characteristic (ROC) curves indicated that the NPRI outperformed the currently used prognostic factors and adding the NPRI improved their performance as a predictor for both BCSS (area under the curve [AUC], 0.88) and DFS (AUC, 0.87).Conclusions: The NPRI predicts BCSS and DFS, with a higher sensitivity than pCR. The NPRI can also improve the sensitivity and specificity of clinicopathologic response as a study endpoint, for assessing response to Neo-ACT, and can serve as a valuable tool for the discovery of future predictive molecular markers. Clin Cancer Res; 21(5); 1052–62. ©2014 AACR.

Prior and concomitant therapies in patients from cohort A (HR+, HER2-) with intracranial clinical benefit.

Supplementary Figure 3. Multivariable Cox proportional hazards regression analyses for disease free survival (DFS; left panel) and corresponding forest plots (Right panel).

Purpose:This phase II study determined the efficacy of lacnotuzumab added to gemcitabine plus carboplatin (gem-carbo) in patients with advanced triple-negative breast cancer (TNBC).Patients and Methods:Female patients with advanced TNBC, with high levels of tumor-associated macrophages not amenable to curative treatment by surgery or radiotherapy were enrolled. Lacnotuzumab was dosed at 10 mg/kg every 3 weeks, ± a dose on cycle 1, day 8. Gemcitabine (1,000 mg/m2) and carboplatin (dose in mg calculated by area under the curve [mg/mL/min] × (glomerular filtration rate [mL/min] + 25 [mL/min]) were dosed every 3 weeks. Treatment continued until unacceptable toxicity, disease progression, or discontinuation by physician/patient.Results:Patients received lacnotuzumab + gem-carbo (n = 34) or gem-carbo (n = 15). Enrollment was halted due to recruitment challenges owing to rapid evolution of the therapeutic landscape; formal hypothesis testing of the primary endpoint was therefore not performed. Median progression-free survival was 5.6 months [90% confidence interval (CI), 4.47–8.64] in the lacnotuzumab + gem-carbo arm and 5.5 months (90% CI, 3.45–7.46) in the gem-carbo arm. Hematologic adverse events were common in both treatment arms; however, patients treated with lacnotuzumab experienced more frequent aspartate aminotransferase, alanine aminotransferase, and creatine kinase elevations. Pharmacokinetic results showed that free lacnotuzumab at 10 mg/kg exhibited a typical IgG pharmacokinetic profile and target engagement of circulating colony-stimulating factor 1 ligand.Conclusions:Despite successful target engagement and anticipated pharmacokinetic profile, lacnotuzumab + gem-carbo showed comparable antitumor activity to gem-carbo alone, with slightly poorer tolerability. However, the data presented in this article would be informative for future studies testing agents targeting the CSF1–CSF1 receptor pathway in TNBC.

Supplementary Figure 6. Receiver operating characteristic (ROC) analysis of Nottingham clinico-pathological response index (NPRI) score and other clinico-pathological covariates were performed for predicting disease free survival in the training (A), internal validation (B), external validation (C) and combined three cohorts (D).

Background: As the development and use of oral anticancer agents increases, it is critical to understand patient adherence to both standard and investigational agents. The open label, phase 3 multicenter PALLAS trial investigates whether adding 2 years of the CDK4/6 inhibitor palbociclib (P) to adjuvant endocrine therapy (ET) improves invasive disease-free survival (iDFS) over adjuvant ET alone in patients (pts) with HR- positive, HR2-negative, stage II-III breast cancer. Pts were randomly assigned to either Palbociclib (125 mg/day, 3 weeks on, 1 week off, in a 28-day cycle) plus ongoing provider/patient-choice adjuvant ET (P+ET) versus ET alone. We examined patient-reported adherence to ET +/- P during the first two years of study treatment. Methods: Adherence outcomes were measured in English-speaking pts in the U.S., UK, Ireland and Australia, Spanish-speaking pts in Spain and Mexico, and German-speaking pts in Germany and Austria. Adherence measures included drug diaries completed at each cycle, pill counts (for P only) collected at each study visit, and the Morisky Medication Adherence Scale-4 item and the McHorney Adherence Estimator questionnaires completed at cycles 2, 3, 6, 12, 18, and 24 (22 months). Mean adherence for each cycle was defined as the average proportion of prescribed pills taken (via drug diary) across all patients who initiated that cycle. Persistence was defined as the duration of drug initiation to treatment cessation (via drug diary). Generalized estimating equations were used to model the “most adherent” pts on the Morisky (score = 5 vs score 0) to compare the average difference between arms over time for ET, adjusting for baseline demographic and clinical variables. Results: 81% (N=4688) of PALLAS pts were included in this analysis. Median persistence to ET was 23.6 months in P + ET (n=2169), 23.7 months in ET alone (2136) and 20.4 months for P (n=2194). The number of pts who initiated each cycle for ET declined over time and was similar between arms; the decline was more marked for P (Table 1). Mean adherence range as measured by drug diary was 98.2-99.3% for ET in P+ET and 98.0 - 99.4% in ET alone; and for P, ranged from 93.4 - 98.8%. The adherence and persistence results were nearly identical whether measured by drug diary or pill count for P. The observed percent “most adherent” for P measured by the Morisky scale ranged from 71.9% - 79.6% and the percent “low risk” for adherence problems measured by the McHorney scale, 64.0% - 73.4%. The percent of pts “most adherent” and “low risk” for adherence problems to ET was higher, on average over time, in the P+ET group compared to ET alone (75% vs 68%, p Table 1.Adherence and persistence in PALLAS over the 24 month treatment periodPalbocicilb + ETETPalbociclibETETTreatment cycleMean Adherence (SD)N*Mean Adherence (SD)NMean Adherence (SD)N193.4 (13.8)229098.7 (6.1)230999.0 (5.2)2343294.7 (13.3)218198.8 (6.4)220398.4 (7.1)2206397.4 (10.1)211298.7 (7.3)214298.8 (6.3)2168497.6 (10.2)203598.6 (7.8)211099.0 (5.7)2154597.6 (11.1)197598.3 (7.9)209398.1 (8.3)2148698.1 (8.7)189998.7 (6.6)203798.5 (8.2)2116798.1 (9.3)185599.0 (6.3)201298.6 (7.3)2102898.0 (9.1)181098.2 (8.2)199798.1 (8.2)2092998.4 (7.4)173399.0 (6.4)196298.8 (6.8)20511098.3 (8.6)171499.2 (4.9)194699.0 (5.5)20381198.3 (8.0)169198.5 (7.3)193798.2 (8.2)20311298.7 (6.2)161299.1 (5.3)191098.7 (7.5)19861398.5 (7.7)159698.9 (6.4)189398.8 (7.1)19691497.9 (9.3)157698.4 (7.3)188298.0 (9.1)19611598.5 (6.9)151499.2 (4.6)185499.0 (6.0)19281698.2 (8.7)148699.1 (4.6)183599.1 (5.7)19131798.1 (9.8)147998.3 (7.8)182698.5 (6.4)19031898.7 (6.8)141699.3 (4.1)176899.2 (5.3)18601998.7 (7.3)140899.3 (3.8)175699.4 (3.1)18482098.4 (8.9)139798.9 (5.3)174298.7 (5.8)18382198.5 (7.5)130199.0 (6.1)167698.8 (7.1)17842297.8 (9.7)124698.8 (6.2)164799.2 (5.7)17692398.1 (8.8)118098.2 (8.5)161998.4 (8.0)17552498.8 (7.2)108699.0 (6.3)146898.9 (7.1)16192598.8 (6.7)99699.2 (5.2)143298.8 (7.1)15892697.9 (11.2)84599.1 (5.7)140998.6 (8.8)1578ET=Endocrine therapy * Number of pts who initiated the treatment cycle. Citation Format: Eileen Shinn, David Zahrieh, Angela DeMichele, Nick Zdenkowski, Julie Lemieux, Jun Mao, Vesna Bjelic-Radisic, Michelle Naughton, Georg Pfeiler, Karen Gelmon, Ingrid Mayer, Daniel Egle, Gabriele Zoppoli, Tiffany Traina, Miguel Martin Jiménez, Silvia Antolin Novoa, Tufia Haddad, Arlene Chan, Alistair Edward Ring, Antonio Wolff, Jose JuanPonce Lorenzo, Dhanusha Sabanathan, Hal Burstein, Zbigniew Ireneusz Nowecki, Gunda Pristauz-Telsnigg, Adam Brufsky, Meritxell Bellet-Ezquerra, Theodoros Foukakis, Yelena Novik, Gabor Rubovszky, Karoline Muehlbacher, Otto Metzger, Theodora Goulioti, Ernest Law, Ann Partridge, Lisa Carey, Alex Zoroufy, Dominik Hlauschek, Christian Fesl, Erica Mayer, Michael Gnant. Adherence with adjuvant endocrine therapy with or without Palbociclib in the PALLAS trial [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 P4-12-01.

Background: Neratinib (NERLYNX®), an irreversible pan-HER tyrosine kinase inhibitor, is approved for the extended adjuvant treatment of early-stage HER2+ breast cancer following adjuvant trastuzumab-based therapy and in combination with capecitabine for HER2+ metastatic breast cancer. Diarrhea is the most frequently reported on-target side effect associated with neratinib; in the ExteNET adjuvant trial, where no mandatory anti-diarrheal prophylaxis was used, 39.8% of patients reported grade 3 diarrhea and 16.8% of patients discontinued neratinib due to diarrhea. The CONTROL trial (Clinicaltrials.gov: NCT02400476) was designed to investigate pre-emptive antidiarrheal prophylaxis (loperamide alone or in combination with budesonide or colestipol) or neratinib dose escalation (DE) for the prevention of neratinib-associated diarrhea. Data for the loperamide, budesonide and colestipol cohorts have been reported previously [Barcenas et al. Ann Oncol 2020]. The final findings for the two DE regimen cohorts are reported here. Methods: CONTROL is an international, multi-cohort, open-label, phase 2 study. Patients ≥18 years of age with stage I-IIIc HER2+ breast cancer received oral neratinib (240 mg/day for 1 year) after trastuzumab-based adjuvant therapy. Patients were enrolled sequentially into separate cohorts investigating: 1) mandatory loperamide prophylaxis; 2) budesonide + loperamide; 3) colestipol + loperamide; 4) colestipol + loperamide PRN; 5) neratinib DE + loperamide PRN (two cohorts). DE1 schedule: neratinib 120 mg/day for week 1, 160 mg/day for week 2, then 240 mg/day from week 3 onwards to complete 12 months of treatment. DE2 schedule: neratinib 160 mg/day for weeks 1&2, 200 mg/day for weeks 3&4, then 240 mg/day from week 5 onwards up to 12 months. Both DE cohorts included loperamide PRN. Adverse events were graded according to NCI-CTCAE v4.0. Primary endpoint: incidence of grade ≥3 diarrhea. Results: A total of 563 patients were enrolled in CONTROL. All preventive strategies reduced the incidence of grade 3 diarrhea compared with that seen in ExteNET (historical control: 39.8%). Median cumulative duration of grade 3 diarrhea ranged from 2-3.5 days across the CONTROL study cohorts for the entire 12-month treatment period (compared with 5.0 days for ExteNET). The proportion of patients discontinuing neratinib because of diarrhea was decreased in all cohorts compared with ExteNET (16.8%), except for loperamide alone. Adoption of neratinib DE, particularly the 2-week DE schedule (DE1), most markedly reduced the incidence, severity, and duration of neratinib-associated diarrhea in CONTROL compared with ExteNET (see Table). Conclusions: Neratinib DE + loperamide PRN during the first 2 weeks of treatment (DE1 cohort) was associated with the lowest rates of grade 3 diarrhea (13.3%) and diarrhea-related discontinuations (3.3%) compared with all other anti-diarrheal strategies investigated in CONTROL. These final findings from the study show improved tolerability of neratinib with all diarrhea prophylaxis strategies and suggest that neratinib DE1 with loperamide PRN allows patients to stay on treatment longer and receive the full benefit of neratinib therapy. Table. Patient disposition and diarrhea characteristics: ExteNET vs CONTROL DE cohortsExteNET(n=1408)CONTROL DE1 (n=60)CONTROL DE2 (n=62)Patients completing 1 year of neratinib treatment, %617874Median duration of treatment, months (range)11.6 (2.5–11.9)12.0 (0.2–12.4)11.9 (0.3–14.5)Diarrhea, %Grade 339.813.327.4Grade 4 Citation Format: Arlene Chan, Manuel Ruiz-Borrego, Gavin Marx, Adam Brufsky, Jo Chien, Michael Thirlwell, Maureen Trudeau, Ron Bose, José A García-Sáenz, Daniel Egle, Barbara Pistilli, Johanna Wassermann, Kerry A Cheong, Christian F Singer, Daniel Hunt, Navid Foruzan, Leanne McCulloch, Carlos H Barcenas. Final findings from the CONTROL trial of diarrheal prophylaxis or neratinib dose escalation on neratinib-associated diarrhea and tolerability in patients with HER2+ early-stage breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-18-02.

PURPOSE Palbociclib is a cyclin-dependent kinase 4 and 6 inhibitor approved for advanced breast cancer. In the adjuvant setting, the potential value of adding palbociclib to endocrine therapy for hormone receptor–positive breast cancer has not been confirmed. PATIENTS AND METHODS In the prospective, randomized, phase III PALLAS trial, patients with hormone receptor–positive, human epidermal growth factor receptor 2–negative early breast cancer were randomly assigned to receive 2 years of palbociclib (125 mg orally once daily, days 1-21 of a 28-day cycle) with adjuvant endocrine therapy or adjuvant endocrine therapy alone (for at least 5 years). The primary end point of the study was invasive disease-free survival (iDFS); secondary end points were invasive breast cancer–free survival, distant recurrence-free survival, locoregional cancer-free survival, and overall survival. RESULTS Among 5,796 patients enrolled at 406 centers in 21 countries worldwide over 3 years, 5,761 were included in the intention-to-treat population. At the final protocol-defined analysis, at a median follow-up of 31 months, iDFS events occurred in 253 of 2,884 (8.8%) patients who received palbociclib plus endocrine therapy and in 263 of 2,877 (9.1%) patients who received endocrine therapy alone, with similar results between the two treatment groups (iDFS at 4 years: 84.2% v 84.5%; hazard ratio, 0.96; CI, 0.81 to 1.14; P = .65). No significant differences were observed for secondary time-to-event end points, and subgroup analyses did not show any differences by subgroup. There were no new safety signals for palbociclib in this trial. CONCLUSION At this final analysis of the PALLAS trial, the addition of adjuvant palbociclib to standard endocrine therapy did not improve outcomes over endocrine therapy alone in patients with early hormone receptor–positive breast cancer.

Background: Amplification of the human epidermal growth factor receptor 2 (HER2) gene with consequent HER2 protein overexpression occurs in approximately 20% of breast cancers (BC) and is a major driver of tumor development and progression. The HER2-targeted ADC trastuzumab emtansine (T-DM1) has been approved for the treatment of HER2-positive metastatic BC (mBC) after prior trastuzumab and taxane therapy. However, disease progression occurs in all patients requiring additional therapeutic options. The use of second-generation anti-HER2 ADCs using alternative molecules is being investigated to overcome drug resistance. ARX788 is a next-generation ADC using a technology platform whereby a HER2-specific monoclonal antibody is conjugated with Amberstatin269, a potent cytotoxic tubulin inhibitor. Site-specificity, high homogeneity, and stable covalent conjugation of ARX788 lead to its slow release and prolongation of the peak serum pAF-AS269 concentration, which may contribute to the lower systemic toxicity and increased targeted delivery of payload to tumor cells at a lower effective dose compared to other HER2 ADCs. Here, early evidence of activity of ARX788 in patients previously treated with T-DM1 is shown. Methods: ACE-Breast-03 (NCT04829604) is an ongoing global, phase 2, single-arm study evaluating ARX788 in patients with HER2+ mBC whose disease has progressed following T-DM1, T-DXd, and/or tucatinib-containing regimens. The ARX788 is administered with an initial dose of 1.5 mg/kg Q4W and subsequent doses of 1.3 mg/kg Q4W. Eligibility criteria included central laboratory confirmed HER2+ mBC per ASCO/CAP guidelines, measurable disease, and adequate organ function. Stable treated brain metastases are allowed. Patients with interstitial lung disease (ILD) or pneumonitis in prior 12 months; active ocular infections or any chronic corneal disorder; are excluded. The primary endpoint is overall response rate (ORR). Results: At the data cutoff of 11-Jul-2022, 7 patients were enrolled in ACE-Breast-03 (v1.0) who previously experienced disease progression on T-DM1 and had response-evaluable disease. Pts had a median age of 59 years and had received a median of 5 lines of prior anti-HER2 cancer therapy (range: 2-8). None of the pts in this subset had received T-DXd or tucatinib. 5 pts were previously treated with HER2-targeted TKIs (neratinib and lapatinib), as well as an investigational HER2 ADC and responded to ARX788 (3 PR; 2 SD). Two patients had hormone receptor (HR)-positive disease and 5 had HR-negative mBC. Treatment with ARX788 remains ongoing with the median time of ARX788 therapy of 4.5 months. The confirmed ORR was 57.1% (4/7 pts) and an unconfirmed ORR of 71.4% (5/7 pts) as one pt experienced an unconfirmed response with PR after 2 cycles. The disease control rate (DCR) was 100% (7/7 pts). No drug-related grade ≥3 AEs were reported; 57.1% (4/7 pts) reported ocular AEs including grade 1 events in 3 pts (i.e., dry eye, blurred vision) and a grade 2 event in one pt (lagophthalmos). No pneumonitis or ILD was observed. ARX788 was well-tolerated, and AEs were manageable. Conclusion: In this small cohort of patients previously treated with T-DM1, ARX788 had a manageable AE profile and demonstrated promising clinical activity (confirmed ORR 57%; DCR 100%). Figure 1: ACE-Breast-03 Spider Plot for patients with mBC who were previously treated with T-DM1 Figure 1: ACE-Breast-03 Spider Plot for patients with mBC who were previously treated with T-DM1 ARX788 demonstrated promising clinical activity in patients previously treated with T-DM1. Citation Format: Sara Hurvitz, Kevin Kalinsky, Vinod Ganju, Kashif Ali, Laila Agrawal, William Gradishar, George Sledge, Anu Thummala, Arlene Chan, Sophia Frentzas, Joo Hyuk Sohn, Kyong-Hwa Park, Keon Uk Park, Catherine Shannon, Joshua Drago, Sara Tolaney, Hope Rugo, Michael F. Press, Alex Alika, Dong Xu, Janice Lu, Debu Tripathy. ACE-Breast-03: Efficacy and safety of ARX788 in patients with HER2+ metastatic breast cancer previously treated with T-DM1 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD18-09.

Introduction D-CARE, an international, phase 3, randomized, double-blind, placebo-controlled study in women with early-stage breast cancer at high risk of disease recurrence, failed to meet its primary endpoint—improvement in bone metastasis-free survival (BMFS) with adjuvant denosumab vs placebo injections. As a result of the limitations of assessing BMFS, which includes relapse in bone with and without extraskeletal recurrences and deaths from any cause, the prespecified exploratory bone endpoints’ analysis may provide a more clinically meaningful effect of denosumab in this disease setting. Methods The study enrolled women (aged ≥ 18 years) with histologically confirmed stage II/III breast cancer. Patients treated with adjuvant/neoadjuvant chemotherapy meeting inclusion criteria were randomly assigned 1:1 to receive either denosumab (120 mg) or placebo subcutaneously every 3–4 weeks for about 6 months and then every 3 months for a total treatment duration of 5 years. Five prespecified exploratory bone endpoints and post hoc subgroup analysis based on age (

Pigment epithelium-derived factor (PEDF) has a critical role in bone development and anti-tumour function in breast cancer (BC). As the expression and role of PEDF in BC bone metastases is unknown, we aimed to characterise PEDF in primary and metastatic BC. Subcellular PEDF localisation was semi-quantitatively analysed via immunohistochemistry in patient-matched, archived formalin-fixed paraffin-embedded primary BC and liver, lung, and decalcified bone metastases specimens. PEDF localisation was evaluated in 23 metastatic BC patients diagnosed with ER+, human epidermal growth factor receptor-2 (HER2) negative BC or TNBC. Cytoplasmic (p = 0.019) and membrane (p = 0.048) PEDF was lower in bone metastases compared to primary ER+/HER2- BC. In contrast, nuclear PEDF scores were higher in metastases compared to primary TNBC (p = 0.027), and increased membrane PEDF in metastatic tissue had improved disease-free interval (p = 0.016). Nuclear PEDF was decreased in bone metastases compared to primary ER+//HER2- BC in post-menopausal patients (p = 0.029). These novel findings indicate PEDF plays a role in clinical BC metastasis. Significantly lower PEDF levels in the post-menopausal compared to pre-menopausal setting suggests future PEDF research may have greater clinical importance in the post-menopausal ER+/HER2- BC population.

Purpose Review of utilization and efficacy of eribulin in Australian metastatic breast cancer (MBC) patients. Methods Retrospective review of consecutive MBC patients treated with eribulin in tertiary Australian BC centers. Key inclusion criteria included eribulin administration in nonclinical trial setting from October 2014 onwards, known duration of MBC systemic treatments administered and known follow-up date after eribulin. Cox regression model was used to assess survival. Results Study population comprised 266 patients from eight centers treated between October 2014 and May 2018. Median age at time of MBC diagnosis was 54 years with 18% of patients having de novo MBC. Seventy-six percent had hormone receptor positive (HRp) disease, 19% triple negative (TN) and 5% HER2-positive. CNS involvement was present in 36% of patients. Eribulin was most frequently given as third-line chemotherapy (36%), with no prior anthracycline exposure in 14% of total population. Eribulin was given more frequently as ≤third-line chemotherapy than > third-line in patients with TN disease, ≥ two metastatic sites or CNS disease. Median overall survival (OS) from eribulin administration was 9.2 (95% CI [8.0, 10.3]) months. Conclusion Similar efficacy was demonstrated for eribulin when given in the first-line to beyond the fifth line of chemotherapy in all subtypes of MBC.

Background: Neratinib (NERLYNX®), an irreversible pan-HER tyrosine kinase inhibitor, is used for the extended adjuvant treatment of patients with early-stage HER2-positive (HER2+) breast cancer following adjuvant trastuzumab-based therapy and for patients with HER2+ metastatic breast cancer in the 3rd-line setting. Diarrhea, particularly in the first 1-2 months, is the main tolerability concern with neratinib and is common in the absence of proactive management. In the ExteNET trial, where no mandatory prophylaxis was used, the rate of grade 3 diarrhea was 40%, 34% of patients experienced at least 1 dose hold, and 17% of patients discontinued due to diarrhea. The CONTROL trial previously showed that pre-emptive antidiarrheal prophylaxis (loperamide alone or in combination with budesonide or colestipol) or dose escalation (DE) reduced the rate, severity, and duration of neratinib-associated grade ≥3 diarrhea compared with ExteNET. Currently, antidiarrheal prophylaxis is initiated with the first dose of neratinib and used during the first 2 cycles of treatment (US PI). Updated findings from two DE cohorts in CONTROL are reported. Methods: CONTROL is an international, multi-cohort, open-label, phase 2 study. Patients ≥18 years with stage I-IIIc HER2+ breast cancer were treated with neratinib (240 mg/day for 1 year) after trastuzumab-based adjuvant therapy. Patients were enrolled sequentially into separate cohorts including 2 dose-escalation cohorts: DE1 (neratinib 120 mg/day on days 1-7, 160 mg/day on days 8-14, then 240 mg/day to day 365) + loperamide as needed (PRN); and DE2 (neratinib 160 mg/day on days 1-14, 200 mg/day on days 15-28, then 240 mg/day to day 365) + loperamide PRN. Adverse events were graded per NCI-CTCAE v4.0. Primary endpoint: incidence of grade ≥3 diarrhea. Data cut-off: May 1, 2020. Results: Complete data for DE1 (60 patients) and interim data for the ongoing DE2 (60 patients) are presented. All patients in DE1 were off study and 40 (66.7%) of patients remained on treatment in the ongoing DE2. The median treatment duration for DE1 was 12.0 months (IQR 11.1-12.0) and for DE2 was 3.7 months (IQR 1.6-9.1). Overall, 48% and 57% of DE1 and DE2 patients, respectively, had prior pertuzumab; 0% and 3%, respectively, had prior T-DM1. The majority of patients in both DE1 and DE2 dose-escalated to 240 mg on planned schedule. The incidence of grade ≥3 diarrhea was 13.3% in DE1 and 20.0% in DE2. The median cumulative duration of grade ≥3 diarrhea over the entire 12-month treatment period was 3 days (range 1-6 days) for DE1 and 2 days (range 1-7 days) for DE2. In both DE1 and DE2, 7 patients (11.7%) had at least one dose hold while on study (none during escalation phase in DE1 and 4 during escalation phase in DE2). In both DE1 and DE2, 2 (3.3%) patients discontinued neratinib because of diarrhea (1 during escalation phase in each cohort). Updated data for the DE2 cohort will be presented. Conclusions: Adoption of neratinib DE reduced the incidence, severity, and duration of neratinib-associated diarrhea in CONTROL compared with ExteNET. DE1 was associated with low rates of dose holds and diarrhea-related discontinuations compared with all previously mandated prophylaxis strategies investigated in CONTROL and with ExteNET. Together these results show improved tolerability of neratinib with DE and suggest that DE combined with loperamide PRN may allow patients to stay on neratinib for the recommended period of time. Neratinib dose escalation scheme 1 (n=60)Neratinib dose escalation scheme 2 (n=60)On neratinib treatment, %066.7Median duration of treatment, months12.03.7Diarrhea, %Grade 140.041.7Grade 245.033.3Grade 313.320.0Grade 400Discontinuation rate due to diarrhea, %3.33.3At least one dose hold due to diarrhea, %11.711.7 Citation Format: Manuel Ruiz-Borrego, Arlene Chan, Gavin Marx, Adam Brufsky, A Jo Chien, Michael Thirlwell, Maureen Trudeau, Ron Bose, José A García-Sáenz, Daniel Egle, Daniel Hunt, Utpal Khambholja, Leanne McCulloch, Naisargee Shah, Debu Tripathy, Carlos H Barcenas, the CONTROL Investigators. Bringing diarrhea under CONTROL: Dose escalation reduces neratinib-associated diarrhea and improves tolerability in HER2-positive early-stage 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 PS13-20.

Background: Metastatic TNBC (mTNBC) has a poor prognosis. Preclinical data suggests benefit for combination therapy of immune checkpoint inhibitor and anti-angiogenesis. Olinvacimab (O) is a fully humanised monoclonal antibody (MAB) which binds to Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) and antiangiogenic and antitumor effects have been demonstrated. Pembrolizumab (P) is an anti-PD1 MAB. This study aimed to identify the safety and tolerability of O and P to establish a phase 2 recommended dose of O. Methods: From December 2018 to September 2020, we conducted a two-site, single arm, open-label study of O and P in pts with mTNBC. Eligible patients (pts) were >18 years, had ER, PR & HER2-negative MBC with at least one measurable lesion and adequate organ function. Pts with history of serious thromboembolism, gastrointestinal haemorrhage and prior anti-VEGF therapy were excluded. A modified Toxicity Probability Interval design was used. Pts received O 12 mg/kg q7d (dose level 1) or 16mg/kg day q7d (dose level 2) in combination with P 200mg flat dose day 1 q21d. Treatment continued until dose limiting toxicity (DLT), disease progression (PD) or treatment intolerance. Results: 11 pts, median age 62 (range 39-67) were recruited and received at least one dose of treatment. 8 (73%) had ECOG PS 1 and 3 (27%) had ECOG PS 2. 5 pts had previous chemotherapy for mTNBC (with 3 pts also having received immunotherapy), 6 pts were treated in the first-line metastatic setting (with all pts having received anthracycline and taxane in the adjuvant setting). 5 pts received O at 12mg/kg with P, completing a median of 6 cycles (range 1-18). As no DLTs were seen, 6 pts were treated with O at 16mg/kg with median of 8 cycles (range 2-21), with no DLTs being observed. Treatment was ceased due to PD in 6 pts, 3 pts are receiving treatment at data cut-off. Haemangiomas were seen in 8 pts accounting for 47 events of CTCAE grade 1 and 21 events of grade 2. Treatment emergent adverse events (TEAEs) of ≥grade 3 was seen in 6 pts (27 events), with 8 events being related to treatment. 4 pts (36%) had partial response (PR) as best overall response 5 pts (45%) had clinical benefit (PR+SD≥24weeks). Conclusions: Combination therapy of O and P was well tolerated with evidence of efficacy in mTNBC pts who had all previously received anthracycline and taxanes, with 3 pts having previously received immunotherapy. These results support the combination entering into a phase 2 study. Citation Format: Arlene Chan, Eugene Moylan, Sally Jackson, Jeannette Devoto, Nicola Jones, Silvie Radmil, Kate Wilkinson, Aflah Roohullah, Tamiem Adam, Seon Young Lee, Weon Sup Lee, Jin-San Yoo. Phase Ib trial of olinvacimab and pembrolizumab in patients with metastatic triple-negative 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 PS10-18.

Summary Background Palbociclib added to endocrine therapy improves progression-free survival in hormone-receptor-positive, HER2-negative, metastatic breast cancer. The PALLAS trial aimed to investigate whether the addition of 2 years of palbociclib to adjuvant endocrine therapy improves invasive disease-free survival over endocrine therapy alone in patients with hormone-receptor-positive, HER2-negative, early-stage breast cancer. Methods PALLAS is an ongoing multicentre, open-label, randomised, phase 3 study that enrolled patients at 406 cancer centres in 21 countries worldwide with stage II–III histologically confirmed hormone-receptor-positive, HER2-negative breast cancer, within 12 months of initial diagnosis. Eligible patients were aged 18 years or older with an Eastern Cooperative Oncology Group performance score of 0 or 1. Patients were randomly assigned (1:1) in permuted blocks of random size (4 or 6), stratified by anatomic stage, previous chemotherapy, age, and geographical region, by use of central telephone-based and web-based interactive response technology, to receive either 2 years of palbociclib (125 mg orally once daily on days 1–21 of a 28-day cycle) with ongoing standard provider or patient-choice adjuvant endocrine therapy (tamoxifen or aromatase inhibitor, with or without concurrent luteinising hormone-releasing hormone agonist), or endocrine therapy alone, without masking. The primary endpoint of the study was invasive disease-free survival in the intention-to-treat population. Safety was assessed in all randomly assigned patients who started palbociclib or endocrine therapy. This report presents results from the second pre-planned interim analysis triggered on Jan 9, 2020, when 67% of the total number of expected invasive disease-free survival events had been observed. The trial is registered with ClinicalTrials.gov (NCT02513394) and EudraCT (2014-005181-30). Findings Between Sept 1, 2015, and Nov 30, 2018, 5760 patients were randomly assigned to receive palbociclib plus endocrine therapy (n=2883) or endocrine therapy alone (n=2877). At the time of the planned second interim analysis, at a median follow-up of 23·7 months (IQR 16·9–29·2), 170 of 2883 patients assigned to palbociclib plus endocrine therapy and 181 of 2877 assigned to endocrine therapy alone had invasive disease-free survival events. 3-year invasive disease-free survival was 88·2% (95% CI 85·2–90·6) for palbociclib plus endocrine therapy and 88·5% (85·8–90·7) for endocrine therapy alone (hazard ratio 0·93 [95% CI 0·76–1·15]; log-rank p=0·51). As the test statistic comparing invasive disease-free survival between groups crossed the prespecified futility boundary, the independent data monitoring committee recommended discontinuation of palbociclib in patients still receiving palbociclib and endocrine therapy. The most common grade 3–4 adverse events were neutropenia (1742 [61·3%] of 2840 patients on palbociclib and endocrine therapy vs 11 [0·3%] of 2903 on endocrine therapy alone), leucopenia (857 [30·2%] vs three [0·1%]), and fatigue (60 [2·1%] vs ten [0·3%]). Serious adverse events occurred in 351 (12·4%) of 2840 patients on palbociclib plus endocrine therapy versus 220 (7·6%) of 2903 patients on endocrine therapy alone. There were no treatment-related deaths. Interpretation At the planned second interim analysis, addition of 2 years of adjuvant palbociclib to adjuvant endocrine therapy did not improve invasive disease-free survival compared with adjuvant endocrine therapy alone. On the basis of these findings, this regimen cannot be recommended in the adjuvant setting. Long-term follow-up of the PALLAS population and correlative studies are ongoing. Funding Pfizer.

Purpose In the MONALEESA-3 Phase III trial of patients with hormone receptor–positive human epidermal growth factor receptor–negative advanced breast cancer, ribociclib plus fulvestrant significantly improved progression-free survival (PFS) and overall survival (OS). Here, we present patient-reported outcomes from the trial, including health-related quality of life (HRQOL). Methods Patients were randomized (2:1) to receive ribociclib plus fulvestrant or placebo plus fulvestrant. Time to definitive 10% deterioration (TTD) from baseline in HRQOL (global health status [GHS] from the EORTC QLQ-C30 questionnaire) and pain (BPI-SF questionnaire) were assessed using Kaplan-Meier estimates; a stratified Cox regression model was used to estimate the hazard ratio (HR) and 95% CIs. Results Deterioration ≥10% in the EORTC-QLQ-C30 GHS was observed in 33% of patients in the ribociclib group vs 34% of patients in the placebo (reference) group (HR for TTD ≥ 10% = 0.81 [95% CI, 0.62–1.1]). Similar findings were noted for TTD ≥5% (HR = 0.79 [95% CI, 0.61–1.0]) and TTD ≥15% (HR = 0.81 [95% CI, 0.60–1.08]). TTD ≥10% in emotional functioning (HR = 0.76 [95% CI, 0.57–1.01]) trended in favor of the ribociclib group, whereas results for fatigue and pain were similar between arms. TTD ≥10% in BPI-SF pain severity index score (HR = 0.77 [95% CI, 0.57–1.05]) and worst pain item score (HR = 0.81 [95% CI, 0.58–1.12]) trended in favor of ribociclib vs placebo. Conclusions In addition to significantly prolonging PFS and OS compared with placebo plus fulvestrant, adding ribociclib to fulvestrant maintains HRQOL., Highlights • Ribociclib + fulvestrant allowed maintenance of global health status (GHS). • Time to deterioration (TTD) by 10% can convey duration until worsening of QOL. • TTD ≥10% was delayed with ribociclib in GHS and emotional functioning. • Ribociclib also demonstrated trends toward delayed TTD vs placebo in pain outcomes.

Purpose:The primary objective was to evaluate intracranial objective response rate (iORR) in patients receiving abemaciclib with brain or leptomeningeal metastases (LM) secondary to hormone receptor–positive (HR+) metastatic breast cancer (MBC). Secondary objectives evaluated extracranial response, abemaciclib pharmacokinetics, brain metastases tissue exposure, and safety.Patients and Methods:This nonrandomized, phase II study (NCT02308020) enrolled patients in tumor subtype–specific cohorts A–D: A (HR+, HER2− MBC), B (HR+, HER2+ MBC), C (HR+ MBC LM), and D (brain metastases surgical resection). Abemaciclib 200 mg was administered twice daily as monotherapy or with endocrine therapy, or 150 mg twice daily with trastuzumab. Cohorts A and B used a Simon two-stage design.Results:In cohort A (n = 58), 3 patients were confirmed responders resulting in an iORR of 5.2% [95% confidence interval (CI), 0.0–10.9], and the intracranial clinical benefit rate (iCBR) was 24% (95% CI, 13.1–35.2). Median overall survival (OS) was 12.5 months (95% CI, 9.3–16.4). A volumetric decrease in target intracranial lesions was experienced by 38% of patients. In cohort B (n = 27), there were no confirmed intracranial responses. An iCBR of 11% (95% CI, 0.0–23.0) was observed. Median OS was 10.1 months (95% CI, 4.2–14.3). A volumetric decrease in target intracranial lesions was experienced by 22% of patients. In cohort C (n = 10), one confirmed complete parenchymal response was observed. In cohort D (n = 9), unbound brain metastases concentrations of total active abemaciclib analytes were 96- [cyclin-dependent kinase 4 (CDK4)] and 19-fold (CDK6) above in vitro IC50. Safety was consistent with prior studies.Conclusions:This study did not meet its primary endpoint. Abemaciclib was associated with an iCBR of 24% in patients with heavily pretreated HR+, HER2− MBC. Abemaciclib achieved therapeutic concentrations in brain metastases tissue, far exceeding those necessary for CDK4 and CDK6 inhibition. Further studies are warranted, including assessing novel abemaciclib-based combinations.

Background: Chemotherapy treatments with robust efficacy that preserve quality of life are needed. Tesetaxel is a novel, oral taxane that has potential advantages over currently available taxanes, including: oral administration with a low pill burden and once every 3 week (Q3W) dosing; no observed hypersensitivity reactions; preclinical evidence of central nervous system (CNS) penetration; and improved activity against chemotherapy-resistant tumors. More than 600 patients have been treated with tesetaxel in clinical studies. Tesetaxel had robust 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%. CONTESSA TRIO investigates tesetaxel plus 3 different PD-(L)1 inhibitors in patients with TNBC and tesetaxel monotherapy in elderly patients with HER2- MBC. Trial design: CONTESSA TRIO is a 2-cohort, multinational, multicenter, Phase 2 study. In Cohort 1, 90 patients (with potential expansion to up to 150 patients) with metastatic TNBC who have not received prior chemotherapy for advanced disease will be randomized 1:1:1 to receive tesetaxel at 27 mg/m2 Q3W plus either: (1) nivolumab at 360 mg Q3W; (2) pembrolizumab at 200 mg Q3W; or (3) atezolizumab at 1,200 mg Q3W. Nivolumab and pembrolizumab (PD-1 inhibitors) and atezolizumab (a PD-L1 inhibitor) are approved for the treatment of multiple types of cancer; atezolizumab, in combination with nab-paclitaxel, was recently approved in the U.S. for the treatment of metastatic TNBC. The dual primary endpoints for Cohort 1 are ORR and progression-free survival (PFS). A sample size of 30 patients in each PD-(L)1 inhibitor treatment group has approximately 70% power to detect an ORR difference of 35% or greater between the treatment group with the highest ORR and the treatment group with the lowest ORR. An increase in the sample size to 50 patients in each treatment group will increase the power to approximately 85%. Secondary endpoints include duration of response (DoR) and overall survival (OS). Efficacy results for each of the 3 PD-(L)1 inhibitor combinations will be assessed for correlation with the results of each of the 3 approved PD-L1 diagnostic assays. CONTESSA TRIO is the first randomized clinical study to compare 3 approved PD-(L)1 inhibitors. In Cohort 2, 40 elderly patients (with potential expansion to up to 60 patients) with HER2- MBC who have not received prior chemotherapy for advanced disease will receive tesetaxel monotherapy at 27 mg/m2 Q3W. The primary endpoint for Cohort 2 is ORR. A sample size of 40 will allow the ORR to be estimated with a maximum standard error of < 8%. An increase in the sample size to 60 patients will decrease the maximum standard error to < 6.5%. Secondary endpoints include PFS, DoR and OS. Patients with CNS metastases are eligible for both cohorts. The Study was initiated in March 2019. For further information on this trial, email joconnell@odonate.com or visit clinicaltrials.gov (NCT03952325). Citation Format: Sara Tolaney, Joanne Blum, Igor Bondarenko, Arlene Chan, Noshir DaCosta, Yin-Hsun Feng, Yann Izarzugaza, Sung-Bae Kim, Mei-Ching Liu, Maria Eva Peréz Lopéz, Mafalda Oliveira, Samuel Guan Wei Ow, Michel Pavic, Hope Rugo, Lee Schwartzberg, Agostina Stradella, Stew Kroll, Joseph O'Connell, Thomas Wei, Elizabeth Mittendorf. CONTESSA TRIO: A multinational, multicenter, phase 2 study of tesetaxel plus 3 different PD-(L)1 inhibitors in patients with metastatic triple-negative breast cancer (TNBC) and tesetaxel monotherapy in elderly patients with HER2- metastatic breast cancer (MBC) [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 OT1-08-08.

Background: Neratinib (NERLYNX®), an irreversible pan-HER tyrosine kinase inhibitor, is used for the extended adjuvant treatment of patients with early-stage HER2-positive (HER2+) breast cancer following adjuvant trastuzumab-based therapy. Diarrhea is the main tolerability concern with neratinib and is common in the absence of proactive management. The CONTROL study (Clinicaltrials.gov: NCT02400476) is investigating the effectiveness of rationally structured antidiarrheal prophylaxis or neratinib dose escalation in the prevention of neratinib-associated diarrhea. CONTROL includes antidiarrheal prophylactic regimens with loperamide either alone or in combination with budesonide (locally acting corticosteroid) or colestipol (bile acid sequestrant), as well as two different neratinib dose-escalation schedules. Updated findings from CONTROL are reported. Methods: CONTROL is an international, multi-cohort, open-label, phase II study. Patients ≥18 years of age with stage I-IIIc HER2+ breast cancer were treated with oral neratinib (240 mg/day for 1 year) after trastuzumab-based adjuvant therapy. Patients were enrolled sequentially into separate cohorts investigating: 1) mandatory loperamide prophylaxis; 2) budesonide + loperamide prophylaxis; 3) colestipol + loperamide prophylaxis; 4) colestipol + loperamide prn; 5) neratinib dose escalation + loperamide prn (two cohorts). Adverse events were graded according to NCI-CTCAE v4.0. Primary endpoint: incidence of grade ≥3 diarrhea. Data cut-off: 17 June 2019. Results: A total of 514 patients have been enrolled. At the cut-off date, study treatment had been completed by 100% of patients in all cohorts except for the two neratinib dose-escalation cohorts (the colestipol + loperamide prn cohort had just 1 patient continuing treatment as of the cut-off date). All preventive strategies reduced the incidence of grade 3 diarrhea (Table) compared with that seen in ExteNET (historical control: 39.9%). Median cumulative duration of grade 3 diarrhea across the study cohorts ranged from 2-5 days for the entire 12-month treatment period. The proportion of patients discontinuing neratinib because of diarrhea was decreased in all cohorts compared with ExteNET (16.8%), except for Cohort 1. The majority of adverse events (including diarrhea) leading to treatment discontinuation occurred early while on treatment, primarily during the first or second cycle. Table. Characteristics of treatment-emergent diarrheaLoperamide (n=137)Budesonide + loperamide (n=64)Colestipol + loperamide (n=136)Colestipol + loperamide prn (n=104)Neratinib dose escalation scheme 1 (n=60)Neratinib dose escalation scheme 2 (n=13)On neratinib treatment, %0001.0a85.084.6Diarrhea, %Grade 124.125.027.930.841.723.1Grade 224.832.834.632.738.346.2Grade 330.728.120.631.715.07.7Grade 4000000Median cumulative duration, days (range)Grade ≥25.0 (1-400)6.0 (1-117)4.0 (1-371)8.0 (1-375)5.0 (1-28)2.0 (1-6)Grade 33.0 (1-93)2.5 (1-6)3.5 (1-22)3.0 (1-55)2.0 (1-5)5.0 (5-5)Discontinuation (due to a diarrhea TEAE), %20.410.94.47.73.30Hospitalization (due to a diarrhea TEAE), %1.500000aAs of the data cut-off, the final patient in the colestipol + loperamide prn cohort had completed 1 year of neratinib treatment but had not yet had the final study visit. Conclusions: The addition of budesonide or colestipol to loperamide prophylaxis given for 1-2 cycles reduces the incidence, severity and duration of neratinib-associated diarrhea. These strategies reduce the rate of neratinib discontinuation due to diarrhea, allowing patients to receive the benefits of 1 year of extended adjuvant neratinib therapy. Early findings with escalating the dose of neratinib over the first 2-4 weeks of treatment are promising. Updated data for the two neratinib dose-escalation cohorts will be presented at the meeting. Citation Format: Arlene Chan, Sara A Hurvitz, Gavin Marx, Manuel Ruiz-Borrego, Cynthia Farrell, Daniel Hunt, Leanne McCulloch, A Jo Chien, Debu Tripathy, Carlos H Barcenas, the CONTROL Investigators. Effect of prophylaxis or neratinib dose escalation on neratinib-associated diarrhea and tolerability in patients with HER2-positive early-stage breast cancer: Phase II CONTROL trial [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 P5-14-03.

Background: Abemaciclib is an oral selective inhibitor of cyclin-dependent kinases 4 and 6 approved for hormone receptor (HR)+, human epidermal growth factor receptor 2 (HER2)- metastatic breast cancer. In the randomized, 3-arm, phase 2 study monarcHER (NCT02675231) for HR+, HER2+ advanced breast cancer (ABC), abemaciclib in combination with trastuzumab (T) and fulvestrant (F) significantly improved investigator-assessed progression-free survival (whereas abemaciclib + T did not) versus (vs) T + physician’s choice of chemotherapy and demonstrated a tolerable safety profile. Here, patient-reported HRQoL, functioning, and symptoms are reported. Methods: In monarcHER, 237 postmenopausal (surgical, natural, or chemical ovarian suppression) women with ABC and ≥2 prior HER2+ directed therapies in the advanced setting were randomized 1:1:1 to abemaciclib (150 mg PO Q12H every 21 days) + T (IV infusion on D1 every 21 days) with F (500 mg IM on Cycle 1 D1 and D15 and Cycle 2 D8, then Q4W; Arm A) or without F (Arm B) vs T + physician’s choice of chemotherapy (per label every 21 days; Arm C). Supportive measures to manage diarrhea were permitted. Patient-reported outcomes were measured at baseline and at each cycle using the modified Brief Pain Inventory-short form (mBPI-sf) and European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30). The EuroQol 5-Dimension 5 Level (EQ-5D 5L) questionnaire was also collected. Higher scores on EORTC QLQ-C30 functional and health status/QoL scales indicate improvement whereas higher scores on EORTC QLQ-C30 symptom scales and mBPI-sf indicate worsening of symptoms/pain. The EQ-5D 5L index score was calculated from a set of item weights to derive a score of 0-1, with 1 representing the best health status. Treatment arm comparisons of change from baseline (all post-baseline visits) were conducted using a mixed model repeated measure, with .05 considered statistically significant. Clinical meaningfulness was defined as a ≥10-point score change from baseline (on a 0-100 scale) for EORTC QLQ-C30 and a 2-point score change from baseline for mBPI-sf. Results: Patient-reported outcome compliance rates were ≥90% through Cycle 15; the range for median duration of each treatment component of each arm was 7.5-10.0 cycles. Overall, no statistically significant or clinically meaningful changes from baseline differences were observed between treatment arms for mBPI-sf pain scores or EORTC QLQ-C30 global health score, function scales, or for symptoms of fatigue, dyspnea, appetite loss, or financial difficulties. Least square (LS) mean change from baseline differences showed statistically significant improvements in Arm A vs C for EORTC QLQ-C30 symptoms of pain (-6.81; p=.026) and insomnia (-6.39; p=.041). Worsening for the symptom of nausea/vomiting was statistically significant but not clinically meaningful in Arm A vs C (4.08; p=.043). Diarrhea showed a statistically significant and clinically meaningful worsening in Arm A vs C (19.27; p Conclusions: Quality of life was maintained for patient-reported pain, global health, functioning, and most symptoms when abemaciclib was added to T + F compared with physician’s choice of chemotherapy in patients with HR+, HER2+ ABC. Gastrointestinal-related symptoms were transient and consistent with the manageable, reversible adverse event profile. Citation Format: Sara M Tolaney, Andrew M Wardley, Stefania Zambelli, John F. Hilton, Tiffany A Troso-Sandoval, Francesco Ricci, Seock-Ah Im, Sung-Bae Kim, Stephen RD Johnston, Arlene Chan, Shom Goel, Kristen Catron, Zhengyu Yang, M. Corona Gianford, Gregory L Price, Fabrice André. Health-related quality of life (HRQoL) in monarcHER: Abemaciclib plus trastuzumab with or without fulvestrant versus trastuzumab plus standard-of-care chemotherapy in HR+, HER2+ advanced breast cancer [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 P3-11-10.

Background: Recently neoadjuvant chemotherapy (NACT) is regarded as a potential standard approach whenever chemotherapy is indicated in principle and is considered as the preferred treatment approach for stage II/III triple-negative and HER2-positive BC. However, there is an urgent need to develop a more sensitive and robust test that can assess the response for NACT and guide the optimum adjuvant therapy. Aim: Our aim is to identify molecular, radiological and histopathologic criteria that could grade response to NACT and to develop a robust prognostic index that accurately predict clinical outcome of the subsequent adjuvant therapy. Method: Comprehensive histopathological and radiological assessment of consecutive series of 850 BC [T2-4, N0-3, M0] have been centrally carried out at the Nottingham University Hospital (NUH). Furthermore, the immunohistochemistry expression of Ki67 and SPAG5 proliferation biomarkers and the histological evaluation of tumour infiltration lymphocytes (TILs) had been examined in all patients while both volumetric and texture changes detected by magnetic resonance imaging (MRI) were available for 400 cases. Oestrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) were assessed according to the most recent American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines. The results were validated in an external cohort of 250 cases. The patient’s characteristics and treatment options are the same between the centres: (68%) has received anthracycline plus Taxane (AC+T) NACT and 32% of patients have received NACT Anthracycline only (AC). Neoadjuvant HER2 targeting agents (Trastuzumab) or (Trastuzumab + Petruzumab) had been prescribed to 16% of patients in addition to AC+T followed by adjuvant Trastuzumab (total=18 cycles). All pre-NACT ER+ patients were given at least 5 year of adjuvant endocrine therapy. The primary end point was disease free survival (DFS). The median follow up was 72 months. Results: Using multivariate Cox proportional hazards models with backward stepwise exclusion for DFS, we found the presence of TILs [(HR (95% CI): 0.68 (0.48-0.94; P=0.022], high SPAG5 expression in post-surgical tumour tissue [(HR (95% CI): 2.58 (1.19-5.63), p=0.017)], the reduction in the primary tumour volume measured by MRI (>30%) [(HR(95% CI): 0.38 (0.16-0.89), p=0.026)], presence of Lymphovascular invasion [(HR(95% CI): 2.92 (1.33-6.40), p=0.008)], presence of chemotherapy induced fibrosis [(HR(95% CI): 0.41 (0.19-0.91), p=0.029)] and the high histological grade [(HR(95% CI): 2.62 (1.19-5.74), p=0.016)] showed statistical significant association with DFS. A prognostic index was calculated using the aforementioned factors after adjusting for both NACT and adjuvant therapy. The receiver-operating characteristic (ROC) curves indicated that this model is a good prognostic test [AUC = 0.854 (95% CI) = 0.777-.0.931; p= 0.00000001] and it outperformed residual cancer burden (RCB score) [AUC = 0. 711 (95% CI) = 0.612-.0.810; P= 0.0003]; and other NACT response grading systems including Miller-Payne system, Clinical-Pathologic Scoring System (CPS) and CPS-ER histological grade (CPS-EG) systems. Conclusion: A prognostic test with high sensitivity and specificity for assessing response to Neo-ACT has been developed and applying this test could guide the choice of the optimal adjuvant therapy. Citation Format: Tarek M. a. Abdel-Fatah, Xin Chen, Ruizhe Li, Elisabetta Giannotti, Dorothee Auer, Jennifer Walker, Jun Lim, A. Graham Pockley, Graham Ball, Emad Rakhah, Ian Ellis, Arlene Chan, Stephen Chan. Developing a robust multidimensional molecular, pathological and radiological prognostic index (MPRPI) to evaluate the response to neoadjuvant chemotherapy (NACT) and predict clinical outcome of breast cancer (BC) [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 P3-07-02.