HER2-positive Breast Cancer Brain Metastases Research Articles

Abstract P2-13-15: VRN101396, a brain-permeable HER2 inhibitor, shows the anti-tumor activity in preclinical HER2-positive cancer models

Abstract Breast cancer (BC) is the second most common cancer associated with brain metastasis (BM) and among patients with breast cancer brain metastasis (BCBM), human epidermal growth factor receptor 2 (HER2)-positive breast cancer is most likely to develop BM. The overall prognosis of HER2-positive BCBM remains dismal with median survival time after BM of less than a year. Drugs like T-DM1, T-DXd and Tucatinib are reported to deliver a progression-free survival benefit in HER2-positive BCBM patients, but there are still unmet needs for a drug that crosses the blood brain barrier more effectively. We develop VRN101396, a brain penetrant, orally available, and irreversible small molecule inhibitor targeting HER2 to offer a new therapeutic option for the treatment of HER2-positive BCBM. VRN101396 potently inhibits catalytic activity of HER2 but spares wild-type EGFR. In HER2-positive breast cancer cell lines BT474 and SK-BR3 and gastric cancer cell line NCI-N87, VRN101396 inhibited the cell proliferation and phosphorylation of HER2 with single- or double-digit nanomolar IC50 values while inhibiting wild type EGFR with an IC50 value of >100 nM. In both subcutaneous and intracranial efficacy mouse models, once-daily oral dose of VRN101396 significantly inhibited tumor growth and achieved tumor regression. In N87 subcutaneous xenograft model, VRN101396 alone showed superior efficacy to the combination of Tucatinib and Trastuzumab. Additionally, in intracranial xenograft model, VRN101396 showed superior efficacy to Tucatinib. Pharmacokinetics of VRN101396 displayed higher brain exposure than tucatinib and lapatinib, indicating better target engagement in the brain. Pharmacodynamic analysis revealed that VRN101396 reduced phosphorylation of HER2, HER3, AKT, and ERK compared to vehicle group after administration up to 24 hours. In conclusion, VRN101396 is a therapeutic candidate for the treatment of HER2-positive BC, BCBM and gastric cancer. Citation Format: Hong-ryul Jung, Sunghwan Kim, Jihye Yoo, Chan mi Park, Somi Lee, Hyoju Lee, Youngyi Lee, Jinhee Park, Kyungah Seo, Dong-Hyuk Seo, Eunhwa Ko, Jung Beom Son, Deakwon Kim, Hwan Geun Choi, Nam Doo Kim. VRN101396, a brain-permeable HER2 inhibitor, shows the anti-tumor activity in preclinical HER2-positive cancer models [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-15.

Performance of enhancement on brain MRI for identifying HER2 overexpression in breast cancer brain metastases

PurposeTo investigate whether enhancement on MRI could help identify HER2 overexpression in breast cancer brain metastases. MethodsWe derived a cohort of 38 histologically proven breast cancer brain metastases with preoperative contrast-enhanced brain MRI and HER2 fluorescent in-situ hybridization of the resected/biopsied brain specimens from 2018 to 2021. Enhancement of the lesions was measured and compared using t-tests. Receiver operating characteristic and logistic regression analyses were performed to evaluate the performance of MRI enhancement in identifying HER2 overexpression. ResultsThe study cohort was comprised of 29 women with a mean age of 55 years (range: 31–81 years) with a total of 38 distinct lesions. The HER2-positive subcohort was comprised of 17 patients, while the HER2-negative subcohort was comprised of 13 patients. The percent signal intensity change (PSIC) of HER2-positive breast cancer brain metastases was significantly greater than that of HER2-negative lesions (310 v. 153, P = 0.002). The PSIC differentiated HER2-positive lesions from HER2-negative lesions with an area under the curve of 0.88 (P < 0.001). In a model controlling for lesion size, lesion location, tumor grade, patient age, scanner magnetic field strength, and contrast agent, the PSIC had an accuracy of 92% (35/38), sensitivity of 96% (23/24), and specificity of 86% (12/14) in differentiating HER2-positive lesions from HER2-negative lesions. ConclusionEnhancement on MRI may assist in identifying HER2 overexpression in breast cancer brain metastases, if validated prospectively.

Trastuzumab Emtansine (T-DM1) and stereotactic radiation in the management of HER2+ breast cancer brain metastases

BackgroundDue to recent concerns about the toxicity of trastuzumab emtansine (T-DM1) with stereotactic radiation, we assessed our institutional outcomes treating HER2-positive breast cancer brain metastases (BCBM) with T-DM1 and stereotactic radiation.MethodsThis is a single institution series of 16 patients with HER2-positive breast cancer who underwent 18 stereotactic sessions to 40 BCBM from 2013 to 2019 with T-DM1 delivered within 6 months. The Kaplan-Meier method was used to calculate overall survival (OS), local control (LC), distant intracranial control (DIC), and systemic progression-free survival (sPFS) from the date of SRS. A neuro-radiologist independently reviewed follow-up imaging.ResultsOne patient had invasive lobular carcinoma, and 15 patients had invasive ductal carcinoma. All cases were HER2-positive, while 10 were hormone receptor (HR) positive. Twenty-four lesions were treated with stereotactic radiosurgery (SRS) to a median dose of 21 Gy (14–24 Gy). Sixteen lesions were treated with fractionated stereotactic radiation (FSRT) with a median dose of 25 Gy (20-30Gy) delivered in 3 to 5 fractions. Stereotactic radiation was delivered concurrently with T-DM1 in 19 lesions (48%). Median follow up time was 13.2 months from stereotactic radiation. The 1-year LC, DIC, sPFS, and OS were 75, 50, 30, and 67%, respectively. There was 1 case of leptomeningeal progression and 1 case (3%) of symptomatic radionecrosis.ConclusionsWe demonstrate that stereotactic radiation and T-DM1 is well-tolerated and effective for patients with HER2-positive BCBM. An increased risk for symptomatic radiation necrosis was not noted in our series.

Favourable outcome of patients with breast cancer brain metastases treated with dual HER2 blockade of trastuzumab and pertuzumab.

Background:Dual human epidermal growth factor receptor 2 (HER2) blockade with trastuzumab and pertuzumab (TP) is a standard therapy of metastatic and localized HER2-positive breast cancer (BC), but its activity in breast cancer brain metastases (BCBM) is unknown.Methods:Patients with HER2-positive BCBM were identified from the Vienna Brain Metastasis Registry and clinical data including patient characteristics, therapies and overall survival (OS) were obtained. Patients were grouped into ‘TP’, ‘other-HER2-targeted therapy’ and ‘no-HER2-targeted therapy’ according to received first-line systemic therapy after diagnosis of BCBM. Radiological re-assessment of intracranial lesions was performed in patients treated with TP as systemic first-line therapy according to RANO response criteria for brain metastases (BM).Results:A total of 252 HER2-positive BC patients with BM were available for this analysis. Patients treated with TP as systemic first-line therapy after diagnosis of BM had a significantly longer OS compared with treatment with other-HER2-targeted therapy and no-HER2-targeted therapy (44 versus 17 versus 3 months, p < 0.001; log-rank test). Among radiologically re-assessed patients treated with TP as systemic first-line therapy after diagnosis of BM, 5/14 patients (35.7%) had complete intracranial remission (CR), 8/14 patients (57.1%) partial intracranial remission (PR), 1/14 patients (7.1%) stable intracranial disease (SD) and 0/14 patients (0.0%) progressive intracranial disease (PD) as best response resulting in an intracranial objective response rate (iORR) of 92.9% and an intracranial clinical benefit rate (iCBR) of 100.0%.Conclusion:First-line therapy with dual HER2-inhibition of TP after BM diagnosis was associated with the longest median OS times in patients with BCBM.

HER2-positive breast cancer brain metastasis: A new and exciting landscape.

BackgroundBrain metastases (BrM) incidence is 25% to 50% in women with advanced human epidermal growth factor receptor 2 (HER2)‐positive breast cancer. Radiation and surgery are currently the main local treatment approaches for central nervous system (CNS) metastases. Systemic anti‐HER2 therapy following a diagnosis of BrM improves outcomes. Previous preclinical data has helped elucidate HER2 brain trophism, the blood‐brain/blood‐tumor barrier(s), and the brain tumor microenvironment, all of which can lead to development of novel therapeutic options.Recent findingsSeveral anti‐HER2 agents are currently available and reviewed here, some of which have recently shown promising effects in BrM patients, specifically. New strategies driven by and focusing on brain metastasis‐specific genomics, immunotherapy, and preventive strategies have shown promising results and are under development.ConclusionsThe field of HER2+ breast cancer, particularly for BrM, continues to evolve as new therapeutic strategies show promising results in recent clinical trials. Increasing inclusion of patients with BrM in clinical studies, and a focus on assessing their outcomes both intracranially and extracranially, is changing the landscape for patients with HER2+ CNS metastases by demonstrating the ability of newer agents to improve outcomes.

Management of brain metastases according to molecular subtypes.

The incidence of brain metastases has markedly increased in the past 20 years owing to progress in the treatment of malignant solid tumours, earlier diagnosis by MRI and an ageing population. Although local therapies remain the mainstay of treatment for many patients with brain metastases, a growing number of systemic options are now available and/or are under active investigation. HER2-targeted therapies (lapatinib, neratinib, tucatinib and trastuzumab emtansine), alone or in combination, yield a number of intracranial responses in patients with HER2-positive breast cancer brain metastases. New inhibitors are being investigated in brain metastases from ER-positive or triple-negative breast cancer. Several generations of EGFR and ALK inhibitors have shown activity on brain metastases from EGFR and ALK mutant non-small-cell lung cancer. Immune-checkpoint inhibitors (ICIs) hold promise in patients with non-small-cell lung cancer without druggable mutations and in patients with triple-negative breast cancer. The survival of patients with brain metastases from melanoma has substantially improved after the advent of BRAF inhibitors and ICIs (ipilimumab, nivolumab and pembrolizumab). The combination of targeted agents or ICIs with stereotactic radiosurgery could further improve the response rates and survival but the risk of radiation necrosis should be monitored. Advanced neuroimaging and liquid biopsy will hopefully improve response evaluation.

Phase I dose-escalation trial of tucatinib in combination with trastuzumab in patients with HER2-positive breast cancer brain metastases

Brain metastases are frequent in HER2-positive breast cancer. ONT-380 (tucatinib) is a potent selective inhibitor of HER2 with intracranial activity in preclinical models. This was a phase I study of tucatinib with trastuzumab, without chemotherapy, in patients with progressive, measurable HER2-positive brain metastases. The study tested two schedules of tucatinib: cohort A was twice daily and cohort B was once daily. The primary objective was determination of the maximum tolerated dose (MTD). Secondary end points included objective response (intracranial and extracranial) using modified RECIST and clinical benefit rate (CBR). Overall, 41 patients were enrolled (cohort A, n= 22; cohort B, n= 19). Patients had a median of two prior treatments for metastatic breast cancer and 83% had progressed after prior brain radiation. The MTD of tucatinib for cohort A was 300 mg twice daily and for cohort B was 750 mg once daily. The most common dose-limiting toxicities included thrombocytopenia and aspartate transaminase/alanine aminotransferase elevation. Grade 3/4 aspartate transaminase/alanine aminotransferase elevation occurred in nine of 41 patients (22%). Intracranial responses were observed in two of 17 (12%) patients in cohort A and one of 17 (6%) patients in cohort B treated at the MTD. In cohort A, CBR at 16 weeks was 35% (n= 6). In cohort B, CBR at 16 weeks was 53% (n= 9). Of 15 patients overall who experienced clinical benefit, 12 (80%) had received prior neratinib and/or lapatinib. Median progression-free survival for cohorts A and B was 3.4 and 4.1 months, respectively. The combination of tucatinib and trastuzumab is tolerable and demonstrated preliminary evidence of efficacy in patients with HER2-positive brain metastases. NCT01921335.

Phase I/II study of T-DM1 alone versus T-DM1 and metronomic temozolomide in secondary prevention of HER2-positive breast cancer brain metastases following stereotactic radiosurgery.

TPS2572 Background: We demonstrated that low doses of temozolomide (TMZ) administered in a prophylactic, metronomic fashion significantly prevented development of brain metastases in murine models of breast cancer. Based on these findings, we developed a secondary-prevention clinical trial. Methods: Phase I is a standard 3+3 design: T-DM1 3.6mg/kg IV every 21 days plus TMZ 30, 40 or 50 mg/m2 daily, to identify the maximum tolerated dose (MTD) of the combination, and is completing accrual, with 9 patients accrued, currently on the third and last dose level. Phase II will randomize patients to T-DM1 3.6mg/kg versus T-DM1 3.6mg/kg plus TMZ at recommended phase 2 dose (RP2D), to evaluate if addition of TMZ improves the recurrence-free incidence from distant new brain metastases at one year from 50% to 65%. Patients will undergo radiology guided lumbar puncture at baseline and after 6 weeks of treatment (C3D1) for correlative studies, brain MRI, systemic restaging CTs, and questionnaires for evaluation of symptoms and quality of life. Eligibility: HER2+ breast cancer with brain metastases (up to 10 lesions), treated with SRS and/or resection ≤12 weeks before enrollment, no leptomeningeal metastases, no previous WBRT, ECOG ≤2 and adequate organ and marrow function. Biomarkers, including cell free DNA from CSF, serum and tumor block, exosomal DNA, serum markers for neuroinflammation, and patient reported outcomes, will be analyzed in an exploratory fashion. Target accrual: up to 18 patients in phase I and 98 in phase II. Clinical trial information: NCT03190967 .

Landscape of combination therapy trials in breast cancer brain metastasis.

Combination therapy has become a cornerstone in cancer treatment to potentiate therapeutic effectiveness and overcome drug resistance and metastasis. In this work, we explore combination trials in breast cancer brain metastasis (BCBM), highlighting deficiencies in trial design and underlining promising combination strategies. On October 31, 2019, we examined ClinicalTrials.gov for interventional and therapeutic clinical trials involving combination therapy for BCBM, without limiting for date or location. Information on trial characteristics was collected. Combination therapies used in trials were analyzed and explored in line with evidence from the medical literature. Sixty-five combination therapy trials were selected (n = 65), constituting less than 0.7% of all breast cancer trials. Most trials (62%) combined ≥2 chemotherapeutic agents. Chemotherapy with radiation was main-stay in 23% of trials. Trastuzumab was mostly used in combination (31%), followed by lapatinib (20%) and capecitabine (15%). Common strategies involved combining tyrosine kinase inhibitors with thymidylate synthase inhibitors (6 trials), dual HER-dimerization inhibitors (3 trials), microtubule inhibitors and tyrosine kinase inhibitors (3 trials), and HER-dimerization inhibitors and tyrosine kinase inhibitors (3 trials). The combination of tucatinib and capecitabine yielded the highest objective response rate (83%) in early phase trials. The triple combination of trastuzumab, tucatinib and capecitabine lowered the risk of disease progression or death by 52% in patients with HER2-positive BCBM. Combining therapeutic agents based on biological mechanisms is necessary to increase the effectiveness of available anti-cancer regimens. Significant survival benefit has yet to be achieved in future combination therapy trials. Enhancing drug delivery through blood-brain barrier permeable agents may potentiate the overall therapeutic outcomes.

Abstract OT1-08-05: Phase II trial of GDC-0084 in combination with trastuzumab for patients with HER2-positive breast cancer brain metastases (BCBM)

Abstract Background: The PI3K/Akt/mTOR is an important pathway in BCBM. Mutations in PIK3CA or PTEN loss are associated with trastuzumab resistance. Inhibition of PI3K and mTOR led to durable responses in 3 of 5 patient-derived xenografts (PDX) models of BCBM. GDC-0084 is a potent, brain-penetrant inhibitor of class I PI3K and mTOR. Methods: This is a single-center, phase II study to evaluate the efficacy of the combination of GDC-0084 with trastuzumab for the treatment of central nervous system (CNS) metastases in patients with HER2-positive breast cancer. Patients will receive GDC-0084 (45 mg daily) and trastuzumab (8 mg/kg loading dose, then 6 mg/kg every 3 weeks). Two cohorts will be enrolled: Cohort A: a single-arm, two-stage, phase II cohort; and Cohort B: a pre-surgical window cohort. Inclusion criteria include unequivocal evidence of new and/or progressive HER2-positive CNS metastases, at least one measurable (≥10 mm) CNS metastasis (Cohort A), clinical indication for CNS metastasis resection (Cohort B). Primary endpoint for Cohort A is objective response rate (ORR) in the CNS per Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM) criteria. For Cohort B, the primary endpoint is the correlation between p4EBP1 levels in the resected CNS tumor tissue from patients and intracranial response to GDC-0084/trastuzumab in the PDX model generated from the same patient. Secondary endpoints include overall survival, safety and patient-reported outcomes. Mandatory blood and cerebrospinal fluid with optional tumor biopsy will be collected at baseline, on-treatment and at progression. In Cohort A, we will enroll 37 patients in a Simon two-stage design. If ≥4 responses are seen, the regimen will be considered successful. This design has 90% power with alpha &amp;lt;10%. Cohort B will enroll 10 patients. The trial opened in February, 2019. NCT03765983. Citation Format: Jose P Leone, Lorenzo Trippa, Lindsey Milisits, Chelsea Andrews, Jennifer Ligibel, Heather Parsons, Wenya L Bi, Jean Zhao, Eric P Winer, Nancy U Lin. Phase II trial of GDC-0084 in combination with trastuzumab for patients with HER2-positive breast cancer brain metastases (BCBM) [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 OT1-08-05.

Hypothesis on the distant spread of HER2-positive breast cancer brain metastasis via the human brain glymphatic system - Clinical and imaging data

Hypothesis on the distant spread of HER2-positive breast cancer brain metastasis via the human brain glymphatic system - Clinical and imaging data

Pre- and Postoperative Neratinib for HER2-Positive Breast Cancer Brain Metastases: Translational Breast Cancer Research Consortium 022

PurposeThis pilot study was performed to test our ability to administer neratinib monotherapy before clinically recommended craniotomy in patients with HER2-positive metastatic breast cancer to the central nervous system, to examine neratinib’s central nervous system penetration at craniotomy, and to examine postoperative neratinib maintenance. Patients and MethodsPatients with HER2-positive brain metastases undergoing clinically indicated cranial resection of a parenchymal tumor received neratinib 240 mg orally once a day for 7 to 21 days preoperatively, and resumed therapy postoperatively in 28-day cycles. Exploratory evaluations of time to disease progression, survival, and correlative tissue, cerebrospinal fluid (CSF), and blood-based analyses examining neratinib concentrations were planned. The study was registered at ClinicalTrials.gov under number NCT01494662. ResultsWe enrolled 5 patients between May 22, 2013, and October 18, 2016. As of March 1, 2019, patients had remained on the study protocol for 1 to 75+ postoperative cycles pf therapy. Two patients had grade 3 diarrhea. Evaluation of the CSF showed low concentrations of neratinib; nonetheless, 2 patients continued to receive therapy without disease progression for at least 13 cycles, with one on-study treatment lasting for nearly 6 years. Neratinib distribution in surgical tissue was variable for 1 patient, while specimens from 2 others did not produce conclusive results as a result of limited available samples. ConclusionNeratinib resulted in expected rates of diarrhea in this small cohort, with 2 of 5 patients receiving the study treatment for durable periods. Although logistically challenging, we were able to test a limited number of CSF- and parenchymal-based neratinib concentrations. Our findings from resected tumor tissue in one patient revealed heterogeneity in drug distribution and tumor histopathology.

Neoadjuvant neratinib promotes ferroptosis and inhibits brain metastasis in a novel syngeneic model of spontaneous HER2+ve breast cancer metastasis

BackgroundHuman epidermal growth factor receptor-2 (HER2)-targeted therapies prolong survival in HER2-positive breast cancer patients. Benefit stems primarily from improved control of systemic disease, but up to 50% of patients progress to incurable brain metastases due to acquired resistance and/or limited permeability of inhibitors across the blood-brain barrier. Neratinib, a potent irreversible pan-tyrosine kinase inhibitor, prolongs disease-free survival in the extended adjuvant setting, and several trials evaluating its efficacy alone or combination with other inhibitors in early and advanced HER2-positive breast cancer patients are ongoing. However, its efficacy as a first-line therapy against HER2-positive breast cancer brain metastasis has not been fully explored, in part due to the lack of relevant pre-clinical models that faithfully recapitulate this disease. Here, we describe the development and characterisation of a novel syngeneic model of spontaneous HER2-positive breast cancer brain metastasis (TBCP-1) and its use to evaluate the efficacy and mechanism of action of neratinib.MethodsTBCP-1 cells were derived from a spontaneous BALB/C mouse mammary tumour and characterised for hormone receptors and HER2 expression by flow cytometry, immunoblotting and immunohistochemistry. Neratinib was evaluated in vitro and in vivo in the metastatic and neoadjuvant setting. Its mechanism of action was examined by transcriptomic profiling, function inhibition assays and immunoblotting.ResultsTBCP-1 cells naturally express high levels of HER2 but lack expression of hormone receptors. TBCP-1 tumours maintain a HER2-positive phenotype in vivo and give rise to a high incidence of spontaneous and experimental metastases in the brain and other organs. Cell proliferation/viability in vitro is inhibited by neratinib and by other HER2 inhibitors, but not by anti-oestrogens, indicating phenotypic and functional similarities to human HER2-positive breast cancer. Mechanistically, neratinib promotes a non-apoptotic form of cell death termed ferroptosis. Importantly, metastasis assays demonstrate that neratinib potently inhibits tumour growth and metastasis, including to the brain, and prolongs survival, particularly when used as a neoadjuvant therapy.ConclusionsThe TBCP-1 model recapitulates the spontaneous spread of HER2-positive breast cancer to the brain seen in patients and provides a unique tool to identify novel therapeutics and biomarkers. Neratinib-induced ferroptosis provides new opportunities for therapeutic intervention. Further evaluation of neratinib neoadjuvant therapy is warranted.

BSCI-09. MECHANISMS OF ENHANCED DRUG DELIVERY IN BRAIN METASTASES WITH FOCUSED ULTRASOUND-INDUCED BLOOD-TUMOR BARRIER DISRUPTION

Blood-brain/blood-tumor barriers (BBB and BTB) and interstitial transport may constitute major obstacles to the transport of therapeutics in brain tumors. In this study, we examined the impact of focused ultrasound (FUS) in combination with microbubbles on the transport of two relevant chemotherapy-based anticancer agents in HER2-positive breast cancer brain metastases at cellular resolution: the non-targeted chemotherapeutic doxorubicin and the antibody-drug conjugate ado- trastuzumab emtansine (T-DM1). Using an orthotopic xenograft model of HER2-positive breast cancer brain metastasis and quantitative microscopy we demonstrate multifold increases in the extravasation of both agents (7-fold and 2-fold for doxorubicin and T-DM1, respectively) and we provide evidence of increased drug penetration (>100μm vs. < 20μm and 42±7μm vs. 12±4μm for doxorubicin and T-DM1, respectively) after application of FUS as compared to control (non-FUS). Integration of experimental data with physiologically based pharmacokinetic (PBPK) modeling of drug transport reveals that FUS in combination with microbubbles alleviates vascular barriers and enhances interstitial convective transport via increase in hydraulic conductivity. Combination of experimental data and PBPK modeling suggests that FUS in combination with microbubbles increases the endothelial cell transmembrane transport and uptake. PBPK modelling indicates selective increase in transvascular transport of the non- targeted small chemotherapeutic doxorubicin through small vessel-wall pores size with a narrow range (Diameter: 10-50nm). Our work provides a quantitative framework for the optimization of FUS-drug combinations to maximize intratumoral drug delivery and facilitate the development of novel therapeutic strategies against brain metastases.

Abstract 4832: Preclinical evaluation of neratinib plus T-DM1 in orthotopic PDX models of HER2-positive breast cancer brain metastases

Abstract Up to half of patients with metastatic HER2-positive breast cancer will develop brain metastases. Breast cancer brain metastases (BCBM) are a major cause of morbidity and mortality, despite multimodal management including surgery, radiotherapy, and systemic therapies. Therefore, there is an urgent need to develop novel, efficacious therapies. Neratinib is an orally bioavailable, irreversible pan-HER tyrosine kinase inhibitor that is FDA-approved in the extended adjuvant treatment setting for HER2-positive, early breast cancer. Neratinib has only modest activity as a single agent in clinical trials of patients with HER2-positive brain metastases. Though the combination of neratinib and capecitabine results in CNS responses in up to half of patients, patients eventually develop drug resistance, and toxicities have been a concern-thus exploration of alternative neratinib combinations is of significant clinical interest. Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate with reported single-agent activity against HER2-positive BCBM. Here, we used HER2-positive orthotopic patient derived xenograft (PDX) models of BCBM to test if combining neratinib with T-DM1 could improve tumor response. PDX cells are labelled with luciferase to allow tumor growth measurement in vivo. We found that neratinib is able to reduce phosphorylated HER2 in an orthotopic PDX tumor derived from HER2-positive BCBM, indicating that neratinib can cross the BBB and inhibit HER2 activation in BCBM PDX tissues. However, in the HER2-positive DF-BM354 PDX model, single agent neratinib did not block orthotopic tumor growth compared to vehicle control as monitored by bioluminescence measurements. In contrast, combined treatment of neratinib with T-DM1 significantly reduced tumor growth compared to single agent treatment of neratinib or T-DM1 alone at earlier time points. At later time points, the combined treatment is comparable to T-DM1 alone. These data warrant further testing of neratinib alone or in combination with T-DM1 in additional BCBM PDX models to better understand drivers of resistance and susceptibility to HER2-inhibitors in HER2-positive BCBMs. Furthermore, they support the launch of a prospective clinical trial (NCT01494662) to test the efficacy and tolerability of T-DM1 in combination with neratinib in patients with progressive HER2-positive BCBM. Citation Format: Jing Ni, Yanzhi Wang, Irmina Diala, Sheheryar Kabraji, Rachel Freedman, Nancy Lin, Jean Zhao. Preclinical evaluation of neratinib plus T-DM1 in orthotopic PDX models of HER2-positive breast cancer brain metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4832.

Highlights of This Issue

Treatment options are limited for breast cancer patients with central nervous system (CNS) metastasis. The combination of capecitabine and lapatinib, at conventional doses, has activity against HER2-positive breast cancer brain metastases; however, few patients respond, especially long-term. In this study, Morikawa and colleagues evaluated the safety and toxicities associated with intermittent high dose lapatinib alternating with intermittent fixed dose capecitabine in HER2-positive breast cancer patients with CNS metastasis. This regimen resulted in manageable toxicity and promising efficacy and will inform future phase II/III trials.Hypoxia is a negative prognostic feature in nearly all cancer types and predicts treatment failure. Validated, widely available tests are lacking for clinical use. Salem and colleagues provide the first-in-human evidence that oxygen-enhanced MRI (OE-MRI) can track changes in hypoxia that are induced by radiotherapy. OE-MRI was well-tolerated in patients with non-small cell lung cancer, and radiotherapy-induced hypoxia modification was detected. OE-MRI has potential to select patients for hypoxia-modification, track therapeutic efficacy, and identify tumors that may fail immunotherapy.Immunotherapy has been ineffective for patients with pancreatic ductal adenocarcinoma (PDA). In this study, Seo and colleagues demonstrate that CD8+ T cells are often present in PDA, but are localized to the stroma, rather than immediately adjacent to cancer cells. Using slice culture live microscopy from primary PDA tumors, the authors demonstrate that inhibition of the CXCR4 chemokine receptor led to the migration of clonally expanded CD8+ T cells to the cancer cell-rich regions of the tumors. Subsequent PD-1 blockade activated effective cancer cell killing. These results provide a new basis for the rational selection of combination immunotherapy for PDA, a disease with limited treatment options.Relapse remains a major issue for patients with multiple myeloma due to the presence of minimal residual disease (MRD) posttherapy. Bispecific T cell-engager antibody therapy has been effective in the elimination of MRD in other hematological malignancies. Zuch de Zafra and colleagues describe AMG 424, a novel bispecific T-cell–recruiting antibody targeted at CD3 and CD38, the multiple myeloma surface cell marker. AMG 424 effectively killed CD38-positive cells in vitro and showed antitumor activity in mouse and nonhuman primate models. AMG 424 is a promising candidate for multiple myeloma patients and is currently in clinical development.

Stereotactic radiosurgery with concurrent lapatinib is associated with improved local control for HER2-positive breast cancer brain metastases.

With increasing survival for patients with human epidermal growth factor receptor 2-positive (HER2+) breast cancer in the trastuzumab era, there is an increased risk of brain metastasis. Therefore, there is interest in optimizing intracranial disease control. Lapatinib is a small-molecule dual HER2/epidermal growth factor receptor inhibitor that has demonstrated intracranial activity against HER2+ breast cancer brain metastases. The objective of this study was to investigate the impact of lapatinib combined with stereotactic radiosurgery (SRS) on local control of brain metastases. Patients with HER2+ breast cancer brain metastases who underwent SRS from 1997-2015 were included. The primary outcome was the cumulative incidence of local failure following SRS. Secondary outcomes included the cumulative incidence of radiation necrosis and overall survival. One hundred twenty-six patients with HER2+ breast cancer who underwent SRS to 479 brain metastases (median 5 lesions per patient) were included. Among these, 75 patients had luminal B subtype (hormone receptor-positive, HER2+) and 51 patients had HER2-enriched histology (hormone receptor-negative, HER2+). Forty-seven patients received lapatinib during the course of their disease, of whom 24 received concurrent lapatinib with SRS. The median radiographic follow-up among all patients was 17.1 months. Concurrent lapatinib was associated with reduction in local failure at 12 months (5.7% vs 15.1%, p < 0.01). For lesions in the ≤ 75th percentile by volume, concurrent lapatinib significantly decreased local failure. However, for lesions in the > 75th percentile (> 1.10 cm3), concurrent lapatinib did not significantly improve local failure. Any use of lapatinib after development of brain metastasis improved median survival compared to SRS without lapatinib (27.3 vs 19.5 months, p = 0.03). The 12-month risk of radiation necrosis was consistently lower in the lapatinib cohort compared to the SRS-alone cohort (1.3% vs 6.3%, p < 0.01), despite extended survival. For patients with HER2+ breast cancer brain metastases, the use of lapatinib concurrently with SRS improved local control of brain metastases, without an increased rate of radiation necrosis. Concurrent lapatinib best augments the efficacy of SRS for lesions ≤ 1.10 cm3 in volume. In patients who underwent SRS for HER2+ breast cancer brain metastases, the use of lapatinib at any time point in the therapy course was associated with a survival benefit. The use of lapatinib combined with radiosurgery warrants further prospective evaluation.

CADD-32. MECHANISMS OF ENHANCED DRUG DELIVERY IN BRAIN TUMORS WITH FOCUSED ULTRASOUND-INDUCED TRANSIENT BLOOD-TUMOR BARRIER DISRUPTION

Blood-brain/blood-tumor barriers (BBB and BTB) and interstitial transport may constitute major obstacles to the transport of therapeutics in brain tumors. In this study, we examined the impact of focused ultrasound (FUS) in combination with microbubbles on the transport of two relevant chemotherapy-based anticancer agents in HER2-positive breast cancer brain metastases at cellular resolution: doxorubicin, a non-targeted low molecular weight chemotherapeutic, and ado-trastuzumab emtansine (T-DM1), an antibody-drug conjugate. Using an orthotopic xenograft model of HER2-positive breast cancer brain metastasis and quantitative microscopy we demonstrate significant increases in the extravasation of both agents (7-fold and 2-fold for doxorubicin and T-DM1, respectively) and we provide evidence of increased drug penetration (>100µm vs. <20µm and 42 ± 7µm vs. 12 ± 4µm for doxorubicin and T-DM1, respectively) after application of FUS as compared to control (non-FUS). Integration of experimental data with physiologically based pharmacokinetic (PBPK) modeling of drug transport reveals that FUS in combination with microbubbles alleviates vascular barriers and enhances interstitial convective transport via an increase in hydraulic conductivity. Combination of experimental data and PBPK modeling suggests that FUS in combination with microbubbles increases the endothelial cell transmembrane transport and uptake. PBPK modeling indicates a selective increase in transvascular transport of doxorubicin through small vessel-wall pores size with a narrow range (Diameter: 10-50nm). Our work provides a quantitative framework for the optimization of FUS-drug combinations to maximize intratumoral drug delivery and facilitate the development of novel strategies to treat brain metastases.

Intrathecal Viral Vector Delivery of Trastuzumab Prevents or Inhibits Tumor Growth of Human HER2-Positive Xenografts in Mice.

Breast cancer brain metastases are a deadly sequela of primary breast tumors that overexpress human epidermal growth factor receptor 2 (HER2); median survival for patients with these tumors is 10 to 13 months from the time of diagnosis. Current treatments for HER2-positive breast cancer brain metastases are invasive, toxic, and largely ineffective. Here, we have developed an adeno-associated virus serotype 9 (AAV9) vector to express the anti-HER2 monoclonal antibody trastuzumab (Herceptin) in vivo A single prophylactic intrathecal administration of AAV9.trastuzumab vector in a novel orthotopic Rag1-/- murine xenograft model of HER2-positive breast cancer brain metastases significantly increased median survival, attenuated brain tumor growth, and preserved both the HER2 antigen specificity and the natural killer cell-associated mechanism of action of trastuzumab. When administered as a tumor treatment, AAV9.trastuzumab increased median survival. Dose-escalation studies revealed that higher doses of AAV9.trastuzumab resulted in smaller tumor volumes. Our results indicate that intrathecal AAV9.trastuzumab may provide significant antitumor activity in patients with HER2-positive breast cancer brain metastases.Significance: Intrathecal delivery of trastuzumab via adeno-associated virus has the potential to become a novel, integral part of adjuvant therapy for patients with HER2-positive breast cancer brain metastases. Cancer Res; 78(21); 6171-82. ©2018 AACR.

Stereotactic Radiosurgery with Concurrent HER2-directed Therapy is Associated with Improved Objective Response for Breast Cancer Brain Metastasis

HER2-positive breast cancer patients remain at high risk of intracranial relapse following treatment of their primary disease and experience increased rates of intracranial failure after stereotactic radiosurgery (SRS). The objective of this study was to evaluate the rates of intracranial of CNS-penetrating HER2 directed therapy with SRS. Patients with newly-diagnosed HER2-amplified breast cancer brain metastases from 2005-2014 who underwent SRS were included and divided into two cohorts based on receipt of concurrent lapatinib. The primary outcome was the magnitude of best objective response after SRS relative to pre-SRS maximum diameter. Secondary outcomes included the proportion of lesions achieving a complete response, partial response, stable disease, or progressive disease according to the RECIST criteria, along with distant intracranial failure, radiation necrosis, and overall survival. Multivariable analysis for best objective response was conducted on a per-lesion basis using multivariable linear regression and for overall survival on a per-patient basis using Cox proportional hazards modeling. Eighty-four patients with 487 brain metastases met inclusion criteria during the study period: 132 lesions (27%) were treated with SRS and concurrent lapatinib while 355 (73%) were treated with SRS without lapatinib. During the initial treatment and follow-up period, 1004 MRIs were reviewed over which 3435 measurements were made (average of 7 measurements per lesion, Range: 2-31). The best objective response was superior in the concurrent lapatinib group (median 100% vs. 70% reduction, p<0.001). Secondary outcomes were also superior in the concurrent lapatinib group, with a greater number of complete responses (58% vs. 39%, p<0.001) and lower rates of progressive disease (9% vs. 13%, p<0.001). Best objective response and overall response generally improved as lapatinib was delivered closer to SRS. After multivariable linear regression, concurrent lapatinib remained statistically significantly associated with improved objective response (mean 11.01% decrease, 95% CI 4.1 – 18.0%, p=0.002). After proportional hazards modeling, concurrent lapatinib was associated with a trend toward longer overall survival (HR 0.59, 95% CI 0.31 – 1.06, p=0.077). Distant intracranial failure rates were similar with or without lapatinib (48% vs. 49%, p=0.91). The risk of radiation necrosis was low and although the rates increased with lesion size, concurrent lapatinib did not increase this risk, even amongst the largest lesions >1.5 cm (2.0 vs. 5.5%, p=0.27). This study provides objective response data supporting the role of concurrent lapatinib with SRS for women with HER2-positive breast cancer brain metastases. Patients treated with combined therapy experienced the highest rates of lesion control, lowest rates of progressive disease, and improvements in overall survival without an increased risk of radiation necrosis.