Leisha A. Emens

Leveraging the activity of tumor vaccines with cytotoxic chemotherapy

Engaging the power of the patients own immune system to actively seek out and destroy transformed cells holds great promise for cancer therapy. Tumor vaccines offer the potential for preventing cancer in high-risk individuals, preventing disease relapse after diagnosis and initial therapy, and shifting the balance of the host-tumor interaction to mitigate the progression of advanced cancers. The therapeutic activity of tumor vaccines is limited by the sheer physical burden of the cancer itself, pathways of local immune tolerance and escape active within the tumor microenvironment, and superimposed potent systemic mechanisms of immune tolerance. In this review, we describe how cytotoxic chemotherapy can be integrated with tumor vaccines using unique doses and schedules to break down these barriers, releasing the full potential of the antitumor immune response to eradicate disease.

Abstract 2859: Inhibition of PD-L1 by MPDL3280A leads to clinical activity in patients with metastatic triple-negative breast cancer (TNBC)

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PAnnIntroduction: TNBC is a mutationally complex breast cancer subtype with poor prognosis and no current targeted therapy options. Compared with other intrinsic breast cancer subtypes, TNBC has higher programmed death-ligand 1 (PD-L1) expression levels, which may hinder antitumor T-cell responses. MPDL3280A is a monoclonal anti-PDL1 antibody, engineered for optimized efficacy and safety, that blocks signaling through the PD-L1/PD-1 and PD-L1/B7.1 pathways.nnMethods: MPDL3280A was tested in a metastatic TNBC expansion cohort as part of a multicenter Phase Ia study. Pts received MPDL3280A at 15 mg/kg, 20 mg/kg or 1200 mg flat dose IV q3w. AEs were summarized for the safety follow-up duration from the first dose to 30 days after the last dose before the clinical cutoff on Sept 2, 2014. Responses were assessed by RECIST v1.1 criteria in pts who received MPDL3280A by Jul 21, 2014, evaluable for efficacy (≥ 6-wk follow-up). PD-L1 expression on tumor-infiltrating immune cells (ICs) at baseline was centrally evaluated by IHC in archival or fresh biopsies, and pts were scored as PD-L1 IHC (IC) 0, 1, 2 or 3. Peripheral biomarkers were assayed using FACS and multiplex immunoassays.nnResults: In the TNBC cohort, 27 pts were selectively enrolled. These pts had a median age of 48 y (29-82 y) and were evaluable for safety; 52% had ECOG PS 0 and 44% had ECOG PS 1. Visceral and bone metastases were present at baseline in 59% and 11% of pts, respectively. In addition, 85% received ≥ 4 prior systemic regimens (neoadjuvant, adjuvant or metastatic), including anthracyclines (78%), taxanes (82%) and platinum agents (15% cisplatin, 41% carboplatin). All-grade treatment-related AEs occurred in 67% of pts, most frequently fatigue (22%), pyrexia (15%), neutropenia (15%) and nausea (15%). 11% of pts experienced a Grade 3-5 related AE (5 Grade 3 events: adrenal insufficiency, neutropenia, nausea, vomiting, decreased WBC count; 1 Grade 5 pulmonary hypertension event in a pt with an atrial septal defect). Among 21 efficacy-evaluable PD-L1 IHC 2 or 3 pts (13 IHC 2 and 8 IHC 3), the unconfirmed RECIST ORR was 24% (95% CI, 8% to 47%); 3 PRs and 2 CRs were observed. Response duration ranged from 0.1+ to 41.6+ wks, with the median not yet reached. Pts with evidence of durable nonclassical responses suggestive of pseudoprogression were also observed. Overall, the 24-wk PFS rate was 33% (95% CI, 12% to 53%). Biomarker analysis revealed transient elevation of plasma cytokines and proliferating CD8 cells following MPDL3280A treatment. Updated clinical data, including PD-L1-negative pts, will be presented.nnConclusions: MPDL3280A was generally well tolerated and demonstrated promising efficacy in pretreated metastatic PD-L1 IHC 2 or 3 TNBC pts. Furthermore, circulating biomarker analyses revealed pharmacodynamic responses to MPDL3280A. Clinical evaluation of MPDL3280A in metastatic PD-L1 IHC 0 or 1 TNBC is ongoing ([NCT01375842][1]).nnCitation Format: Leisha A. Emens, Fadi S. Braiteh, Philippe Cassier, Jean-Pierre Delord, Joseph Paul Eder, Marcella Fasso, Yuanyuan Xiao, Yan Wang, Luciana Molinero, Daniel S. Chen, Ian Krop. Inhibition of PD-L1 by MPDL3280A leads to clinical activity in patients with metastatic triple-negative breast cancer (TNBC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2859. doi:10.1158/1538-7445.AM2015-2859nn [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01375842&atom=%2Fcanres%2F75%2F15_Supplement%2F2859.atom

OX40 Costimulation Synergizes with GM-CSF Whole-Cell Vaccination to Overcome Established CD8+ T Cell Tolerance to an Endogenous Tumor Antigen

T cell costimulation via OX40 is known to increase CD4+ T cell expansion and effector function and enhances the development of T cell memory. OX40 costimulation can also prevent, and even reverse, CD4+ T cell anergy. However, the role of OX40 in CD8+ T cell function is less well defined, particularly in the setting of immune tolerance. To determine the effects of OX40 costimulation on the induction of the host CD8+ T cell repertoire to an endogenous tumor Ag, we examined the fate of CD8+ T cells specific for the immunodominant rat HER-2/neu epitope, RNEU420–429, in FVB MMTV-neu (neu-N) mice, which express rat HER-2/neu protein in a predominantly mammary-restricted fashion. We show that the RNEU420–429-specific T cell repertoire in neu-N mice expands transiently after vaccination with a neu-targeted GM-CSF-secreting whole-cell vaccine, but quickly declines to an undetectable level. However, OX40 costimulation, when combined with GM-CSF-secreting tumor-targeted vaccination, can break established CD8+ T cell tolerance in vivo by enhancing the expansion, and prolonging the survival and effector function of CD8+ T cells specific for RNEU420–429. Moreover, we demonstrate that OX40 expression is up-regulated on both CD4+ and CD8+ T cells shortly after administration of a GM-CSF expressing vaccine. These studies highlight the increased efficacy of OX40 costimulation when combined with a GM-CSF-secreting vaccine, and define a new role for OX40 costimulation of CD8+ T cells in overcoming tolerance and boosting antitumor immunity.

Antagonists of PD-1 and PD-L1 in Cancer Treatment

The PD-1 pathway, comprising the immune cell co-receptor Programmed Death 1 (PD-1) and its ligands, PD-L1 (B7-H1) and PD-L2 (B7-DC), mediates local immunosuppression in the tumor microenvironment. Drugs designed to block PD-1 or PD-L1 release the brakes on anti-tumor immunity and have demonstrated clinical activity in several types of advanced cancers, validating this pathway as a target for cancer therapy. Two such drugs have recently been approved to treat melanoma and lung cancers, and regulatory approvals in first- and second-line settings for additional cancer types are anticipated. The manageable safety profile of PD-1/PD-L1 blocking drugs identifies them as suitable for outpatient administration and the development of combinatorial therapies. Ongoing studies aim to identify biomarkers to guide patient selection, which would further improve the risk:benefit ratio for these drugs.

The Multikinase Inhibitor Sorafenib Reverses the Suppression of IL-12 and Enhancement of IL-10 by PGE2 in Murine Macrophages

Classical activating stimuli like LPS drive macrophages to secrete a battery of inflammatory cytokines, including interleukin (IL)-12/23, through Toll-like receptor (TLR) signaling. TLR activation in the presence of some factors, including prostaglandin E₂ (PGE₂), promotes an anti-inflammatory cytokine profile, with production of IL-10 and suppression of IL-12/23 secretion. Extracellular signal-regulated kinase (ERK) is a key regulator of macrophage IL-10 production. Since it inhibits ERK, we investigated the impact of Sorafenib on the cytokine profile of macrophages. In the presence of PGE₂, Sorafenib restored the secretion of IL-12 and suppressed IL-10 production. Moreover, IL-12 secretion was enhanced by Sorafenib under conditions of TLR ligation alone. Furthermore, the impact of tumor culture supernatants, cholera toxin, and cAMP analogs (which suppress IL-12 secretion), was reversed by Sorafenib. Sorafenib inhibited the activation of the MAP kinase p38 and its downstream target mitogen and stress activated protein kinase (MSK), and partially inhibited protein kinase B (AKT) and its subsequent inactivation of the downstream target glycogen synthase kinase 3-β (GSK3-β). Interference with these pathways, which are pivotal in determining the balance of inflammatory versus anti-inflammatory cytokines, provides a potential mechanism by which Sorafenib can modulate the macrophage cytokine phenotype. These data raise the possibility that the use of Sorafenib as cancer therapy could potentially reverse the immunosuppressive cytokine profile of tumor-associated macrophages, rendering the tumor microenvironment more conducive to an anti-tumor immune response.

A Feasibility Study of Cyclophosphamide, Trastuzumab, and an Allogeneic GM-CSF–Secreting Breast Tumor Vaccine for HER2+ Metastatic Breast Cancer

Chen and colleagues show in patients and in a mouse model of HER2+ breast cancer that abrogating immune suppression with low-dose cyclophosphamide along with administration of an allogeneic GM-CSF–secreting HER2+ tumor vaccine and trastuzumab weekly augmented HER2-specific T-cell responses and survival. Granulocyte-macrophage colony-stimulating factor (GM-CSF)–secreting tumor vaccines are bioactive, but limited by disease burden and immune tolerance. Cyclophosphamide augments vaccine activity in tolerant neu mice and in patients with metastatic breast cancer. HER2-specific monoclonal antibodies (mAb) enhance vaccine activity in neu mice. We hypothesized that cyclophosphamide-modulated vaccination with HER2-specific mAb safely induces relevant HER2-specific immunity in neu mice and patients with HER2+ metastatic breast cancer. Adding both cyclophosphamide and the HER2-specific mAb 7.16.4 to vaccination maximized HER2-specific CD8+ T-cell immunity and tumor-free survival in neu transgenic mice. We, therefore, conducted a single-arm feasibility study of cyclophosphamide, an allogeneic HER2+ GM-CSF–secreting breast tumor vaccine, and weekly trastuzumab in 20 patients with HER2+ metastatic breast cancer. Primary clinical trial objectives were safety and clinical benefit, in which clinical benefit represents complete response + partial response + stable disease. Secondary study objectives were to assess HER2-specific T-cell responses by delayed type hypersensitivity (DTH) and intracellular cytokine staining. Patients received three monthly vaccinations, with a boost 6 to 8 months from trial entry. This combination immunotherapy was safe, with clinical benefit rates at 6 months and 1 year of 55% [95% confidence interval (CI), 32%–77%; P = 0.013] and 40% (95% CI, 19%–64%), respectively. Median progression-free survival and overall survival durations were 7 months (95% CI, 4–16) and 42 months (95% CI, 22–70), respectively. Increased HER2-specific DTH developed in 7 of 20 patients [of whom 4 had clinical benefit (95% CI, 18–90)], with a trend toward longer progression-free survival and overall survival in DTH responders. Polyfunctional HER2-specific CD8+ T cells progressively expanded across vaccination cycles. Further investigation of cyclophosphamide-modulated vaccination with trastuzumab is warranted. (Clinicaltrials.gov identifier: NCT00399529) Cancer Immunol Res; 2(10); 949–61. ©2014 AACR.

A short-term biomarker modulation study of simvastatin in women at increased risk of a new breast cancer.

Observational studies have demonstrated a decreased incidence of cancers among users of HMG CoA reductase inhibitors (statins) and a reduced risk of recurrence among statin users diagnosed with early stage breast cancer. We initiated a prospective study to identify potential biomarkers of simvastatin chemopreventive activity that can be validated in future trials. The contralateral breast of women with a previous history of breast cancer was used as a high-risk model. Eligible women who had completed all planned treatment of a prior stage 0–III breast cancer received simvastatin 40xa0mg orally daily for 24–28xa0weeks. At baseline and end-of-study, we measured circulating concentrations of high-sensitivity C-reactive protein (hsCRP), estrogens, and fasting lipids; breast density on contralateral breast mammogram; and quality of life by Rand Short Form 36-Item health survey. Fifty women were enrolled with a median age of 53xa0years. Total cholesterol, LDL cholesterol, triglyceride, and hsCRP fell significantly during the study (P valuesxa0<xa00.001, <0.001, 0.003, and 0.05, respectively). Estrone sulfate concentrations decreased with simvastatin treatment (Pxa0=xa00.01 overall), particularly among post-menopausal participants (Pxa0=xa00.006). We did not observe a significant change in circulating estradiol or estrone concentrations, contralateral mammographic breast density, or reported physical functioning or pain scores. This study demonstrates the feasibility of short-term biomarker modulation studies using the contralateral breast of high-risk women. Simvastatin appears to modulate estrone sulfate concentrations and its potential chemopreventive activity in breast cancer warrants further investigation.

Toward integrative cancer immunotherapy: targeting the tumor microenvironment.

The development of cancer has historically been attributed to genomic alterations of normal host cells. Accordingly, the aim of most traditional cancer therapies has been to destroy the transformed cells themselves. There is now widespread appreciation that the progressive growth and metastatic spread of cancer cells requires the cooperation of normal host cells (endothelial cells, fibroblasts, other mesenchymal cells, and immune cells), both local to, and at sites distant from, the site at which malignant transformation occurs. It is the balance of these cellular interactions that both determines the natural history of the cancer, and influences its response to therapy. This active tumor-host dynamic has stimulated interest in the tumor microenvironment as a key target for both cancer diagnosis and therapy. Recent data has demonstrated both that the presence of CD8+ T cells within a tumor is associated with a good prognosis, and that the eradication of all malignantly transformed cells within a tumor requires that the intra-tumoral concentration of cytolytically active CD8+ effector T cells remain above a critical concentration until every tumor cell has been killed. These findings have stimulated two initiatives in the field of cancer immunotherapy that focus on the tumor microenvironment. The first is the development of the immune score as part of the routine diagnostic and prognostic evaluation of human cancers, and the second is the development of combinatorial immune-based therapies that reduce tumor-associated immune suppression to unleash pre-existing or therapeutically-induced tumor immunity. In support of these efforts, the Society for the Immunotherapy of Cancer (SITC) is sponsoring a workshop entitled Focus on the Target: The Tumor Microenvironment to be held October 24-25, 2012 in Bethesda, Maryland. This meeting should support development of the immune score, and result in a position paper highlighting opportunities for the development of integrative cancer immunotherapies that sculpt the tumor microenvironment to promote definitive tumor rejection.

Abstract 2986: Atezolizumab in metastatic TNBC (mTNBC): Long-term clinical outcomes and biomarker analyses

Introduction. Triple negative breast cancer (TNBC) has a poor prognosis and limited treatment options. Atezolizumab (atezo) is a humanized mAb that inhibits the binding of PD-L1 to PD-1 and B7.1, thus restoring tumor-specific T-cell immunity. Atezo was evaluated in an expansion cohort of mTNBC patients (pts) in a Phase Ia study (NCT01375842). Methods. Enrollment was initially limited to TNBC pts with PD-L1 on ≥5% of tumor-infiltrating immune cells (IC2/3), then opened to pts regardless of PD-L1 status. Pts received atezo IV in 1L or 2L+ q3w at 15 or 20 mg/kg or 1200 mg for 1 y with option to be retreated at PD, or until loss of clinical benefit. ORR was assessed by RECIST v1.1 and irRC, to capture non-conventional responses. Baseline PD-L1 expression on IC was centrally scored as IC0/1/2/3 (VENTANA SP142 assay). Pretreatment tumors and on-therapy biopsies were evaluated for TILs, CD8 T cells and macrophages by IHC. Results. As of Mar 31, 2016, 115 mTNBC pts were safety evaluable; atezo was generally well tolerated. There were no additional safety signals from prior report (Emens AACR 2015). 112 pts with FU ≥12 wk were evaluable for response. Based on irRC, ORR in 1L and 2L+ pts were 26% and 11%, respectively. ORR for PD-L1 IC2/3 pts were 17% vs 8% in IC0/1. mDoR was 21.1 mo (3 to 34+). mOS of responders (n=15) was not reached (4+ to 37+ mo) with no deaths as of data cutoff. mOS of non-responders who lived ≥ 6 wk (n=87) was 9 mo (1+ to 19+ mo). OS rates in all pts at 1, 2, and 3 y were 41%, 22% and 22%, respectively. OS rates at 1, 2, and 3 y for PD-L1 IC2/3 were 45%, 28% and 28%, respectively. Pts whose tumors had >10% TILs or ≥1.35% CD8 in the tumor center trended toward higher ORR and longer OS. Atezo increased intratumoral TILs, CD8, macrophages and IC PD-L1 expression, but no response association was observed. Conclusions. In mTNBC, atezo was well tolerated. Responders showed durable clinical benefit. Response rates were higher in 1L or PD-L1 IC2/3 pts. Baseline TILs and CD8 were associated with greater clinical benefit. Citation Format: Peter Schmid, Cristina Cruz, Fadi S. Braiteh, Joseph Paul Eder, Sara Tolaney, Irene Kuter, Rita Nanda, Cathie Chung, Philippe Cassier, Jean-Pierre Delord, Michael Gordon, Yijin Li, Bo Liu, Carol O’Hear, Marcella Fasso, Luciana Molinero, Leisha A. Emens. Atezolizumab in metastatic TNBC (mTNBC): Long-term clinical outcomes and biomarker analyses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2986. doi:10.1158/1538-7445.AM2017-2986

Breast cancer immunotherapy: Facts and hopes

Immunotherapy is revolutionizing the management of multiple solid tumors, and early data have revealed the clinical activity of programmed cell death-1/programmed death ligand-1 (PD-1/PD-L1) antagonists in small numbers of patients with metastatic breast cancer. Clinical activity appears more likely if the tumor is triple negative, PD-L1+, and/or harbors higher levels of tumor-infiltrating leukocytes. Responses to atezolizumab and pembrolizumab appear to be durable in metastatic triple-negative breast cancer (TNBC), suggesting that these agents may transform the lives of responding patients. Current clinical efforts are focused on developing immunotherapy combinations that convert nonresponders to responders, deepen those responses that do occur, and surmount acquired resistance to immunotherapy. Identifying biomarkers that can predict the potential for response to single-agent immunotherapy, identify the best immunotherapy combinations for a particular patient, and guide salvage immunotherapy in patients with progressive disease are high priorities for clinical development. Smart clinical trials testing rational immunotherapy combinations that include robust biomarker evaluations will accelerate clinical progress, moving us closer to effective immunotherapy for almost all patients with breast cancer. Clin Cancer Res; 24(3); 511–20. ©2017 AACR.