Abstract OT2-06-02: Chemokine modulation to enhance the effectiveness of pembrolizumab in patients with metastatic triple negative breast cancer

Background: Triple negative breast cancer (TNBC) is found in approximately 15-20% of all breast cancer, and is associated with poor prognosis, early relapse and a significantly shorter survival following recurrence. Early phase trials with immune checkpoint inhibitors have shown modest yet durable clinical responses with a tolerable safety profile. Strategies to sensitize these tumors to checkpoint inhibition will result in decreased morbidity and mortality.

Tumor infiltrating immune cells and intratumoral expression of PD-1/PD-L1/PD-L2 can predict patients' benefit from Pembrolizumab. Pre-clinical ex-vivo data show that chemokine modulating regimen consisting of Rintatolimod, IFNα and COX2 blocker (CKM), selectively attracts cytotoxic T cells into tumors, and increases intratumoral expression of PD-1/PD-L1/PD-L2, without enhancing soluble suppressive mechanisms. Furthermore, mouse data has shown safety of CKM and PD-1 blockade combination and efficacy in inducing long-term survival of mice with resistant tumors.

Clinical trials of CKM in Colon and ovarian cancer (NCT01545141, NCT02432378) demonstrated safety of Rintatolimod given with IFNα/COX2, and preliminary data show local efficacy in tumor microenvironment modulation.

Design: This is an open-label, single center, phase IIa study to test Chemokine modulating regimen (CKM) pre-treatment followed by Pembrolizumab in patients with metastatic TNBC, regardless of PD-1 expression, who progressed on ≥1 lines of therapy.

Patients are given pre-treatment CKM, which consists of Rintatolimod (200 mg IV), IFNα-2 (20 million units/m2 IV) and Celecoxib (200 mg po BID), on 3 consecutive days for a total of 2 cycles, one week apart. The patient is then treated with Pembrolizumab 200 mg IV every 3 weeks until disease progression, intolerable side effects or withdrawal from study for up to 24 months. Study includes pre- and post CKM treatment biopsies.

Eligibility: Major criteria include age ≥ 18 years, ECOG ≤ 1, histologically proven metastatic TNBC, normal organ and marrow function, no active autoimmune disease or history of transplant, no prior anti-PD1/PDL1 therapy.

Aims: Primary objective is to evaluate the overall response rate to the combination therapy per irRECIST criteria. Secondary objectives include safety profile of the combination therapy, determining progression free survival, overall survival and disease control rate. Other immune exploratory objectives will include baseline and CKM-induced predictive biomarkers of clinical activity of the combination treatment.

Statistical Methods: The study includes a safety lead-in of 6 patients and utilizes a Simon two-stage minimax design. 18 patients are enrolled into stage 1 of the study. If < 4 responses are observed, the treatment combination will not be considered promising and enrollment will be terminated. However, if ≥ 4 responses are observed, then an additional 19 patients will be enrolled into stage 2, for a total number of 37 patients. In stage 2, if ≥ 9 responses are observed, then the treatment combination will be considered promising for future study.

Citation Format: Abdou Y, Williams LE, Kalinski P, Opyrchal M. Chemokine modulation to enhance the effectiveness of pembrolizumab in patients with metastatic triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT2-06-02.

P2RX7 purinoceptor: a therapeutic target for ameliorating the symptoms of duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is the most common inherited muscle disease, leading to severe disability and death in young men. Death is caused by the progressive degeneration of striated muscles aggravated by sterile inflammation. The pleiotropic effects of the mutant gene also include cognitive and behavioral impairments and low bone density. Current interventions in DMD are palliative only as no treatment improves the long-term outcome. Therefore, approaches with a translational potential should be investigated, and key abnormalities downstream from the absence of the DMD product, dystrophin, appear to be strong therapeutic targets. We and others have demonstrated that DMD mutations alter ATP signaling and have identified P2RX7 purinoceptor up-regulation as being responsible for the death of muscles in the mdx mouse model of DMD and human DMD lymphoblasts. Moreover, the ATP-P2RX7 axis, being a crucial activator of innate immune responses, can contribute to DMD pathology by stimulating chronic inflammation. We investigated whether ablation of P2RX7 attenuates the DMD model mouse phenotype to assess receptor suitability as a therapeutic target.

METHODS AND FINDINGS

Using a combination of molecular, histological, and biochemical methods and behavioral analyses in vivo we demonstrate, to our knowledge for the first time, that genetic ablation of P2RX7 in the DMD model mouse produces a widespread functional attenuation of both muscle and non-muscle symptoms. In dystrophic muscles at 4 wk there was an evident recovery in key functional and molecular parameters such as improved muscle structure (minimum Feret diameter, p < 0.001), increased muscle strength in vitro (p < 0.001) and in vivo (p = 0.012), and pro-fibrotic molecular signatures. Serum creatine kinase (CK) levels were lower (p = 0.025), and reduced cognitive impairment (p = 0.006) and bone structure alterations (p < 0.001) were also apparent. Reduction of inflammation and fibrosis persisted at 20 mo in leg (p = 0.038), diaphragm (p = 0.042), and heart muscles (p < 0.001). We show that the amelioration of symptoms was proportional to the extent of receptor depletion and that improvements were observed following administration of two P2RX7 antagonists (CK, p = 0.030 and p = 0.050) without any detectable side effects. However, approaches successful in animal models still need to be proved effective in clinical practice.

CONCLUSIONS

These results are, to our knowledge, the first to establish that a single treatment can improve muscle function both short and long term and also correct cognitive impairment and bone loss in DMD model mice. The wide-ranging improvements reflect the convergence of P2RX7 ablation on multiple disease mechanisms affecting skeletal and cardiac muscles, inflammatory cells, brain, and bone. Given the impact of P2RX7 blockade in the DMD mouse model, this receptor is an attractive target for translational research: existing drugs with established safety records could potentially be repurposed for treatment of this lethal disease.

Immunobiology of human mucin 1 in a preclinical ovarian tumor model

Epithelial ovarian cancer is an aggressive malignancy, with a low 5-year median survival. Continued improvement on the development of more effective therapies depends in part on the availability of adequate preclinical models for in vivo testing of treatment efficacy. Mucin 1 (MUC1) glycoprotein is a tumor-associated antigen overexpressed in ovarian cancer cells, making it a potential target for immune therapy. To create a preclinical mouse model for MUC1-positive ovarian tumors, we generated triple transgenic (Tg) mice that heterozygously express human MUC1(+/-) as a transgene, and carry the conditional K-rasG12D oncoallele (loxP-Stop-loxP-K-ras(G12D/+)) and the floxed Pten gene (Pten/(loxP/loxP)). Injection of Cre recombinase-encoding adenovirus (AdCre) in the ovarian bursa of triple (MUC1KrasPten) Tg mice triggers ovarian tumors that, in analogy to human ovarian cancer, express strongly elevated MUC1 levels. The tumors metastasize loco-regionally and are accompanied by high serum MUC1, closely mimicking the human disease. Compared with the KrasPten mice with tumors, the MUC1KrasPten mice show increased loco-regional metastasis and augmented accumulation of CD4+Foxp3+ immune-suppressive regulatory T cells. Vaccination of MUC1KrasPten mice with type 1 polarized dendritic cells (DC1) loaded with a MUC1 peptide (DC1-MUC1) can circumvent tumor-mediated immune suppression in the host, activate multiple immune effector genes and effectively prolong survival. Our studies report the first human MUC1-expressing, orthotopic ovarian tumor model, reveal novel MUC1 functions in ovarian cancer biology and demonstrate its suitability as a target for immune-based therapies.

Analysis of the CD4+ T cell responses to house dust mite allergoid

BACKGROUND

Modified allergen extracts (allergoids) with reduced IgE-binding capacity are successfully used in immunotherapy of atopic allergy. Their reduced T-cell stimulatory capacity is less well studied and is a subject of the present study.

METHODS

We compared the ability of native house dust mite extract (Dermatophagoides pteronyssinus; HDM) and the glutaraldehyde-modified allergoid (HDM-GA) to induce the proliferation and cytokine production by fresh PBMC and by DC-stimulated polyclonal Th cells and HDM-specific Th cell clones.

RESULTS

Freshly isolated T cells showed a partially reduced responsiveness to HDM-GA, differentially pronounced in different donors. HDM-specific Th cell clones prepared from three donors showed either a complete loss of reactivity to HDM-GA, or completely preserved responsiveness. The frequency of nonreactive clones was donor-dependent (2/3, 3/10 and 1/10). GA modification of HDM did not interfere with the cytokine production profile of HDM-specific T cell clones.

CONCLUSIONS

The reduced stimulatory potential of HDM-GA results mainly from a loss of certain Th cell epitopes, rather than impaired allergen uptake and presentation, or induction of suppressive factors. Varying frequencies of allergoid-nonreactive HDM-specific Th cells may result in differential responses of individual patients to immunotherapy.

Ceramide mediates tumor-induced dendritic cell apoptosis

Induction of apoptosis in dendritic cells (DC) is one of the escape mechanisms of tumor cells from the immune surveillance system. This study aimed to clarify the underlying mechanisms of tumor-induced DC apoptosis. The supernatants (SN) of murine tumor cell lines B16 (melanoma), MCA207, and MCA102 (fibrosarcoma) increased C16 and C24 ceramide as determined by electrospray mass spectrometry and induced apoptosis in bone marrow-derived DC. N-oleoylethanolamine or D-L-threo 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), which inhibits acid ceramidase or glucosylceramide synthase and then increases endogenous ceramide, enhanced DC apoptosis and ceramide levels in the presence of tumor SN. Pretreatment with L-cycloserine, an inhibitor of de novo ceramide synthesis, or phorbol ester, 12-O-tetradecanoylphorbol-13-acetate reduced endogenous ceramide levels and protected DC from tumor-induced apoptosis. However, other DC survival factors, including LPS and TNF-alpha, failed to do so. The protective activity of 12-O-tetradecanoylphorbol-13-acetate is abrogated by pretreatment with phosphoinositide 3-kinase (PI3K) inhibitor, LY294002. Therefore, down-regulation of PI3K is the major facet of tumor-induced DC apoptosis. Tumor SN, N-oleoylethanolamine, or PDMP suppressed Akt, NF-kappaB, and bcl-x(L) in DC, suggesting that the accumulation of ceramide impedes PI3K-mediated survival signals. Taken together, ceramide mediates tumor-induced DC apoptosis by down-regulation of the PI3K pathway.

How to deal with polarized Th2 cells: exploring the Achilles' heel

The central effector cells in the pathogenesis of atopic allergic diseases are type 2 T helper (Th2) cells, which display an aberrant cytokine profile dominated by type 2 cytokines. Initial reports from mouse studies indicated that established and committed Th2 cells are stable and unsusceptible to modulation. However, there is a growing awareness that in humans, established effector Th2 cells are more flexible and can be reverted to predominant Th1 phenotypes. In fact, the Th1-driving cytokine interleukin (IL)-12 is the crucial factor in this respect. IL-12 is mainly produced by dendritic cells (DC), which can be primed for high or low IL-12 production, depending on inflammatory and/or microbial signals they encounter during their residence in the peripheral tissues. Accordingly, both the regulation of and the priming for IL-12 production in DC form ideal targets for therapeutic intervention. The development of new therapies for atopic allergy now focuses on local IL-12-promoting substances to target both the development of new Th2 cells and the persistent population of established allergen-specific Th2 cells.

Corticosteroids inhibit the production of inflammatory mediators in immature monocyte-derived DC and induce the development of tolerogenic DC3

Corticosteroids (CS) are potent immunosuppressive agents that are known to affect T cell-mediated inflammation by the inhibition of proliferation and cytokine production, as well as the immunostimulatory function of monocytes and macrophages. Not much is known of the effect of corticosteroids on dendritic cells (DC), the professional T cell stimulatory antigen-presenting cells. We report that the endogenous CS hydrocortisone and the synthetic CS clobetasol-17-propionate strongly inhibited the production of the inflammatory mediators interleukin (IL)-12 p70, tumor necrosis factor alpha (TNF-alpha), and IL-6 by lipopolysaccharide (LPS)-stimulated monocyte-derived immature DC (iDC) in vitro. In contrast, the stimulatory capacity, antigen uptake, and the expression of costimulatory molecules were not affected. In accordance with the decreased production of IL-12 p70, CS-treated iDC induced less production of the inflammatory Th1 cytokine interferon-y and enhanced levels of the Th2 cytokines IL-10 and IL-5 in staphylococcal enterotoxin B-stimulated CD4+ Th cells. Furthermore, CS inhibited the maturation of iDC as assessed by the lack of expression of CD83 as well as by the prevention of the loss of antigen uptake capacities. These type 3 DC (DC3) matured in the presence of CS produce less IL-12 p70 and have a decreased T cell stimulatory capacity. Moreover, uncommitted T cells that encounter the CS-induced DC3 develop into Th2-biased cells, which may additionally decrease the Th1-mediated tissue damage but, on the other hand, Th2 cytokines may promote undesirable elevation of IgE and eosinophilia. These findings indicate that suppression of T cell-mediated inflammation by CS not only relies on direct effects on T cells, but also on various effects on DC, their professional antigen-presenting cells.

Inhibition of contact sensitizer-induced migration of human Langerhans cells by matrix metalloproteinase inhibitors

Emigration of Langerhans cells (LC) from the epidermis upon exposure to contact sensitizers is regarded as an essential event in the development of contact sensitization. Since migration of several types of cells depends on the activity of matrix metalloproteinases (MMPs), in the present study we tested whether MMP inhibitors (BB94, BB2116 and CT1166) can prevent the emigration of LC in cultured skin explants, which were exposed to a contact sensitizer (NiSO4). Epicutaneous application of NiSO4 significantly reduced the number of LC within the epidermis and the remaining LC were localized along the epidermal-dermal junction indicating the emigration of LC. In the presence of each of the MMP inhibitors tested, NiSO4-induced migration of LC was strongly decreased. Since after the epicutaneous application of contact sensitizer, its presentation by skin LC is essential for the development of contact sensitization instead of the development of antigen-specific tolerance, our results suggest that the use of MMP inhibitors may be beneficial for the prevention of contact sensitization of the host.

The paradigm of type 1 and type 2 antigen-presenting cells. Implications for atopic allergy

Optimal clearance of the various pathogen types encountered by the human body requires the selective activation of particular cellular and/or humoral immune responses. The orchestration of the types of effector responses is directed by Th cells through the production of type 1 (Th1 cell-associated) and type 2 (Th2 cell-associated) cytokines. The way in which the Th cell cytokine profile is matched to the type of invading pathogen, and why these profiles sometimes derail and lead to disease, is not well understood. Here, we will discuss the concept that antigen-presenting cells (APC) provide Th cells not only with antigen and costimulatory signals, but also with a polarizing signal (signal 3). This signal can be mediated by many APC-derived factors, but IL-12 and PGE2 seem to be of major importance. The Th2-biased responses in atopic allergy appeared to be associated with monocytes with a decreased IL-12/PGE2 ratio and, consequently, with the down-regulation of type 1 cytokine production in Th cells. As for Th cells, APC can be functionialy polarized. In vitro experiments with monocyte-derived dendritic cells (DC) showed that the presence of IFN-gamma during activation of immature DC primes for mature DC with the ability of high IL-12 production and, consequently, a Th1-driving capacity (APC1 or DC1). In contrast, PGE2 primes for a low IL-12 production ability and a Th2-driving capacity (APC2 or DC2). These findings suggest that pathogens provoke either Th1- or Th2-cell development by inducing the production of a certain pattern of inflammatory DC-polarizing mediators (e.g. IFN-gamma and PGE2) at the site of infection. The type of immune polarization will not only depend on the type of pathogen, but also varies with the type of infected tissue, i.e. that different tissues produce different mediators in response to the same pathogen. In the case of atopic allergy, this concept implies that the Th2-cell bias may be related to low levels of cross-regulatory infections, to Th1 cell-inducing pathogens, or to an aberrant function of stromal cells in peripheral tissues.

The role of antigen-presenting cells in the regulation of allergen-specific T cell responses

Allergic reactions in atopic patients follow from a generalized enhanced polarization of Th cells, predominantly imposed by factors derived from antigen-presenting cells from a pathogen-stressed tissue; these sample information not only on antigen structures but also on the nature of the stress. Antigen-presenting cells of atopic individuals show aberrant characteristics which, through a highly interactive communication network, play an active role in aberrant Th-cell polarization. This generalized bias may follow from intrinsic abnormalities of antigen-presenting cells and also from a low degree of cross-regulation by micro-organisms.

High-level IL-12 production by human dendritic cells requires two signals

IL-12 is a key cytokine in the development of Th1 responses. IL-12 production by antigen-presenting cells (APC) can be induced by the interaction between CD40 on the APC and CD40 ligand (CD40L) expressed on T cells after activation. Our previous study indicated that in dendritic cells (DC), the only APC that can activate naive T(h) cells efficiently, the mere CD40 engagement is insufficient to induce IL-12 production. The aim of the present study was to dissect the conditions for efficient IL-12 production by DC further. Using populations of naive and memory Th cells, recombinant CD40L, neutralizing and blocking antibodies, and by determining IFN-gamma production and CD40L expression levels, we here show that T cell-induced IL-12 production by DC results from the action of two signals, mediated by CD40L and IFN-gamma, and that the inability of naive T(h) cells to induce IL-12 production resides in their inability to produce IFN-(gamma). Other factors than CD40L and IFN-gamma can provide the required signals for IL-12 production by DC, as either factor could be replaced by lipopolysaccharide (LPS). The two-signal requirement proved unique for the production of IL-12, since either CD40 engagement or LPS was sufficient for the efficient production of tumor necrosis factor-alpha, IL-8 and the p40 subunit of IL-12, and may be considered as a safety mechanism for optimal control of potentially harmful T(h)1 responses.

Human dendritic cells require exogenous interleukin-12-inducing factors to direct the development of naive T-helper cells toward the Th1 phenotype

Dendritic cells (DC) are important initiators of specific primary immune responses because they are the only APC that can efficiently activate naive Th cells. DC have the capacity to produce interleukin-12 (IL-12), a cytokine that plays a pivotal role in the development of Th1-mediated cellular immune responses. The present study focuses on the conditions under which human DC produce bioactive IL-12 p70 and, consequently, direct the development of naive T helper (Th) cells toward the Th1 phenotype. Bacteria or bacterial compounds such as Staphylococcus aureus Cowan strain I (SAC) or lipopolysaccharide (LPS) induced substantial IL-12 levels in DC, which could be further upregulated by interferon-gamma (IFN-gamma), whereas induction of IL-12 production via CD40 ligation required IFN-gamma as an obligatory, complementary signal. Also, activated naive Th cells were poor inducers of IL-12 production, unless exogenous IFN-gamma was present, whereas activated memory Th cells were effective inducers of IL-12 production and did not require exogenous IFN-gamma. Next, the cytokine profiles of matured Th cells that were primed by DC under different conditions were examined. DC promoted the development of naive Th cells into memory Th0 cells that produced both the type 1 cytokine IFN-gamma and the type 2 cytokine IL-4. In contrast, after activation with SAC, DC efficiently directed the development of Th1 cells through the release of IL-12. An APC-independent Th cell maturation model, using either recombinant IL-12 or supernatants of SAC-activated DC and neutralizing anti-IL-12 antibodies, confirmed that DC-derived IL-12 was the major Th1 skewing factor. Together, these data indicate that the contact between DC and naive Th cells during the initiation of specific immune responses does not result in the efficient induction of IL-12 production and that, consequently, exogenous IL-12-inducing factors are required to promote primary Th1-mediated cellular immune responses.