A Phase Ib Open-Label, Multicenter Study of Inhaled DV281, a TLR9 Agonist, in Combination with Nivolumab in Patients with Advanced or Metastatic Non-small Cell Lung Cancer

PURPOSE

Although PD-(L)1 inhibitors have shown efficacy in advanced/metastatic non-small cell lung cancer (NSCLC), many patients do not respond to this treatment and more effective combinations with acceptable toxicities are needed. To assess the potential benefit of combining localized innate immune stimulation with checkpoint blockade, the TLR9 agonist DV281 was combined with nivolumab in a phase Ib study.

PATIENTS AND METHODS

Patients after one or two prior lines of systemic therapy were enrolled in a dose-escalation study with a 3+3 design. DV281 was administered via inhalation in five dose cohorts at 1 to 25 mg; nivolumab 240 mg was administered intravenously every 2 weeks. Safety, tolerability, pharmacodynamics, and response to treatment were assessed.

RESULTS

Twenty-six patients with advanced NSCLC enrolled. Baseline programmed death ligand 1 (PD-L1) expression was present in 16 patients (61.5%); 21 (80.7%) had received previous anti-PD-1/PD-L1. Thirteen patients (50%) had stable disease, nine (34.6%) had progressive disease, and four (15.4%) were not evaluable. Median duration of disease control was 124 days. Adverse events were seen in 16 patients (61.5%), mostly grade 1/2 chills, fatigue, flu-like symptoms, diarrhea, and rash; there was only one grade 3 adverse event (dyspnea). Pharmacodynamic assessment, measured by IFN- inducible gene expression, showed target engagement in all dose cohorts. Systemic pharmacodynamic responses plateaued in the 2 highest dose cohorts.

CONCLUSIONS

DV281 with nivolumab was well tolerated with target engagement observed at every dose. Pharmacodynamic advantages at doses above 10 mg were unclear. The long duration of disease control in 50% of patients suggests clinically relevant activity in this population of heavily pretreated patients.

Low-dose metronomic cyclophosphamide complements the actions of an intratumoral C-class CpG TLR9 agonist to potentiate innate immunity and drive potent T cell-mediated anti-tumor responses

The synthetic oligonucleotide SD-101 is a potent and specific agonist for toll-like receptor 9. Intratumoral injection of SD-101 induces significant anti-tumor immunity in preclinical and clinical studies, especially when combined with PD-1 blockade. To build upon this strategy, we studied the enhancement of SD-101 activities by combination with low-dose cyclophosphamide, a well-characterized agent with potentially complementary activities. In multiple mouse tumor models, we demonstrate substantial anti-tumor activity of the combination, compared to each single agent. Combination therapy generated CD8+ T cell dependent immunity leading to rejection of both non-injected and injected tumors and long-term survival, even in very large tumors. Mechanistic studies encompassing global gene expression changes and characterization of immune cell infiltrates show the rapid, sequential induction of innate and adaptive responses and identify discrete contributions of SD-101 and cyclophosphamide. Importantly, these changes were prominent in tumors not injected directly with SD-101. Combination treatment resulted in creation of a permissive environment for a systemic anti-tumor immune response, including a reduction of intratumoral regulatory T cells (Tregs) and an increase in "M1" versus "M2" tumor-associated macrophage (TAM) phenotypes. Additionally, we observed increased immunogenic cell death as well as antigen processing in response to combination treatment.

Discovery and Optimization of HKT288, a Cadherin-6-Targeting ADC for the Treatment of Ovarian and Renal Cancers

Despite an improving therapeutic landscape, significant challenges remain in treating the majority of patients with advanced ovarian or renal cancer. We identified the cell-cell adhesion molecule cadherin-6 (CDH6) as a lineage gene having significant differential expression in ovarian and kidney cancers. HKT288 is an optimized CDH6-targeting DM4-based antibody-drug conjugate (ADC) developed for the treatment of these diseases. Our study provides mechanistic evidence supporting the importance of linker choice for optimal antitumor activity and highlights CDH6 as an antigen for biotherapeutic development. To more robustly predict patient benefit of targeting CDH6, we incorporate a population-based patient-derived xenograft (PDX) clinical trial (PCT) to capture the heterogeneity of response across an unselected cohort of 30 models-a novel preclinical approach in ADC development. HKT288 induces durable tumor regressions of ovarian and renal cancer models in vivo, including 40% of models on the PCT, and features a preclinical safety profile supportive of progression toward clinical evaluation.Significance: We identify CDH6 as a target for biotherapeutics development and demonstrate how an integrated pharmacology strategy that incorporates mechanistic pharmacodynamics and toxicology studies provides a rich dataset for optimizing the therapeutic format. We highlight how a population-based PDX clinical trial and retrospective biomarker analysis can provide correlates of activity and response to guide initial patient selection for first-in-human trials of HKT288. Cancer Discov; 7(9); 1030-45. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 920.

Anterior gradient-2 plays a critical role in breast cancer cell growth and survival by modulating cyclin D1, estrogen receptor-alpha and survivin

Introduction

Anterior-gradient 2 (AGR2) is an estrogen-responsive secreted protein. Its upregulation has been well documented in a number of cancers, particularly breast cancer, for which mixed data exist on the prognostic implications of AGR2 expression. Although emerging evidence indicates that AGR2 is associated with poor prognosis, its function and impact on cancer-relevant pathways have not been elucidated in breast cancer.

Methods

To investigate the biologic role of AGR2 in breast cancer, AGR2 was transiently knocked down, by using siRNA, in T47 D and ZR-75-1 (estrogen receptor-α (ER)-positive) and MDA-MB-231 and SK-BR-3 (ER-negative) human breast cancer cell lines. The impact of silencing AGR2 was evaluated in both anchorage-dependent and anchorage-independent growth (soft agar, spheroid) assays. Cell-cycle profiles in ER-positive cell lines were determined with BrdU incorporation, and cell death was measured with Annexin V, JC-1, and F7-26 staining. After transiently silencing AGR2 or stimulating with recombinant AGR2, modulation of key regulators of growth and survival pathways was assessed with Western blot. Combination studies of AGR2 knockdown with the antiestrogens tamoxifen and fulvestrant were carried out and assessed at the level of anchorage-dependent growth inhibition and target modulation (cyclin D1, ER).

Results

AGR2 knockdown inhibited growth in anchorage-dependent and anchorage-independent assays, with a more-pronounced effect in ER-positive cell lines. Cyclin D1 levels and BrdU incorporation were reduced with AGR2 knockdown. Conversely, cyclin D1 was induced with recombinant AGR2. AGR2 knockdown induced cell death in ZR-75-1 and T47 D cells, and also downregulated survivin and c-Myc. Evidence of AGR2-ER crosstalk was demonstrated by a reduction of ER at the protein level after transiently silencing AGR2. AGR2 knockdown in combination with fulvestrant or tamoxifen did not preclude the efficacy of the antiestrogens, but enhanced it. In addition, p-Src, implicated in tamoxifen resistance, was downregulated with AGR2 knockdown.

Conclusions

Transiently silencing AGR2 in ER-positive breast cancer cell lines inhibited cell growth and cell-cycle progression and induced cell death. Breast cancer drivers (ER and cyclin D1) as well as cancer-signaling nodes (pSrc, c-Myc, and survivin) were demonstrated to be downstream of AGR2. Collectively, the data presented support the utility of anti-AGR2 therapy in ER-positive breast cancers because of its impact on cancer-relevant pathways.

Microarray analysis of primary endothelial cells challenged with different inflammatory and immune cytokines

To investigate the potential molecular mediators of tissue-specific recruitment, we explored the influence of different cytokine challenges on gene expression regulation in five primary endothelial cells (ECs), representing two different phenotypes: iliac artery and aortic (macrovascular); lung, colon and dermal (microvascular). We challenged ECs with cytokines that elicit different patterns of inflammatory and immune responses in immune cells: tumor necrosis factor (TNF-alpha), interferon-gamma (IFN-gamma) or interleukin-4 (IL-4), and used microarrays containing approximately 40,000 unique cDNAs, to assess changes in differential gene expression relative to untreated cells. Five hundred and sixty three sequences changed by at least 2.5 fold in one or more of the 15 possible EC /cytokine combinations. The list included highly regulated adhesion molecules, chemokines, cytokines, metalloproteases, and IFN-gamma-induced genes. Overall, IFN-gamma caused the largest number of gene expression changes and its profile was least correlated with IL-4. In addition to clusters that were predominantly EC/cytokine specific, we also observed several clusters that were regulated by more than one cytokine across several ECs. Furthermore, we identified genes that were reciprocally expressed in response to different cytokines that could serve as markers of inflammatory and immune expression. These results confirm the importance of microenvironment in primary ECs that could have important applications in developing targeted therapies for vascular diseases.

Tumor necrosis factor-dependent segmental control of MIG expression by high endothelial venules in inflamed lymph nodes regulates monocyte recruitment

Monocytes recruited from the blood are key contributors to the nature of an immune response. While monocyte recruitment in a subset of immunopathologies has been well studied and largely attributed to the chemokine monocyte chemoattractant protein (MCP)-1, mechanisms mediating such recruitment to other sites of inflammation remain elusive. Here, we showed that localized inflammation resulted in an increased binding of monocytes to perifollicular high endothelial venules (HEVs) of lymph nodes draining a local inflammatory site. Quantitative PCR analyses revealed the upregulation of many chemokines in the inflamed lymph node, including MCP-1 and MIG. HEVs did not express detectable levels of MCP-1; however, a subset of HEVs in inflamed lymph nodes in wild-type (but not tumor necrosis factor [TNF] null mice) expressed MIG and this subset of HEVs preferentially supported monocyte binding. Expression of CXCR3, the receptor for MIG, was detected on a small subset of peripheral blood monocytes and on a significant percentage of recruited monocytes. Most importantly, in both ex vivo and in vivo assays, neutralizing anti-MIG antibodies blocked monocyte binding to inflamed lymph node HEVs. Together, these results suggest that the lymph node microenvironment can dictate the nature of molecules expressed on HEV subsets in a TNF-dependent fashion and that inflammation-induced MIG expression by HEVs can mediate monocyte recruitment.

Membrane-bound TNF supports secondary lymphoid organ structure but is subservient to secreted TNF in driving autoimmune inflammation

Mice without secreted TNF but with functional, normally regulated and expressed membrane-bound TNF (memTNF(Delta/Delta) mice) were created by knocking-in the uncleavable Delta 1-9,K11E TNF allele. In contrast to TNF-deficient mice (TNF(-/-)), memTNF supported many features of lymphoid organ structure, except generation of primary B cell follicles. Splenic chemokine expression was near normal. MemTNF-induced apoptosis was mediated through both TNF-R1 and TNF-R2. That memTNF is suboptimal for development of inflammation was revealed in experimental autoimmune encephalomyelitis. Disease severity was reduced in memTNF(Delta/Delta) mice relative to wild-type mice, and the nature of spinal cord infiltrates resembled that in TNF(-/-) mice. We conclude that memTNF supports many processes underlying lymphoid tissue structure, but secreted TNF is needed for optimal inflammatory lesion development.

Id-2 regulates critical aspects of human cytotrophoblast differentiation, invasion and migration

During early human placental development, the conceptus attaches itself to the uterus through cytotrophoblast invasion. Invasive cytotrophoblast cells differentiate from precursor villous cytotrophoblasts, but the essential regulating factors in this process are unknown. Basic helix-loop-helix (bHLH) transcription factor dimers are essential regulators of mouse trophoblast development. We therefore examined the importance of this family of factors in the human placenta. In many cell lineages, bHLH factors are sequestered by members of the Id family, HLH proteins that lack the basic DNA binding domain (Inhibitor of DNA binding proteins (Id-1 to Id-4)). During differentiation of some tissues, Id expression declines, allowing bHLH factors to dimerize, bind DNA and trans-activate lineage-specific genes. To begin to study the role of bHLH transcription factors in human placental development, we first characterized Id expression in cytotrophoblast cells. The cells expressed Id-3 constitutively; Id-2 was downregulated, at the mRNA and protein levels, as the cells differentiated in culture and in situ, respectively. In cases when cytotrophoblast differentiation was compromised (in placentas from women with preeclampsia, or in cells grown under hypoxic conditions in culture), Id-2 expression was maintained. To assess the functional relevance of these correlations, we used an adenovirus vector to maintain Id-2 protein expression in cultured cytotrophoblasts. Compared to control (lacZ-expressing) cells, cytotrophoblasts transduced to constitutively express Id-2 retained characteristics of undifferentiated cells: (alpha)1 integrin expression was low and cyclin B expression was retained. Furthermore, invasion through Matrigel was partially inhibited and migration was strikingly enhanced in Id-2-expressing cells. These results suggest that Id-2 and the bHLH factors that it partners play important roles in human cytotrophoblast development.

A repertoire of differentially expressed transcription factors that offers insight into mechanisms of human cytotrophoblast differentiation

During human placental development, specialized cells allocated to the extraembryonic lineage (cytotrophoblasts) invade the uterus, anchoring the conceptus to the decidua and tapping a supply of maternal blood. This unusual behavior requires cytotrophoblasts to assume highly specialized characteristics; some are commonly associated with tumor cells, while others are typical of endothelia. Here we investigated the transcriptional mechanisms that control cytotrophoblast differentiation/invasion. Specifically, we examined the cells' expression of a number of transcription factors, at the RNA level, as they differentiated along the invasive pathway in vitro. Since basic helix-loop-helix (bHLH) proteins play important roles in murine trophoblast differentiation, we first examined their expression by cytotrophoblasts. As in murine placental development, expression of the human homologue of Mash-2 was confined to progenitor cells. But expression of Hand-1, which promotes differentiation of murine trophoblast giant cells, was not detected. We also found that cytotrophoblasts upregulated the expression of bHLH/PAS factors that function in adaptive responses to hypoxia, including hEPAS-1, which is expressed primarily in endothelial cells. Quite unexpectedly, we discovered that cytotrophoblasts express high levels of mRNA encoding the human homologue of the Drosophila neuronal fate gene, glial cells missing-1 (gcm-1). We also found evidence of crosstalk between the bHLH and GCM-1 regulatory networks. Together, these results offer insights into the transcriptional mechanisms that govern cytotrophoblast differentiation/invasion. Interestingly, these mechanisms suggest analogies with those that govern differentiation of murine stem cells allocated to both the intra- and extraembryonic lineages.

Human placental HLA-G expression is restricted to differentiated cytotrophoblasts

Human placental trophoblasts lie at the maternal-fetal interface, a position in which they could play an important role in maternal tolerance of the fetal semi-allograft. Central to this hypothesis is their unusual MHC class I expression: they suppress class Ia production while expressing HLA-G, a class Ib molecule. We investigated human trophoblast HLA-G protein production in vivo and in vitro. We first used a synthetic peptide corresponding to the variable sequence of the alpha 1 domain to produce mAbs that recognized HLA-G. Ab specificity was demonstrated by immunoaffinity purification of a single protein with the same molecular mass (38 kDa) as HLA-G from choriocarcinoma cells. Use of these Abs to stain tissue sections of the maternal-fetal interface containing cytotrophoblasts in all stages of differentiation showed that HLA-G is expressed only by cytotrophoblasts that invade the uterus. Our previous in vitro studies showed that when early-gestation cytotrophoblast stem cells are cultured, they differentiate rapidly along the invasive pathway, as demonstrated by their expression of stage-specific markers. Here we show they also up-regulate HLA-G production. Cytotrophoblasts from term placentas, which have reduced invasive capacity in vitro, also had decreased ability to up-regulate HLA-G protein expression. We detected high levels of HLA-G mRNA in cytotrophoblasts isolated from first- and second-trimester placentas, but only trace amounts in term cells. Taken together, these results suggest that HLA-G production is a critical component of cytotrophoblast differentiation along the invasive pathway.

Human placental HLA-G expression is restricted to differentiated cytotrophoblasts

Human placental trophoblasts lie at the maternal-fetal interface, a position in which they could play an important role in maternal tolerance of the fetal semi-allograft. Central to this hypothesis is their unusual MHC class I expression: they suppress class Ia production while expressing HLA-G, a class Ib molecule. We investigated human trophoblast HLA-G protein production in vivo and in vitro. We first used a synthetic peptide corresponding to the variable sequence of the alpha 1 domain to produce mAbs that recognized HLA-G. Ab specificity was demonstrated by immunoaffinity purification of a single protein with the same molecular mass (38 kDa) as HLA-G from choriocarcinoma cells. Use of these Abs to stain tissue sections of the maternal-fetal interface containing cytotrophoblasts in all stages of differentiation showed that HLA-G is expressed only by cytotrophoblasts that invade the uterus. Our previous in vitro studies showed that when early-gestation cytotrophoblast stem cells are cultured, they differentiate rapidly along the invasive pathway, as demonstrated by their expression of stage-specific markers. Here we show they also up-regulate HLA-G production. Cytotrophoblasts from term placentas, which have reduced invasive capacity in vitro, also had decreased ability to up-regulate HLA-G protein expression. We detected high levels of HLA-G mRNA in cytotrophoblasts isolated from first- and second-trimester placentas, but only trace amounts in term cells. Taken together, these results suggest that HLA-G production is a critical component of cytotrophoblast differentiation along the invasive pathway.