Bone marrow microenvironments that contribute to patient outcomes in newly diagnosed multiple myeloma: A cohort study of patients in the Total Therapy clinical trials.

BACKGROUND: The tumor microenvironment (TME) is increasingly appreciated as an important determinant of cancer outcome, including in multiple myeloma (MM). However, most myeloma microenvironment studies have been based on bone marrow (BM) aspirates, which often do not fully reflect the cellular content of BM tissue itself. To address this limitation in myeloma research, we systematically characterized the whole bone marrow (WBM) microenvironment during premalignant, baseline, on treatment, and post-treatment phases. METHODS AND FINDINGS: Between 2004 and 2019, 998 BM samples were taken from 436 patients with newly diagnosed MM (NDMM) at the University of Arkansas for Medical Sciences in Little Rock, Arkansas, United States of America. These patients were 61% male and 39% female, 89% White, 8% Black, and 3% other/refused, with a mean age of 58 years. Using WBM and matched cluster of differentiation (CD)138-selected tumor gene expression to control for tumor burden, we identified a subgroup of patients with an adverse TME associated with 17 fewer months of progression-free survival (PFS) (95% confidence interval [CI] 5-29, 49-69 versus 70-82 months, χ2 p = 0.001) and 15 fewer months of overall survival (OS; 95% CI -1 to 31, 92-120 versus 113-129 months, χ2 p = 0.036). Using immunohistochemistry-validated computational tools that identify distinct cell types from bulk gene expression, we showed that the adverse outcome was correlated with elevated CD8+ T cell and reduced granulocytic cell proportions. This microenvironment develops during the progression of premalignant to malignant disease and becomes less prevalent after therapy, in which it is associated with improved outcomes. In patients with quantified International Staging System (ISS) stage and 70-gene Prognostic Risk Score (GEP-70) scores, taking the microenvironment into consideration would have identified an additional 40 out of 290 patients (14%, premutation p = 0.001) with significantly worse outcomes (PFS, 95% CI 6-36, 49-73 versus 74-90 months) who were not identified by existing clinical (ISS stage III) and tumor (GEP-70) criteria as high risk. The main limitations of this study are that it relies on computationally identified cell types and that patients were treated with thalidomide rather than current therapies. CONCLUSIONS: In this study, we observe that granulocyte signatures in the MM TME contribute to a more accurate prognosis. This implies that future researchers and clinicians treating patients should quantify TME components, in particular monocytes and granulocytes, which are often ignored in microenvironment studies.

Mycobacterium tuberculosis Transfer RNA Induces IL-12p70 via Synergistic Activation of Pattern Recognition Receptors within a Cell Network.

Upon recognition of a microbial pathogen, the innate and adaptive immune systems are linked to generate a cell-mediated immune response against the foreign invader. The culture filtrate of Mycobacterium tuberculosis contains ligands, such as M. tuberculosis tRNA, that activate the innate immune response and secreted Ags recognized by T cells to drive adaptive immune responses. In this study, bioinformatics analysis of gene-expression profiles derived from human PBMCs treated with distinct microbial ligands identified a mycobacterial tRNA-induced innate immune network resulting in the robust production of IL-12p70, a cytokine required to instruct an adaptive Th1 response for host defense against intracellular bacteria. As validated by functional studies, this pathway contained a feed-forward loop, whereby the early production of IL-18, type I IFNs, and IL-12p70 primed NK cells to respond to IL-18 and produce IFN-γ, enhancing further production of IL-12p70. Mechanistically, tRNA activates TLR3 and TLR8, and this synergistic induction of IL-12p70 was recapitulated by the addition of a specific TLR8 agonist with a TLR3 ligand to PBMCs. These data indicate that M. tuberculosis tRNA activates a gene network involving the integration of multiple innate signals, including types I and II IFNs, as well as distinct cell types to induce IL-12p70.

Age-Specific Adjuvant Synergy: Dual TLR7/8 and Mincle Activation of Human Newborn Dendritic Cells Enables Th1 Polarization.

Due to functionally distinct cell-mediated immunity, newborns and infants are highly susceptible to infection with intracellular pathogens. Indeed, neonatal Ag-presenting dendritic cells (DCs) demonstrate impaired Th1 responses to many candidate adjuvants, including most TLR agonists (TLRAs). Combination adjuvantation systems may provide enhanced immune activation but have typically been developed without regard to the age of the target population. We posited that distinct combinations of TLRAs and C-type lectin receptor agonists may enhance Th1 responses of newborn DCs. TLRA/C-type lectin receptor agonist combinations were screened for enhancement of TNF production by human newborn and adult monocyte-derived DCs cultured in 10% autologous plasma or in newborn cord, infant, adult, and elderly whole blood. Monocyte-derived DC activation was characterized by targeted gene expression analysis, caspase-1 and NF-κB studies, cytokine multiplex and naive autologous CD4+ T cell activation. Dual activation of newborn DCs via the C-type lectin receptor, macrophage-inducible C-type lectin (trehalose-6,6-dibehenate), and TLR7/8 (R848) greatly enhanced caspase-1 and NF-κB activation, Th1 polarizing cytokine production and autologous Th1 polarization. Combined activation via TLR4 (glycopyranosyl lipid adjuvant aqueous formulation) and Dectin-1 (ß-glucan peptide) acted synergistically in newborns and adults, but to a lesser extent. The degree of synergy varied dramatically with age, and was the greatest in newborns and infants with less synergy in adults and elders. Overall, combination adjuvant systems demonstrate markedly different immune activation with age, with combined DC activation via Macrophage-inducible C-type lectin and TLR7/8 representing a novel approach to enhance the efficacy of early-life vaccines.

Toll-like Receptor 4 Ligands Down-regulate Fcγ Receptor IIb (FcγRIIb) via MARCH3 Protein-mediated Ubiquitination.

Monocytes and macrophages are critical for the effectiveness of monoclonal antibody therapy. Responses to antibody-coated tumor cells are largely mediated by Fcγ receptors (FcγRs), which become activated upon binding to immune complexes. FcγRIIb is an inhibitory FcγR that negatively regulates these responses, and it is expressed on monocytes and macrophages. Therefore, deletion or down-regulation of this receptor may substantially enhance therapeutic outcomes. Here we screened a panel of Toll-like receptor (TLR) agonists and found that those selective for TLR4 and TLR8 could significantly down-regulate the expression of FcγRIIb. Upon further examination, we found that treatment of monocytes with TLR4 agonists could lead to the ubiquitination of FcγRIIb protein. A search of our earlier microarray database of monocytes activated with the TLR7/8 agonist R-848 (in which FcγRIIb was down-regulated) revealed an up-regulation of membrane-associated ring finger (C3HC4) 3 (MARCH3), an E3 ubiquitin ligase. Therefore, we tested whether LPS treatment could up-regulate MARCH3 in monocytes and whether this E3 ligase was involved with LPS-mediated FcγRIIb down-regulation. The results showed that LPS activation of TLR4 significantly increased MARCH3 expression and that siRNA against MARCH3 prevented the decrease in FcγRIIb following LPS treatment. These data suggest that activation of TLR4 on monocytes can induce a rapid down-regulation of FcγRIIb protein and that this involves ubiquitination.

Granzyme B expression is enhanced in human monocytes by TLR8 agonists and contributes to antibody-dependent cellular cytotoxicity.

FcγRs are critical mediators of mAb cancer therapies, because they drive cytotoxic processes upon binding of effector cells to opsonized targets. Along with NK cells, monocytes are also known to destroy Ab-coated targets via Ab-dependent cellular cytotoxicity (ADCC). However, the precise mechanisms by which monocytes carry out this function have remained elusive. In this article, we show that human monocytes produce the protease granzyme B upon both FcγR and TLR8 activation. Treatment with TLR8 agonists elicited granzyme B and also enhanced FcγR-mediated granzyme B production in an additive fashion. Furthermore, monocyte-mediated ADCC against cetuximab-coated tumor targets was enhanced by TLR8 agonist treatment, and this enhancement of ADCC required granzyme B. Hence we have identified granzyme B as an important mediator of FcγR function in human monocytes and have uncovered another mechanism by which TLR8 agonists may enhance FcγR-based therapies.

Genetic program activity delineates risk, relapse, and therapy responsiveness in multiple myeloma.

Despite recent advancements in the treatment of multiple myeloma (MM), nearly all patients ultimately relapse and many become refractory to multiple lines of therapies. Therefore, we not only need the ability to predict which patients are at high risk for disease progression but also a means to understand the mechanisms underlying their risk. Here, we report a transcriptional regulatory network (TRN) for MM inferred from cross-sectional multi-omics data from 881 patients that predicts how 124 chromosomal abnormalities and somatic mutations causally perturb 392 transcription regulators of 8549 genes to manifest in distinct clinical phenotypes and outcomes. We identified 141 genetic programs whose activity profiles stratify patients into 25 distinct transcriptional states and proved to be more predictive of outcomes than did mutations. The coherence of these programs and accuracy of our network-based risk prediction was validated in two independent datasets. We observed subtype-specific vulnerabilities to interventions with existing drugs and revealed plausible mechanisms for relapse, including the establishment of an immunosuppressive microenvironment. Investigation of the t(4;14) clinical subtype using the TRN revealed that 16% of these patients exhibit an extreme-risk combination of genetic programs (median progression-free survival of 5 months) that create a distinct phenotype with targetable genes and pathways.

Phase Ib Study of Immune Biomarker Modulation with Neoadjuvant Cetuximab and TLR8 Stimulation in Head and Neck Cancer to Overcome Suppressive Myeloid Signals.

Purpose: The response rate of patients with head and neck squamous cell carcinoma (HNSCC) to cetuximab therapy is only 15% to 20%, despite frequent EGFR overexpression. Because immunosuppression is common in HNSCC, we hypothesized that adding a proinflammatory TLR8 agonist to cetuximab therapy might result in enhanced T-lymphocyte stimulation and anti-EGFR-specific priming.Experimental Design: Fourteen patients with previously untreated HNSCC were enrolled in this neoadjuvant trial and treated preoperatively with 3 to 4 weekly doses of motolimod (2.5 mg/m2) and cetuximab. Correlative tumor and peripheral blood specimens were obtained at baseline and at the time of surgical resection and analyzed for immune biomarker changes. Preclinical in vitro studies were also performed to assess the effect of cetuximab plus motolimod on myeloid cells.Results: TLR8 stimulation skewed monocytes toward an M1 phenotype and reversed myeloid-derived suppressor cell (MDSC) suppression of T-cell proliferation in vitro These data were validated in a prospective phase Ib neoadjuvant trial, in which fewer MDSC and increased M1 monocyte infiltration were found in tumor-infiltrating lymphocytes. Motolimod plus cetuximab also decreased induction of Treg and reduced markers of suppression, including CTLA-4, CD73, and membrane-bound TGFß. Significantly increased circulating EGFR-specific T cells were observed, concomitant with enhanced CD8+ T-cell infiltration into tumors. These T cells manifested increased T-cell receptor (TCR) clonality, upregulation of the costimulatory receptor CD27, and downregulation of inhibitory receptor TIGIT.Conclusions: Enhanced inflammatory stimulation in the tumor microenvironment using a TLR agonist overcomes suppressive myeloid and regulatory cells, enhancing the cellular antitumor immune response by therapeutic mAb in HNSCC. Clin Cancer Res; 24(1); 62-72. ©2017 AACR.

Effect of Adding Motolimod to Standard Combination Chemotherapy and Cetuximab Treatment of Patients With Squamous Cell Carcinoma of the Head and Neck: The Active8 Randomized Clinical Trial.

Importance: Immunotherapy for recurrent and/or metastatic (R/M) squamous cell carcinoma of the head and neck (SCCHN) is promising. The toll-like receptor 8 (TLR8) agonist motolimod may stimulate innate and adaptive immunity. Objective: To determine whether motolimod improves outcomes for R/M SCCHN when combined with standard therapy. Design, Setting, and Participants: The Active8 study was a multicenter, randomized, double-blind, placebo-controlled clinical trial enrolling adult patients (age ≥18 years) with histologically confirmed R/M SCCHN of the oral cavity, oropharynx, hypopharynx, or larynx between October 2013 and August 2015. Follow-up ended September 2016. Analysis for the present report was conducted between June 2016 and December 2017. Interventions: Combination treatment with platinum (carboplatin or cisplatin), fluorouracil, cetuximab (the EXTREME regimen), and either placebo or motolimod, each administered intravenously every 3 weeks. Patients received a maximum of 6 chemotherapy cycles, after which patients received weekly cetuximab with either placebo or motolimod every 4 weeks. Main Outcomes and Measures: Progression-free survival (PFS) as determined by independent central review using immune-related RECIST (Response Evaluation Criteria in Solid Tumors). Key secondary end points included overall survival (OS) and safety. Results: Of 195 patients enrolled, 85% were men (n = 166); 82% were white (n = 159); median age was 58 years (range 23-81 years). Median PFS was 6.1 vs 5.9 months (hazard ratio [HR], 0.99; 1-sided 90% CI, 0.00-1.22; P = .47), and median OS was 13.5 vs 11.3 months (HR, 0.95; 1-sided 90% CI, 0.00-1.22; P = .40) for motolimod vs placebo. Increased incidence of injection site reactions, pyrexia, chills, anemia, and acneiform rash were noted with motolimod. Of 83 cases oropharyngeal cancer, 52 (63%) were human papillomavirus (HPV) positive. In a prespecified subgroup analysis of HPV-positive participants, motolimod vs placebo resulted in significantly longer PFS (7.8 vs 5.9 months; HR, 0.58; 1-sided 90% CI, 0.00-0.90; P = .046) and OS (15.2 vs 12.6 months; HR, 0.41; 1-sided 90% CI, 0.00-0.77; P = .03). In an exploratory analysis, patients with injection site reactions had longer PFS and OS (median PFS, 7.1 vs 5.9 months; HR, 0.69; 1-sided 90% CI, 0.00-0.93; P = .06; and median OS, 18.7 vs 12.6; HR, 0.56; 1-sided 90% CI, 0.00-0.81; P = .02). Conclusions and Relevance: Adding motolimod to the EXTREME regimen was well tolerated but did not improve PFS or OS in the intent-to-treat population. Significant benefit was observed in HPV-positive patients and those with injection site reactions, suggesting that TLR8 stimulation may benefit subset- and biomarker-selected patients. Trial Registration: ClinicalTrials.gov identifier: NCT01836029.

Bacterial flagellin is a dominant antigen in Crohn disease.

Chronic intestinal inflammation, as seen in inflammatory bowel disease (IBD), results from an aberrant and poorly understood mucosal immune response to the microbiota of the gastrointestinal tract in genetically susceptible individuals. Here we used serological expression cloning to identify commensal bacterial proteins that could contribute to the pathogenesis of IBD. The dominant antigens identified were flagellins, molecules known to activate innate immunity via Toll-like receptor 5 (TLR5), and critical targets of the acquired immune system in host defense. Multiple strains of colitic mice had elevated serum anti-flagellin IgG2a responses and Th1 T cell responses to flagellin. In addition, flagellin-specific CD4(+) T cells induced severe colitis when adoptively transferred into naive SCID mice. Serum IgG to these flagellins, but not to the dissimilar Salmonella muenchen flagellin, was elevated in patients with Crohn disease, but not in patients with ulcerative colitis or in controls. These results identify flagellins as a class of immunodominant antigens that stimulate pathogenic intestinal immune reactions in genetically diverse hosts and suggest new avenues for the diagnosis and antigen-directed therapy of patients with IBD.

Anti-flagellin (CBir1) phenotypic and genetic Crohn's disease associations.

BACKGROUND: Antibody reactivity to microbial antigens correlates with distinct Crohn's disease (CD) phenotypes such as fistulizing or fibrostenosing disease. We examined the association between anti-CBir1 and clinical phenotypes and NOD2 variants in a large cohort of adult CD patients. METHODS: Sera and genomic DNA were collected from 731 patients with CD and tested for immune responses to I2, CBir1, oligomannan, and outer membrane porin C (OmpC) and the 3 most common CD-associated NOD2 variants. RESULTS: Anti-CBir1 reactivity was significantly associated with fibrostenosis (FS), internal penetrating (IP) disease phenotypes, small bowel (SB) involvement, and SB surgery but negatively associated with ulcerative colitis (UC)-like CD. Multivariate logistic regression analysis showed that anti-CBir1 was independently associated with FS and UC-like CD irrespective of the antibody reactivity to I2, oligomannan, or OmpC, but not with SB involvement or SB surgery. The magnitude of anti-CBir1 reactivity, when added to the quantitative response toward the other 3 CD-associated antigens, enhances the discrimination of FS, IP, UC-like CD, and SB involvement, but not SB surgery. Finally, although the frequency of anti-CBir1 was similar in patients with none versus at least 1 NOD2 variant, the quantitative response to CBir1 flagellin was significantly higher in patients with CD carrying at least 1 NOD2 variant versus those carrying no variants (median anti-CBir1 titer 33.39 versus 28.36, respectively; P = 0.01). CONCLUSIONS: Anti-CBir1 serum reactivity in CD patients is independently associated with FS and complicated SB CD. Quantitative, but not qualitative, response to CBir1 is also significantly associated with the CD-associated NOD2 variants.

Phase Ib Trial of the Toll-like Receptor 8 Agonist, Motolimod (VTX-2337), Combined with Cetuximab in Patients with Recurrent or Metastatic SCCHN.

Purpose: As Toll-like receptors (TLR) are key mediators of immune responses, TLR agonists may be important for augmenting the efficacy of therapies for squamous cell carcinoma of the head and neck (SCCHN). Motolimod (VTX-2337), a selective small-molecule agonist of TLR8, stimulates natural killer (NK) cells, dendritic cells, and monocytes. A phase Ib clinical trial assessed the safety and antitumor activity of motolimod in combination with cetuximab in patients with SCCHN. Correlative biomarkers of immune activity were explored.Experimental Design: Thirteen patients with recurrent or metastatic SCCHN were enrolled in this open-label, dose-escalation study using a standard 3 + 3 design. Doses of motolimod (2.5, 3.0, or 3.5 mg/m2) were given on days 1, 8, and 15, in combination with fixed weekly doses of cetuximab in 28-day cycles.Results: There were no protocol-defined dose-limiting toxicities, drug-related deaths, or evidence of synergistic toxicities between motolimod and cetuximab. Clinical tolerability at the 3.5 mg/m2 dose level was not optimal for repeated dosing and 3.0 mg/m2 was identified as the MTD. Two patients achieved partial responses for an overall response rate of 15%. Five patients had disease stabilization equating to a disease control rate of 54%. Statistically significant increases in plasma cytokines and in the frequency and activation of circulating NK cells were observed.Conclusions: Motolimod can be safely administered in combination with cetuximab with an acceptable toxicity profile. Encouraging antitumor activity and robust pharmacodynamic responses were observed. Motolimod is being further investigated in a phase II trial in patients with SCCHN (ClinicalTrials.gov ID: NCT01836029). Clin Cancer Res; 23(10); 2442-50. ©2016 AACR.

Integrative Development of a TLR8 Agonist for Ovarian Cancer Chemoimmunotherapy.

Purpose: Immunotherapy is an emerging paradigm for the treatment of cancer, but the potential efficacy of many drugs cannot be sufficiently tested in the mouse. We sought to develop a rational combination of motolimod-a novel Toll-like receptor 8 (TLR8) agonist that stimulates robust innate immune responses in humans but diminished responses in mice-with pegylated liposomal doxorubicin (PLD), a chemotherapeutic that induces immunogenic cell death.Experimental Design: We followed an integrative pharmacologic approach including healthy human volunteers, non-human primates, NSG-HIS ("humanized immune system") mice reconstituted with human CD34+ cells, and patients with cancer to test the effects of motolimod and to assess the combination of motolimod with PLD for the treatment of ovarian cancer.Results: The pharmacodynamic effects of motolimod monotherapy in NSG-HIS mice closely mimicked those in non-human primates and healthy human subjects, whereas the effects of the motolimod/PLD combination in tumor-bearing NSG-HIS mice closely mimicked those in patients with ovarian cancer treated in a phase Ib trial (NCT01294293). The NSG-HIS mouse helped elucidate the mechanism of action of the combination and revealed a positive interaction between the two drugs in vivo The combination produced no dose-limiting toxicities in patients with ovarian cancer. Two subjects (15%) had complete responses and 7 subjects (53%) had disease stabilization. A phase II study was consequently initiated.Conclusions: These results are the first to demonstrate the value of pharmacologic approaches integrating the NSG-HIS mouse, non-human primates, and patients with cancer for the development of novel immunomodulatory anticancer agents with human specificity. Clin Cancer Res; 23(8); 1955-66. ©2016 AACR.

Molecular approaches to the role of the microbiota in inflammatory bowel disease.

The microbiota plays a crucial role in experimental models of inflammatory bowel disease, but the exact mechanisms of its effects are unknown. These studies took two molecular approaches to this question. The first used amplification of the 16s ribosomal DNA to define microbial diversity in the colon. Although there were differences in colitic and non-colitic mice, we could not determine whether this was primary or secondary to the disease. The second approach used serologic expression cloning to identify the microbial proteins stimulating the pathogenic immune response. Previously unknown microbial flagellins were the dominant cluster of antigens identified. About half of the sera from patients with Crohn's disease have IgG antibodies to these flagellins.

Immunotherapy for prostate cancer using prostatic acid phosphatase loaded antigen presenting cells.

Dendritic cells from patients with cancer are deficient in number and functional activity, leading to inadequate tumor immunosurveillance as a result of poor induction of T-cell antitumor responses. Loaded dendritic cell therapy is a vaccination strategy aimed at eliciting tumor antigen-specific, T-cell immune responses. Loaded dendritic cell therapy using prostatic acid phosphatase (APC8015; Provenge, Dendreon Corp., Seattle, WA) as an immunogen has shown a survival benefit in patients with metastatic hormone-refractory prostate cancer in a randomized phase III trial. This review will summarize the prostate cancer clinical trials using APC8015 and discuss the potential future role of APC8015 in prostate cancer treatment.

VTX-1463, a novel TLR-8 agonist, attenuates nasal congestion after ragweed challenge in sensitized beagle dogs.

VTX-1463 is a selective toll-like receptor (TLR) 8 agonist that activates a subset of innate immune cells to produce a unique cytokine profile. Delivery of VTX-1463 via nasal spray may modulate the nasal response in allergic rhinitis. The aim of this study was to determine the effects of VTX-1463 on the nasal response in a dog model of allergic rhinitis. Ragweed (RW)-sensitized dogs were pretreated with increasing doses of VTX-1463 1 day prior to RW challenge or with two doses (4 or 8 days and 1 day prior to RW). Changes in nasal cavity volume (NV) were determined by acoustic rhinometry and nasal lavage fluid was assessed for histamine, lipid mediators, and cellular infiltrates at sequential times following RW challenge. VTX-1463 pretreatment significantly preserved NV during the acute response to RW challenge for all doses tested. The area under the curve (AUC) for NV over the 1.5 h assessment period in RW challenged vehicle controls averaged 51.5% (SEM: ±2.12%) of the baseline NV over all studies. A single 100 µg dose of VTX-1463 given 1 day prior to RW yielded an AUC for NV of 69.3% (±6.59%) of baseline, while a 1000 µg dose administered twice (8 days and 1 day prior to RW) resulted in an AUC for NV of 85.4% (±4.74%, P < 0.05) of baseline. For a single 1000 µg VTX-1463 dose 1 day prior to RW, multiple mediators produced by mast cells, including histamine, PGE2, PGD2, and cysteinyl LTs, were significantly reduced relative to the vehicle control. The selective TLR8 agonist, VTX-1463, preserved NV in a dose-dependent manner in the acute phase of a nasal allergic response. The therapeutic effect appears to result from attenuated mast cell mediator release. Modulating the local cytokine response via TLR8 agonism appears to have a therapeutic effect on the acute allergic nasal response.

Coordinated Activation of Toll-Like Receptor8 (TLR8) and NLRP3 by the TLR8 Agonist, VTX-2337, Ignites Tumoricidal Natural Killer Cell Activity.

UNLABELLED: VTX-2337 (USAN: motolimod) is a selective toll-like receptor 8 (TLR8) agonist, which is in clinical development as an immunotherapy for multiple oncology indications, including squamous cell carcinoma of the head and neck (SCCHN). Activation of TLR8 enhances natural killer cell activation, increases antibody-dependent cell-mediated cytotoxicity, and induces Th1 polarizing cytokines. Here, we show that VTX-2337 stimulates the release of mature IL-1ß and IL-18 from monocytic cells through coordinated actions on both TLR8 and the NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome complex. In vitro, VTX-2337 primed monocytic cells to produce pro-IL-1ß, pro-IL-18, and caspase-1, and also activated the NLRP3 inflammasome, thereby mediating the release of mature IL-1ß family cytokines. Inhibition of caspase-1 blocked VTX-2337-mediated NLRP3 inflammasome activation, but had little impact on production of other TLR8-induced mediators such as TNFα. IL-18 activated natural killer cells and complemented other stimulatory pathways, including FcγRIII and NKG2D, resulting in IFNγ production and expression of CD107a. NLRP3 activation in vivo was confirmed by a dose-related increase in plasma IL-1ß and IL-18 levels in cynomolgus monkeys administered VTX-2337. These results are highly relevant to clinical studies of combination VTX-2337/cetuximab treatment. Cetuximab, a clinically approved, epidermal growth factor receptor-specific monoclonal antibody, activates NK cells through interactions with FcγRIII and facilitates ADCC of tumor cells. Our preliminary findings from a Phase I open-label, dose-escalation, trial that enrolled 13 patients with recurrent or metastatic SCCHN show that patient NK cells become more responsive to stimulation by NKG2D or FcγRIII following VTX-2337 treatment. Together, these results indicate that TLR8 stimulation and inflammasome activation by VTX-2337 can complement FcγRIII engagement and may augment clinical responses in SCCHN patients treated with cetuximab. TRIAL REGISTRATION: ClinicalTrials.gov NCT01334177.

Taking toll: lipid A mimetics as adjuvants and immunomodulators.

Vaccine adjuvants based on the structure of lipid A, such as monophosphoryl lipid A (MLA), have proven to be safe and effective in inducing immune responses to heterologous proteins in animal and human vaccines. Recent work on the development of a recombinant vaccine for leishmaniasis has demonstrated that a clinical grade MLA formulation - MPL(R) adjuvant - is essential in the development of a protective response. Preliminary evidence suggests that MLA and a chemically distinct family of lipid A mimetics - the aminoalkyl glucosaminide 4-phosphates - act on Toll-like receptor 4 (TLR4). As TLR4 agonists, they have potent immunomodulatory effects when used both as vaccine adjuvants and as stand-alone products. Novel approaches to vaccine development could benefit from taking full advantage of the effects of these compounds on innate and adaptive responses.

Late-Stage Cancer Patients Remain Highly Responsive to Immune Activation by the Selective TLR8 Agonist Motolimod (VTX-2337).

PURPOSE: Immunotherapy as a treatment for cancer holds the promise of complete and durable tumor remission, yet the immunosuppressive environment created by many tumors, advanced patient age, and previous treatments with cytotoxic agents may limit the approach. The activity of motolimod (VTX-2337), a potent and selective Toll-like receptor 8 (TLR8) agonist, was therefore assessed in the context of advanced, late-stage cancer patients. EXPERIMENTAL DESIGN: The repertoire of mediators induced from human peripheral blood mononuclear cells in response to motolimod was characterized. Translational studies in cynomolgus monkeys elucidated the activity of motolimod on an intact immune system, identified biomarkers of TLR8 activation, and defined the relationship between the pharmacokinetic and pharmacodynamic (PK/PD) response. The PK/PD relationship for motolimod in cancer patients was assessed, compared with preclinical findings, and contrasted with activity in healthy volunteers. RESULTS: In late-stage cancer patients, plasma levels of multiple biomarkers, including IL6, G-CSF, MCP-1, and MIP1-ß, increased with increasing motolimod dose. The magnitude and breadth of the biomarker response closely aligned with the response seen in preclinical studies, demonstrating that advanced cancer patients remained responsive to TLR8 activation. In addition, the PK/PD response in cancer patients closely aligned with the activity of motolimod seen in healthy volunteers. CONCLUSIONS: Late-stage cancer patients are highly sensitive to TLR8 activation by motolimod. Tumor burden, advanced age, and prior treatment history with cytotoxic agents did not moderate or modify the response predicted by nonclinical studies and confirmed in healthy volunteers. Clin Cancer Res; 21(24); 5445-52. ©2015 AACR.

A phase I dose-finding study of the novel Toll-like receptor 8 agonist VTX-2337 in adult subjects with advanced solid tumors or lymphoma.

PURPOSE: This phase I, open-label, uncontrolled, ascending-dose study explored the safety, maximum tolerated dose (MTD), pharmacokinetics, and pharmacology of the TLR8 agonist VTX-2337 in subjects with advanced solid tumors or lymphoma. EXPERIMENTAL DESIGN: VTX-2337 doses (0.1-3.9 mg/m(2)) were administered subcutaneously on days 1, 8, and 15 of each 28-day cycle. Safety/tolerability assessments included adverse events (AE); physical, ophthalmologic, and laboratory evaluations; and electrocardiograms. Dose-limiting toxicities (DLT) were evaluated during the first cycle. Pharmacokinetics were evaluated after the first dose. Plasma samples were quantitatively assessed for chemokines, cytokines, and other inflammatory mediators. Antitumor activity was assessed. RESULTS: Thirty-three subjects were enrolled in 8 cohorts and received an average of 2 treatment cycles (range, 1-8 cycles). Most AEs were grades 1 to 2; the most common drug-related AEs were injection site reactions, chills, pyrexia, and influenza-like illness. One DLT was reported: grade 3 hypotension (3.9 mg/m(2)). The MTD was considered the highest dose administered. Peak drug plasma levels and total systemic exposure were generally dose proportional. At doses ≥0.4 mg/m(2), increases above baseline levels were observed for plasma levels of G-CSF, monocyte chemoattractant protein-1, macrophage inflammatory protein-1ß, and TNFα. Eight subjects (24.2%) had a best response of stable disease (median duration, 54.5 days). CONCLUSIONS: VTX-2337 is clinically well tolerated and biologically active with a predictable pharmacokinetic profile. Suitable doses for testing in combination studies were identified. Phase II placebo-controlled studies of VTX-2337 in combination with doxorubicin in ovarian cancer, and in combination with platinum chemotherapy, 5 FU, and cetuximab in head and neck cancer have been initiated (NCT #01666444 and NCT#01836029).

The ultra-potent and selective TLR8 agonist VTX-294 activates human newborn and adult leukocytes.

BACKGROUND: Newborns display distinct immune responses that contribute to susceptibility to infection and reduced vaccine responses. Toll-like receptor (TLR) agonists may serve as vaccine adjuvants, when given individually or in combination, but responses of neonatal leukocytes to many TLR agonists are diminished. TLR8 agonists are more effective than other TLR agonists in activating human neonatal leukocytes in vitro, but little is known about whether different TLR8 agonists may distinctly activate neonatal leukocytes. We characterized the in vitro immuno-stimulatory activities of a novel benzazepine TLR8 agonist, VTX-294, in comparison to imidazoquinolines that activate TLR8 (R-848; (TLR7/8) CL075; (TLR8/7)), with respect to activation of human newborn and adult leukocytes. Effects of VTX-294 and R-848 in combination with monophosphoryl lipid A (MPLA; TLR4) were also assessed. METHODS: TLR agonist specificity was assessed using TLR-transfected HEK293 cells expressing a NF-κB reporter gene. TLR agonist-induced cytokine production was measured in human newborn cord and adult peripheral blood using ELISA and multiplex assays. Newborn and adult monocytes were differentiated into monocyte-derived dendritic cells (MoDCs) and TLR agonist-induced activation assessed by cytokine production (ELISA) and co-stimulatory molecule expression (flow cytometry). RESULTS: VTX-294 was ≈ 100x more active on TLR8- than TLR7-transfected HEK cells (EC50, ≈ 50 nM vs. ≈ 5700 nM). VTX-294-induced TNF and IL-1ß production were comparable in newborn cord and adult peripheral blood, while VTX-294 was 1 log more potent in inducing TNF and IL-1ß production than MPLA, R848 or CL075. Combination of VTX-294 and MPLA induced greater blood TNF and IL-1ß responses than combination of R-848 and MPLA. VTX-294 also potently induced expression of cytokines and co-stimulatory molecules HLA-DR and CD86 in human newborn MoDCs. CONCLUSIONS: VTX-294 is a novel ultra-potent TLR8 agonist that activates newborn and adult leukocytes and is a candidate vaccine adjuvant in both early life and adulthood.