Purpose/Objective(s)Cetuximab, an EGFR-specific monoclonal antibody, is an approved therapy for SCCHN alone or combined with radiation or chemotherapy. Beyond blocking the EFGR signaling pathway, natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC) is important for cetuximab-mediated tumor killing; hence, NK cell activation may enhance the anti-tumoral effect. VTX-2337, a novel Toll-like receptor 8 (TLR8) agonist, stimulates NK cells, myeloid-derived dendritic cells, and monocytes. Preclinical data demonstrated synergistic NK cell activation and enhancement of ADCC with combination cetuximab and VTX-2337, forming the rationale to assess the safety, tolerability, immunological correlates, and efficacy of this combination in SCCHN patients.Materials/MethodsThis open label phase 1b study in platinum-refractory or -intolerant recurrent or metastatic SCCHN patients (NCT01836029; N=12) included cetuximab-naïve patients who received a 400 mg/m2 loading dose followed by 250 mg/m2 weekly for a lead-in assessment for cetuximab toxicity and previously cetuximab-treated patients who received 250 mg/m2 weekly, prior to VTX-2337 combination. Using a 3+3 design, patients were enrolled into cohorts of escalating VTX-2337 doses (2.5, 3.0, 3.5 mg/m2) given SC days 1, 8, 15 q 28 day cycle. Correlative pharmacokinetic and pharmacodynamic immunologic assessments of response and activity were performed. Response was evaluated using RECIST 1.1.ResultsThis combination was well-tolerated with no dose-limiting toxicities, no serious, unexpected or synergistic drug-related toxicities between cetuximab and VTX-2337 in 10 patients. Toxicities were similar in scope and severity to those observed with cetuximab (fatigue, skin rash, cough, malaise) or VTX-2337 alone (Gr 1/2 injection site reaction, flu-like symptoms and fatigue). Commonly observed flu-like symptoms, injection site reactions and fatigue established the 3.0 mg/m2 dose as most tolerable. Serum biomarkers were consistent with TLR8 activation. Ex vivo analysis of NK cells collected pre- and post-dose demonstrated enhanced NK cell mobilization and activation. In 8 response-evaluable patients, one partial response, 4 stable disease and 3 disease progression were observed. Results of this ongoing study will be updated.ConclusionsCetuximab and VTX-2337 in combination is tolerable and active in SCCHN patients. Clinical data and serum biomarkers demonstrating immunostimulation with marked NK cell activation provide rationale for further study in SCCHN. A randomized, placebo-controlled, phase 2 trial comparing cetuximab + platinum + 5-FU +/- VTX-2337 has been initiated. Purpose/Objective(s)Cetuximab, an EGFR-specific monoclonal antibody, is an approved therapy for SCCHN alone or combined with radiation or chemotherapy. Beyond blocking the EFGR signaling pathway, natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC) is important for cetuximab-mediated tumor killing; hence, NK cell activation may enhance the anti-tumoral effect. VTX-2337, a novel Toll-like receptor 8 (TLR8) agonist, stimulates NK cells, myeloid-derived dendritic cells, and monocytes. Preclinical data demonstrated synergistic NK cell activation and enhancement of ADCC with combination cetuximab and VTX-2337, forming the rationale to assess the safety, tolerability, immunological correlates, and efficacy of this combination in SCCHN patients. Cetuximab, an EGFR-specific monoclonal antibody, is an approved therapy for SCCHN alone or combined with radiation or chemotherapy. Beyond blocking the EFGR signaling pathway, natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC) is important for cetuximab-mediated tumor killing; hence, NK cell activation may enhance the anti-tumoral effect. VTX-2337, a novel Toll-like receptor 8 (TLR8) agonist, stimulates NK cells, myeloid-derived dendritic cells, and monocytes. Preclinical data demonstrated synergistic NK cell activation and enhancement of ADCC with combination cetuximab and VTX-2337, forming the rationale to assess the safety, tolerability, immunological correlates, and efficacy of this combination in SCCHN patients. Materials/MethodsThis open label phase 1b study in platinum-refractory or -intolerant recurrent or metastatic SCCHN patients (NCT01836029; N=12) included cetuximab-naïve patients who received a 400 mg/m2 loading dose followed by 250 mg/m2 weekly for a lead-in assessment for cetuximab toxicity and previously cetuximab-treated patients who received 250 mg/m2 weekly, prior to VTX-2337 combination. Using a 3+3 design, patients were enrolled into cohorts of escalating VTX-2337 doses (2.5, 3.0, 3.5 mg/m2) given SC days 1, 8, 15 q 28 day cycle. Correlative pharmacokinetic and pharmacodynamic immunologic assessments of response and activity were performed. Response was evaluated using RECIST 1.1. This open label phase 1b study in platinum-refractory or -intolerant recurrent or metastatic SCCHN patients (NCT01836029; N=12) included cetuximab-naïve patients who received a 400 mg/m2 loading dose followed by 250 mg/m2 weekly for a lead-in assessment for cetuximab toxicity and previously cetuximab-treated patients who received 250 mg/m2 weekly, prior to VTX-2337 combination. Using a 3+3 design, patients were enrolled into cohorts of escalating VTX-2337 doses (2.5, 3.0, 3.5 mg/m2) given SC days 1, 8, 15 q 28 day cycle. Correlative pharmacokinetic and pharmacodynamic immunologic assessments of response and activity were performed. Response was evaluated using RECIST 1.1. ResultsThis combination was well-tolerated with no dose-limiting toxicities, no serious, unexpected or synergistic drug-related toxicities between cetuximab and VTX-2337 in 10 patients. Toxicities were similar in scope and severity to those observed with cetuximab (fatigue, skin rash, cough, malaise) or VTX-2337 alone (Gr 1/2 injection site reaction, flu-like symptoms and fatigue). Commonly observed flu-like symptoms, injection site reactions and fatigue established the 3.0 mg/m2 dose as most tolerable. Serum biomarkers were consistent with TLR8 activation. Ex vivo analysis of NK cells collected pre- and post-dose demonstrated enhanced NK cell mobilization and activation. In 8 response-evaluable patients, one partial response, 4 stable disease and 3 disease progression were observed. Results of this ongoing study will be updated. This combination was well-tolerated with no dose-limiting toxicities, no serious, unexpected or synergistic drug-related toxicities between cetuximab and VTX-2337 in 10 patients. Toxicities were similar in scope and severity to those observed with cetuximab (fatigue, skin rash, cough, malaise) or VTX-2337 alone (Gr 1/2 injection site reaction, flu-like symptoms and fatigue). Commonly observed flu-like symptoms, injection site reactions and fatigue established the 3.0 mg/m2 dose as most tolerable. Serum biomarkers were consistent with TLR8 activation. Ex vivo analysis of NK cells collected pre- and post-dose demonstrated enhanced NK cell mobilization and activation. In 8 response-evaluable patients, one partial response, 4 stable disease and 3 disease progression were observed. Results of this ongoing study will be updated. ConclusionsCetuximab and VTX-2337 in combination is tolerable and active in SCCHN patients. Clinical data and serum biomarkers demonstrating immunostimulation with marked NK cell activation provide rationale for further study in SCCHN. A randomized, placebo-controlled, phase 2 trial comparing cetuximab + platinum + 5-FU +/- VTX-2337 has been initiated. Cetuximab and VTX-2337 in combination is tolerable and active in SCCHN patients. Clinical data and serum biomarkers demonstrating immunostimulation with marked NK cell activation provide rationale for further study in SCCHN. A randomized, placebo-controlled, phase 2 trial comparing cetuximab + platinum + 5-FU +/- VTX-2337 has been initiated.

RATIONALE: Toll-like receptors (TLRs) have been shown to modulate allergic immune responses. The safety and efficacy of VTX-1463_a novel, small-molecule, TLR8 agonist given once weekly intranasally_was assessed in allergic rhinitis (AR) subjects exposed to allergen in the Vienna Challenge Chamber (VCC). METHODS: This randomized, double-blind, placebo-controlled study was conducted in-season, and enrolled 80 adults with confirmed atopy to grass pollen. Two dosing regimens were compared to placebo: ascending dose (GrpA; 25mcg, 50mcg, 75mcg, 100mcg) and fixed dose (GrpB; 62.5mcg x 4 doses). Subjects were dosed on Days 1, 8, 15 and 22. On Day 24, subjects underwent grass allergen exposure in the VCC, a validated setting for assessing the efficacy of anti-allergic treatment. The primary efficacy endpoints were the average change over 6 hours of allergen exposure in Total Nasal Symptom Score (TNSS; the sum of scores for nasal congestion, itching, sneezing and rhinorrhea) and Active Anterior Rhinomanometry (AAR). Adverse event data were collected for all subjects. RESULTS: Subjects in the overall efficacy population (n=76) who were treated with VTX-1463 and underwent allergen challenge had significantly improved TNSS compared to placebo (p=0.012). This benefit was observed in both GrpA (p=0.008) and GrpB (p=0.012). AAR trended towards a benefit in both treatment groups, but was not statistically significant. VTX-1463 was generally well tolerated. CONCLUSIONS: Four doses of VTX-1463 conferred statistically significant improvement in TNSS compared to placebo. This TLR8 agonist may represent a novel, weekly-administered treatment for AR.

RATIONALE: VTX-378 is a selective TLR8 agonist that interacts with monocytes, macrophages, and myeloid dendritic cells. We hypothesized that delivery of VTX-378 via nasal spray directly to sites of allergic inflammation might initiate rapid anti-allergic activity. METHODS: Ragweed (RW)-sensitized dogs (n=5) were treated with VTX-378 (100, 500 or 1000 μg/dog), given ∼ 24 hours prior to RW challenge. Two VTX-378 pretreatments of 250 or 1000 μg/dog, spaced either 3, 4 or 7 days apart were also evaluated. Changes in nasal cavity volumes (congestion) were determined by acoustic rhinometry. RESULTS: Statistically significant improvements in nasal congestion (44.5% ± 8.7%, 59.1% ± 15.1% and 56.5% ± 10.0% increase in nasal cavity volume vs vehicle) were seen at 100, 500 and 1000 μg/dog doses, respectively, following 24 hour pretreatment. Two 250 μg/dog doses at Day -4 and Day -1, resulted in efficacy comparable to a single 500 μg/dog dose given at Day -1 (58.9% ± 10.3% versus 59.1% ± 15.1%). At a dose of 1000 μg/dog, VTX-378, pretreatment on Days -8 and -1, Days -5 and -1 or only Day -1 significantly attenuated nasal congestion (71.9% ± 7.7%, 65.4% ± 10.3% and 56.5% ± 10.0%, respectively). CONCLUSIONS: Overall, VTX-378 conferred clinical benefit in a dose-dependent manner. Pretreatment with two VTX-378 doses were more effective than a single dose, indicating a greater therapeutic effect with dosing on a weekly interval. These findings suggest that nasal VTX-378 may have a unique pharmacologic profile in the treatment of allergic rhinitis and encourage further studies in humans.

4500 Background APC8015 is an immunotherapy cellular product consisting of autologous peripheral blood mononuclear cells enriched for a dendritic cell fraction pulsed with PA2024, a Prostatic Acid Phosphatase (PAP)-GM-CSF construct. We previously reported results including time to objective progression (TTP) and time to onset of disease related pain (TDRP) from a randomized trial in metastatic HRPC. Reported here are final overall survival (OS) data from this trial, as well as results of immunologic testing. Methods Patients (pts) with asymptomatic, metastatic HRPC were randomized (2:1) to receive APC8015 (n=82) or placebo (n=45) every 2 weeks x 3. Eligible pts had > 25% of cancer cells positive for PAP by central pathology review. The primary endpoint was TTP. TDRP was a secondary endpoint and pts were monitored for OS at 36 months. Monitoring was by weekly pain logs and serial radiologic imaging. Progression and pain were centrally reviewed and pts were followed per protocol for survival for 3 years following randomization. T-cell proliferation to PA2024 was evaluated by 3H-thymidine uptake. The T-Cell Stimulation Index (TCSI) was defined as: counts per minute (cpm) with antigen/cpm without antigen. The TCSI-ratio was defined as the median TCSI at 8 weeks/median TCSI at pre-treatment. Results 127 pts were randomized between 1/00 and 10/01. In an intent-to-treat (ITT) analysis, median OS was 25.9 months for pts on APC8015 compared with 22.0 months for those on placebo (p=0.020, log-rank, hazard ratio 1.625). At 36 months, 33% of APC8015 pts were alive, compared with 11% of placebo pts. The TCSI-ratio was 16.9 for APC8015 and 1.99 for placebo (p=.003, Wilcoxon Rank Sum). Treatment was generally well tolerated. Grade 1 and 2 fevers and rigors were the most common treatment-related AEs. Conclusions In an ITT analysis, treatment with APC8015 resulted in a statistically significant OS advantage of 3.9 months in pts with asymptomatic HRPC, representing the first survival advantage attributed to an immunotherapy product in prostate cancer. APC8015 pts also had an 8-fold increase in the TCSI-ratio. These data support this approach in the treatment of pts with metastatic HRPC. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Dendreon Dendreon Dendreon Dendreon Dendreon Dendreon

Using the human macrophage hybridoma cell line 43 and primary monocytes, we investigated the regulation of class II expression and intracellular Ag trafficking after HIV-1 infection. The HIV-1-infected human macrophage hybridoma cell line, 43HIV, lost class II Ag expression, as determined by immunofluorescence, immunoprecipitation, and Northern blot analysis, 2 wk after infection. Class II expression could be restored by transfection with the full-length HLA-DR4 cDNA driven by a CMV IE promotor. However, even after transfection, the 43HIV cells were incapable of presenting Ag to MHC-matched Ag-specific T cells. This defect was associated with decreased formation of class II-Ag complexes, and similar findings were observed in primary HIV-1BaL-infected monocytes. We investigated Ag uptake using FITC-labeled tetanus, OVA, and keyhole limpet hemocyanin. There was decreased uptake of all three Ags after HIV-1 infection at different time points after Ag pulsing in the 43HIV cells and in primary HIV-1BaL-infected monocytes. There was colocalization of the FITC-labeled Ags with early (cathepsin D) and late endosomal markers (anti-mannose-6-phosphate receptor), lysosomal markers (CD-63), and acidic compartment markers (3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine) in the uninfected cells, but the level of colocalized Ag was reduced in the 43HIV cells and HIV-1BaL-infected monocytes. Our data suggest that class II expression, formation of class II-Ag complexes, and Ag uptake are impaired in chronically HIV-1-infected monocytic cells, which may contribute to the global immunosuppression observed in AIDS.