Jamie Lowe

Abstract 3688: Imprime PGG, a novel innate immune therapeutic in phase 2 clinical development, induces mobilization of monocytes and focalized recruitment of innate immune cells to tumor sites

Immune checkpoint inhibitors (CPI) have shown compelling clinical efficacy in multiple tumor types, though only in a minority of treated patients. Significant research and clinical development are focused on expanding CPI efficacy. Imprime PGG is a novel, IV administered 1,3/1,6 β-glucan PAMP (pathogen-associated molecular pattern) that activates innate immune effector cells to enhance tumor killing, to repolarize the suppressive myeloid cells of the tumor microenvironment and to activate the antigen presentation capability of dendritic cells, macrophages and monocytes. In multiple preclinical models, Imprime enhances the anti-tumor efficacy of CPIs. Imprime is now in multiple phase 2 clinical studies in combination with the CPI, pembrolizumab. We sought to understand more precisely how Imprime activates the innate immune system to enable a concerted innate and adaptive anti-cancer immune response. Using multispectral fluorescence IHC we now show that Imprime induces focalized recruitment of innate immune cells to tumor bearing tissue. In the B16F10 experimental metastasis model, Imprime dosed in combination with the tumor-targeting antibody TA-99 can nearly completely repress the outgrowth of pulmonary metastases across a 19 day time course. At 24h post-Imprime treatment, the presence of Ly6G+ neutrophils was evident throughout the lung tissue. At later time points (72h and beyond) the formation of immune cell clusters was readily evident in lungs from Imprime treated mice and rarer in control mice or mice treated only with TA-99. These immune cell clusters were predominately localized to arterioles near B16 tumor sites and comprised of multiple immune cell subtypes including macs, B cells, T cells as well as a monocyte population that are CD11b+, Ly6G- and F4/80- and strongly positive for MHCII. Consistent with these preclinical findings, IV administration of Imprime to healthy human volunteers increased neutrophil and monocyte mobilization into peripheral blood 2-3 fold 4h post infusion. Imprime treatment also resulted in a significantly increased subset of CD16+ monocytes that are known to have higher antigen presentation capability and express higher levels of the activation markers CD86, PD-L1, and HLA-DR (MHCII). Furthermore, RNA expression profiling of whole blood from Imprime-treated volunteers shows increased expression of the CCL3, CCL4, IL-1β and TNF-α, functional mediators produced by these monocyte populations. Together, these data show that Imprime drives the concerted activation of multiple innate immune subtypes and promotes the appearance of unique monocyte populations that may be critical for an Imprime-induced anti-cancer immune response. Citation Format: Steven Leonardo, Nadine Ottosson, Keith Gorden, Takashi Kangas, Xiaohong Qiu, Ross Fulton, Benjamin Harrison, Adria Jonas, Richard Walsh, Katie Ertelt, Jamie Lowe, Richard Huhn, Jeremy Graff, Nandita Bose, Mark T. Uhlik. Imprime PGG, a novel innate immune therapeutic in phase 2 clinical development, induces mobilization of monocytes and focalized recruitment of innate immune cells to tumor sites [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3688. doi:10.1158/1538-7445.AM2017-3688

Abstract B008: Imprime PGG, an intravenously administered beta glucan PAMP activates the innate immune system: A phase I clinical study to evaluate immunopharmacodynamic responses

Imprime PGG (Imprime), in combination with both tumor-targeting and anti-angiogenic antibodies, has shown promising efficacy in multiple phase 2 clinical trials. In numerous pre-clinical in vivo tumor models, Imprime also enhances the efficacy of immune checkpoint inhibitor antibodies in addition to tumor-targeting and anti-angiogenic antibodies. Imprime is a yeast-derived, soluble β-1,3/1,6 glucan that acts as a Pathogen Associated Molecular Pattern (PAMP) to trigger activation of innate immune effector cells (macrophages, monocytes, neutrophils, dendritic cells (DC)), which orchestrate a coordinated anti-cancer immune response with cells of the adaptive immune system. Ex vivo studies with human whole blood have shown that Imprime forms an immune complex with endogenous anti-beta glucan antibodies (ABA) to trigger a constellation of innate immune functions. These include complement activation via the classical complement pathway, select chemokine production, phenotypic activation and enhanced tumor cell killing by neutrophils and macrophages. Imprime also activates antigen-presenting cells (e.g. macrophages, DC), enabling T cell expansion and activation. In vivo, intravenous (IV) injection of Imprime in C57BL/6 mice increases select chemokine expression, triggers neutrophil and monocyte mobilization into circulation and secondary lymphoid organs, and also enhances DC maturation and antigen-specific T-cell priming. In this study, we show that the immunopharmacodynamic (IPD) responses elicited by IV administration of Imprime in healthy human subjects are consistent with the innate immune responses observed in ex vivo human and in vivo mouse studies. Healthy human volunteers (18-65 yr) were administered single (Cohort 1) or multiple (once weekly for 3 wks-Cohort 2) doses of Imprime PGG (4 mg/kg) by IV infusion over 2-3 hrs. Physical examination with vital signs, adverse event solicitation and timed blood sampling for IPD changes were performed. IPD endpoints included complement protein levels, circulating blood cell lineage counts, ABA concentrations, circulating immune complex (CIC) levels, cytokine and chemokine concentrations, as well as binding and activation of blood leukocytes. Cohort 1 and 2 results show that the complement activation proteins C5a and SC5b-9 were significantly increased in the plasma at the end of infusion (EOI) of Imprime. The formation of Imprime:ABA complexes was evident in a substantial drop of free ABA and a concomitant increase in CIC in the serum also at the EOI. IL-8 and MCP-1 were consistently detected between EOI and 1 hr post infusion. Additional chemokines, including MIP-1α, MIP-1β, and IP-10 were also detected in some of the subjects. A significant increase in the neutrophil and monocyte counts was seen in the blood after infusion. Cellular analyses showed Imprime binding to neutrophils, monocytes, and subsets of DC (classical and inflammatory) 15-30 mins after the start of infusion. Additionally, 24 hrs after completion of Imprime administration, a population of non-classical monocytes (CD14/CD16 positive), which are known to have higher antigen presentation capability and thus express higher levels of the activation markers CD86, PD-L1, and HLA-DR, was observed. Importantly, these IPD responses were evident only in subjects with higher ABA levels. Collectively, these data provide the first evidence that, when dosed IV in healthy human subjects, Imprime elicits a constellation of innate immune activating events that are consistent with efficacy in preclinical tumor models. Importantly, these human data also provide the first evidence linking pre-treatment ABA levels and Imprime induced IPD changes, suggesting the plausibility of using pre-treatment ABA levels in the selection of patients most likely to benefit from Imprime-based therapy. Citation Format: Nadine C. Ottoson, Richard D. Huhn, Jamie Lowe, Ben Harrison, Jose Iglesias, Blaine Rathmann, Takashi Kangas, Lindsay R. Wurst, Xiaohong Qiu, Anissa Chan, Adria Bykowski Jonas, Kathryn Fraser, Richard M. Walsh, Katie Ertelt, Steven M. Leonardo, Ross Fulton, Keith Gorden, Mark A. Matson, Mark Uhlik, Jeremy Graff, Nandita Bose. Imprime PGG, an intravenously administered beta glucan PAMP activates the innate immune system: A phase I clinical study to evaluate immunopharmacodynamic responses [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B008.

Abstract A26: Imprime PGG improves the efficacy of carboplatin, paclitaxel, and cetuximab chemoimmunotherapy of advanced non-small cell lung cancer (NSCLC).

Imprime PGG is a yeast-derived beta 1,3/1,6 glucan that primes innate immune cells to kill monoclonal antibody (MAb)-targeted cancer cells via a mechanism dependent on complement receptor 3 (CR3). In humans, naturally occurring anti-beta glucan antibodies are required for binding of Imprime PGG to CR3 on immune cells. A quantitative assay has been developed to measure these antibodies in serum; subjects with levels conducive to binding are considered “biomarker positive” (BM+) and others “biomarker negative” (BM-). In a Phase 2 study, stage IIIb or IV NSCLC subjects received cetuximab (250 mg/m2 following initial 400 mg/m2 loading dose) without (Control, N=30) or with Imprime PGG 4mg/kg (Imprime, N=60) on Days 1, 8 and 15 of each 3-week treatment cycle; all subjects also received carboplatin (AUC 6) plus paclitaxel (200 mg/m2) on Day 2 of each cycle for the first 4 to 6 cycles. Maintenance treatment with cetuximab alone or with Imprime was continued in subjects achieving radiographic stable disease or tumor responses (RECIST 1.0). In the efficacy population comprised of all treated subjects who had evaluable baseline and post-baseline scans, median overall survival was 11.2 mo in the control group (N=26), 10.2 mo in the entire Imprime group (N=46) (HR 1.06, p=0.85 vs. control), 16.5 mo in the BM+ Imprime group (N=15) (HR 0.63, p=0.26 vs. control) and 9.1 mo in the BM- Imprime group (N=31) (HR 1.35, p=0.35 vs. control). Three-year survival was 0% in the control group, 7% in the entire Imprime group, 17% in the BM+ Imprime group and 0% in the BM- Imprime group. The objective response rate (ORR, all partial responses) was 23% in the control group, 48% in the entire Imprime group (p= 0.048 vs. control), 67% in the BM+ Imprime group (p=0.009 vs. control) and 39% in the BM- Imprime group (p=0.26 vs. control). Among subjects with squamous cell histology, 6 of 6 BM+ Imprime subjects had responses compared with 3 of 10 control subjects (p=0.01). Grade 3/4 adverse events occurred in 25 of 29 control subjects (86%) and 46 of 59 Imprime subjects (78%). All adverse events were consistent with toxicities attributable to the cytotoxic drugs or cetuximab. In summary, the addition of Imprime PGG to chemoimmunotherapy with carboplatin, paclitaxel and cetuximab resulted in improved outcomes in BM+ subjects with respect to increased ORR and extended survival compared to control subjects and had a good safety profile. Citation Format: Michael Thomas, Parvis Sadjadian, Jens Kollmeier, Zhonglin Hao, Myra Patchen, Jamie Lowe, Paulette Mattson, Richard D. Huhn, Nandita Bose, Mary Antonysamy, Michele Gargano, Keith Gordon, Folker Schneller. Imprime PGG improves the efficacy of carboplatin, paclitaxel, and cetuximab chemoimmunotherapy of advanced non-small cell lung cancer (NSCLC). [abstract]. In: Proceedings of the AACR-IASLC Joint Conference on Molecular Origins of Lung Cancer; 2014 Jan 6-9; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2014;20(2Suppl):Abstract nr A26.

1071PCHEMOIMMUNOTHERAPY OF ADVANCED NON-SMALL CELL LUNG CANCER (NSCLC) WITH IMPRIME PGG (IPGG) IN COMBINATION WITH CETUXIMAB, CARBOPLATIN AND PACLITAXEL–ANALYSIS OF SECONDARY ENDPOINTS OF A MULTICENTER, RANDOMIZED PHASE 2 TRIAL

ABSTRACT Aim: IPGG is a yeast-derived b-glucan that primes innate immune cells to kill monoclonal antibody-targeted cancer cells via complement receptor 3 (CR3). Subjects with anti-beta glucan antibodies (ABA) levels conducive to IPGG binding to CR3 are considered “biomarker positive” (BM+). We have previously reported significant improvements in objective responses with IPGG in combination with cetuximab, carboplatin and paclitaxel in patients (pts) with advanced NSCLC. Herein, we present the secondary endpoints of the clinical trial. Methods: Pts with Stage IV NSCLC received cetuximab (CET) 250 mg/m2 following initial 400 mg/m2 loading dose) without (Control, N = 30) or with IPGG 4mg/kg (IPGG, N = 60) on Days 1, 8 and 15 of each 3-week treatment cycle, and carboplatin (AUC 6) + paclitaxel (200 mg/m2) on Day 2 for the first 4 to 6 cycles. Pts achieving radiographic stable disease or tumor response (modified RECIST 1.0) received CET or CET/IPGG maintenance treatment. The primary endpoint was objective response rate. Secondary endpoints included disease control rate (DCR: CR + PR + SD), time to progression (TTP), overall survival (OS) and safety. Results: Best overall response (control vs IPGG) was PR in 23.1% vs 47.8% (p = 0.048), SD in 53.8% vs 30.4%, and PD in 23.1% vs 21.7%, respectively; DCR was 76.9% vs 78.3%, respectively (p = NS). ORR was 66.7% with IPGG in BM+ pts (p = 0.009 vs. Control) and 38.7% in the BM - group (p = NS vs. Control). Median TTP was 4.4 mo vs 4.3 mo respectively in the overall population and 5.6 mo in BM+ pts receiving IPGG (p = NS). OS was 11.3 mo vs 12.4 mo overall (p = NS), and 16.7 mo in BM+ pts vs. 9.4 mo in BM- pts receiving IPGG (p = 0.133). All subjects had at least one adverse event; grade III/IV adverse events occurred in 86.2% vs 78.0% of control vs. IPGG-treated pts. Conclusions: In patients with stage IV NSCLC receiving combination therapy with carboplatin, paclitaxel and CET, IPGG was well tolerated, improved objective responses and prolonged OS in BM+ pts. Disclosure: N. Bose, M.L. Patchen, J. Lowe, P. Mattson, M. Gargano, R.D. Huhn and A. Braun: Employee of Biothera, Inc.All other authors have declared no conflicts of interest.