Immunotherapeutic maintenance treatment with toll-like receptor 9 agonist lefitolimod in patients with extensive-stage small-cell lung cancer: results from the exploratory, controlled, randomized, international phase II IMPULSE study

Background

The immune surveillance reactivator lefitolimod (MGN1703), a DNA-based TLR9 agonist, might foster innate and adaptive immune response and thus improve immune-mediated control of residual cancer disease. The IMPULSE phase II study evaluated the efficacy and safety of lefitolimod as maintenance treatment in extensive-stage small-cell lung cancer (ES-SCLC) after objective response to first-line chemotherapy, an indication with a high unmet medical need and stagnant treatment improvement in the last decades.

Patients and methods

103 patients with ES-SCLC and objective tumor response (as per RECIST 1.1) following four cycles of platinum-based first-line induction therapy were randomized to receive either lefitolimod maintenance therapy or local standard of care at a ratio of 3 : 2 until progression or unacceptable toxicity.

Results

From 103 patients enrolled, 62 were randomized to lefitolimod, 41 to the control arm. Patient demographics and response patterns to first-line therapy were balanced. Lefitolimod exhibited a favorable safety profile and pharmacodynamic assessment confirmed the mode-of-action showing a clear activation of monocytes and production of interferon-gamma-induced protein 10 (IP-10). While in the intent-to-treat (ITT) population no relevant effect of lefitolimod on progression-free and overall survival (OS) could be observed, two predefined patient subgroups indicated promising results, favoring lefitolimod with respect to OS: in patients with a low frequency of activated CD86⁺ B cells (hazard ratio, HR 0.53, 95% CI: 0.26–1.08; n = 38 of 88 analyzed) and in patients with reported chronic obstructive pulmonary disease (COPD) (HR 0.48, 95% CI: 0.20–1.17, n = 25 of 103).

Conclusions

The IMPULSE study showed no relevant effect of lefitolimod on the main efficacy end point OS in the ITT, but (1) the expected pharmacodynamic response to lefitolimod, (2) positive OS efficacy signals in two predefined subgroups and (3) a favorable safety profile. These data support further exploration of lefitolimod in SCLC.

Beneficial modulation of the tumor microenvironment and generation of anti-tumor responses by TLR9 agonist lefitolimod alone and in combination with checkpoint inhibitors

Activation of Toll-like receptor 9 (TLR9) is known to foster innate and adaptive immune responses and thus improve immune-mediated control of malignant disease. Lefitolimod is a potent TLR9 agonist without chemical modification developed for immunotherapeutic strategies. Modulation of the tumor microenvironment (TME) is a crucial requirement for the response to various immunotherapies: Immunogenic (“hot”) tumors, characterized by their T cell-infiltrated TME, respond better compared to non-immunogenic (“cold”) tumors. It has been speculated that the mode-of-action of lefitolimod provides the necessary signals for activation of immune cells, their differentiation into anti-tumor effector cells and their recruitment into the TME. We investigated the effect of lefitolimod on TME, and its potency to induce synergistic anti-tumor effects when combined with immune checkpoint inhibitory antibodies (CPI) in a murine model. Indeed, we could show that treatment with single-agent lefitolimod beneficially modulated the TME, via infiltration of activated CD8+ cells and a shift in the macrophage population toward M1 phenotype. The result was a pronounced anti-tumor effect correlated with the magnitude of infiltrated immune cells and tumor-specific T cell responses. In line with this, lefitolimod led to persistent anti-tumor memory in the EMT-6 model after tumor re-challenge. This was accompanied by an increase of tumor-specific T cell responses and cross-reactivity against different tumor cells. Lefitolimod clearly augmented the limited anti-tumor effect of the CPI anti-PD1 in an A20 and anti-PD-L1 in a CT26 model. These properties of potent immune surveillance reactivation render lefitolimod an ideal candidate as therapeutic agent for immuno-oncology, e.g. improving CPI strategies.

TLR9 agonist MGN1703 enhances B cell differentiation and function in lymph nodes

Background

TLR9 agonists are being developed as immunotherapy against malignancies and infections. TLR9 is primarily expressed in B cells and plasmacytoid dendritic cells (pDCs). TLR9 signalling may be critically important for B cell activity in lymph nodes but little is known about the in vivo impact of TLR9 agonism on human lymph node B cells. As a pre-defined sub-study within our clinical trial investigating TLR9 agonist MGN1703 (lefitolimod) treatment in the context of developing HIV cure strategies (NCT02443935), we assessed TLR9 agonist-mediated effects in lymph nodes.

Methods

Participants received MGN1703 for 24 weeks concurrent with antiretroviral therapy. Seven participants completed the sub-study including lymph node resection at baseline and after 24 weeks of treatment. A variety of tissue-based immunologic and virologic parameters were assessed.

Findings

MGN1703 dosing increased B cell differentiation; activated pDCs, NK cells, and T cells; and induced a robust interferon response in lymph nodes. Expression of Activation-Induced cytidine Deaminase, an essential regulator of B cell diversification and somatic hypermutation, was highly elevated. During MGN1703 treatment IgG production increased and antibody glycosylation patterns were changed.

Interpretation

Our data present novel evidence that the TLR9 agonist MGN1703 modulates human lymph node B cells in vivo. These findings warrant further considerations in the development of TLR9 agonists as immunotherapy against cancers and infectious diseases.

Fund

This work was supported by Aarhus University Research Foundation, the Danish Council for Independent Research and the NovoNordisk Foundation. Mologen AG provided study drug free of charge.

Abstract 5557: EnanDIM, a family of potent enantiomeric TLR9 agonists, modulate the tumor microenvironment and show single-agent antitumor effects in various syngeneic murine models

Introduction: TLR9 agonists, being recognized via non-methylated CG-motifs, target the Toll-like receptor 9 (TLR9). This way, they activate the innate and the adaptive immune system. Two different families of TLR9 agonists are currently used in preclinical and clinical studies: Covalently-closed dumbbell-shaped DNA molecules with natural phosphodiester backbone which are protected from degradation by their conformation (dSLIM®) and single-stranded, oligodeoxynucleotides (CpG-ODN) commonly stabilized by phosphorothioates (PTO). However, chemical PTO-modifications have resulted in off-target effects and an unfavorable risk-to-benefit ratio in clinical trials. EnanDIM® are a new family of TLR9 agonists. EnanDIM® molecules consist of linear single-stranded ODN. Protection against exonucleases is achieved through L-deoxyribose nucleotides instead of the naturally occurring D-deoxyribose nucleotides at their 3'-ends. EnanDIM® lead to pronounced induction of cyto- and chemokines, like IFN-alpha and IP-10, as well as broad activation of immune cells, like monocytes, NK cells and dendritic cells, within PBMC. Therefore, EnanDIM® were evaluated in various syngeneic murine tumor models for their anti-tumor effects.

Methods: Mice were subcutaneously inoculated with either CT26 (colon carcinoma), MC38 (colon carcinoma), EMT-6 (breast cancer), B16F10 (melanoma) or A20 (lymphoma) cells for solid tumor growth. EnanDIM® (250 µg per dose, intratumoral) was used to treat established tumors. In addition, the capability of EnanDIM® to modulate the tumor micro-environment (TME) was analyzed via immunohistochemistry in a syngeneic tumor model.

Results: Mice in all models showed clear reduction in tumor growth (TGI: 53 to 85%) and, therefore, an increased survival (p ≤0.001, logrank). Notably, in the EMT-6 tumor model 8/10 mice showed complete tumor regression after EnanDIM® injection. Those 8 mice rejected EMT-6 tumor cells in a subsequent re-challenge study, indicating a sustained immune memory against the tumor, which was in contrast to age-matched naïve mice. When analyzing the TME of mice from the CT26 model an increased immune cell infiltration into the tumor by CD3+, especially CD8+ T cells was detected, showing the ability of EnanDIM® to beneficially modulate the TME.

Conclusions: The enantiomeric TLR9 agonists EnanDIM® show promising anti-tumor effects in a variety of syngeneic murine tumor models and a beneficial modulation of the TME towards an increase of anti-tumor effector cells. These data provide the basis for a further development of EnanDIM® in cancer.

Citation Format: Barbara Volz, Kerstin Kapp, Detlef Oswald, Burghardt Wittig, Manuel Schmidt. EnanDIM, a family of potent enantiomeric TLR9 agonists, modulate the tumor microenvironment and show single-agent antitumor effects in various syngeneic murine models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5557.

Short-Course Toll-Like Receptor 9 Agonist Treatment Impacts Innate Immunity and Plasma Viremia in Individuals With Human Immunodeficiency Virus Infection

Background.

Treatment with latency reversing agents (LRAs) enhances human immunodeficiency virus type 1 (HIV-1) transcription in vivo but leads to only modest reductions in the size of the reservoir, possibly due to insufficient immune-mediated elimination of infected cells. We hypothesized that a single drug molecule-a novel Toll-like receptor 9 (TLR9) agonist, MGN1703-could function as an enhancer of innate immunity and an LRA in vivo.

Methods.

We conducted a single-arm, open-label study in which 15 virologically suppressed HIV-1-infected individuals on antiretroviral therapy received 60 mg MGN1703 subcutaneously twice weekly for 4 weeks. We characterized plasmacytoid dendritic cell, natural killer (NK), and T-cell activation using flow cytometry on baseline and after 4 weeks of treatment. HIV-1 transcription was quantified by measuring plasma HIV-1 RNA during MGN1703 administration.

Results.

In accordance with the cell type-specific expression of TLR9, MGN1703 treatment led to pronounced activation of plasmacytoid dendritic cells and substantial increases in plasma interferon-α2 levels (P < .0001). Consistently, transcription of interferon-stimulated genes (eg, OAS1, ISG15, Mx1; each P < .0001) were upregulated in CD4+ T cells as demonstrated by RNA sequencing. Further, proportions of activated cytotoxic NK cells and CD8+ T cells increased significantly during MGN1703 dosing, suggesting an enhancement of cellular immune responses. In 6 of 15 participants, plasma HIV-1 RNA increased from <20 copies/mL to >1500 copies/mL (range, 21-1571 copies/mL) during treatment.

Conclusions.

TLR9 agonist treatment in HIV infection has a dual potential by increasing HIV-1 transcription and enhancing cytotoxic NK cell activation, both of which are key outcomes in HIV-1 eradication therapy.

Clinical Trials Registration.

NCT02443935.

Modulation of T cell and macrophage tumor infiltration by the TLR9 agonist lefitolimod in a murine model of colorectal cancer

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Background: The use of TLR9 agonists for immunotherapeutic approaches is supported by preclinical and ongoing clinical studies. Lefitolimod, a covalently-closed dumbbell-shaped DNA construct, is an immune surveillance reactivator which broadly activates cells of the innate and adaptive immune system. The conversion of non-immunogenic (cold) tumors into immunogenic (hot) tumors, characterized by their T-cell infiltration, is a pre-requisite for response to immunotherapies. By its mode-of-action lefitolimod likely provides the necessary signals for activation of immune cells and their differentiation into anti-tumor effector cells as well as their recruitment to the tumor microenvironment (TME). Methods: To support the further clinical development of lefitolimod in mCRC, the syngeneic colon carcinoma model CT26 was used to evaluate anti-tumoral efficacy of lefitolimod and its modulation of the TME. The phenotype of T cells and macrophages present within tumor-infiltrating immune cells were analyzed by flow cytometry. Their localization within the tumor was investigated by immunohistochemistry. Results: Intratumoral injection of single-agent lefitolimod in the CT26 model resulted in reduced tumor growth. This was accompanied by an increased infiltration of T cells, in particular CD8+ T cells, into the tumor center. The CD8+ T cells were activated and showed an up-regulation of the cytolytic effector Granzyme B. Correspondingly, the ratio of activated CD8+ T cells with cytolytic function to regulatory T cells was increased by lefitolimod. Moreover, lefitolimod led to the recruitment of macrophages into the tumor and, importantly, an increase of M1 macrophages and a decrease of M2 macrophages inside the TME. Conclusions: Lefitolimod treatment resulted in modulation of the TME towards an increase of effector cells with anti-tumoral functions like cytotoxic CD8+ T cells and M1-type macrophages as well as a decrease of pro-tumoral M2-type macrophages. Therefore, lefitolimod provides the essential requirements for clinical response to immunotherapeutic drugs like checkpoint inhibitors. This predestines lefitolimod as combination partner in immuno-oncological trials.

Abstract 2622: Two new TLR9 agonists for cancer immunotherapy: Combination with checkpoint inhibitors

Introduction

TLR9 agonists are developed as anti-cancer therapies based on their broad activation of the innate and adaptive immune system. Single-stranded oligodeoxynucleotides (ODN) containing non-methylated CG-motifs activate TLR9. Previously, chemical modification was used to prevent their degradation by exonucleases. To avoid the off-target effects observed with chemical modifications, new TLR9 agonists containing only natural DNA were stabilized by structural components. The dSLIM® family of TLR9 agonists is protected from exonucleolytic degradation by its covalently-closed dumbbell-shaped structure. It contains an immunomodulatory sequence with CG-motifs in its loops. The linear single-stranded EnanDIM® family of TLR9 agonists utilizes L-deoxyribonucleotides (natural enantiomers of D-deoxyribonucleotides) at their 3’-ends to prevent degradation. Since the mode-of-action of TLR9 agonists starts upstream of the targets of checkpoint inhibitors anti-PD-1/anti-PD-L1 a combinatory approach may support synergistic immune activation and thus enhanced anti-tumor effects.

Methods

The impact of dSLIM2006 and EnanDIM-1 on T cell responses was analyzed employing an in vitro assay using human peripheral blood mononuclear cells (PBMC). PBMC were treated with peptides selected from HLA class I-restricted T-cell epitopes of recall-antigens (CMV, EBV, Flu = CEF), TLR9 agonists and anti-PD-1 as checkpoint inhibitor. In addition, in vivo studies were used to investigate the anti-tumor effect of dSLIM2006 and EnanDIM-1 in combination with anti-PD-1 in a syngeneic murine CT26 tumor model.

Results

The IFN-gamma secretion of human PBMC after stimulation of CEF peptides was roughly 5-fold increased by EnanDIM-1 and dSLIM2006, whereas treatment with anti-PD-1 resulted barely in a two-fold increase. The combination of the TLR9 agonists and anti-PD-1 further enforced IFN-gamma secretion by about 7-fold. In the murine colon cancer model CT26 the subcutaneous injection of EnanDIM-1 or intraperitoneal injection of anti-PD-1 had a moderate effect on the tumor growth when used in monotherapy (28.3% or 57.0% tumor growth inhibition, TGI). Notably, a combination of EnanDIM-1 and anti-PD-1 further reduced tumor growth (74.7% TGI). Intratumoral injection of dSLIM2006 in combination with intraperitoneal injection of anti-PD-1 reduced tumor growth (54.2% TGI) whereas the single components had more limited effects (dSLIM2006: 18.7%, anti-PD-1: no inhibition). Combined treatment with TLR9 agonists and anti-PD-1 prolonged survival of the mice in comparison to single treatments.

Conclusions

The TLR9 agonists and immune surveillance reactivators (ISR) EnanDIM-1 and dSLIM2006 enhance T cell responses and anti-tumor effects of the anti-PD-1 checkpoint inhibitor. These data show their promising potential not only for monotherapeutic but also combinatory approaches.

Citation Format: Kerstin Kapp, Barbara Volz, Detlef Oswald, Burghardt Wittig, Manuel Schmidt. Two new TLR9 agonists for cancer immunotherapy: Combination with checkpoint inhibitors [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 2622. doi:10.1158/1538-7445.AM2017-2622

TLR9 agonist lefitolimod to improve antitumor effect of checkpoint inhibitors in vivo

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Background: TLR9 agonists are potent activators of the immune system via induction of cellular and humoral responses. Preclinical and ongoing clinical studies support the use of TLR9 agonists for immunotherapeutic approaches. Lefitolimod/MGN1703 is a covalently-closed dumbbell-like immune surveillance reactivator (ISR) with a broad immunomodulatory potential. Due to promising data from a phase 2 trial (IMPACT) as maintenance therapy after first-line chemotherapy in mCRC patients lefitolimod is recently evaluated in a phase 3 trial in mCRC patients (IMPALA). Furthermore, lefitolimod is currently investigated in a phase 2 trial in SCLC patients (IMPULSE) and in a phase 1 / 2 trial in HIV patients (TEACH). Methods: It was shown that lefitolimod reduces tumor growth in several murine tumor models. Since the mode-of-action of lefitolimod starts upstream of the initiation points of checkpoint inhibitors like anti-CTLA-4 or anti-PD-1/anti-PD-L1 a combinatory approach may result in an enhanced anti-tumor effect. Therefore, two syngeneic murine models were used – a colon carcinoma CT26 and a lymphoma A20 model – for evaluation of the anti-tumor effect in vivo. Results: In the CT26 model treatment with anti-PD-L1 (i.p.) had no effect on the tumor growth, whereas addition of lefitolimod (s.c.) to anti-PD-L1 led to an anti-tumor effect (tumor growth inhibition, TGI 48%) which consequently resulted in prolonged survival of the mice. This combinatory effect was even more pronounced in the A20 model where treatment with anti-PD-1 (i.p.) alone had a moderate anti-tumor effect which was vastly increased by the combination (TGI – anti-PD-1: 46%, anti-PD-1/lefitolimod 99%). Conclusions: In conclusion, we showed that lefitolimod, a member of dSLIM® family of TLR9 agonists and an ISR, can enhance the limited anti-tumor effects of checkpoint inhibitors in pilot studies in murine colon carcinoma and lymphoma tumor models in vivo. These data show the promising potential for the combination with checkpoint inhibitors. Notably, a clinical trial in cooperation with MD Anderson evaluating the benefit of lefitolimod in combination with ipilimumab is currently ongoing.

Combination of TLR9 agonists EnanDIM with checkpoint inhibitors for cancer immunotherapy

134

Background: TLR9 agonists have shown anti-tumor effects by modulating the innate and adaptive immune system. Ongoing clinical studies support the use of TLR9 agonists for immunotherapeutic approaches. The new family of TLR9 agonists, EnanDIM, consists of linear single-stranded ODN synthesized using L-deoxyribonucleotides (natural enantiomers of D-deoxyribonucleotides) at their 3’-ends to prevent degradation. Therefore, EnanDIM does not own the off-target effects of PTO-modified CpG-ODN. Methods: EnanDIM with varying nucleotid sequences were compared for IFN-alpha response from human peripheral blood mononuclear cells and those molecules inducing the stronges response were selected. A maximum feasible dose (MFD) approach was employed to evaluate their acute toxicity and immunomodulatory properties. In addition, a combinatory approach with aPD-1 was evaluated in an syngeneic colon carcinoma CT26 mouse tumor model. Results: EnanDIM581 and EnanDIM532 were selected due to their pronounced activation of the IFN-alpha pathway in vitro. Safety assessments throughout and a gross necropsy at the end of the study revealed no signs of toxicity despite extremely high doses (300 - 1700 mg/kg). Dose-dependent increase of IP-10 levels in serum was observed between 6 and 24 hours after injection. In the colon carcinoma CT26 model subcutaneous injection of EnanDIM532 and intraperitoneal injection of aPD-1 had a moderate effect on the tumor growth when used in monotherapy (28.3% and 57.0% tumor growth inhibition, TGI). Notably, a combination of EnanDIM532 and aPD-1 further reduced tumor growth (74.7% TGI) and thus prolonged survival of the mice. Conclusions: In conclusion, EnanDIM, a new family of TLR9 agonists and immune surveillance reactivators (ISR), broadly activates the immune system, shows no toxicity in an MFD study and enhances the anti-tumor effects of the aPD-1 checkpoint inhibitor in a pilot study of a murine colon carcinoma tumor model. These data show the promising potential of EnanDIM not only for monotherapeutic but also combinatory approaches.

Combination of TLR9 agonist lefitolimod/MGN1703 with checkpoint inhibitors for cancer immunotherapy

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Background: TLR9 agonists are potent activators of the immune system via induction of cellular and humoral responses. Preclinical and ongoing clinical studies support the use of TLR9 agonists for immunotherapeutic approaches. Lefitolimod/MGN1703 is a covalently-closed dumbbell-like immune surveillance reactivator (ISR) with a broad immunomodulatory potential. After promising data from a phase II trial (IMPACT) as maintenance therapy after first-line induction chemotherapy in patients with metastatic colorectal cancer lefitolimod is recently evaluated in a phase III trial in mCRC patients (IMPALA). Methods: It was previously shown that lefitolimod can reduce tumor growth in several murine tumor models. Since the mode-of-action of lefitolimod starts upstream of the initiation points of checkpoint inhibitors aCTLA-4 or aPD-1/aPD-L1 a combinatory approach may result in an enhanced anti-tumor effect. Therefore, we employed two syngeneic murine tumor models: One with s.c. inoculation of CT26 cells and another with s.c. A20 cell challenge. Multiple doses of lefitolimod were injected s.c. or i.tu. Results: In the colon carcinoma CT26 model i.p. injection of aPD-L1 had no effect on the tumor growth, whereas peritumoral injection of lefitolimod led to a slowed tumor growth. The tumor growth was further inhibited by the combination (tumor growth inhibition, TGI - aPD-L1: no, lefitolimod: 28%, combination: 48%) resulting in prolonged survival of the mice. This combinatory effect was even more pronounced in the lymphoma A20 model: Injections of anti-PD-1 (i.p.) or lefitolimod (i.tu.) alone had a moderate anti-tumor effect which was vastly increased by the combination (TGI - aPD-1: 46%, lefitolimod: 50%, combination: 99%). Conclusions: In conclusion, we showed that lefitolimod, a member of dSLIM family of TLR9 agonists and an ISR, can enhance the limited anti-tumor effects of checkpoint inhibitors in pilot studies in murine colon carcinoma and lymphoma tumor models in vivo. These data show the promising potential for the combination with checkpoint inhibitors. In fact, a clinical trial in cooperation with MD Anderson evaluating the benefit of lefitolimod in combination with ipilimumab is currently ongoing.

Abstract B067: Preclinical data of novel enantiomeric oligonucleotides for cancer immunotherapy: The TLR9 agonist EnanDIM

Introduction: The use of TLR9 agonists as immunomodulators is supported by preclinical and clinical studies, showing their anti-tumor effect by enhancing both cellular and humoral responses. Two different families of DNA molecules containing non-methylated CG-motifs for TLR9 activation have been established so far: Dumbbell-shaped dSLIM molecules are protected against exonucleolytic degradation by their covalently-closed, natural phosphodiester (PO) backbone. In contrast, single-stranded, oligodeoxynucleotides (CpG-ODN) are most commonly chemically-stabilized by phosphorothioates (PTO) in their phosphate moieties. However, PTO modifications produce off-target effects in immune cell populations and have resulted in an unfavorable risk-to-benefit ratio.

Methods: Linear single-stranded ODN were synthesized using L-deoxyribonucleotides at their 3'-ends, which are the natural enantiomers of D-deoxyribonucleotides, to ensure protection against exonucleases and avoid the off-target effects of PTO-modified CpG-ODN. The vast majority of deoxyribose in present organisms are D-deoxyribose, thus co-evolved nucleases are blind for L-deoxyribose thereby leaving L-protected ODN intact. Using high secretion of IFN-alpha and IP-10 from human peripheral blood mononuclear cells as marker, we selected nucleotide sequences of such L-protected, CG-motif containing, single-stranded ODN, EnanDIM. First, we employed a maximum feasible dose (MFD) approach. Mice received subcutaneous injection of single doses of 10 to 50 mg EnanDIM to evaluate its acute toxicity. Immunomodulatory properties were evaluated as well. Finally, a pilot tumor model in mice was used to investigate the anti-tumor effect of EnanDIM.

Results: EnanDIM581 and EnanDIM532 were selected due to their pronounced activation of immune cells (e.g. monocytes, NK cells and plasmacytoid dendritic cells) and their prominent induction of IFN-alpha and IP-10 secretion in vitro. EnanDIM744, comprising EnanDIM581 with additional 5'-end L-nucleotide protection and exhibiting an activation pattern similar to EnanDIM581, was also used for MFD studies. Safety assessments were performed throughout the study period and no mortality, clinical signs and body weight changes were observed, despite the extremely high doses of app. 300 to 1700 mg/kg. A gross necropsy consisting of a macroscopic organ evaluation at day 15 revealed also no toxicity. Dose-dependent increase of IP-10 levels in serum was observed between 6 and 24 hours after injection (maximum at 6h) but after 15 days IP-10 levels were undetectable, confirming that L-nucleotides in EnanDIM do not change the kinetic profile known from other DNA-based TLR9 agonists. Preliminary data from a murine tumor model suggest that multiple doses of EnanDIM can reduce tumor growth.

Conclusions: EnanDIM, a new family of TLR9 agonists, broadly activates the immune system in vitro and in vivo. While maximal feasible doses of EnanDIM resulted in no signs of toxicity, an indication of reduced tumor growth was observed in a murine tumor model in vivo. Therefore EnanDIM has the potential for clinical development in the treatment of cancer.

Citation Format: Kerstin Kapp, Barbara Volz, Detlef Oswald, Burghardt Wittig, Manuel Schmidt. Preclinical data of novel enantiomeric oligonucleotides for cancer immunotherapy: The TLR9 agonist EnanDIM [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 B067.

Distinct immunological activation profiles of dSLIM® and ProMune® depend on their different structural context

INTRODUCTION

DNA-based TLR9 agonists are potent activators of the immune system. ProMune® and dSLIM® belong to different families of TLR9 agonists and both have been established as cancer immunotherapeutics in clinical proof-of-concept studies. Unfortunately, ProMune® failed in pivotal oncological trials. dSLIM®, the active ingredient of Lefitolimod (MGN1703), successfully finished a double-blinded, placebo-controlled phase II study in patients with advanced colorectal cancer, exhibiting improved progression-free survival and durable disease control.

METHODS

To explain the different systemic efficacies of dSLIM® and ProMune®, both TLR9 agonists and chimeric molecules thereof are analyzed side-by-side in a panel of in vitro assays for immune activation.

RESULTS AND CONCLUSIONS

Indeed, dSLIM® exposure results in an IFN-α dependent broad activation of immune cells whereas ProMune® strongly stimulates B cells. Moreover, all functional effects of dSLIM® strictly depend on the presence of CG-motifs within its dumbbell-shaped, covalently closed structural context. Conversely, several immunological effects of ProMune® like IL-8 secretion are independent of CG-motifs and could be ascribed to the phosphorothioate-modifications of its DNA backbone, which may have caused the side effects of ProMune® in clinical trials. Finally, we showed that the implementation of ProMune® (ODN2006) base sequence into the characteristic dSLIM® dumbbell form resulted in dSLIM2006 with all beneficial effects for immunostimulation combined from both TLR9 classes without any CG-independent effects.

Abstract A035: Pharmacokinetics and pharmacodynamics of the immunotherapeutic TLR-9 agonist MGN1703 – conclusions by comparison of data from clinical trials with healthy volunteers and cancer patients

Background: The synthetic DNA-based immunomodulator MGN1703 is a member of the new dSLIM® family of TLR-9 agonists, comprising covalently closed dumbbell-like DNA molecules which consist entirely of natural DNA with two single-stranded CG-containing loops separated by a double-stranded stem. MGN1703 exerts its function by activating the innate and both arms of the adaptive immune system. MGN1703 has already shown a good safety profile and benefit for patients compared to placebo in maintenance therapy of metastatic colorectal carcinoma (mCRC) after fist-line induction therapy in a phase 2 clinical trial (MGN1703-C02, IMPACT).

Methods: Following preclinical studies in mice and monkeys, a human clinical program was performed, including a phase 1 trial (MGN1703-C01), on a variety of solid tumors, and the double-blinded, placebo-controlled phase 2 IMPACT trial with mCRC patients. Additionally, a single dose crossover, placebo-controlled phase 1 cardiac safety trial, MGN1703-C04, was conducted to assess cardiac and general safety, pharmacokinetics (PK) and pharmacodynamics (PD) in healthy volunteers (HV). Fourteen HV were randomized and 13 subjects completed the study receiving a subcutaneous dose of 60 mg MGN1703 during one treatment period and a single dose of placebo during the other.

Results: After single dose administration of MGN1703 standard PK parameters were determined in the MGN1703-C04 trial: mean Tmax (14h), AUC0-t (5000 ng•hr/mL) and shape of the curve of MGN1703 concentration in serum. These were similar to single dose data obtained from cancer patients, where a mean Tmax of 10h and a mean AUC0-t of 5340 ng•hr/mL have been observed. Notably, multiple doses resulted in similar levels in serum of cancer patients, without accumulation of MGN1703.

PD was mainly evaluated by analyzing levels of the chemokine IP-10 in serum of the HV as an equivalent of innate immune activation. Elevated IP-10 levels in the serum of HV were shown peaking at 24-48 hours after dosing with MGN1703. This is clearly in line with expected time frame of immune activation subsequent to MGN1703 appearance in the serum of the HV. Timing and levels of IP-10 elevation are in keeping with data from the peripheral blood of cancer patients, where in addition to IP-10 also the subsequent activation of innate immune cells – especially the up-regulation of CD169 on monocytes – as a consequence of MGN1703 administration was observed.

Conclusions: The data show obvious similarities between healthy volunteers and cancer patients with respect to PK and PD and also confirm the appearance of the appropriate immunomodulatory signature downstream of MGN1703 appearance. This supports the twice weekly application scheme of current immunotherapy studies with MGN1703, e.g. the ongoing phase 3 IMPALA trial in mCRC patients. Further data will allow for evaluation of a possible association with clinical parameters in cancer patients.

Citation Format: Manuel Schmidt, Kerstin Kapp, Detlef Oswald, Matthias Schroff, Burghardt Wittig, Alfredo Zurlo. Pharmacokinetics and pharmacodynamics of the immunotherapeutic TLR-9 agonist MGN1703 – conclusions by comparison of data from clinical trials with healthy volunteers and cancer patients. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A035.

Abstract A034: Immune responses against tumor associated antigens are induced by treatment with the cell-based tumor vaccine MGN1601 in patients with renal cell carcinoma

Background: In a first in men, proof-of-principle, multi-center, open-label, single-arm, non-randomized phase 1/2 clinical ASET trial (ClinicalTrials.gov: NCT01265368; EudraCT No.: 2009-016853-16) in patients with advanced RCC the tumor vaccine MGN1601 has shown a good safety profile and improved overall survival in the per-protocol (PP) treated patient population. MGN1601 is a cell-based tumor vaccine consisting of two active pharmaceutical ingredients: Allogeneic (human) cells originating from renal cell carcinoma were gene-modified with four different MIDGE vectors encoding IL-7, GM-CSF, CD80 and CD154. These vaccine cells were combined with the synthetic DNA-based immunomodulator dSLIM®, a potent TLR-9 agonist.

Methods: The tumor vaccine MGN1601 – each dose consists of 107 vaccine cells and 5 mg dSLIM® – was administered 8 times over 12 weeks with 3 weekly and 5 bi-weekly administrations (PP population) in the ASET trial. Specific humoral immune responses in sera from patients before and after treatment with MGN1601 against a natural set of 17 known tumor associated antigens (TAA) expressed by the vaccine cells were evaluated ex-vivo in a translational research program using peptide arrays. On the array each TAA was represented by peptides of 15 amino acids length with an overlap of 13 amino acids.

Results: Nineteen heavily pre-treated patients with advanced RCC have been included into the trial. In the PP population – comprising 10 of these 19 patients – the humoral immune response against TAA expressed on vaccine cells was evaluated. Within each antigen subsets of overlapping peptides were recognized by patient's sera with an abundant or clearly increased intensity after MGN1601 treatment indicating favoured immunogenic regions within a TAA for an individual immune response. Such sets of peptides were identified within each antigen showing individual responses by sera from 2 to eight patients. Remarkably, some of these overlapping peptides were recognized by sera of more than one patient (“shared immunogenic regions”): In particular, 50 to 70 % of treated patients shared response to immunogenic regions within Survivin, Stromelysin, c-Myc, Histone H1.2 and G1/S-specific Cyclin-D1 indicating their comprehensive immunogenic potential. Within other TAA (e.g. p53, telomerase) shared immune responses to peptides were observed at lower rates (20 to 40% of patients), whereas for some of the antigens (e.g. MUC1, Her2/neu) only individual immune responses to the peptides were identified.

Conclusions: The humoral immune response – assessed in patients treated with the tumor vaccine MGN1601 – revealed overlapping peptides within various TAA that induced an immune response shared by up to 7 of 10 patients, indicating comprehensive immunogenic regions within those TAA and their potential use as vaccine epitopes. The specific evaluation of immune response to those TAA remains to further studies.

Citation Format: Manuel Schmidt, Barbara Volz, Kerstin Kapp, Viktor Gruenwald, Matthias Schroff, Burghardt Wittig. Immune responses against tumor associated antigens are induced by treatment with the cell-based tumor vaccine MGN1601 in patients with renal cell carcinoma. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A034.

Abstract B61: Exploratory analyses of the randomized phase 2 IMPACT study: Patients with response to prior induction chemotherapy have improved outcome when treated with the TLR-9 agonist MGN1703

Background: The international randomized (2:1) double-blind placebo-controlled phase 2 IMPACT trial recruited patients with metastatic colorectal cancer (mCRC) and disease control after induction with 1st-line chemotherapy +/- bevacizumab. The trial aimed to assess the clinical efficacy, safety, and immunological effects of the immunomodulator MGN1703, a potent Toll-Like Receptor 9 (TLR9) agonist, given at the dose of 60 mg subcutaneously twice weekly as switch maintenance after 4.5 to 6 months of induction therapy.

Methods: After randomization of 59 patients (43 MGN1703, 16 placebo) the trial was prematurely closed. The final analysis showed superiority of MGN1703 over placebo with hazard ratios (HR) for the primary endpoint PFS on maintenance of 0.55 (p=0.041) and 0.56 (p=0.070) by local investigator assessment or independent radiological review, respectively. Some delayed and long term responses were observed, 3 still ongoing in excess of 36 months. Exploratory PFS analyses of pretreatment characteristics identified patients with objective response (HR=0.39, p=0.0051), normalized CEA (HR=0.07, p&lt;0.0001), and the presence of activated NKT-cells (CD3+/CD56+/CD69+) (HR=0.26, p=0.0017) at the end of induction chemotherapy to benefit the most from maintenance with MGN1703. Since PFS is not considered the best endpoint to assess the benefit of immunotherapies, we analyzed the impact of these factors on the secondary endpoint overall survival (OS).

Results: Despite a median follow up of 17.7 months at the time of final study analysis, the OS data were not mature with only 35% and 50% of patients in the MGN1703 arm and placebo arm with an event, respectively. The power of the following OS analyses is therefore limited and will require confirmation when a large majority of events has been observed. The HR for the whole study ITT population was 0.63 (median 22.6 vs. 15.1 months for MGN1703 vs. placebo; p=NS). The subgroup of patients who were randomized into the study after achieving a RECIST response to prior induction therapy had HR of 0.40 (median 24.5 vs. 15.1 months; p=NS). Patients randomized in the study with stable disease had instead no benefit (HR 1.57; p=NS). The HR for OS of patients with presence of activated NKT cells and normalized CEA level after induction therapy was 0.43 and 0.69, respectively. Overall these results appear in line with the evidence from PFS subgroup analyses suggesting that responders may benefit the most from switch maintenance treatment with MGN1703. Recent literature provides a rationale for such finding, as a large series showed that presence of high density of lymphocyte infiltration in CRC metastases strongly predicts responses to chemotherapy (Halama et al, Cancer Res 2011; 71:5670-5677). A good response to chemotherapy may thus be a surrogate marker for increased immunogenicity of the tumor and allow identifying patients with an immune system that may be able to control tumor progression when broadly activated by MGN1703. Based on this hypothesis, the phase 3 IMPALA study has recently started recruitment in several European countries. Patients who achieved an objective response to their 1st-line induction therapy for mCRC are randomized to either continue local standard treatment or start switch maintenance with MGN1703. CEA and activated NKT values at baseline are stratification factors and will be also assessed prospectively.

Conclusions: The exploratory PFS and OS subgroup data from the IMPACT study support the hypothesis that is possible to identify patients more likely to benefit from an immunomodulatory treatment following active induction chemotherapy. This information has been used to design the phase 3 IMPALA study currently recruiting patients.

Citation Format: Werner Scheithauer, Jorge Riera-Knorrenschild, Hans-Georg Kopp, Frank Mayer, Hendrik Kroening, Dieter Nitsche, Jan Kuhlmann, Reinhard Ziebermayr, Johannes Andel, Dirk Arnold, Alfredo Zurlo, Burghardt Wittig, Hans-Joachim Schmoll. Exploratory analyses of the randomized phase 2 IMPACT study: Patients with response to prior induction chemotherapy have improved outcome when treated with the TLR-9 agonist MGN1703. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B61.

Immune response of healthy horses to DNA constructs formulated with a cationic lipid transfection reagent

Background

Deoxyribonucleic acid (DNA) vaccines are used for experimental immunotherapy of equine melanoma. The injection of complexed linear DNA encoding interleukin (IL)-12/IL-18 induced partial tumour remission in a clinical study including 27 grey horses. To date, the detailed mechanism of the anti-tumour effect of this treatment is unknown.

Results

In the present study, the clinical and cellular responses of 24 healthy horses were monitored over 72 h after simultaneous intradermal and intramuscular application of equine IL-12/IL-18 DNA (complexed with a transfection reagent) or comparative substances (transfection reagent only, nonsense DNA, nonsense DNA depleted of CG).

Although the strongest effect was observed in horses treated with expressing DNA, horses in all groups treated with DNA showed systemic responses. In these horses treated with DNA, rectal temperatures were elevated after treatment and serum amyloid A increased. Total leukocyte and neutrophil counts increased, while lymphocyte numbers decreased. The secretion of tumour necrosis factor alpha (TNFα) and interferon gamma (IFNγ) from peripheral mononuclear blood cells ex vivo increased after treatments with DNA, while IL-10 secretion decreased. Horses treated with DNA had significantly higher myeloid cell numbers and chemokine (C-X-C motif) ligand (CXCL)-10 expression in skin samples at the intradermal injection sites compared to horses treated with transfection reagent only, suggesting an inflammatory response to DNA treatment.

In horses treated with expressing DNA, however, local CXCL-10 expression was highest and immunohistochemistry revealed more intradermal IL-12-positive cells when compared to the other treatment groups.

In contrast to non-grey horses, grey horses showed fewer effects of DNA treatments on blood lymphocyte counts, TNFα secretion and myeloid cell infiltration in the dermis.

Conclusion

Treatment with complexed linear DNA constructs induced an inflammatory response independent of the coding sequence and of CG motif content. Expressing IL-12/IL-18 DNA locally induces expression of the downstream mediator CXCL-10.

The grey horses included appeared to display an attenuated immune response to DNA treatment, although grey horses bearing melanoma responded to this treatment with moderate tumour remission in a preceding study. Whether the different immunological reactivity compared to other horses may contributes to the melanoma susceptibility of grey horses remains to be elucidated.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0452-3) contains supplementary material, which is available to authorized users.

Design and Structural Requirements of the Potent and Safe TLR-9 Agonistic Immunomodulator MGN1703

Single-stranded oligodeoxynucleotides (ODN), containing nonmethylated cytosine–guanine motifs (CpG ODN), are recognized by the innate immune system as “danger signals.” CpG ODN are efficacious immunomodulators but require phosphorothioate (PT) or other backbone modifications for metabolic stability, which cause toxicities in mice and primates. We therefore designed a covalently closed DNA molecule (dSLIM^®) where two single-stranded loops containing CG motifs are connected through a double-stranded stem in the absence of any nonnatural DNA component. The most promising immunomodulator, MGN1703, comprises two loops of 30 nucleotides containing three CG motifs each, and a connecting stem stem of 28 base pairs. MGN1703 stimulates cytokine secretion [interferon (IFN)-α, IFN-γ, interleukin (IL)-12, IL-6, and IL-2] and activates immune cells by increased expression of CD80, CD40, human leukocyte antigen (HLA)-DR and ICAM-1. Efficacy of immunomodulation strictly depends on the descriptive dumbbell shape and size of the molecule. Variations in stem length and loop size lead to reduced potency of the respective members of the dSLIM^® class. In a representative mouse model, toxicities from injections of high amounts of a CpG ODN-PT and of MGN1703 were evaluated. The CpG ODN-PT group showed severe organ damage, whereas no such or other pathologies were found in the MGN1703 group. Oncological clinical trials of MGN1703 already confirmed our design.

Influences of age and sex on leukocytes of healthy horses and their ex vivo cytokine release

Leukocytes and their functional capacities are used extensively as biomarkers in immunological research. Commonly employed indicators concerning leukocytes are as follows: number, composition in blood, response to discrete stimuli, cytokine release, and morphometric characteristics. In order to employ leukocytes as biomarkers for disease and therapeutic monitoring, physiological variations and influencing factors on the parameters measured have to be considered. The aim of this report was to describe the ranges of selected leukocyte parameters in a sample of healthy horses and to analyse whether age, sex, breed, and sampling time point (time of day) influence peripheral blood leukocyte composition, cell morphology and release of cytokines ex vivo. Flow cytometric comparative characterisation of cell size and complexity in 24 healthy horses revealed significant variance. Similarly, basal release of selected cytokines by blood mononuclear cells also showed high variability [TNFα (65-16,624pg/ml), IFNγ (4-80U/ml), IL-4 (0-5069pg/ml), IL-10 (49-1862pg/ml), and IL-17 (4-1244U/ml)]. Each animal's age influenced leukocyte composition, cell morphology and cytokine release (TNFα, IL-4, IL-10) ex vivo. Geldings showed smaller monocytes and higher spontaneous production of IL-10 when compared to the mares included. The stimulation to spontaneous release ratios of TNFα, IL-4 and IL-17 differed in Warmblood and Thoroughbred types. Sampling time influenced leukocyte composition and cell morphology. In summary, many animal factors - age being the dominant one - should be considered for studies involving the analysis of equine leukocytes. In addition, high inter-individual variances argue for individual baseline measurements.

Maintenance therapy with the TLR-9 agonist MGN1703 in the phase II IMPACT study of metastatic colorectal cancer patients: A subgroup with improved overall survival

680

Background: Patients with mCRC and disease control after induction with first-line chemotherapy +/- bevacizumab were included in the double-blind placebo-controlled phase II IMPACT trial, aiming to assess the clinical efficacy, safety, and immunological effects of the immunomodulator MGN1703, a potent TLR9 agonist, given at the dose of 60 mg subcutaneously twice weekly as switch maintenance after first line induction therapy in mCRC. Methods: The trial was prematurely closed after randomization of 59 patients. The final analysis showed a superior effect of MGN1703 compared to placebo with hazard ratios (HR) for the primary endpoint PFS on maintenance of 0.55 (p=0.041) and 0.56 (p=0.070) by local investigator assessment or independent radiological review, respectively. Exploratory PFS analyses of pretreatment characteristics identified patients with normalized CEA, objective response, and the presence of activated NKT cells at the end of induction chemotherapy to benefit the most from maintenance with MGN1703. We analysed the impact of these factors on the secondary endpoint overall survival (OS). Results: At time of final study analysis, OS data were not mature. Only 35% of MGN1703 patients had an event, as opposed to 50% of placebo patients. The HR for OS of whole study population was 0.63 (median 22.6 vs. 15.1 months, p=NS). The subgroup of patients randomized into the study with confirmed RECIST response had a HR of 0.40 (median 24.5 vs. 15.1 months, p=NS), suggesting this may be the population with greater benefit. HR for patients with normalized CEA or with activated NKT cells were 0.69 and 0.43, respectively. Based on this evidence, in the phase III IMPALA study patients with objective response after standard induction therapy are randomized to standard treatment or switch maintenance with MGN1703. CEA and activated NKT cells are stratification factors for the study and will be prospectively assessed. Conclusions: The pretreatment characteristics predictive of a PFS benefit in the IMPACT study seem to retain their value also in exploratory analyses for OS. This information has been used to design the phase III IMPALA study, currently recruiting patients. Clinical trial information: NCT01208194.

Abstract 2565: Conformation overrides base sequence - insights from a novel class TLR-9 agonists

Introduction

DNA-based TLR-9 agonists are potent activators of immune cell populations and the immune system. Preclinical and ongoing clinical studies support the use of TLR-9 agonists as immunomodulators and/or adjuvants, and proof their anti-tumor effect by enhancing both the humoral and cellular responses. From the 4 classes of known activators with distinct immunomodulation profiles all members except one comprise of linear DNA molecules. The exception is dSLIM®, the active ingredient of MGN1703 in several clinical trials. dSLIM® establishes a new class of TLR-9 agonists, represented by covalently closed dumbbell-like DNA molecules consisting entirely of natural DNA with two single-stranded CG-containing loops separated by a double-stranded stem.

Results

By cytokine secretion and cellular activation of relevant cells in human PBMC we show that CG-motifs - such as in ODN2006, a class B TLR9 agonist - if incorporated in dSLIM® conformation reveal an improved immunomodulatory potential compared to their corresponding linear CpG oligonucleotides. Increased cytokine secretion encompasses the central anti-cancer cytokine IFN-alpha, the potent angiostatic cytokine IP-10, or IFN-gamma the key activator of NK-, NKT-, and cytotoxic T-cell responses. After 24-48h exposure to dSLIM® TLR-9 agonists, also activation surface markers of relevant cell subpopulations of PBMC are up-regulated including CD80 of pDCs, CD86 of B-cells, CD86 and CD169 of monocytes, CD69 of NK, NKT as well as T cells. Consequently, dSLIM® triggers an explicit specific cytotoxicity against Jurkat target cells while ODN2006 is without significant effect in this readout. All these effects are considered important and relevant cancer-fighting features of dSLIM®.

Conclusions

Differences in immunomodulation profiles between classes of TLR-9 agonists appear to be more closely related to their conformation than their individual nucleotide sequences. We show individual loop sequences in dSLIM® that differentiate the immunomodulation profile of molecules only to a moderate extent. Inherent to the dumbbell-like structure of dSLIM® TLR-9 agonists is their potential to dimerize loop-binding TLR-9 molecules in the membrane of immune-competent cells. Thereby, dSLIM® TLR-9 agonists most probably not only bind and activate but also cluster TLR-9 molecules thereby changing the TLR-9 triggered immune response in a qualitative way. Stabilizing chemical modifications in linear CpG ODN also impact the immunomodulatory profile of TLR-9 agonists and are discussed.

Citation Format: Kerstin Kapp, Christiane Kleuss, Matthias Schroff, Burghardt Wittig. Conformation overrides base sequence - insights from a novel class TLR-9 agonists. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2565. doi:10.1158/1538-7445.AM2014-2565

Maintenance treatment with the immunomodulator MGN1703, a Toll-like receptor 9 (TLR9) agonist, in patients with metastatic colorectal carcinoma and disease control after chemotherapy: a randomised, double-blind, placebo-controlled trial

PURPOSE

This phase II study evaluated the synthetic DNA-based immunomodulator and Toll-like receptor 9 agonist MGN1703 as maintenance treatment in metastatic colorectal carcinoma (mCRC).

METHODS

Fifty-nine patients with mCRC and disease control after standard first-line chemotherapy were randomised to MGN1703 60 mg (N = 43) or placebo (N = 16).

RESULTS

The hazard ratio (HR) for the primary endpoint [progression-free survival (PFS) from the start of maintenance] was 0.56 (95 % CI 0.29-1.08; P = 0.07) and 0.55 (95 % CI 0.3-1.0; P = 0.04) by independent and investigator review, respectively. MGN1703 significantly improved PFS measured from the start of induction therapy versus placebo on independent (HR 0.49; 95 % CI 0.26-0.94; P = 0.03) and investigator review (HR 0.50; 95 % CI 0.31-1.02; P = 0.02). Overall survival (OS) data remain immature (HR 95 %; 95 % CI 0.3-1.5; P = 0.29) with 28/43 patients alive after a medium follow-up of >17 months. Retrospective subgroup analysis showed a significant effect of MGN1703 on PFS versus placebo in patients with greater than median tumour size reduction and normalised carcinoembryonic antigen concentrations following induction therapy, and in patients with elevated activated NKT cells ≥3.08 %. Adverse events were mild to moderate and limited to injection-site reactions or linked to general immune system activation.

CONCLUSIONS

MGN1703 maintenance treatment was well tolerated and appears to induce durable and prolonged PFS and disease control in a subgroup of patients with mCRC following induction therapy. Activated NKT cells may be a predictive biomarker for selecting patients likely to benefit more from MGN1703.

ASET study: Long-term follow-up data of patients with metastatic renal cell carcinoma treated with MGN1601

LBA399

Background: The cell-based therapeutic cancer vaccine MGN1601 is a fixed combination of allogeneic tumor cells modified via MIDGE vectors to express IL-7, GM-CSF, CD80, and CD154 plus the immunomodulator dSLIM. In the ASET trial heavily pretreated patients with metastatic renal cell carcinoma (mRCC) were enrolled to assess safety, immunological effects, and clinical efficacy of MGN1601. Methods: The ASET study was a multicenter, single-arm phase 1/2 study. The treatment phase consisted of 8 intradermal vaccinations over 12 weeks. Following evaluation, patients with at least disease stabilization entered an extension phase (EP, 5 vaccinations over 120 weeks). Overall, 19 patients were included and received at least one MGN1601 injection (ITT); the majority (N=17) had ≥3 lines of previous therapy. Results: Of 19 patients, 10 (55%) completed the treatment phase per-protocol (PP); 9 patients discontinued the study due to disease progression (PD) or rapid deterioration. Overall, 110 adverse events were documented (grade 1-2: 80.9%) of which only 10 (9.1%) were drug-related. No drug-related serious adverse event was reported. PBMCs from patients increased cytokine secretion after re-stimulation with standard antigens, confirming an improved cellular immune function. Two patients achieved disease control (PR, SD) after 12 treatment weeks and continued in the extension phase: One patient had PD after 60 weeks, the other remains in sustained partial remission after completion of the EP. Median overall survival (OS) was 24.8 weeks in the ITT population and 115.3 weeks in the PP population. Univariate analysis of pre-treatment characteristics revealed absolute lymphocyte counts, neutrophil to lymphocyte ratios, platelets, MSKCC score, and liver metastasis as putative predictive factors of longer overall survival. Conclusions: MGN1601 administration was safe and showed promising OS in a population of heavily pretreated RCC patients who could receive therapy over 12 weeks (PP population). These results warrant further evaluation in a larger, controlled clinical trial. Baseline biomarkers and factors may allow identifying patients more likely to benefit from this innovative vaccination approach. Clinical trial information: NCT01265368.

Preclinical study on combined chemo- and nonviral gene therapy for sensitization of melanoma using a human TNF-alpha expressing MIDGE DNA vector

Nonviral gene therapy represents a realistic option for clinical application in cancer treatment. This preclinical study demonstrates the advantage of using the small-size MIDGE(®) DNA vector for improved transgene expression and therapeutic application. This is caused by significant increase in transcription efficiency, but not by increased intracellular vector copy numbers or gene transfer efficiency. We used the MIDGE-hTNF-alpha vector for high-level expression of hTNF-alpha in vitro and in vivo for a combined gene therapy and vindesine treatment in human melanoma models. The MIDGE vector mediated high-level hTNF-alpha expression leads to sensitization of melanoma cells towards vindesine. The increased efficacy of this combination is mediated by remarkable acceleration and increase of initiator caspase 8 and 9 and effector caspase 3 and 7 activation. In the therapeutic approach, the nonviral intratumoral in vivo jet-injection gene transfer of MIDGE-hTNF-alpha in combination with vindesine causes melanoma growth inhibition in association with increased apoptosis in A375 cell line or patient derived human melanoma xenotransplant (PDX) models. This study represents a proof-of-concept for an anticipated phase I clinical gene therapy trial, in which the MIDGE-hTNF-alpha vector will be used for efficient combined chemo- and nonviral gene therapy of malignant melanoma.

Maintenance with the TLR-9 agonist MGN1703 versus placebo in patients with advanced colorectal carcincoma (mCRC): A randomized phase II trial (IMPACT)

3643

Background: Standard induction chemotherapy for mCRC is often discontinued in patients responding to the treatment. MGN1703, a synthetic DNA-based immunomodulator, acts as TLR-9 agonist. This trial has been conducted to assess clinical efficacy, safety, and immunogenicity of MGN1703 as maintenance therapy vs placebo. Methods: The IMPACT trial is an international, multicenter, randomized (2:1) double-blind placebo-controlled phase 2 trial in mCRC patients with disease control (CR, PR, SD) after 4.5 to 6 months of 1st-line induction chemotherapy with FOLFOX/XELOX or FOLFIRI +/- bevacizumab. Results: 59 patients have been randomized (43 MGN1703, 16 placebo). Median PFS from start of maintenance was not different with 2.8 vs 2.7 months, however the HR was 0.56 (CI 95%: 0.29-1.08; p=0.069) in favor of MGN1703, due to a small favorable subgroup with long-term PFS (20% vs 0% at 9 months; p=0.006). Total PFS from beginning of induction chemotherapy including maintenance was significantly improved: HR 0.49 (CI 95%: 0.25-0.94), p=0.029. After a median follow-up of 13 months 66% of patients are still alive (67% vs 62%), therefore survival data are still preliminary (HR 0.79; CI 95%: 0.3-2.1) and will be mature at the meeting. Activation of cellular immune function as indicated by significant increase of CD14+CD169+monocytes was observed in all but one of the MGN1703 treated patients, while absent in all placebo patients. Treatment was well tolerated: 46.5% vs 31.3% of patients (MGN1703 vs placebo) had any drug-related adverse events (AE) and 20.9% vs 18.8% had AE with grade 3 or 4 (including hypertension, ileus, sepsis, sensory polyneuropathy, nausea/vomiting for MGN1703 and pain, popular exanthema for placebo). Conclusions: MGN1703 maintenance seems to prolong PFS in a subgroup of patients with disease control after induction chemotherapy vs placebo, and is associated with relative mild toxicity. This in an early signal in a selected and very limited patient population which supports further investigation. Predictive biomarkers are under evaluation to identify a potential subgroup which might have benefit from this TLR-9 MGN1703 maintenance. Clinical trial information: NCT01208194.

Identification of biomarkers for overall survival of patients with metastatic renal cell carcinoma treated with MGN1601

468

Background: The cell-based therapeutic cancer vaccine MGN1601 consists of two active pharmaceutical ingredients in fixed combination. Fourfold gene-modified, allogeneic tumor cells expressing IL-7, GM-CSF, CD80, and CD154 through MIDGE gene expression vectors are combined with the DNA-based immunomodulator dSLIMas a TLR-9 agonist. In the phase I-II clinical trial (ASET trial) heavily pre-treated patients with metastatic renal cell carcinoma (mRCC) were enrolled. Methods: TheASET study has been conducted as a multicenter, open, single-arm phase I-II study. The treatment phase (TP) consisted of 8 intradermal vaccinations, administered within 12 weeks. We analysed known mRCC prognostic factors for their predictive value, i.e. safety laboratory and immunological parameters, quality of life, local reactions and other patients’ characteristics. Results: 19 patients from the ASET study, who received at least one vaccination (ITT population), were included in the biomarker evaluation. The median overall survival (mOS) in the ITT population is currently 25 weeks. mOS of patients who discontinued TP prematurely was only 10 weeks. However, mOS of those patients who completed at least TP is not yet mature for statistical calculation (NR), but is currently estimated as 69 weeks, resulting in a highly significant difference (10 weeks vs. NR, p < 0.001). Patients with an absolute lymphocyte counts (ALC) at baseline of ≥1,000/μL had increased overall survival (mOS NR vs. 16 weeks, p = 0.013), if compared to those with an ALC <1,000/μL. Neutrophil lymphocyte ratios (NLR) at baseline of >3, bone and liver metastasis, high MSKCC score were identified as risk factors associated with lower overall survival. ALC ≥1,000/μL after three MGN1601 vaccinations (week 5) was even more significantly associated with increased overall survival (mOS NR vs. 17 weeks, p = 0.007). The NLR and quality of life improvement at week 5 as well as local reactions at injection sites seem to correlate with OS. Conclusions: MGN1601 shows promising efficacy in late stage mRCC patients. The identified parameters should be further investigated as potential biomarkers for efficacy. Clinical trial information: NCT01265368.