NOD2/RIG-I Activating Inarigivir Adjuvant Enhances the Efficacy of BCG Vaccine Against Tuberculosis in Mice

Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) kills about 1.5 million people each year and the widely used Bacille Calmette-Guérin (BCG) vaccine provides a partial protection against TB in children and adults. Because BCG vaccine evades lysosomal fusion in antigen presenting cells (APCs), leading to an inefficient production of peptides and antigen presentation required to activate CD4 T cells, we sought to boost its efficacy using novel agonists of RIG-I and NOD2 as adjuvants. We recently reported that the dinucleotide SB 9200 (Inarigivir) derived from our small molecule nucleic acid hybrid (SMNH)^® platform, activated RIG-I and NOD2 receptors and exhibited a broad-spectrum antiviral activity against hepatitis B and C, Norovirus, RSV, influenza and parainfluenza. Inarigivir increased the ability of BCG-infected mouse APCs to secrete elevated levels of IL-12, TNF-α, and IFN-β, and Caspase-1 dependent IL-1β cytokine. Inarigivir also increased the ability of macrophages to kill MTB in a Caspase-1-, and autophagy-dependent manner. Furthermore, Inarigivir led to a Capsase-1 and NOD2- dependent increase in the ability of BCG-infected APCs to present an Ag85B-p25 epitope to CD4 T cells in vitro. Consistent with an increase in immunogenicity of adjuvant treated APCs, the Inarigivir-BCG vaccine combination induced robust protection against tuberculosis in a mouse model of MTB infection, decreasing the lung burden of MTB by 1-log10 more than that afforded by BCG vaccine alone. The Inarigivir-BCG combination was also more efficacious than a muramyl-dipeptide-BCG vaccine combination against tuberculosis in mice, generating better memory T cell responses supporting its novel adjuvant potential for the BCG vaccine.

Trends in malignant melanoma mortality in 31 countries from 1985 to 2015

BACKGROUND

Malignant melanoma (MM) causes the highest absolute number of deaths among skin cancers. An up-to-date analysis of international MM mortality trends is required for assessing the burden of disease, and may support the assessment of the effectiveness of new diagnostic, therapeutic and preventative strategies.

OBJECTIVES

To report MM mortality trends between 1985 and 2015 using the World Health Organization (WHO) Mortality Database.

MATERIALS AND METHODS

We used country-level MM mortality data from the WHO Mortality Database for all countries with high usability death registration data. Mortality trends were described using Joinpoint regression modelling.

RESULTS

Thirty-one countries met the inclusion criteria. All countries, except the Czech Republic, demonstrated increased age-standardized death rates (ASDRs) in males over the observation period. More countries exhibited decreased or stable MM mortality in females. The median mortality rate for 2013-2015 was 2·57 deaths per 100 000 for males and 1·55 per 100 000 for females. Australia and Norway had the highest ASDRs for males (5·72 per 100 000 and 4·55 per 100 000, respectively). Norway and Slovenia had the highest ASDRs for females (3·02 per 100 000 and 2·58 per 100 000, respectively). MM mortality was greater for males than females in all countries, with sex disparity increasing across the period. Disparity in mortality between older and younger cohorts in several countries was also found.

CONCLUSIONS

An overall increase in MM mortality over the past 30 years was observed. However, there was notable variation in mortality trends between countries, as well as between males and females, and between different age groups.

Abstract B87: Mechanistic insights into the antitumor activity of SB 11285—a novel STING agonist

Background: Cancer immunotherapy is a highly effective therapeutic option for cancer patients. However, the overall response rate with checkpoint inhibitors and other related modalities has been modest. Targeting innate immune signaling pathways that induce type I IFN production to reprogram tumor microenvironment and restore antitumor immunity represents a novel immunotherapeutic approach. We have previously reported that SB 11285 is a first-in-class synthetic cyclic dinucleotide STING agonist, which has demonstrated potent antitumor activity, when used alone or combined with other antitumor agents, in several syngeneic mouse and rat tumor models when administered by intratumoral, intravenous or intraperitoneal routes. Presented here are studies that provide additional insights into the mechanism of action of SB 11285 and analogs.

Methods: (a) SB 11285 induces Type I IFN production and other cytokines in human PBMCs and PBMC-derived monocytes. PBMCs and monocytes, isolated from fresh PBMCs using pan monocyte isolation kit (Miltenyi Biotec), were stimulated with SB 11285. Type I IFNs and other cytokines were quantified using regular and multiplex ELISA assays. (b) SB 11285 directly binds STING. To address whether SB 11285 directly binds wild-type human STING, surface plasmon resonance assay was performed with a Biacore T200 device and a biotinylated SB 11285 analog (Biot-SB 11285). (c) Activity against STING polymorphs. Evaluation of SB 11285 and analogs was carried out using both SZ14 reporter cells (HEK293-derived) and HEK293T cells that stably or transiently express STING polymorphic variants. (d) Pharmacodynamic studies. Normal BALB/c mice were injected intravenously with SB 11285 or its analogs at 9 mg/kg. Serum, spleen, and liver samples were collected to quantify RANTES and TNF-α using ELISA. The expression of representative ISGs in spleen samples, including IRF7, IFIT2, and OAS1b were quantified using real-time PCR. (e) Determination of cellular uptake of SB 11285 by PBMCs. The STING agonist activity of Biot-SB 11285 in inducing type I IFN response was confirmed using SZ14 reporter cells and THP1-Dual-WT reporter cells. Human PBMCs were incubated with Biot-SB 11285 and the cellular uptake of compound by immune cells was evaluated using flow cytometry.

Results and Conclusion: Our studies provide significant mechanistic insights into the STING agonistic activity of SB 11285 and analogs in that they: (a) induce Type I IFNs, other cytokines and chemokines in PBMCs and monocytes, monocyte-derived dendritic cells; (b) directly bind STING with nanomolar affinity; (c) activate multiple human STING polymorphic variants; (d) induce cytokines, chemokines, and ISGs in mice following i.v. injection; and (e) are effectively taken up by monocytes and other immune cells. SB 11285 is being advanced to human clinical trials.

Citation Format: Shenghua Zhou, Sreerupa Challa, Vishal Nair, Geeta Meher, Anjaneyulu Sheri, Rayomand Gimi, Seetharamaiyer Padmanabhan, Dillon Cleary, Leena Suppiah, Diane Schmidt, Santosh Khedkar, Radhakrishnan Iyer. Mechanistic insights into the antitumor activity of SB 11285—a novel STING agonist [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B87.

Abstract B75: Nanoparticle formulation of the STING agonist SB 11285

Background: Immunotherapy has emerged as a transformative approach for the treatment of cancer. Recent evidence suggests that the activation of Stimulator of Interferon Genes (STING) pathway in immune calls within the tumor microenvironment (TME) can induce the production of Interferons and cytokines that would lead to the induction of innate and adaptive immunity. We have previously disclosed the discovery and development of SB 11285 as a first-in-class synthetic cyclic dinucleotide STING agonist, which has demonstrated potent antitumor activity, when used alone or combined with other antitumor agents, in several syngeneic mouse and rat tumor models when administered by intratumoral, intravenous, or intraperitoneal routes. Presented here is the development of a controlled-release nanoparticle formulation of SB 11285 for subcutaneous administration.

Methods: (a) Nanoparticle formulations of SB 11285. SB 11285-NPs were generated using Polylactic-glycolic acid copolymer (PLGA) using double emulsion and nano-precipitation methods (b) Imaging of nanoparticles: Scanning electron microscopy was performed to visualize and measure size of the nanoparticles. (c) Induction of IRF3 and NF-KB. THP-1 cells and RAW macrophages carrying dual reporter constructs were treated with either SB 11285-NPs or naked SB 11285 for 22hrs and induction of IRF3 and NF-KB was calculated as % fold-change in luminescence compared to vehicle-treated cells. (d) Induction of cytokines: PBMCs were treated with different concentrations of 11285-NPs or naked SB 11285, and cell supernatants were analyzed for IFN-β, TNF-α, and RANTES by ELISA. (e) Dendritic cell maturation assay: PBMCs were differentiated into immature dendritic cells by addition of IL4 and GM-CSF followed by treatment with either SB 11285-NP or naked SB 11285. The maturation of dendritic cells was then evaluated by analyzing expression of CD83 and CD86 by flow cytometry.

Results: PLGA formulations of SB 11285 prepared by double-emulsion method with an entrapment efficiency of 30 to 40% were spherical particles with an average diameter of 800nm. The nanoparticles were stable in aqueous media with minimal release of the entrapped SB 11285. In cell-culture studies, SB 11285-NPs showed potent induction of: (a) STING-dependent IRF3 induction in THP-1 cells (EC50: 3nM) as well as RAW macrophages (EC50: 3nM); (b) secretion of IFN-β (35 pg/ml), TNF-α (800 pg/ml), and RANTES (200 pg/ml), when tested at a low concentration of 112nM; and (c) SB 11285-NPs effectively induced DC maturation that was evident by increase in CD83 and CD86 expression.

Conclusion: PLGA nanoparticles of SB 11285 were successfully prepared with submicron particle size that demonstrated potent expression of STING-dependent Type I IFN and cytokines in immune cells. The nanoparticles also induced maturation of dendritic cells. In vivo evaluation is in progress.

Citation Format: Sreerupa Challa, Leena Suppiah, Dillon Cleary, Anjaneyulu Sheri, Rayomand Gimi, Geeta Meher, Seetharamaiyer Padmanabhan, Sumit Shah, Pranav Bhatt, Jovita Tauro, Radhakrishnan Iyer. Nanoparticle formulation of the STING agonist SB 11285 [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B75.

Abstract B53: Development of SB 11 and SB 12, structurally unique linkage analogs of SB 11285 as STING agonists for Immuno-oncology

Background: Agonists of the Stimulator of Interferon Genes (STING) pathway have great potential in cancer immunotherapy. Activation of STING in tumor cells and/or antige- presenting cells (APCs) can induce type I Interferon production, leading to the induction of innate and adaptive immune response. We recently reported the discovery of the cyclic dinucleotide SB 11285 as a potent, first-in-class, STING agonist. Herein, we report SB 11 and SB 12 as unique linkage analogs of SB 11285.

Methods: (a) Synthesis: Several linkage analogs of SB 11285 were synthesized by standard solution-phase phosphoramidite chemistry and screened for STING agonistic activity using the previously described SZ14 reporter cell lines, and SB 11 and SB 12 were identified as lead compounds., (b) Binding affinity: Differential scanning fluorimetry was used to determine binding affinity of SB 11 and 12 to wtSTING, with 2´,3´-cGAMP being used as a positive control. (c) Induction of IRF3 and NF-KB: wtTHP-1 or R232-THP1 or RAW cells carrying the respective reporter constructs were treated with SB 11 and 12 or controls for 22hrs and induction of IRF3 and NF-KB was determined as % fold-change in luminescence compared to vehicle-treated cells. (d) Induction of cytokines: PBMCs and mBMDCs were treated with SB 11 and 12 at different doses, and cell supernatants were analyzed for IFN-β, TNF-α, and RANTES by ELISA or multiplexing Luminex assays. (e) In vivo studies: Both SB 11 and 12 were tested for antitumor efficacy in CT26 syngeneic mouse tumor model after intravenous (i.v.) administration at 3mg/kg on days 1,5,9,14.

Results: (i) SB 11 and 12 demonstrated high binding affinity to human wild-type and mouse STING that is evident by 16° thermal shift. (ii) SB 11 and 12 showed potent induction of (a) STING-dependent IRF3 (EC50: 0.8 and 39.7 nM) and NF-κB (EC50: 9 and 5265 nM) signaling induction in wtTHP-1 cells; (b) IRF3 (EC50: 2.6 and 317 nM) and NF-κB (EC50: 83 and 3783 nM) induction in R232-THP-1 cells; (c) IRF3 (EC50: 67 and 46 nM) in RAW macrophages. (iii) Both SB 11 and SB 12 induced STING dependent secretion of IFN-β (~10 ng/ml) in mBMDCs. (iv) In the CT26 colon carcinoma syngeneic mouse models, both SB 11 and 12 showed potent antitumor activity when administered by i.v. route with 98 and 97% TGI and 91 and 79% TGD, respectively.

Conclusion: SB 11 and SB 12 showed excellent safety and antitumor activity in syngeneic mouse model when administered by i.v. route. SB 11 and SB 12 were shown to cause STING-dependent activation of IRF3 and NF-κB signaling, as well as the induction of type I IFN signature and ISGs. Further preclinical studies of systemically administered analogs SB 11 and SB 12 are in progress.

Citation Format: Shenghua Zhou, Sreerupa Challa, Diane Shmidt, Leena Suppiah, Vishal Nair, Anjaneyulu Sheri, Geeta Meher, Rayomand Gimi, Seetharamaiyer Padmanabhan, Dillon Cleary, Radhakrishnan Iyer. Development of SB 11 and SB 12, structurally unique linkage analogs of SB 11285 as STING agonists for Immuno-oncology [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B53.

Relationship between IHC4 score and response to neo-adjuvant chemotherapy in estrogen receptor-positive breast cancer

AIMS

To determine whether IHC4 score assessed on pre-treatment core biopsies (i) predicts response to neo-adjuvant chemotherapy in ER-positive (ER+) breast cancer; (ii) provides more predictive information than Ki67 alone.

METHODS

113 patients with ER+ primary breast cancer treated with neo-adjuvant chemotherapy at the Royal Marsden Hospital between 2002 and 2010 were included in the study. Pathologic assessment of the excision specimen was made for residual disease. IHC4 was determined on pre-treatment core biopsies, blinded to clinical outcome, by immunohistochemistry using quantitative scoring of ER (H-score), PgR (%) and Ki67 (%). Determination of HER2 status was made by immunohistochemistry and fluorescent in situ hybridization for 2+ cases. IHC4 and Ki67 scores were tested for their association with pathological complete response (pCR) rate and residual cancer burden (RCB) score.

RESULTS

18 (16%) of the 113 patients and 8 (9%) of the 88 HER2-ve cases achieved pCR. Ki67 and IHC4 score were both positively associated with achievement of pCR (P < 10-7 and P < 10-9, respectively) and RCB0+1 (P < 10-5 and P < 10-9, respectively) following neo-adjuvant chemotherapy in all patients. Rates of pCR+RCB1 were 45 and 66% in the highest quartiles of Ki67 and IHC4 scores, respectively. In ER+HER2-ve cases, pCR+RCB1 rates were 35% and in the highest quartile of both Ki67 and IHC4. There were no pCRs in the lower half of IHC4 or Ki67 scores.

CONCLUSIONS

IHC4 was strongly predictive of pCR or near pCR in ER+ breast cancers following neo-adjuvant chemotherapy. Ki67 was an important component of this predictive ability, but was not as predictive as IHC4.

SB 9200, a novel agonist of innate immunity, shows potent antiviral activity against resistant HCV variants

SB 9200 is a novel, first-in-class oral modulator of innate immunity that is believed to act via the activation of the RIG-I and NOD2 pathways. SB 9200 has broad-spectrum antiviral activity against RNA viruses including hepatitis C virus (HCV), norovirus, respiratory syncytial virus, and influenza and has demonstrated activity against hepatitis B virus (HBV) in vitro and in vivo. In phase I clinical trials in chronically infected HCV patients, SB 9200 has been shown to reduce HCV RNA by up to 1.9 log₁₀ . Here, we demonstrate the antiviral activity of SB 9200 against a HCV replicon system and patient derived virus. Using the HCV capture-fusion assay, we show that SB 9200 is active against diverse HCV genotypes and is also effective against HCV derived from patients who relapse following direct-acting antiviral treatment, including viruses containing known NS5A resistance-associated sequences. These data confirm the broad antiviral activity of SB 9200 and indicate that it may have clinical utility in HCV patients who have failed to respond to current antiviral regimens.

Preclinical studies of SB 11285, a novel STING agonist for immuno-oncology

e14616

Background: The activation of innate and adaptive immunity via Stimulator of Interferon Genes (STING) signaling is a potentially transformative immuno-therapeutic strategy in cancer. We report here in vivo efficacy and safety studies of SB 11285. Methods: Tumor Growth Inhibition (TGI) and Tumor Growth Delay (TGD) studies in syngeneic mouse models were initiated when mean tumor volume (MTV) reached 100mm3: A20 Lymphoma: (10 animals/Group); (A) Saline; (B) 100µg SB 11285, intratumoral (i.t.), days 3,4,6,8,10; (C) 100mg/kg Cyclophosphamide, intraperitoneal (i.p), days 1,2; and (D) combination of cyclophosphamide+SB 11285. CT26 Colon Carcinoma experimental design is shown in Table. Re-challenge study was initiated in tumor-free animals in A20 lymphoma model on day 73, and monitored for an additional 45 days. Presence of activated immune cells intumor tissues was evaluated by immuno-histochemistry. Cytokine response was evaluated in serum after a single i.p. injection of SB 11285 at 10mg/kg. Maximum Tolerated Dose (MTD) in mice was determined by daily i.p. injection of SB 11285 for 10 days. Results: A20 model: % TGI in the treatment groups were—A, 0; B, 86; C, 98, and D, 93; % TGD, day 70: A, 0; B, 64; C, 156; D, 288. In D, day 73, 90% of animals remained tumor-free. CT26 model: Table 1 shows MTV on day 19 and %TGD on day 43; Re-challenge study. All animals from the SB 11285-treated groups remained completely tumor-free on day 45 compared to control group (MTV,1666 mm3); Immuno-histochemistry of SB 11285-treated groups, revealed the infiltration of CD8+T and NK cells into tumor and surrounding tissues; Cytokine analysis did not show systemic inflammatory response; MTD of SB 11285 was 16 mg/kg/day. Conclusions: SB 11285, a novel STING agonist, showed very potent, and highly durable immune response-mediated anti-tumor activity. SB 11285 was well tolerated, safe, and is being advanced to IND-enabling studies. [Table: see text]

Abstract B40: Nucleotide analogs as novel STING agonists for immuno-oncology

Immunotherapy has recently emerged as a transformative approach for the treatment of cancer; nevertheless, many patients remain unresponsive to treatment. Recent evidence suggests that the activation of Stimulator of Interferon Genes (STING) pathway in tumor cells and/or antigen presenting cells (APCs) within the tumor microenvironment (TME) can induce type I Interferon production leading to apoptosis of tumor cells, as well as, induction of adaptive immune response (through priming of CD8+ T cells to tumor-associated antigens) thereby providing a powerful anti-cancer strategy. Therefore, therapeutic agents that activate STING signaling pathway in tumor cells and APCs in the TME are urgently needed. Herein, we describe the discovery of highly potent and selective first-in-class STING agonists for application in immuno-oncology.

Methods: Using structure-guided drug design, in conjunction with published crystal structures of different cyclic dinucleotides bound to STING, a focused library of nucleotide compounds was prepared using standard phosphoramidite chemistry. The compounds were screened for induction of Interferon regulatory factor (IRF), Interferon-stimulated gene 54 (ISG54), and NF-KB using reporter assays. We used HEK293 cell line stably expressing ISG54 (ISRE)-promoter-driven firefly luciferase reporter gene for initial hit discovery and the actives were further characterized in PBMCs and THP1 cells. The IRF and NF-kB induction was calculated from % fold-change in luminescence compared to DMSO-treated cells and EC50 of the compounds were ascertained using Xlfit. Lead STING agonists were further evaluated for: (a) Binding affinity: Binding assays were conducted by Differential Scanning Fluorimetry (DSF) and Tm was calculated using Thermal Shift software, (b) Induction of pathogen recognition receptors (PRRs), ISGs and Programmed Death Ligands 1 & 2 (PDL1, PDL2) genes: THP1 cells and PBMCs were treated with various concentrations of lead compounds or 2,'3'-cGAMP or DMSO and the gene expression of different PRRs, ISGs, PDL1, and PDL2 was determined by quantitative RT-PCR using ΔΔct method, (c) Apoptosis-inducing activity: PBMCs and THP1 cells were treated with various concentrations of lead compounds, 2',3'-cGAMP, or DMSO control and the apoptotic activity was evaluated using Caspase-Glo® 3/7 Assay (Promega), and (d) In vitro anti-tumor activity: STING-dependent anti-tumor activity of lead compounds in various tumor cell lines was assessed by either high-content imaging or through Cell titer Glo® Cytotoxicity Assay (Promega). Cell survival was calculated based upon % reduction of live cells compared to DMSO control. CC50 of the compounds were generated by curve fit in Xlfit.

Results: Through in vitro assays in conjunction with Structure Activity Relationship (SAR) studies, we have identified several highly potent and selective first-in-class STING agonists. A promising lead nucleotide compound SB 11285 caused STING-dependent induction of: (a) IRF with an EC50 of 2 nM that is 1000-fold more potent than the natural STING agonist 2',3'-cGAMP, (b) NF-kB with an EC50 of 200 nM that is &gt;200-fold more potent than 2',3'-cGAMP, (c) selective apoptosis of human monocyte leukemic cell lines (CC50, 500 nM) as compared to normal PBMCs through induction of IFN, and NF-kB signaling, and (d) expression of various PRRs and ISGs including RIG-I, MDA-5, LGP2, ISG54 and OAS-1, as well as, PDL1 and PDL2. Finally, SB 11285 showed potent in vitro anti-tumor activity in multiple tumor cell lines.

Conclusion: We have discovered highly potent first-in-class STING agonists that show excellent selectivity in induction of IFN, NF-KB, ISGs, and PRRs, and apoptosis of tumor-derived cell lines. The lead STING agonist SB 11285 has potent immune-modulating, as well as, anti-tumor activities and is being advanced for additional preclinical studies for application in immuno-oncology.

Citation Format: Sreerupa Challa, Shenghua Zhou, Anjaneyulu Sheri, Seetharamaiyer Padmanabhan, Samantha Delaney, Geeta Meher, Dillon Cleary, Vishal Nair, Rayomand Gimi, Santosh Khedkar, Radhakrishnan Iyer. Nucleotide analogs as novel STING agonists for immuno-oncology. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr B40.

Abstract B39: Novel dinucleotides that activate STING signaling for immuno-oncology

Background: Immunotherapy has recently emerged as a transformative approach for the treatment of cancer; nevertheless, many patients remain unresponsive to treatment. It is being recognized that induction of type I interferons (IFN) and interferon-stimulated genes (ISGs) in tumor cells and within the tumor microenvironment (TME) is essential for modulating the host-immune response and inducing apoptosis of tumor cells. Furthermore, the antigen-presenting cells within TME can cause induction of adaptive immune response, through priming of CD8+ T cells and tumor killing. Importantly, the DNA released from damaged cells and cancer cells can be sensed by cyclic GMP-AMP synthase (cGAS) leading to the synthesis of cyclic-GMP-AMP (2',3'-cGAMP), a second messenger that activates Stimulator of Interferon Genes (STING) pathway resulting in the production of type I IFN and ISGs. The cumulative effects of activation of innate and adaptive immune response can result in potent anti-cancer effects. Therefore, therapeutic agents that activate the cGAS-STING signaling pathway in tumor cells and TME are urgently needed. Herein, we describe the discovery of novel potent, first-in-class small molecules for application in immuno-oncology.

Methods: Using structure-guided drug design, in conjunction with published crystal structures of cyclic dinucleotides bound to STING, a focused library of dinucleotide compounds was synthesized using phosphoramidite chemistry and evaluated for: (a) Induction of IFN signaling: The compounds were screened for the induction of Interferon regulatory factor (IRF), ISG54, and NF-κB using reporter assays. We used HEK293 cell line (SZ14) stably expressing ISG54 (ISRE)-promoter-driven firefly luciferase reporter gene for screening and the active compounds were further characterized in THP1 cells and human primary PBMCs. The IRF, ISG54, and NF-κB induction was calculated from % fold-change in luminescence compared to DMSO-treated cells and EC50s of the compounds were ascertained to identify active compounds, (b) Expression of IFN-β and IRF7 in THP1 cells: THP1 cells were treated with active compounds or controls for 22hrs. RNA was extracted and the expression of IFN-β, IRF7, was ascertained using semi-quantitative RT-PCR, (c) Induction of pathogen recognition receptors (PRRs) including RIG-I, MDA5, LGP2, and OAS-1 and ISG54: THP1 cells and PBMCs were treated with active compounds, 2',3'-cGAMP (control), or DMSO and the gene expression of different PRRs, ISGs, was determined by quantitative RT-PCR using ΔΔct method, (d) Induction of cGAS-STING signaling using reporter assays: HEK293 cells stably expressing ISG54 were transfected with plasmids encoding human cGAS (wild-type, or K384A, K400A, or K411A mutants) and treated with active compounds, poly (dA:dT) (positive control), or DMSO for 21 hrs. ISG54 induction was calculated as fold-change in luminescence compared to DMSO-treated controls. (e) Cytotoxicity assays: THP1 cells were treated with active compounds or DMSO control with Lipofectamine and cytotoxicity assessed using the CellTiter-Glo® Luminescent assays. Cytotoxicity was calculated from %-fold change in luminescence compared to DMSO-treated sample.

Results: Through in vitro assays in conjunction with Structure Activity Relationship studies, we have identified potent compounds that activate cGAS-STING signaling pathway for induction of IRF, IFN, and NF-κB. These compounds also cause induction of expression of PRRs, including RIG-I, MDA5, LGP2, as well as, ISG54 and OAS-1.

Conclusion: We have discovered potent, first-in-class agents that cause induction of IFN, NF-κB, ISGs, and PRRs. Further optimization and preclinical evaluation of the compounds for application in immuno-oncology is underway.

Citation Format: Shenghua Zhou, Sreerupa Challa, Seetharamaiyer Padmanabhan, Anjaneyulu Sheri, Samantha Delaney, Geeta Meher, Dillon Cleary, Rayomand Gimi, Santosh Khedkar, Radhakrishnan Iyer. Novel dinucleotides that activate STING signaling for immuno-oncology. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr B39.

Antiviral Efficacy and Host Immune Response Induction during Sequential Treatment with SB 9200 Followed by Entecavir in Woodchucks

SB 9200, an orally bioavailable dinucleotide, activates the viral sensor proteins, retinoic acid-inducible gene 1 (RIG-I) and nucleotide-binding oligomerization domain-containing protein 2 (NOD2) causing the induction of the interferon (IFN) signaling cascade for antiviral defense. The present study evaluated the overall antiviral response in woodchucks upon induction of immune response, first with SB 9200 followed by Entecavir (ETV) versus reduction of viral burden with ETV followed by SB 9200 immunomodulation. Woodchucks chronically infected with woodchuck hepatitis virus (WHV) were treated orally with SB 9200 (30 mg/kg/day) and ETV (0.5 mg/kg/day). Group 1 received ETV for 4 weeks followed by SB 9200 for 12 weeks. Group 2 received SB 9200 for 12 weeks followed by ETV for 4 weeks. At the end of treatment in Group 2, average reductions of 6.4 log₁₀ in serum WHV DNA and 3.3 log₁₀ in WHV surface antigen were observed whereas in Group 1, average reductions of 4.2 log₁₀ and 1.1 log₁₀ in viremia and antigenemia were noted. Both groups demonstrated marked reductions in hepatic WHV nucleic acid levels which were more pronounced in Group 2. Following treatment cessation and the 8-week follow-up, recrudescence of viral replication was observed in Group 1 while viral relapse in Group 2 was significantly delayed. The antiviral effects observed in both groups were associated with temporally different induction of IFN-α, IFN-β, and IFN-stimulated genes in blood and liver. These results suggest that the induction of host immune responses by pretreatment with SB 9200 followed by ETV resulted in antiviral efficacy that was superior to that obtained using the strategy of viral reduction with ETV followed by immunomodulation.

Residual proliferative cancer burden to predict long-term outcome following neoadjuvant chemotherapy

BACKGROUND

The purpose of this study was (i) to test the hypothesis that combining Ki67 with residual cancer burden (RCB) following neoadjuvant chemotherapy, as the residual proliferative cancer burden (RPCB), provides significantly more prognostic information than either alone; (ii) to determine whether also integrating information on ER and grade improves prognostic power.

PATIENTS AND METHODS

A total of 220 patients treated with neoadjuvant chemotherapy for primary breast cancer were included in the study. Analyses employed a Cox proportional hazard model. Prognostic indices (PIs) were created adding in Ki67, grade and ER to RCB. Leave-one-out cross-validation was used to reduce bias. The overall change in χ(2) of the best model for each index was used to compare the prognostic ability of the different indices.

RESULTS

All PIs provided significant prognostic information for patients with residual disease following neoadjuvant chemotherapy. RPCB (χ(2) = 61.4) was significantly more prognostic than either RCB (χ(2) = 38.1) or Ki67 (χ(2) = 53.8) alone P < 0.001. A PI incorporating RCB, Ki67 grade and ER provided the most prognostic information overall and gave χ(2) = 73.8.

CONCLUSIONS

This study provides proof of principle that the addition of post-treatment Ki67 to RCB improves the prediction of long-term outcome. Prediction may be further improved by addition of post-treatment grade and ER and warrants further investigation for estimating post-neoadjuvant risk of recurrence. These indices may have utility in stratifying patients for novel therapeutic interventions after neoadjuvant chemotherapy.

Novel small molecule nucleotide homologs (SMNH) activate human macrophages to kill intracellular Mycobacterium tuberculosis. (VAC6P.949)

Tuberculosis is a major cause of death in mankind and drug resistant tuberculosis has posed a problem for therapy. Immunotherapy is an option for better control of tuberculosis. We discovered two types of novel SMNH compounds which were active as adjuvants since they activated respectively NOD2 and TLR-7 receptors in macrophages. Since these cytosolic pattern recognition pathways lead to bactericidal mechanisms, we tested the efficacy of the SMNHs to activate macrophages to kill mycobacteria. Methods: Human THP1 macrophages were treated with either NOD-2 (SB44, SB44-1) or TLR-7 (SB9922) SMNH followed by infection with M. tuberculosis. Three days later macrophages were lysed and plated for bacterial counts. Cytokines from BMs were estimated using sandwich ELISA and autophagic markers were evaluated using monodansyl cadaverine and fluorescence microscopy. Results: Both NOD2 and TLR-7 activating SMNH compounds reduced the numbers of M. tuberculosis in human macrophages by 1-log10 over 3 days of culture. These SMNHs also reduced the numbers of M. tuberculosis within mouse BMs between 1-2log10 over 3 days. SMNHs activated autophagic processes in macrophages underscoring a new mechanism to kill intracellular M. tuberculosis. Since the main scaffold of SB44 has been used as an adjuvant in human trials, we anticipate that SB44 and SB9922 like compounds can be used as adjuncts to drugs for treating ongoing infections of M. tuberculosis in humans.

Synthesis, biological evaluation, hydration site thermodynamics, and chemical reactivity analysis of α-keto substituted peptidomimetics for the inhibition of Plasmodium falciparum

A new series of peptidomimetic pseudo-prolyl-homophenylalanylketones were designed, synthesized and evaluated for inhibition of the Plasmodium falciparum cysteine proteases falcipain-2 (FP-2) and falcipain-3 (FP-3). In addition, the parasite killing activity of these compounds in human blood-cultured P. falciparum was examined. Of twenty-two (22) compounds synthesized, one peptidomimetic comprising a homophenylalanine-based α-hydroxyketone linked Cbz-protected hydroxyproline (39) showed the most potency (IC50 80 nM against FP-2 and 60 nM against FP-3). In silico analysis of these peptidomimetic analogs offered important protein-ligand structural insights including the role, by WaterMap, of water molecules in the active sites of these protease isoforms. The pseudo-dipeptide 39 and related compounds may serve as a promising direction forward in the design of competitive inhibitors of falcipains for the effective treatment of malaria.

Abstract P1-08-03: Prediction of response to neoadjuvant chemotherapy in estrogen receptor positive (ER+) breast cancer by IHC4 or Ki67 alone

Aims To determine whether IHC4 score assessed on pre-treatment core biopsies (i) predicts response to neoadjuvant chemotherapy in ER positive breast cancer; (ii) provides more predictive information than Ki67 alone.

Background The IHC4 score, a composite of ER, PgR, Ki67 and HER2 scores provides prognostic information similar to the OncotypeDx 21-gene Recurrence Score in ER + primary breast cancer treated with endocrine therapy but it is unknown if it also predicts response to chemotherapy. Pathological complete response (pCR) following neoadjuvant chemotherapy is established as an intermediate marker of long-term outcome. More recently the residual cancer burden (RCB) has also been shown to be prognostic, with those patients with minimal residual disease (RCB1) following neoadjuvant chemotherapy having a similar prognosis to those with a pCR (RCB0). The development of these intermediate markers provides an opportunity to study the predictive role of pre-treatment biomarkers for benefit to a particular therapy.

Methods A total of 114 ER+ patients treated with neoadjuvant chemotherapy at the Royal Marsden Hospital between 2002-2010 were included in the study.

An assessment of the excision specimen was made for residual disease. IHC4 was determined on pre-treatment core biopsies, blinded to clinical outcome, by immunohistochemistry using quantitative scoring of ER (H-score), PgR (%) and Ki67 (%). Determination of HER2 status was made by immunohistochemistry and fluorescent in situ hybridization for 2+ cases. IHC4 and Ki67 scores were tested for their association with pCR rate and RCB score.

Results 19 (17%) of the 114 patients and 9 (10%) of the 90 HER2-ve cases showed a pCR. Ki67 and the IHC4 score were both positively associated with achievement of pCR (P&lt;10-7 and P&lt;10-9 respectively) and RCB0+1 (P&lt;10-5 and P&lt;10-9 respectively) following neoadjuvant chemotherapy in all patients. Rates of RCB0+1 were 45% and 66% in the highest quartiles of Ki67 and IHC4 scores respectively. In ER + HER2-ve cases pCR and RCB0+ 1 rates were 35% and 39%, respectively in the highest quartile of IHC4 and 30% and 39%, respectively in the highest quartile of Ki67 (Table 1). There were no pCRs in the lower half of IHC4 or Ki67 scores.

Conclusions A high IHC4 was strongly predictive of a pCR or near pCR in ER + breast cancers following neoadjuvant chemotherapy. Ki67 was an important component of this predictive ability.

Response according to IHC4 and Ki67 quartile in HER2 negative, ER+ breast cancersIntermediate endpointpCRpCRRCB0+RCB1RCB0+RCB1ScoreIHC4Ki67IHC4Ki67Quartile 10% (0/22)0% (0/22)5% (1/22)9% (2/22)Quartile 20% (0/23)0% (0/23)4% (1/23)0% (0/23)Quartile 35%(1/22)9% (2/23)9% (2/22)9% (2/23)Quartile 435% (8/23)30% (7/23)39% (9/23)39% (9/23)

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-03.

Structures of SHV-1 β-lactamase with penem and penam sulfone inhibitors that form cyclic intermediates stabilized by carbonyl conjugation

Bacterial β-lactamase enzymes are in large part responsible for the decreased ability of β-lactam antibiotics to combat infections. The inability to overcome β-lactamase mediated resistance spurred the development of inhibitors with penems and penam sulfones being amongst the most potent and broad spectrum mechanism-based inactivators. These inhibitors form covalent, “suicide-type” inhibitory intermediates that are attached to the catalytic S70 residue. To further probe the details of the mechanism of β-lactamase inhibition by these novel compounds, we determined the crystal structures of SHV-1 bound with penem 1, and penam sulfones SA1-204 and SA3-53. Comparison with each other and with previously determined crystal structures of members of these classes of inhibitors suggests that the final conformation of the covalent adduct can vary greatly amongst the complex structures. In contrast, a common theme of carbonyl conjugation as a mechanism to avoid deacylation emerges despite that the penem and penam sulfone inhibitors form different types of intermediates. The detailed insights gained from this study could be used to further improve new mechanism-based inhibitors of these common class A serine β-lactamases.

The importance of the trans-enamine intermediate as a β-lactamase inhibition strategy probed in inhibitor-resistant SHV β-lactamase variants

The ability of bacteria to express inhibitor-resistant (IR) β-lactamases is stimulating the development of novel inhibitors of these enzymes. The 2'β-glutaroxypenicillinate sulfone, SA2-13, was previously designed to enhance the stabilization of the deacylation-refractory, trans-enamine inhibitory intermediate. To test whether this mode of inhibition can overcome different IR mutations, we determined the binding mode of SA2-13 through X-ray crystallography, obtaining co-crystals of the inhibitor-protein complex by soaking crystals of the IR sulfhydryl variable (SHV) β-lactamase variants S130G and M69V with the inhibitor. The 1.45 Å crystal structure of the S130G SHV:SA2-13 complex reveals that SA2-13 is still able to form the stable trans-enamine intermediate similar to the wild-type complex structure, yet with its carboxyl linker shifted deeper into the active site in the space vacated by the S130G mutation. In contrast, data from crystals of the M69V SHV:SA2-13 complex at 1.3 Å did not reveal clear inhibitor density indicating that this IR variant disfavors the trans-enamine conformation, likely due to a subtle shift in A237.

The synthesis and biological evaluation of 2-(3-methyl or 3-phenylisoxazol-5-yl)-3-aryl-8-thiabicyclo[3.2.1]octanes

Cocaine, a potent stimulant of the central nervous system, owes its reinforcing and stimulant properties to its ability to inhibit monoamine uptake systems such as the Dopamine Transporter (DAT), and the Serotonin Transporter (SERT) located on presynaptic neurons in the striatum. The search for pharmacotherapies for cocaine addiction has focused on the design of compounds that bind selectively to the DAT and manifest slow onset of stimulatory action with long duration of action. We had reported that 3-aryl-2-carbomethoxy-8-thiabicyclo[3.2.1]octanes are potent and selective inhibitors of the DAT. In this Letter we report on the effects of replacement of the 2-carbomethoy group by a 2-isoxazole. This new class of 8-thiabicyclo[3.2.1]octanes provides potent and selective inhibitors of the DAT. The 3β-aryl compounds are particularly potent inhibitors of DAT (IC(50) = 7-43 nM) with substantial selectivity versus inhibition of SERT.

Design, synthesis, and crystal structures of 6-alkylidene-2'-substituted penicillanic acid sulfones as potent inhibitors of Acinetobacter baumannii OXA-24 carbapenemase

Class D β-lactamases represent a growing and diverse class of penicillin-inactivating enzymes that are usually resistant to commercial β-lactamase inhibitors. As many such enzymes are found in multi-drug resistant (MDR) Acinetobacter baumannii and Pseudomonas aeruginosa, novel β-lactamase inhibitors are urgently needed. Five unique 6-alkylidene-2'-substituted penicillanic acid sulfones (1-5) were synthesized and tested against OXA-24, a clinically important β-lactamase that inactivates carbapenems and is found in A. baumannii. Based upon the roles Tyr112 and Met223 play in the OXA-24 β-lactamase, we also engineered two variants (Tyr112Ala and Tyr112Ala,Met223Ala) to test the hypothesis that the hydrophobic tunnel formed by these residues influences inhibitor recognition. IC(50) values against OXA-24 and two OXA-24 β-lactamase variants ranged from 10 ± 1 (4 vs WT) to 338 ± 20 nM (5 vs Tyr112Ala, Met223Ala). Compound 4 possessed the lowest K(i) (500 ± 80 nM vs WT), and 1 possessed the highest inactivation efficiency (k(inact)/K(i) = 0.21 ± 0.02 μM(-1)  s(-1)). Electrospray ionization mass spectrometry revealed a single covalent adduct, suggesting the formation of an acyl-enzyme intermediate. X-ray structures of OXA-24 complexed to four inhibitors (2.0-2.6 Å) reveal the formation of stable bicyclic aromatic intermediates with their carbonyl oxygen in the oxyanion hole. These data provide the first structural evidence that 6-alkylidene-2'-substituted penicillin sulfones are effective mechanism-based inactivators of class D β-lactamases. Their unique chemistry makes them developmental candidates. Mechanisms for class D hydrolysis and inhibition are discussed, and a pathway for the evolution of the BlaR1 sensor of Staphylococcus aureus to the class D β-lactamases is proposed.

Histology classification is not a predictor of clinical outcomes in advanced non-small cell lung cancer (NSCLC) treated with vinorelbine or gemcitabine combinations

BACKGROUND

Until recently, histology has not been clearly or consistently described in the literature as a prognostic or predictive variable in advanced NSCLC studies. We have categorised patients treated with vinorelbine and gemcitabine based first line chemotherapy regimes for advanced NSCLC as either squamous or non-squamous, and also as either adenocarcinoma and non-adenocarcinoma, and compared outcome.

MATERIAL AND METHODS

420 patients treated with platinum/gemcitabine, platinum/vinorelbine or single agent gemcitabine or vinorelbine as first line chemotherapy for advanced NSCLC were identified. The influence of pathology on progression free survival (PFS) and overall survival (OS) has been investigated by means of a Cox regression analysis. Hazard ratios with 95% CIs have been given for each pathological type after adjusting for the effects of age, gender, stage (III vs. IV), PS (0/1 vs. 2/3) and treatment type (platinum doublet vs. single agent).

RESULTS

Neither univariate nor multivariate analysis suggested that there was a significant difference in the response rates for adenocarcinoma vs. non-adenocarcinoma or between squamous and non-squamous pathology. There was no difference in PFS between adenocarcinoma and non-adenocarcinoma pathologies until 8 months (p = 0.98), and there was a statistically significant advantage in PFS for squamous vs. non-squamous pathologies (p = 0.04). Using multivariate Cox regression analysis to adjust for the effects of age, gender, stage, PS, and treatment type, the pathology subtype was not significant. There was no difference in OS in any group.

CONCLUSIONS

These results suggest that histology may not be considered as a predictor of clinical outcome using these drugs.

Why clinically used tazobactam and sulbactam are poor inhibitors of OXA-10 beta-lactamase: Raman crystallographic evidence

The clinically used inhibitors tazobactam and sulbactam are effective in the inhibition of activity of class A beta-lactamases, but not for class D beta-lactamases. The two inhibitors exhibit a complex multistep profile for their chemistry of inhibition with class A beta-lactamases. To compare the inhibition profiles for class A and D enzymes, the reactions were investigated within OXA-10 beta-lactamase (a class D enzyme) crystals using a Raman microscope. The favored reaction pathway appears to be distinctly different from that for class A beta-lactamases. In contrast to the case of class A enzymes that favor the formation of a key enamine species, the OXA-10 enzyme forms an alpha,beta-unsaturated acrylate (acid or ester). Quantum mechanical calculations support the likely product as the adduct of Ser115 to the acrylate. Few enamine-like species are formed by sulbactam or tazobactam with this enzyme. Taken together, our results show that the facile conversion of the initial imine, formed upon acylation of the active site Ser67, to the cis- and/or trans-enamine is disfavored. Instead, there is a significant population of the imine that could either experience cross-linking to a second nucleophile (e.g., Ser115) or give rise to the alpha,beta-unsaturated product and permanent inhibition. Alternatively, the imine can undergo hydrolysis to regenerate the catalytically active OXA-10 enzyme. This last process is the dominant one for class D beta-lactamases since the enzyme is not effectively inhibited. In contrast to sulbactam and tazobactam, the reactions between oxacillin or 6alpha-hydroxyisopropylpenicillinate (both substrates) and OXA-10 beta-lactamase appear much less complex. These compounds lead to a single acyl-enzyme species, the presence of which was confirmed by Raman and MALDI-TOF experiments.

Rational design of a beta-lactamase inhibitor achieved via stabilization of the trans-enamine intermediate: 1.28 A crystal structure of wt SHV-1 complex with a penam sulfone

beta-Lactamases are one of the major causes of antibiotic resistance in Gram negative bacteria. The continuing evolution of beta-lactamases that are capable of hydrolyzing our most potent beta-lactams presents a vexing clinical problem, in particular since a number of them are resistant to inhibitors. The efficient inhibition of these enzymes is therefore of great clinical importance. Building upon our previous structural studies that examined tazobactam trapped as a trans-enamine intermediate in a deacylation deficient SHV variant, we designed a novel penam sulfone derivative that forms a more stable trans-enamine intermediate. We report here the 1.28 A resolution crystal structure of wt SHV-1 in complex with a rationally designed penam sulfone, SA2-13. The compound is covalently bound to the active site of wt SHV-1 similar to tazobactam yet forms an additional salt-bridge with K234 and hydrogen bonds with S130 and T235 to stabilize the trans-enamine intermediate. Kinetic measurements show that SA2-13, once reacted with SHV-1 beta-lactamase, is about 10-fold slower at being released from the enzyme compared to tazobactam. Stabilizing the trans-enamine intermediate represents a novel strategy for the rational design of mechanism-based class A beta-lactamase inhibitors.

Sulbactam forms only minimal amounts of irreversible acrylate-enzyme with SHV-1 beta-lactamase

Sulbactam is a mechanism-based inhibitor of beta-lactamase enzymes used in clinical practice. It undergoes a complex series of chemical reactions in the active site that have been studied extensively in the past three decades. However, the actual species that gives rise to inhibition in a clinical setting has not been established. Recent studies by our group, using Raman microscopy and X-ray crystallography, have found that large quantities of enamine-based acyl-enzyme species are present within minutes in single crystals of SHV-1 beta-lactamases which can lead to significant inhibition. The enamines are formed by breakdown of the cyclic beta-lactam structures with further transformations leading to imine formation and subsequent isomerization to cis and/or trans enamines. Another favored form of inhibition arises from attack on the imine by a second nucleophilic amino acid side chain, e.g., from serine 130, to form a cross-linked species in the active site that can degrade to an acrylate-like species irreversibly bound to the enzyme. Thus, the imine is at a branch point on the reaction pathway. Using sulbactam and 6,6-dideuterated sulbactam we follow these alternate paths in WT and E166A SHV-1 beta-lactamase by means of Raman microscopic studies on single enzyme crystals. For the unlabeled sulbactam, the Raman data show the presence of an acrylate-like species, probably 3-serine acrylate, several hours after the reaction is started in the crystal. However, for the 6,6-dideutero analogue the acrylate signature appears on the time scale of minutes. The Raman signatures, principally an intense feature near 1530 cm-1, are assigned based on quantum mechanical calculations on model compounds that mimic acrylate species in the active site. The different time scales observed for acrylate-like product formation are ascribed to different rates of reaction involving the imine intermediate. It is proposed that for the unsubstituted sulbactam the conversion from imine to enamine, which involves breaking a C-H bond, is aided by quantum mechanical tunneling. For the 6,6-dideutero-sulbactam the same step involves breaking a C-D bond, which has little or no assistance from tunneling. Consequently the conversion to enamines is slower, and a higher population of imine results, presenting the opportunity for the competing reaction with the second nucleophile, serine 130 being the prime candidate. The hydrolysis of the resulting cross-linked intermediate leads to the observed rapid buildup of the acrylate product in the Raman spectra from the dideutero analogue. The protocol used here, essentially running the reactions with the two forms of sulbactam in parallel, provides an element of control and enables us to conclude that, for the unsubstituted sulbactam, the formation of the cross-linked intermediate and the final irreversible acrylate product is not a significant route to inhibition of SHV-1.

Efficient inhibition of class A and class D beta-lactamases by Michaelis complexes

A 6-alkylidiene penam sulfone, SA-1-204, is an efficient inhibitor of both SHV-1 and OXA-1 beta-lactamases with K(I) = 42 +/- 4 nm and 1.0 +/- 0.1 microm, respectively. To gain insight into the reaction chemistry of SA-1-204, the reactions between this inhibitor and SHV-1 and OXA-1 were studied by Raman spectroscopy in single crystals and in solution. Raman signatures characteristic of the unreacted beta-lactam ring show that in both phases the inhibitor binds as a noncovalent Michaelis-like complex. This complex is present as the major population for periods of up to an hour. On longer time scales, the Raman data show that beta-lactam ring opening eventually leads to a complex mixture of reaction products. However, the data clearly demonstrate that the key species for inhibition on the time scale of bacterial half-lives is the noncovalent complex preceding acylation.