In vitro activities of thiazolidione derivatives combined with daptomycin against clinical Enterococcus faecium strains

Background Previous reports have demonstrated two thiazolidione derivatives (H2-60 and H2-81) can robustly inhibit the planktonic growth and biofilm formation of S. epidermidis and S. aureus by targeting the histidine kinase YycG. Whereas the antibacterial and anti-biofilm activity of these two thiazolidione derivatives (H2-60 and H2-81) against Enterococcus faecium remains elusive. Here, the pET28a-YycG recombinant plasmid were in vitro expressed in E. coli competent cell BL21 (DE3) and induced to express YycG’ protein (conding HisKA and HATPase_c domain) by 0.5 mM IPTG and was purified by Ni – NTA agarose and then for the autophosphorylation test. Antimicrobial testing and time-killing assay were also be determined. Anti-biofilm activity of two derivatives with sub-MIC concentration towards positive biofilm producers of clinical E. faecium were detected using polystyrene microtiter plate and CLSM. Results The MICs of H2-60 and H2-81 in the clinical isolates of E. faecium were in the range from 3.125 mg/L to 25 mg/L. Moreover, either H2-60 or H2-81 showed the excellent bactericidal activity against E. faecium with monotherapy or its combination with daptomycin by time-killing assay. E. faecium planktonic cells can be decreased by H2-60 or H2-81 for more than 3 × log10 CFU/mL after 24 h treatment when combined with daptomycin. Furthermore, over 90% of E. faecium biofilm formation could markedly be inhibited by H2-60 and H2-81 at 1/4 × MIC value. In addition, the frequency of the eradicated viable cells embedded in mature biofilm were evaluated by the confocal laser microscopy, suggesting that of H2-60 combined with ampicillin or daptomycin was significantly high when compared with single treatment (78.17 and 74.48% vs. 41.59%, respectively, P < 0.01). Conclusion These two thiazolidione derivatives (H2-60 and H2-81) could directly impact the kinase phosphoration activity of YycG of E. faecium. H2-60 combined with daptomycin exhibit the excellent antibacterial and anti-biofilm activity against E. faecium by targeting YycG.

Combination of Three Unique Anti-Tumor Modalities Engineered into iPSC-Derived T Cells Demonstrate a Synergistic Effect in Overcoming Tumor Heterogeneity and Cancer Escape

Chimeric antigen receptor (CAR) is known to trigger an effective immune response through surface antigen recognition enhanced by T-cell activation signal one (ex. CD3) and signal two (ex. CD28); however, targeting neoantigens and intracellular antigens remains a challenge. On the other hand, the T-cell receptor (TCR) can target neo/intracellular antigens presented by MHC molecules, but often the response is not as potent. The CD16 Fc receptor, which is naturally expressed on NK cells, mediates antibody-dependent cellular cytotoxicity (ADCC), but its application in T cells is yet not fully appreciated. Utilizing our proprietary induced pluripotent stem cell (iPSC) platform to engineer multiple modalities into a clonal iPSC line, which can serve as the starting cell source for mass production of off-the-shelf, iPSC-derived CAR-T cells (CAR-iT cells), we aimed to study the combination of these three targeting modalities, CAR, TCR, and CD16 (tri-modal), to determine whether challenges associated with the treatment of heterogeneous tumors may be overcome. To evaluate the benefit of the three distinct targeting modalities, we tested the functional activity of individual and various combinations of i) anti-CD19 CAR, anti-MICA/B CAR, and anti-BCMA CAR, ii) high-affinity, non-cleavable CD16 (hnCD16), and iii) MR1 and NYESO1 TCR modalities in iT cells. All tested combinations successfully expressed the designated edits and differentiated into iT cells (T-lymphocytes &gt; 95%). Initially, we tested CD19 CAR and MR1 TCR in a 9-day serial killing assay of Nalm6 leukemia cells (CD19 high, MR1 +), where we observed CD19 CAR-iT cells induce prompt CAR-mediated tumor growth inhibition (TGI), saw similar effective killing by MR1 TCR-iT cells but with a 24-hr delay, and observed the most effective response of tumor cell elimination when both where combined in the same iT cell population (relative tumor counts; Day 1, no stim: 2.6, CAR: 0.28, TCR: 1.02, CAR+TCR: 0.02; Day 2, no stim: 5.36, CAR: 0.25, TCR: 0.05, CAR+TCR: 0.02). All conditions (CAR, TCR, and CAR+TCR) reached and maintained complete TGI by Day 9 of the assay (relative tumor count, Day 9, no stim: 50.97, all other stim conditions: &lt;0.01). In line with killing kinetics, the time for the activation marker CD25 upregulation differed between CAR and TCR (peak time and percentage of CD25 +, CAR: Day 1, 49.9%; TCR: Day 5, 74.6%). Co-triggering of CAR and TCR in combination revealed quickest, highest, and sustained CD25 upregulation levels (CD25 +, CAR+TCR Day 1: 62.5%, Days 3 to 9: &gt;90%), indicating a synergistic effect and compatibility between CAR and TCR. Assessing anti-MICA/B CAR and hnCD16, we confirmed the hnCD16-mediated response in iT cells in the presence of anti-MICA/B CAR when crosslinking hnCD16 via biotinylated anti-CD16 antibody with streptavidin (phosphorylated CD3zeta peaked at 10 min upon ADCC triggering), indicating the compatibility between a CAR-iT cell and the hnCD16 motif. Lastly, combining iT cells expressing anti-BCMA CAR + MR1 TCR + hnCD16 with daratumumab (anti-CD38 mAb) in a 9-day serial killing assay demonstrated the best TGI among the groups with a near-elimination of transgenic Nalm6 cells (area under curve, no stim: 30.29, TCR: 1.564, CAR: 0.7087, hnCD16+mAb: 1.452, trimodal+mAb: 0.5824). To assess the function of the tri-modal iT cells in vivo, we used a disseminated xenograft model of B-cell leukemia where a heterogenous mixture of transgenic Nalm6 leukemia cells was used to mimic tumor heterogeneity. Assessment of the bone marrow revealed the unique capacity of each target modality to eliminate its target designated Nalm6 leukemia group, with tri-modal iT cells effectively clearing all populations (Figure 1). In summary, using the unique approach to engineer iPSCs at the clonal level to create a distinct population of engineered iT cells, we successfully demonstrated the compatibility between CAR, TCR, and hnCD16 to mitigate tumor heterogeneity. This approach is an ideal strategy to create off-the-shelf cellular immunotherapy for a promising therapeutic approach to combat heterogeneous and difficult to treat solid tumors, including those that are resistant due to antigen escape. Figure 1 Figure 1. Disclosures Yang: Fate Therapeutics, Inc.: Current Employment. Lin: Fate Therapeutics, Inc.: Current Employment. Shirinbak: Fate Therapeutics, Inc.: Current Employment. Pribadi: Fate Therapeutics, Inc.: Current Employment. Chu: Fate Therapeutics, Inc.: Current Employment. Gutierrez: Fate Therapeutics, Inc.: Current Employment. Mehta: Fate Therapeutics, Inc.: Current Employment. Avramis: Fate Therapeutics, Inc.: Current Employment. Whitlock: Fate Therapeutics, Inc.: Current Employment. ORourke: Fate Therapeutics, Inc.: Current Employment. van der Stegen: Fate Therapeutics, Inc.: Current Employment. Lee: Fate Therapeutics, Inc.: Current Employment. Witty: Fate Therapeutics, Inc.: Current Employment. Peralta: Fate Therapeutics, Inc.: Current Employment. Hosking: Fate Therapeutics: Current Employment. Chang: Fate Therapeutics, Inc.: Current Employment. Valamehr: Fate Therapeutics, Inc.: Current Employment.

191 GAPDH knock-in of high affinity CD16 in iPSC derived NK cells drives high-level expression and increased anti-tumor function

BackgroundNatural killer (NK) cells have emerged as an alternative cell type for clinical utility given the low propensity for graft-versus-host disease, thereby making NK cells a potential off-the-shelf cell therapy. One critical pathway NK cells use to target tumor cells is through expression of Fc gamma receptor III alpha (CD16). Antibodies that bind tumor antigens are recognized by CD16 on NK cells, promoting NK-mediated tumor cell killing. High-affinity CD16 variants in the human population correlate with better clinical outcome and anti-tumor response. One mechanism tumors use to evade NK cell recognition is through down-regulation of CD16 expression on the NK cell surface. After being activated, CD16 is cleaved by A Disintigrin and Metalloprotease-17 (ADAM-17). By using a highly-active engineered AsCas12a to knock-in high-affinity CD16 (hCD16KI) at the GAPDH locus, hCD16 is constitutively expressed, continuously replacing hCD16, thereby allowing for repeated ADCC mediated killing.Methods iPSCs were edited at the GAPDH locus with an engineered AsCas12a along with the CD16 donor construct. The bulk edited population was then plated at clonal density and single clones were selected and screened. iPSC clones were then differentiated into NK cells. A 3D tumor spheroid killing assay was used to demonstrate NK cell cytotoxicity against an ovarian cancer cell line (SKOV-3). In addition, a serial killing assay was used to better model NK cell serial killing.ResultsBi-allelic CD16KI iPSC clones were successfully generated. These iPSCs exhibited normal morphology and were able to differentiate into iNK cells. hCD16KI iNK cells showed normal differentiation and surface marker expression, such as CD45/CD56, compared to unedited iNK cells. CD16KI iNK cells demonstrated significantly increased cytotoxicity in the presence of antibody against tumor cells when compared with unedited iNK cells, as measured by reduction in tumor spheroid size in a 3D tumor spheroid killing assay. Importantly, enhanced surface expression of hCD16 on iNK cells after tumor exposure was detected, demonstrating the replenishment of cleaved hCD16. Notably, hCD16KI iNK cells demonstrated prolonged and enhanced tumor cell killing after being subjected to repeated tumor cell exposure in a serial killing assay.ConclusionsThis work demonstrates a powerful new method to drive high-level constitutive hCD16 expression on the surface of iNK cells through transgene knock-in at the GAPDH locus using an engineered AsCas12a. The high level constitutive hCD16 expression enhances ADCC of iNK cells and enables enhanced serial tumor killing and is expected to exert enhanced anti-tumor activity in the clinic.

159 METFORMIN DOWNREGULATES PD-L1 EXPRESSION IN ESOPHAGEAL SQUAMOUS CELL CARCINOMA BY INHIBITING IL-6 SIGNALING PATHWAY

ESCC is an aggressive cancer with poor prognosis in China. Metformin with low cost and toxicity have proved to have anti-cancer effects in many kinds of cancers, while its role in combination of immune checkpoint blockade and mechanism in ESCC has seldom been studied. This study was designed to evaluate the potential role of combinatorial anti-tumor effect with metformin and immunomodulatory monoclonal antibodies (mAbs) targeting programmed cell death protein-1 (PD-1) in vitro and in vivo. Methods Reverse transcription-quantitative polymerase chain reaction, western blot and immunohistochemistry (IHC) assays were used to study the effects of metformin on the expression levels of PD-L1. In addition, T cell activation and killing assay were performed in the co-culture system of ESCC cell and peripheral blood mononuclear cells (PBMCs) treated with metformin or IL-6 to evaluate the function of inhibiting PD-L1 expression. In vivo assay, we used NPIdKOTM mice model, which was re-constructed replaced immune system by transplanting PBMCs through intravenously injecting. Mice were treated with metformin alone as well as in combination with anti-PD-1 mAbs. Results PD-L1 expression were downregulated by metformin via JAK2 and STAT3 signaling pathway. The results showed that metformin promoted CD3/CD28 induced ERK phosphorylation at a dose dependent measure. And IL-2 was increased in the supernatant of KYSE-450/PBMC coculture system after metformin treatment. Both of which are indicators of T cell activation. T cell mediated tumor killing assay showed that metformin inducing PD-L1 downregulation could protect T cell function, and it could be reversed by IL-6. It showed that metformin enhanced its efficacy in TE-7 cells-harboring mice in the combination treatment group, reflected by tumor sizes assay, and in vivo imaging system. Conclusion Various approaches are under way to expand the benefits and improve the efficacy of these immune checkpoint inhibitors. Another approach is combining immunotherapy with existing anticancer therapies. In this regard, we have evaluated the mechanism of metformin inhibiting PD-L1 expression in ESCC. This finding indicated that metformin significantly improved the antitumor effects by anti-PD-1 blockade without detectable toxicity and suggested that metformin has strong potential to be used in combination with immunotherapy.

Preclinical Development of Edit-201, a Multigene Edited Healthy Donor NK Cell with Enhanced Anti-Tumor Function and Superior Serial Killing Activity in an Immunosuppressive Environment

Natural killer (NK) cells distinguish tumor from healthy tissue via multiple mechanisms, including recognition of stress ligands and loss of MHC class I expression. For example, KIR mismatching enables allogenic NK cells to respond to MHC positive tumors in a similar manner to MHC negative tumors, making allogeneic NK cell therapy a promising approach for broad oncology indications. Accordingly, allogenic human HD-NK cells, including gene-modified cells, have demonstrated an impressive safety and efficacy profile when administered to patients with advanced hematologic malignancies. However, effector function of allogeneic NK cells can be diminished by the lack of functional persistence, as well as tumor-intrinsic immunosuppressive mechanisms, such as production of TGF-β. To this end, we developed a next-generation allogeneic NK cell therapy using CRISPR-Cas12a gene editing to enhance NK cell function through knockout of the genes CISH and TGFBR2. Both single and simultaneous targeting (DKO) of TGFBR2 and CISH in NK cells using CRISPR-Cas12a produced in/dels at both targets in greater than 80% of NK cells, with greater than 90% of edited NK cells viable at 72 hours post-editing. Importantly, we find that DKO NK cells do not phosphorylate the SMAD2/3 protein downstream of the TGF-b receptor complex and demonstrate increased phosphorylation of pSTAT3 and pSTAT5 upon IL-15 stimulation, consistent with protein level knockout of TGFBR2 and CISH. To determine whether DKO NK cells exhibited superior function relative to control NK cells, we first measured the ability of DKO NK cells to kill Nalm6 cells (adult B cell ALL) relative to unedited control NK cells. We find that in the presence of exogenous TGF-b, DKO NK cells demonstrate improved cytotoxicity against Nalm6 tumor targets by delaying tumor re-growth in comparison to control NK cells. To better characterize the ability of DKO NK cells to kill tumor cells, we developed an in vitro serial killing assay. In this long-duration assay, up to 30 days, control and DKO NK cells (grown in the presence of IL-15) were challenged every 48 hours with a new bolus of Nalm6 tumor targets. Both DKO and unedited NK cells control Nalm6 target cell growth for greater than 18 days (9 additions of new Nalm6 target cells), demonstrating a surprising ability for the same NK cells to serially kill new Nalm6 target cells for a prolonged period of time in vitro. We find that DKO NK cells produce higher levels of IFN-γ and TNF-α relative to control NK cells over the duration of the entire serial killing assay, suggesting that DKO NK cells can continue to produce these inflammatory cytokines even after serial killing. As many tumors, including hematologic malignancies, have high concentrations of TGF-β in their microenvironments, we next tested the ability of DKO NK cells to control the growth of Nalm6 cells in our serial killing assay in the presence of TGF-b. 10ng/mL TGF-β was added at the start of the assay as well as at each addition of new Nalm6 target cells. We observed that control NK cells fail to restrict Nalm6 target cell growth beyond 4 days (after 1 addition of new Nalm6 target cells) whereas DKO NK cells control Nalm6 target cell growth for greater than 18 days (after 9 additions of new Nalm6 target cells). Similar to the serial killing assay without TGF-b, we find that DKO NK cells produce higher concentrations of IFN-γ and TNF-α relative to control NK cells over the duration of the entire serial killing assay. Broadening our repertoire of target cells beyond B cell malignancies is now in progress, including the AML-like cell lines HL-60 and THP-1, the multiple myeloma cell line RPMI 8226, and various solid tumor targets. In summary, using CRISPR-Cas12a we demonstrated highly efficient gene editing of primary human NK cells at two unique targets designed to augment NK cell anti-tumor activity across a variety of malignancies. Most significantly, we demonstrate sustained anti-tumor serial-killing activity in the presence of the potent immunosuppressive cytokine TGF-β. Together, the increased overall effector function of CISH/TGFBR2 DKO primary human NK cells and their ability to serial kill, support their development as a potent allogeneic cell-based medicine for cancer. This potential medicine, termed EDIT-201, is being advanced to clinical study. Disclosures Borges: Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Wasko:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Nasser:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Donahue:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Pfautz:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Antony:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Leary:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Sexton:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Morgan:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Wong:Editas Medicine: Current Employment, Current equity holder in publicly-traded company.

Generation of Natural Killer Cells with Enhanced Function from a CRISPR/Cas12a-Edited Induced Pluripotent Stem Cell Line

Adoptive cell therapy using T cells to treat cancer is efficacious in a number of hematologic malignancies. Recently, natural killer (NK) cells have emerged as an alternative cell type for clinical utility given the low propensity for graft-versus-host disease, thereby making NK cells a potential off-the-shelf cell therapy. NK cells distinguish tumor from healthy tissue via multiple mechanisms, including recognition of stress ligands and loss of MHC class I expression. For instance, KIR mismatching enables allogenic NK cells to kill MHC-positive tumor cells similar to MHC-negative tumor cells. Effector function of allogeneic NK cells are typically diminished by limited functional persistence, as well as tumor-intrinsic immunosuppressive mechanisms, such as TGF-β, a pleiotropic cytokine that inhibits immune effector function. Gene editing, however, can overcome these biological limitations. We hypothesized that knockout of CISH, a negative regulator of IL-2/IL-15 signaling, would improve NK cell effector function, while knockout of the TGF-β receptor gene 2, TGFBR2, would render NK cells resistant to TGF-β mediated suppression. NK cells are typically isolated from either cord blood or peripheral blood of healthy donors but recent advances with induced pluripotent stem cells (iPSCs) allows a nearly unlimited supply of iPSC-derived natural killer cells (iNK). In this study, we used CRISPR/Cas12a to generate edited iPSC lines that were differentiated into CD56+ iNK cells. Specifically, we generated TGFβR2-/-, CISH-/-, and TGFβR2-/-/CISH-/- iPSC clones with bi-allelic gene disruption confirmed by next generation sequencing. Importantly, we also confirmed that the edited clones were pluripotent. In particular, a minimum of 3 clones from each genotype were differentiated to CD56+ iNK cells. After differentiation, &gt;90% of the cells expressed CD56 for all genotypes. Additionally, we observed the expression of canonical natural killer cell markers such as CD16, NKG2A, KIRs, NKp46, NKp44, and NKp30 within this CD56+ population. We tested the effector function of TGFβR2-/-, CISH-/-, and TGFβR2-/-/CISH-/- iNKs in a variety of molecular and functional assays, including a spheroid killing assay and an in vitro serial killing assay. For example, we utilized a SK-OV-3 spheroid killing assay to determine the intrinsic ability for the iNK cells to kill tumor targets following the differentiation process. TGFβR2-/-, CISH-/-, and TGFβR2-/-/CISH-/- iNKs reduce the size of SK-OV-3 ovarian tumor spheroids more effectively than control iNK cells in the presence of exogenous TGF-β. In conclusion, we have established an iPSC editing platform that can generate a near infinite supply of natural killer cells with enhanced tumor killing function, paving the way for future off-the-shelf cell therapies for application to broad oncology indications. Disclosures Moon: Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Chin:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Burden:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Sexton:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Wasko:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Nasser:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Antony:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Wong:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Borges:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Morgan:Editas Medicine: Current Employment, Current equity holder in publicly-traded company. Welstead:Editas Medicine: Current Employment, Current equity holder in publicly-traded company.

Synergistic interaction of eugenol and antimicrobial drugs in eradication of single and mixed biofilms of Candida albicans and Streptococcus mutans

In vitro eradication of the C. albicans and S. mutans mixed biofilms by eugenol alone and in combination with the antimicrobial drugs. Previously characterized strains of C. albicans (CAJ-01 and CAJ-12) and S. mutans MTCC497 were used to evaluate the eradication of biofilms using XTT reduction assay, viability assay, time dependent killing assay and scanning electron microscopy (SEM). Synergistic interaction was assessed by checkerboard method. Sessile MIC (SMIC) of eugenol was equivalent to the planktonic MIC (PMIC) against C. albicans and S. mutans mixed biofilms. SMIC of fluconazole and azithromycin was increased upto 1000-folds over PMIC. Eradication of single or mixed biofilms was evident from the viability assay and SEM. At 1 × MIC of eugenol, log10CFU count of C. albicans cells were decreased from 6.3 to 4.2 and 3.8 (p < 0.05) in single and mixed biofilms, respectively. SEM studies revealed the eradication of C. albicans and S. mutans cells from glass surface at 800 µg/mL concentration of eugenol. Time dependent killing assay showed dose dependent effect of eugenol on pre-formed CAJ-01, CAJ-12 and S. mutans biofilm cells. Eugenol was highly synergistic with fluconazole (FICI = 0.156) against CAJ-12 single biofilms. However, the combination of eugenol and azithromycin showed maximum synergy (FICI = 0.140) against pre-formed C. albicans and S. mutans mixed biofilms. These findings highlighted the promising efficacy of eugenol in the eradication of biofilms of two oral pathogens (C. albicans and S. mutans) in vitro and could also be exploited in synergy with fluconazole and azithromycin in controlling oral infections.