Target In Multiple Myeloma Research Articles

Abstract 660: OPN-6602, a potent dual EP300/CBP bromodomain inhibitor, targets multiple myeloma through concomitant suppression of IRF4 and c-MYC

Abstract Multiple myeloma (MM) is an aggressive hematological cancer derived from malignant plasma cells in the bone marrow. E1A-binding protein (EP300) and CREB-binding protein (CBP) are transcription coactivators that contain both epigenetic writer histone acetyltransferase (HAT) and reader bromo- (BRD) domains that regulate transcription of genes via chromatin remodeling. EP300/CBP inhibition causes cell cycle arrest and apoptosis in MM through suppression of interferon regulatory factor (IRF4) and concomitant repression of c-MYC, rendering EP300/CBP as a novel target for MM. OPN-6602 is a potent, selective, and orally active small molecule dual EP300/CBP inhibitor discovered through structure guided drug design. Its binding interaction exhibits low nM activity on EP300 (Kd= 1.5 nM) and CREBBP (Kd= 1 nM), with > 200-fold less activity against BRD4. OPN-6602 binding to EP300 is particularly potent by Surface Plasmon Resonance analysis, displaying a Kd of 0.87 nM, with a fast association rate (1.5 E+06/Ms) and a slow dissociation rate (1.3 E-03/s) with a residence time of 13 min. It potently inhibits cell growth in MM cell lines OPM-2 (IC50 ~ 4 nM) and MM.1S (IC50 ~ 47 nM) as well as histone acetylation (IC50 ~ 2 nM) via BRD intramolecular modulation of HAT activity. OPN-6602 demonstrated potent inhibition of H3K27Ac in both LK2 (CBP-deficient lung cancer cells, IC50 = 11 nM) and in OPM-2 (IC50 = 1.6 nM). OPN-6602 also potently inhibited H3K27ac expression in PBMCs with IC50s of 0.75 and 1.4 nM, respectively. The effects of OPN-6602 with dexamethasone (dex) or lenalidomide (len) on the growth of OPM-2 and MM1.S cells were evaluated in a matrix combination study. As single agents, maximal growth inhibition reached 60-75% following dex treatment and only 30-40% following len treatment. In vitro combination studies utilizing a systematic assessment of a broad range of OPN-6602 concentrations in combination with dex or len demonstrated strong synergy. Synergy was observed between OPN-6602 at 3.7 nM and len through a concentration range from 0.027 to 20 µM. Synergy was observed with 1.2 or 3.7 nM of OPN-6602 in combo with dex concentrations from 0.055 to 40 µM. In the OPM-2 xenograft model, OPN-6602 inhibits tumor growth by 30-111% at doses from 2.5-60 mg/kg QD. This growth inhibition correlated with downregulation of IRF4 and cMYC in tumor samples analyzed by QPCR analysis. The pharmacokinetic profile is favorable for oral QD dose administration due to a high Cmax (19 µg/mL at 24 mg/kg) and short half-life (T1/2 = 1.5 hr). A first-in-human study of OPN-6602 in patients with MM is planned for 2024. Citation Format: Bernice Matusow, Wayne Spevak, Chao Zhang, Yan Ma, Rafe Shellooe, James Tsai, Pei Pei Li, Pan Yu Chen, Gaston Habets, Christine Nichols, Parmveer Singh, Kerry Inokuchi, Jackie Walling, Jason Halladay, Gideon Bollag. OPN-6602, a potent dual EP300/CBP bromodomain inhibitor, targets multiple myeloma through concomitant suppression of IRF4 and c-MYC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 660.

Abstract 1318: Targeting multiple myeloma with BCMA-CAR NK cells expressing a GPRC5D-NKG2D bispecific antibody

Abstract Recently developed therapeutics for multiple myeloma (MM) include targeted therapy, immunomodulatory drugs, and immunotherapy, the latter of which consists of B-cell maturation antigen (BCMA)-CAR cells, bispecific antibodies (BsAbs) to engage T cells. However, challenges including relapse and toxicity still exist. The orphan G protein-coupled receptor, class C group 5 member D (GPRC5D), emerged as a novel target for MM therapy. Therefore, following our established system [Cancer Immunol Res PMID: 29769244; Leukemia, PMID:24067492], we generated a BsAb by fusing anti-GPCR5D single-chain variable fragment (scFv) and an anti-NKG2D scFv (GPRC5D-NKG2D BsAb) in a human IgG4 platform and expressed it from BCMA-CAR and soluble IL15 natural killer (NK) cells (s15.BsAb.BCMA-CAR NK) to address the current known limitations. Our data showed that s15.BsAb.BCMA-CAR NK cells secreted GPRC5D-NKG2D BsAb both in vitro and in vivo. To evaluate the function of GPRC5D- NKG2D BsAb expressed from NK cells in vivo, we treated MM tumor-bearing mice with the purified antibody. The data showed that GPRC5D-NKG2D BsAb demonstrated a significantly better survival effect than saline (P≤0.01). We tested s15.BsAb.BCMA-CAR NK cells for cytotoxicity against a homogenous tumor cell mode (BCMA + GPRC5D + ) and a heterogeneous MM tumor cell model, including 50% BCMA + GPRC5D + , 25% BCMA ─ GPRC5D + , and 25% BCMA + GPRC5D ─ cells. Real-time cell analysis (RTCA) data showed s15.BsAb.BCMA-CAR NK cells killed tumor cells in vitro better than both BCMA-CAR NK cells and empty vector-transduced NK cells in an antigen-dependent manner. To test the efficacy of s15.BsAb.BCMA-CAR NK cells in vivo, we established a heterogeneous MM tumor cell mouse model, by mixing BCMA + GPRC5D + OPM2 cells and BCMA + GPRC5D ─ OPM2 cells at the ratio of 2:1. MM mice were treated with “off-the-shelf” different construct NK cells. The results showed that s15.BsAb.BCMA-CAR NK cells significantly prolonged survival compared to other NK cells(s15.BsAb.BCMA-CAR vs. BCMA-CAR P = 0.0012). Our data demonstrated that this all-in-one, multifaceted modality provides 2 ready-to-use biologics simultaneously, CAR NK cells and BsAb, for MM treatment. Citation Format: Lei Tian, Victoria Chen, Tasha Barr, Zhiyao Li, Yuqing Chen, Jiaying Zhang, Michael A. Caligiuri, Jianhua Yu. Targeting multiple myeloma with BCMA-CAR NK cells expressing a GPRC5D-NKG2D bispecific antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1318.

Nicotinamide-Expanded Allogeneic Natural Killer Cells with CD38 Deletion, Expressing an Enhanced CD38 Chimeric Antigen Receptor, Target Multiple Myeloma Cells.

Natural killer (NK) cells are a vital component of cancer immune surveillance. They provide a rapid and potent immune response, including direct cytotoxicity and mobilization of the immune system, without the need for antigen processing and presentation. NK cells may also be better tolerated than T cell therapy approaches and are susceptible to various gene manipulations. Therefore, NK cells have become the focus of extensive translational research. Gamida Cell's nicotinamide (NAM) platform for cultured NK cells provides an opportunity to enhance the therapeutic potential of NK cells. CD38 is an ectoenzyme ubiquitously expressed on the surface of various hematologic cells, including multiple myeloma (MM). It has been selected as a lead target for numerous monoclonal therapeutic antibodies against MM. Monoclonal antibodies target CD38, resulting in the lysis of MM plasma cells through various antibody-mediated mechanisms such as antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity, and antibody-dependent cellular phagocytosis, significantly improving the outcomes of patients with relapsed or refractory MM. However, this therapeutic strategy has inherent limitations, such as the anti-CD38-induced depletion of CD38-expressing NK cells, thus hindering ADCC. We have developed genetically engineered NK cells tailored to treat MM, in which CD38 was knocked-out using CRISPR-Cas9 technology and an enhanced chimeric antigen receptor (CAR) targeting CD38 was introduced using mRNA electroporation. This combined genetic approach allows for an improved cytotoxic activity directed against CD38-expressing MM cells without self-inflicted NK-cell-mediated fratricide. Preliminary results show near-complete abolition of fratricide with a 24-fold reduction in self-lysis from 19% in mock-transfected and untreated NK cells to 0.8% of self-lysis in CD38 knock-out CAR NK cells. Furthermore, we have observed significant enhancements in CD38-mediated activity in vitro, resulting in increased lysis of MM target cell lines. CD38 knock-out CAR NK cells also demonstrated significantly higher levels of NK activation markers in co-cultures with both untreated and αCD38-treated MM cell lines. These NAM-cultured NK cells with the combined genetic approach of CD38 knockout and addition of CD38 CAR represent a promising immunotherapeutic tool to target MM.

Development of the First SEMA4A CAR-T Cell Targeting Multiple Myeloma

Development of the First SEMA4A CAR-T Cell Targeting Multiple Myeloma

Targeting multiple myeloma with nanobody-based heavy chain antibodies, bispecific killer cell engagers, chimeric antigen receptors, and nanobody-displaying AAV vectors.

Nanobodies are well suited for constructing biologics due to their high solubility. We generated nanobodies directed against CD38, a tumor marker that is overexpressed by multiple myeloma and other hematological malignancies. We then used these CD38-specific nanobodies to construct heavy chain antibodies, bispecific killer cell engagers (BiKEs), chimeric antigen receptor (CAR)-NK cells, and nanobody-displaying AAV vectors. Here we review the utility of these nanobody-based constructs to specifically and effectively target CD38-expressing myeloma cells. The promising results of our preclinical studies warrant further clinical studies to evaluate the potential of these CD38-specific nanobody-based constructs for treatment of multiple myeloma.

From Nature to Synthetic Compounds: Novel 1(N),2,3 Trisubstituted-5-oxopyrrolidines Targeting Multiple Myeloma Cells.

The insurgence of drug resistance in treating Multiple Myeloma (MM) still represents a major hamper in finding effective treatments, although over the past decades new classes of drugs, such as proteasome inhibitors and immunomodulatory drugs, have been discovered. Recently, our research team, within a Nature-Aided Drug Discovery project, isolated from Hibiscus Sabdariffa L. calyces the secondary metabolite called Hib-ester which possesses antiproliferative properties against human multiple myeloma RPMI 8226 cells, reduces migration and cell invasion and inhibits proteasome without neurotoxic effects. In the present study, we explored the chemical spaces of the hit compound Hib-ester. We explored the structure-activity relationships (SAR), and we optimized the scaffold through sequentially modifying Hib-ester subunits. Compound screening was performed based on cytotoxicity against the RPMI 8226 cells to assess the potential efficacy toward human MM. The ability of the most effective molecules to inhibit the proteasome was evaluated and the binding mode of the most promising compounds in the proteasome chymotrypsin binding pocket was deciphered through molecular modeling simulations. Compounds 13 and 14 are more potent than Hib-ester, demonstrating that our strategy was suitable for the identification of a novel chemotype for developing possible drug candidates and hopefully widening the drug armamentarium against MM.

Venetoclax Reverses Metabolic Reprogramming Induced By S1P Modulator FTY720, Suppresses Oxidative Phosphorylation and Synergistically Targets Multiple Myeloma

Patients with multiple myeloma (MM) invariably relapse with chemotherapy-resistant disease, underscoring the need for new therapeutic modalities that bypass these resistance mechanisms. FTY720, also known as fingolimod, is an S1P modulator approved by the FDA to treat the relapsing form of multiple sclerosis. Previously we reported that FTY720 exhibits potent anti-myeloma effect in vitro and in vivo in disseminated xenograft model of MM (Beider et al., Clin Cancer Res 2017). Cytotoxic activity of FTY720 was associated with down-regulation of anti-apoptotic protein MCL-1 while not affecting BCL-2 levels. It is therefore conceivable that BCL-2 inhibition using BH3-mimetic venetoclax may improve responses to FTY720.Incubation of human MM cell lines (n=8) and primary MM cells (n=3) with venetoclax and FTY720 combination synergistically potentiated cell death (CI<0.02), regardless of the MM cells t (11; 14) status. The robust apoptosis induced by venetoclax /FTY720 treatment was accompanied by cytochrome C release, activation of caspase-3 and extensive DNA damage, demonstrated by increased TUNEL staining and elevated levels of phosphorylated histone H2AX, respectively . These effects were associated with down-regulation of BCL-2 protein, stabilization of pro-apoptotic Bak protein, loss of mitochondrial membrane potential, ER stress induction, and inhibition of the AKT/mTOR signaling pathway. Furthermore, the venetoclax /FTY720 combination markedly induced mitochondrial calcium flux and mitochondrial ROS generation.Corresponding with mitochondrial destabilization, venetoclax/FTY720 combination promoted the release of apoptosis-inducing factor (AIF) from the mitochondria to the cytosol and subsequently increased AIF nuclear localization, suggesting its functional role in the execution phase of the apoptosis in response to the dual treatment. AIF is a mitochondrial oxidoreductase that contributes to cell death programs and participates in the assembly of the respiratory chain. Of note, single-agent treatment with FTY720 profoundly up-regulated mitochondrial AIF levels. Given the regulative role of AIF in mitochondrial bioenergetics, we could suggest that increased mitochondrial levels of AIF upon FTY720 exposure may support adaptive responses and promote MM survival upon mitochondrial stress. We thus investigated a possible effect of venetoclax and FTY720 separately or in combination on the metabolic activity of MM cells, observing distinct metabolic profiles of single versus combined exposures. FTY720 significantly suppressed glycolysis, down-regulating the transcript levels of the glycolytic enzymes HK2, PDK1, and LDHA. Glycolytic suppression may result in upregulation of mitochondrial content, which maintains cell survival. In accordance, increased mitochondrial activity was detected in FTY720-treated MM cells, detected by high uptake of MitoSpy Red, a dye that stains mitochondria in a membrane potential-dependent manner. To determine if the changes in the mitochondrial content also altered mitochondrial function, bioenergetic analysis was undertaken. FTY720-treated MM cells demonstrated increased levels of NDUFB8 and UQCRC2 (subunits of mitochondrial respiratory complexes I and III, respectively). Furthermore, FTY720 exposure up-regulated ATP production, suggesting an increase in tumor-protective oxidative phosphorylation (OXPHOS). In agreement, inhibition of mitochondrial electron transport chain using rotenone sensitized MM cells to FTY720, synergistically promoting cell death.Notably, co-treatment with venetoclax effectively reversed the metabolic changes mediated by FTY720, reducing mitochondrial mass, suppressing mitochondrial activity and strongly down-regulating the pathways related to OXPHOS. Furthermore, venetoclax/FTY720 combination significantly reduced glutathione (GSH) levels, therefore suppressing antioxidative cell responses.To conclude, we unveil venetoclax role in the metabolic regulation in MM cells. Venetoclax reverses metabolic reprogramming induced by FTY720, suppresses mitochondrial respiration, induces vigorous mitochondrial damage and preferentially targets MM cells in combination with FTY720. These findings may provide the scientific basis for a novel combinatorial anti-myeloma therapy. [Display omitted] DisclosuresPeled: Biokine Therapeutics Ltd: Current Employment; Gamida Cell: Research Funding.

Activated and Expanded Natural Killer Cells Expressing an NKG2D-CAR Efficiently Target Multiple Myeloma Cells

Background:Multiple myeloma (MM) remains an incurable disease and new therapeutic venues are required. Immune-based therapies represent a new weapon in the fight against cancer. Natural killer (NK) cells have an important role as natural control of tumor cells. Based on that, we carried out a proof-of-concept phase I clinical trial to make multiple infusions of autologous activated and expanded NK cells (NKAE) together with anti-myeloma drugs in MM (NCT02481934). In spite of the good clinical results, better responses are needed to erradicate MM. Chimeric antigen receptors (CARs) are emerging as a very good treatment strategy against MM. CAR studies have focused on their expression in T cells. However, CAR-NK cells could have lower toxicity and provides a method to redirect these cells more specifically to target refractory cancer. As our group has previously demonstrated an essential role of NKG2D receptor in NK cell cytotoxic activity, the objective of this work was to combine NK cell activation with the expression of an NKG2D-CAR in primary NK cells from MM patients.Methods:NKAE cells were generated by co-culture of peripheral blood mononuclear cell (PBMCs) with the genetically modified and previously irradiated K562 CL9 mIL21 cell line (kindly given by the Nationwide Children's Hospital) at a 1:1.5 ratio, and interleukin-2 at 100 IU/ml. NKAE cells were transduced with NKG2D CARs containing 4-1BB and CD3z signaling domains (kindly provided by the Perelman School of Medicine). The viral supernatant was produced by transient transfection of HEK293T cells with the vector genome plasmid and lentiviral packaging helper plasmids. NKAE expansion and NKG2D-CAR expression were evaluated by flow cytometry based on the percentage of the NK cell population and on the expression of the activating receptor NKG2D. The gating strategy was based on dead/live cells and doublet discrimination. NKAE-CAR in vitro cytotoxicity against MM cell lines was tested by performing 2-hour europium-TDA release assays.Results:NKAE cells were expanded during 10 days, after that transduction was performed using MOI=5. Better transduction efficiency was found on purified NKAE cells (100% purity) than on NKAEs which were not purified (purity higher than 80%). One day after transduction purified NKAE cells show an increase of NKG2D positive cells (62,6%±12,2%) when compare with untransduced NKAE cells (n=4). NKAE-CAR cells had similar viability as the untransduced NKAE cells. NKG2D-CAR expression was monitored 72 hours after transduction, 24% of NKG2D positive cells was due to episomal expression (38,5%±1,54%) but remain stable up to 7 days (36,8±11,06%). NKAE-CAR in vitro cytotoxic activity was tested at different NKAE-CAR:MM cells ratio (1:8 up to 32:1) using MM L-363 cell line as target (n=4). NKG2D CAR-expressing NKAE cells showed significantly higher cytotoxic activity against myeloma cells than untransduced NKAE cells even at low ratio. NKAE-CAR cells showed maximum cytotoxic capacity at 8:1 ratio (112%±19,2% lysed MM cells), however untransduced NKAE cells showed maximum activity at 32:1 ratio (67,5%±15,8%). At same ratio (8:1), NKAE-CAR cells were able to destroy 112% (±19,2%) MM cells, 53,75% more than untransduced NKAE cells. At very low ratio (1:8) NKG2D-CAR expressing NKAE cells could destroy 42,4% (±2,4%) MM cells.Conclusions:Primary NK cells from MM patients can be activated and transduced in vitro with an NKG2D CAR showing higher cytotoxic activity that untransduced NKAE cells. These results warrant further development of NKAEs-CAR as a new treatment modality for refractory MM. DisclosuresLee:Miltenyi: Speakers Bureau; Courier Therapeutics, Inc: Membership on an entity's Board of Directors or advisory committees; Cyto-Sen Therapeutics, Inc: Other: Founder, Vice President, Medical Director; Intellia Therapeutics, Inc: Consultancy.

Bioactive Compounds from Herbal Medicine Targeting Multiple Myeloma

Multiple myeloma (MM) is one of the most widespread hematological cancers. It is characterized by a clonal proliferation of malignant plasma cells in the bone marrow and by the overproduction of monoclonal proteins. In recent years, the survival rate of patients with multiple myeloma has increased significantly due to the use of transplanted stem cells and of the new therapeutic agents that have significantly increased the survival rate, but it still cannot be completely cured and therefore the development of new therapeutic products is needed. Moreover, many patients have various side effects and face the development of drug resistance to current therapies. The purpose of this review is to highlight the bioactive active compounds (flavonoids) and herbal extracts which target dysregulated signaling pathway in MM, assessed by in vitro and in vivo experiments or clinical studies, in order to explore their healing potential targeting multiple myeloma. Mechanistically, they demonstrated the ability to promote cell cycle blockage and apoptosis or autophagy in cancer cells, as well as inhibition of proliferation/migration/tumor progression, inhibition of angiogenesis in the tumor vascular network. Current research provides valuable new information about the ability of flavonoids to enhance the apoptotic effects of antineoplastic drugs, thus providing viable therapeutic options based on combining conventional and non-conventional therapies in MM therapeutic protocols.

Targeting Multiple Myeloma through the Biology of Long-Lived Plasma Cells.

Multiple myeloma (MM) is a hematological malignancy of terminally differentiated bone marrow (BM) resident B lymphocytes known as plasma cells (PC). PC that reside in the bone marrow include a distinct population of long-lived plasma cells (LLPC) that have the capacity to live for very long periods of time (decades in the human population). LLPC biology is critical for understanding MM disease induction and progression because MM shares many of the same extrinsic and intrinsic survival programs as LLPC. Extrinsic survival signals required for LLPC survival include soluble factors and cellular partners in the bone marrow microenvironment. Intrinsic programs that enhance cellular fidelity are also required for LLPC survival including increased autophagy, metabolic fitness, the unfolded protein response (UPR), and enhanced responsiveness to endoplasmic reticulum (ER) stress. Targeting LLPC cell survival mechanisms have led to standard of care treatments for MM including proteasome inhibition (Bortezomib), steroids (Dexamethasone), and immunomodulatory drugs (Lenalidomide). MM patients that relapse often do so by circumventing LLPC survival pathways targeted by treatment. Understanding the mechanisms by which LLPC are able to survive can allow us insight into the treatment of MM, which allows for the enhancement of therapeutic strategies in MM both at diagnosis and upon patient relapse.

Actionable Strategies to Target Multiple Myeloma Plasma Cell Resistance/Resilience to Stress: Insights From "Omics" Research.

While the modern therapeutic armamentarium to treat multiple myeloma (MM) patients allows a longer control of the disease, this second-most-frequent hematologic cancer is still uncurable in the vast majority of cases. Since MM plasma cells are subjected to various types of chronic cellular stress and the integrity of specific stress-coping pathways is essential to ensure MM cell survival, not surprisingly the most efficacious anti-MM therapy are those that make use of proteasome inhibitors and/or immunomodulatory drugs, which target the biochemical mechanisms of stress management. Based on this notion, the recently realized discoveries on MM pathobiology through high-throughput techniques (genomic, transcriptomic, and other “omics”), in order for them to be clinically useful, should be elaborated to identify novel vulnerabilities in this disease. This groundwork of information will likely allow the design of novel therapies against targetable molecules/pathways, in an unprecedented opportunity to change the management of MM according to the principle of “precision medicine.” In this review, we will discuss some examples of therapeutically actionable molecules and pathways related to the regulation of cellular fitness and stress resistance in MM.

Lycorine targets multiple myeloma stem cell-like cells by inhibition of Wnt/β-catenin pathway.

Multiple myeloma (MM) is characterised by the proliferation and accumulation of malignant plasma cells in the bone marrow. Despite the progress in treatment over the last few years, MM remains incurable and the majority of patients relapse. MM stem-like cells (MMSCs) have been considered as the main reason for drug resistance and eventual relapse. Currently, therapeutic agents are not enough to eradicate MMSCs, and finding effective strategies to eradicate MMSCs may improve the outcome of patients. Here we showed that lycorine, a natural compound from the Amaryllidaceae species, effectively inhibits the proliferation of myeloma cells from cell lines or patients, mainly through decreasing ALDH1+ cells. Mechanistically, lycorine decreases the MMSC population through inhibition of the Wnt/β-catenin pathway by reducing the β-catenin protein level. Moreover, lycorine could overcome the increasing proportion of ALDH1+ cells caused by bortezomib (BTZ) treatment, and a combination BTZ and lycorine have a synergistic effect on anti-myeloma cells. Furthermore, we found a similar reduction of MMSC characteristics by lycorine in BTZ-resistant MM cells and primary CD138+ plasma cells. Collectively, our findings indicate lycorine as a promising agent to target MMSCs to overcome the drug resistance of BTZ, and that, alone or in combination with BTZ, lycorine is a potential therapeutic strategy for MM treatments.

The CD38low natural killer cell line KHYG1 transiently expressing CD16F158V in combination with daratumumab targets multiple myeloma cells with minimal effector NK cell fratricide.

Multiple myeloma (MM) is a clonal plasma cell malignancy typically associated with the high and uniform expression of the CD38 transmembrane glycoprotein. Daratumumab is a humanized IgG1κ CD38 monoclonal antibody (MoAb) which has demonstrated impressive single agent activity even in relapsed refractory MM patients as well as strong synergy with other anti-MM drugs. Natural Killer (NK) cells are cytotoxic immune effector cells that mediate in vivo tumour immunosurveillance. NK cells also play an important role during MoAb therapy by inducing antibody dependent cellular cytotoxicity (ADCC) via their FcγRIII (CD16) receptor. Furthermore, 15% of the population express a naturally occurring variant of CD16 harbouring a single-point polymorphism (F158V). However, the contribution of NK cells to the efficacy of daratumumab remains debatable as clinical data clearly indicate the rapid depletion of CD38high peripheral blood NK cells in patients upon daratumumab administration. In contrast, CD38low peripheral blood NK cells have been shown to survive daratumumab mediated fratricide in vivo, while still retaining their potent anti-MM cytolytic effector functions ex vivo. Therefore, we hypothesize that transiently expressing the CD16F158V receptor using a "safe" mRNA electroporation-based approach on CD38low NK cells in combination with daratumumab could represent a novel therapeutic option for treatment of MM. In the present study, we investigate a NK cell line (KHYG-1), derived from a patient with aggressive NK cell leukemia, as a platform for generating CD38low NK cells expressing CD16F158V which can be administered as an "off-the-shelf" therapy to target both CD38high and CD38low tumour clones in patients receiving daratumumab.

Development of Exosome-Capturing Antibody-Conjugated Nucleic Acid Medicines Targeting Multiple Myeloma Cells

Nucleic acid medicines including small interfering RNAs (siRNAs) are expected to be next-generation therapies. However, targeted delivery of siRNAs into cancer cells, especially hematological cancer cells, via systemic administration is limited by the lack of efficient and cell-specific delivery systems. We previously demonstrated that cancer cell-derived exosomes are preferentially transfer into their parental cancer cells. Based on this observation, we hypothesized that monoclonal antibody (mAb)-conjugated siRNAs that capture exosomes can efficiently deliver siRNAs into hematological cancer cells (Figure 1). To test this hypothesis, we developed a noncovalent Ab-conjugated siRNA system and confirmed the efficient delivery into multiple myeloma (MM) cells. We selected the surface antigen CD63 to capture MM cell-derived exosomes. An anti-CD63 mAb was thiolated using Traut's reagent and then modified with a linear (D-arginine (Arg))9 (9r) or branched (Arg)18 (9+9r) peptide (vehicle). The anti-CD63 mAb-Arg:siRNA complex was obtained by mixing anti-CD63 mAb-Arg and siRNA in phosphate-buffered saline and incubating the mixture. A gel shift assay showed that the anti-CD63 mAb-linear Arg construct bound to siRNAs in a construct concentration-dependent manner and the optimal vehicle-to-siRNA ratio was 5:1. By contrast, the anti-CD63 mAb-branched Arg construct bound to siRNAs at lower concentrations, and the optimal vehicle-to-siRNA ratio was 1:1-2.5:1. We next examined uptake of fluorescence-labeled siRNAs by OPM-2 MM cells using a confocal microscope. A higher level of siRNAs was delivered using the anti-CD63 mAb-branched Arg construct than using the anti-CD63 mAb-linear Arg construct; therefore, we used the former construct for further experiments. We investigated the knockdown effects of the CD63 mAb-branched Arg construct conjugated with luc siRNA in luciferase-expressing OPM-2 cells (OPM-2-luc cells). Luciferase activity decreased to 55.9% in OPM-2-luc cells following uptake of this construct. We next examined the mRNA transcript levels of MYC and CTNNB1 (β-catenin) mRNA transcript levels by RT-PCR in OPM-2 cells treated with the anti-CD63 mAb-branched Arg construct conjugated with MYC and CTNNB1 siRNAs. Treatment with mAb-conjugated siRNAs at a vehicle-to-siRNA ratio of 1:1 decreased the mRNA transcript levels of MYC and CTNNB1 to 52.5% and 55.3%, respectively (Figure 2). In conclusion, exosome-capturing antibody-conjugated siRNAs are effectively delivered into MM cells via uptake of exosomes by parental cells. We are currently investigating their delivery into other hematological cancer cells. This technology might lead to a breakthrough in drug delivery systems for hematological cancers. Disclosures No relevant conflicts of interest to declare.

Targeting Multiple Myeloma with AMG 424, a Novel Anti-CD38/CD3 Bispecific T-cell–recruiting Antibody Optimized for Cytotoxicity and Cytokine Release

Despite advances in the treatment of multiple myeloma, new therapies are needed to induce more profound clinical responses. T-cell-redirected lysis triggered by bispecific antibodies recruiting T cells to cancer cells is a clinically validated mechanism of action against hematologic malignancies and CD38 is a tumor-associated antigen with near-universal expression in multiple myeloma. Thus, an anti-CD38/CD3 bispecific T-cell-recruiting antibody has the potential to be an effective new therapeutic for multiple myeloma. Anti-CD38/CD3 XmAb T-cell-recruiting antibodies with different affinities for CD38 and CD3 were assessed in vitro and in vivo for their redirected T-cell lysis activity against cancer cell lines, their lower levels of cytokine release, and their potency in the presence of high levels of soluble CD38. Select candidates were further tested in cynomolgus monkeys for B-cell depletion and cytokine release properties. AMG 424 was selected on the basis of its ability to kill cancer cells expressing high and low levels of CD38 in vitro and trigger T-cell proliferation, but with attenuated cytokine release. In vivo, AMG 424 induces tumor growth inhibition in bone marrow-invasive mouse cancer models and the depletion of peripheral B cells in cynomolgus monkeys, without triggering excessive cytokine release. The activity of AMG 424 against normal immune cells expressing CD38 is also presented. These findings support the clinical development of AMG 424, an affinity-optimized T-cell-recruiting antibody with the potential to elicit significant clinical activity in patients with multiple myeloma.

NKG2D-CAR Transduced Primary Natural Killer Cells Efficiently Target Multiple Myeloma Cells

IntroductionImmunotherapy represents a new weapon in the fight against multiple myeloma. Current clinical outcomes using CAR-T cell therapy against multiple myeloma show promise in the eradication of the disease. However, these CARs observe relapse as a common phenomenon after treatment due to the reemergence of neoantigens or negative cells. CARs can also be targeted using non-antibody approaches, including the use of receptors, as NKG2D with a wider range of ligands, and ligands to provide target specificity.Different cell types have been used to improve CAR cell therapy. CAR-T cells are the most commonly used. However, despite its effectiveness, there are still problems to face. The toxicity of the cytokine release syndrome is well known, that is why memory CD45RA- T cells are used to avoid collateral effects, although having lower efficacy. However, CAR-NK cells may have less toxicity and provide a method to redirect these cells specifically to refractory cancer.The objective of this work was to compare the anti-tumor activity of CAR-T, NKAEs and CAR-NK cells from multiple myeloma patients.MethodsThe activated and expanded NK cells (NKAE) were generated by coculture of peripheral blood mononuclear cells with the previously irradiated CSTX002 cell line. The CD45RA- T cells were obtained by depletion with CD45RA magnetic beads and subsequent culture. The NKAE and T were transduced with an NKG2D-CAR with signaling domains of 4-1BB and CD3z. The expansion of NKAE and the expression of NKG2D-CAR were evaluated by flow cytometry based on the percentage of NK cell population and transduction efficiency by the expression of NKG2D. Europium-TDA release assays (2-4 hours) were performed to evaluate in vitro cytotoxic activity. The antitumor activity of the NKAE (n=4) and CD45RA- (n=4) cells against MM U-266 cells was studied. Methylcellulose cultures were performed to assess the activity against the clonogenic tumor cell. In vivo studies were carried out in NSG mice receiving 5.106 of U266-luc MM cells i.v. injected at day 1. At day 4, mice received 15.106 i.v. injected of either CAR-NKAE or untransduced NKAE cells.ResultsIn vitro. The killing activity of primary NKAE cells (n=4) was 86.6% (± 13.9%), considerably higher than that of CD45RA- lymphocytes (16.7% ± 13.6%) from the same patient (n=4). Even CD45RA- T cells from healthy donors (n=4) exhibit lower anti tumoral capacity (28.2% ± 9.7%) than NKAE cells. The transduction with an NKG2D CAR (MOI=5) improved the activity of autologous NKAE cells by 10% (96.4% ± 19%) leading to a nearly complete destruction of U-266 MM cells, and that of CD45RA- allogenic healthy cells in 19% (47.4% ± 12.6%). Nevertheless, CD45RA- autologous T cells transduced with NKG2D-CAR minimally improved their activity by 5.8% (22.5% ± 10.6%). Additionally, the CAR-NKAE cells were able to destroy the clonogenic tumor cell responsible for the progression of the MM from RPMI-8226 cell line. At an 8:1 ratio the CAR-NKAE cells were able to destroy 71.2% ± 2.5% of the clonogenic tumor cells, while the NKAE reached 56.5% ± 2.6% at a maximum ratio of 32: 1. The toxicity of the CAR-NKAE cells on healthy tissue from the same patient was assessed, and no activity against autologous PBMCs was observed, 1,8% at a maximun ratio of 32:1 (effector:target).In vivo. NKAE cells and CAR-NKAE cells were efficient in abrogating MM growth. However, CAR-NKAE cells treatment showed higher efficiency 14 days after tumor cells injection. Forty-two days after tumor cells injection, only animals receiving CAR-NKAE cells treatment remain free of disease (Figure 1).ConclusionsIt is feasible to modify primary NKAE cells and CD45RA- T cells from primary MM cells to safely express an NKG2D-CAR. Our data show that CD45RA- T cells from patients are not effective in vitro against MM even once transduced with our CAR. The resulting CAR-NKG2D NKAE cells are the most appropriate strategy for the destruction of MM in vitro and in vivo in our model. These results form the basis for the development of an NKG2D-CAR NK cell therapy in MM. DisclosuresRio:Rocket Pharmaceuticals Inc: Equity Ownership, Patents & Royalties, Research Funding. Lee:Merck, Sharp, and Dohme: Consultancy; Courier Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; CytoSen Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding. Martinez-Lopez:Janssen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Vivia: Honoraria; Pfizer: Research Funding; BMS: Research Funding; Novartis: Research Funding.

Abstract PR01: Targeting multiple myeloma with universal SLAMF7-specific CAR T-cells

Abstract Background: Recent studies with autologous chimeric antigen receptor (CAR)-redirected T-cells against CD19 have demonstrated long-term durable remissions in patients with B-cell leukemia and lymphoma, indicating that CAR T-cell therapy is a promising approach for refractory malignancies. Signaling lymphocytic activation molecule F7 (SLAMF7, also called CS1) is highly expressed on multiple myeloma (MM) tumor cells and is present in only a subset of hematopoietic cells among normal tissues. Because of its high expression on MM tumor cells and restricted expression in normal cells, SLAMF7 is a potential target for CAR T-cell therapy approach in MM. We had previously demonstrated that allogeneic “off-the-shelf” CAR T-cells lacking the ability to induce graft versus host disease could be generated for universal use by inactivating the TCRα constant (TRAC) gene using TALEN® gene editing technology. We also demonstrated that to minimize the risk of fratricide of SLAMF7-specific CAR+ T-cells, SLAMF7 could be inactivated by TALEN® in the T-cells prior to introduction of the CAR construct (Galetto et al., ASH 2015, Abstract 116). Here, we report the efficacy of these double KO (TRAC and SLAMF7) SLAMF7-specific universal CAR T cells (UCARTCS1) against MM in in vitro and in vivo studies. Methods: We tested the efficacy of UCARTCS1 cells against MM cell lines and primary tumor cells from MM patients for their capacity to specifically a) degranulate when co-cultured with MM tumor cells as determined by CD107a assay, b) lyse MM cell lines and primary MM cells in in vitro cytotoxicity assay, c) produce cytokines in culture supernatants, d) proliferate in presence of MM cells as determined by CFSE proliferation assay, and e) eradicate primary MM tumors in a patient-derived xenograft model as determined by serum tumor immunoglobulin (M-protein) levels and survival analysis. Results: UCARTCS1 but not control double KO T-cells (lacking SLAMF7 CAR) specifically lysed the MM cell line, MM.1S (median, 93% lysis; range, 78-98% with UCARTCS1 vs. median, 17%; range, 15-47% with control T-cells; n=10). UCARTCS1 cells similarly induced significant lysis of tumor cells from primary MM samples (n=10) (median 59%; range, 20-90%) compared to control T cells (median 9%; range, 0-36%). In agreement with this, we observed specific degranulation in both CD4+ and CD8+ UCARTCS1 cells but not control T-cells in presence of MM.1S cells and primary MM tumor cells. In addition, significant and specific proliferation of both CD4+ and CD8+ UCARTCS1 cells but not control T-cells was observed when they were co-cultured with MM.1S or primary MM tumor samples (n=8). Analysis of culture supernatants for ten cytokines (IFN-γ, GM-CSF, IL-2, IL-4, IL-5, IL-6, IL-10, IL-13, IL-17, and TNF-α) showed that UCARTCS1 cells primarily produced IFN-γ and GM-CSF in presence of primary MM tumor cells (n=6), indicating a Th1/Tc1 response. To test the efficacy of UCARTCS1 cells in vivo, we injected 1x106 primary MM tumor cells into human fetal bone implanted under the skin of NSG mice. After the tumor has been established for 6 to 8 weeks and the serum M-protein was sufficiently elevated, mice were treated intravenously with either 10x106 total cells/mouse of UCARTCS1 or control T-cells. Mice treated with control T-cells developed gradual increase in M-protein levels (median, 339 µg/ml; range, 100-700 µg/mL) whereas the M-protein levels rapidly became undetectable in the mice treated with UCARTCS1 cells and remained undetectable until they were euthanized at approximately 50 days after adoptive transfer. Conclusion: Our results demonstrated that UCARTCS1 cells were highly cytotoxic against primary MM tumor cells in both in vitro and in vivo studies. In addition, UCARTCS1 cells specifically degranulated, produced Th1/Tc1 cytokines, and proliferated in response to primary MM tumor cells. These data provide a rationale for evaluating UCARTCS1 cells as a universal “off-the-shelf” allogeneic CART product in patients with MM. This abstract is also being presented as Poster A46. Citation Format: Rohit Mathur, Zheng Zhang, Jin He, Roman Galetto, Agnes Gouble, Isabelle Chion-Sotinel, Stephanie Filipe, Annabelle Gariboldi, Tanooha Veeramachaneni, Elisabet Manasanch, Sheeba Thomas, Hans C. Lee, Krina Patel, Donna Weber, Richard Eric Davis, Robert Orlowski, Julianne Smith, Jing Yang, Sattva S. Neelapu. Targeting multiple myeloma with universal SLAMF7-specific CAR T-cells [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr PR01.

Targeting Multiple Myeloma Cancer Stem Cells with Natural Products - Lessons from Other Hematological Malignancies.

Multiple myeloma is characterized by the accumulation of malignant plasma cells in the bone marrow. Multiple myeloma is the second most frequently diagnosed hematological malignancy, predominantly affecting the elderly. Despite recent advances in the development of novel therapies, multiple myeloma remains an incurable malignancy where the majority of patients relapse, develop resistance, and eventually die from the disease. This has been attributed to the fact that conventional therapy currently in use targets mainly the bulk of tumor cells, but not the tumor-initiating cancer stem cells. Cancer stem cells are a highly resistant subpopulation of cells believed to be responsible for the initiation, progression, metastasis, and relapse of cancer. Enormous efforts have been invested in the characterization of cancer stem cells. These efforts led to the characterization of key cellular signaling pathways responsible for conferring stem cell characteristics including self-renewal, differentiation, migratory, survival, and intracellular detoxification capabilities. Targeting these protective mechanisms offers a valuable strategy that may help combat a major driving force behind cancers. The use of natural products offers a promising therapeutic approach for targeting cancer stem cells. In this review, recent advances achieved in the characterization of cancer stem cells derived from hematological malignancies, with a particular focus on multiple myeloma, are discussed and major natural products that target cancer stem cells are presented. As natural products remain an essential source of novel chemical structures and medicinal leads, the exploitation of this immense reservoir is used to draw lessons in targeting multiple myeloma-cancer stem cells.

Abstract 394: A novel anti-a proliferation-inducing ligand hAPRIL.01A monoclonal antibody targets multiple myeloma cells in the bone marrow microenvironment

Abstract A proliferation-inducing ligand (APRIL), a close member of B-cell-activating factor (BAFF) belonging to the TNF superfamily, is mainly produced by bone marrow (BM) accessory cells to stimulates growth and survival of multiple myeloma (MM) cells. We here characterize molecular mechanisms regulating APRIL activation in the BM microenvironment and further determine whether a novel anti-APRIL monoclonal antibody hAPRIL.01A inhibits its functional sequelae in MM. First, in vitro culture showed that osteoclasts (OC) and macrophages secret significantly higher levels of APRIL than unstimulated CD14+ monocytes and BM stromal cells. All MM cell lines express cell surface BCMA in significantly higher level than TACI (p &amp;lt; 9.06e-15). H929 MM cells (expressing only BCMA, but not TACI), and other MM cell lines were next stimulated with APRIL, in the presence or absence of hAPRIL.01 Ab followed by immunoblotting and TaqMan® Array assays on harvested protein lysates and mRNA. APRIL stimulation activated NF-κB, PI3K/AKT, and ERK1/2 signaling in MM cells. NF-κB-DNA binding activities of p65 and p50 (p52, to a less extent), were significantly upregulated as early as 15 minute after stimulation. Conversely, hAPRIL.01 Ab completely blocked these signaling cascades, consistent with decreased NF-κB-DNA binding activities in BCMA-knock-downed MM cells by shBCMA lentivirus transfection. APRIL further induced pro-survival proteins (Mcl1, Bcl2, BIRC3, XIAP) and MM cell growth-stimulating regulators (CCDN2, CDK4, CDK6, c-myc), which were completely inhibited by hAPRIL.01 Ab. These results correlated with blockade of hAPRIL.01 Ab in APRIL-promoted proliferation and survival of MM cells, in the presence of OCs or macrophages. APRIL also induces adhesion of MM cells to BMSC, which was blocked by hAPRIL.01 Ab. This concurred with hAPRIL.01 Ab-reduced adhesion molecules (CD44, ICAM-1) induced by APRIL. APRIL-increased VEGF-A and PECAM-1 in MM cells was also significantly reduced by this mAb. APRIL-upregulated chemotactic/osteoclast-activating factors (MIP-1α, MIP1β, SDF-1) were also inhibited by this Ab. Other angiogenesis and adhesion/chemoattractant factors were changed in a similar fashion, indicating specific blocking of hAPRIL.01 Ab to APRIL-induced downstream target genes. This mAb further inhibited APRIL-increased viability of plasmacytoid dendritic cells (pDC) and diminished MM cell viability protected by pDC in 3-d cocultures. Finally, hAPRIL.01 specifically overcame APRIL-, but not IL-6, induced protection in lenalidomide- or dexamethasone-treated MM1S and H929 MM cells. This Ab also blocks OC-induced MM cell growth and survival in ongoing SCID-hu model of MM. These studies confirm a constitutive APRIL activation via BCMA and TACI in promoting malignancies of myeloma cells, supporting a novel therapeutics of hAPRIL.01 Ab to target MM in the BM microenvironment. Note: This abstract was not presented at the meeting. Citation Format: Yu-Tzu Tai, Chirag Acharya, Gang An, Mike Y. Zhong, Xiaoyan Feng, Hua Jiang, Hans van Eenennaam, Andrea van Elsas, Nikhil C. Munshi, Kenneth C. Anderson. A novel anti-a proliferation-inducing ligand hAPRIL.01A monoclonal antibody targets multiple myeloma cells in the bone marrow microenvironment. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 394. doi:10.1158/1538-7445.AM2015-394

Isopentenyl pyrophosphate secreted from Zoledronate-stimulated myeloma cells, activates the chemotaxis of γδT cells

γδT cell receptor (TCR)-positive T cells, which control the innate immune system, display anti-tumor immunity as well as other non-immune-mediated anti-cancer effects. γδT cells expanded ex vivo by nitrogen-containing bisphosphonate (N-BP) treatment can kill tumor cells. N-BP inhibits farnesyl pyrophosphate synthase in the mevalonate pathway, resulting in the accumulation of isopentenyl pyrophosphate (IPP), which is a stimulatory antigen for γδT cells. We have previously observed that as they get closer, migrating γδT cells increase in speed toward target multiple myeloma (MM) cells. In the present study, we investigated the γδT cell chemotactic factors involving using a micro total analysis system-based microfluidic cellular analysis device. The addition of supernatant from RPMI8226 MM cells treated with the N-BP zoledronic acid (ZOL) or the addition of IPP to the device induced chemotaxis of γδT cells and increased the speed of migration compared to controls. Analysis of the ZOL-treated RPMI8226 cell supernatant revealed that it contained IPP secreted in a ZOL-dose-dependent manner. These observations indicate that IPP activates the chemotaxis of γδT cells toward target MM cells treated with ZOL.