Multiple myeloma (MM) is a plasma cell disease with a preferential bone marrow (BM) tropism. Enforced expression of tissue-specific chemokine receptors has been shown to successfully guide adoptively-transferred CAR NK cells towards the malignant milieu in solid cancers, but also to BM-resident AML and MM. For redirection towards BM-associated chemokine CXCL12, we armored BCMA CAR-NK-92 as well as primary NK cells with ectopic expression of either wildtype CXCR4 or a gain-of-function mutant CXCR4R334X. Our data showed that BCMA CAR-NK-92 and -primary NK cells equipped with CXCR4 gained an improved ability to migrate towards CXCL12 in vitro. Beyond its classical role coordinating chemotaxis, CXCR4 has been shown to participate in T cell co-stimulation, which prompted us to examine the functionality of CXCR4-cotransduced BCMA-CAR NK cells. Ectopic CXCR4 expression enhanced the cytotoxic capacity of BCMA CAR-NK cells, as evidenced by the ability to eliminate BCMA-expressing target cell lines and primary MM cells in vitro and through accelerated cytolytic granule release. We show that CXCR4 co-modification prolonged BCMA CAR surface deposition, augmented ZAP-70 recruitment following CAR-engagement, and accelerated distal signal transduction kinetics. BCMA CAR sensitivity towards antigen was enhanced by virtue of an enhanced ZAP-70 recruitment to the immunological synapse, revealing an increased propensity of CARs to become triggered upon CXCR4 overexpression. Unexpectedly, co-stimulation via CXCR4 occurred in the absence of CXCL12 ligand-stimulation. Collectively, our findings imply that co-modification of CAR-NK cells with tissue-relevant chemokine receptors affect adoptive NK cell therapy beyond improved trafficking and retention within tumor sites.

Recent improvement in patient outcomes with the use of novel cellular immunotherapies for multiple myeloma (MM) has raised the prospect for the emergence of a curative treatment. While BCMA-targeted chimeric antigen receptor (CAR)-T cell therapies have been successful in treating MM, CAR-T cell manufacturing challenges preventing broad patient access and treatment relapse drive the need for additional targeted therapies with emphasis on multi-antigen targeting and off-the-shelf availability. GPRC5D, a tumor-associated orphan G-protein-coupled receptor found to be highly expressed in MM, is a potentially attractive target that has demonstrated promising clinical benefit when targeted via immunotherapy modalities. Here, we describe the development of FT555, an induced pluripotent stem cell (iPSC)-derived CAR-NK (CAR-iNK) cell product with the unique and effective ability to simultaneously co-target GPRC5D and CD38 (an additional tumor-associated antigen of MM) via combination with daratumumab, and which can be mass produced and is available off-the-shelf to support broad patient access. FT555 is a CAR-NK cell derived from an iPSC master cell line that has been multiplexed-engineered at the clonal level to contain four unique modalities; a novel GPRC5D-specific CAR fine-tuned for NK cell biology; a high-affinity, non-cleavable CD16 (hnCD16) to maximize antibody-dependent cellular cytotoxicity (ADCC) when combined with a monoclonal antibody (mAb); a unique IL-15/IL-15 receptor fusion protein (IL15RF) to promote cytokine-independent function; and CD38 knockout to promote NK cell fitness and uniquely prevent anti-CD38 mAb-mediated fratricide. Sourced from a renewable engineered iPSC master cell line, FT555 is a pure population of engineered NK cells (>95% CD56+) exhibiting uniform expression of CAR-GPRC5D (>90%), hnCD16 (>90%) and IL15RF (>90%), with complete elimination of CD38 expression (not detected). In cytotoxicity assays, FT555 shows antigen specificity, dose-dependent potency and importantly, when combined with the anti-CD38 mAb daratumumab, exhibits resistance to fratricide. In a serial restimulation killing assay, FT555 demonstrates persistent tumor-specific activity against GPRC5D-positive MM.1S WT target cells when compared to isogenic GPRC5D knock-out (KO) targets (70.9% control of tumor by AUC against WT targets vs. 3.5% control against GPRC5D KO targets in the third round of stimulation). When used in combination with daratumumab, FT555 targets CD38 and eliminates CAR-resistant GPRC5D KO target cells (57.1% target killing when combined with daratumumab vs. 3.5% target killing in the absence of mAb in the third round of stimulation), demonstrating the capacity for FT555 to target GPRC5D+ and CD38+ cells through CAR and hnCD16 engagement, respectively. In a disseminated xenograft in vivo model of MM where the MM.1S cell line shows comprehensive tumor engraftment, FT555 demonstrates robust killing kinetics and tumor clearance as a single dose, resulting in control of MM progression for up to 42 days and increased survival to 80 days vs. 37 days for the untreated control arm (Figure 1A, 1B, FT555; 99.9% tumor growth inhibition (TGI) at D37, 151% increased lifespan (ILS)). Durability of FT555 is further enhanced with the addition of daratumumab, where tumor growth inhibition deepened and survival improved, with 2 of 5 mice showing complete clearance of tumor cells at Day 80, demonstrating the synergy of anti-tumor activity between CAR and hnCD16 (Figure 1A, 1B, FT555+Dara; 100% TGI at D37, >207% ILS). Furthermore, in a distinct xenograft model of MM, treatment with FT555 resulted in significantly improved TGI against OPM2 tumor targets (FT555; 100% TGI at D51, p < 0.05). Together these studies demonstrate that FT555 is a multiplexed-engineered CAR-NK cell derived from a clonal master iPSC line, which utilizes the intrinsic versatility of NK cells to enable a highly effective combination therapy with daratumumab to simultaneously target both GPRC5D and CD38 in a single, standardized, and scalable off-the-shelf platform. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Resistance to CAR-T cell therapy through antigen loss and clonal heterogeneity is a major limiting factor in achieving durable responses, even in highly persistent cell therapies. Simultaneous targeting of multiple tumor antigens with a single therapeutic modality offers the potential to treat heterogeneous tumor populations, prevent antigen escape, and induce durable clinical remission. Here, we demonstrate the application of a unique dual-CAR approach simultaneously targeting two tumor associated antigens (TAA) for the treatment of multiple myeloma (MM) using an off-the-shelf induced pluripotent stem cell (iPSC) derived NK cell platform. The iPSC background has been functionally enhanced and can be combined with therapeutic antibodies. A CAR targeting B cell maturation antigen (BCMA), a well-defined TAA in MM, was designed utilizing a previously published high-affinity binding sequence shown to exhibit high selectivity to BCMA with enhanced recognition of low-BCMA expressing myeloma cells (Bluhm et al., Molec Ther 2018). This CAR was combined with a companion CAR targeting the pan-TAAs, MICA and MICB. The CAR binding sequence targets the conserved α3 domain of MICA/MICB, which we have previously shown to inhibit MICA/B shedding by blocking the putative cleavage site (Andrade et al., Science 2018). The designed anti-MICA/B-α3 CAR exhibits selective targeting potential against a broad range of tumor types. To determine the suitability of co-targeting BCMA and MICA/B in MM, we surveyed surface expression of BCMA and MICA/B on a variety of MM cancer cell lines and observed a complimentary pattern of co-expression compatible with a dual-CAR to broaden the targeting approach of malignant plasma cells. In a reductionist approach, dual CAR-iNK cells exhibited antigen-specific activation, degranulation and cytotoxicity against a Nalm6 target line constitutively expressing the BCMA and MICA/B. Similar trends were observed in a series of long-term cytotoxicity assays against several MM lines, consistent with antibody staining on target cells, illustrating that co-targeting of MICA/B and BCMA expands the breadth of coverage against MM. Known modulators of antigen expression were tested for their ability to provide further depth of response, and therapeutic antibodies such as anti-CD38 were tested in combination to exploit the non-cleavable CD16 and CD38KO edits in the iPSC backbone. These combinations were further tested in vivo against a disseminated model of multiple myeloma where BCMA/MICA dual CAR-iNK cells demonstrated superior tumor control relative to single-CAR controls, and TGI was augmented with the addition of Daratumamab. These data highlight the applicability of a multi-targeted approach in MM patients, whereby MM dual-CAR NK and/or T cells maintain responsiveness to malignant cells that shed or downregulate tumor antigens to evade treatment. Citation Format: Ketan Mathavan, John Reiser, Sajid Mahmood, Yijia Pan, Bryan Hancock, Robert Blum, Wen-I Yeh, Andrew Houk, Chia-Wei Chang, Tom Lee, Bobby Goulding, Jode Goodridge, Ryan Bjordahl, Bahram Valamehr, Uta Hoepken, Armin Rehm, Kai Wucherpfennig. Combining dual CAR iPSC-derived immune cells with antibody for multi-antigen targeting to overcome clonal resistance in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4190.

Chimeric antigen receptor (CAR) T-cell therapy has proven highly effective in patients with hematological malignancies. However, resistance to CAR-T cell therapy arising from target protein shedding and other forms of antigen downregulation can lead to CAR-resistant disease relapse. Tumor escape may be successfully prevented through the simultaneous targeting of multiple tumor antigens. The ability to target multiple antigens with a single therapeutic modality offers the potential for anti-tumor responses, broader coverage of heterogeneous tumor populations, and the potential to prevent antigen escape, potentially inducing durable clinical remission. Multiple myeloma (MM) presents an ideal case to employ a dual-CAR approach, as BCMA-targeting cell therapies have shown impressive efficacy to date, but curative treatment remains elusive. Additionally, the oligoclonal nature of MM may contribute to antigen escape and clonal resistance. Here, we demonstrate the application of a unique dual-CAR approach simultaneously targeting two tumor associated antigens (TAA) for the treatment of MM. We further demonstrate the efficacy in an induced pluripotent stem cell (iPSC) platform, where a master engineered iPSC line is used as the starting material for mass production of off-the-shelf, dual-CAR immune effector cells.

Allogeneic off-the-shelf cell therapies offer distinct advantages over conventional autologous cell therapies in terms of scaled manufacturing, on-demand availability and optimization of cellular starting material. A unique consideration in the use of allogeneic cell therapies is the potential for immune cell-mediated recognition of the allogeneic cell product by the patient's immune system. CAR T-cell therapies are commonly combined with conditioning chemotherapies that suppress a patient's immune system, creating a suitable window of activity to elicit clinical response. However, protracted lympho-conditioning also affects immune reconstitution and can negatively impact the rate of infection. Alternative approaches to prevent allorejection may therefore help to enhance the efficacy of the therapy while preserving the immune system of the patient.

Protein glycosylation plays essential roles in protein structure, stability and activity such as cell adhesion. The cadherin superfamily of adhesion molecules carry O-linked mannose glycans at conserved sites and it was recently demonstrated that the TMTC1-4 genes contribute to the addition of these O-linked mannoses. Here, biochemical, cell biological and organismal analysis was used to determine that TMTC3 supports the O-mannosylation of E-cadherin, cellular adhesion and embryonic gastrulation. Using genetically engineered cells lacking all four TMTC genes, overexpression of TMTC3 rescued O-linked glycosylation of E-cadherin and cell adherence. The knockdown of the Tmtcs in Xenopus laevis embryos caused a delay in gastrulation that was rescued by the addition of human TMTC3. Mutations in TMTC3 have been linked to neuronal cell migration diseases including Cobblestone lissencephaly. Analysis of TMTC3 mutations associated with Cobblestone lissencephaly found that three of the variants exhibit reduced stability and missence mutations were unable to complement TMTC3 rescue of gastrulation in Xenopus embryo development. Our study demonstrates that TMTC3 regulates O-linked glycosylation and cadherin-mediated adherence, providing insight into its effect on cellular adherence and migration, as well the basis of TMTC3-associated Cobblestone lissencephaly.

During vertebrate gastrulation, canonical Wnt signaling induces the formation of neural plate border (NPB). Wnt is also thought to be required for the subsequent specification of neural crest (NC) lineage at the NPB, but the direct evidence is lacking. We found previously that the disintegrin metalloproteinase ADAM13 is required for Wnt activation and NC induction in Xenopus Here, we report that knockdown of ADAM13 or its close paralog ADAM19 severely downregulates Wnt activity at the NPB, inhibiting NC specification without affecting earlier NPB formation. Surprisingly, ADAM19 functions nonproteolytically in NC specification by interacting with ADAM13 and inhibiting its proteasomal degradation. Ectopic expression of stabilized ADAM13 mutants that function independently of ADAM19 can induce the NC marker/specifier snail2 in the future epidermis via Wnt signaling. These results unveil the essential roles of a novel protease-protease interaction in regulating a distinct wave of Wnt signaling, which directly specifies the NC lineage.

During development, a multi-potent group of cells known as the cranial neural crest (CNC) migrate to form craniofacial structures. Proper migration of these cells requires proteolysis of cell adhesion molecules, such as cadherins. In Xenopus laevis, preventing extracellular cleavage of cadherin-11 impairs CNC migration. However, overexpression of the soluble cleavage product (EC1-3) is capable of rescuing this phenotype. The mechanism by which EC1-3 promotes CNC migration has not been investigated until now. Here we show that EC1-3 stimulates phosphorylation of Akt, a target of PI3K, in X.laevis CNC. Through immunoprecipitation experiments, we determined that EC1-3 interacts with all ErbB receptors, PDGFRα, and FGFR1. Of these receptors, only ErbB2 was able to produce an increase in Akt phosphorylation upon treatment with a recombinant EC1-3. This increase was abrogated by mubritinib, an inhibitor of ErbB2. We were able to recapitulate this decrease in Akt phosphorylation in vivo by knocking down ErbB2 in CNC cells. Knockdown of the receptor also significantly reduced CNC migration in vivo. We confirmed the importance of ErbB2 and ErbB receptor signaling in CNC migration using mubritinib and canertinib, respectively. Mubritinib and the PI3K inhibitor LY294002 significantly decreased cell migration while canertinib nearly prevented it altogether. These data show that ErbB2 and Akt are important for CNC migration and implicate other ErbB receptors and Akt-independent signaling pathways. Our findings provide the first example of a functional interaction between the extracellular domain of a type II classical cadherin and growth factor receptors.

Adam13/33 is a cell surface metalloprotease critical for cranial neural crest (CNC) cell migration. It can cleave multiple substrates including itself, fibronectin, ephrinB, cadherin-11, pcdh8 and pcdh8l (this work). Cleavage of cadherin-11 produces an extracellular fragment that promotes CNC migration. In addition, the adam13 cytoplasmic domain is cleaved by gamma secretase, translocates into the nucleus and regulates multiple genes. Here, we show that adam13 interacts with the arid3a/dril1/Bright transcription factor. This interaction promotes a proteolytic cleavage of arid3a and its translocation to the nucleus where it regulates another transcription factor: tfap2α. Tfap2α in turn activates multiple genes including the protocadherin pcdh8l (PCNS). The proteolytic activity of adam13 is critical for the release of arid3a from the plasma membrane while the cytoplasmic domain appears critical for the cleavage of arid3a. In addition to this transcriptional control of pcdh8l, adam13 cleaves pcdh8l generating an extracellular fragment that also regulates cell migration.

Objective/BackgroundADAMs are cell surface metalloproteases that shed a variety of substrate from the plasma membrane and contribute to multiple signaling cascades. Our objective was to determine the role of this protease during cranial neural crest cell migration.MethodsWe have used replacement of the endogenous ADAM proteins with proteins encoding truncated and mutated forms to test their ability to promote neural crest cell migration. Migration was assessed by following fluorescently labeled cells in vivo and in vitro.ResultsWe found that meltrins (ADAM9, 13 and 19) play a complex role to promote cranial neural crest cell migration. ADAM9 and 13 cleave Cadherin‐11 to release an extracellular fragment that promotes cell migration by signaling via receptor tyrosine kinases. In addition ADAM13 cleaves multiple protocadherins and extracellular matrix proteins that may contribute to its activity during CNC migration. Finally, the cytoplasmic domain of ADAM13 undergoes multiple phosphorylation and cleavage that result in its translocation into the nucleus where it regulates the expression of multiple genes including cytoplasmic (calpain8) and extracellular proteases (MMP13).ConclusionsWhile the proteolytic activity of ADAM is certainly critical as confirmed by our study, our result also uncovered an independent role for the cytoplasmic domains that has been conserved during evolution.Support or Funding InformationNIH RO1‐DE016289, NIH F31‐DE023275

RNA polymerases must couple the energetics of nucleotide addition to drive timed release of strong promoter contacts. RNA polymerases also undergo substantial structural changes in transitioning from sequence-specific initial transcription to stable elongation. Initially transcribing complexes are characteristically unstable, yielding short abortive products, but polymerase mutations have been isolated that dramatically reduce abortive instability. Understanding these mutations is essential to understanding the energetics of initial transcription and promoter clearance. using fluorescence probes of structural changes, we demonstrate that the low-abortive P266L mutant T7 RNA polymerase also transitions to elongation at longer lengths of RNA. We propose that both properties derive from a weakening of the initial barrier to hybrid-driven rotation of the promoter binding N-terminal platform, a motion necessary to drive promoter release. While the hybrid pushes on this protein element, the protein in turn pushes back on the hybrid, leading to the observed instability during initial transcription. Parallel biochemical experiments on bacterial RNA polymerase show that the sigma region 3.2 linker (analogous to the eukaryotic RNA polymerase "B-finger") functions in a very similar manner. Thus the mechanical "pushing" of the RNA-DNA hybrid against the protein is met by a reciprocal, and destabilizing, pushing of the protein against the hybrid.