High-Specificity CRISPR-Mediated Genome Engineering in Anti-BCMA Allogeneic CAR T Cells Suppresses Allograft Rejection in Preclinical Models

Allogeneic chimeric antigen receptor (CAR) T cell therapies hold the potential to overcome many of the challenges associated with patient-derived (autologous) CAR T cells. Key considerations in the development of allogeneic CAR T cell therapies include prevention of graft-vs-host disease (GvHD) and suppression of allograft rejection. Here, we describe preclinical data supporting the ongoing first-in-human clinical study, the CaMMouflage trial (NCT05722418), evaluating CB-011 in patients with relapsed/refractory multiple myeloma. CB-011 is a hypoimmunogenic, allogeneic anti-B-cell maturation antigen (BCMA) CAR T cell therapy candidate. CB-011 cells feature 4 genomic alterations and were engineered from healthy donor-derived T cells using a Cas12a CRISPR hybrid RNA-DNA (chRDNA) genome-editing technology platform. To address allograft rejection, CAR T cells were engineered to prevent endogenous HLA class I complex expression and overexpress a single-chain polyprotein complex composed of beta-2 microglobulin (B2M) tethered to HLA-E. In addition, T-cell receptor (TCR) expression was disrupted at the TCR alpha constant locus in combination with the site-specific insertion of a humanized BCMA-specific CAR. CB-011 cells exhibited robust plasmablast cytotoxicity in vitro in a mixed lymphocyte reaction in cell cocultures derived from patients with multiple myeloma. In addition, CB-011 cells demonstrated suppressed recognition by and cytotoxicity from HLA-mismatched T cells. CB-011 cells were protected from natural killer cell-mediated cytotoxicity in vitro and in vivo due to endogenous promoter-driven expression of B2M-HLA-E. Potent antitumor efficacy, when combined with an immune-cloaking armoring strategy to dampen allograft rejection, offers optimized therapeutic potential in multiple myeloma. See related Spotlight by Caimi and Melenhorst, p. 385.

Directed differentiation of mouse pluripotent stem cells into functional lung-specific mesenchyme

While the generation of many lineages from pluripotent stem cells has resulted in basic discoveries and clinical trials, the derivation of tissue-specific mesenchyme via directed differentiation has markedly lagged. The derivation of lung-specific mesenchyme is particularly important since this tissue plays crucial roles in lung development and disease. Here we generate a mouse induced pluripotent stem cell (iPSC) line carrying a lung-specific mesenchymal reporter/lineage tracer. We identify the pathways (RA and Shh) necessary to specify lung mesenchyme and find that mouse iPSC-derived lung mesenchyme (iLM) expresses key molecular and functional features of primary developing lung mesenchyme. iLM recombined with engineered lung epithelial progenitors self-organizes into 3D organoids with juxtaposed layers of epithelium and mesenchyme. Co-culture increases yield of lung epithelial progenitors and impacts epithelial and mesenchymal differentiation programs, suggesting functional crosstalk. Our iPSC-derived population thus provides an inexhaustible source of cells for studying lung development, modeling diseases, and developing therapeutics.

Allogeneic chimeric antigen receptor-T cells with CRISPR-disrupted programmed death-1 checkpoint exhibit enhanced functional fitness

BACKGROUND AIMS

Therapeutic disruption of immune checkpoints has significantly advanced the armamentarium of approaches for treating cancer. The prominent role of the programmed death-1 (PD-1)/programmed death ligand-1 axis for downregulating T cell function offers a tractable strategy for enhancing the disease-modifying impact of CAR-T cell therapy.

METHODS

To address checkpoint interference, primary human T cells were genome edited with a next-generation CRISPR-based platform (Cas9 chRDNA) by knockout of the PDCD1 gene encoding the PD-1 receptor. Site-specific insertion of a chimeric antigen receptor specific for CD19 into the T cell receptor alpha constant locus was implemented to drive cytotoxic activity.

RESULTS

These allogeneic CAR-T cells (CB-010) promoted longer survival of mice in a well-established orthotopic tumor xenograft model of a B cell malignancy compared with identically engineered CAR-T cells without a PDCD1 knockout. The persistence kinetics of CB-010 cells in hematologic tissues versus CAR-T cells without PDCD1 disruption were similar, suggesting the robust initial debulking of established tumor xenografts was due to enhanced functional fitness. By single-cell RNA-Seq analyses, CB-010 cells, when compared with identically engineered CAR-T cells without a PDCD1 knockout, exhibited fewer T_reg cells, lower exhaustion phenotypes and reduced dysfunction signatures and had higher activation, glycolytic and oxidative phosphorylation signatures. Further, an enhancement of mitochondrial metabolic fitness was observed, including increased respiratory capacity, a hallmark of less differentiated T cells.

CONCLUSIONS

Genomic PD-1 checkpoint disruption in the context of allogeneic CAR-T cell therapy may provide a compelling option for treating B lymphoid malignancies.

Generation of a Purified iPSC-Derived Smooth Muscle-like Population for Cell Sheet Engineering

Induced pluripotent stem cells (iPSCs) provide a potential source for the derivation of smooth muscle cells (SMCs); however, current approaches are limited by the production of heterogeneous cell types and a paucity of tools or markers for tracking and purifying candidate SMCs. Here, we develop murine and human iPSC lines carrying fluorochrome reporters (Acta2hrGFP and ACTA2eGFP, respectively) that identify Acta2+/ACTA2+ cells as they emerge in vitro in real time during iPSC-directed differentiation. We find that Acta2hrGFP+ and ACTA2eGFP+ cells can be sorted to purity and are enriched in markers characteristic of an immature or synthetic SMC. We characterize the resulting GFP+ populations through global transcriptomic profiling and functional studies, including the capacity to form engineered cell sheets. We conclude that these reporter lines allow for generation of sortable, live iPSC-derived Acta2+/ACTA2+ cells highly enriched in smooth muscle lineages for basic developmental studies, tissue engineering, or future clinical regenerative applications.

Matrix stiffness modulates the differentiation of neural crest stem cells in vivo

Stem cells are often transplanted with scaffolds for tissue regeneration; however, how the mechanical property of a scaffold modulates stem cell fate in vivo is not well understood. Here we investigated how matrix stiffness modulates stem cell differentiation in a model of vascular graft transplantation. Multipotent neural crest stem cells (NCSCs) were differentiated from induced pluripotent stem cells, embedded in the hydrogel on the outer surface of nanofibrous polymer grafts, and implanted into rat carotid arteries by anastomosis. After 3 months, NCSCs differentiated into smooth muscle cells (SMCs) near the outer surface of the polymer grafts; in contrast, NCSCs differentiated into glial cells in the most part of the hydrogel. Atomic force microscopy demonstrated a stiffer matrix near the polymer surface but much lower stiffness away from the polymer graft. Consistently, in vitro studies confirmed that stiff surface induced SMC genes whereas soft surface induced glial genes. These results suggest that the scaffold's mechanical properties play an important role in directing stem cell differentiation in vivo, which has important implications in biomaterials design for stem cell delivery and tissue engineering.

Engineering bi-layer nanofibrous conduits for peripheral nerve regeneration

Trauma injuries often cause peripheral nerve damage and disability. A goal in neural tissue engineering is to develop synthetic nerve conduits for peripheral nerve regeneration having therapeutic efficacy comparable to that of autografts. Nanofibrous conduits with aligned nanofibers have been shown to promote nerve regeneration, but current fabrication methods rely on rolling a fibrous sheet into the shape of a conduit, which results in a graft with inconsistent size and a discontinuous joint or seam. In addition, the long-term effects of nanofibrous nerve conduits, in comparison with autografts, are still unknown. Here we developed a novel one-step electrospinning process and, for the first time, fabricated a seamless bi-layer nanofibrous nerve conduit: the luminal layer having longitudinally aligned nanofibers to promote nerve regeneration, and the outer layer having randomly organized nanofibers for mechanical support. Long-term in vivo studies demonstrated that bi-layer aligned nanofibrous nerve conduits were superior to random nanofibrous conduits and had comparable therapeutic effects to autografts for nerve regeneration. In summary, we showed that the engineered nanostructure had a significant impact on neural tissue regeneration in situ. The results from this study will also lead to the scalable fabrication of engineered nanofibrous nerve conduits with designed nanostructure. This technology platform can be combined with drug delivery and cell therapies for tissue engineering.

Response rates to combination therapy for chronic HCV infection in a clinical setting and derivation of probability tables for individual patient management

Evidence for efficacy of established treatment guidelines for chronic hepatitis C virus (HCV) disease is based on multinational randomized controlled trials (RCTs). Strategies for managing HCV, however, require an assessment of the effectiveness of intervention in routine clinical practice. We report the outcomes of combination therapy in a large cohort of HCV-infected individuals in the UK. A total of 347 (113 genotype 1, 234 genotype non-1) patients were treated with pegylated interferon and ribavirin according to current guidelines. Forty-two (37.2%) of those with genotype 1 infection and 164 (70.1%) with genotype non-1 infection achieved sustained viral response (SVR). Thirty-nine (11%) patients withdrew from treatment. In addition to viral genotype, factors predictive of a response to therapy were age at start of treatment and disease stage on pretreatment liver biopsy. Multivariate regression analysis demonstrated that the effects of age [odds ratio 0.5; 95% confidence interval (0.31-0.82) per 10-year increment (P = 0.006)] were confined to genotype 1 disease. In order to further inform the management of the individual patient, a multivariate logistic model was used to predict the probability of SVR for subgroups defined by disease stage, genotype and age at commencement of therapy. This model revealed striking differences in predicted response rates between subgroups and provided a strong rationale for early treatment, particularly for those with genotype 1 disease. Our study demonstrates that results comparable with those of RCTs can be achieved in clinical practice, and suggests that prediction of response rates based on probability modelling will provide a valuable adjunct to individual patient management.