A BAFF ligand-based CAR-T cell targeting three receptors and multiple B cell cancers

B cell-activating factor (BAFF) binds the three receptors BAFF-R, BCMA, and TACI, predominantly expressed on mature B cells. Almost all B cell cancers are reported to express at least one of these receptors. Here we develop a BAFF ligand-based chimeric antigen receptor (CAR) and generate BAFF CAR-T cells using a non-viral gene delivery method. We show that BAFF CAR-T cells bind specifically to each of the three BAFF receptors and are effective at killing multiple B cell cancers, including mantle cell lymphoma (MCL), multiple myeloma (MM), and acute lymphoblastic leukemia (ALL), in vitro and in vivo using different xenograft models. Co-culture of BAFF CAR-T cells with these tumor cells results in induction of activation marker CD69, degranulation marker CD107a, and multiple proinflammatory cytokines. In summary, we report a ligand-based BAFF CAR-T capable of binding three different receptors, minimizing the potential for antigen escape in the treatment of B cell cancers.

Aerosol-Mediated Non-Viral Lung Gene Therapy: The Potential of Aminoglycoside-Based Cationic Liposomes

Aerosol lung gene therapy using non-viral delivery systems represents a credible therapeutic strategy for chronic respiratory diseases, such as cystic fibrosis (CF). Progress in CF clinical setting using the lipidic formulation GL67A has demonstrated the relevance of such a strategy while emphasizing the need for more potent gene transfer agents. In recent years, many novel non-viral gene delivery vehicles were proposed as potential alternatives to GL67 cationic lipid. However, they were usually evaluated using procedures difficult or even impossible to implement in clinical practice. In this study, a clinically-relevant administration protocol via aerosol in murine lungs was used to conduct a comparative study with GL67A. Diverse lipidic compounds were used to prepare a series of formulations inspired by the composition of GL67A. While some of these formulations were ineffective at transfecting murine lungs, others demonstrated modest-to-very-efficient activities and a series of structure-activity relationships were unveiled. Lipidic aminoglycoside derivative-based formulations were found to be at least as efficient as GL67A following aerosol delivery of a luciferase-encoding plasmid DNA. A single aerosol treatment with one such formulation was found to mediate long-term lung transgene expression, exceeding half the animal’s lifetime. This study clearly supports the potential of aminoglycoside-based cationic lipids as potent GL67-alternative scaffolds for further enhanced aerosol non-viral lung gene therapy for diseases such as CF.

Viral Transduction of Human Rod Opsin or Channelrhodopsin Variants to Mouse ON Bipolar Cells Does Not Impact Retinal Anatomy or Cause Measurable Death in the Targeted Cells

The viral gene delivery of optogenetic actuators to the surviving inner retina has been proposed as a strategy for restoring vision in advanced retinal degeneration. We investigated the safety of ectopic expression of human rod opsin (hRHO), and two channelrhodopsins (enhanced sensitivity CoChR-3M and red-shifted ReaChR) by viral gene delivery in ON bipolar cells of the mouse retina. Adult Grm6Cre mice were bred to be retinally degenerate or non-retinally degenerate (homozygous and heterozygous for the rd1Pde6b mutation, respectively) and intravitreally injected with recombinant adeno-associated virus AAV2/2(quad Y-F) serotype containing a double-floxed inverted transgene comprising one of the opsins of interest under a CMV promoter. None of the opsins investigated caused changes in retinal thickness; induced apoptosis in the retina or in transgene expressing cells; or reduced expression of PKCα (a specific bipolar cell marker). No increase in retinal inflammation at the level of gene expression (IBA1/AIF1) was found within the treated mice compared to controls. The expression of hRHO, CoChR or ReaChR under a strong constitutive promoter in retinal ON bipolar cells following intravitreal delivery via AAV2 does not cause either gross changes in retinal health, or have a measurable impact on the survival of targeted cells.

Preclinical Evaluation of Prgn-3007, a Non-Viral, Multigenic, Autologous ROR1 Ultracar-T ® Therapy with Novel Mechanism of Intrinsic PD-1 Blockade for Treatment of Hematological and Solid Cancers

Traditional methods for chimeric antigen receptor (CAR) T manufacturing utilize viral vectors, ex vivo activation and expansion of T cells to achieve clinically relevant cell numbers, which leads to an exhausted T cell phenotype, high manufacturing costs, and treatment delays. The UltraCAR-T platform is designed to overcome these limitations using our advanced non-viral gene delivery system and a rapid, overnight manufacturing process (Blood 2019 134 (Supplement_1):2660; Blood 2020 136 (Supplement 1):17); Cancer Research 2020 80 (16Suppl):6593). UltraCAR-T cells, which express antigen specific CAR, membrane-bound IL-15 (mbIL15), and kill switch genes, are manufactured at the medical center's cGMP facility using autologous T cells and administered back to the patient only one day after gene transfer. UltraCAR-T cells are currently under clinical investigation for hematological (NCT03927261) and solid tumors (NCT03907527). Here we describe the advancement of the UltraCAR-T platform to address the inhibitory tumor microenvironment by incorporating intrinsic checkpoint blockade without the need for complex and expensive gene editing techniques. PRGN-3007, based on the next generation of the UltraCAR-T platform, is engineered to simultaneously express CAR for targeting receptor tyrosine kinase-like orphan receptor 1 (ROR1), which is overexpressed on many hematological and solid tumors; mbIL15 for enhanced in vivo expansion and persistence; kill switch for improved safety profile; and a novel mechanism for the intrinsic blockade of PD-1 gene expression. This approach of intrinsic blockade of PD-1 expression, only on UltraCAR-T cells, is aimed to avoid systemic toxicity and high cost of checkpoint inhibitors by eliminating the need for combination treatment. PRGN-3007 is manufactured using the already established rapid and streamlined UltraCAR-T manufacturing process. PRGN-3007 was generated using multiple healthy donor T cells using multi-cistronic non-viral vector and the overnight manufacturing process. The co-expression of CAR, mbIL15 and kill switch transgenes was confirmed by flow cytometry, western blotting, and qPCR. Furthermore, PRGN-3007 showed significant reduction in PD-1 expression on UltraCAR-T cells compared to ROR1 CAR-T cells lacking PD-1 blockade (Control ROR1 CAR-T). The downregulation of PD-1 expression on PRGN-3007 resulted in enhanced ROR1-specific cytotoxicity and release of inflammatory cytokines upon co-culture with various ROR1 + PD-L1 + hematological and solid tumor cells compared to Control ROR1 CAR-T, especially at low effector to target cell ratios. Single-cell cytokine proteomics showed that the downregulation of PD-1 expression on PRGN-3007 resulted in a significantly higher number of polyfunctional CAR-T cells compared to Control ROR1 CAR-T. Expression of mbIL15 on UltraCAR-T, with or without downregulation of PD-1 expression, resulted in robust expansion in presence of ROR1 antigen, lack of autonomous expansion in absence of ROR1, and durable persistence even in absence of exogenous cytokines in vitro. Furthermore, PRGN-3007 was selectively and effectively eliminated by the kill switch activator antibody treatment. A single administration of PRGN-3007, only one day after gene transfer, effectively reduced tumor burden and significantly improved overall survival (p<0.05) of tumor bearing mice compared to Control ROR1 CAR-T in an aggressive xenograft model of mantle cell lymphoma (Figure). Blood analyses demonstrated sustained downregulation of PD-1 expression, rapid expansion, long-term persistence, and a predominant central memory phenotype of PRGN-3007 in tumor bearing mice. In summary, these preclinical data highlight the overall safety and improved efficacy of incorporating intrinsic downregulation of PD-1 expression on UltraCAR-T cells using non-viral gene delivery and the established rapid, decentralized manufacturing process. These data provide a strong rationale for the evaluation of PRGN-3007 for the treatment of ROR1 + malignancies. Figure: Overall survival in in an established model of mantle cell lymphoma in NSG mice. Tumor cells were engrafted in mice on Day 0 and treatments were administered on Day 8. Data shown is from 8 mice/group at the start of the study. * p<0.05, ***p<0.001; log rank test. Figure 1 Figure 1. Disclosures Chan: Precigen, Inc: Current Employment, Current equity holder in publicly-traded company. Scott: Precigen, Inc: Current Employment. Du: Precigen, Inc: Current Employment. Bolinger: Precigen, Inc: Current Employment. Poortman: Precigen, Inc: Current Employment. Shepard: Precigen, Inc: Current Employment. Koenitzer: Precigen, Inc: Current Employment. Govekung: Precigen, Inc: Current Employment. Sailor: Precigen, Inc: Current Employment. Johnson: Precigen, Inc: Current Employment. Plummer: Precigen, Inc: Current Employment. Zilko: Precigen, Inc: Current Employment. Dutta: Precigen, Inc: Current Employment. Kunchithapautham: Precigen, Inc: Current Employment. Athwal: Precigen, Inc: Current Employment. Klocke: Precigen, Inc: Current Employment. Zinser: Precigen, Inc: Current Employment. Abdeladhim: Precigen, Inc: Current Employment. Ahmad: Precigen, Inc: Current Employment; Kite, A Gilead Company: Ended employment in the past 24 months. Metenou: Precigen, Inc: Current Employment. Semnani: Precigen, Inc: Current Employment. Brough: Precigen, Inc: Current Employment, Current equity holder in publicly-traded company. Shah: Precigen: Current Employment, Current equity holder in publicly-traded company. Sabzevari: Precigen: Current Employment, Current equity holder in publicly-traded company; Kinnate BioPharma: Membership on an entity's Board of Directors or advisory committees; Compass Therapeutics: Current equity holder in publicly-traded company.

Development and Characterization of High Efficacy Cell-Penetrating Peptide via Modulation of the Histidine and Arginine Ratio for Gene Therapy

Cell-penetrating peptides (CPPs), as non-viral gene delivery vectors, are considered with lower immunogenic response, and safer and higher gene capacity than viral systems. In our previous study, a CPP peptide called RALA (arginine rich) presented desirable transfection efficacy and owns a potential clinic use. It is believed that histidine could enhance the endosome escaping ability of CPPs, yet RALA peptide contains only one histidine in each chain. In order to develop novel superior CPPs, by using RALA as a model, we designed a series of peptides named HALA (increased histidine ratio). Both plasmid DNA (pDNA) and siRNA transfection results on three cell lines revealed that the transfection efficacy is better when histidine replacements were on the C-terminal instead of on the N-terminal, and two histidine replacements are superior to three. By investigating the mechanism of endocytosis of the pDNA nanocomplexes, we discovered that there were multiple pathways that led to the process and caveolae played the main role. During the screening, we discovered a novel peptide-HALA2 of high cellular transfection efficacy, which may act as an exciting gene delivery vector for gene therapy. Our findings also bring new insights on the development of novel robust CPPs.

Recent Advancement and Innovations in CRISPR/Cas and CRISPR Related Technologies: A review

CRISPR genome editing technologies have been improving by every passing day. The initial CRISPR/Cas9 technologies, though emerged an improved version of genome editing in competition with TALENS and ZFNs, was nevertheless not free from technical and off-target effects. Technological improvements overtime start addressing issues with original CRISPR/Cas9 technology. The major areas of improvement targeted nucleases and delivery methods. Overtime the nuclease like Cas9 had some modifications like FokI-dCas9, Truncated guide RNAs (tru-gRNAs), Paired Cas9 nickase, Cpf1, Cas6 with Csm/Csr complex and chemically treated Cas9. In terms of delivery methods the improvements came along after almost all methods including viral methods like Recombinant Adeno Associated Viruses (rAAV), Lentivirus (LV), and bacteriophages. The review summarizes various non-viral gene delivery modes including physical methods like electroporation and chemical methods like nano particles, cell-derived membrane vesicles (CMVs) with upgraded developments. The review also compares various modes of delivering CRISPR gene editing machinery.

Nonviral Vehicles for Gene Delivery

Nonviral gene delivery (NVGD) is an appealing alternative to viral gene delivery for clinical applications due to its lower cost and increased safety. A variety of promising nonviral vectors are under development, including cationic polymers, lipids, lipid-polymer hybrids (LPHs) and inorganic nanoparticles. However, some NVGD strategies have disadvantages that have limited their adoption, including high toxicity and low efficiency. This review focuses on the most common NVGD vehicles with an emphasis on recent developments in the field.

HGG-16. DISSECTING THE EFFECT OF ATM DELETION ON RADIOSENSITIVITY IN DIFFUSE MIDLINE GLIOMAS WITH H3K27M MUTATION

Diffuse midline gliomas (DMGs) are responsible for a large proportion of childhood brain tumor deaths. Currently, radiation therapy is thought to be one of the most effective treatment options, but more than 90% of children still die within 2 years of diagnosis. DMGs are defined by somatic histone 3 K27M (H3K27M) mutations that have been shown to promote the G0/G1 to S cell cycle transition. The majority of DMGs also contain loss-of-function mutations in TP53. Prior research demonstrated that orthotopic xenograft and primary mouse models of non-H3K27M-mutated gliomas with inactivation of p53 are preferentially radiosensitized by inactivation of Ataxia Telangiectasia Mutated (ATM), a kinase that mediates DNA repair in response to DNA damage caused by radiation. The high frequency of mutations that deregulate p53 in DMGs raises the possibility that H3K27M-mutant DMGs may also be radiosensitized by ATM inhibition, representing a unique therapeutic opportunity. Here, we hypothesize that H3K27M-mutant DMGs that have loss of function of p53 will be radiosensitized by loss of ATM. To test this hypothesis, we used the RCAS-TVA viral gene delivery system to generate genetically-faithful primary mouse models of H3K27M-mutant DMG with p53 deletion, and we used Cre recombinase to delete Atm in the tumor cells of these mice and generated littermate controls that retained Atm. Mice were imaged weekly via luciferase-based bioluminescence to track tumor development and irradiated with three daily fractions of 10 Gy after tumor detection. We subsequently quantified the survival of mice without neurological decline following irradiation. In separate cohorts, we collected primary tumors after irradiation to verify H3K27M expression and to assess cell cycle arrest and mechanisms of cell death. These studies will elucidate mechanisms by which ATM inactivation can radiosensitize H3K27M-mutant DMGs with nonfunctioning p53, which will guide the design of clinical trials testing ATM inhibitors in DMG patients.