Seattle Children’s Researchers Share Progress at American Society of Gene and Cell Therapy Annual Meeting

May 16, 2023 - Pivotal research from Seattle Children’s Research Institute’s Center for Immunity and Immunotherapies (CIIT) will be showcased at the American Society of Gene and Cell Therapy’s (ASGCT) Annual Meeting, held May 16–20, 2023, in Los Angeles, California.

Last year, over 7,600 researchers from around the world attended the conference, with the work of only a small percentage selected for presentations each year. More than 20 CIIT scientists will attend this year’s event, and members of the labs of Drs. Richard James, Carol Miao and David Rawlings will present posters and abstracts highlighting advancements in novel cell therapies to treat cancer, Type 1 diabetes, hemophilia and more. CIIT’s Dr. Bruce Torbett is co-chairing a session on gene targeting and gene correction of the liver.

Additionally, biotechnology startups GentiBio and Be Biopharma — both spin-outs from the research institute — will present their latest findings, based on ongoing collaboration with James’ and Rawlings’ labs, in engineered regulatory T cells (Tregs) and B cells as they move closer to human clinical trials and large-scale manufacturing.

“We're the world leaders in both of these technologies,” said Rawlings, CIIT director and a professor of pediatrics and an adjunct professor of immunology at the University of Washington School of Medicine. “GentiBio and Be Biopharma are making great progress in parallel with the new data our labs are generating.”

Among the research institute findings being presented:

• Poster Abstract: Human Plasma Cells Engineered to Produce Bi-Specific T Cell Engagers Show In Vivo Anti-Tumor Efficacy
  
  Lead author Tyler Hill, James Lab. Seattle Children’s contributors include James and lab members Parnal Narvekar, Gregory Asher and Nathan Camp; Rawlings and former lab member Kerri Thomas.
  
  Engineered plasma cells (ePCs) were shown to kill leukemia in this collaborative study with Be Biopharma. “This is the first proof of concept that plasma cells producing an anti-cancer reagent can kill cancer cells in a humanized mouse model,” said James, an associate professor of pediatrics and pharmacology at the University of Washington School of Medicine. This effort broadens the application of engineered B cells from genetic diseases into cancer. The findings support further development of ePCs for use as a durable, local delivery system for the treatment of acute leukemias and potentially other cancers.
  
  
• Oral Abstract: SEC-seq: Association of Molecular Signatures with Antibody Secretion in Thousands of Single Human Plasma Cells
  
  Lead author Dr. Rene Cheng, James Lab. Seattle Children’s contributors include James and current and past lab members Cade Ito and Andee Ott, respectively; Rawlings.
  
  Protein secretion drives many functions in the body but methods to link how much protein an individual B cell is secreting with that cell’s specific genetic information were lacking. Using a technology called hydrogel nanovials, these proof-of-concept findings illuminated the factors that regulate secretion by plasma cells. “We can now study genetic factors in the cell and the amount of protein that gets secreted simultaneously,” James said. “No one had done that before. This links our gene editing to single-cell secretion, critical to optimize the engineering steps.” The team’s method lays the foundation for numerous discoveries in immunology and stem cell biology. “We envision applying this method to better engineer a cell therapy with high therapeutic protein secretion capacity,” said Cheng.
  
  These findings have been published by Nature Communications.
  
  
• Oral Abstract: Liver-Specific Targeting CRISPR/Cas9 mRNA LNPs Achieve Long-Term FVIII Expression in Hemophilia A Mice
  
  Lead author Dr. Chun-Yu Chen, Miao Lab. Seattle Children’s contributors include Miao and lab member Xiaohe Cai.
  
  The researchers demonstrated lipid nanoparticles (LNPs) carrying gene-editing tools can treat hemophilia A, an inherited bleeding disorder. “This is the first study to show gene correction of factor VIII [the protein needed to form blood clots] deficiency using LNPs in a hemophilia mouse model,” said Miao, professor of pediatrics at the University of Washington School of Medicine. The findings will foster future development of LNPs targeting liver sinusoidal endothelial cells, which line blood vessels’ interior, to treat genetic deficiency for hemophilia A as well as other diseases related to endothelial cells. Miao and her team plan to next improve the targeting efficiency, aiming to increase gene correction efficiency to treat hemophilia A and other related diseases. 
  
  
• Poster Abstract: Treatment of Canine Hemophilia A via Intraosseous Delivery of a Platelet-Specific Factor VIII-Lentiviral Vector
  
  Lead author Dr. Cameron Rementer, Miao Lab. Seattle Children’s contributors include Miao and lab members Dr. Chong Li, Xiaohe Cai, Julia Joo and Dr. Xuefeng Wang; Dr. Hans Ochs; Rawlings.
  
  This study showed that injecting a platelet-specific FVIII lentiviral vector into bone marrow can correct hemophilia A in a diseased large-animal model. These findings, in collaboration with researchers at the University of North Carolina at Chapel Hill, will facilitate future development of clinical trials to apply this novel technology in clinical application. This approach is expected to be especially beneficial for the very challenging patient population who have already developed anti-FVIII inhibitors. Miao and her team are currently working on treatments addressing pre-existing inhibitors and are seeking clinical trial partnerships.
  
  
• Oral Abstract: CISC: A Multi-Purpose Enrichment Tool for HDR-Edited Human T Cells Applicable for Treg and CAR-T Therapeutic Cell Products
  
  Lead author Annaiz Grimm, Rawlings Lab. Seattle Children’s contributors include Rawlings and lab members Drs. Peter Cook and Su Jung Yang, Samuel West, Li-Jie Wang, Chester Jacobs, Noelle Dahl and Dr. Karen Sommer; Dr. Andrew Scharenberg.
  
  A platform called a chemically inducible signaling complex (CISC) promotes the survival and expansion of Tregs and CAR-T cells. “T cells in general, and Tregs in particular, are dependent upon IL-2, a cytokine [a protein that functions as a chemical messenger] that keeps them alive,” said Rawlings. “A major challenge for Tregs is that they cannot make their own IL-2 so they rely on other cells making it. When you transfer a Treg into a patient, it must compete with other cells for IL-2. The CISC system gives an IL-2 signal specifically to the engineered Tregs (EngTregs) so those cells preferentially survive.” The researchers found the boost allowed the EngTregs to engraft and thrive and also perform better in treating disease in humanized mouse model. The CISC technology is being utilized in collaboration with GentiBio to manufacture disease-specific EngTregs designed to treat patients with Type 1 diabetes and other autoimmune disorders. The journal Molecular Therapy recently published online the Rawlings’ team and GentiBio’s CISC technology findings.
  
  
• Oral Abstract: Pancreatic Islet-Specific Engineered Treg Are Therapeutic in Mouse Models of Type 1 Diabetes
  
  Lead author Travis Drow, Rawlings Lab. Seattle Children’s contributors include Rawlings and lab members Noelle Dahl, Dr. Peter Cook and former lab member Dr. Akhilesh Singh.
  
  Immunosuppressive Tregs have tremendous promise as a cell-based therapy for tissue-specific autoimmune diseases. Importantly, antigen-specific Tregs work better than polyclonal Tregs in mouse models of Type 1 diabetes. However, expansion of naturally occurring antigen-specific Tregs is challenging. To address this, the researchers devised strategies to generate antigen-specific engineered regulatory T cells (EngTregs) at the scale needed for clinical use. “In the mouse model, we’ve shown that not only can we prevent diabetes, but we can go in at a later point and treat animals with severe islet inflammation [a symptom of diabetes] and block diabetes development,” said Rawlings of the research collaboration with GentiBio. Rawlings said this prevention and treatment data shows significant progress toward the creation of a therapeutic product and is being used to support the investigational new drug application ahead of a future Type 1 diabetes clinical trial.
  
  
• Poster Abstract: Generation of HLA-A2-Specific CAR Engineered CD8 Tregs with Robust In Vitro and In Vivo Suppressive Activity
  
  Lead author Dr. Subhash Tripathi, Rawlings Lab. Seattle Children’s contributors include Rawlings and lab members Noelle Dahl, Dr. Peter Cook, Martina Hunt and former lab member Dr. Yuchi Honaker.
  
  Within the immune system, CD4 T cells are helpers, assisting other blood cells to produce an immune response, while CD8 T cells are cytotoxic, inducing cell death. T cells play roles in immune tolerance and immunosuppression, impacting autoimmune disorders, solid organ transplantation and graft vs. host disease. The Rawlings team previously created engineered CD4 Tregs and have now expanded that work to make engineered CD8 Tregs. “That allows us to use some of the unique biology of CD8 T cells to do different things with regulatory cells,” said Rawlings, including testing the addition of chimeric antigen receptors (CARs) to these cells to help suppress immunity in transplantation and potentially in other diseases.

— Colleen Steelquist