On May 18, 2023 Poseida Therapeutics, Inc. (Nasdaq: PSTX), a clinical-stage cell and gene therapy company advancing a new class of treatments for patients with cancer and rare diseases, today highlights its two oral and four poster presentations on the Company’s preclinical gene therapy programs and platforms at the American Society of Gene and Cell Therapy (ASGCT) (Free ASGCT Whitepaper) 2023 Annual Meeting, being held at the Los Angeles Convention Center in Los Angeles and virtually May 16 – 20, 2023 (Press release, Poseida Therapeutics, May 18, 2023, View Source [SID1234631868]).
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"We are excited to highlight multiple advancements across our gene therapy programs and platform technologies at ASGCT (Free ASGCT Whitepaper), which underscore the significant progress our company has made in the past year," said Brent Warner, President, Gene Therapy at Poseida Therapeutics. "We are making encouraging progress with our P-OTC-101 program, where our hybrid LNP+AAV approach has shown its potential to deliver a functional cure for severe, pediatric-onset OTCD with a single dose. In addition, early preclinical data utilizing our Cas-CLOVER and non-viral piggyBac technologies continue to show great promise as we seek to unlock the potential of non-viral gene therapies for patients."
Oral Presentations
Title: Preclinical Proof-of-Concept: A Novel Hybrid Gene Therapy Approach to Treat Severe Early-Onset Ornithine Transcarbamylase Deficiency
Session Title: Metabolic, Storage, Endocrine, Liver and Gastrointestinal Diseases I
Presentation Time: Thursday, May 18, 2023, 2:30 – 2:45 PM PST
Location: Room 403 AB
Abstract Number: 127
Ornithine Transcarbamylase Deficiency (OTCD) is an X-linked urea cycle disorder that prevents the breakdown and excretion of ammonia, allowing it to rise to toxic levels and affect the central nervous system, leading to coma, seizures, brain damage, and death. Poseida has developed P-OTC-101, a liver directed gene therapy utilizing a hybrid lipid-nanoparticle (LNP) and adeno-associated virus (AAV) delivery system based on its piggyBac DNA insertion system to enable integration of the therapeutic human OTC gene into the genome. In this study, researchers demonstrated correction of severe OTCD following a single dose in a stringent mouse model of the disease. Researchers also reported preclinical pharmacology showing dose-response behavior as well as favorable translational safety and pharmacology in mice and non-human primates using this hybrid platform approach, which supports further development of P-OTC-101 towards evaluation in humans.
Title: Cas-CLOVER Technology Enables Precise Gene Editing and Site-Specific Transgene Insertion in Mouse Liver
Session Title: Gene Targeting and Gene Correction: Liver
Presentation Time: Thursday, May 18, 2023, 3:00 – 3:15 PM PST
Location: Room 515 AB
Abstract Number: 157
This presentation highlights the potential of Cas-CLOVER, Poseida’s high-fidelity, proprietary gene editing technology co-formulated with guide RNAs as a single LNP. Data demonstrated highly efficient editing and favorable tolerability in mice following a single dose of Cas-CLOVER with extremely low off-target editing in the liver. The study establishes proof-of-concept for knock-in of a transgene using Cas-CLOVER and a fully non-viral delivery system in mice and further supports the potential of this technology to develop effective therapies for rare diseases.
Poster Presentations
Title: Demonstration of Human Factor VIII Expression and Activity Following Single and Repeat Dosing of a Non-Viral Integrating Gene Therapy
Session Title: Wednesday Poster Session
Session Date/Time: Wednesday, May 17, 2023, 12:00 PM PST
Location: West Hall A
Abstract & Poster Board Number: 638
P-FVIII-101 is a fully non-viral liver-directed gene therapy combining Poseida’s proprietary piggyBac technology with nanoparticle delivery for the treatment of Hemophilia A. This study demonstrated the potential of P-FVIII-101 to produce durable human FVIII expression over six months in an adult mouse model of severe Hemophilia A following a single dose. The study also highlighted the potential of repeat dosing to achieve therapeutic levels of human FVIII activity. An integration site analysis revealed a favorable insertion profile and well-controlled integrated vector copy number. These data provide proof-of-principle evidence toward a potential functional cure for Hemophilia A.
Title: Development of a Novel Non-Viral Gene Therapy Platform
Session Title: Thursday Poster Session
Session Date/Time: Thursday, May 18, 2023, 12:00 PM PST
Location: West Hall A
Abstract & Poster Board Number: 945
The piggyBac DNA insertion system is a transposon-based gene therapy platform that enables stable integration of the therapeutic transgene into the genome, thereby offering the potential for durable and lifelong activity. This poster details formulation discovery work on an LNP comprising a novel degradable ionizable lipid with unique capabilities for efficient DNA delivery to the liver, as well as discovery and optimization of an LNP-based delivery system capable of co-encapsulating mRNA and DNA for delivery of piggyBac transposon system components.
Title: Editing of a γ-Globin (HBG1/HBG2) cis-Regulatory Element in Human Hematopoietic Stem and Progenitor Cells Using Cas-CLOVER Technology Reactivates Fetal Hemoglobin
Session Title: Thursday Poster Session
Session Date/Time: Thursday, May 18, 2023, 12:00 PM PST
Location: West Hall A
Abstract & Poster Board Number: 1212
This study demonstrates that high-fidelity Cas-CLOVER nuclease targeting of gamma globin genes provides efficient editing and reactivation of fetal hemoglobin expression. Cas-CLOVER-mediated gene editing of gamma globin genes was also shown to produce up to 70% positivity for fetal hemoglobin among differentiated red blood cells. Further, Cas-CLOVER-mediated gene editing did not adversely affect stem cell capabilities, including potential to produce the red blood cell lineage. These data support Cas-CLOVER editing of gamma globin genes as a potential therapeutic strategy for genetic diseases such as β-thalassemia and sickle cell disease.
Title: Development and Optimization of Novel Super piggyBac-Based Hybrid Gene Therapy Approach
Session Title: Friday Poster Session
Session Date/Time: Friday, May 19, 2023, 12:00 PM PST
Location: West Hall A
Abstract & Poster Board Number: 1318
This presentation describes the discovery and optimization of a novel LNP formulation suitable for delivery of Poseida’s super piggyBac transposase to the liver. In addition, these studies highlighted in vivo safety and pharmacology of Poseida’s lead LNP formulation in mice and non-human primates for use in liver-directed hybrid gene therapy applications. The presentation further characterizes the use of Poseida’s hybrid gene therapy platform in a mouse model of OTCD to achieve disease resolution at significantly lower doses of AAV. These data demonstrate the versatility of the piggyBac hybrid platform and its potential to achieve durable transgene expression when administered early in life.