Strand Therapeutics Advances In Vivo CAR-T Therapy with Programmable circRNA Platform
Strand Therapeutics, a clinical-stage biotechnology company at the forefront of programmable RNA medicines, has announced the presentation of compelling preclinical data from its in vivo CAR-T program at the 2026 American Society of Gene & Cell Therapy (ASGCT) Annual Meeting. The data highlight a major technological breakthrough: the ability to generate functional CAR-T cells directly inside the body using a programmable circular RNA (circRNA) platform, eliminating the need for traditional ex vivo cell engineering.
This development represents a potentially transformative shift in the field of cell therapy, where scalability, accessibility, and safety have long been constrained by complex manufacturing processes. By combining advanced RNA engineering with targeted delivery technologies, Strand Therapeutics is positioning itself to redefine how CAR-T therapies are designed, produced, and administered.
Background: The Evolution of CAR-T Therapy
Chimeric Antigen Receptor T-cell (CAR-T) therapy has revolutionized cancer treatment, particularly for hematologic malignancies such as leukemia and lymphoma. Traditional CAR-T therapy involves extracting a patient’s T cells, genetically modifying them in a laboratory to express a tumor-targeting receptor, expanding them, and reinfusing them into the patient.
While highly effective in certain indications, this approach comes with significant challenges:
- Complex manufacturing processes requiring specialized facilities
- High costs, often exceeding hundreds of thousands of dollars per treatment
- Long production timelines, delaying treatment for critically ill patients
- Limited scalability, restricting global access
- Safety risks, including cytokine release syndrome and off-target effects
These limitations have driven the search for next-generation solutions—particularly in vivo CAR-T approaches, where the patient’s immune cells are engineered directly inside the body.
The Promise of In Vivo CAR-T Therapy
In vivo CAR-T therapy aims to bypass the need for external cell manipulation by delivering genetic instructions directly to T cells within the patient. If successful, this approach could:
- Dramatically reduce treatment costs
- Enable rapid administration
- Expand access to broader patient populations
- Simplify manufacturing and logistics
- Allow for repeat dosing and improved control
However, achieving this goal has proven challenging. Key hurdles include:
- Efficient and selective delivery to T cells
- Controlled expression of CAR proteins
- Avoidance of off-target effects
- Ensuring durability and safety of response
Strand Therapeutics’ latest data suggest that these challenges may be closer to resolution than previously thought.
Strand’s Programmable circRNA Platform
At the core of Strand’s innovation is its EverScript circular RNA (circRNA) technology. Unlike traditional linear mRNA, circRNA forms a closed-loop structure, which offers several advantages:
Stability and Durability
Circular RNA is inherently more stable than linear RNA because it lacks free ends that are susceptible to degradation. This results in prolonged protein expression within cells.
Enhanced Protein Production
The structure of circRNA enables efficient and sustained translation, allowing for robust generation of therapeutic proteins such as CAR constructs.
Reduced Immunogenicity
CircRNA can be engineered to minimize unwanted immune responses, improving safety profiles.
Targeted Lipid Nanoparticle (LNP) Delivery
To deliver its circRNA payload, Strand employs a targeted lipid nanoparticle (LNP) system. LNPs are already widely used in RNA therapeutics, including vaccines, but Strand has advanced this technology with cell-specific targeting capabilities.
Key Features of Strand’s LNP System
- Selective targeting of T cells in circulation
- Systemic delivery via intravenous administration
- Efficient cellular uptake and RNA expression
- Reduced off-target distribution
This targeted delivery is critical for ensuring that CAR expression occurs primarily in the desired immune cell population.
Strand Signal Stack: Integrated Platform Design
Strand’s broader platform, known as Signal Stack, integrates multiple layers of engineering to optimize performance, safety, and programmability.
Components of Signal Stack
- EverScript circRNA backbone
Provides stability and sustained expression - Enhanced CAR architecture
Optimized receptor design for improved targeting and activation - Targeted LNP delivery system
Enables precise delivery to T cells in vivo - SignalLock regulatory system
Incorporates microRNA (miRNA)-responsive elements for safety control
SignalLock: Built-In Safety Mechanism
One of the most innovative aspects of Strand’s platform is SignalLock, a proprietary system designed to regulate CAR expression using endogenous microRNA signals.
How SignalLock Works
- Specific miRNA sequences are embedded within the RNA construct
- These sequences respond to cellular environments
- In off-target cells, miRNA activity suppresses CAR expression
- In target T cells, CAR expression remains active
Benefits
- Reduces off-target toxicity
- Minimizes unintended immune activation
- Enhances safety profile
- Supports repeat dosing strategies
This approach introduces a level of biological precision that has been difficult to achieve with traditional gene therapy methods.
Preclinical Study Highlights
The data presented by Strand Therapeutics demonstrate the effectiveness of its platform across both humanized mouse models and non-human primates (NHPs).
Key Findings
1. Efficient In Vivo CAR-T Generation
Following intravenous administration, the platform successfully generated functional CAR-T cells directly within the body.
2. Robust Target Cell Elimination
The therapy achieved significant depletion of target cells, particularly B cells, which are commonly associated with certain cancers and autoimmune diseases.
3. Near-Complete B Cell Depletion in NHPs
In non-human primate models, the treatment resulted in near-complete B cell depletion—an important benchmark demonstrating translational potential.
4. Consistent Performance Across Models
Results were reproducible across different biological systems, reinforcing the robustness of the platform.
Implications for Oncology
Cancer remains one of the primary targets for CAR-T therapies. Strand’s in vivo approach could significantly expand the reach of these treatments.
Potential Advantages
- Faster treatment initiation
- Lower manufacturing costs
- Improved patient accessibility
- Ability to treat solid tumors (future potential)
Broader Oncology Applications
- Hematologic malignancies
- Solid tumors (with further optimization)
- Combination therapies with checkpoint inhibitors
Applications in Autoimmune Diseases
Beyond oncology, Strand’s platform has significant implications for autoimmune disorders.
Why CAR-T for Autoimmune Diseases?
Autoimmune diseases often involve dysfunctional immune cells attacking the body’s own tissues. Targeted depletion of these cells can restore immune balance.
Potential Indications
- Lupus
- Rheumatoid arthritis
- Multiple sclerosis
- Type 1 diabetes
The ability to safely and selectively eliminate specific immune cell populations opens new therapeutic possibilities.
Jake Becraft, PhD (CEO)
Strand’s CEO emphasized the significance of the findings, noting that generating CAR-T cells inside the body has long been a central goal in the field.
He highlighted that the platform achieves not only functional CAR-T generation but also the precision and safety required for real-world application.
Tasuku Kitada, PhD, MBA (President & Head of R&D)
Dr. Kitada underscored the years of optimization behind the platform, from RNA design to delivery systems and regulatory controls.
He also pointed to the broader potential of the technology, extending beyond oncology into multiple therapeutic areas.
Scientific and Industry Impact
The implications of Strand’s work extend beyond a single company or platform.
Industry-Level Impact
- Accelerates the shift toward in vivo cell therapies
- Reduces reliance on centralized manufacturing
- Encourages innovation in RNA-based therapeutics
Scientific Advancements
- Demonstrates feasibility of circRNA-based therapies
- Validates targeted LNP delivery for immune cells
- Introduces programmable safety mechanisms
Challenges and Future Directions
While the results are promising, several challenges remain:
Clinical Translation
Moving from preclinical models to human trials will require careful evaluation of safety and efficacy.
Regulatory Considerations
Novel platforms like circRNA and in vivo CAR-T will require new regulatory frameworks.
Long-Term Safety
Monitoring durability and potential long-term effects will be critical.
Scalability and Manufacturing
Although simplified compared to traditional CAR-T, large-scale production of RNA therapeutics still requires optimization.
Upcoming Presentation Details
Strand Therapeutics will present its findings at the ASGCT Annual Meeting with the following details:
- Abstract Title: Programmable circRNA-tLNP platform enables efficient in vivo CAR-T cell programming and robust activity in a NHP model
- Session Type: Oral Presentation
- Session Name: LNPs for in vivo CAR-T applications
- Date & Time: May 12, 2026, 9:00–9:15 AM ET
- Location: MCEC Room 210 ABC (Level 2)
Strand Therapeutics’ programmable circRNA platform represents a major step forward in the evolution of CAR-T therapy. By enabling the generation of functional CAR-T cells directly داخل the body, the company addresses some of the most significant limitations of current cell therapy approaches.
The combination of:
- Stable and efficient circRNA
- Targeted LNP delivery
- Built-in safety controls via SignalLock
- Demonstrated efficacy in non-human primates
positions Strand as a leader in next-generation RNA therapeutics.
If these findings translate successfully into clinical settings, in vivo CAR-T therapy could redefine the treatment landscape for cancer, autoimmune diseases, and beyond—bringing powerful, personalized therapies to a much broader patient population.
About Strand Therapeutics
Strand Therapeutics is a clinical-stage biotechnology company pioneering programmable mRNA therapeutics to unlock the full potential of genetic medicines. Strand is applying its proprietary Signal Stack platform, which integrates EverScript circular RNA, AmpliScript self-replicating RNA, SignalPath targeted delivery, and logic-driven SignalLock genetic circuits to enable precise control of therapeutic activity across tissues and cell types and overcome foundational limitations in targeting, durability, and safety.
Strand is advancing a pipeline with an initial focus on oncology and autoimmune disease. Its initial program, STX-001, an intratumorally delivered LNP-encapsulated self-replicating RNA expressing IL-12, has demonstrated preliminary evidence of systemic immune activation and anti-tumor activity in patients with advanced solid tumors who have progressed on prior therapies. Building on this early clinical validation, intravenously delivered STX-003 is designed for tumor-targeted expression and avoidance of off-target expression. STX-003, which is expected to enter the clinic in mid-2026, has the potential to be a major step forward for the fields of genetic medicine and oncology. Strand is also advancing STX-005, an in vivo CAR-T program designed to enable controlled, durable expression and repeat dosing. Founded by MIT synthetic biology pioneers, Strand has raised over $250 million and is headquartered in Boston
