Quell Therapeutics paused its liver transplant trial despite showing patient benefit. The pivotal trial size for their successful 'low-dose immunosuppression' endpoint required over 200 patients, a commercially prohibitive number for a small biotech compared to the ~60 patients needed for a 'no immunosuppression' endpoint.
The paused liver transplant trial provided crucial learnings that informed Quell's pivot to autoimmune diseases. They discovered that high baseline inflammation improves cell engraftment and that durable targets lead to long-term cell activity. These insights gave them confidence to pursue autoimmune indications where these conditions are prevalent.
A core safety feature of Quell's platform is inserting an extra copy of the FOXP3 gene into its Treg cells. This 'phenotype locks' the cells, anchoring them in a suppressive state. This prevents them from flipping into pro-inflammatory 'attacking' cells, which is critical when they are engineered with a CAR to target specific tissues.
Quell's CEO suggests a competitor's transient target may limit long-term efficacy. He notes that for a CAR-Treg to persist, it needs a stable antigen for activation. By targeting CD19 on B-cells which are not depleted, Quell ensures its therapy has a durable target, aiming for sustained, long-term disease control.
Quell differentiates its CAR-Treg therapy by aiming to restore immune balance. Unlike B-cell depletion therapies (CAR-T), their approach uses CD19 on B-cells as an activation signal. This creates a local suppressive environment that 'chills' multiple pathogenic cell types (T-cells, B-cells, macrophages) instead of killing just one.