Tunable ECMs for more effective T cell therapies

The Problem

Adoptive immune cell therapies (ICTs) are taking their place in the pantheon of modern medicines alongside drugs and gene therapies. In ICTs, immune cells are taken out of patients and engineered and amplified in vitro act as “living drugs” that recognize and respond to disease states when infused back into patients. Multiple engineered T cell therapies, with so-called CAR-T cell therapies at the forefront, have been approved for the treatment of blood-based (hematological) cancers. Two of the main objectives of ICT developers, target cell specificity and safely, are being increasingly better addressed by advances in immune cell and genome engineering. However, a third objective, maintaining immune cells’ therapeutic efficacy first during their in vitro amplification (manufacturing) and after their transfer into patients, remains a formidable challenge.

This problem is potentiated in efforts to fight tumors or other diseases in solid tissues. Following their infusion back into the body, the efficacy of engineered immune cells to kill unwanted target cells, and recall them in later encounters, is thought to be impacted by the mechanical features of the tissue environments they are experiencing. These fundamentally vary, for example, between bone, muscle, brain, and different organs, and pathological tissues such as tumor masses or fibrotic tissues are very different from healthy tissues. Being able to mimic this biomechanical impact already during the manufacturing of ICTs in vitro could thus allow to better match ICTs to target tissue biology, and thereby significantly boost therapeutic efficacies, and create opportunities to develop ICTs for a much broader scope of diseases.

Our Solution

A team led by David Mooney at the Wyss Institute developed a novel tunable biomaterial system that allows researchers to investigate and leverage the effects of tissue mechanics on the state of therapeutic T cells in vitro. The system is an engineered 3D model of the gel-like extracellular matrix (ECM) produced by cells, which is responsible for tissues’ different “stiffnesses” (how much a tissue “gives” under pressure) and “viscoelasticities” (the typical ways different tissues relax over time once pressure is removed) and allows both parameters to be independently tuned.

Tunable ECMs are centered around a type of collagen, an ECM protein produced by almost all cells in the body. In tissues, collagen is naturally organized into crimped fibrils that aggregate further into fibers by chemically cross-linking themselves. Each fibril functions as a mechanical spring, and each fiber as an assembly of springs. An ECM’s stiffness depends on how densely collagen proteins are packed together, whereas its distinct viscoelasticity depends on how densely they are cross-linked to each other.

The Wyss’ proprietary tunable ECM system essentially consists of a simple-to-fabricate biocompatible hydrogel whose stiffness can be modulated by varying the concentration of a synthetic collagen protein, and whose viscoelasticity can be modulated by varying the amount of a synthetic cross-linker molecule. In addition, tunable ECMs allow the incorporation of other activation agents that can synergize with mechanical activation. The utility of tunable ECMs for cell manufacturing processes benefits from their stability and longer-term storability at 4°C before use. Added to the surface of cell culture dishes, tunable ECMs allow immune cells, to either embed themselves within the hydrogel matrices, or attach to their surfaces to be mechanically stimulated. This exposure to mechanical cues induces T cells to express certain immune cell features related to their cytotoxic or memory functions that remain throughout the harvesting of cells from the cultures prior to their transfer into recipients of adoptive cell therapies, as well as within recipients’ tissues.

Product Journey

The team that developed tunable ECMs, led by Kwasi Adu-Berchie and Yutong Liu in Mooney’s group, using tunable ECMS, demonstrated in a proof-of-concept study that specifically viscoelasticity has a distinct impact on T cell development and function. When added to cultures of T cells during ICT manufacturing, more elastic tunable ECMs facilitated the development of cytotoxic “effector-like T cells” with tumor cell-killing potential, while more viscous tunable ECMs facilitated the development of “memory-like T cells.” Applied to the manufacturing of human lymphoma-specific CAR-T cells, more elastic tunable ECMs provided them with greater fast-acting tumor-eradicating potential following their transfer into mice with lymphomas than more viscous tunable ECMs.

This research, for the first time, has revealed the state and function of therapeutic T cells is controlled by tissue-specific viscoelasticities, and allowed the team to identify molecular pathways driving these effects. Tunable ECMs thus have potential to enhance the efficacy and precision of T cell therapies, with potential also for ICTs harnessing other immune cell types. They also can be used as a research tool to pinpoint signaling pathways controlling T cell responses to the natural mechanical stimulation provided by different tissues of interest that could be targeted with drugs directly to improve therapeutic outcomes of ICTs.