Creation of CAR-Tregs that are resistant to the senescent environment

To date, there is no effective drug to treat the neurodegenerative disease amyotrophic lateral sclerosis (ALS). ALS is a fast-progressing and ultimately fatal condition which leads to selective motor neuron loss and death within two to five years after symptom onset. The current gold standard treatment for ALS is riluzole, a drug without a proven mechanism of action that was developed in the early 1990s. As an unmet need, ALS is a target for drug development.

ALS involves abnormalities of the immune system, most strikingly changes to T cells, a specific type of white blood cell. In particular ALS causes the loss of a specialised T cell called a T regulatory cell or Treg. These cells act to dampen down the immune response and maintain self-tolerance, the ability of the immune system to recognise the body as a non-threat and only mount a response to foreign substances. In ALS not only do the numbers of Tregs decline but so also do their potent suppressive ability.

Cell therapies are in clinical development and involve expanding patient-derived Tregs but the treatment requires large doses of Tregs and patients decline soon after stopping the infusion. We believe this to be due to the highly pro-inflammatory and pro-senescence (ageing) ALS environment. Reflection Therapeutics have developed a new targeted methodology called a CAR-Treg (CAR, Chimeric Antigen Receptor) that shows improved performance over conventional cell therapies, however, the hostile environment these engineered cells find themselves in needs addressing. Therefore the main aim of this grant is to create a CAR-Treg that specifically targets inflamed areas while also being resistant to the damaging environment. The creation of this next generation CAR-Treg therapy is of vital importance as there is no effective treatment for ALS.

The last decade has brought an effector T cell-based revolution. Cellular therapies based on chimeric antigen receptors have shown unprecedented efficacy against haematological malignancies. Initial evidence for CAR-Tregs in inflammatory disorders have provided the proof of concept for their anti-inflammatory function. Reflection Therapeutics have engineered a CAR-Treg that specifically targets neuroinflammation. These neuro-specific CAR-Tregs can be used to treat amyotrophic lateral sclerosis (ALS), the most prevalent motor neuron disease.

An older age is a risk factor for the development of ALS and along with immunosenescence and age-associated inflammation contributes to disease progression. We have evidence of elevated numbers of senescent T cells from patients with ALS together with the ALS environment accelerating immune senescence to all T cell subsets, including Tregs.

We propose a multi-disciplinary approach to investigate the impact of senescence to CAR-Treg function. We postulate that the pathological unifier between ALS, senescence and immune dysfunction is metabolic imbalance. The metabolic environment is altered in both ALS and senescence and we will investigate the impact an altered nutrient availability has on CAR-Treg function using radiolabeled metabolites. This is of crucial importance as recent therapeutic developments have been conceived around the concept of resetting T cells to recreate a favourable inflammatory environment.

Immunomodulatory therapies have not been successful in treating ALS as studies have failed to consider the impact of senescence. We wish to engineer a CAR-Treg with the ability to stabilise the Treg phenotype, and to counteract senescence-induced changes in Treg metabolism. We will include GATA3 in the CAR-Treg as it stabilises both Foxp3 expression and metabolism in response to DNA damage mitigating the effects of immune senescence. This study offers a novel approach for the treatment of ALS.