Potential approach to improve solid tumor T cell therapy

Researchers at the Perelman School of Medicine at the University of Pennsylvania have been working on a preclinical study that focuses on a new strategy that uses a “one-two punch” to assist T cells in attacking solid tumors.

The results, which were reported in the Proceedings of the National Academy of Sciences (PNAS), demonstrated that focusing on two regulators that manage gene activities linked to inflammation caused T cell expansion in models to be at least ten times higher, increasing antitumor immune activity and durability.

Carl H. June, MD, the Richard W. Vague Professor in Immunotherapy at Penn and the director of the Center for Cellular Immunotherapies (CCI) at Abramson Cancer Center, pioneered CAR T cell therapy at Penn Medicine.

His work resulted in the first CAR T cell therapy approved for B-cell acute lymphoblastic leukemia in 2017. Since then, customized cellular treatments have transformed the treatment of blood cancers, but they have persistently failed to treat solid tumors, such as breast and lung cancer.

We want to unlock CAR T cell therapy for patients with solid tumors, which include the most commonly diagnosed cancer types. Our study shows that immune inflammatory regulator targeting is worth additional investigation to enhance T cell potency.”

Carl H. June, MD, Study Senior Author and Richard W. Vague Professor, Immunotherapy, University of Pennsylvania Health System

T cell fatigue, a condition where the T cells are continually exposed to antigens from the solid mass of tumor cells and become so exhausted that they are unable to generate an antitumor response, is one of the difficulties for CAR T cell treatment in solid tumors.

Since the T cells do not grow sufficiently or retain their role as effectively, engineering exhausted T cells from patients for CAR T cell treatment leads to a less effective finished product.

Regnase-1, an inflammatory regulator that can create hyperinflammation when disrupted in T cells, has previously been suggested as a possible target to indirectly counteract the effects of T cell exhaustion by revitalizing them to produce an antitumor response.

The research team, which included lead author David Mai, a graduate student in bioengineering at the School of Engineering and Applied Science, and co-corresponding author Neil Sheppard, DPhil, head of the CCI T Cell Engineering Lab, proposed that simultaneous targeting of the related-yet-independent Roquin-1 regulator could enhance responses even more.

Each of these two regulatory genes has been implicated in restricting T cell inflammatory responses, but we found that disrupting them together produced much greater anticancer effects than disrupting them individually. By building on previous research, we are starting to get closer to strategies that seem to be promising in the solid tumor context.”

David Mai, Study Lead Author and Graduate Student, School of Engineering and Applied Science, University of Pennsylvania Health System

In healthy donor T cells expressing two distinct immune receptors under investigation in Phase I clinical trials: the mesothelin-targeting M5 CAR (mesoCAR) and the NY-ESO-1-targeting 8F TCR (NYESO TCR), the researchers employed CRISPR-Cas9 gene editing to knock out Regnase-1 and Roquin-1 separately and together.

As CD19 is missing from solid tumors, neither modified T cell product targets this antigen, which is the one most commonly targeted by approved CAR T cell therapies.

After CRISPR editing, the T cells were expanded and infused into solid tumor mice models. Researchers found that the double knockout produced at least 10 times as many engineered T cells as removing Regnase-1 alone did, in addition to increasing antitumor immune activity and longevity of the engineered T cells. Moreover, it resulted in harmful lymphocyte overproduction in certain mice.

CRISPR is a useful tool for completely ablating the expression of target genes like Regnase and Roquin, resulting in a clear phenotype, however there are other strategies to consider for translating this work to the clinical setting, such as forms of conditional gene regulation.”

Neil Sheppard, DPhil, Study Co-Corresponding Author and Head, T Cell Engineering Lab, Center of Cellular Immunotherapies, University of Pennsylvania Health System

Sheppard added, “We are certainly impressed by the antitumor potency that was unleased by knocking out these two non-redundant proteins in combination. In solid tumor studies, we often see limited expansion of CAR T cells, but if we are able to make each T cell more potent, and replicate them to greater quantities, we expect T cell therapies to have a better shot at attacking solid tumors.”