Engineering Novel CAR T-Cells to Overcome CD58 Loss Alternative for Immunotherapy-Resistant Patients with Large B-Cell Lymphomas

For patients with large B-cell lymphomas who do not respond to treatment with immunotherapy, engineering chimeric antigen receptors (CAR) T-cells to overcome CD58 loss could provide an alternative route of treatment, according to data presented at the 2020 ASH Annual Meeting.^1,2

Early data in the mouse models suggest that the novel approach of providing CD2 costimulation to CAR T-cells in trans reestablishes the efficacy of the therapy in patients with CD58 mutations.

Anti-CD19 CAR T-cell therapy produces durable remission in approximately 40% of patients with B-cell lymphomas, however strategies to overcome mechanisms of resistance, including immune escape, are needed for patients.³ One such identified genetic event is CD58 inactivity. CD58 is the receptor of the CD2 molecule expressed by T cells and natural killer cells and its expression is necessary for T-cell– and natural killer cell-mediated cytotoxicity.⁴

CD58 mutations or loss are common and occur in 21% of patients with diffuse large B-cell lymphoma (DLBCL) and CD58 protein expression is deregulated in approximately 67% of all patients with DLBCL.⁴

In results of a study of 51 patients treated with axicabtagene-ciloleucel (axi-cel; Yescarta), 25% of patients did not have a fully functioning version of the CD58 protein and that these patients did not have a long-term response to axi-cel.^1,2 Patients with DLBCL who had a CD58 alteration—either a mutation or absence by next generation sequencing or immunohistochemistry—the median progression-free survival was 3.12 months for patients versus not reached for those with CD58 wild-type disease (P=.0043) at a median follow-up of 12.4 months.¹

“[The outcomes for] patients who don’t obtain durable, complete responses outcome is really, really poor, [with a median] overall survival of a less than 200 days,” said Robbie G. Majzner, MD, an assistant professor of pediatrics in the Division of Hematology and Oncology at Stanford University School of Medicine.

Further, he noted that when examining the data of the types of responses elicited in patients with DLBCL, less than 30% of those with CD58 alterations had complete responses to treatment with axi-cel compared with almost 80% of patients with CD58 wild-type disease. Partial responses were seen more in those with CD58-altered DLBCL (approximately 60%) compared with CD58 wild-type disease (approximately 15%).¹

“We wanted to understand the biology of what CD58 is providing for CAR T cells,” Majzner said. “We know that CAR T-cell [therapy] is able to induce long-term remission in patients, we feel that if we could just get this initial response rate up and find that find the mechanisms of resistance and engineer around them, we could cure more patients,” he said.

Pinpointing Immune Escape

To test this hypothesis, investigators took a B-cell leukemia line and used CRISPR technology to create a CB58 knockout version of the gene. Next, they exposed CAR T cells including a 1928 axi-cel–like CAR and a 19BBC tisagenlecleucel (Kymriah)-like CAR. “This is a killing assay and CAR T cells lose their ability to kill the tumor cell when CD58 is knocked out,” Majzner said.

In mice models, those that were inoculated with CD58 wild-type leukemia and treated with the axi-cel–like product had long-term disease control compared with those who were treated with CD58 knockout leukemia and experienced initial disease control and response, but ultimately relapsed and died from disease progression.¹ Similar data were observed in those treated with a tisagenlecleucel-like product.

To overcome CD58 loss, investigators set their focus on reengineering CARs to integrate CD2 signaling to reestablish efficacy of the T cells. Investigators determined that the cross-linking between CD2 and CD58 played a role in driving CAR signaling and cytoskeletal rearrangements that drive T-cell function needed to kill target tumor cells.

“This data was very surprising to us, to see how important CD2 costimulation turned out to be for CAR T cells,” Majzner said. “We always considered CAR T cells to be already endowed with costimulation and what this data tells us is that other costimulators on the surface of tumor cells really matter and can drive that T-cell function.”

Investigators engineered CARs to integrate CD2 signaling in trans. “Only when we adopted this trans set up, did we have a significant tumor control of the CD58 knockout tumor cells and a significant prolongation of survival,” Majzner said. At the time of presentation, investigators noted that clinical trials could be underway within in 1 to 2 years.²

Investigators believe that the modified treatment could significantly increase the number of patients who are likely to benefit from axi-cel therapy and could have an effect on immunotherapy research in other malignancies where CD58 mutations are common.

References:

1. Majzner RG, Frank MJ, Mount C, et al. CD58 aberrations limit durable responses to CD19 CAR in large B cell lymphoma patients treated with axicabtagene ciloleucel but can be overcome through novel CAR engineering. Presented at: 2020 American Society of Hematology Meeting and Exposition; December 4-8, 2020; virtual. Accessed December 5, 2020. https://ash.confex.com/ash/2020/webprogram/Paper139605.html

2. Genome editing and cellular therapies show promise for treating blood disorders, cancers. News release. American Society of Hematology. December 5, 2020. Accessed December 5, 2020. https://www.hematology.org/newsroom/press-releases/2020/genome-editing-and-cellular-therapies-show-promise-for-treating-blood-disorders-cancers

3. Abramson JS. Anti-CD19 CAR T-cell therapy for B-cell non-Hodgkin lymphoma. Transfus Med Rev. 2020;34(1):29-33. doi:10.1016/j.tmrv.2019.08.003

4. Testoni M, Zucca E, Young KH, Bertoni F. Genetic lesions in diffuse large B-cell lymphomas. Ann Oncol. 2015;26(6):1069-1080. doi:10.1093/annonc/mdv019.