An off-the-shelf, allogeneic CD30-CAR Epstein Barr virus–specific T-cell therapy has demonstrated favorable safety and encouraging clinical activity, even when given at lower dose levels, in patients with relapsed/refractory CD30-positive lymphoma.
An off-the-shelf, allogeneic CD30-CAR Epstein Barr virus–specific T-cell (EBVST) therapy (TT11X) has demonstrated favorable safety and encouraging clinical activity, even when given at lower dose levels, in patients with relapsed/refractory CD30-positive lymphoma, according to topline data from an ongoing phase 1 study (NCT04288726).1,2
Results from 6 patients who received the therapy were presented during the 2021 American Society of Gene and Cell Therapy Annual Meeting. Of 5 patients who were determined to be evaluable for efficacy, 3 patients achieved disease control with partial responses (PRs) to treatment, while 2 experienced disease progression.
“Off-the-shelf CD30-CAR EBVSTs have been shown to be safe and clinically active,” David Hon Quach, lead study author and postdoctoral associate in the Center for Gene Therapy at Baylor College of Medicine, said during a presentation on the data. “We want to monitor these patients to determine the durability of their clinical response, and we want to investigate the localization of our CD30-CAR EBVSTs because it is important to be able to determine whether they are present or not so we can evaluate whether our cells are protected from rejection.”
One of the challenges that come with off-the-shelf T cells derived from a donor is that when they are infused into a recipient, they can attack the recipient’s cells and cause graft-versus-host disease (GVHD). In contrast, off-the-shelf T cells, when infused into a recipient, can also be recognized by the recipient’s T cells and then be rejected.
Both reactions are mediated by alloreactive T cells; GVHD is caused by donor alloreactive T cells, while rejection is caused by recipient alloreactive T cells. For an off-the-shelf therapy to be successful, it must be able to overcome these issues. To this end, investigators set out to examine EBVSTs expressing CD30-CAR as a potential off-the-shelf option.
Several cell platforms have been investigated to address the issue of GVHD. Most autologous T-cell therapies have used αβ T cells that can knock out a T-cell receptor (TCR) to eliminate alloreactivity. Other T cells have restricted or invariant TCRs, like γδ T cells, virus-specific T cells (VSTs), or natural killer T cells. At Baylor College of Medicine, Quach and colleagues focused on using VSTs as a cell platform.
“There are so many benefits to VSTs in cell therapy. First, they are very safe in the allogeneic transplant setting. Hundreds of patients have been treated, with the cells derived from the donor or a third party, and in all of these trials, rarely any GVHD has been seen,” Quach explained. “Also, EVSTs have been shown to be proliferate in patients, and they possess memory and have the potential to persist long term. EVSTs can also expand in response to viral reactivation, and they can localize to lymphoid tissues and sites of inflammation.”
Due to this, EBVSTs were explored as an off-the-shelf therapy in patients with EBV-positive lymphoma. A total of 19 patients were treated with the cell therapy. Of these patients, 4 achieved complete responses, and 5 had stable disease. However, some of the participants experienced progression.
“We believe that might be due to a lack of persistence of our cells because these cells are allogeneic, and therefore, can potentially be rejected by the recipient’s alloreactive T cells,” Quach noted.
As such, Quach and colleagues have proposed a new strategy to prevent rejection. To do this, investigators set out to target recipient alloreactive T cells. They hypothesized that if there is a marker expressed on the alloreactive T cells, they could design a CAR to target that marker, which would allow for the CAR T cells to eliminate those alloreactive T cells, and thus, protect the CAR cells from rejection.
“CD30 is a molecule that is upregulated on alloreactive T cells when stimulated by allogeneic targets and so, luckily there has been a CAR that was designed against CD30,” Quach said. “The CD30-CAR has actually been tested clinically and shown to be both safe in patients, and effective against CD30-positive lymphomas. As such, we are developing a CD30-expressing EBVST as an off-the-shelf therapy.”
Because EBVSTs are not known to cause GVHD, the cells were hypothesized to be safe. Additionally, the cells possess the capability to eliminate alloreactive T cells, and therefore, should not be rejected. Moreover, as effectors, they should be able to eliminate CD30-positive tumors that are either EBV positive or negative; they should also be able to kill EBV-positive tumors that are either CD30 positive or negative, according to Quach.
Previously, Quach and colleagues evaluated these cells in an in vitro model to determine whether the cells could be protected from rejection. Investigators cultured EBVTs with allogeneic peripheral blood mononuclear cells (PBMCs) that contained alloreactive T cells. Within the culture, investigators anticipated that the alloreactive T cells would eliminate the EBVSTs and predominate in the culture, unless the EBVSTs expressed CD30-CAR.
In the CD30-CAR condition, they observed persistence of their EBVSTs and a limited expansion of the alloreactive T cells. Based on these data, they went on to evaluate whether this off-the-shelf treatment can be effective in patients. As such, they launched the phase 1 trial, where they evaluated the therapy in patients with relapsed/refractory, CD30-positive Hodgkin lymphoma or non-Hodgkin lymphoma.
The objectives of the research were to examine the safety of the approach, determine the persistence of the CD30-CAR EBVSTs, and evaluate the antitumor activity with the therapy.
Study participants previously received lymphodepletion chemotherapy comprised of cyclophosphamide at a daily dose of 500 mg/m2 plus fludarabine at a daily dose of 30 mg/m2. Three different dose levels will be evaluated. Patients start at dose level 1, which was 4 x 107 cells, and could be escalated to dose level 2 (1 x 108 cells) and dose level 3 (4 x 108 cells). After infusion, investigators draw blood on a weekly basis to measure the transgene and evaluate epitope spreading. In weeks 6 to 8, investigators perform diagnostic scans to examine the efficacy of the treatment.
The investigators generated a bank of 7 CD30-CAR EBVST lines that were derived from healthy donors, and characterized the lines to determine whether they were able to kill through the CAR and maintain EBV specificity.
“In determining the donor line to use to treat patients, we have actually decided to select the line that has the best human leukocyte antigen match between patient and donor because this will allow our EBVSTs to expand in response to EBV reactivation if present in patients,” Quach explained.
A total of 6 patients have been treated with the investigative off-the-shelf therapy; 3 of these patients received the treatment at dose level 1, while 3 received it at dose level 2.
One of the patients (patient #1), a 34-year-old female with relapsed Hodgkin lymphoma, received the therapy at dose level 1. On her pre-infusion scan, the patient had disease in the lymph nodes located in the abdomen and the pelvis; she had bone lesions, as well. By week 6 of treatment, most areas of her disease had resolved; however, 1 site had residual disease. As such, the patient was determined to have a PR to the therapy.
Another patient (patient #5), a 39-year-old female with relapsed Hodgkin lymphoma, received the therapy at dose level 2. At 6 weeks, most of the disease in her lymph nodes present in the chest and neck had been resolved with treatment. However, the patient had 1 solitary site of residual disease, so she was graded as having a PR.
Additionally, a 29-year-old male with relapsed Hodgkin lymphoma (patient #3) had a low tumor burden before cell therapy infusion. By week 6, the patient went on to develop a new lesion. The lesion was biopsied and determined to be CD30 positive, so the patient was graded to have disease progression.
All patients had weekly blood draws following infusion with the therapy, which allowed investigators to examine the presence of CD30-CAR EBVSTs in their blood by measuring the transgene with qPCR. In the 3 patients who received dose level 1, and 2 patients who received dose level 2, investigators detected cells present at the time of infusion, but rapid loss thereafter, except for patient #3 who had expansion following infusion.
“This result is quite puzzling to us, given the fact that even though there does not seem to be any cells present in the blood, there are many patients who did have a clinical response,” Quach explained. “The reason why we believe that is possible is that our CD30-CAR EBVSTs may be simply trafficking completely to the sites of disease, which, in our case, would be the lymph nodes or the bone marrow. Therefore, they would not present in the blood.”
When looking at the copy number analysis, investigators reported that most patients had peak transient expression at the time of infusion, whereas patient #3 had a peak at week 1. Moreover, 4 different donor lines were used to treat patients, and the first 3 patients were treated with the same line.
In the next steps for this research, Quach and colleagues want to infuse additional doses of the CD30-CAR EBVSTs to induce a greater response or achieve a more durable response. They would also like to treat patients with CD30-negative, EBV-positive lymphoma, Quach concluded.