SAN DIEGO – Fresh, never-frozen autologous CAR T cells targeting both CD19 and CD20 antigens on lymphomas demonstrated encouraging efficacy in an early readout from the DALY II USA clinical trial presented at the American Society of Hematology's annual meeting on Saturday.
Autologous CAR T-cell therapies involve harvesting patients' immune cells, transporting them to a centralized manufacturing location, modifying them to express chimeric antigen receptors targeting a specific tumor antigen (or several), expanding them, transporting them back to the patient, and reinfusing them as a one-time treatment. In this process, cryopreserving the product is typically a crucial step. All of the US Food and Drug Administration-approved CAR T-cell therapy products involve freezing and thawing cells.
But in a multicenter clinical trial sponsored by Miltenyi Biomedicine, based in Bergisch Gladbach, Germany, patients are receiving a product that's never been frozen. The Phase II trial is designed to evaluate this non-cryopreserved CAR T-cell product, dubbed zamtocabtagene autoleucel, or zamto-cel, in patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL) after two prior lines of treatment.
"The manufacturing protocol here is unique," said Nirav Shah, a hematologist-oncologist at the Medical College of Wisconsin, who presented the DALY II USA results. "This is a fresh-in, fresh-out product." According to Shah, zamto-cel is the first tandem CD19- and CD20-directed CAR T-cell product delivered without cryopreservation.
After the cell harvesting process, Shah explained, patients' cells are delivered to a central manufacturing site. There, using the CliniMACS Prodigy machine, an automated, closed device, the cells are modified so they express the dual-targeting CAR, then delivered back, still fresh, to the patient's treatment site and infused into the patient.
Patients in the DALY II USA trial do receive lymphodepleting chemotherapy so their bodies won't reject the product, but they receive it during the zamto-cel manufacturing process to expedite the total treatment time, Shah said. Zamto-cel's total vein-to-vein time, or the time from the moment the cells are harvested from the patient to when the patient receives the infusion of their CAR T-cell product, is currently 14 days. Vein-to-vein times vary among commercially available CAR T-cell therapies, but typically those take around three weeks to one month.
In the preplanned, interim analysis of 59 patients, the overall response rate with zamto-cel was 73 percent. This included a complete response rate of 51 percent and a partial response rate of 22 percent. The median progression-free survival was nine months, and among those patients who received a complete response, the median progression-free survival was not yet reached. After six months, the progression-free survival rate was 55 percent.
"This is still early data," Shah said. "[But] we look forward to letting this data mature to report what people want to know, which is one-year and two-year progression-free survival."
Patients' median duration of response was 11.4 months with zamto-cel, and this median response time was not reached in patients who had complete responses. The median overall survival was not reached in the study.
As for toxicities, Shah noted that there had been some concern going into the study that targeting two antigens would have a different side effect profile from what oncologists are accustomed to with CD19-targeting CAR T-cell therapies. But this was not the case. Zamto-cel had what Shah called an "incredible safety profile," with none of the patients experiencing grade 3 or higher cytokine-release syndrome and just three patients, or 4.3 percent, experiencing grade 3 or higher immune effector cell-associated neurotoxicity syndrome (iCANS). Grade 1 or 2 cytokine-release syndrome occurred in 46.4 percent of patients and lasted a median of four days.
So far, none of the patients developed secondary malignancies after zamto-cel, but Shah noted that, should there be any such cases, they would take more time to develop. "Further follow-up is indicated for this clinical trial," he said.
Benefits of dual targeting
One of the chief reasons that patients relapse following treatment with CD19-directed therapy is CD19 antigen loss, meaning that their B cells stop expressing the antigen that the cell therapy was designed to target. This has long been a limitation of CAR T-cell therapy, and one of the driving reasons for assessing dual-target approaches.
In the DALY II USA trial, Shah and colleagues wanted to interrogate this hypothesis.
To this end, they closely analyzed posttreatment biopsies from 27 patients who relapsed after zamto-cel. "In the great majority of them, there was no loss of CD19 or CD20," he said. "This is important when we think about sequential therapy and other treatment options that might be available for those patients who relapse post-CAR T."
Many other therapies available for lymphoma patients, both commercially and through clinical trials, are designed to target one or both of these antigens. This includes the growing class of bispecific therapies. Accordingly, patients whose cancers progress after zamto-cel, but who still express these targets, could, in theory, be eligible for a whole suite of other subsequent treatments that otherwise would be off the table if their cancers no longer expressed the antigens.
"That's a really important story [with this therapy]," Shah said. "We know that all of our agents that are active in diffuse large B-cell lymphoma rely on CD19 and CD20 targeting. The fact that patients aren't losing those antigens suggests that they can go on to receive subsequent therapies targeting that." Even though Shah didn't share data on which patients in the DALY II USA trial went on to receive which therapies, he noted that the fact that the median overall survival was not yet reached for the entire study population "suggests that patients are responding to subsequent therapies."
At the time of relapse to zamto-cel, only one of the 27 biopsied patients had lost expression of both the CD20 and CD19 antigens, and only four patients had lost expression of one of the two antigens.
In those patients who didn't experience any antigen loss, Shah said that it will take additional research to determine what it was that drove their relapse.
Toward automation, point-of-care
Miltenyi Biotech's closed system CliniMACS device is designed to manufacture CAR T-cell therapies at any center equipped with the device. The concept is a shift from the typical autologous CAR T-cell model, which involves shipping patients' frozen cells over long distances, then manufacturing them in a clean room at a designated facility with specialized personnel.
In the DALY II USA trial, Miltenyi did not manufacture the products for all patients at the point of care. But Shah said that is the goal going forward. Local manufacturing is currently available for patients treated at the Medical College of Wisconsin, which owns a CliniMACS system, but in this particular trial, the aim was to validate the process and dual-targeting therapy first, not to roll out the point-of-care option.
"The goal and intent [of DALY II USA] is to show we have efficacy of this product in a centralized manufacturing [setting]," Shah said. "But my goal, and the goal of Miltenyi, is to one day move toward a point-of-care model, and really allow distributed manufacturing, either regionally based or truly point of care."
According to Shah, any facility that currently does stem cell-like processing would be able to manufacture an autologous CAR T-cell therapy with a CliniMACS device.
This Phase II trial follows an earlier Phase I study of zamto-cel at the Medical College of Wisconsin, which treated patients with zamto-cel at the point of care. Miltenyi, of note, did not sponsor that initial study even though it involved their closed system manufacturing device. Instead, that Phase I study was sponsored by the Medical College of Wisconsin, but Miltenyi stepped in after seeing the promising early results and is now developing the dual-targeted therapy in its pipeline.
According to Miltenyi CEO Toon Overstijns, the reason for evaluating zamto-cel within a centralized manufacturing facility in the Phase II trial, instead of jumping straight into point-of-care trials, is due in part to regulations.
The firm is having discussions with regulatory authorities about the requirements for implementing point-of-care models into a trial. "There are ongoing evaluations related to quality control and good manufacturing practices requirements for point of care," Overstijns said.
Historically, regulatory challenges with potency assays, which measure individual products' ability to do what they're intended to do, have muddied efforts to automate autologous cell therapies. Regulators have pushed back on potency assay plans, and drugmakers and FDA reviewers alike have had to shift the way they think about these tests.
For zamto-cel, Shah said that the drugmakers are currently "reworking" the potency assay, but that one of the advantages of the Miltenyi device is the ability to test the product as it is being produced.
"The CliniMACS Prodigy allows you to pull out CAR T cells during the manufacturing process to initiate some of that release testing early," he said.