Removing CD5 gene improves CAR-T expansion, antitumor capabilities
Click Here to Manage Email Alerts
Key takeaways:
- CD5 knockout CAR-T exhibited efficacy in several preclinical models.
- A phase 1 trial will evaluate the approach for patients with T-cell lymphoma.
Deleting the CD5 gene from chimeric antigen receptor T cells improved their expansion, durability and tumor-killing capabilities, according to study findings.
Researchers plan to evaluate this approach in a phase 1 trial of patients with CD5-bearing T-cell lymphomas.
If the trial replicates the findings observed in multiple preclinical models, investigators believe CD5 “knockout” eventually could be used to improve existing CAR-T products and guide development of others, including those that target solid tumors.
“I have six [or] seven models that show CD5 knockout improves CAR T-cell function,” Marco Ruella, MD, assistant professor of hematology-oncology at University of Pennsylvania’s Perelman School of Medicine and scientific director of Penn Medicine’s lymphoma program, told Healio. “I have no doubts about it.”
‘The story completely changed’
Ruella and colleagues did not start their research investigating CD5 knockout.
In fact, Ruella compared the discovery to his experience at Penn.
He grew up in Turin, Italy, and arrived at Penn for postdoctoral work. He planned to stay a couple years but after Carl H. June, MD — director of the Center for Cellular Immunotherapies at Perelman School of Medicine — helped pioneer tisagenlecleucel (Kymriah, Novartis), the first FDA-approved CAR-T product, Ruella could not bring himself to leave.
“The story completely changed,” Ruella said.
Ruella and colleagues initially investigated CD5 as a target to treat T-cell lymphoma.
CAR-Ts have produced significant results in non-Hodgkin’s lymphoma, multiple myeloma and other hematologic cancers; however, they have not been as effective in T-cell lymphoma, Ruella said.
“Less than 20% of patients with T-cell lymphoma survive at least 5 years,” Ruella said.
Researchers developed a CAR-T to target CD5 but, because normal T cells also express CD5, the cells began killing each other.
Ruella and colleagues decided to use CRISPR-Cas9 technology to knock out CD5.
Not only did the cells not kill each other, the CD5 knockout approach yielded “pretty striking” antitumor improvement over the original CAR T cells, Ruella said.
Researchers knocked out CD5 in multiple models — first with CD19 CAR, then to another blood cancer model using CD30. They observed improvement in both.
This approach also is relevant for solid tumors, Ruella said.
“We use a clinical-grade mesothelin CAR-T that was used in the clinic at Penn for pancreatic cancer. We developed the CAR-T, removed CD5 and, again, we had a several logs less disease in the mice that were treated with the CD5 knockout CAR-T.”
Researchers also have data with HER2 CAR and prostate cancer, as well as with T cell receptor-redirected T cells.
Researchers believe deleting CD5 removes multiple inhibitors.
“CD5 serves like an anchor, which a lot of factors bind to, and most of them are inhibitory factors,” said Ruella, citing CBL-B and SHP-1 proteins as examples. “If you remove CD5, those factors are not able to get to the immune synapse and are not able to inhibit CAR signaling, and, as a result, the CAR T cell without CD5 has a much stronger activation in all our models.”
Phase 1 trial
The phase 1 dose-escalation trial is open for individuals with relapsed or refractory CD5-positive T-cell lymphoma without peripheral blood disease.
Ruella expects the first patient to be treated in the next month.
Researchers will investigate safety and feasibility as primary endpoints. They also will evaluate response.
Approximately 10% to 15% of patients treated with FDA-approved CAR-T products achieve complete response, Ruella said.
“Anything that goes beyond that would be a huge success,” he added.
The study can accommodate up to 30 patients, but researchers expect to have a good idea of the safety and feasibility after 12 are treated.
Ruella and colleagues hope to enroll at least three patients by the end of the year, and they hope to have a sense of early results in the first quarter of 2025.
Ruella is particularly excited about the 5-day manufacturing period for the CAR product. Current FDA-approved products take between 7 to 10 days to make, he said.
“During this manufacturing, the T cells get sort of exhausted — they differentiate,” he said. “Every day in manufacturing, you get a lesser quality of the product. We decided to have 5-day manufacturing to get a much stronger product that is way more active.”
Safety profile
The CD5 knockout product may produce more cytokine release syndrome and neurotoxicity because of the proliferation and persistence of the CAR T cells, Ruella said.
It also is possible the CAR-T will attack healthy T cells that have a CD5 gene, which could lead to infections.
However, researchers believe that can be managed in one of three ways.
The CAR-T product has a “mirroring, binding domain,” Ruella said. “It binds to the antigen through an antibody called single chain variable fragment, which we think over time is going to be immunogenic.”
Each trial participant also will have a plan for stem cell transplantation, if necessary.
Lastly, the CAR-T product will be given with CD5-negative T cells.
“We show that they can recognize viruses like Epstein-Barr virus, cytomegalovirus and so on,” Ruella said. “While we are infusing a product that can be toxic to the T cells, we [also] are infusing T cells that don’t have CD5, so they’re not going to be killed but [they will] have the ability to protect the patient from infection.”
Future outlook
T-cell lymphoma is an orphan disease, so treatments can be fast-tracked if successful, Ruella said.
In 5 years, he hopes CD5 knockout can be a curative option for patients with T-cell lymphoma, and that the safety and efficacy support testing it for other types of hematologic and solid cancers.
“That would be the dream,” he said.
For more information:
Marco Ruella, MD, can be reached at mruella@upenn.edu.
Collapse
Click Here to Manage Email Alerts