NEW YORK – Researchers in Australia are hopeful that a new CRISPR-edited CAR T-cell therapy candidate for solid tumors, including breast and ovarian cancers, could better deliver immune-stimulating cytokines that kill tumor cells but avoid healthy cells.\n\nThe team, based at the Peter MacCallum Cancer Center in Melbourne, identified two endogenous gene promoters, NR4A2 and RGS16, that are active in CAR T cells and better at directing cytokines to the tumor. Over a decade of preclinical research and testing in mice and in cell lines demonstrated that these CAR T cells, which the researchers dubbed \"precision-guided munition\" cells, are particularly active against solid tumors, including breast, colon, and ovarian cancers. Based on preclinical research, they estimate that cure rates in some cancer settings could be close to 100 percent for this type of CAR T-cell therapy. \n\nThe next step, which they hope to reach within the next five years, is to bring the therapy to first-in-human clinical trials.\n\nWhen the first autologous CAR T-cell therapy, Novartis' Kymriah (tisagenlecleucel), was approved by the US Food and Drug Administration in 2017, it was seen as a promising advancement that, in some cases, could be curative. Since then, seven CAR T-cell therapies have been approved for treating blood cancers, including lymphomas, leukemias, and multiple myeloma. \n\nThe first two cell therapies for solid tumors finally came to market last year, with the approvals of Iovance's tumor infiltrating lymphocyte therapy Amtagvi (lifileucel) in melanoma and Adaptimmune's autologous T-cell receptor (TCR) therapy Tecelra (afamitresgene autoleucel) in synovial sarcoma — but these aren't CAR T-cell therapies. \n\nDeveloping a safe and effective CAR T-cell therapy for solid tumors, which account for 90 percent of cancer diagnoses, has been a challenge. \"We need to overcome the tumor microenvironment and its capacity to dampen or suppress CAR T-cell activity, and we need CAR T cells to be able to traffic and penetrate the tumor in high numbers to have an effect,\" said Phil Darcy, who co-heads the cancer immunology program at the Peter Mac and is leading the center's research on this CRISPR-edited CAR T-cell therapy.\n\nMyriad CAR T-cell therapies for solid tumors have entered clinical testing, but some of the most potent cytokines, like IL-12, which the Peter Mac team has been using, can cause unexpected toxicities bad enough to terminate a trial.\n\n\"Previous strategies have tried a range of different cytokines, such as IL-15, IL-18, and IL-12,\" said Paul Beavis, an associate professor at the Peter Mac who worked on the preclinical research. \"But the problem is that because these cytokines are naturally designed to activate an immune response, if they're not controlled sufficiently to the tumor site, it causes an inflammatory response all around the body and limits the ability to deliver this as a therapy.\" \n\nBeavis' solution is to use CRISPR to insert an armoring gene encoding \"a pro-inflammatory protein into the CAR T-cell genome in such a way that the CAR T cells only release this pro-inflammatory protein at the tumor site.\" The team's research found a bit of flexibility in choosing the knock-in design — while NR4A2 may be ideal for IL-12, which is highly effective but also highly toxic, RGS16 may be better suited for less-toxic cytokines like IL-2.\n\nCell therapy researchers have dabbled in using CRISPR to generate off-the-shelf CAR T-cell therapies or conduct knock-out gene experiments to try to find the genes that provide the greatest advantage. Beavis said his team's knock-in approach is novel and believes their armored \"precision-guided munition\" cells are the first to be able to deliver powerful cytokines through the highly-specific promoters NR4A2 and RGS16.\n\n\"The promoters that we found were much more tightly restricted than PD-1, so we think that clinically, they could be an advance,\" Beavis said.\n\nIt's a bit of a mystery why those genes are better at selectively releasing cytokines. \"I don't think we really fully know, and that's something we'll be looking to follow up on,\" Beavis said.\n\nThe team is in the early stages of securing funding and planning a clinical trial, for which they are exploring different proteins to target across various cancer indications. In solid tumors, GPC3 could be a candidate because of its safety profile in existing CAR T therapies. Beavis said multiple myeloma, a blood cancer that occurs in plasma cells in bone marrow, could be the first indication his team tests this treatment in within clinical trials to establish proof of concept, since CAR T-cell therapy has already shown to benefit those patients, though with decreasing efficacy over time. \n\n\"There's a window of opportunity there where we can provide a CAR T-cell therapy that we know will provide some level of benefit to patients, but there's still ample room for improvement so that we can test whether our approaches have increased the efficacy of therapy,\" Beavis said. Once efficacy is established in a known cancer setting, \"that would provide even greater initiative to go into the harder-to-treat solid tumors,\" which is \"ultimately where we would like to take this therapy,\" he said.\n\nA number of regulatory and logistical barriers make it especially difficult to get CAR T-cell therapies from the lab to patients, including the cost — which for a patient at the Peter Mac could amount to a steep half a million dollars, on par with other CAR T-cell therapies, Darcy said. Off-the-shelf allogeneic CAR T cells, developed with the help of CRISPR, could lower costs and ease distribution, but CRISPR-editing in cell therapies is newer and faces added scrutiny, Beavis said.\n\n\"There are some regulatory challenges around using CRISPR-edited products, because there's only been one FDA-approved CRISPR therapy, and it's still quite a new area,\" Beavis said, referring to the approval in 2023 of Vertex Pharmaceuticals' gene therapy Casgevy (exagamglogene autotemcel) for sickle cell disease and transfusion-dependent beta thalassemia. \"Exactly what's required in terms of showing that your CRISPR edits are safe is still a bit fluid.\" \n\nBeavis said patients would not notice a difference in the treatment process with CRISPR-edited CAR T cells, though, compared to existing CAR T-cell therapies. \n\nOnce proof of efficacy is established in humans, the Peter Mac researchers hope to apply the technology to a range of CAR T-cell therapies in development and improve their specificity and efficacy in solid tumors. The team was optimistic about its potential, even in hard-to-treat solid tumors like pancreatic cancer. In mice models, the therapy also avoided cytokine release syndrome, a severe adverse reaction associated with already-approved CAR T-cell therapies.\n\n\"Our technology is about improving existing CAR T-cell strategies,\" Beavis said. \"This work is all complimentary.\"

Researchers in Australia Explore Potential of New CRISPR-Edited CAR T-Cell Therapy in Solid Tumors

Australian researchers at the Peter MacCallum Cancer Center are developing a CRISPR-edited CAR T-cell therapy for solid tumors, using gene promoters NR4A2 and RGS16 to enhance cytokine delivery and target cancer cells more precisely. The therapy aims to improve efficacy against breast, ovarian, and other solid tumors, with preclinical trials suggesting near-100% cure rates. The team plans first-in-human trials within five years, addressing challenges like tumor microenvironment suppression and cytokine toxicity. Regulatory and cost hurdles, including CRISPR-editing scrutiny, remain critical barriers to clinical adoption.