Casgevy was the first CRISPR therapeutic worldwide to receive FDA approval in December 2023. Since then, the number of clinical trials has grown: WU-CART-007, another CRISPR-modified treatment, achieves a 91 percent response rate in aggressive T-cell leukemias. How far CRISPR has actually penetrated cancer therapy overall is systematically examined in a meta-analysis of 89 studies published in the journal Medicine by a research team: the numbers are encouraging, but two fundamental obstacles still block broad application in solid tumors for years.
From sickle cell to tumor: CRISPR expands into oncology
CRISPR/Cas9 is a molecular tool that cuts and modifies DNA sequences in a targeted manner. In cancer medicine, two strategies are pursued: inactivation of oncogenes—genes that drive cancer growth—and restoration of tumor suppressor genes that normally protect cells from uncontrolled growth.
The analysis by Shafee Ur Rehman and Ghulam Husain Abbas, working at Ala-Too International University in Bishkek and at Mass General Brigham in Boston, evaluated 89 studies from 2015 to 2025. It distinguishes between two approaches: In the ex vivo procedure, cells are edited with CRISPR outside the body and then returned to the patient. This principle already underlies clinically tested CAR-T cell therapies. In the in vivo approach, CRISPR is introduced directly into the body and should modify cancer cells in the tumor at the site.
What the numbers show: effect size 0.82 in 30 quantitative studies
Of the 89 studies, 30 provided evaluable quantitative effect data. The pooled effect size according to Hedges g is 0.82 (95% confidence interval 0.75 to 0.88, p below 0.001). In statistical interpretation, a g-value above 0.8 is considered a large effect. For hematologic cancers such as leukemias and lymphomas, it is slightly higher at 0.85 than for solid tumors at 0.78.
In delivery—the introduction of CRISPR into target cells—a clear difference emerges: viral vectors like lentiviruses or adeno-associated viruses achieve gene knockout rates of 85 to 90 percent in laboratory studies. Non-viral methods such as lipid nanoparticles reach 60 to 80 percent. In the ex vivo domain, WU-CART-007, a CRISPR-modified CAR-T agent against T-cell leukemia, demonstrates this potential concretely: according to 2026 clinical trials, it achieved an overall response rate of 91 percent in early tests and received FDA Breakthrough Therapy Designation.
Where CRISPR still fails: off-target and the delivery problem
The large effect sizes hide two fundamental limitations. The first problem is off-target activity: CRISPR cuts not exclusively at the desired DNA site but can also attack similar locations in the genome. In cancer cells, which are already genetically unstable, such unintended interventions can trigger new mutations. The authors of the review cite this as the most critical safety concern of the technology. Jennifer Doudna, 2020 Nobel Prize laureate in Chemistry and co-developer of CRISPR/Cas9, has stated in multiple published opinions that improved Cas proteins and more precise screening methods must be developed before broad clinical approvals can be granted.
The second problem is delivery in solid tumors. Viral vectors occasionally trigger immune reactions. Lipid nanoparticles, which have proven effective for liver and lung, reach other solid tumors in insufficient concentration. Tumor heterogeneity aggravates the problem: a single tumor often contains genetically distinct subpopulations, only some of which may respond to CRISPR intervention. Glioblastoma, a common and aggressive brain tumor, is known for this heterogeneity; multiple ongoing CRISPR studies face exactly this challenge.
2026 and 2027: ongoing phase I/II trials deliver first answers
Clinical phase I and II trials with CRISPR-based cancer therapies are currently underway, mostly addressing hematologic malignancies such as leukemias and lymphomas. For solid tumors, including breast, lung, colon, and pancreatic cancers, preclinical results still dominate. The authors estimate that broader clinical utility in solid tumors is not realistic before 2028 to 2030, depending on how quickly delivery systems improve.
Another factor is cost. The first approved CRISPR therapeutic, Casgevy, for sickle cell disease costs roughly 2.2 million dollars per patient in the US. Personalized CRISPR approaches for cancer, where the tool is tailored to the patient's individual tumor mutation, would be even more expensive. Whether and how quickly statutory health insurance companies can reimburse these costs remains unclear and is critical for actual healthcare delivery.