This year has seen a flurry of good news about CRISPR gene editing clinical trials in human patients. CRISPR-Cas 9 is a gene editing tool capable of providing specific changes to genes in a wide range of animal models. In the last few years, this tool has moved out of the lab and into the clinic.
CRISPR Gene Editing Treats Cancer in the US
Just this week researchers announced preliminary results from the first US clinical trial using CRISPR gene editing to fight cancer in humans (1). The research team at the University of Pennsylvania’s Abramson Cancer Center was led by Professor Carl June, one of the scientists behind CAR T cells. Similar to CRISPR-edited cells, CAR T cells are modified to express synthetic receptors that help target cancer cells. Two CAR T cell therapies, Yescarta and Kymriah, are now on the market after regulatory approval in 2017.
So far, Penn researchers have used CRISPR-edited T cells to treat two patients with multiple myeloma and one with sarcoma. Scientists first drew blood from each patient, isolated T cells, then used CRISPR to edit four genes in those T cells (1). The gene edits helped the T cells to target a specific antigen on cancer cells.
Initial trial results show that the CRISPR-edited T cells can multiply inside the body and bind to target cancer cells. None of the patients showed serious side effects, indicating that this treatment may be safe. However, none of the patients has yet responded to the therapy. The researchers are now expanding this clinical trial to include more patients. They will continue to monitor patients for any response to treatment or adverse side effects.
Gene Editing Treats Cancer and HIV in China
Scientists and doctors in China, where regulatory rules are much less stringent, have used CRISPR gene editing in more than 300 cancer patients (2). The first CRISPR clinical trial in humans took place in China in 2015. Since then at least 11 trials have tested this therapeutic approach in patients with lymphoma and kidney, lung, head and neck, prostate and bladder cancer. According to the doctors involved in these trials, many of the patients have responded to treatment. However, tumor regression may only occur months after initial treatment with gene edited cells.
Gene editing is not only being used to target cancer. In a report recently published in the New England Journal of Medicine, Chinese researchers also used CRISPR gene editing to treat a patient suffering from both leukemia and HIV infection (3). This trial involved killing off the patient’s own bone marrow cells then transplanting bone marrow stem cells that had been edited to inactivate the CCR5 gene. Cells lacking a functional CCR5 gene are more resistant than normal cells to HIV infection. The patient’s leukemia went into remission after this treatment. However, it has not yet cured his HIV.
CRISPR Gene Editing Treats Beta Thalassemia in Europe
Earlier this year, Swiss company, CRISPR Therapeutics, and US company, Vertex Phamaceuticals, announced they have used CRISPR-editing of bone marrow stem cells to treat beta thalassemia in one human patient (4). Beta thalassemia is caused by mutations in the HBB gene, which is responsible for producing beta-hemoglobin, the protein that carries oxygen in red blood cells. In the trial, scientists collected bone marrow stem cells from the patient and used CRISPR to activate a fetal version of hemoglobin within these cells. The patient was then treated with a drug to destroy any unedited bone marrow cells. Finally, the edited stem cells were infused back into the patient. The companies aim to test the treatment in 45 patients by 2022 (5).
These initial clinical trials show that CRISPR-edited cells could be a powerful way to treat a range of human diseases. Compared to other therapies, CRISPR seems to have rocketed out of preclinical research into clinical trials. Chinese scientists have largely spearheaded this push thanks to fewer regulatory hurdles than in the US or Europe. This has led to researchers around the world to question whether all countries should be subject to similar regulatory rules. It will be very interesting to see how regulatory bodies deal with gene therapies in the future, and to follow the results of clinical trials currently underway in the US and Europe.
- First-In-US trial of CRISPR-edited immune cells for cancer appears safe. (Online) Accessed 7 November at https://eurekalert.org/pub_releases/2019-11/uops-fto110519.php
- China, Unhampered by Rules, Races Ahead in Gene-Editing Trials. Wall Street Journal (Online) Accessed 7 November, 2019 at https://www.wsj.com/articles/china-unhampered-by-rules-races-ahead-in-gene-editing-trials-1516562360
- Xu et al. CRISPR-Edited Stem Cells in a Patient with HIV and Acute Lymphocytic Leukemia. NEJM. 2019
- CRISPR Therapeutics and Vertex Announce Progress in Clinical Development Programs for the Investigational CRISPR/Cas9 Gene-Editing Therapy CTX001. (Online) Accessed 7 November, 2019 at https://www.globenewswire.com/news-release/2019/02/25/1741524/0/en/CRISPR-Therapeutics-and-Vertex-Announce-Progress-in-Clinical-Development-Programs-for-the-Investigational-CRISPR-Cas9-Gene-Editing-Therapy-CTX001.html
- A Safety and Efficacy Study Evaluating CTX001 in Subjects With Transfusion-Dependent B-Thalassemia. ClinicalTrials.gov (Online) Accessed 7 November, 2019 at https://clinicaltrials.gov/ct2/show/NCT03655678