In U.S. First, Scientists Safely Edit Cancer Patients’ Cells With CRISPR

The pioneering study is backed by tech billionaire Sean Parker

A microscope image of a T cell. Credit: National Institute of Allergy and Infectious Diseases

On Wednesday, U.S. scientists announced that they used the gene-editing tool CRISPR to modify the cells of cancer patients — a first in the United States — and that so far, the technique appears to be safe. It’s too early to tell whether the edited cells will help patients live longer, but researchers think the approach looks promising and is an important first step for using CRISPR against other diseases.

There’s an incredible amount of optimism around using CRISPR to treat or possibly cure a wide range of genetic disorders and cancers by snipping out detrimental strands of DNA from cells. The technology has drawn the attention of high-profile investors, including billionaire Sean Parker, co-founder of Napster and an early investor in Facebook, who helped fund the study. The idea is that CRISPR could eliminate disease at its source, rather than just alleviating symptoms, as the vast majority of pharmaceuticals on the market do. But CRISPR is a relatively new tool, and it is unclear how safe it is for human treatment. While experiments in animal subjects have looked promising, this new research gives scientists the first glimpse of how CRISPR will perform in people.

So far three cancer patients in the United States have received the experimental CRISPR treatment, which involved extracting certain immune cells — called T cells — from the blood, editing them in the lab, and infusing them back into the body. T cells are the body’s natural mechanism for fighting infections and other foreign invaders, including tumors. But the reason cancer can persist in the body is because it can hide from the immune system, going undetected by these T cells. In this trailblazing study, the first proposed use of CRISPR in humans, researchers used CRISPR to supercharge patients’ T cells by removing three genes that interfere with the immune cells' ability to bind to cancer cells and kill them.

A bag of modified T cells. Credit: Penn Medicine

Plans for this study were first reported in 2016 when an advisory group at the U.S. National Institutes of Health gave researchers at the University of Pennsylvania the green light. The first two patients were treated this April, and ultimately the study is slated to include 18 total patients with multiple myeloma, sarcoma, or melanoma whose cancers have relapsed or not responded to traditional cancer treatments, like chemotherapy or radiation.

The research, which is also funded by Philadelphia-based biotech startup Tmunity in addition to the Parker Institute for Cancer Immunotherapy, is still in its early stages, but so far it appears that the CRISPR-edited cells haven’t posed a risk to patients. The three patients who received the edited T cells, all in their 60s, have not responded to the treatment yet, but blood tests showed that the edited T cells survived in the body and migrated to cancer cells as intended. What those cells did once they reached the tumors is less clear: One patient’s cancer has worsened, another’s disease has remained stable three months after treatment, and the researchers say it’s too early to assess the third patient’s condition. None of the patients have had any major side effects from the therapy. The findings were released by the American Society of Hematology and will be presented at the group’s annual conference in December.

The results follow on the heels of another CRISPR study in which Chinese researchers found that editing the stem cells of an HIV patient was safe but didn’t reduce the amount of virus in his body. CRISPR has already been used in cancer patients in China, but researchers there have yet to publicly announce or publish any results.

It could still be months before we know whether CRISPR techniques being tried in current studies are effective in patients and years before a treatment becomes commercially available. For now, it’s encouraging that editing cells with CRISPR outside the body then putting them back in — known as an “ex vivo” treatment — looks safe. But the approach will only be useful for a handful of conditions, such as certain cancers and blood disorders. Other gene-editing treatments will require injecting CRISPR directly in the body, and just how safe that is in humans remains to be seen.