Home / Health / In a CRISPR first, therapy aimed at curing the HIV patient seems safe

In a CRISPR first, therapy aimed at curing the HIV patient seems safe



An n HIV-positive man in China is doing well after receiving donor cell infusions whose genes were edited with CRISPR 19 months ago, researchers reported on Wednesday in the New England Journal of Medicine. That makes him the longest-followed individual ever treated with CRISPR, a gene technology that has inspired soaring hopes for disease cures and spawned a multibillion industry in just four years.

The patient's mere survival, apparently without side effects from a treatment that some studies suggested could trigger cancer or other catastrophic genetic damage, provides some assurance that CRISPR-based therapies can be safe ̵

1; and overshadows the fact that the intervention was well below target. : Eliminating HIV from Male Cells

"They tried a moon shot, and even though they didn't land on the moon, they came home safely," said Fyodor Urnov of the Innovative Genomics Institute at the University of California, Berkeley, who previously helped lead a study for Sangamo Therapeutics (SGMO) on whether an older gene technology, zinc fingers, could cure HIV / AIDS. Crucially, Urnov said of the Chinese study, "they emphasized how to get to the moon."

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It is rare but not uncommon for the New England Journal to publish articles describing a single patient. They do, said spokeswoman Julia Morin, "when the findings justify it."

The 27-year-old patient was diagnosed with HIV / AIDS in May 2016 and through further tests with acute lymphoblastic leukemia two weeks later, researchers led by Hongkui Deng of Beijing University reported. The man received standard AIDS treatment, antiretroviral therapy (ART), and chemotherapy for his form of leukemia, a cancer of the immune system's T cells.

But the researchers saw an opportunity for a moon shot: a one-and-done cure for AIDS. Although ART keeps the virus in check, it does not eradicate HIV-hiding in cells, so patients must take ART medications for the rest of their lives.

Serendipitously, however, researchers discovered a dozen years ago that transplants of cells that cause blood and immune cells, called hematopoietic stem and stem cells (HSPC), can cure AIDS if their genome contains a mutation in the CCR5 gene that blocks a common form of HIV from infecting cells.

"Serendipity" arose because the 2007 "Berlin patient", Timothy Ray Brown, who had both AIDS and leukemia, received a bone marrow transplant for the latter. It just so happened that the donor cells had the HIV-blocking CCR5 mutation. Brown, who was treated in Berlin, was thus cured of both his leukemia and AIDS and has not taken ART since his cell transplant.

Deng, who received his doctorate. at the University of California, Los Angeles, and one of China's most prominent biologists, reasoned that if hematopoietic stem cells that naturally had the CCR5 mutation can cure AIDS, perhaps those whose CCR5 gene is disrupted by CRISPR may do the same. [19659003] Because HSPC transplantation from a healthy donor is a standard treatment for acute lymphoblastic leukemia, the risk-benefit balance was much clearer than if the patient had AIDS alone: ​​He still received the cell transplant, so only the CCR5 status of the cells would be different.

Deng and his colleagues therefore edited hematopoietic stem cells from a healthy bone marrow donor. They delivered the CRISPR molecules – a targeting RNA and a DNA-cutting enzyme – not through a virus, as other experimental CRISPR therapies do, but through "electroporation", with current to lead to a minuscule opening in cells. The editing was designed to inactivate the CCR5 gene in a way that would keep HIV out of cells as a locked room keeps out visitors without a key.

As is typical of CRISPR, only a fraction of the cells were edited. When Deng and his colleagues tested the hematopoietic stem cells before infusing them into the patient, they found that 17.8% were without functional CCR5, as intended.

As the edited stem cells were infused into the patient and settled in his bone marrow, a series of measurements over time showed that only 5.2 to 8.28% of his bone marrow cells, progeny from the stem cells, had the intended CCR5 editing.

In an email interview, Deng acknowledged that it was a "low efficiency for gene editing in the patient." The likely explanation is that many of the edited, infused cells do not survive, and that they are extremely outnumbered by the unidentified donor cells or by and with the patient's own.

His leukemia went into remission after cell transplantation, but the low fraction of CCR5-edited cells was not sufficient to control his viral load. When the researchers took the patient of antiretroviral treatment seven months after the stem cell transplant, Consent, HIV rates and healthy T-cell counts fell, he went back to ART.

An encouraging discovery, however, was that the percentage of CCR5-edited cells increased during the drug weekend, and before that, the level of CCR5 disruption in T-cells was increasing. in the blood 2.96%, Deng told STAT, and it "reached a peak of 4.39% during the break." Unfortunately, he continued, "the pe the effective gene editing efficiency is 100%, suggested by the Berlin patient's case. "

Two scientists not involved in the study questioned the decision to transplant stem cells when so few had been successfully edited.

It has been known for several years "to more efficient CCR5 knockout tracks with answers," Berkeley's Urnov said. “They chose to treat a substance with cells that had less than 20% editing. This is not a decision I would have made. "That they did not achieve HIV control is not" surprising, "he said, but" does not reflect negatively on the approach. "

The fact is that low editing rates can be meaningful. In the Sangamo study with zinc fingers to edit CCR5, 12 HIV-positive patients received a single dose of 10 billion T cells. Between 11% and 28% of the cells were edited as intended, and no longer produced normal CCR5. Patients' levels of a type of T-cells that kill HIV, called CD4 T-cells, rose, indicating that the gene-edited T-cells not only had their own but actually spread, Sangamo reported in 2014. Although Sangamo concluded that the treatment was safe, and the company conducted a larger clinical trial, it no longer continues with that program and instead focused on through-editing for stem cell disease and other blood diseases.

Deng nevertheless called the levels of editing that he and his colleagues achieved "a promising gene therapy strategy" of HIV / AIDS. "The cells with the modified CCR5 gene lasted" for 19 months, counting, albeit at low levels, he said, and CRISPR met the intended target and no others, as far as researchers could determine through genome sequencing. This indicates, for example, that CRISPR did not become false and edited, for example, cancer suppressor genes.

So far, there is only one patient in the study, Deng said. But "we plan to improve the editing efficiency of hematopoietic stem cells and optimize the transplant protocol based on this patient," he said, guided by both his results and those from mouse studies he and his colleagues reported in 2017. That experiment they wrote, "Provides evidence to translate CCR5 -redited [hematopoietic] transplant for an HIV cure to the clinic. "

Deng was born in China and graduated from college there. After earning his doctorate at UCLA in 1995, he worked as a postdoctoral fellow at New York University, focusing on HIV, and in 1998 he became director of research for the Boston-based stem cell biotech ViaCell. He was attracted back to China in 2001 by a prestigious professorship at Peking University, where he originally worked on the use of human embryonic stem cells to cure diabetes. In 2006, he won $ 1.9 million from the Bill and Melinda Gates Foundation's Global Challenges for Global Health for Research on HIV and Hepatitis C. Vaccines

Not everyone agrees that CRISPR is ready to be used in HIV / AIDS patients. "I think it's too early to go to bed," said biologist Shuliang Chen of Ohio State University and Wuhan University, co-author of a new review of HIV / AIDS gene editing. First, inactivation of CCR5 holds only one HIV strain, not all. More generally, Chen said, "We need more evidence on CRISPR-related security, off-target effects and efficiency on target."

But there is a bigger question. "In most cases, HIV patients live well with antiviral drug therapy," Chen said; Deng's patient did just that. The only reason for "high-risk gene editing," he said, is if they also have leukemia, in which case "one can use gene-edited hematopoietic stem cells to kill two birds with one stone."

Nevertheless, there will be more experiments trying to cure HIV / AIDS with CRISPR. "This is not a complete success," said Urnov, "but what to do next and how to achieve that success is now even clearer."


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