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Clinical Trial Underway for One-Time Crispr HIV Treatment

Crispr-Cas9

Crispr editing with Cas9 enzyme (Broad Institute, NIH)

27 Jan. 2022. A clinical trial is underway assessing a therapy for HIV infections that aims to eradicate the virus with one dose of the gene-editing technique Crispr. The early- and mid-stage study is testing the treatment code-named EBT-101 developed by the biotechnology company Excision BioTherapeutics Inc. in San Francisco.

Today’s standard of care for HIV infections is antiretorviral therapy, which suppresses and controls, but does not eliminate the virus. Antiretorviral medications must be taken periodically, usually each day, to prevent viral loads from rebounding, since residual levels of HIV remain in infected individuals. Excision Bio says EBT-101, its one-time treatment candidate, is a functional cure for HIV.

According to Centers for Disease Control and Prevention, 36,801 Americans were diagnosed with HIV infections in 2019, a decrease of nine percent from 2015. About seven in 10 (69%) of those new cases were gay or bisexual men, with nearly a quarter (23%) heterosexual, and seven percent people who inject drugs. Worldwide, according to World Health Organization, nearly 38 million people were living with HIV in 2020, with 1.5 million new cases reported that year.

Excision Bio uses gene editing to remove large sections of DNA from HIV viruses, taking out the viruses’ ability to replicate and escape. For these edits, the company adapts Crispr, short for clustered regularly interspaced short palindromic repeats, a process based on bacterial defense mechanisms that use RNA to identify, monitor, and edit targeted locations in DNA. Excision says its Crispr process employs dual guided RNA probes with Cas 9 enzymes to eradicate parts of the viral DNA responsible for reproduction and viral escape. The result, says the company, is one EBT-101 treatment can disable HIV-1 viruses, the more common and infectious strain, preventing their replication and thus stopping further infection.

Safety and tolerability of Crispr

The clinical trial is enrolling nine male adults with HIV-1 infections and on an antiretroviral regimen, but with viral quantities below quantifiable levels. Participants at the four sites in the U.S. are randomly assigned to receive one of three dose levels of EBT-101, delivered with benign adeno-associated viruses often used in gene therapies. The study team is looking primarily for signs of adverse events in recipients in the next 48 weeks, using a standard grading guide for clinical trials of this kind.

Rachel Presti, lead investigator of the trial and professor of infectious diseases at Washington University in St. Louis, says in a company statement released through Globe Newswire, “We’ll be looking at the safety and tolerability of Crispr in removing fragments of viral DNA from the genome of infected cells and tissues that are known to be reservoirs of HIV. The existence of such reservoirs has been a major hurdle in our efforts to cure HIV.”

The team is also tracking efficacy indicators, including activity of the treatments in patients. Science & Enterprise reported in Sept. 2021 on the Food and Drug Administration accepting Excision Bio’s investigational new drug application for EBT-101, clearing the way for the trial.

Lisa Danzig, Excision Bio’s chief medical officer notes, “Forty years into this pandemic there is still no curative regimen,” adding “we are now working to validate our preclinical findings in the clinic by generating safety, pharmacodynamic, and preliminary efficacy data. We believe these data will inform the design of future studies and demonstrate EBT-101’s potential to address the unmet needs of patients with HIV.”

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