December is HIV/AIDs Awareness Month and CGTLive is taking a look at Excision's first-in-human CRISPR therapy trial for people with HIV-1.
A cure for human immunodeficiency virus type 1 (HIV-1) becomes more feasible as advances continue in gene therapy research and the more trials open investigating potential novel treatments for the virus. One such approach among the frontrunners developing a novel therapy for treating HIV-1 is Excision BioTherapeutics’ EBT-101.
EBT-101 uses the CRISPR/Cas9 system, which was recently publicly validated with the FDA approval of Vertex Pharmaceuticals' and CRISPR Therapeutics’ exagamglogene autotemcel (exa-cel), which uses the same gene-editing mechanism and was recently approved under the name Casgevy.1
Exa-cel is an autologous gene-edited cell therapy edited with the use of CRISPR/Cas9 before reinfusion. On the other hand, EBT-101 is a multiplexed, in vivo CRISPR-based gene editing therapy that delivers CRISPR-Cas9 and dual guide RNAs via an adeno-associated virus (AAV), targeting 3 sites in the HIV genome for excision, with the intention of minimizing viral escape.
“Having spoken to some clinicians, they realized that only a handful of people in the world have been cured of HIV ever, so they understand the transformative nature of the therapy. And we believe that the trial will provide important information on the path to a potential functional cure for people living with HIV and meets an area of high unmet medical need. It’s really exciting that we have this groundbreaking therapy for infectious diseases," TJ Cradick, chief scientific officer, Excision BioTherapeutics, told CGTLive.
EBT-101 is being evaluated in an open-label, multicenter, phase 1/2 clinical trial (NCT05144386). The trial has a planned enrollment of 9 male patients aged 18 years to 60 years with documented chronic HIV-1 infection. Participants must be on stable HIV suppression on ART with CD4+ T cells > 500 cells/uL for at least 1 year and low anti-AAV9 neutralizing antibody titers. Patients are additionally required to have a body weight between 45 and 90 kg (inclusive) and must be vaccinated for N. meningitidis and COVID-19. Patients who have had drug resistance to 2 or more classes of ART within the past 5 years, patients with more than 1 change in ART due to virologic failure in the past 2 years, and patients receiving long-acting injectable ART will be excluded from the study, as will patients with anti-AAV9 serum neutralizing antibodies greater than 1:20 titer. Patients with a history of HIV dementia or HIV-related cardiac disease, HIV-related kidney disease with abnormal renal function, or HIV-related opportunistic infections within the past 2 years will also be excluded. Additional exclusion criteria relate to past treatments and health status. FIGURE
Participants receive 7 days of immunosuppression with dexamethasone starting 24 hours before IV EBT-101 administration of 1 of 3 dose-levels, depending on their cohort. Participants will be followed up for 48 weeks posttreatment and will be assessed for sustained viral suppression off ART in an analytical treatment interruption starting at week 12 with weekly assessments for adverse events, HIV viral rebound, and changes in CD4+ T cell count. Other measures of biodistribution, pharmacodynamics, and efficacy will also be evaluated. The study is taking place at multiple locations in the United States and is expected to be completed in March 2025. Participants will also be enrolled in a long-term follow-up study (NCT05143307), which will follow the patients for up to 15 years.
The trial dosed its first patient in September 2022 and was granted Fast Track designation by the FDA in July 2023.2,3 The most recent data from the trial were from the first 3 treated patients and were released in October 2023 at the European Society of Gene & Cell Therapy (ESGCT) meeting.4
These participants, treated in cohort A at the first dose level, were treated safely with no serious AEs or dose-limiting toxicities. There were 4 mild AEs possibly or definitely related to EBT-101 which resolved without intervention and 12 mild AEs. There were no infusion-related reactions, and no complement-mediated toxicity, or withdrawals during intravenous administration. Two participants had transient and reversible transaminase elevations. EBT-101 was detectable in blood at 4 weeks in every participant with peripheral exposure. There has been no evidence of horizontal transmission of gene vector shedding in 2 tissue compartments associated with male reproductive function. Excision plans to dose escalate to the 3.0x1012 vg/kg dose in the fourth quarter of 2023, with more data to come in 2024.
“A major barrier to curing HIV is viral latency, which is defined as the persistence of integrated proviral DNA that is replication competent. Although antiretroviral therapy (ART) effectively suppresses viral replication and prevents disease progression to AIDS, long-term treatment with ART does not eliminate latent HIV and people living with HIV on suppressive ART have significant ART-related side effects and non-AIDS-related comorbidities and malignancies,” Rachel M. Presti, MD, PhD, Professor of Medicine, and medical director, Infectious Disease Clinical Research Unit, Washington University School of Medicine, St. Louis, said during her presentation of the data.4