MedicalResearch.com Interview with:
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Synthetic Biologics, Inc.[/caption]
Sheila Connelly, PhD
Vice President, Research
Synthetic Biologics, Inc.
MedicalResearch.com: What is the background for this study?
Response: Synthetic Biologics, Inc. is focused on the protection and preservation of the gut microbiome which is the diverse collection of microorganisms that live in the intestinal tract. We are learning that the gut microbiome plays a key role in health. Negative changes to the microbiome, called dysbiosis, are linked to disease states including allergies, autism, and obesity, among a rapidly growing list of other conditions. A consequence of using antibiotics is that, in addition to fighting the bacterial infection being treated, they also kill the gut microbiota. The space left in the gut by the dead bacteria allows other surviving bacteria, many times opportunistic pathogens or microbes that are resistant to multiple antibiotics, to overgrow and fill the open niches. Exposure to antibiotics, particularly broad-spectrum antimicrobials, such as penicillins and cephalosporins, is a major risk factor for acquiring a potentially deadly
Clostridium difficile infection.
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Dr. Sheila Connelly[/caption]
Another consequence of antibiotic use is the emergence of antibiotic-resistant organisms. Widespread use of antibiotics provides selective pressure for the evolution of lethal, multi-drug resistant pathogens, termed “nightmare bacteria”. The gut microbiome acts as a reservoir of antibiotic resistance that can be triggered, by antibiotic exposure, to acquire and propagate resistance genes.
A way to protect the microbiome and reduce antibiotic resistance is to limit exposure of the gut microbiota to antibiotics. To this end, we developed an antibiotic inactivation strategy using a beta-lactamase enzyme to degrade beta-lactam antibiotics in the GI tract before they can harm the gut microbiome. Beta-lactamases are naturally-occurring bacterial enzymes that confer resistance to beta-lactams, the most widely used broad spectrum antibiotics, and their presence is normally considered an obstacle to efficacious infection control. We took advantage of the highly efficient antibiotic degradation activity of a beta-lactamase and developed SYN-004 (ribaxamase). Ribaxamase is a beta-lactamase engineered to inactivate penicillins and most cephalosporins, formulated for oral delivery, and intended for use with IV beta-lactam antibiotics to degrade the antibiotics in the GI tract to protect the microbiome.
Ribaxamase was demonstrated to significantly reduce the occurrence of
C. difficile disease in a recently completed Phase 2b clinical study. The study met its primary endpoint by demonstrating that ribaxamase, when delivered orally with IV ceftriaxone, significantly reduced
C. difficile disease in patients treated for a respiratory tract infection. Ribaxamase also resulted in a significant reduction in new colonization by vancomycin-resistant enterococcus (VRE).
For the current study, pig models of antibiotic-mediated gut dysbiosis were established using three classes of beta-lactam antibiotics, a cephalosporin, ceftriaxone, a penicillin, amoxicillin, and a carbapenem, ertapenem. The ceftriaxone model was used to evaluate the protective effect of ribaxamase on the microbiome and the amoxicillin and ertapenem models are intended for evaluation of pipeline products.
Jean-Marc Steens, M.D.
Chief Medical Officer of Abivax
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Antiretroviral therapy (ART) has had an enormous impact on the HIV pandemic since its introduction almost 20 years ago. Most patients treated with ART achieve undetectable or near undetectable plasma levels of the virus. This means that although HIV is controlled, it is not completely eliminated. The virus remains in the body, usually contained in dormant cells (known as the HIV reservoir) that are widely distributed, including to the central nervous system, the gut mucosa, the lymph nodes and other sites. If ART is stopped, the virus rebounds. The goal of any curative therapy would be to eliminate the virus or ensure there is sustained remission in the absence of ART, which until now have been unsuccessful.
Abivax’s Phase 2 clinical study with ABX464 demonstrated, for the first time, a reduction in HIV reservoirs in chronically infected HIV patients as measured by total HIV DNA detected in peripheral blood mononuclear cells (PBMCs).
In the ABX464-004 trial, 30 HIV patients received either ABX464 or matching placebo in addition to their current antiretroviral treatment over 28 days. The viral load at the start of the study was well controlled with boosted darunavir. After the 28-day treatment period, all treatments were interrupted until viral load rebound. Baseline and day 28 blood samples were taken to assess the potential effect of ABX464 on the HIV reservoir in PBMCs.
Safety was the primary endpoint in the trial. ABX464 was well tolerated, with no severe adverse events in the treatment group. Amongst evaluable patients (4 placebo and 14 ABX464-treated patients), a reduction in viral DNA copies/mPBMCs was observed in 7/14 treated patients (mean change of -40%, ranging from -27% to -67%) and no responders were observed in the placebo group. Responders were defined as patients who had a decrease greater than 25% in total HIV DNA in PBMCs and a reduction of at least 50 copies.
Total HIV DNA in PBMC has been validated as a widely accepted biomarker for measuring the HIV reservoir. Specifically, in untreated patients, total HIV DNA load influences the course of the infection and is therefore clinically relevant. In addition, a correlation exists between the pool of HIV-1 DNA and the replication-competent reservoir.
