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A critical mediator of pathogenicity associated with S. aureus bacterial infection is a toxin protein called ‘alpha-toxin’. S. aureus alphatoxin attacks and destroys human host cells, including the critical human immune cells that are mobilized to fight the invading pathogen.  AR-301 (SalvecinTM) is a fully human monoclonal IgG1 antibody specifically targeting S. aureus alpha-toxin. Upon binding AR-301 represses functional toxin pore formation leading to protection of host cells from alpha-toxin dependent destruction.  Its mode of action is independent of the antibiotic resistance profile of S. aureus, hence it is active against infections caused by both MRSA and MSSA. When testing the therapeutic activity of AR-301 in preclinical animal studies of localized and systemic infection, administration of the monoclonal antibody resulted in reduced bacterial loads and significantly improved the survival rates of infected animals.

AR-301 is being developed as an adjunctive therapy to standard of care antibiotics in hospital-acquired bacterial pneumonia (HABP) and ventilator- associated bacterial pneumonia (VABP) patients. A double-blinded, placebo controlled Phase 1/2a clinical trial was conducted in the US and four European countries evaluating AR-301 in S. aureus HABP & VABP pneumonia patients.  The study met its primary endpoint of safety, and found that VABP patients treated with antibiotics plus AR-301 at all dose levels spent a shorter time under mechanical ventilation as compared to antibiotics plus placebo. Additionally, eradication of S. aureus was also consistently higher in the group receiving AR-301 at all dose levels. Aridis will move forward with plans for late-stage clinical studies of AR-301 in 2017.

Pathogenicity of the bacterial target AR-301: S. aureus. S. aureus is a leading cause of bloodstream, skin, soft tissue and lower respiratory tract infections worldwide, with both hospital-acquired infections and community-acquired infections increasing steadily in recent years. Additionally, treatment of these infections has become more challenging due to the emergence of multi-drug resistant strains. In many developed countries around the world, including the U.S., UK and Japan, resistance to beta-lactam antibiotics in MRSA strains is a major problem in hospitals and other healthcare settings. Notably, the incidence rate of all invasive MRSA infections, including those outside of hospitals, is high compared with other bacterial pathogens, with up to 50% of these infections resulting in death.

In spite of preventive measures and various antibiotic treatment options, there is a clear medical need for alternative anti-infective therapies to treat hospital-acquired S. aureus infections. This high unmet medical need is further supported by the observation that resistant S. aureus strains were identified for every antibiotic after its introduction into clinical practice. In this context, the use of human monoclonal antibodies (mAb) for passive immunotherapy against S. aureus infections represents one new approach to combat the disturbing rise in antibiotic resistance.

AR-301: Fully Human mAb Against Staphylococcus aureus

Bacterias release toxin “sub-units”.

See diagram below.

AR-301 mAb’s Protect Immune Cells from Alpha-toxins by Blocking Their Formation.


Breakthrough Therapies for

Antibiotic Resistant Infections

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