Alopexx Pharmaceuticals, LLC was founded in 2006 to develop and commercialize a promising new alternative for the treatment and prevention of staphylococcal and other serious bacterial infections. The company obtained the rights for all antibodies developed against a proprietary antigenic target – dPNAG. That target, developed by Dr. Gerald B. Pier and colleagues at Harvard Medical School, holds great promise for the treatment of a wide range of infections. The Company’s lead compound is a fully human monoclonal IgG1 antibody (F598) directed against dPNAG that has the potential to serve as an alternative to antibiotics in the prevention and treatment of serious bacterial infections.
For bacterial pathogens, surface capsules, often composed of highly varied carbohydrate polymers, have been used successfully to vaccinate humans against Streptococcus pneumonia, Hemophilus influenzae type b, Neisseria meningitidis and Salmonella enterica serovar typhi. However, efficacy is limited to the capsule types included in vaccines or targeted by monoclonal antibodies.
In contrast to other carbohydrates the β-1→6-linked polymeric-N-acetyl glucosamine (PNAG) polysaccharide has been discovered to be broadly expressed and highly conserved on the surface of a wide range of pathogenic microbial species. The synthesis of PNAG by both gram-positive and gram-negative bacterial pathogens, as well as fungal filarial and protozoan pathogens, suggests an important role for this molecule in microbial biology. Identification of PNAG on a large number of pathogens suggests that it could serve as a therapeutic target against many different microbes.2
|PNAG Expression Determination||Bacterial Species|
|Genes for biosynthetic proteins identified, polysaccharide isolated, immunologic confirmation of PNAG expression||
|Genes for biosynthetic proteins identified and immunologic confirmation of PNAG expression||
|Immunologic confirmation of PNAG expression only||
Therapeutic Potential of Targeting PNAG
As summarized in the table below the efficacy of targeting of dPNAG has been demonstrated in more than 18 animal models of infection against over 10 different microbial pathogens.
Efficacy of Targeting dPNAG – Summary of In Vivo Studies
|Mouse||S. aureus||Lethal peritonitis
|E. coli||Lethal peritonitis
Oral infection with Shiga-toxin producing strains
|Burkholderia cenocepacia||Lethal peritonitis|
|N. meningitidis serogroup B||Neonatal infection|
|S. pyogenes||Lethal infections|
|L. monocytogenes||Lethal infections|
|P. berghei ANKA||Malaria|
|Horses||R. equi||Pneumonia in foals – immunity transferred from vaccinated mares|
Protection associated with achieving high titer to PNAG
F598 Clinical Development
F598 is an intact, fully human IgG1 monoclonal antibody directed against PNAG. It has the potential to serve as an alternative to antibiotics in the treatment and prevention of infections caused by a wide range of bacterial, fungal, filarial and protozoan organisms that express PNAG on their surface. Unlike antibiotics, monoclonal antibodies are not expected to lead to the development of bacterial resistance to therapy. PNAG has been found to be a critical factor in the virulence and immune response to infections. Bacterial strains that cannot produce PNAG generally have a significantly reduced ability to cause infections. The antibody works by inducing either complement-dependent, direct bactericidal killing of gram-negative organisms or via opsonophagocytosis using complement and individuals own white blood cells.
A Phase I trial of F598 was performed by Alopexx in 2010 enrolling 20 healthily adults. Pharmacokinetic analysis showed long elimination half lives (~ 20-30 days), low systemic clearance, a low volume of distribution and a dose-dependent increase in serum MAb levels. No relevant immunogenicity related to study compound (as measured by detection of antibodies against F598 in human serum) was observed.
Functional activity of the antibody, as measured by opsonophagocytic assays, was seen at all doses up to Day 50 the last time point in the study, suggesting that single administration of F598 could provide protection for a prolonged period of time.
Opsonic phagocytic activity (OPA) over time
Plans for Phase II clinical trials are underway, including pilot studies in gonorrhea, tuberculosis and malaria. All of these organisms express PNAG and pre-clinical data suggests that F598 will be effective in treating and preventing infections from all 3 of these diverse pathogens.