Immunogenicity risk assessment of empty capsids present in adeno-associated viral vectors using predictive innate immune responses.

Immunogenicity of gene therapy and the impacts on safety and efficacy are of increasing interest in the pharmaceutical industry. Unique structural aspects of gene therapy delivery vectors, such as adeno-associated viral (AAV) vectors, are expected to activate the innate immune system. The risk of innate immune activation is critical to understand due to the potential impacts on safety and on subsequent adaptive immune responses.

Immunogenicity of Protein Pharmaceuticals.

Protein therapeutics have drastically changed the landscape of treatment for many diseases by providing a regimen that is highly specific and lacks many off-target toxicities. The clinical utility of many therapeutic proteins has been undermined by the potential development of unwanted immune responses against the protein, limiting their efficacy and negatively impacting its safety profile. This review attempts to provide an overview of immunogenicity of therapeutic proteins, including immune mechanisms and factors influencing immunogenicity, impact of immunogenicity, preclinical screening methods, and strategies to mitigate immunogenicity.

Subcutaneous administration of Lyso-phosphatidylserine nanoparticles induces immunological tolerance towards Factor VIII in a Hemophilia A mouse model.

A major complication with enzyme replacement therapy of Factor VIII (FVIII) in Hemophilia A (HA) is the development of anti-drug antibodies. Recently, we have shown that FVIII administration in the presence of heterogeneous phosphatidylserine (PS) nanoparticles derived from a natural source induces tolerance to FVIII, suggesting that PS converts an immunogen to a tolerogen. However, the specific structural features responsible for the immune-regulatory properties of PS is unclear.

Phosphatidylserine Is Not Just a Cleanup Crew but Also a Well-Meaning Teacher.

Phosphatidylserine (PS) exposure during apoptosis leads to silent clearance of cells without adverse immune reactions to self-proteins. Given the biological functions of PS in cellular cleanup and global immunosuppression, we hypothesized that administration of PS-protein complexes would reduce immunogenicity. Here, we report that exposing Pompe disease mice to acid alpha glucosidase (rhGAA) with PS or immunosuppressant dexamethasone resulted in lower anti-rhGAA antibodies than in animals receiving rhGAA alone.

Challenges and Opportunities for the Subcutaneous Delivery of Therapeutic Proteins.

Biotherapeutics is a rapidly growing drug class, and over 200 biotherapeutics have already obtained approval, with about 50 of these being approved in 2015 and 2016 alone. Several hundred protein therapeutic products are still in the pipeline, including interesting new approaches to treatment. Owing to patients' convenience of at home administration and reduced number of hospital visits as well as the reduction in treatment costs, subcutaneous (SC) administration of biologics is of increasing interest.

Phosphatidylserine Converts Immunogenic Recombinant Human Acid Alpha-Glucosidase to a Tolerogenic Form in a Mouse Model of Pompe Disease.

Development of unwanted immune responses against therapeutic proteins is a major clinical complication. Recently, we have shown that exposure of Factor VIII in the presence of phosphatidylserine (PS) induces antigen-specific hyporesponsiveness to Factor VIII rechallenge, suggesting that PS is not immune suppressive, but rather immune regulatory in that PS converts an immunogen to a tolerogen. Since PS is exposed in the outer leaflet during apoptosis, we hypothesize that PS imparts tolerogenic activity to this natural process.

Effect of Biophysical Properties of Phosphatidylserine Particle on Immune Tolerance Induction Toward Factor VIII in a Hemophilia A Mouse Model.

A major complication in the replacement therapy of Factor VIII (FVIII) for Hemophilia A is the development of unwanted immune responses. Previous studies from our laboratory have shown that pretreatment of FVIII in the presence of phosphatidylserine (PS) resulted in hyporesponsiveness to subsequent administration of FVIII alone, due to the ability of PS to convert an immunogen to a tolerogen. We investigated the importance of biophysical properties of PS liposomes on its ability to convert an immunogen to a tolerogen.

Soy Phosphatidylinositol-Containing Lipid Nanoparticle Prolongs the Plasma Survival and Hemostatic Efficacy of B-domain-Deleted Recombinant Canine Factor VIII in Hemophilia A Dogs.

Soy phosphatidylinositol (PI)-containing lipid nanoparticles prolong plasma survival, improve hemostatic efficacy, and decrease immunogenicity of human B-domain-deleted factor VIII (BDD FVIII) in hemophilia A (HA) mice. We hypothesize that PI-associated BDD FVIII is more potent than the free protein and, using mathematical modeling, have projected that PI-associated BDD FVIII could be used for once-weekly prophylactic dosing in patients. To facilitate translation to the clinic, comparative plasma survival and ex vivo efficacy of PI-associated recombinant canine FVIII (PI-rcFVIII) were evaluated in HA dogs.

O-phospho-l-serine mediates hyporesponsiveness toward FVIII in hemophilia A-murine model by inducing tolerogenic properties in dendritic cells.

The clinical use of therapeutic proteins can be complicated by the development of anti-product antibodies. We have previously observed that O-phospho-l-serine (OPLS) reduced antibody response to FVIII in Hemophilia-A (HA) mice. However, the mechanism underlying this observation is not clear.