SBIR Phase I: Development, Optimization and Analysis of Poly (Carboxy Betaine) Bio-conjugates to L-Asparagianse as PEGylation Alternatives

This SBIR Phase I project aims to develop a superior alternative to the current frontline treatment for children?s Acute Lymphoblastic Leukemia (ALL). The primary treatment option has a host of negative side effects resulting from the use of poly(ethylene glycol) (PEG) conjugated to the L-asparaginase enzyme. Antibodies made against this drug can cause the body to eliminate it rapidly or result in a severe allergic reaction and even death, particularly after multiple injections (induced immunity). PEG has been utilized extensively in the food, cosmetics and agricultural industries. As a result, the majority of healthy people test positive for anti-PEG antibodies (pre-existing immunity), causing the elimination of PEG-modified drugs before their action. The technology proposed here utilizes the non-essential amino acid, glycine betaine, to construct a new poly(carboxybetaine) (PCB) polymer for conjugation that is not recognized as a foreign molecule by the immune system. Therefore, it will maintain function and mitigate the negative side effects associated with the immune system that are attributed to the current therapy. Additionally, therapy with PCB conjugates avoids pre-existing immunity to PEG and ensures treatment efficacy. The primary goal of this work is to show that the technology is superior to and safer than the current PEG technology. The technical innovation at the foundation of this work is the zwitterionic, poly(carboxybetaine) (PCB) polymer and its use as a bio-conjugate to replace the widely used poly(ethylene glycol) (PEG) for the treatment of children?s Acute Lymphoblastic Leukemia (ALL). The unique properties of the zwitterionic polymer impart remarkable characteristics to the bio-conjugate that truly eliminates immunogenicity. The current frontline treatment suffers from Accelerated Blood Clearance (ABC) in patients, which has been attributed to induced or pre-existing anti-PEG antibodies. This Phase I project aims to demonstrate that PCB is a preferable bio-conjugation polymer to PEG for the modification of L-asparaginase with regard to extended half-life and decreased immunogenicity after multiple doses in mice. To achieve the goals, an optimized PCB L-asparaginase will be developed with regard to polymer length and conjugation density and a multi-dose pharmacokinetic/immunogenicity study will be performed to evaluate its half-life and immune protection in animals. All results will be compared with those from its PEG counterpart. It is expected that PCB L-asparaginase has great potential to eradicate the serious side effects associated with the current therapy. If PCB L-asparaginase proves to be safe and effective, this will lead to more successful outcomes for the treatment of ALL.