Q&A: University of Portsmouth discusses a new stealth polymer

After the University of Portsmouth announced a new ‘stealth’ polymer that is a promising alternative for delivering drugs around the body, Medical Plastics News spoke to Dr Farah El Mohtadi, senior lecturer in pharmaceutical sciences for the School of Pharmacy and Biomedical Sciences, for more information. 

What is so unique about this new polymer? 

This new polymer (PTGG) is unique because it has demonstrated significant advantages over the current benchmark PEG and as a multifunctional, biodegradable stealth-polymer, offering an attractive alternative to PEG. The antioxidant and cryo/lyoprotective properties offer significant formulation/processing advantages to industry while the antioxidant/anti-inflammatory properties are highly attractive for e.g. anti-inflammatory protein-conjugates where a synergistic effect can be reasonably assumed, or for oxidation-sensitive proteins, e.g. galectin-1. PTGG therefore represents an important milestone in the advent of functional stealth polymers.   

What is the importance of having a stealth polymer? 

Delivery of therapeutics such as small molecules, peptides, and proteins, in their native form, is limited due to their poor stability, low solubility, and short in vivo circulation. These challenges in drug delivery lead to decreased therapeutic efficacy and increased risk of off-target toxicity. Various materials, mostly stealth polymers have been previously designed to deliver drugs. The “stealth” properties of these polymers improve solubility and stability of drugs and reduces their premature clearance from the body.  

How is it safe for delivering drugs around the body? 

We have assessed this polymer’s cytotoxicity and its potential to activate complement system. PTGG displayed a toxicity profile almost identical to that of PEG that is FDA approved and currently available in the market. Therefore, it is safe to be used for delivery of drugs and therapeutic proteins. 

What’s the importance of not being detected by immune systems? 

The presence of anti-protein or anti-polymer antibodies is correlated with reduced or ameliorated efficacy of the therapeutic agent due to enhanced clearance or hypersensitivity reactions. Being able to shield antigenic portions of the protein from recognition would therefore reduce immunogenicity and in turn increase plasma half-life.  

What would this material be used for? 

PTGG is a novel stealth polymer that can be used as a nanocarrier delivery system for different drugs (hydrophobic or hydrophilic). Additionally, due to its potent anti-inflammatory nature, we strongly believe PTGG is an exciting candidate for conjugating therapeutic proteins used to target inflammatory diseases and other pathologies characterised by high ROS levels.   

This polymer can also be used to stabilise nylon-degrading enzymes. 

How can this change the way the industry delivers drugs? 

Pharmaceutical companies are now producing different protein-based therapeutics (biologicals) including antibodies against specific receptors or growth factors, or actives used in e.g. enzyme replacement therapies (ERTs), or agonists/antagonists such as G-CSF (Filgrastin). Their performance, however, is often hampered by inefficiencies in their production, preservation and/or storage as well as denaturation by proteolysis and oxidation. Using PTGG to conjugate these proteins will improve their pharmacokinetics and storage. We believe that our findings strongly position PTGG as a stealth polymer of the future, from both manufacturing and therapeutic standpoints.