Polymers fight HIV: potent (pro)drugs identified through parallel automated synthesis

Progress in Treatment and Diagnostics of Infectious Disease with Polymers

In this era of advanced technology and innovation, infectious diseases still cause significant morbidity and mortality, which need to be addressed. Despite overwhelming success in the development of vaccines, transmittable diseases such as tuberculosis and AIDS remain unprotected, and the treatment is challenging due to frequent mutations of the pathogens. Formulations of new or existing drugs with polymeric materials have been explored as a promising new approach. Variations in shape, size, surface charge, internal morphology, and functionalization position polymer particles as a revolutionary material in healthcare. Here, an overview is provided of major diseases along with statistics on infection and death rates, focusing on polymer-based treatments and modes of action. Key issues are discussed in this review pertaining to current challenges and future perspectives.

The evolution of nucleosidic analogues: self-assembly of prodrugs into nanoparticles for cancer drug delivery

Nucleoside and nucleotide analogs are essential tools in our limited arsenal in the fight against cancer. However, these structures face severe drawbacks such as rapid plasma degradation or hydrophilicity, limiting their clinical application. Here, different aspects of nucleoside and nucleotide analogs have been exposed, while providing their shortcomings. Aiming to improve their fate in the body and combating their drawbacks, two different approaches have been discussed, the prodrug and nanocarrier technologies. Finally, a novel approach called "PUFAylation" based on both the prodrug and nanocarrier technologies has been introduced, promising to be the supreme method to create a novel nucleoside or nucleotide analog based formulation, with enhanced efficacy and highly reduced toxicity.

Advanced Prodrug Strategies in Nucleoside and Non-Nucleoside Antiviral Agents: A Review of the Recent Five Years

Background: Poor pharmacokinetic profiles and resistance are the main two drawbacks from which currently used antiviral agents suffer, thus make them excellent targets for research, especially in the presence of viral pandemics such as HIV and hepatitis C. Methods: The strategies employed in the studies covered in this review were sorted by the type of drug synthesized into ester prodrugs, targeted delivery prodrugs, macromolecular prodrugs, other nucleoside conjugates, and non-nucleoside drugs. Results: Utilizing the ester prodrug approach a novel isopropyl ester prodrug was found to be potent HIV integrase inhibitor. Further, employing the targeted delivery prodrug zanamivir and valine ester prodrug was made and shown a sole delivery of zanamivir. Additionally, VivaGel, a dendrimer macromolecular prodrug, was found to be very efficient and is now undergoing clinical trials. Conclusions: Of all the strategies employed (ester, targeted delivery, macromolecular, protides and nucleoside analogues, and non-nucleoside analogues prodrugs), the most promising are nucleoside analogues and macromolecular prodrugs. The macromolecular prodrug VivaGel works by two mechanisms: envelope mediated and receptor mediated disruption. Nucleotide analogues have witnessed productive era in the recent past few years. The era of non-interferon based treatment of hepatitis (through direct inhibitors of NS5A) has dawned.

Synthetic Macromolecular Antibiotic Platform for Inhalable Therapy against Aerosolized Intracellular Alveolar Infections

Lung-based intracellular bacterial infections remain one of the most challenging infectious disease settings. For example, the current standard for treating Franciscella tularensis pneumonia (tularemia) relies on administration of oral or intravenous antibiotics that poorly achieve and sustain pulmonary drug bioavailability. Inhalable antibiotic formulations are approved and in clinical development for upper respiratory infections, but sustained drug dosing from inhaled antibiotics against alveolar intracellular infections remains a current unmet need. To provide an extended therapy against alveolar intracellular infections, we have developed a macromolecular therapeutic platform that provides sustained local delivery of ciprofloxacin with controlled dosing profiles. Synthesized using RAFT polymerization, these macromolecular prodrugs characteristically have high drug loading (16-17 wt % drug), tunable hydrolysis kinetics mediated by drug linkage chemistry (slow-releasing alkyllic vs fast-releasing phenolic esters), and, in general, represent new fully synthetic nanotherapeutics with streamlined manufacturing profiles. In aerosolized and completely lethal F.t. novicida mouse challenge models, the fast-releasing ciprofloxacin macromolecular prodrug provided high cure efficiencies (75% survival rate under therapeutic treatment), and the importance of release kinetics was demonstrated by the inactivity of the similar but slow-releasing prodrug system. Pharmacokinetics and biodistribution studies further demonstrated that the efficacious fast-releasing prodrug retained drug dosing in the lung above the MIC over a 48 h period with corresponding C_max/MIC and AUC_0-24h/MIC ratios being greater than 10 and 125, respectively; the thresholds for optimal bactericidal efficacy. These findings identify the macromolecular prodrug platform as a potential therapeutic system to better treat alveolar intracellular infections such as F. tularensis, where positive patient outcomes require tailored antibiotic pharmacokinetic and treatment profiles.

Macromolecular Prodrugs of Ribavirin: Structure-Function Correlation as Inhibitors of Influenza Infectivity

The requirement for new antiviral therapeutics is an ever present need. Particularly lacking are broad spectrum antivirals that have low toxicity. We develop such agents based on macromolecular prodrugs whereby both the polymer chain and the drug released from the polymer upon cell entry have antiviral effects. Specifically, macromolecular prodrugs were designed herein based on poly(methacrylic acid) and ribavirin. Structure-function parameter space was analyzed via the synthesis of 10 polymer compositions varied by molar mass and drug content. Antiviral activity was tested in cell culture against both low and high pathogenic strains of influenza. Lead compounds were successfully used to counter infectivity of influenza in chicken embryos. The lead composition with the highest activity against influenza was also active against another respiratory pathogen, respiratory syncytial virus, providing opportunity to potentially treat infection by the two pathogens with one antiviral agent. In contrast, structure-function activity against the herpes simplex virus was drastically different, revealing limitations of the broad spectrum antiviral agents based on macromolecular prodrugs.

A prodrug micellar carrier assembled from polymers with pendant farnesyl thiosalicylic acid moieties for improved delivery of paclitaxel

In order to achieve enhanced and synergistic delivery of paclitaxel (PTX), a hydrophobic anticancer agent, two novel prodrug copolymers, POEG15-b-PFTS6 and POEG15-b-PFTS16 composed of hydrophilic poly(oligo(ethylene glycol) methacrylate) (POEG) and hydrophobic farnesylthiosalicylate (FTS, a nontoxic Ras antagonist) blocks, were synthesized. Both POEG-b-PFTS polymers were able to form micelles with intrinsic antitumor activity in vitro and in vivo. Employing these micelles as a carrier to load PTX, their drug loading capacity, stability, in vivo biodistribution and tumor inhibition effect were evaluated. PTX/POEG15-b-PFTS16 mixed micelles exhibited an excellent stability of 9days at 4°C with a PTX loading capacity of 8.2%, which was more effective than PTX/POEG15-b-PFTS6 mixed micelles. In vivo biodistribution data showed that DiR-loaded POEG-b-PFTS micelles were more effectively localized in the tumor than in other organs. Moreover, both PTX/POEG-b-PFTS micelles showed significantly higher antitumor activity than Taxol in a 4T1.2 murine breast tumor model, and the tumor inhibition and animal survival followed the order of PTX/POEG15-b-PFTS16>PTX/POEG15-b-PFTS6>POEG15-b-PFTS16>Taxol≈POEG15-b-PFTS6. Our data suggest that POEG-b-PFTS micelles are a promising anticancer drug carrier that warrants more studies in the future.

STATEMENT OF SIGNIFICANCE

Polymerization of drug-based monomer represents a facile and precise method to obtain well-defined polymeric prodrug amphiphiles. Currently, most reports largely focus on the synthesis methods and the biophysical properties. There is limited information about their anti-tumor activity and delivery function as prodrug carriers in vitro and in vivo. In this manuscript, we report the development of two novel prodrug copolymers, POEG15-b-PFTS6 and POEG15-b-PFTS16 composed of hydrophilic poly(oligo(ethylene glycol) methacrylate) (POEG) and hydrophobic farnesylthiosalicylate (FTS, a nontoxic Ras antagonist) blocks. Both POEG-b-PFTS polymers were able to self-assemble into nano-sized micelles with intrinsic antitumor activity in vitro and in vivo. More importantly, POEG-b-PFTS polymers were effective in forming stable mixed micelles with various anticancer agents including PTX, DOX, docetaxel, gefitinib, and imatinib. Delivery of PTX via our new carrier led to significantly improved antitumor activity, suggesting effective PTX/FTS combination therapy. We believe that our study shall be of broad interest to the readers in the fields of biomaterials and drug delivery.

Polyanionic Macromolecular Prodrugs of Ribavirin: Antiviral Agents with a Broad Spectrum of Activity

Macromolecular prodrugs are developed as multiarmed agents against diverse viral pathogens. Lead candidates inhibit infectivity and replication of HIV, Ebola, influenza, measles, RSV, etc-thus being broad-spectrum antiviral agents.

Biomedical applications of polymers derived by reversible addition - fragmentation chain-transfer (RAFT)

RAFT- mediated polymerization, providing control over polymer length and architecture as well as facilitating post polymerization modification of end groups, has been applied to virtually every facet of biomedical materials research. RAFT polymers have seen particularly extensive use in drug delivery research. Facile generation of functional and telechelic polymers permits straightforward conjugation to many therapeutic compounds while synthesis of amphiphilic block copolymers via RAFT allows for the generation of self-assembled structures capable of carrying therapeutic payloads. With the large and growing body of literature employing RAFT polymers as drug delivery aids and vehicles, concern over the potential toxicity of RAFT derived polymers has been raised. While literature exploring this complication is relatively limited, the emerging consensus may be summed up in three parts: toxicity of polymers generated with dithiobenzoate RAFT agents is observed at high concentrations but not with polymers generated with trithiocarbonate RAFT agents; even for polymers generated with dithiobenzoate RAFT agents, most reported applications call for concentrations well below the toxicity threshold; and RAFT end-groups may be easily removed via any of a variety of techniques that leave the polymer with no intrinsic toxicity attributable to the mechanism of polymerization. The low toxicity of RAFT-derived polymers and the ability to remove end groups via straightforward and scalable processes make RAFT technology a valuable tool for practically any application in which a polymer of defined molecular weight and architecture is desired.

Disulfide reshuffling triggers the release of a thiol-free anti-HIV agent to make up fast-acting, potent macromolecular prodrugs

The release of azidothymidine from macromolecular prodrugs was designed to respond to the intracellular disulfide reshuffling. This drug has no thiol groups, and a response to this trigger was engineered using a self-immolative linker. The resulting formulations were fast-acting, efficacious, and highly potent with regards to suppressing the infectivity of the virus.

Macromolecular prodrugs of ribavirin: towards a treatment for co-infection with HIV and HCV

Human immunodeficiency virus (HIV) and hepatitis C virus (HCV) represent tremendous healthcare burdens with a large proportion of patients hosting the two viruses at the same time. An altered hepatic function and immunity as well as cross-interference of drugs make treatment of co-infection increasingly challenging. Herein we report the first design of macromolecular prodrugs (MP) with concurrent success in fighting HIV and alleviating hepatitis (liver inflammation). To achieve this, polymer compositions were systematically screened in a broad range of molar mass and content of ribavirin - a broad spectrum antiviral agent. For the first time, we report that ribavirin is efficacious in fighting HIV and in the form of MP, the treatment is safe, both in terms of lack of association of ribavirin with red blood cells and lack of toxicity upon cellular internalization. The lead polymer compositions were also potent in anti-inflammatory assays with relevance to viral hepatitis - thus making up formulations with potential for treatment of co-infection with HIV and HCV.

One pot synthesis of higher order quasi-block copolymer librariesviasequential RAFT polymerization in an automated synthesizer

The utility of automated high-throughput methods for the one pot synthesis of functional polymers of increased complexity is reported.