Injectable implants for the sustained release of protein and peptide drugs

Towards superior biopolymer gels by enabling interpenetrating network structures: A review on types, applications, and gelation strategies

Gels derived from single networks of natural polymers (biopolymers) typically exhibit limited physical properties and thus have seen constrained applications in areas like food and medicine. In contrast, gels founded on a synergy of multiple biopolymers, specifically polysaccharides and proteins, with intricate interpenetrating polymer network (IPN) structures, represent a promising avenue for the creation of novel gel materials with significantly enhanced properties and combined advantages. This review begins with the scrutiny of newly devised IPN gels formed through a medley of polysaccharides and/or proteins, alongside an introduction of their practical applications in the realm of food, medicine, and environmentally friendly solutions. Finally, based on the fact that the IPN gelation process and mechanism are driven by different inducing factors entwined with a diverse amalgamation of polysaccharides and proteins, our survey underscores the potency of physical, chemical, and enzymatic triggers in orchestrating the construction of crosslinked networks within these biomacromolecules. In these mixed systems, each specific inducer aligns with distinct polysaccharides and proteins, culminating in the generation of semi-IPN or fully-IPN gels through the intricate interpenetration between single networks and polymer chains or between two networks, respectively. The resultant IPN gels stand as paragons of excellence, characterized by their homogeneity, dense network structures, superior textural properties (e.g., hardness, elasticity, adhesion, cohesion, and chewability), outstanding water-holding capacity, and heightened thermal stability, along with guaranteed biosafety (e.g., nontoxicity and biocompatibility) and biodegradability. Therefore, a judicious selection of polymer combinations allows for the development of IPN gels with customized functional properties, adept at meeting precise application requirements.

Injectable hydrogels as emerging drug-delivery platforms for tumor therapy

Tumor therapy continues to be a prominent field within biomedical research. The development of various drug carriers has been propelled by concerns surrounding the side effects and targeting efficacy of various chemotherapeutic drugs and other therapeutic agents. These carriers strive to enhance drug concentration at tumor sites, minimize systemic side effects, and improve therapeutic outcomes. Among the reported delivery systems, injectable hydrogels have emerged as an emerging candidate for the in vivo delivery of chemotherapeutic drugs due to their minimal invasive drug delivery properties. This review systematically summarizes the composition and preparation methodologies of injectable hydrogels and further highlights the delivery mechanisms of diverse drugs using these hydrogels for tumor therapy, along with an in-depth discussion on the optimized therapeutic efficiency of drugs encapsulated within the hydrogels. The work concludes by providing a dynamic forward-looking perspective on the potential challenges and possible solutions of the in situ injectable hydrogels for non-surgical and real-time diagnostic applications.

Polymer Delivery Systems for Long-Acting Antiretroviral Drugs

The success of long-acting (LA) drug delivery systems (DDSs) is linked to their biocompatible polymers. These are used for extended therapeutic release. For treatment or prevention of human immune deficiency virus type one (HIV-1) infection, LA DDSs hold promise for improved regimen adherence and reduced toxicities. Current examples include Cabenuva, Apretude, and Sunlenca. Each is safe and effective. Alternative promising DDSs include implants, prodrugs, vaginal rings, and microarray patches. Each can further meet patients' needs. We posit that the physicochemical properties of the formulation chemical design can optimize drug release profiles. We posit that the strategic design of LA DDS polymers will further improve controlled drug release to simplify dosing schedules and improve regimen adherence.

Biodegradable Long-Acting Injectables: Platform Technology and Industrial Challenges

Long-acting injectables have been used to benefit patients with chronic diseases. So far, several biodegradable long-acting platform technologies including drug-loaded polymeric microparticles, implants (preformed and in situ forming), oil-based solutions, and aqueous suspension have been established. In this chapter, we summarize all the marketed technology platforms and discuss their challenges regarding development including but not limited to controlling drug release, particle size, stability, sterilization, scale-up manufacturing, etc. Finally, we discuss important criteria to consider for the successful development of long-acting injectables.

Enhancement of Oral Bioavailability of Protein and Peptide by Polysaccharide-based Nanoparticles

Oral drug delivery is a prevalent and cost-effective method due to its advantages, such as increased drug absorption surface area and improved patient compliance. However, delivering proteins and peptides orally remains a challenge due to their vulnerability to degradation by digestive enzymes, stomach acids, and limited intestinal membrane permeability, resulting in poor bioavailability. The use of nanotechnology has emerged as a promising solution to enhance the bioavailability of these vital therapeutic agents. Polymeric NPs, made from natural or synthetic polymers, are commonly used. Natural polysaccharides, such as alginate, chitosan, dextran, starch, pectin, etc., have gained preference due to their biodegradability, biocompatibility, and versatility in encapsulating various drug types. Their hydrophobic-hydrophilic properties can be tailored to suit different drug molecules.

Injectable systems for long-lasting insulin therapy

Insulin therapy is the mainstay to treat diabetes characterizedd by hyperglycemia. However, its short half-life of only 4-6 min limits its effectiveness in treating chronic diabetes. Advances in recombinant DNA technology and protein engineering have led to several insulin analogue products that have up to 42 h of glycemic control. However, these insulin analogues still require once- or twice-daily injections for optimal glycemic control and have poor patient compliance and adherence issues. To achieve insulin release for more than one day, different injectable delivery systems including microspheres, in situ forming depots, nanoparticles and composite systems have been developed. Several of these delivery systems have advanced to clinical trials for once-weekly insulin injection. This review comprehensively summarizes the developments of injectable insulin analogs and delivery systems covering the whole field of injectable long-lasting insulin technologies from prototype design, preclinical studies, clinical trials to marketed products for the treatment of diabetes.

Long-acting injectable multipurpose prevention technology for prevention of HIV and unplanned pregnancy

Only condoms are proven to protect against both HIV and unplanned pregnancy, however, poor user acceptability and lack of partner cooperation impede effectiveness. We developed an injectable ultra-long-acting, biodegradable, and removable in-situ forming implant (ISFI) as multipurpose prevention technology (MPT). MPT ISFIs co-formulated an antiretroviral (dolutegravir (DTG)) or cabotegravir (CAB)), and a hormonal contraceptive (etonogestrel (ENG) or medroxyprogesterone acetate (MPA)). All formulations were well-tolerated in mice with no signs of chronic local or systemic inflammation. Plasma CAB and DTG concentrations were above 4× PA-IC90 for 90 days with zero-order and diffusion-controlled absorption, respectively, and no differences when co-formulated with either hormone. Plasma ENG and MPA concentrations were quantifiable for 90 days. Complete removal of CAB/MPA ISFIs resulted in MPA concentrations falling below the limit of quantification after 24 h post-removal, but incomplete CAB elimination from plasma. Collectively, we demonstrated the ability to co-formulate antiretrovirals with contraceptives in an ISFI that is well-tolerated with sustained plasma concentrations up to 90 days.

Engineered therapeutic proteins for sustained-release drug delivery systems

Proteins play a vital role in diverse biological processes in the human body, and protein therapeutics have been applied to treat different diseases such as cancers, genetic disorders, autoimmunity, and inflammation. Protein therapeutics have demonstrated their advantages, such as specific pharmaceutical effects, low toxicity, and strong solubility. However, several disadvantages arise in clinical applications, including short half-life, immunogenicity, and low permeation, leading to reduced drug effectiveness. The structure of protein therapeutics can be modified to increase molecular size, leading to prolonged stability and increased plasma half-life. Notably, the controlled-release delivery systems for the sustained release of protein drugs and preserving the stability of cargo proteins are envisioned as a potential approach to overcome these challenges. In this review, we summarize recent research progress related to structural modifications (PEGylation, glycosylation, poly amino acid modification, and molecular biology-based strategies) and promising long-term delivery systems, such as polymer-based systems (injectable gel/implants, microparticles, nanoparticles, micro/nanogels, functional polymers), lipid-based systems (liposomes, solid lipid nanoparticles, nanostructured lipid carriers), and inorganic nanoparticles exploited for protein therapeutics. STATEMENT OF SIGNIFICANCE: In this review, we highlight recent advances concerning modifying proteins directly to enhance their stability and functionality and discuss state-of-the-art methods for the delivery and controlled long-term release of active protein therapeutics to their target site. In terms of drug modifications, four widely used strategies, including PEGylation, poly amino acid modification, glycosylation, and genetic, are discussed. As for drug delivery systems, we emphasize recent progress relating to polymer-based systems, lipid-based systems developed, and inorganic nanoparticles for protein sustained-release delivery. This review points out the areas requiring focused research attention before the full potential of protein therapeutics for human health and disease can be realized.

Polymeric in situ forming depots for long-acting drug delivery systems

Polymeric in situ forming depots have emerged as highly promising drug delivery systems for long-acting applications. Their effectiveness is attributed to essential characteristics such as biocompatibility, biodegradability, and the ability to form a stable gel or solid upon injection. Moreover, they provide added versatility by complementing existing polymeric drug delivery systems like micro- and nanoparticles. The formulation's low viscosity facilitates manufacturing unit operations and enhances delivery efficiency, as it can be easily administered via hypodermic needles. The release mechanism of drugs from these systems can be predetermined using various functional polymers. To enable unique depot design, numerous strategies involving physiological and chemical stimuli have been explored. Important assessment criteria for in situ forming depots include biocompatibility, gel strength and syringeability, texture, biodegradation, release profile, and sterility. This review focuses on the fabrication approaches, key evaluation parameters, and pharmaceutical applications of in situ forming depots, considering perspectives from academia and industry. Additionally, insights about the future prospects of this technology are discussed.

Injectable cell-targeting fiber rods to promote lipolysis and regulate inflammation for obesity treatment

Obesity has become a worldwide public health problem and continues to be one of the leading causes of chronic diseases. Obesity treatment is challenged by large drug doses, high administration frequencies and severe side effects. Herein, we propose an antiobesity strategy through the local administration of HaRChr fiber rods loaded with chrysin and grafted with hyaluronic acid and AtsFRk fiber fragments loaded with raspberry ketone and grafted with adipocyte target sequences (ATSs). The hyaluronic acid grafts double the uptake levels of HaRChr by M1 macrophages to promote phenotype transformation from M1 to M2 through upregulating CD206 and downregulating CD86 expressions. ATS-mediated targeting and sustained release of raspberry ketone from AtsFRk increase the secretion of glycerol and adiponectin, and Oil red O staining shows much fewer lipid droplets in adipocytes. The combination treatment with AtsFRk and the conditioned media from HaRChr-treated macrophages elevates adiponectin levels, suggesting that M2 macrophages may secrete anti-inflammatory factors to stimulate adipocytes to produce adiponectin. Diet-induced obese mice showed significant weight losses of inguinal (49.7%) and epididymal (32.5%) adipose tissues after HaRChr/AtsFRk treatment, but no effect was observed on food intake. HaRChr/AtsFRk treatment reduces adipocyte volumes, lowers serum levels of triglycerides and total cholesterol and restores adiponectin levels to those of normal mice. In the meantime, HaRChr/AtsFRk treatment significantly elevates the gene expression of adiponectin and interleukin-10 and downregulates tissue necrosis factor-α expression in the inguinal adipose tissues. Thus, local injection of cell-targeting fiber rods and fragments demonstrates a feasible and effective antiobesity strategy through improving lipid metabolism and normalizing the inflammatory microenvironment.

Challenges and opportunities in delivering oral peptides and proteins

INTRODUCTION

Rapid advances in bioengineering enable the use of complex proteins as therapeutic agents to treat diseases. Compared with conventional small molecule drugs, proteins have multiple advantages, including high bioactivity and specificity with low toxicity. Developing oral dosage forms with active proteins is a route to improve patient compliance and significantly reduce production costs. However, the gastrointestinal environment remains a challenge to this delivery path due to enzymatic degradation, low permeability, and weak absorption, leading to reduced delivery efficiency and poor clinical outcomes.

AREAS COVERED

This review describes the barriers to oral delivery of peptides and complex proteins, current oral delivery strategies utilized and the opportunities and challenges ahead to try and circumvent these barriers. Oral protein drugs on the market and clinical trials provide insights and approaches for advancing delivery strategies.

EXPERT OPINION

Although most current studies on oral protein delivery rely on in vitro and in vivo animal data, the safety and limitations of the approach in humans remain uncertain. The shortage of clinical data limits the development of new or alternative strategies. Therefore, designing appropriate oral delivery strategies remains a significant challenge and requires new ideas, innovative design strategies and novel model systems.

Electrospun polymer fibers modified with FK506 for the long-term treatment of acute cardiac allograft rejection in a heart transplantation model

FK506, a first-line immunosuppressant, is routinely administered orally and intravenously following heart transplantation. However, frequent administration can result in a substantial psychological burden to patients, resulting in non-adherence to medication. The purpose of our study is to overcome the disadvantages of systemic drug administration by developing a polymer-based delivery system that is tunable and biodegradable and that can release highly hydrophobic FK506 over extended periods to treat or prevent acute cardiac allograft rejection. Using an electrospinning method, long-acting microfibers were prepared, and FK506 appeared to be continuously released for up to 14 days based on the in vitro release profiles. After implanting the microfiber subcutaneously into the abdominals of transplanted rats, it was found that the infiltration of T cells and macrophages and the secretion of interleukin-2 (IL-2) and IL-1β were significantly reduced compared with those of the free FK506 groups. More importantly, the mean survival time (MST) of the PCL-FK506 group was significantly extended in comparison with that of untreated control recipients and free FK506 (MST of untreated control recipients, free FK506, and PCL-FK506 was 8, 26.1, and 37, respectively). In conclusion, we propose that this drug delivery approach would be suitable for developing long-lasting immunomodulatory agents that prolong cardiac graft survival safely and effectively.

Anionic polysaccharides for stabilization and sustained release of antimicrobial peptides

Chemical and enzymatic in vivo degradation of antimicrobial peptides represents a major challenge for their therapeutic use to treat bacterial infections. In this work, anionic polysaccharides were investigated for their ability to increase the chemical stability and achieve sustained release of such peptides. The investigated formulations comprised a combination of antimicrobial peptides (vancomycin (VAN) and daptomycin (DAP)) and anionic polysaccharides (xanthan gum (XA), hyaluronic acid (HA), propylene glycol alginate (PGA) and alginic acid (ALG)). VAN dissolved in buffer of pH 7.4 and incubated at 37 °C showed first order degradation kinetics with a reaction rate constant k_obs of 5.5 × 10^-2 day^-1 corresponding with a half-life of 13.9 days. However, once VAN was present in a XA, HA or PGA-based hydrogel, k_obs decreased to (2.1-2.3) × 10^-2 day^-1 while k_obs was not affected in an alginate hydrogel and a dextran solution (5.4 × 10^-2 and 4.4 × 10^-2 day^-1). Under the same conditions, XA and PGA also effectively decreased k_obs for DAP (5.6 × 10^-2 day^-1), whereas ALG had no effect and HA even increased the degradation rate. These results demonstrate that the investigated polysaccharides (except ALG for both peptides and HA for DAP) slowed down the degradation of VAN and DAP. DSC analysis was used to investigate on polysaccharide ability to bind water molecules. Rheological analysis highlighted that the polysaccharides containing VAN displayed an increase in G' of their formulations, pointing that the peptides interaction act as crosslinker of the polymer chains. The obtained results suggest that the mechanism of stabilization of VAN and DAP against hydrolytic degradation is conferred by electrostatic interactions between the ionizable amine groups of the drugs and the anionic carboxylate groups of the polysaccharides. This, in turn, results in a close proximity of the drugs to the polysaccharide chain, where the water molecules have a lower mobility and, therefore, a lower thermodynamic activity.

Injectable hydroethanolic physical gels based on Codonopsis pilosula polysaccharide for sustained anticancer drug delivery

The development of biocompatible carriers based on hydroethanolic physical gels for effectively encapsulating and delivering hydrophobic drug molecules is of particular interest. In this paper, we reported a novel hydroethanolic physical gel based on Codonopsis pilosula polysaccharide (CPP) prepared from the roots of C. pilosula. The gelation behaviors of the graded CPP fractions in a water-ethanol solvent system were evaluated, and the physicochemical and mechanical properties of the CPP-based gel (CPP-G) were characterized. The results indicated that CPP-G had consisted of a random physically crosslinked network formed by hydrophobic association of CPP chains and exhibited good mechanical strength, higher shear-thinning sensitivity and rapid, highly efficient self-recovering characteristics, ensuring superior performance in constructing injectable and self-recovering drug-loaded gels. Hydrophobic paclitaxel (PTX) and hydrophilic doxorubicin (DOX) were used as representative drugs to investigate the encapsulation and in vitro release behaviors of CPP-G, which exhibited long-term sustained release properties. Additionally, the evaluation of drug activity in drug-loaded gels further revealed the synergistic effect of CPP-G with the selected drugs on tumor inhibition against 4T1 and MCF-7 breast cancer cell lines. This work evaluated the feasibility of using the natural polysaccharide CPP to construct hydroethanolic physical gels and the applicability of the injectable drug-loaded gels for hydrophobic drug delivery.

Micro-Scale Vacuum Compression Molding as a Predictive Screening Tool of Protein Integrity for Potential Hot-Melt Extrusion Processes

Hot-melt extrusion (HME) is used for the production of solid protein formulations mainly for two reasons: increased protein stability in solid state and/or long-term release systems (e.g., protein-loaded implants). However, HME requires considerable amounts of material even at small-scale (>2 g batch size). In this study, we introduced vacuum compression molding (VCM) as a predictive screening tool of protein stability for potential HME processing. The focus was to identify appropriate polymeric matrices prior to extrusion and evaluation of protein stability after thermal stress using only a few milligrams of protein. The protein stability of lysozyme, BSA, and human insulin embedded in PEG 20,000, PLGA, or EVA by VCM was investigated by DSC, FT-IR, and SEC. The results from the protein-loaded discs provided important insights into the solid-state stabilizing mechanisms of protein candidates. We demonstrated the successful application of VCM for a set of proteins and polymers, showing, in particular, a high potential for EVA as a polymeric matrix for solid-state stabilization of proteins and the production of extended-release dosage forms. Stable protein-polymer mixtures with sufficient protein stability after VCM could be then introduced to a combination of thermal and shear stress by HME and further investigated with regard to their process-related protein stability.

Ultra-long-acting in-situ forming implants with cabotegravir protect female macaques against rectal SHIV infection

Ultra-long-acting delivery platforms for HIV pre-exposure prophylaxis (PrEP) may increase adherence and maximize public health benefit. We report on an injectable, biodegradable, and removable in-situ forming implant (ISFI) that is administered subcutaneously and can release the integrase inhibitor cabotegravir (CAB) above protective benchmarks for more than 6 months. CAB ISFIs are well-tolerated in female mice and female macaques showing no signs of toxicity or chronic inflammation. In macaques, median plasma CAB concentrations exceed established PrEP protection benchmarks within 3 weeks and confer complete protection against repeated rectal SHIV challenges. Implant removal via a small incision in 2 macaques at week 12 results in a 7- to 48-fold decrease in plasma CAB levels within 72 hours. Modeling to translate CAB ISFI dosing suggests that a 3 mL injection would exceed protective benchmarks in humans for over 5 months post administration. Our results support the clinical advancement of CAB ISFIs for ultra-long-acting PrEP in humans.

Long-acting injectable PLGA/PLA depots for leuprolide acetate: successful translation from bench to clinic

The excellent properties of polyesters combined with their ease of synthesis and modification enabled their wide use in the pharmaceutical industry. This has been translated into the approval of several injectable depots for clinical use. Long-acting depots for leuprolide acetate were among the first and most successful examples including Lupron Depot^® and ELIGARD^®. Studying these products is of great interest for researchers in both industry and academia. This will undoubtedly pave the road for the development of new as well as generic long-acting depots for a variety of drugs.

Ocular Delivery of Therapeutic Proteins: A Review

Therapeutic proteins, including monoclonal antibodies, single chain variable fragment (ScFv), crystallizable fragment (Fc), and fragment antigen binding (Fab), have accounted for one-third of all drugs on the world market. In particular, these medicines have been widely used in ocular therapies in the treatment of various diseases, such as age-related macular degeneration, corneal neovascularization, diabetic retinopathy, and retinal vein occlusion. However, the formulation of these biomacromolecules is challenging due to their high molecular weight, complex structure, instability, short half-life, enzymatic degradation, and immunogenicity, which leads to the failure of therapies. Various efforts have been made to overcome the ocular barriers, providing effective delivery of therapeutic proteins, such as altering the protein structure or including it in new delivery systems. These strategies are not only cost-effective and beneficial to patients but have also been shown to allow for fewer drug side effects. In this review, we discuss several factors that affect the design of formulations and the delivery of therapeutic proteins to ocular tissues, such as the use of injectable micro/nanocarriers, hydrogels, implants, iontophoresis, cell-based therapy, and combination techniques. In addition, other approaches are briefly discussed, related to the structural modification of these proteins, improving their bioavailability in the posterior segments of the eye without affecting their stability. Future research should be conducted toward the development of more effective, stable, noninvasive, and cost-effective formulations for the ocular delivery of therapeutic proteins. In addition, more insights into preclinical to clinical translation are needed.

Strontium-loaded hydrogel scaffolds to promote gingival fibroblast function

Dental implant clinical success is dependent on effective peri-implant tissue attachment to the trans-mucosal portion following placement. Modification of transmucosal implant surfaces can improve cellular adhesion and function leading to formation of an effective soft-tissue seal during healing, of which gingival fibroblasts are prominent cells to migrate to repair wounds and crucial for the development of a collagen rich connective tissue. Biocompatible loaded scaffold materials have been developed to allow local release of molecules with effective biological activity. Our previous studies indicate that strontium can promote gingival fibroblast metabolism, decrease apoptosis and support adhesion to titanium healing abutments. In this study, we developed a strontium-loaded alginate hydrogel scaffold which can be easily personalized to fit over any size and shape of implant transmucosal collar or healing abutment. Results indicate that biologically active strontium ions are effectively released from loaded alginate hydrogel material to promote fibroblast viability and migration to repair in vitro wounds similar to that of strontium citrate solution. Overall, this novel strontium-loaded alginate scaffold device displays good biocompatibility and functionality, demonstrating high potential as a system to provide local delivery of strontium to improve peri-implant mucosal healing following implant placement and clinical success.

Basic Salt Additives Modulate the Acidic Microenvironment Around In Situ Forming Implants

There is a growing number of protein drugs, yet their limited oral bioavailability requires that patients receive frequent, high dose injections. In situ forming implants (ISFIs) for controlled release of biotherapeutics have the potential to greatly reduce the injection frequency and improve patient compliance. However, protein release from ISFIs is a challenge due to their proclivity for instability. Specifically, factors such as the acidic microclimate within ISFIs can lead to protein aggregation and denaturation. Basic salts have been shown in PLGA microparticle and microcylinder formulations to significantly reduce protein instability by neutralizing this acidic environment. The overall objective of the study was to demonstrate that basic salts can be used with an ISFI system to neutralize the implant acidification. To this end, the basic salts MgCO3 and Mg(OH)2 were added to a protein-releasing ISFI and the effect on drug release, pH, implant swelling, implant diffusivity, and implant erosion were evaluated. Either salt added at 3 wt% neutralized the acidic environment surrounding the implants, keeping the pH at 6.64 ± 0.03 (MgCO₃) and 6.46 ± 0.11 (Mg(OH)₂) after 28 day compared to 3.72 ± 0.05 with no salts added. The salts initially increased solution uptake into the implants but delayed implant degradation and erosion. The 3 wt% Mg(OH)₂ formulation also showed slightly improved drug release with a lower burst and increased slope. We showed that salt additives can be an effective way to modulate the pH in the ISFI environment, which can improve protein stability and ultimately improve the capacity of ISFIs for delivering pH-sensitive biomolecules. Such a platform represents a low-cost method of improving overall patient compliance and reducing the overall healthcare burden.

The industrial design, translation, and development strategies for long-acting peptide delivery

INTRODUCTION

Peptides are widely recognized as therapeutic agents in the treatment of a wide range of diseases, such as cancer, diabetes etc. However, their use has been limited by their short half-life, due to significant metabolism by exo- and endo-peptidases as well as their inherent poor physical and chemical stability. Research with the aim of improving their half-life in the body, and thus improving patient compliance (by decreasing the frequency of injections) has gained significant attention.

AREAS COVERED

This review outlines the current landscape and industrial approaches to achieve extended peptide exposure and reduce dosing frequency. Emphasis is placed on identifying challenges in drug product manufacturing and desirable critical quality attributes that are essential for activity and safety, providing insights into chemistry and design aspects impacting peptide release, and summarizing important considerations for CMC developability assessments of sustained release peptide drugs.

EXPERT OPINION

Bring the patient and disease perspective early into development. Substantial advances have been made in the field of sustained delivery of peptides despite their complexity. The article will also highlight considerations for early-stage product design and development, providing an industrial perspective on risk mitigation in developing sustained release peptide drug products.

Polymer-based thermoresponsive hydrogels for controlled drug delivery

INTRODUCTION

controlled drug delivery through hydrogels is generally limited by the poor barrier that polymeric network can create to diffusion mechanism. Stimuli responsive polymers can help in this way guaranteeing that delivery can be sustained and finely controlled using an external stimulus.

AREA COVERED

this review provides an overview of recent studies about the use of temperature as an external stimulus able to work as an efficient new route of drug's administration. Thermoresponsive hydrogels are discussed and compared in terms of physical properties and mechanism of drug release considering their classification in intrinsically (formed by thermosensitive polymers) and non-intrinsically (polymers with thermosensitive moieties) hydrogels.

EXPERT OPINION

thermoresponsive hydrogels can be developed by using different polymers added or not with micro/nanoparticles of organic or inorganic origin. In both cases the final system represents an innovative way for the local and sustained drug delivery in a specific site of the body. In particular, it is possible to obtain an on-demand release of drug by applying a local increase of temperature to the system.

Strychnos Potatorum L. Seed Polysaccharide-Based Stimuli-Responsive Hydrogels and Their Silver Nanocomposites for the Controlled Release of Chemotherapeutics and Antimicrobial Applications

Natural Strychnos potatorum L. (SPL) polysaccharide-based dual-responsive semi-IPN-type (SPL-DMA) hydrogels have been fabricated using dimethylaminoethyl methacrylate by simple free radical polymerization. Furthermore, a facial and eco-friendly method has been developed for the green synthesis of silver nanoparticles on SPL-DMA hydrogel templates (SPL-DMA-Ag) using an aqueous leaf extract of Carissa spinarum (as a bioreducing agent). SPL-DMA and SPL-DMA-Ag were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and evaluated network parameters. 5-Fluorouracil and doxorubicin were successfully encapsulated, and in vitro drug release studies were performed at pH values of 1.2 and 7.4 and at 25 and 37 °C. To understand the drug release mechanism of SPL-DMA hydrogels, various kinetic parameters were calculated. Biocompatibility and anticancer activities of SPL-DMA hydrogels were proved by an antioxidant activity study and in vitro cell viability studies against HeLa and 3T3-L1 cell lines. SPL-DMA-Ag hydrogels were used for antibacterial application.

Drug release from in situ forming implants and advances in release testing

In situ forming implants, defined as liquid formulations that generate solid or semisolid depots following administration, have shown a range of advantages in drug delivery. This drug delivery strategy allows localized delivery, sustained drug release over periods of days to months, and is a less invasive option compared to traditional solid implants which typically require surgical implantation. Unfortunately, there are a number of quality control challenges in terms of drug release testing of these delivery systems which is likely to have contributed to the relatively few commercially available in situ forming implant products. This article reviews current marketed in situ forming implant products, FDA guidance on in vitro release testing, and formulation and environmental parameters influencing drug release from in situ forming implants. Formulation considerations for development of biological agents loaded in situ forming implants are also discussed. The advantages and limitations of typically used in vitro release testing methods are summarized. Difficulties in the development of in vitro-in vivo correlations (IVIVCs) for in situ forming implant are discussed. The knowledge presented will be helpful for the development of in situ forming implants, as well as for the development of appropriate in vitro testing methods and IVIVCs.

In-situforming drug-delivery systems for periodontal treatment: current knowledge and perspectives

Several chemical compounds are considered to be promising as adjuvants in the treatment of periodontitis. Antimicrobials, anti-inflammatory drugs or, more recently, pro-regenerative or antioxidant molecules have shown a very interesting potential to improve the outcomes of mechanical biofilm removal and promote the healing of the damaged tissues. However, their clinical effect is often limited by the challenge of achieving effective and prolonged drug delivery within the periodontal lesion, while limiting the risk of toxicity.In-situforming implants (ISFI) are 'implantable' drug-delivery systems that have gained considerable attention over the last few decades due to their multiple biomedical applications. They are liquids that, when injected at the site to be treated, form a semi-solid or solid dosage form that provides safe and locally controlled drug release. This review discusses current data and future prospects for the use of ISFI in periodontal treatment.

Novel injectable progesterone-loaded nanoparticles embedded in SAIB-PLGA in situ depot system for sustained drug release

Poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) have attracted considerable interest in the medical community as a sustained-release drug delivery system for localized treatment. However, it is currently a grand challenge to simultaneously achieve low-dose drugs, stable and prolonged drug release, and long-term retention circumventing uptake by macrophages. Here, we construct a solvent-exchange in-situ depot system by incorporating progesterone (PRG) loaded PLGA NPs into a sucrose acetate isobutyrate (SAIB) and PLGA matrix for the long term treatment of Assisted Reproductive Technology (ART). The results showed that different solvent and PLGA contents could affect the drug release rate of PRG NPs-SAIB-PLGA in-situ depot system (PSPIDS). When DMSO was used as solvent with the addition of 8% PLGA to the depot, PSPIDS could achieve a constant drug release with no burst for 2 weeks in vitro. After a single intramuscular injection, such PSPIDS showed higher drug concentration and AUC (6773.0 ± 348.8 μg/L·h) over the entire 7-day testing period compared with the commercial multiple-day-dosing intramuscular PRG-oil solution (1914.5 ± 180.7 μg/L·h) in vivo. Importantly, PSPIDS could be administered at a dose of 3.65 mg/kg, which was one fourth of dose required for PRG-oil solution. The results demonstrate that PRG NPs could successfully achieve both reduced administered dosage and burst release, and therefore that PSPIDS is a promising long-acting composite system for hydrophobic drugs.

A review of existing strategies for designing long-acting parenteral formulations: Focus on underlying mechanisms, and future perspectives

The need for long-term treatments of chronic diseases has motivated the widespread development of long-acting parenteral formulations (LAPFs) with the aim of improving drug pharmacokinetics and therapeutic efficacy. LAPFs have been proven to extend the half-life of therapeutics, as well as to improve patient adherence; consequently, this enhances the outcome of therapy positively. Over past decades, considerable progress has been made in designing effective LAPFs in both preclinical and clinical settings. Here we review the latest advances of LAPFs in preclinical and clinical stages, focusing on the strategies and underlying mechanisms for achieving long acting. Existing strategies are classified into manipulation of in vivo clearance and manipulation of drug release from delivery systems, respectively. And the current challenges and prospects of each strategy are discussed. In addition, we also briefly discuss the design principles of LAPFs and provide future perspectives of the rational design of more effective LAPFs for their further clinical translation.

Multipurpose Prevention Technologies: Oral, Parenteral, and Vaginal Dosage Forms for Prevention of HIV/STIs and Unplanned Pregnancy

There is a high global prevalence of HIV, sexually transmitted infections (STIs), and unplanned pregnancies. Current preventative daily oral dosing regimens can be ineffective due to low patient adherence. Sustained release delivery systems in conjunction with multipurpose prevention technologies (MPTs) can reduce high rates of HIV/STIs and unplanned pregnancies in an all-in-one efficacious, acceptable, and easily accessible technology to allow for prolonged release of antivirals and contraceptives. The concept and development of MPTs have greatly progressed over the past decade and demonstrate efficacious technologies that are user-accepted with potentially high adherence. This review gives a comprehensive overview of the latest oral, parenteral, and vaginally delivered MPTs in development as well as drug delivery formulations with the potential to advance as an MPT, and implementation studies regarding MPT user acceptability and adherence. Furthermore, there is a focus on MPT intravaginal rings emphasizing injection molding and hot-melt extrusion manufacturing limitations and emerging fabrication advancements. Lastly, formulation development considerations and limitations are discussed, such as nonhormonal contraceptive considerations, challenges with achieving a stable coformulation of multiple drugs, achieving sustained and controlled drug release, limiting drug-drug interactions, and advancing past preclinical development stages. Despite the challenges in the MPT landscape, these technologies demonstrate the potential to bridge gaps in preventative sexual and reproductive health care.

An overview of PLGA in-situ forming implants based on solvent exchange technique: effect of formulation components and characterization

As a result of the low oral bioavailability of several drugs, there is a renewed interest for parenteral administration to target their absorption directly into the blood bypassing the long gastrointestinal route and hepatic metabolism. In order to address the potential side effects of frequent injections, sustained release systems are the most popular approaches for achieving controlled long-acting drug delivery. Injectable in-situ forming implants (ISFIs) have gained greater popularity in comparison to other sustained systems. Their significant positive aspects are attributed to easier production, acceptable administration route, reduced dosing frequency and patient compliance achievement. ISFI systems, comprising biodegradable polymers such as poly (lactide-co-glycolide) (PLGA) based on solvent exchange mechanisms, are emerged as liquid formulations that develop solid or semisolid depots after injection and deliver drugs over extended periods. The drug release from ISFI systems is generally characterized by an initial burst during the matrix solidification, followed by diffusion processes and finally polymeric degradation and erosion. The choice of suitable solvent with satisfactory viscosity, miscibility and biocompatibility along with considerable PLGA hydrophobicity and molecular weights is fundamental for optimizing the drug release. This overview gives a particular emphasis on evaluations and the wide ranges of requirements needed to achieve reasonable physicochemical characteristics of ISFIs.

Biodistribution of fluorescence-labelled EGF protein from slow release NanoZolid depots in mouse

AIM

The study was designed to evaluate the ability of the calcium sulfate based NanoZolid® drug delivery technology to locally release the epidermal growth factor (EGF) protein while maintaining its biological activity.

METHODS

NanoZolid-formulated EGF protein labelled with a near infrared dye (EGF-NIR) depots or EGF-NIR dissolved in PBS were injected subcutaneously into mice bearing EGF receptor (EGFR) positive human A549 lung cancer tumors inoculated subcutaneously. The release and biodistribution of the EGF-NIR were investigated in vivo longitudinally up to 96 h post administration, utilizing whole body fluorescence imaging. In order to confirm the in vivo findings, histological analysis of tumor cryosections was performed to investigate EGF-NIR fluorescent signal and EGFR expression level by immunofluorescence labelling.

RESULTS

The in vivo fluorescence imaging showed a controlled release profile of the EGF-NIR loaded in the NanoZolid depots compared to free EGF-NIR. Histological analysis of the tumors further demonstrated a prevailing distribution of EGF-NIR in regions with high levels of EGFR expression.

CONCLUSION

Calcium sulfate based depots can be used to formulate EGF while maintaining its biological activity, e.g. receptor binding capability. This may have a good clinical potential for local delivery of biomolecules to enhance treatment efficacy and minimize systemic adverse effects.

An injectable hydrogel using an immunomodulating gelator for amplified tumor immunotherapy by blocking the arginase pathway

Arginase 1 (ARG1) inactivates T cells by degrading L-arginine, severely reducing the immunotherapeutic efficacy. Effectively blocking the ARG1 pathway remains a challenge. L-norvaline is a very cheap and negligible side effects inhibitor of ARG1. However, its blockage efficacy for ARG1 is impeded by its high half-maximal-inhibitory concentration (IC50) requiring high drug loading content of L-norvaline in carriers. Moreover its high water solubility results in bursting and uncontrolled release. Herein we reported an injectable hydrogel strategy via an L-norvaline-based immunomodulating gelator that could effectively block ARG1 pathway. The designed gelator was a diblock copolymer containing L-norvaline-based polypeptide block, which could construct a thermally responsive injectable hydrogel by its self-gelation in tumor microenvironments. The hydrogel not only ensures high drug loading of L-norvaline, but also ensures controlled release of L-norvaline through responsive peptide bond cleavage, thereby solving the problems encountered by L-norvaline. The injectable hydrogel in combination with doxorubicin hydrochloride demonstrated a potent immunotherapy for removal of primary tumors, suppression of abscopal tumors and inhibition of pulmonary metastasis by combining the blockage of ARG1 pathway and the immunogenic cell death. Our immunomodulating gelator strategy provides a robust injectable hydrogel platform to efficiently reverse ARG1 immunosuppressive environments for amplified immunotherapy. STATEMENT OF SIGNIFICANCE: We designed an injectable hydrogel via an L-norvaline-based immunomodulating gelator. The designed gelator, a diblock copolymer containing an L-norvaline-based polypeptide block, enabled a thermally responsive injectable hydrogel by its self-gelation in tumor microenvironments. The injectable hydrogel not only guarantees high drug loading of L-norvaline, but also ensures controlled release of L-norvaline through responsive peptide bonds cleavage, thereby solving the problems encountered by L-norvaline. By further introducing doxorubicin hydrochloride in the hydrogel for inducing immunogenic cell death, the hydrogel showed remarkable immunotherapeutic efficacy towards ablation of primary tumors, suppression of abscopal tumors and inhibition of pulmonary metastasis. Our immunomodulating gelator strategy provides a new concept to efficiently reverse Arginase 1 immunosuppressive environments for amplified immunotherapy.

Review of Contemporary Self-Assembled Systems for the Controlled Delivery of Therapeutics in Medicine

The novel and unique design of self-assembled micro and nanostructures can be tailored and controlled through the deep understanding of the self-assembly behavior of amphiphilic molecules. The most commonly known amphiphilic molecules are surfactants, phospholipids, and block copolymers. These molecules present a dual attraction in aqueous solutions that lead to the formation of structures like micelles, hydrogels, and liposomes. These structures can respond to external stimuli and can be further modified making them ideal for specific, targeted medical needs and localized drug delivery treatments. Biodegradability, biocompatibility, drug protection, drug bioavailability, and improved patient compliance are among the most important benefits of these self-assembled structures for drug delivery purposes. Furthermore, there are numerous FDA-approved biomaterials with self-assembling properties that can help shorten the approval pathway of efficient platforms, allowing them to reach the therapeutic market faster. This review focuses on providing a thorough description of the current use of self-assembled micelles, hydrogels, and vesicles (polymersomes/liposomes) for the extended and controlled release of therapeutics, with relevant medical applications. FDA-approved polymers, as well as clinically and commercially available nanoplatforms, are described throughout the paper.

Vaccine implants: current status and recent advancements

Implants have long been used in the field of drug delivery as controlled release vehicles and are now being investigated as single-shot vaccine technologies. Implants have shown great promise, minimizing the need for multiple immunizations while stimulating potent immune responses with reduced doses of vaccine. Synchronous release of vaccine components from implants over an appropriate period of time is important in order to avoid issues including immune tolerance, sequestration or deletion. Traditionally, implants require surgical implantation and removal, which can be a barrier to their widespread use. Degradable and in situ implants are now being developed that can be administered using minimally invasive subcutaneous or intramuscular injection techniques. Injectable hydrogels remain the most commonly studied approach for sustained vaccine delivery due to their ease of administration and tunable degradation properties. Despite exciting advancements in the field of vaccine implants, few technologies have progressed to clinical trials. To increase the likelihood of clinical translation of vaccine implants, strategic testing of disease-relevant antigens in appropriate species is essential. In this review, the significance of vaccine implants and the different types of implants being developed to deliver vaccines are discussed.

Clinically established biodegradable long acting injectables: An industry perspective

Long acting injectable formulations have been developed to sustain the action of drugs in the body over desired periods of time. These delivery platforms have been utilized for both systemic and local drug delivery applications. This review gives an overview of long acting injectable systems that are currently in clinical use. These products are categorized in three different groups: biodegradable polymeric systems, including microparticles and implants; micro and nanocrystal suspensions and oil-based formulations. Furthermore, the applications of these drug delivery platforms for the management of various chronic diseases are summarized. Finally, this review addresses industrial challenges regarding the development of long acting injectable formulations.

Advancements in the co-formulation of biologic therapeutics

Biologic therapeutics are the medicines of the future and are destined to transform the approaches by which the causes and symptoms of diseases are cured and alleviated. These approaches will be accelerated through the development of novel strategies that target multiple pharmacologically active sites using a combination of different biologics, or mixtures of biologics and small molecule therapeutics. However, for this potential to be realised, advancements in co-formulation strategies for biologic therapeutics must be established. This review describes the current and emerging developments within this field and highlights the challenges and potential solutions, that will pave-the-way towards their clinical translation.

Injectable thermo-responsive nano-hydrogel loading triptolide for the anti-breast cancer enhancement via localized treatment based on "two strikes" effects

The clinical application of triptolide (TPL) in tumor therapy has been greatly limited by its toxicity and inefficient delivery. Herein, a localized and sustained-release thermo-sensitive hydrogel was developed for the intra-tumor administration of TPL. Based on the amphiphilic structure of poly (N-isopropylacrylamide-co-acrylic acid)-g-F68 copolymer, it was able to form nano-micelles to efficiently encapsulate TPL, and then turn into a hydrogel at 37 °C. TPL@nano-gel exhibited a sustained drug release profile in vitro and a stronger anticancer effect caused by "two strikes". The "first strike" was its enhanced cytotoxicity compared to free TPL, due to the enhanced pro-apoptosis effect observed in both MDA-MB-231 and MCF-7 cells caused by the regulation of endogenous mitochondrial pathways. Furthermore, TPL@nano-gel exhibited a "second-strike" through its anti-angiogenesis capabilities mediated through VEGFR-2 signaling inhibition. As expected, after intra-tumoral injection at a 0.45 mg/kg TPL-equivalent dose three times over 14 days in 4T1 tumor-bearing mice, TPL@nano-gel led to lower systemic toxicity and higher antitumor efficacy compared to multiple injections of TPL. In this regard, these findings indicate that this injectable thermo-responsive hydrogel carries great potential for TPL as a safe and effective cancer therapy.

Silica particles incorporated into PLGA-based in situ-forming implants exploit the dual advantage of sustained release and particulate delivery

Poly (lactic-co-glycolic acid) (PLGA) in situ-forming implants are well-established drug delivery systems for controlled drug release over weeks up to months. To prevent initial burst release, which is still a major issue associated with PLGA-based implants, drugs attached to particulate carriers have been encapsulated. Unfortunately, former studies only investigated the resulting release of the soluble drugs and hence missed the potential offered by particulate drug release. In this study, we developed a system capable of releasing functional drug-carrying particles over a prolonged time. First, we evaluated the feasibility of our approach by encapsulating silica particles of different sizes (500 nm and 1 μm) and surface properties (OH or NH₂ groups) into in situ-forming PLGA implants. In this way, we achieved sustained release of particles over periods ranging from 30 to 70 days. OH-carrying particles were released much more quickly when compared to NH₂-modified particles. We demonstrated that the underlying release mechanisms involve size-dependent diffusion and polymer-particle interactions. Second, particles that carried covalently-attached ovalbumin (OVA) on their surfaces were incorporated into the implant. We demonstrated that OVA was released in association with the particles as functional entities over a period of 30 days. The released particle-drug conjugates maintained their colloidal stability and were efficiently taken up by antigen presenting cells. This system consisting of particles incorporated into PLGA-based in situ-forming implants offers the dual advantage of sustained and particulate release of drugs as a functional unit and has potential for future use in many applications, particularly in single-dose vaccines.

An injectable thermosensitive hydrogel self-supported by nanoparticles of PEGylated amino-modified PCL for enhanced local tumor chemotherapy

We synthesized amino-modified poly(ε-caprolactone) PCN-b-PEG-b-PCN (PECN) triblock copolymers and studied the contribution of the introduced amino groups to the drug delivery efficiency of PECN nanoparticles (NPs) and their injectable thermosensitive hydrogels. PECN15 with an optimal amino group content was obtained. Firstly, the hydrophobic drug paclitaxel (PTX) was loaded into PECN15 up to 5.91% and formed PTX/PECN NPs 90 nm in size and with a slightly positive charge (7.3 mV). Furthermore, the injectable PTX/PECN NPs aqueous solution (25 wt%) at ambient temperature could undergo fast gelation at 37 °C and sustainedly release PTX/PECN NPs in 10 days. More importantly, compared with our previously reported PECT NPs, the PECN NPs without an increase in toxicity could improve the cell uptake and enhance intracellular drug release by responding to the acidic environment of the endosome. Thus, the PTX/PECN NPs presented a lower IC50 of 3.14 μg mL-1 than that of the PTX/PECT NPs (7.67 μg mL-1) and free PTX (4.65 μg mL-1). Moreover, through peritumoral injection, the PTX/PECNGel showed 94.27% inhibition rate of tumor growth on day 19, higher than PTX/PECTGel (72.28%) and Taxol® (47.03%). Therefore, the PECN NPs hydrogel provided a more effective injectable platform to enhance local cancer chemotherapy, and also provided the possibility of further functionalization by the reactive amino groups.

Chitosan hydrogels for sustained drug delivery

Sustainable and controlled delivery of drugs is at the centre of a huge amount of undertaken researches. The ability of hydrogels, high water content materials, to achieve a local and delayed-delivery has already been demonstrated for a wide variety of therapeutic agents and various polymer natures. In particular, chitosan, a natural polymer, stands out as a first choice material for hydrogels elaboration in biomedical, cosmetic, and health related applications, owing to its interesting properties (as biocompatibility, biodegradability, antimicrobial capacity, and mucoadhesivity). Moreover, chitosan also allows drugs to go easier through biological barriers. The main objective of this review is to report the various uses of chitosan hydrogels as drug delivery devices to control and/or delay the release of drugs loaded into their three dimensional matrix. A wide spectrum of corresponding biomedical applications of these systems can be encountered in the literature, whatever the physicochemical nature of drugs (hydrophilic, hydrophobic, macromolecular), as detailed in this review.

Comparison of the short-term results of single-dose intra-articular peptide with hyaluronic acid and platelet-rich plasma injections in knee osteoarthritis: a randomized study

Introduction/objectives

Intra-articular injections may be useful in terms of pain and functional status, in knee osteoarthritis (OA). Besides hyaluronic acid (HA) and platelet-rich plasma (PRP), peptide molecules recently begin to be used. The aim of this study was to compare the efficacy of intra-articular peptide Prostrolane® (CAREGEN Co. Ltd.) injection with that of the HA and PRP in the persons with OA.

Method

Fifty-four patients with OA were included in this prospective, randomized study. Patients were randomized into three groups as intra-articular HA, peptide, and PRP groups. Paracetamol was permitted three times a day to all groups. All the patients were evaluated by the Western Ontario and McMaster Universities Arthritis Index (WOMAC), Health Assessment Questionnaire (HAQ), and visual analogue scale (VAS) at rest and during movements. Measurements performed at the baseline, after the first week of injection, and at the first and third months of follow-up.

Results

Mean age was 55.8 ± 8.9 years. Forty-four (81.6%) were women. A week after the injections, rest and movement pain severity was measured by VAS decreased significantly in all the study groups (p < 0.05). There were no statistically significant differences between the groups in terms of first week pain relief (p > 0.05). WOMAC pain, stiffness, function, and total scores were improved significantly in all the groups a week after the injections (p < 0.05). Improvement continued at the third month control; however, the improvement in the WOMAC pain score was significantly better in the peptide group at the third month control (p < 0.05). The decrease in the rest and movement pain was continued for 3 months except the HA group’s rest pain. There were no differences among the groups for all measurements, except for the WOMAC pain score at 3 months after treatment, which was significantly lower in the peptide group.

Conclusion

As a result, pain relief and functional improvement were obtained after the intra-articular HA, peptide, and PRP injections in OA, and decrease in pain was better in the peptide group.

Key Points • The short-term effects of intra-articular HA, peptide, and PRP injections were compared in knee osteoarthritis. • HA, peptide, and PRP injections may be useful in pain relief and functional improvement in knee osteoarthritis.

Release rate determination from in situ gel forming PLGA implant: a novel 'shape-controlled basket in tube' method

OBJECTIVES

This study aimed to examine the impact of syringe-needle assembly differences in making implants of different shapes as well as its influence on the release kinetics and investigate the release kinetics of the in situ forming implant under various release arrangements.

METHODS

PLGA in situ forming implant was prepared in different shape and then subjected to in vitro release testing. Mathematical modelling was used to investigate drug release mechanisms.

KEY FINDINGS

The in situ forming implant was investigated for the first time how implant shapes can affect release results. It was demonstrated that implant shape differences could lead to significant variation in the release data. Here, we addressed this issue by developing a shape-controlled method to provide a consistent surface to volume ratio and, therefore, a reliable release result. Injectability in the in vitro release was discussed for the first time. Comparisons between various release methods were also evaluated. The release arrangement was found to be of great importance in release kinetics.

CONCLUSIONS

The developed 'shape-controlled basket in tube' method can provide the most reproducible release profiles by minimizing implant adhesion to the release vessels or movement without sacrificing full contact between the release medium and the implant surface.

Ultra-long-acting tunable biodegradable and removable controlled release implants for drug delivery

Here we report an ultra-long-acting tunable, biodegradable, and removable polymer-based delivery system that offers sustained drug delivery for up to one year for HIV treatment or prophylaxis. This robust formulation offers the ability to integrate multiple drugs in a single injection, which is particularly important to address the potential for drug resistance with monotherapy. Six antiretroviral drugs were selected based on their solubility in N-methyl-2-pyrrolidone and relevance as a combination therapy for HIV treatment or prevention. All drugs released with concentrations above their protein-adjusted inhibitory concentration and retained their physical and chemical properties within the formulation and upon release. The versatility of this formulation to integrate multiple drugs and provide sustained plasma concentrations from several weeks to up to one year, combined with its ability to be removed to terminate the treatment if necessary, makes it attractive as a drug delivery platform technology for a wide range of applications.