Soluplus®-Based Pharmaceutical Formulations: Recent Advances in Drug Delivery and Biomedical Applications

Abstract

Poor water solubility remains a significant challenge in the pharmaceutical industry that limits the therapeutic efficacy and bioavailability of many active pharmaceuticals. Soluplus^® (SLP), an amphiphilic graft copolymer made of polyethylene glycol, polyvinyl caprolactam, and polyvinyl acetate, has been gaining interest in recent years as it addresses these limitations by acting as a versatile carrier. Its ability to form stable amorphous dispersions and enhance drug solubility, as well as its physicochemical properties, support its role as a key excipient in advanced drug delivery systems. Recent investigations have demonstrated the adaptability of SLP in addressing drug delivery requirements, offering controlled release, improved targeting, and superior therapeutic outcomes. This review examines some key formulation methods that make use of SLP, including hot-melt extrusion, spray drying, electrospinning, drug–polymer layering, and capsule and tablet formulations, highlighting the capacity of SLP to overcome formulation challenges. Biomedical applications of SLP have also been explored, with a focus on its role in improving the delivery of antitumoral, anti-inflammatory, antimicrobial, and antiparasitic drugs.

Introduction

Some orally administered drugs remain unabsorbed, limiting their therapeutic options and their clinical efficacy [1,2]. It has been observed that a set of medicines designed to treat chronic conditions or to manage severe illnesses fail to achieve their full potential because a great number of them exhibit poor solubility in water, which is a critical factor for their effective absorption [3]. As a result, only a small fraction of the administered dose of active principle reaches the systemic circulation and, therefore, the target site. These challenges are widespread, affecting a wide category of pharmaceutical compounds, particularly class-II and class-IV drugs, according to the Biopharmaceutics Classification System (BCS).

Poor water solubility has more implications than just inefficacy, as it can also lead to different therapeutic and side effects. BCS class-II drugs have high permeability and can easily cross biological membranes and consequently, their absorptions largely depend on their dissolution rates in the gastrointestinal fluids. A well-known example is ibuprofen, widely used as a painkiller and anti-inflammatory, which, despite its high permeability, often demonstrates variable absorption levels because of its limited solubility [4,5]. Similarly, when dealing with class-IV drugs that display both poor solubility and permeability, additional challenges are faced in order to achieve therapeutic effectiveness, such as complex matrices or the incompatibility of formulating high-dose drugs [6]. The combination of these factors highlights the need for innovative approaches to improve the pharmacokinetic profiles of these drugs, ensuring their efficient absorption that can permit exerting the intended therapeutic effects.

Different strategies to target key factors in drug formulation and delivery have been developed in order to enhance their solubility and absorption, thereby improving their bioavailability [7]. Examples include the production of formulations in which a drug is dispersed in a solid matrix, as well as lipid-based formulations, capable of enhancing the solubility of lipophilic drugs by the formation of oil-in-water emulsions upon contact with gastrointestinal fluids. The use of nanosuspensions is another approach that is attracting attention lately, in which a drug is dispersed in a colloidal nanoscale system, significantly increasing its surface area and, consequently, its dissolution rate [8,9].

In recent years, polymer-based drug delivery systems have gained ground because of their ability to modulate the release profile of drugs in a more controlled and sustained manner. This is particularly beneficial for drugs that require precise dosages to avoid adverse effects. Polymers classified as “generally recognized as safe” (GRAS), such as polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), low molecular weight chitosan, and certain amphiphilic block copolymers, are commonly employed because of their biocompatibility and capacity to interact with a wide range of drugs [10,11]. For example, PVP has been effectively used via solid dispersion techniques to improve the dissolution rate of itraconazole, an antifungal agent, resulting in better therapeutic outcomes [10]. Similarly, López-Rios de Castro et al. (2024) concluded that PEG-PLGA polymeric nanoparticles were able to solubilize therapeutic peptides [12]. Likewise, poloxamers (better known by their trade name, Pluronic®, from BASF, Tarragona, Spain), a family of triblock copolymers constituted of polyethylene oxide (PEO) and polypropylene oxide (PPO) blocks, have been widely utilized to enhance the solubility of drugs such as paclitaxel, an anti-cancer agent with very limited water solubility [10].

Poloxamines (Tetronic®, also from BASF, Tarragona, Spain) are another family of amphiphiles, formed by four arms of PEO and PPO blocks connected by an ethylene diamine spacer, which confers pH-sensitivity to the polymer, as an advantage over their linear counterparts, Pluronic®. They have been used recently in the form of micelles and gels [13,14] and in combination with polymeric nanofibers [15] for the delivery of miltefosine, an antiparasitic drug used for the treatment of leishmaniasis.

Among amphiphilic block copolymers, Soluplus® (SLP, hereafter), an amphiphilic water-soluble graft copolymer developed by BASF, stands out as particularly effective in addressing the solubility challenges posed by poorly water-soluble drugs as well as a matrix polymer for solid solutions [16]. Until now, most articles dealing with SLP have focused on the features and applications of this copolymer in drug delivery, highlighting its advantages, drug incorporation methods, and the physicochemical characteristics of SLP-based formulations. In this review, we have focused on the biomedical applications of this polymer. This review is structured to explore the physicochemical properties of SLP, followed by a discussion of potential formulation methods, and concludes with some of its relevant biomedical applications.

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Following excipients are mentioned in the study besides other: Soluplus^® (SLP), TPGS, poloxamer F127, poloxamer F108, Cremophor® RH 40, poloxamer 188, Kollidon® VA30, Kollidon® VA64, poloxamer 407, Tween 80, vitamin E, Eudragit®, ethyl cellulose, chitosan, Solutol® HS15

Guembe-Michel, N.; Nguewa, P.; González-Gaitano, G. Soluplus^®-Based Pharmaceutical Formulations: Recent Advances in Drug Delivery and Biomedical Applications. Int. J. Mol. Sci. 2025, 26, 1499. https://doi.org/10.3390/ijms26041499

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