Soluplus–TPGS Mixed Micelles as a Delivery System for Brigatinib: Characterization and In Vitro Evaluation

Abstract

Lung cancer is a major public health concern, with a high incidence and fatality rate. Its treatment is very difficult, as it is mostly diagnosed in advanced stages. Non-small cell lung carcinoma (NSCLC) is the major form of lung carcinoma that persists. Brigatinib (BGT), a powerful small-molecule tyrosine kinase inhibitor, has demonstrated significant therapeutic potential in the treatment of NSCLC with anaplastic lymphoma kinase (ALK) mutations. However, the therapeutic applicability of BGT is hampered by its low solubility and bioavailability. In this study, we developed a mixed micelle system comprising Soluplus and TPGS loaded with BGT. BGT was encapsulated into the mixed micelles using various combinations of Soluplus and TPGS, with encapsulation efficiency (EE%) ranging from 52.43 ± 1.07 to 97.88 ± 2.25%. The dynamic light scattering data showed that the mixed micelles ranged in size from 75.7 ± 0.46 to 204.3 ± 5.40 nm. The selected mixed micelles (F6) showed approximately 38% BGT release in the first 2 h, and subsequently, within 72 h, the release was 94.50 ± 5.90%. The NMR experiment confirmed the formation of micelles. Additionally, the mixed micelles showed significantly higher cellular uptake (p < 0.05) and increased cytotoxicity (p < 0.05) as compared to the free BGT. Specifically, the obtained IC₅₀ values for BGT-loaded Soluplus–TPGS mixed micelles and free BGT were 22.59 ± 6.07 and 61.45 ± 6.35 μg/mL, respectively. The results of the in vitro stability experiment showed that the selected mixed micelle (F6) was stable at both room temperature and 4 °C, with only minor changes in size and PDI. Our results indicate great potential for the developed Soluplus–TPGS mixed micelles as a delivery system for BGT.

Introduction

Cancer is a condition characterized by an uncontrolled division of aberrant cells that can spread from one organ to another or different regions of the body. It starts with a genetic mutation of a single cell that allows it to divide and multiply uncontrollably. These mutations are either inherited or acquired. (1) The acquired mutation can be caused by environmental exposures such as ultraviolet rays or smoking. Out of the different types of cancer, lung cancer is a major public health concern, with a high incidence and fatality rate. It is the second most prevalent cancer worldwide. According to GLOBOCAN 2020 cancer incidences and mortality estimates, lung cancer has become the second most diagnosed (11.4%) cancer and the leading cause of cancer death (18%) worldwide. (2) The lung cancer is lethal because it initially shows no signs or symptoms and is only identified in its advanced stages. The incidence of lung cancer is higher among males compared to females. (3) It must be promptly diagnosed and staged (size of the tumor and its extent) for a better prognosis.

Lung cancer is classified into two major groups, non-small cell lung carcinoma (NSCLC) and small cell lung carcinoma (SCLC). NSCLC is the most common form of lung cancer. (4) Depending on the stage of NSCLC, the main treatment options include surgery, radio frequency ablation, radiation therapy, chemotherapy, targeted medication therapy, immunotherapy, and palliative procedures. With the advancement of molecular and diagnostic procedures, the researchers have gained insights into the etiology of NSCLC and identified their genomic biomarkers. These biomarkers include Kirsten rat sarcoma viral oncogene homologue (KRAS), epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), ROS proto oncogene 1 (ROS1), B-RAF proto oncogene (BRAF), RET proto oncogene (RET), MET proto oncogene (MET), human epidermal growth factor receptor 2 (HER2), and neurotrophic receptor tyrosine kinase (NTRK). (5) The knowledge of these biomarkers helped in the development of the drugs that precisely target these oncogenic mutations.

Brigatinib (BGT), a potent small-molecule tyrosine kinase inhibitor, has shown remarkable therapeutic potential in the treatment of NSCLC with ALK mutations. It received FDA approval in 2017 for the treatment of NSCLC. BGT is considered a breakthrough drug because it has successfully addressed the issue of drug resistance associated with the first-generation oral tyrosine kinase ALK inhibitor (Crizotinib) and second-generation tyrosine kinase ALK inhibitors (Ceritinib and Alectinib). It effectively inhibits both trans-membrane proteins, EGFR and ALK in humans. (6) The superior inhibitory effects of BGT against NSCLC with ALK mutations are primarily due to the specific affinity of its dimethyl phosphine oxide moiety to the ALK. (7) However, the clinical application of BGT is hindered by its poor solubility and limited bioavailability. (8) Specifically, the reported aqueous solubility of BGT is around 0.1 mg/mL. (9) Although the exact absolute bioavailability of BGT in humans remains unknown due to the lack of pharmacokinetic data following intravenous administration, it was estimated to be 46%, (10) which is within the range reported in rat and monkey (40–53%). (11) In addition to its low solubility, BGT is a substrate for the CYP3A enzyme, P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP). (10) These factors likely contribute to its low bioavailability due to the first-pass effect and intestinal efflux.

Nanotechnology has emerged as a promising field in medical research and treatment, offering innovative solutions for diagnosing, treating, and preventing various ailments. Liposomes, (12) solid lipid nanoparticles, (13) and polymeric nanoparticles (14) are some of the nanotechnology-based formulations that enhance the properties and effectiveness of pharmaceutical products. In order to address the challenges associated with BGT delivery, researchers have turned to nanotechnology-based drug delivery systems, including nanospanlastics, (15) solid lipid nanoparticles, (16) self-nanoemulsifying drug delivery systems, (17) and polymeric nanoparticles. (18) Polymeric micelles have attracted attention in drug delivery due to their biocompatibility, core–shell structure that protects active molecules in their core, low toxicity, stable morphology, and nanoscale size. Polymeric micelles can also address the solubility issue of hydrophobic drugs. (19) Recently, “mixed micelles” systems have been introduced to utilize the properties of two or more block copolymers to improve the qualities of the single micelle system. (20) These include improved kinetic and thermodynamic stability, more precise control over size, increased drug loading capacities, and easy surface modification. (21) The mixed micelle system may lower reticuloendothelial system uptake, as well as improve drug targeting by increasing permeability and retention. (22) Furthermore, mixed micelles have a size range of 20 to 200 nm, which is sufficient to avoid quick clearance from renal tubules yet small enough to permeate through capillaries in order to improve targeting and limit off-target toxicity. Thus, mixed micelles can minimize the negative effects of anticancer medications. (23)

Polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus) is a novel amphiphilic polymer that has been shown to improve the solubility of numerous hydrophobic medicines such as acyclovir, (24) scopoletin, (25) febendazole, (26) and cyclosporine A. (27) Soluplus has reportedly a very low critical micellar concentration (CMC) value of around 7.6 μg/mL and a high hydrophilic lipophilic balance (HLB) value of approximately 14. This combination provides high stability to the micelles against dilution. (28)

D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) is a biomaterial that has been commonly used for the preparation of mixed micelles. TPGS is an FDA-approved, synthetic and water-soluble derivative of vitamin E and composed of both hydrophilic (PEG chain) and hydrophobic (vitamin E) parts. (29) TPGS is mainly used as a surfactant, solubilizing agent, and permeation enhancer for hydrophobic drugs. (30) TPGS also acts as a P-gp inhibitor and helps in overcoming multi-drug resistance (MDR) in cancer treatments. (31)

In the current work, BGT was encapsulated in the mixed micellar system based on Soluplus and TPGS, in order to enhance its aqueous solubility and improve the in vitro antitumor activity. The physicochemical properties of the BGT-loaded mixed micelles, such as percentage drug loading (DL%), encapsulation efficiency (EE%), particle size, polydispersity (PDI), morphology, in vitro stability, and in vitro release profile, were investigated. Finally, in vitro cellular uptake and cytotoxicity in human lung cancer cell lines (A549) were also studied.

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Materials

Brigatinib (BGT) was purchased from Beijing Mesochem Technology Co. Ltd. (Beijing China). Soluplus was procured from BASF Pharma (New Jersey, USA). TPGS, DMSO-d6, D2O, ethanol, methanol, acetonitrile and coumarin-6 were purchased from Sigma-Aldrich (St. Louis, USA). Milli-Q water was prepared in-house using a Merck Milli-Q Millipore ultrapure water purification system. Dulbecco’s Modified Eagle Medium (DMEM) was purchased from Life Technologies Ltd. (Paisley, UK).

Raisuddin Ali, Wajhul Qamar, Mohd Abul Kalam, and Ziyad Binkhathlan, Soluplus–TPGS Mixed Micelles as a Delivery System for Brigatinib: Characterization and In Vitro Evaluation, ACS Omega Article ASAP, DOI: 10.1021/acsomega.4c06264

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