Rational Design of Polyglutamic Acid Delivering an Optimized Combination of Drugs Targeting Mutated BRAF and MEK in Melanoma

Abstract

Targeted therapies against cancer can relieve symptoms and induce remission; however, they often present limited duration of disease control, cause side effects, and may induce acquired resistance. Therefore, there is great motivation to develop a unique delivery system, targeted to the tumor, in which several active entities can be combined, the therapeutic index can be increased by reducing systemic exposure, and their synergistic activity can be enhanced. To meet these goals, the biocompatible and biodegradable poly(α,l‐glutamic acid) (PGA) is chosen as a nanocarrier that facilitates extravasation‐dependent tumor targeting delivery. The RAS/RAF/MEK/ERK pathway when aberrantly activated in melanoma, can lead to uncontrolled cell proliferation, induced invasion, and reduced apoptosis. Here, two drugs targeting this pathway are selected: a MEK1/2 inhibitor (selumetinib, SLM) and a modified BRAF inhibitor (modified dabrafenib, mDBF) that exhibit synergism in vitro. The combination of PGA conjugated to SLM and mDBF (PGA–SLM–mDBF) is synthesized and characterized. PGA–SLM–mDBF inhibits the proliferation of melanoma cells and decreases their migratory and sprouting abilities without inducing a hemolytic effect. Moreover, it exhibits superior antitumor activity in a mouse model of primary melanoma and prolonged survival at a lower dose than the free drugs.

Nanotechnology Addressing Cutaneous Melanoma: The Italian Landscape

“…Furthermore, Ret melanoma cells have the capability to form spontaneous brain metastasis [250], and this represents a valuable tool to evaluate the efficacy of the proposed therapies, as in most cases of primary lesions, surgery is resolutive. Another interesting cell line is the BRAF V600E mutated D4M.3A [251], which grows in C57BL/6 mice; this model can be exploited to evaluate targeted therapies [252], as well as immunotherapeutic agents. With the establishment of immunotherapy as the gold standard for melanoma treatment, xenografts of human melanoma cell lines in immunocompromised mice became a less attractive model of the disease, although they still offer valuable insights on the evaluation of nanomedicines targeting cancer cells [241][242][243] and of stimuli sensitive-based nanomedicines [244,245].…”

Hydrophilic Poly(glutamic acid)-Based Nanodrug Delivery System: Structural Influence and Antitumor Efficacy

“…γ-PGA is produced by several microorganisms of the Bacillus species [ 32 , 33 ], and α-PGA by chemical synthesis [ 34 , 35 , 36 ]. Due to their excellent hydrophilicity, biosafety, and biodegradability, a lot of PGA-based composites are employed for building nanoscale delivery systems [ 37 , 38 ], including hydrogels [ 39 ], nanofibers [ 40 ], monoliths [ 30 ], polymersomes [ 41 ], and NPs [ 42 ]. For these PGA-based nanoscale delivery systems, doxorubicin (DOX) is commonly selected as the model drug, as it can form stable aggregates via ionic interactions [ 43 , 44 , 45 ].…”

Polyglutamate-based nanoconjugates for image-guided surgery and post-operative melanoma metastases prevention

“…The benefits of macromolecules, particularly polymers exploited as vehicles for the delivery of low molecular weight (Mw) drugs and diagnostic agents were broadly described in terms of improved drugs solubility 42 , simultaneous delivery of synergistic therapeutic combinations 43 - 45 , or a large payload of a drug and/or imaging agent 46 to the tumor site. These led to enhancement of the fluorescence signal in comparison with low Mw fluorescent entities 47 , 48 and altered the pharmacokinetics/pharmacodynamics (PK/PD) of drugs which present a narrow therapeutic window, hence increasing their maximum-tolerated dose (MTD) and decreasing their adverse effects thus improving their safety profile 49 .…”

“…These led to enhancement of the fluorescence signal in comparison with low Mw fluorescent entities 47 , 48 and altered the pharmacokinetics/pharmacodynamics (PK/PD) of drugs which present a narrow therapeutic window, hence increasing their maximum-tolerated dose (MTD) and decreasing their adverse effects thus improving their safety profile 49 . We have recently reported the rational design and synthesis of a biocompatible and biodegradable poly(α,L-glutamic acid) (PGA) delivering an optimized combination of drugs targeting mutated BRAF and MEK in melanoma 43 . The enhanced antitumor effect was demonstrated in primary melanoma-bearing mice treated with SLM and modified DBF (mDBF) conjugated to PGA (PGA-SLM-mDBF) compared to those treated with the combination of the unconjugated drugs or combination of the mono-drug conjugates 43 .…”

“…We have recently reported the rational design and synthesis of a biocompatible and biodegradable poly(α,L-glutamic acid) (PGA) delivering an optimized combination of drugs targeting mutated BRAF and MEK in melanoma 43 . The enhanced antitumor effect was demonstrated in primary melanoma-bearing mice treated with SLM and modified DBF (mDBF) conjugated to PGA (PGA-SLM-mDBF) compared to those treated with the combination of the unconjugated drugs or combination of the mono-drug conjugates 43 . This was probably attributed to the macromolecular carrier, PGA, that simultaneously delivered the drugs in a synergistic ratio to the tumor, exploiting the enhanced permeability and retention (EPR) effect 50 .…”