Poster S14 - Controlled release of fucoidan-based BRAF-targeted nanoparticles prevents MAPK/ERK paradoxical activation

Saturday, October 26, 2024

10:00 AM - 11:00 AM EST

Location: Exhibit Hall E, F & G

Primary Investigator(s)

Daniel Heller, PhD (he/him/his)

Head, Cancer Nanomedicine Laboratory
Memorial Sloan Kettering Cancer Center
New York, New York, United States

Co-Author(s)

CC

Chen Chen

Postdoctoral Fellow
Genentech, Inc., United States

Presenting Author(s)

Ana Marie Perea (she/her/hers)

Research Technician at The Heller Lab
Memorial Sloan Kettering Cancer Center
New York, New York, United States

Introduction: Mutations in the MAPK/ERK signaling pathway are present in multiple advanced solid tumors, including melanoma, non-small cell lung cancer, and anaplastic thyroid cancer. While 1st and 2nd generation BRAF inhibitors (BRAFi) can effectively target the ATP-binding site of BRAF V600 mutants, drug resistance can arise due to paradoxical activation of MAPK/ERK signaling. To address the shortage of potential BRAFi that target both monomeric and dimeric BRAF alterations and ultimately overcome drug resistance, plixorafenib (also known as FORE8394 or PLX8394) was developed to inhibit monomeric, mutated BRAF and to prevent subsequent dimerization. In its phase 1/2a clinical trial, plixorafenib demonstrated pharmacological potential for treating cancers harboring BRAF alterations. Daily doses of >=900 mg administered alone or with cobicistat, a CYP3A inhibitor/pharmacokinetic booster, achieves targeted exposures and demonstrates clinical efficacy. Methods to enhance therapeutic exposure systemically and more importantly in the tumor tissue may improve the therapeutic window.
We developed a nanoparticle delivery system to encapsulate plixorafenib and target it to tumors using fucoidan, a natural polysaccharide, which binds activated tumor vasculature. In this work, we found that fucoidan encapsulation of plixorafenib markedly enhances its pharmacodynamics and pharmacokinetics without administering cobicistat, in part due to delayed release from late endosomes/lysosomes, and overall extends survival of BRAF-mutant tumor-bearing mice.

Materials and

Methods: We synthesized plixorafenib nanoparticles via nanoprecipitation with fucoidan and an indocyanine dye. Drug encapsulation efficiency was quantified by high performance liquid chromatography. Nanoparticle imaging was performed using scanning electron microscopy, cryogenic electron microscopy, and atomic force microscopy. We used A375 tumor cells as a model for BRAFV600E melanoma in a mixture with Matrigel for injection into athymic nude mice. When tumor volumes reached 150 mm3, mice were randomized and intraperitoneally injected with one of the following four conditions: 1) plixorafenib free drug (100 mg/kg); 2) plixorafenib nanoparticles (100 mg/kg); 3) Cobicistat (25 mg/kg); or 4) plixorafenib free drug and cobicistat (100 mg/kg and 25 mg/kg respectively). Mice were treated 3 times a week, and the tumor volume and mouse weight were monitored 4 times a week until the designated endpoint.

Results, Conclusions, and Discussions: We investigated the delivery of plixorafenib via fucoidan-based nanocarriers. The nanoparticles achieve a drug mass loading of 83% and an encapsulation efficiency of 60% (Fig 1. a). The nanoparticles extended BRAF inhibition and subsequent ERK phosphorylation in A375 cells compared to the free drug (Fig 1. b) due to endolysosomal sequestration. In vivo studies performed in a A375 xenograft model showed that nanoparticles administered intraperitoneally improved the pharmacokinetics of plixorafenib compared to the free drug in healthy mice (Fig 1. c). We observed a similar pharmacokinetic profile between the nanoparticles and free drug/cobicistat co-treatment, suggesting that the nanoparticles increased blood circulation time to a similar degree as co-administration of the drug with cobicistat. These combined advantages of nanoparticles, enhanced anti-tumor efficacy and prolonged survival, even compared to the combination of plixorafenib with cobicistat (Fig 1. d).

Acknowledgements (Optional):