Targeting metabolic dependencies in MYC-driven osteosarcoma through Lp-PLA2 inhibition

Osteosarcoma (OS) is the most prevalent pediatric bone cancer and treatment outcomes and survival rates have remained largely unchanged for decades. Patients with metastatic or relapsed/refractory disease face five-year survival rates below 30%, with no salvage therapies available after standard of care failure. Overexpression of the oncogene MYC contributes to aggressive tumor progression, therapeutic resistance, and metabolic reprogramming in OS, yet direct targeting of MYC remains challenging. Lipoprotein-associated phospholipase A2 (Lp-PLA2), an inflammatory enzyme, regulates phospholipid remodeling and inflammatory lipid signaling that may be exploited by MYC-high tumors. Targeting this pathway with the small-molecule Lp-PLA2 inhibitor Darapladib could reveal metabolic dependencies on phospholipid and fatty acid metabolism that supports growth and survival in MYC-driven OS. A 3D spheroid high-throughput drug screen of 2,036 FDA-approved and bioactive compounds was performed on a high-MYC patient-derived xenograft (PDX) OS cell line and a murine Myc knock-in OS cell line. Darapladib was identified as a candidate compound and IC₅₀ values were determined in both 2D and 3D models. High MYC-expressing PDX and murine OS cells were treated in 2D for 72 hours based on IC₅₀ values, followed by spheroid formation assays post-treatment. CellTiter-Glo viability was assessed after a 72-hour growth period. Migration capacity was examined via wound healing assays using the same treatment strategy. In vivo efficacy of Darapladib was evaluated in NSG mice using two high MYC-expressing PDX models. Darapladib exhibited IC₅₀ values below 5 μM in both PDX and murine OS lines, indicating sensitivity to Lp-PLA2 inhibition. Low-MYC expressing OS lines showed relatively higher IC₅₀ values compared to high-MYC lines. In 3D spheroids, Darapladib pre-treatment decreased cellular ATP levels and demonstrated significant spheroid size reduction. Darapladib-treated cells exhibited impaired migration in wound healing assays. In vivo studies revealed decreased average primary tumor volume in both high-MYC PDX models. Darapladib demonstrates in vitro and in vivo efficacy in high-MYC OS models, establishing Lp-PLA2 as a novel therapeutic target that potentially exploits MYC-dependent metabolic vulnerabilities. The selective sensitivity of high-MYC expressing lines to Darapladib suggests that MYC status may serve as a predictive biomarker. As Darapladib has an established safety profile from previous cardiovascular clinical trials, these findings support its clinical translation for high-risk OS patients lacking effective therapies. Further studies are warranted to elucidate mechanisms by which Lp-PLA2 inhibition disrupts MYC-driven lipid metabolism and evaluate Darapladib in combination with other targeted therapies.