Preclinical activity of homoharringtonine against melanoma leptomeningeal disease using patient-derived tumor cells.

2024 Background: Leptomeningeal disease arising from melanoma (M-LMD) is a rare and highly aggressive form of metastasis associated with limited therapeutic options and poor clinical outcomes. Progress in treatment development has been hindered by the lack of clinically relevant models, particularly patient-derived circulating tumor cells obtained from cerebrospinal fluid (PD-CSF-CTCs). To overcome this limitation, we established protocols for CSF and tissue collection from patients with M-LMD, enabling successful ex vivo propagation of PD-CSF-CTCs and the generation of patient-derived xenograft models. These platforms facilitated integrated proteomic and transcriptomic analyses to identify M-LMD–specific pathways, thereby supporting the discovery of targeted therapeutic strategies. Methods: PD-CSF-CTCs were propagated from samples obtained from the CSF of patients with M-LMD. A library of 1,436 FDA-approved small molecules was screened using a high-throughput 384-well assay to identify agents that suppressed tumor cell proliferation. Lead compounds were subsequently assessed in vivo through intrathecal administration in xenograft models. Results: Twenty compounds (~1.4%) demonstrated complete cytotoxicity in both PD-CSF-CTCs and murine melanoma cell lines. The most potent agents included ponatinib (EC₅₀: 1.85–4.06×10⁻⁶), sorafenib (9.57–9.77×10⁻⁶), ceritinib (1.84–2.05×10⁻⁶), and homoharringtonine (HHT; 3.63–4.11×10⁻⁸). HHT, a plant-derived semisynthetic cephalotaxine ester, was prioritized for in vivo evaluation based on its robust cytotoxic activity and capacity to penetrate both the blood–brain and blood–CSF barriers. In a randomized murine M-LMD model, daily intrathecal administration of HHT (24.0 μg) was well tolerated, significantly prolonged survival (P < 0.001, Mantel–Cox test), and achieved complete responses in 27% of treated mice, while preserving body weight and motor function. Conclusions: This study introduces a robust preclinical platform for identifying effective treatments for M-LMD. Our findings highlight the promise of repurposing FDA-approved HHT as a therapeutic option. Future work will focus on refining HHT’s activity against M-LMD and elucidating HHT’s molecular mechanisms.