Abstract A061: The LSD1 inhibitor iadademstat shows preclinical efficacy in malignant peripheral nerve sheath tumor cells and synergistic effects in combination
Authors: Sacilotto Natalia , Mascaró Cristina , Creus Edgar , Fernández Juana , Lázaro Conxi , Limón Ana , Soliva Robert , Xaus Jordi 
Published: December 2023

Abstract
Background: Malignant peripheral nerve sheath tumors (MPNSTs) are highly aggressive and rare malignancies accounting for 10% of all tissue sarcomas. Around 50% develop in patients with neurofibromatosis type 1 carrying mutations in the NF1 gene and the other 50% occur sporadically. NF1 is a tumor suppressor gene and a negative regulator of RAS signaling pathway. However, mutation of the NF1 gene is not sufficient to drive MPNST and a series of further mutational events must accumulate in genes other than NF1, such as in CDKN2A and PRC2 complex components. Mutations in p53 or PTEN and/or mutations or copy number variations in oncogenes, such as EGFR or c-Met can also be detected in MPNST. Herein we explore the effects of LSD1 inhibition with iadademstat as a single agent in a panel of MPNST cell lines, both NF1-related and sporadic, and in combination with inhibitors of the MEK-ERK and PI3K/AKT signaling pathways.
Materials and Methods: The cell viability in 12 MPNST cell lines, both commercial and derived from patients’ primary tumors, was assessed after 6 days of treatment with iadademstat as a single agent. Synergisms between iadademstat and the MEK inhibitor selumetinib or the PI3K inhibitor copanlisib were also evaluated after 6 days of treatment in three selected responsive cell lines and analyzed with Calcusyn and Combenefit software. Additionally, the effects of iadademstat in RAS pathways (pAKT and pERK levels) were also evaluated in these cell lines.
Results: Iadademstat displayed sub-nanomolar activity as a single agent in 8 out of 12 cell lines tested, both NF1-related and sporadic, with different degrees of viability reduction. This was further confirmed with two additional LSD1 inhibitors, with iadademstat being the most potent inhibitor tested. Highly-responsive cell lines showed a decrease in pAKT levels while medium- and low-responsive cell lines displayed no significant differences. pERK levels were not affected. Moreover, the combination of iadademstat and selumetinib or copanlisib displayed strong synergy in cell viability assays in both commercial and patient-derived iadademstat-sensitive cell lines.
Conclusions: The LSD1 inhibitor iadademstat is efficacious as single agent in nearly 70% of the MPNST cell lines tested, both NF1-related and sporadic and this efficacy increases synergistically in combination with selumetinib or copanlisib. Therefore, LSD1 inhibitors alone or in combination emerge as a potential treatment for MPNST, an indication with high unmet needs with no approved targeted therapies available.
Citation Format: Natalia Sacilotto, Cristina Mascaró, Edgar Creus, Juana Fernández, Conxi Lázaro, Ana Limón, Robert Soliva, Jordi Xaus. The LSD1 inhibitor iadademstat shows preclinical efficacy in malignant peripheral nerve sheath tumor cells and synergistic effects in combination [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A061.