S1P/ceramides and cytokines as potential biomarkers of response following administration of bxq-350

e15007 Background: BXQ-350 was investigated in a Phase 1 dose-escalation safety study of all-comer cancer patients with advanced solid malignancies, including high grade gliomas ( NCT02859857 ) (safety/efficacy results reported in a separate abstract). The primary objective of this single agent study was to describe the safety profile and to determine the maximum tolerated dose. Multiple secondary parameters were included to characterize BXQ-350’s pharmacokinetic parameters, efficacy profile and elucidation of potential biomarkers. BXQ-350 is a nanovesicle of recombinantly expressed Saposin C (SapC) and dioleoylphosphatidylserine. In nature, SapC is a protein encoded by the Psap gene, and serves as an allosteric activator of several enzymes involved in sphingolipid/ceramide metabolism, enzymes which are being investigated as novel therapeutic targets in cancers. Indeed, sphingolipids are a class of bioactive signaling molecules implicated in multiple cellular processes and molecular pathways. Amongst these sphingolipids, Sphingosine-1-Phosphate (S1P) induces cancer cell survival and proliferation, activates multiple oncogenic pathways, and promotes a pro-tumoral microenvironment. SapC has broad anticancer activity, lowering S1P and increasing ceramides, also inducing an anti-tumoral immune response. Methods: Lipodomic analysis (sphingolipids) and cytokines were analyzed in plasma samples of a subset of patients enrolled in this study. Results: Analysis of plasma biomarker samples, collected throughout the period patients were on study, reveals notable changes of circulating sphingolipids and cytokines. A subset of patients exhibited clinical benefits following BXQ-350 administration (see other presentation for details; ̃17% of the evaluable patients remained on study up to Cycle 6; and 8 patients (̃11%) with PFS> 6 months). Concomitant circulating changes in S1P and other ceramides may be indicative of treatment effect. Also, concurrent changes in circulating levels of pro/antitumoral cytokines were noted. Conclusions: While these results are exploratory and preliminary in nature, these initial results warrant further investigation. These observations will be further explored in specific cancer and non-cancer indications. Clinical trial information: 02859857.