Abstract
Myristoylation, the N-terminal addition of the fatty acid myristate to proteins, regulates membrane-bound signal transduction pathways important in cancer cell biology. This modification is catalyzed by two N-myristoyltransferases, NMT1 and NMT2. Zelenirstat is a first-in-class potent oral small molecule inhibitor of both NMT1 and NMT2 proteins. Patients with advanced solid tumors and relapsed/refractory (R/R) B-cell lymphomas were enrolled in an open label, phase I dose escalation trial of oral daily zelenirstat, administered in 28-day cycles until progression or unacceptable toxicity. The endpoints were to evaluate dose-limiting toxicities (DLT) to establish a maximum tolerated dose (MTD), pharmacokinetic parameters, and anticancer activity. Twenty-nine patients were enrolled (25 advanced solid tumor; 4 R/R B-cell lymphoma) and 24 were DLT-evaluable. Dosing ranged from 20mg once daily (OD) to 210mg OD without DLT, but gastrointestinal DLTS were seen in the 280mg cohort. MTD and recommended phase 2 dose were 210mg OD. Common adverse events were predominantly Gr ≤ 2 nausea, vomiting, diarrhea, and fatigue. Plasma concentrations peaked at 2h with terminal half-lives averaging 10h. Steady state was achieved by day 15, and higher doses achieved trough concentrations predicted to be therapeutic. Stable disease as best response was seen in eight (28%) patients. Progression-free survival and overall survival were significantly better in patients receiving 210mg OD compared to those receiving lower doses. Zelenirstat is well-tolerated, achieves plasma exposures expected for efficacy, and shows early signs of anticancer activity. Further clinical development of zelenirstat is warranted.
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