Leveraging Open Science Drug Development for PET: Preliminary Neuroimaging of (11)C-Labeled ALK2 Inhibitors

[Image: see text] Mutations in the gene encoding activin receptor-like kinase 2 (ALK2) are implicated in the pathophysiology of a pediatric brainstem cancer, diffuse intrinsic pontine glioma (DIPG). Inhibitors of ALK2 that cross the blood–brain barrier have been proposed as a method of treatment for DIPG. As part of an open science approach to radiopharmaceutical and drug discovery, we developed (11)C-labeled radiotracers from potent and selective lead ALK2 inhibitors to investigate their brain permeability through positron emission tomography (PET) neuroimaging. Four radiotracers were synthesized by (11)C-methylation and assessed by dynamic PET imaging in healthy Sprague–Dawley rats. One of the compounds, [(11)C]M4K2127, showed high initial brain uptake (SUV ∼ 2), including in the region of interest (pons). This data supports the use of this chemotype as a brain penetrant ALK2 inhibitor that permeates evenly into the pons with potential application for the treatment of DIPG.