Hydroxamate-Based Selective Macrophage Elastase (MMP-12) Inhibitors and Radiotracers for Molecular Imaging

Macrophage elastase [matrix metalloproteinase (MMP)-12] is the most upregulated MMP in abdominal aortic aneurysm (AAA) and, hence, MMP-12-targeted imaging may predict AAA progression and rupture risk. Here, we report the design, synthesis, and evaluation of three novel hydroxamate-based selective MMP-12 inhibitors (CGA, CGA-1, and AGA) and the methodology to obtain MMP-12 selectivity from hydroxamate-based panMMP inhibitors. Also, we report two ^99mTc-radiotracers, ^99mTc-AGA-1 and ^99mTc-AGA-2, derived from AGA. ^99mTc-AGA-2 displayed faster blood clearance in mice and better radiochemical stability compared to ^99mTc-AGA-1. Based on this, ^99mTc-AGA-2 was chosen as the lead tracer and tested in murine AAA. ^99mTc-AGA-2 uptake detected by autoradiography was significantly higher in AAA compared to normal aortic regions. Specific binding of the tracer to MMP-12 was demonstrated through ex vivo competition. Accordingly, this study introduces a novel family of selective MMP-12 inhibitors and tracers, paving the way for further development of these agents as therapeutic and imaging agents.