Potent, collagenase-selective MMP inhibitor (Ki values are 3.0, 3.4, 4.4, 59, 154 and 527 nM for MMP-1, MMP-13, MMP-8, MMP-9, MMP-2 and MMP-3 respectively). Inhibits cartilage breakdown in vitro and in vivo and displays antiarthritic activity. Orally active.