A biphenyl matrix metalloproteinase (MMP) inhibitor (MMPI) with potential antineoplastic activity. Tanomastat inhibits MMP-2, MMP-3, and MMP-9, inhibiting extracellular matrix degradation and potentially inhibiting angiogenesis, tumor growth and invasion, and metastasis. MMPs consist of at least 18 zinc-containing endo-proteinases that are capable of degrading collagen and proteoglycan.