Matrix metalloproteases (MMP) are a family of enzymes that contribute to the degradation of the extracellular matrix. The destruction of the extracellular matrix eventually leads to tumour invasion, metastasis and angiogenesis. Realising this mechanism of action, there is tremendous potential for inhibitors of MMP in cancer therapy. Extensive preclinical data have shown that administration of matrix metalloprotease inhibitors (MMPI) to different animal models results in a reduction in primary tumour growth as well as in the number and size of metastatic lesions. Based on promising preclinical studies, synthetic MMPI have been developed and taken into clinical trials. These include marimastat, BAY-129566, CGS-27023A, prinomastat (AG-3340), EMS-275291 and metastat (COL-3). These drugs are all in different stages of clinical development, ranging from phase I to III. In general, musculoskeletal problems, such as joint stiffness and pain in hands, arms and shoulders seem to affect most patients in varying degrees, depending on the dose and type of compound administered. In addition to single agent therapy, several MMPI have entered trials of combination therapy. The objective of combining chemotherapy with an MMPI is to potentiate tumour cytotoxicity as well as to reduce the size and number of metastatic lesions. Several compounds have entered phase III combination therapy trials, but it is still too early to report any data. There is ongoing research in correlating biological endpoints, such as levels of MMP and markers of angiogenesis with clinical response. As the field of MMP and their inhibitors continues to mature, its role in cancer therapeutics will be better defined.
