Structure-based design of novel class II c-Met inhibitors: 1. Identification of pyrazolone-based derivatives.

Deregulation of c-Met receptor tyrosine kinase activity leads to tumorigenesis and metastasis in animal models. More importantly, the identification of activating mutations in c-Met, as well as MET gene amplification in human cancers, points to c-Met as an important target for cancer therapy. We have previously described two classes of c-Met kinase inhibitors (class I and class II) that differ in their binding modes and selectivity profiles. The class II inhibitors tend to have activities on multiple kinases. Knowledge of the binding mode of these molecules in the c-Met protein led to the design and evaluation of several new class II c-Met inhibitors that utilize various 5-membered cyclic carboxamides to conformationally restrain key pharmacophoric groups within the molecule. These investigations resulted in the identification of a potent and novel class of pyrazolone c-Met inhibitors with good in vivo activity.

Design, synthesis, and biological evaluation of potent c-Met inhibitors.

c-Met is a receptor tyrosine kinase that plays a key role in several cellular processes but has also been found to be overexpressed and mutated in different human cancers. Consequently, targeting this enzyme has become an area of intense research in drug discovery. Our studies began with the design and synthesis of novel pyrimidone 7, which was found to be a potent c-Met inhibitor. Subsequent SAR studies identified 22 as a more potent analog, whereas an X-ray crystal structure of 7 bound to c-Met revealed an unexpected binding conformation. This latter finding led to the development of a new series that featured compounds that were more potent both in vitro and in vivo than 22 and also exhibited different binding conformations to c-Met. Novel c-Met inhibitors have been designed, developed, and found to be potent in vitro and in vivo.

Determination of the importance of the stereochemistry of psorospermin in topoisomerase II-induced alkylation of DNA and in vitro and in vivo biological activity.

Psorospermin is a natural product that has been shown to have activity against drug-resistant leukemia lines and AIDS-related lymphoma. It has also been shown to alkylate DNA through an epoxide-mediated electrophilic attack, and this alkylation is greatly enhanced at specific sites by topoisomerase II. In this article, we describe the synthesis of the two diastereomers of O5-methyl psorospermin and their in vitro activity against a range of solid and hematopoietic tumors. The diastereomeric pair (+/-)-(2'R,3'R) having the naturally occurring enantiomer (2'R,3'R) is the most active across all the cell lines and shows approximately equal activity in both drug-sensitive and drug-resistant cell lines. In subsequent studies using all four enantiomers of O5-methyl psorospermin, the order of biological potency is (2'R,3'R) > (2'R,3'S) = (2'S,3'R) > (2'S,3'S). This order of potency is also found in the topoisomerase II-induced alkylation of O5-methyl psorospermin and can be rationalized by molecular modeling of the psorospermin-duplex binding complex. Therefore, this study defines the optimum stereochemical requirements for both the topoisomerase II-induced alkylation of DNA and the biological activity by psorospermin and its O5-methyl derivatives. Finally, (2'R,3'R) psorospermin was found to be as effective as gemcitabine in slowing tumor growth in vivo in a MiaPaCa pancreatic cancer model. In addition, (2'R,3'R) psorospermin in combination with gemcitabine was found to show an at least additive effect in slowing tumor growth of MiaPaCa.