The erbB-2 oncogene encodes a transmembrane protein tyrosine kinase which plays a pivotal role in signal transduction and has been implicated when overexpressed in breast, ovarian, and gastric cancers. Naturally occurring benzoquinoid ansamycin antibiotics herbimycin A, geldanamycin (GDM), and dihydrogeldanamycin were found to potently deplete p185, the erbB-2 oncoprotein, in human breast cancer SKBR-3 cells in culture. Chemistry efforts to modify selectively the quinoid moiety of GDM afforded derivatives with greater potency in vitro and in vivo. Analogs demonstrated inhibition of p185 phosphotyrosine in cell culture and in vivo after systemic drug administration to nu/nu nude mice bearing Fisher rat embryo cells transfected with human erbB-2 (FRE/erbB-2). Specifically, dosed intraperitoneally at 100 mg/kg, 17-(allylamino)-17-demethoxygeldanamycin and other 17-amino analogs were effective at reducing p185 phosphotyrosine in subcutaneous flank FRE/erbB-2 tumors. Modifications to the 17-19-positions of the quinone ring revealed a broad structure-activity relationship in vitro.

Overexpression of the erbB-2 oncogene has been linked to poor prognosis in breast, ovarian, and gastric cancers. Naturally occurring benzoquinoid ansamycin antibiotics herbimycin A, geldanamycin (GDM), and dihydrogeldanamycin were found to potently deplete p185, the erbB-2 oncoprotein, in human breast cancer SKBR-3 cells in culture. Chemistry efforts to modify selectively the ansa ring of GDM afforded derivatives with greater potency in vitro and in vivo. Analogs demonstrated inhibition of p185 phosphotyrosine in cell culture and in vivo after systemic drug administration to nu/nu nude mice bearing Fisher rat embryo cells transfected with human erbB-2. Functional group modification in the ansa ring was performed stereoselectively and regiospecifically without the need for protection strategies. Essential functional groups that were required for anti-erbB-2 activity were the 7-carbamate and the 2,3-double bond. Modification of the functional groups at the other positions was permitted. Structure-activity relationships are described for 1-5-, 7-9-, 11-, 15-, and 22-substituted geldanamycins.

These findings suggest that GA and its derivatives are cytostatic/cytotoxic at concentrations that also downregulate Raf-1, p185erbB2 and mutant p53, and raise the possibility that depletion of these proteins and the antiproliferative activities of GA have a common mechanism.

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Sorbitol formation from glucose, catalyzed by the enzyme aldose reductase, is believed to play a role in the development of certain chronic complications of diabetes mellitus. Spiro hydantoins derived from five- and six-membered ketones fused to an aromatic ring or ring system inhibit aldose reductase isolated from calf lens. In vivo these compounds are potent inhibitors of sorbitol formation in sciatic nerves of streptozotocinized rats. Optimum in vivo activity is reached in spiro hydantoins derived from 6-halogenated 2,3-dihydro-4H-1-benzopyran-4-ones (4-chromanones). In 2,4-dihydro-6-fluorospiro[4H-1-benzopyran-4,4'-imidazolidine]-2',5 '-dione, the activity resides exclusively in the 4S isomer, compound 115 (CP-45,634, USAN: sorbinil). This compound is currently being used to test, in humans, the value of aldose reductase inhibitors in the therapy of diabetic complications.