Comparative studies on the cytotoxicity and antileukemic activity of limited numbers of Amaryllidaceae alkaloids with pretazettine, a narcissus alkaloid, have been performed on the systems of Rauscher virus-carrier cells and the leukemic mice. Only precriwelline, a stereochemical epimer of pretazettine, has been found to be therapeutically active as that of pretazettine. The natural precursors such as haemanthamine, crinamine and 6-hydroxycrinamine were also moderately active, but the artifical final product, tazettine, was confirmed to be inert. The structure-activity relationship of pretazettine or precriwelline has been partially analyzed. Also, the predominancy of antiviral activity relative to cytotoxicity of the alkaloids has been demonstrated when compared with some standard antileukemic drugs.

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A series of 6-benzoxazinylpyridazin-3-ones was prepared and evaluated for inhibition of cardiac phosphodiesterase (PDE) fraction III in vitro and for positive inotropic activity in vivo. 6-[3,4-Dihydro-3-oxo-1,4(2H)-benzoxazin-7-yl]-2,3,4,5-tetrahydro-5 - methylpyridazin-3-one (bemoradan) was found to be an extremely potent and selective inhibitor of canine PDE fraction III and a long-acting, potent, orally active inotropic vasodilator agent in various canine models. Additional benzoxazin-6-yl and -8-yl compounds were also prepared. Altering the pyridazinone substitution from the 6-position to the 7-position produced a 14-fold increase in the iv cardiotonic potency (ED50) from 77 to 5.4 micrograms/kg while substitution at the 8-position reduced potency. Methyl substitution at various sites in the molecule was also examined. Positive inotropic activity was maintained for between 8 and 24 h after a single oral dose (100 micrograms/kg) of bemoradan in dogs, thus making it one of the most potent and long-acting orally effective inotropes yet described. Bemoradan is currently under development as a cardiotonic agent for use in the management of congestive heart failure.

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A series of benzoxazinones has been synthesized and tested for PPARgamma agonist activity. Synthetic approaches were developed to provide either racemic or chiral compounds. In vitro functional potency could be measured through induction of the aP2 gene, a target of PPARgamma. These studies revealed that compounds with large aliphatic chains at the nitrogen of the benzoxazinone were the most potent. Substitution of the chain was tolerated and in many cases enhanced the in vitro potency of the compound. Select compounds were further tested for metabolic stability, oral bioavailability in rats, and efficacy in db/db mice after 11 days of dosing. In vivo analysis with 13 and 57 demonstrated that the series has potential for the treatment of type 2 diabetes.

A novel series of nonsteroidal heterocycles was discovered which display cell-type selective, high-affinity (nanomolar) binding to the progesterone receptors from TE85 osteosarcoma cells but > 1 microM binding affinity to the progesterone receptors from T47D and ZR75 human breast carcinoma cells. Structure-activity relationships were developed for a set of these compounds, and a representative analog 1-(3,4-dichlorobenzoyl)-3-phenyl-1,4,5,6-tetrahydropyridazine++ + (1i, RWJ 25333) was chosen for further evaluation. RWJ 25333 stimulated the in vitro proliferation of human osteoblast-like cells but not human breast cells.