[Meso-1,2-bis(2,6-dihalo-3/4-hydroxyphenyl)ethylenediamine]platinum(II) complexes (meso-1-PtLL': 2,6-F-2,3-OH; meso-2-PtLL': 2,6-F-2,4-OH; meso-3-PtLL': 2,6-Cl-2,3-OH; meso-4-PtLL': 2,6-Cl-2,4-OH; L = OH2, L' = OSO3 or L,L' = Cl-2) were designed with the aim to get drugs comprising both cytotoxic and testosterone level lowering potencies. It is assumed that such compounds are more efficient than the established endocrine therapeutic measures and can affect the development of hormone refractory prostate cancer (PC). With exception of meso-3-PtLL' all Pt-complexes and the comparison compound cisplatin significantly reduced the testosterone level in experiments on male rats. However, in the test on the Dunning R3327 PC of the rat only cisplatin and meso-4-PtLL' showed a significant anti-tumor activity at well-tolerated dose ranges. Meso-4-PtLL' also significantly extended the time to disease progression in comparison with orchiectomy in this tumor model. Interestingly, the relapsed tumor, too, responded to meso-4-PtLL' as demonstrated in a long-term study on orchiectomized rats bearing Dunning R3327 PC grafts. This effect cannot be ascribed to cytotoxic effects of meso-4-PtLL' because of its inactivity on the human LNCaP/FGC PC cell line. Therefore, the contribution of an additional mechanism to the anti-prostate cancer activity of meso-4-PtLL', presumably owing to its estrogenic potency, must be considered. This assumption was supported by test results with diethylstilbestrol (DES) (non-steroidal estrogen) on the Dunning R3327 PC of the rat relapsed after orchiectomy. This tumor model was strongly inhibited by DES. The possible mode of action of meso-4-PtLL' is thoroughly discussed.

The marked activity of [meso-1, 2-bis(2, 6-difluoro-3-hydroxyphenyl)ethylenediamine]platinum(II) (meso-3-PtLL', L, L' = Cl(2) or L = OH(2), L' = OSO(3)) on the hormone-sensitive MXT-M-3, 2 breast cancer implanted in mice is most probably due to a mechanism based on the reduction of the endogenous estrogen level. Cytotoxic effects which are poorly pronounced in experiments on several breast cancer cell lines (e.g. MCF-7), do not significantly contribute to the anti-breast cancer activity of this compound. In contrast to this, the standard cisplatin and the structurally related comparison compound [meso-1, 2-bis(4-fluorophenyl)ethylenediamine]platinum(II) (meso-4-PtLL', L, L' = Cl(2) or L = OH(2), L' = OSO(3)) are strongly active in vivo as well as in vitro. Both effects entail programmed cell death, which is responsible for the inhibition of the tumor growth. The minor cytotoxicity of meso-3-PtLL' in breast cancer cell cultures is caused neither by an inappropriate rate of reaction with bionucleophiles (e.g. by a too fast inactivation by plasma proteins) nor solely by the observed poor absorption by the tumor cells resulting in an insufficient drug concentration at the DNA. Additionally, an impeded reaction with biologically important, guanine-rich sequences of DNA (owing to the 2, 6-standing F atoms which hinder the drug-target inter action) must be assumed as cause of its marginal cytotoxicity.

Aqua[meso‐1, 2‐bis(2, 6‐difluoro‐3‐hydroxyphenyl)ethylenediamine]sulfatoplatinum(II) (meso‐3‐PtSO 4 ) and its racemate (rac‐3‐PtSO 4 ) are highly active on the hormone‐sensitive MXT‐M‐3, 2 breast cancer of the mouse. In vitro , on the MXT + cell culture derived from this tumor, however, they are inactive (meso‐3‐PtSO 4 ) or moderately active (rac‐3‐PtSO 4 ) in concentrations corresponding to levels of these drugs in animal experiments. The in vivo effect is mainly caused by a reduction of the endogenous estrogen level in the host animals due to an interference with the ovarian steroid biosynthesis as demonstrated for meso‐3‐PtSO 4 . Therefore, a reversal of the breast cancer inhibiting effect of meso‐3‐PtSO 4 can be achieved by simultaneous estrone administration. Histological results on ovaries, uterus, and tumor of meso‐3‐PtSO 4 ‐treated mice also favor such a mode of action. However, especially for rac‐3‐PtSO 4 cytotoxic effects contributing to the anti‐breast cancer activity cannot be excluded. Considerations on the mode of action of Pt‐complexes which inhibit breast cancer by interference with estrogen receptor mediated processes of growth control and with DNA replication are presented.

Aiming at the development of new drugs for the treatment of prostate cancer, the effects of steroidal compounds and one non-steroidal substance on androgen biosynthesis were evaluated in vitro and in vivo. Sa 40 [17-(5-pyrimidyl)androsta-5,16-diene-3beta-ol], its 3-acetyl derivate Sa 41 and BW 19 [3,4-dihydro-2-(4-imidazolylmethyl)-6-methoxy-1-methyl-naphthalene] are compounds from our group, which have been developed as inhibitors of CYP 17 (17alpha-hydroxylase-C17, 20-lyase, the key enzyme in androgen biosynthesis). They have been compared with CB 7598 [abiraterone: 17-(3-pyridyl)androsta-5,16-diene-3beta-ol], its 3-acetyl compound CB 7630 and ketoconazole, compounds which already have been used clinically. The most potent compound toward human CYP 17 (testicular microsomes) was Sa 40 (IC(50) value of 24 nM), followed by Sa 41, CB 7598, BW 19, CB 7630 and ketoconazole. Sa 40 shows a type II difference spectrum and a non-competitive type of inhibition (K(i) value of 16 nM). No recovery of enzyme activity was observed after preincubation of CYP 17 with Sa 40 and subsequent charcoal treatment. In Escherichia coli cells coexpressing human CYP 17 and NADPH-P450 reductase, Sa 40 was more active than CB 7598 and BW 19, whereas the acetyl compounds were not active. The latter three compounds were equally active towards rat CYP 17. Male Sprague-Dawley (SD) rats were administered daily for 14 days BW 19 and the acetyl derivatives Sa 41 and CB 7630 as prodrugs (0.1 mmol/kg intraperitoneally). The test compounds strongly reduced plasma testosterone concentration, as well as prostate and seminal vesicles weights. They showed moderate inhibitory effects on the weights of levator ani, bulbocavernosus and testes, whereas they led to an increase in adrenal and pituitary weights. The only exception was BW 19 which did not change pituitary weights. Based on its superiority on the human enzyme, it was concluded that Sa 40 in its 3beta-acetate form (Sa 41) could be a promising candidate for clinical evaluation.

[meso-1,2-Bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine]platinum(II) complexes (meso-1-PtLĹ; L,Ĺ= Cl or L = H2O and Ĺ = OSO3) are highly effective towards hormone-sensitive, rodent breast cancers due to their significant estrogenic potencies. Their antitumor activities are caused by modification of the immune response. The pharmacophor of these compounds, the 1,2-bis(2,6-dichloro-4-hydroxyphenyl) ethane (23H), was used as the lead structure in a structure-activity study with the goal of finding new biological response modifiers for the therapy of breast cancer. As intermediates for the synthesis of the 23H derivatives, the CH3O-substituted stilbenes 12E/12Z— 16E/16Z were prepared by reaction of the related benzyltriphenylphosphonium halides with 2,6-dichloro-4-methoxybenzaldehyde by the method of Wittig/Campbell and Donald, respectively. Separation of the E/Z-mixtures was performed by fractional crystallization and/or column chromatography. The E-1,2-bis(2,6-dichloro-4-methoxyphenyl)ethene (17E) was obtained by reductive coupling of 2,6-dichloro-4-methoxybenzaldehyde with TiCl4/Zn according to the method of Mukaiyama. Illumination of the solution of 17E in benzene with UV light resulted in an E/Z-isomerization. Compound 17Z could be isolated from this mixture. The CH3O-substituted stilbenes were transformed into their 1,2-diphenylethanes (12H—17H) by catalytic hydrogenation of the C1=C2 double bond. Ether cleavage of the compounds was performed with BBr3. In the estrogen receptor binding assay all OH-substituted 1,2-diphenylethanes showed affinity to the estrogen receptor, which was about two orders of magnitude lower than that of 17 β-estradiol. In the uterus weight test on the immature mouse 1,2-diphenylethanes with 4-substituted OH groups proved to be “true” estrogens (19H: 2-F/4-OH; 20H: 2-Cl/4-OH; 23H: 2,6-Cl2/4-OH), while those with a 3-substituted OH group in the 2-phenyl ring showed the properties of a “partial” estrogen (18H: 3-OH) or of an “impeded” estrogen (21H: 2-Cl/3-OH; 22H: 2-Cl/5-OH). The latter also showed significant additional antiestrogenic activity. The related E-stilbenes mostly exhibit similar hormonal activities. As a rule, the replacement of the OH groups by the CH3O groups and the change from the E- to the Z-configuration led to a reduction of the estrogenic potencies. Several of the 1-(2,6-dichloro-4-methoxyphenyl)-2-phenylethenes (12E: 3-OCH3; 12Z: 3-OCH3; 15E: 2-Cl/3-OCH3; 15Z: 2-Cl/3-OCH3; 16E: 2-Cl/5-OCH3) produced antiestrogenic effects in the uterus weight test. It is supposed that those new 1-(2,6-dichloro-4-hydroxyphenyl)-2-phenylethanes endowed with marked estrogenic properties are also active as biological response modifiers in animals bearing hormone-sensitive breast cancer. The antiestrogenic derivatives presumably inhibit the breast cancer development by competing with tumor growth stimulating endogenous estrogens for the binding to the receptor. This is to be confirmed in a further study.

The new neuropeptide Y (NPY) Y-5 receptor antagonist CGP 71683A displayed high affinity for the cloned rat NPY Y-5 subtype, but > 1,000-fold lower affinity for the cloned rat NPY Y-1, Y-2, and Y-4 subtypes, In LMTK cells transfected with the human NPY Y-5 receptor, CGP 71683A was without intrinsic activity and antagonized NPY-induced Ca2+ transients. CGP 71683A was given intraperitoneally (dose range 1-100 mg/kg) to a series of animal models of high hypothalamic NPY levels. In lean satiated rats CGP 71683A significantly antagonized the increase in food intake induced by intracerebroventricular injection of NPY. In 24-h fasted and streptozotocin diabetic rats CGP 71683A dose-dependently inhibited food intake. During the dark phase, CGP 71683A dose-dependently inhibited food intake in free-feeding lean rats without affecting the normal pattern of food intake or inducing taste aversion. In free-feeding lean rats, intraperitoneal administration of CGP 71683A for 28 d inhibited food intake dose-dependently with a maximum reduction observed on days 3 and 4, Despite the return of food intake to control levels, body weight and the peripheral fat mass remained significantly reduced. The data demonstrate that the NPY Y-5 receptor subtype plays a role in NPY-induced food intake, but also suggest that, with chronic blockade, counterregulatory mechanisms are induced to restore appetite.

NEUROPEPTIDE Y (NPY) is a powerful stimulant of food intake and is proposed to activate a hypothalamic 'feeding' receptor distinct from previously cloned Y-type receptors(1). This receptor was first suggested to explain a feeding response to NPY and related peptides, including NPY2-36, that differed from their activities at the Y1 receptor(2), Here we report the expression cloning of a novel Y-type receptor from rat hypothalamus, which we name Y5, The complementary DNA encodes a 456-amino-acid protein with less than 35% overall identity to known Y-type receptors, The messenger RNA is found primarily in the central nervous system, including the paraventricular nucleus of the hypothalamus. The extent to which selected peptides can Inhibit adenylate cyclase through the Y5 receptor and stimulate food intake in rats correspond well, Our data support the idea that the Y5 receptor is the postulated 'feeding' receptor, and may provide a new method for the study and treatment of obesity and eating disorders.