The lonidamine derivative H2-gamendazole reduces cyst formation in polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a debilitating renal neoplastic disorder with limited treatment options. It is characterized by the formation of large fluid-filled cysts that develop from kidney tubules through abnormal cell proliferation and cyst-filling fluid secretion driven by cAMP-dependent Cl- secretion. We tested the effectiveness of the indazole carboxylic acid H2-gamendazole (H2-GMZ), a derivative of lonidamine, to inhibit these processes using in vitro and in vivo models of ADPKD. H2-GMZ was effective in rapidly blocking forskolin-induced, Cl--mediated short-circuit currents in human ADPKD cells, and it significantly inhibited both cAMP- and epidermal growth factor-induced proliferation of ADPKD cells. Western blot analysis of H2-GMZ-treated ADPKD cells showed decreased phosphorylated ERK and decreased hyperphosphorylated retinoblastoma levels. H2-GMZ treatment also decreased ErbB2, Akt, and cyclin-dependent kinase 4, consistent with inhibition of heat shock protein 90, and it decreased levels of the cystic fibrosis transmembrane conductance regulator Cl- channel protein. H2-GMZ-treated ADPKD cultures contained a higher proportion of smaller cells with fewer and smaller lamellipodia and decreased cytoplasmic actin staining, and they were unable to accomplish wound closure even at low H2-GMZ concentrations, consistent with an alteration in the actin cytoskeleton and decreased cell motility. Experiments using mouse metanephric organ cultures showed that H2-GMZ inhibited cAMP-stimulated cyst growth and enlargement. In vivo, H2-GMZ was effective in slowing postnatal cyst formation and kidney enlargement in the Pkd1flox/flox: Pkhd1-Cre mouse model. Thus, H2-GMZ treatment decreases Cl- secretion, cell proliferation, cell motility, and cyst growth. These properties, along with its reported low toxicity, suggest that H2-GMZ might be an attractive candidate for treatment of ADPKD.NEW & NOTEWORTHY Autosomal dominant polycystic kidney disease (ADPKD) is a renal neoplastic disorder characterized by the formation of large fluid-filled cysts that develop from kidney tubules through abnormal cell proliferation and cyst-filling fluid secretion driven by cAMP-dependent Cl- secretion. This study shows that the lonidamine derivative H2-GMZ inhibits Cl- secretion, cell proliferation, and cyst growth, suggesting that it might have therapeutic value for the treatment of ADPKD.

N-Butyldeoxygalactonojirimycin Induces Reversible Infertility in Male CD Rats.

This study shows for the first time that an iminosugar exerts anti-spermiogenic effect, inducing reversible infertility in a species that is not related to C57BL/6 male mice. In CD rats, N-butyldeoxygalactonojirimycin (NB-DGJ) caused reversible infertility at 150 mg/kg/day when administered daily as single oral dose. NB-DGJ inhibited CD rat-derived testicular ß-glucosidase 2 (GBA2) activity at 10 µM but did not inhibit CD rat-derived testicular ceramide-specific glucosyltransferase (CGT) at doses up to 1000 µM. Pharmacokinetic studies revealed that sufficient plasma levels of NB-DGJ (50 µM) were achieved to inhibit the enzyme. Fertility was blocked after 35 days of treatment and reversed one week after termination of treatment. The rapid return of fertility indicates that the major effect of NB-DGJ may be epididymal rather than testicular. Collectively, our in vitro and in vivo studies in rats suggest that iminosugars should continue to be pursued as potential lead compounds for development of oral, non-hormonal male contraceptives. The study also adds evidence that GBA2, and not CGT, is the major target for the contraceptive effect of iminosugars.

Discovery of a potential allosteric ligand binding site in CDK2.

Cyclin-dependent kinases (CDKs) are key regulatory enzymes in cell cycle progression and transcription. Aberrant activity of CDKs has been implicated in a number of medical conditions, and numerous small molecule CDK inhibitors have been reported as potential drug leads. However, these inhibitors exclusively bind to the ATP site, which is largely conserved among protein kinases, and clinical trials have not resulted in viable drug candidates, attributed in part to the lack of target selectivity. CDKs are unique among protein kinases, as their functionality strictly depends on association with their partner proteins, the cyclins. In an effort to identify potential target sites for disruption of the CDK-cyclin interaction, we probed the extrinsic fluorophore 8-anilino-1-naphthalene sulfonate (ANS) with human CDK2 and cyclin A using fluorescence spectroscopy and protein crystallography. ANS interacts with free CDK2 in a saturation-dependent manner with an apparent K(d) of 37 µM, and cyclin A displaced ANS from CDK2 with an EC(50) value of 0.6 µM. Co-crystal structures with ANS alone and in ternary complex with ATP site-directed inhibitors revealed two ANS molecules bound adjacent to one another, away from the ATP site, in a large pocket that extends from the DFG region above the C-helix. Binding of ANS is accompanied by substantial structural changes in CDK2, resulting in a C-helix conformation that is incompatible for cyclin A association. These findings indicate the potential of the ANS binding pocket as a new target site for allosteric inhibitors disrupting the interaction of CDKs and cyclins.

A novel potent indazole carboxylic acid derivative blocks spermatogenesis and is contraceptive in rats after a single oral dose.

Women have historically been the focus for development of new contraceptive methods. The National Institutes of Health, World Health Organization, and Institute of Medicine have stressed the need to develop nonhormonal, nonsteroidal male contraceptive agents. We report results from initial dose-ranging studies of a new indazole carboxylic acid analogue, gamendazole. An infertility rate of 100% was achieved in seven out of seven proven-fertile male rats 3 wk after a single oral dose of 6 mg/kg of gamendazole. Fertility returned by 9 wk in four of seven animals, with typical numbers of normal-appearing conceptuses. A fertility rate of 100% returned in four of six animals that became infertile at a single oral dose of 3 mg/kg of gamendazole. No differences in mating behavior were observed in either of the gamendazole-treated groups versus the control (vehicle-only) group. In the animals that showed reversible infertility, a transient increase in circulating FSH levels coincided with an initial decline in inhibin B levels after administration of gamendazole, but no other significant changes in circulating reproductive hormones were observed. Gamendazole inhibited production of inhibin B by primary Sertoli cells in vitro with a median inhibitory concentration of 6.8 thorn+/- 3.0 (SEM) (3/4)x 10(-10) M, suggesting that Sertoli cells are a primary target. A biotinylated gamendazole analogue revealed cytoplasmic and perinuclear binding of gamendazole in primary Sertoli cells. Gamendazole represents the most potent new oral antispermatogenic indazole carboxylic acid to date. Our results, however, demonstrate that additional dose-finding studies are required to improve reversibility and widen the therapeutic window before more detailed drug development of this potential nonhormonal male contraceptive agent can occur.

Gamendazole, an orally active indazole carboxylic acid male contraceptive agent, targets HSP90AB1 (HSP90BETA) and EEF1A1 (eEF1A), and stimulates Il1a transcription in rat Sertoli cells.

Gamendazole was recently identified as an orally active antispermatogenic compound with antifertility effects. The cellular mechanism(s) through which these effects occur and the molecular target(s) of gamendazole action are currently unknown. Gamendazole was recently designed as a potent orally active antispermatogenic male contraceptive agent. Here, we report the identification of binding targets and propose a testable mechanism of action for this antispermatogenic agent. Both HSP90AB1 (previously known as HSP90beta [heat shock 90-kDa protein 1, beta]) and EEF1A1 (previously known as eEF1A [eukaryotic translation elongation factor 1 alpha 1]) were identified as binding targets by biotinylated gamendazole (BT-GMZ) affinity purification from testis, Sertoli cells, and ID8 ovarian cancer cells; identification was confirmed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry and Western blot analysis. BT-GMZ bound to purified yeast HSP82 (homologue to mammalian HSP90AB1) and EEF1A1, but not to TEF3 or HBS1, and was competed by unlabeled gamendazole. However, gamendazole did not inhibit nucleotide binding by EEF1A1. Gamendazole binding to purified Saccharomyces cerevisiae HSP82 inhibited luciferase refolding and was not competed by the HSP90 drugs geldanamycin or novobiocin analogue, KU-1. Gamendazole elicited degradation of the HSP90-dependent client proteins AKT1 and ERBB2 and had an antiproliferative effect in MCF-7 cells without inducing HSP90. These data suggest that gamendazole may represent a new class of selective HSP90AB1 and EEF1A1 inhibitors. Testis gene microarray analysis from gamendazole-treated rats showed a marked, rapid increase in three interleukin 1 genes and Nfkbia (NF-kappaB inhibitor alpha) 4 h after oral administration. A spike in II1a transcription was confirmed by RT-PCR in primary Sertoli cells 60 min after exposure to 100 nM gamendazole, demonstrating that Sertoli cells are a target. AKT1, NFKB, and interleukin 1 are known regulators of the Sertoli cell-spermatid junctional complexes. A current model for gamendazole action posits that this pathway links interaction with HSP90AB1 and EEF1A1 to the loss of spermatids and resulting infertility.