Exceptionally potent antispermatogenic compounds from 8-halogenation of (4aRS,5SR,9bRS)-hexahydroindeno-[1,2-c]pyridines

Magnesiate-Utilized/Benzyne-Mediated Approach to Indenopyridones from 2-Pyridones: An Attempt To Synthesize the Indenopyridine Core of Haouamine

An efficient, short-staged synthesis of cis-fused indeno[2,1-b]- and indeno[1,2-c]pyridin-2-ones, starting from 2-pyridones, using magnesiates of type R₃MgLi as nucleophilic and deprotonation agents, mediated by benzyne generated in situ, under optimized conditions, is described. Following the developed protocol, rare C4a-arylsubstituted indeno[2,1-b]pyridones, resembling the core of haouamine, were obtained. The protocol offering the one-pot synthesis directly from 2-pyridone is also described.

New frontiers in nonhormonal male contraception

The world's population is nearing 6.8 billion, and we are in need of a male contraceptive that is safe, effective, reversible and affordable. Hormonal approaches, which employ different formulations of testosterone administered in combination with other hormones, have shown considerable promise in clinical trials, and they are currently at the forefront of research and development. However, the long-term effects of using hormones throughout a male's reproductive life for contraception are unknown, and it may take decades before this information becomes available. Because of this, many investigators are aiming to bring a nonhormonal male contraceptive to the consumer market. Indeed, there are several distinct but feasible avenues in which fertility can be regulated without affecting the hypothalamus-pituitary-testis axis. In this review, we discuss several approaches for fertility control involving the testis that one day may lead to the development of a nonhormonal male contraceptive.

Mechanism of action of l-CDB-4022, a potential nonhormonal male contraceptive, in the seminiferous epithelium of the rat testis

The present study was conducted to elucidate the possible molecular mechanisms involved in the antispermatogenic activity of l-CDB-4022, an indenopyridine. In this study 45-d-old male Sprague-Dawley rats were treated with a single oral dose of l-CDB-4022 (2.5 mg/kg) or vehicle, and blood and testes were collected at various time points. The rate of body weight gain was not affected, but a significant loss of testes weight was induced by l-CDB-4022. Serum hormones were assayed using specific RIAs or ELISAs, and testicular protein and RNA were analyzed by Western blotting and RT-PCR, respectively. There was a significant decrease in inhibin B and concomitant increase in FSH in serum from l-CDB-4022-treated rats, but serum levels of activin A, testosterone, and LH were unchanged. Western analysis of testicular lysates from l-CDB-4022-treated rats exhibited phosphorylation of ERK1/2 at 4 h and later time points. Loss of nectin/afadin complex occurred at 48 h, but there was an increase in levels of integrin-beta1, N-cadherin, alpha-catenin, and beta-catenin protein at 24 h and later time points. Increase in expression of Fas ligand and Fas receptor was detected 8 and 24 h after l-CDB-4022 treatment. The ratio of the membrane to soluble form of stem cell factor mRNA was decreased. Immunohistochemical analysis of testicular sections indicated a dramatic disruption of the Sertoli cell microtubule network in l-CDB-4022-treated rats. Collectively, these results suggest that l-CDB-4022 activates the MAPK pathway, reduces expression of prosurvival factors such as the membrane form of stem cell factor, alters expression of Sertoli-germ cell adherens junction proteins, disrupts Sertoli cell microtubule structure, and induces the proapoptotic factor, Fas, culminating in germ cell loss from the seminiferous epithelium.

Disruption of spermatogenesis and Sertoli cell structure and function by the indenopyridine CDB-4022 in rats

The present studies were undertaken to determine the testicular cell type(s) affected by the antispermatogenic indenopyridine CDB-4022. At the oral threshold dose (2.5 mg/kg), CDB-4022 induced infertility in all males. CDB-4022 did not alter (P > 0.05) Leydig cell function as assessed by circulating testosterone, seminal vesicle, and ventral prostate weights or body weight gain compared to controls. Conversely, CDB-4022 reduced (P < 0.05) testicular weight, spermatid head counts, and percentage of seminiferous tubules undergoing spermatogenesis. In a second study, adult male rats received a maximally effective oral dose of CDB-4022 (12.5 mg/kg), dipentylphthalate (DPP; 2200 mg/kg; a Sertoli cell toxicant), or vehicle and were necropsied 3, 6, or 12 h after dosing to determine acute effects. Serum inhibin B levels were suppressed (P < 0.05) by 6 h after CDB-4022 or DPP treatment, but epididymal androgen-binding protein (ABP) levels were not altered (P > 0.05), compared to controls. CDB-4022 and DPP increased (P < 0.05) the percentage of tubules with apoptotic germ cells, particularly differentiating spermatogonia and spermatocytes, by 12 h after dosing. Microscopic examination of the testis indicated a greater degree of vacuolation in Sertoli cells and initial signs of apical germ cell sloughing/shedding by 3 or 12 h after CDB-4022 or DPP treatment, respectively. In a third study, prepubertal male rats were treated with vehicle, 12.5 mg/kg of CDB-4022, or 2200 mg/kg of DPP, and the efferent ducts of the right testis were ligated 23 h before necropsy. Seminiferous tubule fluid secretion (difference in weight of testes), serum inhibin B levels, and ABP levels in the unligated epididymis were reduced (P < 0.05) at 24 and 48 h after dosing in CDB-4022- and DPP-treated rats compared to controls. Collectively, these data suggest that CDB-4022 disrupts spermatogenesis by inducing apoptosis in early stage germ cells via a direct action on the Sertoli cell.

Lupron depot prevention of antispermatogenic/antifertility activity of the indenopyridine, CDB-4022, in the rat

The goals of this study were to determine the CDB-4022 dose-response relationship for induction of acute decreases in testicular weight and germ cell depopulation in rats; establish the threshold dose of CDB-4022 required to induce infertility; and investigate whether CDB-4022-induced testicular damage could be prevented by a GnRH agonist (Lupron Depot). Reduction of testis weight and germ cell depopulation were observed 7 days after a single oral dose of 1 mg CDB-4022/kg, whereas 0.5 mg/kg had no observable effect. These effects were maximal at 12.5 or 25 mg CDB-4022/kg. After a single oral dose of either 2.5 or 5 mg/kg, CDB-4022 induced infertility in five of five treated rats by Week 5, whereas only one of five males was rendered infertile at a dose of 1 mg/kg. Proven fertile male rats (6/group) were treated with vehicle, CDB-4022 alone (2.5 mg/kg on Day 0), CDB-4022 plus Lupron Depot (on Weeks -1, 2, 5, and 8), or Lupron Depot alone. Control males demonstrated normal fertility throughout a 32-wk cohabitation period. Five of six rats were rendered transiently infertile with Lupron Depot alone, but all recovered fertility. CDB-4022 treatment resulted in infertility in all six rats, and only one of six regained fertility. Combined treatment also caused infertility in all six rats, but four of six recovered fertility (P = 0.08 compared to CDB-4022 alone). Testicular weight was decreased in the three treatment groups compared to vehicle controls; testicular weights were ranked from highest to lowest as follows: vehicle > Lupron Depot > Lupron Depot + CDB-4022 > CDB-4022. The tubule differentiation index of Lupron Depot-treated rats (96 +/- 4%) was not different from vehicle-treated rats (100%). CDB-4022 treatment decreased the number of differentiating tubules (15 +/- 8%). Lupron Depot plus CDB-4022 treatment resulted in a greater number of differentiating tubules (53 +/- 12%) than CDB-4022 alone, but this was still lower than vehicle- or Lupron Depot-treated rats. These data indicate that 2.5 mg/kg of CDB-4022 was the oral threshold dose that caused testicular damage rendering the majority of adult male rats permanently infertile within the study interval; 12.5 mg/kg of CDB-4022 induced maximal testicular damage. Suppression of gonadotropins and/or testosterone production by treatment with Lupron Depot before and after CDB-4022 prevented the CDB-4022-induced irreversible testicular damage.

28-day toxicology test: indenopyridine RTI 4587-056 in male Sprague-Dawley rats

The potential toxicity of RTI 4587-056, a hexahydroindenopyridine analog of SANDOZ 20-438, was examined in adult male Sprague-Dawley rats. Testicular, intestinal, and erythropoietic histology was assessed after 28 days of gavage treatment at 0, 10, and 100 mg/kg/day. During the first 10 days, dose-related clinical signs included mild to moderate lethargy shortly after dosing, lower consumption of feed and water, and body weight loss or decreased weight gain. Tolerance developed, such that lethargy disappeared and weight gains were equivalent to the control group during the second through fourth weeks. The compound did not affect intestinal epithelium or bone marrow. RTI 4587-056 was a highly effective antispermatogenic agent at both doses causing epididymal hypospermia and testicular atrophy. Based upon the Spermatogenic Index ratings, still lower doses would be effective male contraceptive agents. RTI 4587-056 has potential as a male contraceptive without overt side effects. Further testing is required.