5α-reductase

As expected, dutasteride prevents the conversion of 3H-T to 3H-DHT and T-induced PSA production and proliferation. Nevertheless, the medication also prevented cell division and PSA secretion triggered by DHT (IC50 = 1 μM)[1]. Dutasteride has an IC50 of about 1.5 μM and competes with LNCaP cell AR binding. Elevated levels of dutasteride (10-50 μM) in steroid-free media led to increased cell death, potentially through apoptosis, but not finasteride[1]. In both of the studied cell lines for androgen-responsive (LNCaP) and androgen-unresponsive (DU145) human prostate cancer (PCa), dutasteride decreases cell viability and proliferation [2].

With a terminal half-life of almost 240 hours, GG745 considerably reduced DHT levels in single doses more than 10 mg, compared to finasteride single doses of 5 mg[3]. Using doubled results to account for dutasteride treatment, there was an 8.3% median increase in PSA in men without prostate cancer who were treated with a placebo at month 24, compared to -59.5% in those who got the medication[4]. Toxicity: The dynamics of steroid hormones and male fertility may be impacted by dutasteride. In order to ascertain the impact of dutasteride (10, 32, and 100 μg/L) on fish reproduction, a 21-day reproduction research was carried out. Fish exposed to dutasteride saw a considerable reduction in fecundity and experienced various effects on their reproductive endocrine systems, affecting both male and female fish[5].

Dutasteride inhibited 3H-T conversion to 3H-DHT and, as anticipated, inhibited T-induced secretion of PSA and proliferation. However the drug also inhibited DHT-induced PSA secretion and cell proliferation (IC50 ∼ 1 μM). Finasteride also inhibited DHT action but was less potent than dutasteride. Dutasteride competed for binding the LNCaP cell AR with an IC50 ∼ 1.5 μM. High concentrations of dutasteride (10–50 μM), but not finasteride, in steroid-free medium, resulted in enhanced cell death, possibly by apoptosis. This was accompanied by loss of AR protein and decreased AR ligand-binding activity. Occupation of AR by R1881 partly protected against cell death and loss of AR protein. PC-3 prostate cancer cells, which do not contain AR, also were killed by high concentrations of dutasteride, as well as by 50 μM finasteride. CONCLUSIONS Dutasteride exhibited some inhibitory actions in LNCaP cells possibly related to 5αR inhibition but also had antiandrogenic effects at relatively low concentrations and cell death-promoting effects at higher concentrations. Finasteride also was antiandrogenic, but less than dutasteride. The antiandrogenic effects may be mediated by the mutant LNCaP cell AR. Promotion of cell death by dutasteride can be blocked, but only in part, by androgens[1].

LNCaP cells were incubated for varying times with T or DHT in steroid-free medium in the absence or presence of increasing doses of dutasteride or finasteride and the effects on 5alphaR activity, PSA accumulation in the medium, and on cell proliferation were determined. Drug effects on apoptosis were investigated using Annexin V staining and a cell death ELISA assay. Effects of the drugs on AR ligand-binding activity and on AR protein levels were determined[1].

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dutasteride reduces cell viability and cell proliferation in both cell lines tested. AndroChip 2 gene signature identified in LNCaP a total of 11 genes differentially expressed (FC >or= +/-1.5). Eight of these genes, were overexpressed and three were underexpressed. Overexpressed genes included genes encoding for proteins involved in biosynthesis and metabolism of androgen (HSD17B1;HSD17B3;CYP11B2), androgen receptor and androgen receptor co-regulators (AR;CCND1), and signal transduction(ERBB2; V-CAM; SOS1) whereas, underexpressed genes (KLK3; KLK2; DHCR24) were androgen-regulated genes (ARGs). No differentially expressed genes were scored in DU145. Microarray data were confirmed by quantitative real-time PCR assay (QRT-PCR). These data offer a selective genomic signature for dutasteride treatment in prostate epithelial cells and provide important insights in prostate cancer pathophysiology.[2]

Pharmacokinetic and pharmacodynamic results are reported of treatment with a potent inhibitor of both 5alpha-reductase isozymes, GG745, in rats, dogs and men. In the rat, GG745 has a similar effect on DHT-driven prostatic growth as finasteride, another dual 5alpha-reductase inhibitor in this species. However, GG745 appears to be more potent in the rat, a result that likely reflects the greater inherent potency and terminal half-life of GG745 (14 hr) compared with that of finasteride (1 hr). These pharmacokinetic differences are also maintained in the dog (65 and 4 hr for GG745 and finasteride, respectively). From these results, the literature, and in vitro studies, we estimated doses of GG745 likely to prove efficacious in reducing DHT levels in man. These estimated values were predictive of single-dose effects of GG745 in man. Results from single-dose evaluations in man indicate that GG745 has a terminal half-life of approximately 240 hr, and single doses of >10 mg decreased DHT levels significantly more than did single 5-mg doses of finasteride. These data support the hypothesis that a molecule (GG745) that effectively inhibits both 5alpha-reductases will lower serum DHT levels significantly more than a molecule that inhibits only a single 5alpha-reductase isozyme (e.g., finasteride, a selective inhibitor of the type 2 enzyme in man).[3]

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This research addressed the question of whether or not dutasteride, a pharmaceutical used to treat benign prostatic hyperplasia, may cause adverse effects in a teleost fish, the fathead minnow (Pimephales promelas), by inhibiting the activity of both isoforms of 5α-reductase (5αR), the enzyme that converts testosterone into dihydrotestosterone (DHT). Mammalian pharmacological and toxicological information were used to guide the experimental design and the selection of relevant endpoints, according to the so-called "read-across approach", suggesting that dutasteride may affect male fertility and steroid hormone dynamics. Therefore, a 21-day reproduction study was conducted to determine the effects of dutasteride (10, 32 and 100 μg/L) on fish reproduction. Exposure to dutasteride significantly reduced fecundity of fish and affected several aspects of reproductive endocrine functions in both males and females. However, none of the observed adverse effects occurred at concentrations of exposure lower than 32 μg/L; this, together with the low volume of drug prescribed every year (10.34 kg in the UK in 2011), and the extremely low predicted environmental concentration (0.03 ng/L), suggest that, at present, the potential presence of dutasteride in the environment does not represent a threat to wild fish populations.[5]

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A total of 2,802 men 50 years or older with a clinical diagnosis of benign prostatic hyperplasia, no history of prostate cancer, PSA 1.5 to 10 ng/ml, prostate volume 30 cc or greater, an American Urological Association symptom score of 12 or greater and peak urinary flow rate 15 ml per second or less were randomized to 0.5 mg dutasteride daily or matching placebo for 24 months. Increases in PSA from baseline and the maximum increase from nadir to month 24 were compared between the groups and analyzed by prostate cancer status, as determined by PSA driven biopsy and an advised cutoff of more than 4 ng/ml after doubling to correct for dutasteride treatment with sensitivity and specificity calculated for each.[4]

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100 mg/kg

Rats

Absorption, Distribution and Excretion
Following oral administration of a single dose of 0.5 mg dutasteride, the peak serum concentrations were reached within 2 to 3 hours. Following daily oral administration of 0.5 mg dutasteride, the steady-state concentration of 40 ng/mL is expected to be achieved at 6 months following initial administration. In healthy subjects, the absolute bioavailability was 60%, ranging from 40% to 94%. While food intake reduced the maximum serum concentrations by 10 to 15%, food intake is reported to have a negligible effect on the bioavailability of the drug.
Dutasteride and its metabolites mainly undergo fecal excretion. About 1-15% of the dose is excreted as the unchanged parent compound, while 2-90% of the total dose is excreted in the form of dutasteride-related metabolites in the feces. Trace amounts of unchanged dutasteride, with less than 1%, can also be detected in the urine. Therefore, on average, the dose unaccounted for approximated 55%, with a range between 5% and 97%.
Dutasteride displays a large volume of distribution ranging from 300 to 500 L. Following daily oral administration of 0.5 mg dutasteride healthy subjects for 12 months, the semen dutasteride concentrations averaged 3.4 ng/mL (range: 0.4 to 14 ng/mL) with 11.5% of serum dutasteride concentrations being partitioned into semen.
In a study of healthy volunteers receiving single oral doses of dutasteride ranging from 0.01 to 40 mg, dutasteride displayed a low linear clearance of 0.58 L/h. The estimated inter-individual variability for the linear clearance was high.

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Metabolism / Metabolites
Dutasteride undergoes extensive hepatic metabolism mediated by CYP3A4 and CYP3A5. 4′-hydroxydutasteride, 6-hydroxydutasteride, 6,4′-dihydroxydutasteride, 1,2-dihydrodutasteride, and 15-hydroxydutasteride metabolites are formed. 2 minor metabolites - 6,4′-dihydroxydutasteride and 15-hydroxydutasteride - can also be detected. According to _in vitro_ studies, 4′-hydroxydutasteride and 1,2-dihydrodutasteride mediated inhibitory actions against both isoforms of 5α-reductase but with lower potency when compared to the parent drug. The activity of 6β-hydroxydutasteride is comparable to that of dutasteride.

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Biological Half-Life
The terminal elimination half-life of dutasteride is approximately 5 weeks at steady state. This long half-life accounts for the serum concentrations remaining detectable for up to 4 to 6 months after discontinuation of treatment.

Hepatotoxicity
Dutasteride has been associated with a low rate of serum aminotransferase elevations that, in controlled trials, was no higher than with placebo therapy. These elevations were transient and rarely required dose modification. There have been no published reports of clinically apparent liver injury due to dutasteride therapy.
Likelihood score: E (unlikely cause of clinically apparent liver injury).

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Protein Binding
Dutasteride is about 99% bound to albumin and 96.6% bound to α-1 acid glycoprotein in the serum.

[1]. Dutasteride, the dual 5alpha-reductase inhibitor, inhibits androgen action and promotes cell death in the LNCaP prostate cancer cell line. Prostate. 2004 Feb 1;58(2):130-44.

[2]. Effects of dutasteride on the expression of genes related to androgen metabolism and related pathway in human prostate cancer cell lines. Invest New Drugs. 2007 Oct;25(5):491-7.

[3]. Unique preclinical characteristics of GG745, a potent dual inhibitor of 5AR. J Pharmacol Exp Ther. 1997 Sep;282(3):1496-502.

[4]. Clinical usefulness of serum prostate specific antigen for the detection of prostate cancer is preserved in men receiving the dual 5alpha-reductase inhibitor dutasteride. J Urol. 2006 May;175(5):1657-62.

[5]. Mode of action of human pharmaceuticals in fish: the effects of the 5-alpha-reductase inhibitor, dutasteride, on reproduction as a case study. Aquat Toxicol. 2013 Mar 15;128-129:113-23.

Pharmacodynamics
Dutasteride is a synthetic 4-azasteroid compound that selectively inhibits both the type I and type II isoforms of steroid 5α-reductase, an intracellular enzyme that converts testosterone to 5α-dihydrotestosterone (DHT). Dutasteride works by reducing the levels of circulating DHT. It was also shown to reduce the size of the prostate gland, improve urinary flow, and symptoms of benign prostatic hyperplasia alone or in combination with tamsulosin. The effect of the reduction of DHT by dutasteride is dose-dependent, with the maximum effect observed within 1-2 weeks following initial administration. After 1 and 2 weeks of daily dosing with dutasteride 0.5 mg, median serum DHT concentrations were reduced by 85% and 90%, respectively. The serum concentrations of DHT were maintained to be decreased by more than 90% in 85% of patients following 1 years' administration of oral dutasteride 0.5 mg/day. As evident from the clinical studies, dutasteride may also cause decreases in serum PSA in the presence of prostate cancer.

C27H30F6N2O2

528.53

528.221

C, 61.36; H, 5.72; F, 21.57; N, 5.30; O, 6.05

164656-23-9

Dutasteride-13C6;1217685-27-2

6918296

White to off-white solid powder

1.3±0.1 g/cm3

620.3±55.0 °C at 760 mmHg

242-250ºC

329.0±31.5 °C

0.0±1.8 mmHg at 25°C

1.523

5.61

2

8

2

37

964

7

C[C@]12CC[C@H]3[C@H]([C@@H]1CC[C@@H]2C(=O)NC4=C(C=CC(=C4)C(F)(F)F)C(F)(F)F)CC[C@@H]5[C@@]3(C=CC(=O)N5)C

JWJOTENAMICLJG-VYZSUTEISA-N

InChI=1S/C27H30F6N2O2/c1-24-11-9-17-15(4-8-21-25(17,2)12-10-22(36)35-21)16(24)6-7-19(24)23(37)34-20-13-14(26(28,29)30)3-5-18(20)27(31,32)33/h3,5,10,12-13,15-17,19,21H,4,6-9,11H2,1-2H3,(H,34,37)(H,35,36)/t15-,16-,17?,19+,21+,24-,25+/m0/s1

(4aR,6aS,7S,9aS,9bS,11aR)-N-(2,5-bis(trifluoromethyl)phenyl)-4a,6a-dimethyl-2-oxo-2,4a,4b,5,6,6a,7,8,9,9a,9b,10,11,11a-tetradecahydro-1H-indeno[5,4-f]quinoline-7-carboxamide

GI-198745, GG-745; GI198745, GG745; GI 198745, GG 745; LS-173584; LS 173584; LS173584; trade names: Avodart; Avidart; Avolve; Duagen; Dutas; Dutagen; Duprost.

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (4.73 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)