Discovery and Development of GG745, a Potent Inhibitor of Both Isozymes of of 5α-Reductase

Sv, Frye; Hn, Bramson; Dj, Hermann; Fw, Lee; Ak, Sinhababu; Tian, Gaochao

doi:10.1007/0-306-47384-4_17

Cited by 33 publications

(23 citation statements)

References 84 publications

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“…This finding is consistent with the fact that all of these drugs are competitive inhibitors of 5a-reductase (Stoner, 1996;di Salle et al, 1998;Frye et al, 1998). All of the somatic SRD5A2 missense substitutions analysed significantly modified the apparent K i of the normal protein for all three steroid 5a-reductase inhibitors examined (Table 4).…”

Section: Discussionsupporting

confidence: 84%

Identification and characterization of somatic steroid 5α-reductase (SRD5A2) mutations in human prostate cancer tissue

2004

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Prostate cancer is a very common disease in industrialized countries and it is known to be androgen-dependent. The human SRD5A2 gene encodes the prostatic (or type II) steroid 5a-reductase, which catalyses the irreversible conversion of testosterone to dihydrotestosterone (DHT), the most active androgen in the prostate. We have sequenced the entire protein-coding region of this locus in 30 microdissected prostate adenocarcinomas. We identified a total of 17 de novo amino-acid substitutions in 13 of these tumors. We also identified six additional silent substitutions. In total, 18 out of 30 (60%) of the tumors examined had de novo somatic substitutions in the prostatic steroid 5a-reductase-coding region. We also characterized all of the SRD5A2 missense substitutions biochemically and pharmacologically, using three 5a-reductase inhibitors, including finasteride. The biochemical parameters of the distinct 5a-reductase missense substitutions varied substantially. We note that two out of the three recurrent SRD5A2 missense substitutions increased 5a-reductase in vitro activity, while the third one is essentially neutral. These findings are consistent with a role for increased DHT levels in the prostate through increased activity of the SRD5A2 locus in prostate cancer progression, in a subset of patients. Our pharmacologic studies also reveal substantial variability for each 5a-reductase inhibitor. These data, therefore, should be taken into account in both prevention as well as therapeutic trials of prostate cancer utilizing 5a-reductase inhibitors.

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Section: Discussionsupporting

confidence: 84%

Identification and characterization of somatic steroid 5α-reductase (SRD5A2) mutations in human prostate cancer tissue

2004

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“…Replacing the N-t-butyl substituent at C-17 of finasteride with a much more lipophilic N- (2,5-bis(trifluoromethyl))phenyl group (GG745; see Fig. 1) indeed significantly increased the rate of inhibition of 5AR, supporting the strategy to improve the rate of time-dependent inhibition of 5AR by using ligand binding energies provided at C-17 of ⌬ 1 -4-azasteroids (10,11). Although this approach was successful in discovering GG745, whether it was generally possible to use ligand binding energies to optimize the kinetic potency of ⌬ 1 -4-azasteroids remained unclear.…”

Section: Armentioning

confidence: 79%

“…Although it is an extremely potent dual inhibitor of 5AR thermodynamically in vitro, finasteride does not fully suppress plasma dihydrotestosterone level at doses up to 100 mg. A theoretical analysis of pharmacodynamic effects of time-dependent inhibitors indicates that the in vivo effects of such inhibitors depend upon both the kinetic and thermodynamic potency of the inhibitor (9) and provides a theoretical basis for improving the in vivo efficacy of ⌬ 1 -4-azasteroids by improving their kinetic potency in the inhibition of 5AR (10,11). Because a smaller K i value would translate into a greater k 3 /K i , the second order rate constant for the time-dependent inhibition, it was reasoned that improving the affinity of ⌬ 1 -4-azasteroids for 5AR would enhance the kinetic potency of the inhibitors against 5AR (10, 11).…”

Section: Armentioning

confidence: 99%

Linear Relationships between the Ligand Binding Energy and the Activation Energy of Time-dependent Inhibition of Steroid 5α-Reductase by Δ1-4-Azasteroids

Tian

Haffner

2001

Journal of Biological Chemistry

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The inhibition of steroid 5␣-reductase (5AR) by ⌬ 1 -4-azasteroids is characterized by a two-step time-dependent kinetic mechanism where inhibitor combines with enzyme in a fast equilibrium, defined by the inhibition constant K i , to form an initial reversible enzyme-inhibitor complex, which subsequently undergoes a time-dependent chemical rearrangement, defined by the rate constant k 3 , leading to the formation of an apparently irreversible, tight-binding enzyme-inhibitor complex (Tian, G., Mook, R. A., Jr., Moss, M. L., and Frye, S. V. (1995) Biochemistry 34, 13453-13459). A detailed kinetic analysis of this process with a series of ⌬ 1 -4-azasteroids having different C-17 substituents was performed to understand the relationships between the rate of time-dependent inhibition and the affinity of the time-dependent inhibitors for the enzyme. A linear correlation was observed between ln(1/K i ), which is proportional to the ligand binding energy for the formation of the enzymeinhibitor complex, and ln(1/(k 3 /K i )), which is proportional to the activation energy for the inhibition reaction under the second order reaction condition, which leads to the formation of the irreversible, tight-binding enzyme-inhibitor complex. The coefficient of the correlation was ؊0.88 ؎ 0.07 for type 1 5AR and ؊1.0 ؎ 0.2 for type 2 5AR. In comparison, there was no obvious correlation between ln(1/K i ) and ln(1/k 3 ), which is proportional to the activation energy of the second, time-dependent step of the inhibition reaction. These data are consistent with a model where ligand binding energies provided at C-17 of ⌬ 1 -4-azasteroids is fully expressed to lower the activation energy of k 3 /K i with little perturbation of the energy barrier of the second, time-dependent step. 5AR1 catalyzes the NADPH-dependent reductive conversion of testosterone to dihydrotestosterone. Two isozymes of 5AR, designated types 1 and 2, have been described (1, 2). Although 5AR1 is predominantly expressed in skin and liver, 5AR2 is mainly expressed in prostate, seminal vesicles, liver, and epididymis (3). Both 5AR1 and 5AR2 are implicated in benign prostatic hyperplasia (2), a condition affecting the majority of men over age of 60 (4). Intense efforts made over the past decade to develop drugs against the activity of this enzyme has led to the discovery of potent, time-dependent ⌬ 1 -4-azasteroidal inhibitors of 5AR, including finasteride and GG745 (see Fig. 1).Finasteride inhibits both 5AR1 and 5AR2 in a time-dependent manner (5-7). The kinetic mechanism of this time-dependent inhibition is characterized by a fast binding step for the formation of an initial enzyme-inhibitor complex (EI), followed by a time-dependent event leading to the formation of an apparently irreversible enzyme-inhibitor complex (EI*). This timedependent event involves a chemical transformation at the ⌬ 1 double bond (8). The finding of a NADP-dihydrofinasteride adduct as a product of this time-dependent inhibition reaction suggests that the chemical event is a combination of a n...

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“…Finasteride, however, dissociates from the enzyme very slowly, and therefore is a time-dependent inhibitor of steroid 5 -reductase (Faller et al 1993, Tian et al 1994, 1995. In addition, dutasteride (Frye et al 1998), like finasteride, retains the 1,2 bond that is critical for time-dependent inhibition in 4-azasteroids (Russell & Wilson 1994). Thus we decided to compare the kinetics of steroid 5 -reductase inhibition using 10-and 30-min incubation of the enzyme with either finasteride or dutasteride.…”

Section: Introductionmentioning

confidence: 99%

Pharmacogenetic analysis of human steroid 5α reductase type II: comparison of finasteride and dutasteride

Makridakis

Reichardt

2005

Journal of Molecular Endocrinology

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Human steroid 5 -reductase type II is a prostate-specific, membrane-associated enzyme that catalyzes the conversion of testosterone to dihydrotestosterone, the most potent androgen in the prostate gland. Genetic variants of this enzyme have been associated with both the development and the progression of prostate cancer. Both finasteride and dutasteride are competitive inhibitors of the type II steroid 5 -reductase that have been effectively used for the treatment of benign prostatic hyperplasia. Finasteride has also been successfully utilized for prostate cancer chemoprevention. We here investigate 5 -reductase inhibition assays in vitro to measure the effect of incubation time on the apparent inhibition constant (K i ) for both constitutional and somatic (prostate cancer) enzyme variants. Our systematic pharmacogenetic analysis shows that both finasteride and dutasteride are slow, time-dependent inhibitors of steroid 5 -reductase type II, and that the inhibition kinetics depend on the 5 -reductase genotype. We also show that, overall, dutasteride is a more efficient steroid 5 -reductase inhibitor than finasteride. Based on our data, we are able to map areas of the enzyme that are responsible for this time-dependent inhibition for either (or both) enzyme inhibitor(s). This comprehensive pharmacogenetic analysis of steroid 5 -reductase variants unveiled significant pharmacogenetic variation for both finasteride and dutasteride and thus should be taken into account when designing protocols for treatment and/or chemoprevention of prostatic diseases with either one of these 5 -reductase inhibitors since there is considerable pharmacogenetic variation for both drugs.

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Discovery and Development of GG745, a Potent Inhibitor of Both Isozymes of of 5α-Reductase

Cited by 33 publications

References 84 publications

Identification and characterization of somatic steroid 5α-reductase (SRD5A2) mutations in human prostate cancer tissue

Identification and characterization of somatic steroid 5α-reductase (SRD5A2) mutations in human prostate cancer tissue

Linear Relationships between the Ligand Binding Energy and the Activation Energy of Time-dependent Inhibition of Steroid 5α-Reductase by Δ1-4-Azasteroids

Pharmacogenetic analysis of human steroid 5α reductase type II: comparison of finasteride and dutasteride

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