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<<   作成日時 : 2012/08/17 20:04   >>

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男性用ピルの開発が近づく
画像 女性用の経口避妊薬は何十年も前から使用されているが、男性用はまだである。
 マウスでの最新の米国の研究では性欲を妨げずに一時的に不妊になることが示された。精子の生成に重要なタンパク質を標的とした薬剤はJQ1と呼ばれる。研究開発の課題の一つは血液から精巣への運搬にあった。
 従来の開発アプローチは男性ホルモンであるテストステロンを操作して精子の生産を止めようとしてきたが、どれも通常の使用には適さなかった。

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17 August 2012 Last updated at 00:41 GMT
Male contraceptive pill 'step closer' after mice studies
By James Gallagher
Health and science reporter, BBC News
http://www.bbc.co.uk/news/health-19281690

Scientists believe they are a step closer in the difficult journey towards developing a male contraceptive pill, after successful studies in mice.

A contraceptive pill for women has been around for decades, but an equivalent for men has proved elusive.

A US study, published in the journal Cell, showed a drug could make mice temporarily infertile without hampering their sex drive.

Experts said the findings were "exciting", but needed tests in people.

It has been argued that the lack of a male contraceptive pill has contributed to the number of unplanned pregnancies.

One of the challenges is developing a drug which can cross over from the blood into the testes.

US researchers at the Dana-Farber Cancer Institute and Baylor College of Medicine were testing a drug called JQ1. It targets a protein which exists only in the testes and is critical for sperm production.

'Profound effects'
The testes of mice taking the drug began to shrink as they produced fewer sperm, which were also less mobile. Some were rendered infertile.

When the animals were no longer taking the drug they were able to have babies.

One of the researchers, Dr James Bradner said: "This compound produces a rapid and reversible decrease in sperm count and motility with profound effects on fertility.

"These findings suggest that a reversible, oral male contraceptive may be possible."

Researchers hope to be able to target the same protein in men, however, more tests will be needed to show whether the drug is both safe and effective in people.

Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, told the BBC there was a need for such a pill.

"To date, most of the trials have attempted to stop sperm production by manipulating the male hormone testosterone through the use of injections or implants.

"These approaches work reasonably well, but none have yet made it to routine use. So the door is wide open for someone to develop a novel drug that doesn't rely on hormones."

He said it should be fairly easy to test this latest approach in humans.

Prof Moira O'Bryan, the head of male infertility at Monash University in Australia, said: "This is an exciting report that could have major scientific and social impacts."

She added: "The strong similarity between sperm production in the mouse and the human suggest that a variation of JQ1 may ultimately result in a human contraceptive.

"Although there is undoubtedly an urgent need for additional contraceptive options, the path between this paper and a new product is likely to be long."

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Cell, Volume 150, Issue 4, 673-684, 17 August 2012
Copyright 2012 Elsevier Inc. All rights reserved.
10.1016/j.cell.2012.06.045

Small-Molecule Inhibition of BRDT for Male Contraception

Authors
Martin M. Matzuk, Michael R. McKeown, Panagis Filippakopoulos, Qinglei Li, Lang Ma, Julio E. Agno, Madeleine E. Lemieux, Sarah Picaud, Richard N. Yu, Jun Qi, Stefan Knapp, James E. BradnerSee Affiliations

Highlights
Bromodomain, testis-specific (BRDT) is a contraceptive target
JQ1 is a BRDT inhibitor that causes a reversible contraceptive effect in male mice
JQ1 alters spermatogenesis at the spermatocyte and round spermatid stages
JQ1 treatment targets the male germline and reduces spermatozoa number and motility

Summary
A pharmacologic approach to male contraception remains a longstanding challenge in medicine. Toward this objective, we explored the spermatogenic effects of a selective small-molecule inhibitor (JQ1) of the bromodomain and extraterminal (BET) subfamily of epigenetic reader proteins. Here, we report potent inhibition of the testis-specific member BRDT, which is essential for chromatin remodeling during spermatogenesis. Biochemical and crystallographic studies confirm that occupancy of the BRDT acetyl-lysine binding pocket by JQ1 prevents recognition of acetylated histone H4. Treatment of mice with JQ1 reduced seminiferous tubule area, testis size, and spermatozoa number and motility without affecting hormone levels. Although JQ1-treated males mate normally, inhibitory effects of JQ1 evident at the spermatocyte and round spermatid stages cause a complete and reversible contraceptive effect. These data establish a new contraceptive that can cross the blood:testis boundary and inhibit bromodomain activity during spermatogenesis, providing a lead compound targeting the male germ cell for contraception.

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