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Merck's new anabolic steroid: MK-0773

It hasn't got an official name yet, but the men at the top of Merck/Schering-Plough Pharma are determined to launch it soon: the anabolic steroid MK-0773. Its structural formula is shown below.

Actually experts expected that S4, which is already available online, would conquer the medical market for muscle, bone and libido enhancers. Or that otherwise this would happen with its chemical brother from the same source: the GTx company. But intrigues in the market for new anabolics make us suspect that the era of the steroids is not over yet.

GTx was set up by the chemists who were the first to make new anabolics without a steroid structure. They are called SARMS: they interact with the androgen receptor, but have almost no androgenic effects. You can read more about them in Chapter 20 of the incomparable Anabolics Book.

GTx was working together with Merck, but when Merck merged with Schering-Plough the collaboration came to an end. If the press releases are true, GTx intends to go it alone and develop its own SARMs. [ June 11, 2009] Under new management, Merck has resumed research on old-fashioned steroids.

But anabolic steroids have a bad name, which is why the Merck researchers are presenting their MK-0773 as a SARM too. SARM is a far more positive term than 'anabolic steroid' these days - although even trenbolone has SARM-like characteristics, some researchers have declared in recent reviews. [Steroids. 2010 Jun; 75(6): 377-89.]

Researchers at Merck Research Laboratories recently published results of tests of MK-0773 on rats in the Journal of Biological Chemistry. They still had some of the 4-aza steroid lying around. And when they subjected a whole range of compounds to a new test, the researchers discovered that MK-0773 had some interesting effects. The new test measured whether compounds could do interesting things with the androgen receptor without too many side effects.

DHT, the researchers discovered, attaches itself 6 times better to the androgen receptor than MK-0773. The killer steroid methyltrenbolone does so even 8 times better.

Nevertheless, MK-0773 increases lean body mass in rats. True, you need more mg/kg bodyweight than you do of DHT, but the androgenic side effects measured in this case as effect on the seminal vesicles are negligible.

Merck's new anabolic steroid: MK-0773

Merck's new anabolic steroid: MK-0773

MK-0773 reduced cholesterol levels less than DHT does.

Merck's new anabolic steroid: MK-0773

At present there's the grand sum of 1 publication on the new substance available on PubMed, but Merck has now completed 3 human trials using oral versions of MK-0773. [] These included trials that compared the effect of MK-0773 with that of good ol' testosterone. We reserve judgement on MK-0773 until these studies have been published.

J Biol Chem. 2010 May 28; 285(22): 17054-64.

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