SARMs

MK-2866

The only one here with a phase 3 record, and it measured two things

7 sections

Top of article
What it actually is
What it is supposed to do
What people take it for
The dose question
How to check you have the right molecule
What people get wrong
What is known about harm

What circulates: 10 to 25 mg a day, reported as the commonest range on guide pages
What was studied: 3 mg a day for 147 days in the phase 3 trials
The gap: Convention runs above the studied dose
How long it lasts: I could not find a published human half life in the material behind the class page. Dosing in every trial was once daily.

What it actually is

MK-2866, also called ostarine and enobosarm, is the most studied compound on this shelf by a wide margin. It reached phase 3 twice, in people starting chemotherapy for lung cancer, and it has 17 registered records across four sponsors. It holds no medicines approval anywhere the searches looked, and it is also the compound most often turning up in anti-doping tests.

What it is supposed to do

It acts selectively on the androgen receptor. What the trials measured, and this is the substance of the argument about it, was mostly a number from a DXA body scan, the X-ray scan that sorts a body into fat, bone and everything else.

What people take it for

Muscle gain and preserving muscle while dieting. What it was trialled for is muscle wasting in cancer, which is a different problem in a different population.

The dose question

What circulates: 10 to 25 mg a day, reported as the commonest range on guide pages
What was studied: 3 mg a day for 147 days in the phase 3 trials; Two completed phase 3 trials in people starting chemotherapy

Above the studied dose

Three to eight times the phase 3 dose, and the trials are worth reading before the dose. Both carried two co-primary endpoints, a body scan measure and a stair climb measure, both scored as responder counts on advice the design paper attributes to the American regulator. At day 84 the scan showed more responders on the drug in both trials. The stair climb showed a smaller gap in the same direction in the first and went the wrong way in the second. Those registry records post percentages and confidence intervals and no statistical test of any kind, so nothing sourced to them says an endpoint passed.

Reported because it is what people use. Nothing here recommends any amount.

How long it lasts

I could not find a published human half life in the material behind the class page. Dosing in every trial was once daily.

Route studied

By mouth, once daily. The two phase 3 trials gave 3 mg a day for 147 days. An earlier phase 2 randomised 120 healthy elderly men and postmenopausal women across five arms at 0.1, 0.3, 1 and 3 mg and placebo for 12 weeks. Later trials in breast cancer used 9 mg and 18 mg.

Route used

By mouth, at 10 to 25 mg a day, reported as the commonest range on guide pages and not as a recommendation.

How to check you have the right molecule

Ostarine, enobosarm and MK-2866 are one compound. Two things are worth knowing about the name. It is the compound most often found in tested products, sometimes in bottles that name something else entirely, and in 2019 it produced 74 anti-doping findings, more than any other name on this list.

Walked through on two real certificates in how to read a certificate of analysis.

What people get wrong

The scan moved further than the person did, and that is the finding worth carrying away. Both phase 3 trials scored two co-primary endpoints as responder counts. At day 84 the body scan measure showed more responders on the drug in both. The stair climb measure showed a smaller gap in the same direction in the first trial and went the wrong way in the second. Those registry records post no statistical test at all, so nothing sourced to them says an endpoint passed either way. The one trial where a functional measure did improve against placebo was the 120 person phase 2, at 3 mg.

What is known about harm

Two published case reports name this compound on its own in liver injury. In the trials, raised liver enzymes were among the commonest higher grade events in the later breast cancer work. The class page carries the fuller picture, including an Australian series of 23 people hospitalised with drug induced liver injury in which 14 of the 40 drugs involved were SARMs, so that 14 is a count of exposures rather than of patients.

Others in SARMs

Everything on this page is a summary. The citations, the studies and the reasoning live in the full entry.

Read the full entry on MK-2866

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