Selective Androgen Receptor Modulator (SARM)

• Non-hormonal Anabolic Compound
• Increases Lean Muscle Mass
• Promotes Fat Loss
• Promotes Recovery
• Increases Libido
• Safe for Males & Females
• Can be used for PCT and Bridging

(MK-2866) ~ 4-cyanophenoxy)-N-[4-cyano-3-(trifluoromethyl)phenyl]-2-hydroxy-2-methylpropanamide)




Osta Rx™ is a Selective Androgen Receptor Modulator. A SARM is exactly what it sounds like: a compound (not an anabolic steroid) which has the ability to stimulate the androgen receptor (much the same way as anabolic steroids). Osta Rx™ is an orally active (and highly bioavailable) selective agonist for androgen receptors which was shown to have anabolic effects in muscle and bone tissue. It has been shown to have no measurable effect on lutenizing hormone (LH) or follicle-stimulating hormone (FSH), but it has been shown to have some effect on prostate weight, with an androgenic potency around 1/3rd of its anabolic potency. Still, this is a good trade-off, because it’s anabolic effect has been measured to be roughly the same as testosterone. It has also been shown to produce dose-dependent increases in bone mineral density and mechanical strength in addition to being able decrease body fat and increase lean body mass.

Selective androgen receptor modulators (SARMs) bind to the androgen receptor and demonstrate osteo (bone) and myo (muscular) anabolic activity. Binding and activation of the Androgen receptor alters the expression of genes and increases protein synthesis, hence builds muscle. So in essence, SARMs such as Osta Rx™ causes muscle growth in the same manner as steroids, however unlike testosterone and other anabolic steroids and prohormones, SARMs (as nonsteroidal agents) don’t produce the growth effect on prostate and other secondary sexual organs.

Osta Rx™ in particular exerts its anabolic effects on muscle tissue almost exclusively. So not only does it represent a new potential treatment option for a wide spectrum of conditions from muscle wasting diseases (from age-related to AIDS or cancer-related), but is also has immense potential for muscle building for Bodybuilders, fitness, athletes and an agent to minimize atrophy during recovery periods from serious surgery or similar situations.

MK-2866 aka Ostarine, belongs to a class of chemicals known as SARMs or selective androgen receptor modulators. SARMs create selective anabolic activity at certain androgen receptors and not others, hence their name. Compared to testosterone and other anabolic steroids and pro hormones, the advantage of SARMs such as MK-2688 is that they do not have androgenic activity in non-skeletal-muscle tissues. 

MK-2866 is effective in not only maintaining lean body mass (LBM) but actually increasing it. 

It is often described or named S1 on various internet sources, however this is actually incorrect as S1 was a SARM that was developed quite early and is no longer undergoing any further development. 

Selective androgen receptor modulators (SARMs) bind to the androgen receptor and demonstrate osteo (bone) and myo (muscular) anabolic activity. 

Androgen receptor activation 

Binding and activation of the Androgen receptor alters the expression of genes and increases protein synthesis, hence builds muscle. 

So in essence, SARMs such as MK-2866 causes muscle growth in the same manner as steroids, however unlike testosterone and other anabolic steroids and prohormones, SARMs (as non-steroidal agents) don’t produce the growth effect on prostate and other secondary sexual organs. 

MK-2866 in particular exerts its anabolic effects on muscle tissue almost exclusively. So not only does it represent a new potential treatment option for a wide spectrum of conditions from muscle wasting diseases (from age-related to AIDS or cancer-related), but is also has immense potential for muscle building for Bodybuilders, fitness, athletes and an agent to minimize atrophy during recovery periods from serious surgery or similar situations. 

To date, GTx has evaluated MK-2866 in eight clinical trials involving approximately 600 subjects including three efficacy studies. A four month Phase IIb clinical trial enrolled 159 patients with the study meeting its primary objective of an absolute increase in total lean body mass (muscle) compared to placebo and the secondary objective of muscle function (increase in strength). 

Is MK-2866 commercially available? Most of the purchasing options for SARMs are from Research Chemical companies, whether they be genuine distributors of pharmaceutical grade research chemicals, or supplying exclusively to the bodybuilder/athlete/fitness enthusiast. 

There has been debate to any commercial source of MK-2866 as the GTx, the company which invented it and released its patents has not given out the EXACT chemical structure. 

As MK-2866 is the most anabolic of the available SARMs, its first and foremost use must be when trying to gain lean muscle. 

Now the gains in absolute weight won’t be comparable to steroids such as Dianabol, however what will be gained will almost exclusively be lean mass. Due to the lack of shutdown in comparison to steroids/prohormones, a PCT period is not needed and almost all the mass that is gained on MK-2866 is kept once the cycle is finished. 

Doses of 25mg for 4-6 weeks are the most common protocol for such goals. Over this 4-6 week period will typically produce 6lbs or 3kg of lean, keepable gains. However the abundant side effects of steroids/prohormones will not be present. 

Users have as high as 36mg [only recommended for those who weigh in at 210lbs (95kg)+] for periods as long as 8 weeks. However the potential for suppression from such doses is higher and users would have to look into a PCT protocol after undergoing such a cycle. 

As the majority of MK-2866 supplies come in 30ml bottles at 25mg/ml, a dose of 17.5mg per day will give the user a 6 week cycle from one bottle, a very good compromise between an anabolic dose and cost. 

MK-2866 would primarily fit into a cutting protocol for the maintenance of muscle mass whilst reducing calories. One of the most disheartening outcomes of cutting is the loss hard earned muscle mass. 

The drop in metabolic rate and hormone levels (T3, IGF, Testosterone etc) with the lack of calories is a perfect catabolic environment for loss of muscle tissue. 

As MK-2866 has anabolic effects, the dieter can cut calories without having to worry about muscle or strength loss. 

MK-2866 has also shown noticeable nutrient partitioning effects among users, another reason why it can be of great help when cutting. 

A 12.5-15mg dosing protocol for 4-6 weeks is good for cutting with MK-2866 without undergoing any side effects or suppression. However it must be stated that due to the lack of androgenic activity, muscle hardness and overall results are not as prominenant as with the SARM S-4. 

In our opinion, along with lean gains in muscle mass, recomping is where MK-2866 really shines. 

The recomping effect of losing fat and gaining muscle at the same time is what the majority of users are looking for. Trying to achieve this when you are not absolutely new to training is extremely difficult. 

Where MK-2866 shines for recomping is in its nutrient partitioning benefits. Calories are taken from fat stores and calorie intake is fed to the muscle tissue. In fact many users report that MK-2866 consumed at maintenance calories produces weight loss, whilst still getting increases in strength and muscle mass! 

One of the most important factors of recomping is TIME. As you are trying to achieve multiple objectives, it requires a longer time period to notice good recomp effects so even when running steroids, these would have to be longer run injectable compounds as oppose to the short used liver toxic oral steroids/prohormones. 

Although MK-2866 is taken orally, as it is not methylated it is not as liver toxic as other oral steroids/prohormones. Therefore it can be run for longer than the standard 4 week period with the aforementioned compounds. 

The dosing protocol of 12.5-25mg for 4-8 weeks will give excellent recomp effects. 

Diet must also be optimized to where calories are just above maintenance with at least 30% coming from lean sources of protein to get the best recomp effect. 

As mentioned by Furuya, the effects of MK-2688 translate to anabolism in bone as well as skeletal muscle tissue, which means it could be used in the future for a wide variety of uses such as osteoporosis and as a concurrent treatment with drugs that reduce bone density. 

Therefore it has great application as a compound to use for rehabilitation of injuries, in particular bone and tendon related injuries. 

Doses of 12.5mg per day is recommend for such purposes and improvement in joint movement that can be seen after just 6-8 days. Timing of Doses As MK-2866 has a half life of around 24 hours, each of these doses only has to be taken orally once a day, therefore its also offers an extremely convenient supplementation intake. 

MK-2866 and estrogen concern SARMs cannot be aromatized, conferring all their effects to AR binding and not to metabolic conversion to active androgens/estrogens. 

However blood work from users has shown a slight elevation in serum estradiol levels (which may be one of the factors in its high effectiveness for treating tendon, ligament, and bone injuries or illnesses. 

This elevation is extremely small and is no case for concern. If however you are absolutely concerned about slight increases in Estrogen, you can always opt for low doses of OTC AI’s such as 6bromo or very very low doses of prescription AI’s like Adex or Aromasin. 

Advantages Of MK-2866 when compared to Steroids/Prohormones 

• There is no need for pre cycle supports such as Hawthorn berry. 
• There is no need for on cycle supports such as milk thistle for the liver, policosanol or RYR for cholesterol etc. 
• Some suppression may be present at doses of 25mg+ run for longer than 4 weeks, however a stringent PCT of prescription SERMs like Nolva or Clomid is not necessary. 
• High oral biovailabilty without significant damage to your liver as with oral steroids/prohormones. 
• Great sense of well being while on, (without the aggression which can often detrimentally impact users daily lifes). 
• No need for a long time period off between cycles; the recommended time of period for normal cycles would be Time on +PCT, so for a typical 6 week cycle and 4 week PCT, a user would have to wait another 10 weeks after PCT to start another cycle. 
• MK-2866 (MK-2866) also resulted in a dose-dependent decrease in LDL and HDL cholesterol levels, with the average LDL/HDL ratio for all doses remaining in the low cardiovascular risk category – hence there is little impact on cholesterol values. 

Advantages Of MK-2866 when compared to other SARMs 

The metabolite M1 which seems to cause toxicity in S4 (temporary occular disturbances) is not present in MK-2866. Also unlike S4, MK-2866 does not have androgenic properties in non muscle tissue. 

MK-2866 Summary 

• Anabolic even at doses as low as 3mg 
• Great for strength 
• Great for lean mass gains 
• Great for body recomposition 
• Great for endurance (aerobic or anaerobic) 
• Joint healing abilities 
• Half life of circa 24 hours – only once a day dosing required 

MK-2866 Use In PCT 

One of the most recent popular uses of SARMs has been during the critical PCT period following a cycle of anabolic steroids or pro hormones. 

To see why, lets look at what happens after a cycle and during the PCT period: 

Shutdown When taking an anabolic androgenic compound, whether it be steroids or prohormones, the bodies own natural production of hormones are affected. 

The bodies detects an abundance of androgens, hence signals the hypothalamus to decrease GnRH excretion. This in turn results in the pituitary gland to lower LH and FSH production which in turn signals the leydig cells in the testes to stop producing testosterone. 

HPTA Feedback Loop 

This negative feedback loop is the reason why testicular atrophy or shrinkage of the testes occurs on cycle. 

The Role of PCT 

Post Cycle Therapy The objective of a PCT (Post Cycle Therapy) is to quickly get the body to normalize its prodcution of the above hormones, and hence signal your body to resume testosterone production. 

The most common and effective compounds used to accomplish this are the SERMs (selective estrogen receptor modulators) Nolva (tamoxifen citrate) and Clomid (Clomiphene citrate). 

Nolva and Clomid are used immediately following a cycle to get the body back to homeostasis (normal hormone levels) at a faster rate. 

However even with Nolva/Clomid use, there is still a delay period for hormone levels to rach their normal levels. It is in this delay period where the loss of muscle and loss of strength gains occurs in PCT. 

MK-2866 in PCT This is where an anabolic SARM like MK-2866 offers it benefits. As MK-2866 selectively binds to the androgen receptor in muscle and bone, it continues activation of the androgen receptor while Nolva and Clomid are bringing the natural testosterone production back to normal. 

As a result of this continued activation in the muscle, the loss of muscle mass and strength in PCT is minimized and most users even report an increase in strength from the numbers they were pushing on cycle! 

Food Intake Another very important factor in PCT is CALORIES. As mentioned previously, the endocrine system is not at optimal function following a cycle. 

The body strives for homeostasis and after a cycle is in a state quite often where it has gained an amount of mass that it is not used to. 

In order to keep hold of this (particularly when in a less than optimal hormonal environment), the Calorie consumption must be at or greater than was present whilst on cycle. 

Even knowing this, users can be hesitant to consume so many calories due to no longer being on cycle and the resultant fat gain that may come with the high calories. 

The anabolic and nutrient partitioning effects of MK-2866 allows the user to keep up their calories during PCT without the resultant fat gain.