Ostarine vs RAD-140 vs LGD-4033: A Lab Comparison of Three SARMs

Here is a number that should change how you read any SARM comparison. In 2016 a team bought 44 products marketed online as selective androgen receptor modulators and tested every one. Only 23 actually held a SARM. Seventeen held some other unapproved drug, four held nothing active, and the amount on the label matched the vial in just 18 cases out of 44 ^[1].

The SARMs that did show up were ostarine, LGD-4033 and andarine. Two of those sit on this page. So we will get to binding affinities and metabolism, but keep that survey in mind the whole way down, because none of the chemistry below matters if the powder isn’t what the label claims.

Three molecules, three chemical families

They all grab the androgen receptor. None of them looks like testosterone, which is built on a four-ring sterol core. Past that, they barely resemble each other.

Ostarine is an aryl-propionamide. That puts it in the same chemical family as andarine and several of the first-generation SARMs the anti-doping labs cut their teeth on ^[2]. LGD-4033 is the little one of the three, a pyrrolidine ring carrying two trifluoromethyl groups. RAD-140 is the outlier, with a 1,3,4-oxadiazole bridged to a cyanophenyl group and a chlorine hung off its benzonitrile ring ^[3].

Why does any of that matter? Because the scaffold decides where liver enzymes bite. And that, as we will see, is the whole ballgame for a study that runs longer than an afternoon.

Binding data, and why you can’t just line it up

RAD-140 has the cleanest published numbers, because its discovery paper reported everything in one assay. Radius Health measured a Ki of 7 nM at the androgen receptor. Testosterone came in at 29 nM and DHT at 10 nM on the same bench. The closest thing to an off-target was the progesterone receptor, way out at an IC50 of 750 nM. In a C2C12 myoblast assay RAD-140 acted as an agonist with an EC50 of 0.1 nM, next to 0.05 nM for DHT ^[4].

We would love to fill the same two rows for ostarine and LGD-4033. The trouble is that their published affinities come from different labs, different radioligands, different formats. Line those Ki values up in a table and you are comparing rulers marked in different units. If affinity is your real question, run all three together in one assay. Don’t trust a number you stitched out of three papers.

A 2026 docking study makes the case for us. Ostarine scored well against five different nuclear receptors (androgen, estrogen, progesterone, glucocorticoid and mineralocorticoid), from -10.42 to -12.05 kcal/mol, and showed no special preference for the androgen receptor ^[5]. The authors’ conclusion was blunt: computed binding energy does not predict the tissue selectivity SARMs are named for. Only a wet-lab assay does.

The assay can fool you from the other direction too. One 2019 study ran RAD-140 and two cousins through a yeast screen and through a mammalian reporter-gene assay. For one of the compounds the two EC50 values came out about a thousandfold apart ^[6]. Same molecule. Different test tube. Wildly different answer.

Metabolism, the part the label skips

Run your experiment past a few hours and the parent compound stops being the only thing in the well. Each of these three falls apart on its own route, and those breakdown products are exactly what forensic chemists chase.

LGD-4033 is mapped best. In one study the vial was confirmed to hold LGD-4033 and nothing else, then human liver microsomes and S9 fractions spun out five metabolites. All five were changes to the pyrrolidine ring, and two also showed up as glucuronide conjugates ^[7].

RAD-140 is messier. A 2023 group pitted three in vitro systems against a real human urine sample: liver fractions, liver spheroids on a chip, and electrochemical conversion. Urine held 16 metabolites. The liver-on-a-chip found 14, the plain liver fraction 13, and the electrochemical route only 7 ^[8]. Not one in vitro method caught the full human picture. So the system you pick quietly decides what you detect.

Ostarine, true to its chemical class, mostly goes by hydroxylation, dephenylation and demethylation in liver fractions, then picks up glucuronidation and sulfation once it is inside a live animal ^[2]. Same lesson as the other two. Choose the metabolism model on purpose.

Reading SARM research in 2026

Three things travel with you from every section above.

First, identity and amount come before everything. More than half the products in that 2016 survey were wrong ^[1], so a certificate of analysis tied to your specific lot is the floor, not a bonus. Second, hold the assay steady, because yeast versus mammalian cells moved an EC50 a thousandfold ^[6]. Third, read docking as a guess and not a verdict, since binding energy missed ostarine’s selectivity entirely ^[5].

For the paperwork side, our certificate of analysis explainer covers what a usable COA actually contains, and our third-party testing overview gets into independent verification.

References

1. Van Wagoner RM, et al. JAMA. 2017;318(20):2004-2010. PubMed 29183075
2. de Rijke E, et al. Food Addit Contam Part A. 2013;30(9):1517-1526. PubMed 23883284
3. PubChem compound records: ostarine (CID 11326715), LGD-4033 (CID 44137686), RAD-140 (CID 44200882).
4. Miller CP, et al. ACS Med Chem Lett. 2010;2(2):124-129. PubMed 24900290
5. Mihalev K, et al. Int J Mol Sci. 2026;27(13):5765. PubMed 42450037
6. Zierau O, et al. J Steroid Biochem Mol Biol. 2019;189:81-86. PubMed 30825507
7. Geldof L, et al. Drug Test Anal. 2017;9(2):168-178. PubMed 26767942
8. Wagener F, et al. Anal Bioanal Chem. 2023;415(23):5657-5669. PubMed 37421437

Disclaimer: This content is intended for research purposes only and is not meant to constitute medical advice.