Selective Androgen Receptor Modulators (SARMs) are a class of synthetic ligands designed to bind the androgen receptor (AR) with tissue-selective activity. Of the many SARMs under investigation, three have accumulated the most substantial preclinical and early clinical research datasets: RAD-140 (Testolone), LGD-4033 (Ligandrol), and Ostarine (MK-2866).
This article provides a structured research comparison of their binding profiles, potency, published study findings, and relative positions in the SARM literature — for laboratory reference purposes only.
What Are SARMs? Brief Research Background
SARMs interact with androgen receptors through a mechanism distinct from anabolic-androgenic steroids. Rather than binding and activating the AR uniformly across all tissues, SARMs are engineered to act as selective agonists or partial agonists — promoting anabolic gene transcription in muscle and bone while having limited or modulating effects at other AR-expressing sites (prostate, skin, liver).
The selectivity mechanism involves conformational changes in the AR ligand-binding domain that differ from those induced by testosterone, allowing differential co-activator and co-repressor recruitment depending on tissue type. None of the three compounds discussed here have regulatory approval for therapeutic use in any jurisdiction.
RAD-140 (Testolone) — Research Profile
- Classification: Non-steroidal SARM
- Developer: Radius Health
- AR binding affinity: Ki ~7 nM (high)
- Anabolic:androgenic ratio: ~90:1 in preclinical models (vs testosterone 1:1)
RAD-140 is among the most potent SARMs currently under preclinical investigation. Research has demonstrated strong anabolic activity in skeletal muscle and bone in animal models, with attenuated androgenic activity in prostate tissue compared to testosterone equivalents. A 2017 study published in Endocrinology showed RAD-140 induced anabolic effects in primates and neuroprotective properties in rat neural cell models.
Safety signal considerations: Case reports in the human observational literature have described hepatotoxicity (liver enzyme elevation) associated with RAD-140 use, and cardiovascular markers have been flagged in some reports. These signals warrant careful consideration in study design and risk assessment frameworks.
LGD-4033 (Ligandrol) — Research Profile
- Classification: Non-steroidal SARM
- Developer: Ligand Pharmaceuticals / Viking Therapeutics
- AR binding affinity: Ki ~1 nM (very high)
- Anabolic:androgenic ratio: ~10:1 in preclinical models
LGD-4033 has the most substantial Phase I human clinical data of the three compounds. A landmark 2013 Phase I randomised controlled trial published in The Journals of Gerontology demonstrated dose-dependent lean body mass increases in healthy male volunteers over 21 days, with dose-dependent suppression of total testosterone and sex hormone-binding globulin (SHBG) — providing the most important human pharmacokinetic dataset available for any SARM.
In preclinical models, LGD-4033 shows strong anabolic activity in muscle and bone with lower androgenic impact in prostate tissue compared to testosterone equivalents. Its hepatotoxicity signal in the observational literature is lower than RAD-140.
Ostarine (MK-2866) — Research Profile
- Classification: Non-steroidal SARM
- Developer: GTx, Inc.
- AR binding affinity: Ki ~3.8 nM
- Anabolic:androgenic ratio: ~3:1 in preclinical models
Ostarine has the largest body of published human clinical data of any SARM, having progressed furthest through regulatory trial stages. Multiple Phase II trials have examined its effects on lean mass and physical function in sarcopenia, cancer cachexia, and musculoskeletal disease populations. It is the mildest of the three compounds by anabolic potency but the most studied and best characterised for safety in humans.
Research applications include muscle wasting models, bone density studies, and metabolic health markers where a well-characterised, lower-potency AR modulator is appropriate.
Research Comparison Table
| Parameter | RAD-140 | LGD-4033 | Ostarine (MK-2866) |
|---|---|---|---|
| AR binding affinity (Ki) | ~7 nM | ~1 nM | ~3.8 nM |
| Anabolic:androgenic ratio | ~90:1 | ~10:1 | ~3:1 |
| Potency rank | Highest | Middle | Mildest |
| Human clinical data | Limited | Phase I complete | Phase II complete |
| Lean mass signal | Strong | Strong | Moderate |
| Hepatotoxicity signal | Case reports | Low | Low |
| Primary research application | High-potency AR binding, neuroprotection models | Lean mass / bone / PK reference | Broadest human dataset; muscle wasting models |
Selectivity Mechanism: What Makes a SARM “Selective”?
Androgen receptor selectivity arises from the peptide’s ability to induce specific three-dimensional conformational changes in the AR ligand-binding domain that differ from those induced by testosterone or dihydrotestosterone (DHT). These conformation-dependent changes alter which co-activator and co-repressor proteins bind to the AR-ligand complex in different cell types. In skeletal muscle and bone cells, the SARM-induced conformation may favour anabolic gene transcription; in prostate or skin cells, the same compound may recruit different co-regulators and produce limited or no androgenic transcription. The precise co-regulator expression profile of each tissue type determines the apparent “selectivity” observed in research models.
Sourcing SARMs for Research in Australia
PureRawz Australia supplies RAD-140, LGD-4033, Ostarine, and other SARMs as COA-verified research compounds at ≥99% purity, available in multiple research forms (liquid, powder, capsules):
Browse SARMs research compounds →
Frequently Asked Questions
What is the most potent SARM in research — RAD-140 or LGD-4033?
In preclinical models, RAD-140 demonstrates the highest anabolic:androgenic ratio (~90:1 vs LGD-4033’s ~10:1) and strongest lean tissue anabolic signal per milligram. However, LGD-4033 has more robust human Phase I pharmacokinetic data and a lower observed hepatotoxicity signal in the case report literature, making it a more characterised research reference compound.
Which SARM has the most human clinical research data?
Ostarine (MK-2866) has the most extensive human clinical dataset, having progressed through multiple Phase II trials in populations including cancer cachexia and sarcopenia. LGD-4033 has completed Phase I in healthy male volunteers. RAD-140 has the least human data of the three.
Are SARMs legal to purchase for research in Australia?
SARMs are not scheduled under the TGA Poisons Standard for general distribution and are legally available for laboratory and research purposes in Australia. They are prohibited in sport under WADA regulations. Researchers should confirm institutional compliance requirements before use in any study context.
How do SARMs differ from anabolic steroids in research models?
Anabolic-androgenic steroids bind to the androgen receptor with relatively uniform activity across tissues, driving both anabolic and androgenic effects. SARMs are designed to produce tissue-selective AR modulation through conformation-dependent co-regulator recruitment — seeking anabolic effects in muscle and bone while limiting androgenic signalling in other AR-expressing tissues. The degree of achieved selectivity varies by compound and research model.
How should SARMs be stored for research?
Most research SARMs in powder form should be stored at −20°C, protected from light and moisture. Liquid formulations should be refrigerated at 2–8°C and used within the supplier’s stated stability period. Always check the batch COA for compound-specific storage specifications.
For laboratory and research use only. Not for human or veterinary consumption. Nothing in this article constitutes medical advice.
