RAD-140 (Testolone)

Quick Facts

Introduction

RAD-140 — commonly called Testolone — is a non-steroidal selective androgen-receptor modulator (SARM). Like MK-2866, it is a small molecule rather than a peptide, but it is catalogued alongside the peptides in this library because it shares their research focus on muscle and body-composition endpoints. It is studied as one of the more potent members of the SARM class.

The premise of the SARM class is tissue selectivity: producing the anabolic effects of androgen-receptor (AR) activation in muscle and bone while limiting the activity in prostate and other androgenic tissues that characterizes traditional steroids. RAD-140 emerged from medicinal-chemistry programs that explored this premise and additionally examined the receptor's role in neural tissue, giving it a research profile that spans anabolic and neuroprotective questions. It is frequently compared with the milder SARM MK-2866 and with mechanistically distinct muscle-research compounds such as Follistatin-344 and MK-677.

This profile covers what RAD-140 is, its non-steroidal chemistry, its tissue-selective androgen-receptor mechanism, the lean-mass and neuroprotection research it appears in, and how it compares with related compounds. Related entries are catalogued in the peptide database.

What is RAD-140?

RAD-140 is a non-steroidal, orally active SARM developed in pharmaceutical research programs that explored selective androgen-receptor activation. Chemically it is unrelated to testosterone and the steroidal anabolics: it lacks the steroid ring system entirely and is instead a synthetic small molecule designed to bind the androgen receptor with high affinity and a tissue-selective activity profile.

A defining theme in the RAD-140 literature is potency. Compared with earlier SARMs, it is reported to combine strong anabolic activity in muscle with relatively low activity in androgenic tissues, an anabolic-to-androgenic separation that is the central reason it became a focus of research. As with other non-steroidal compounds, it is not a substrate for the steroidal conversion enzymes that generate estrogenic metabolites.

Because it is a small molecule and not a peptide, RAD-140 is administered and handled differently from the injectable peptides in this library — it is orally bioavailable and is typically worked with as a solution in an organic co-solvent rather than reconstituted in water.

Molecular and structural characteristics

RAD-140 is a small organic molecule built around a substituted aromatic scaffold incorporating a chloro-substituted pyrrolidine-carbonitrile system. This non-steroidal structure is the feature that most clearly separates it from testosterone-derived anabolics and underlies its distinct receptor-conformation and metabolic behavior.

Unlike the folded proteins and linear peptides elsewhere in this library, RAD-140 has no disulfide bonds or tertiary structure to preserve. Its handling considerations center on solubility and chemical stability rather than denaturation, since it is poorly water-soluble and is generally dissolved in a suitable organic co-solvent.

Mechanism of action

RAD-140 binds the androgen receptor, a ligand-activated nuclear transcription factor. On binding, the receptor changes conformation, translocates to the nucleus, and regulates transcription of androgen-responsive genes — the same fundamental pathway through which testosterone acts, but reached via a different, high-affinity ligand chemistry.

As with the SARM class generally, the functional outcome depends on tissue selectivity: the co-regulatory proteins recruited to the activated receptor differ by cell type and by the precise conformation the ligand induces. RAD-140 is studied because it is reported to drive strong anabolic gene programs in muscle and bone while producing comparatively weak activation in tissues such as the prostate, yielding a favorable anabolic-to-androgenic ratio in preclinical models.

A distinctive strand of RAD-140 research concerns the nervous system. The androgen receptor is expressed in neurons, and studies have examined RAD-140 for AR-mediated neuroprotective signaling — for example in models of neuronal injury — making it unusual among SARMs for the breadth of pathways explored. Because it is not a steroid, it is also not converted by aromatase or 5α-reductase, and like all AR agonists it is studied for effects on the body's own endocrine feedback.

• Binds the androgen receptor as a ligand-activated transcription factor.
• Induces conformations favoring anabolic gene programs in muscle and bone.
• Reported high anabolic-to-androgenic selectivity in preclinical models.
• Studied for AR-mediated neuroprotective signaling in neural tissue.

Lean-mass and body-composition research

The leading research context for RAD-140 is anabolic activity in skeletal muscle. In preclinical models it has been associated with increases in lean mass, and its reported potency relative to earlier SARMs is the primary reason it became a focus of muscle-research interest. Investigators frame it as a tool for testing how far the anabolic effects of androgen-receptor activation can be separated from androgenic activity in non-target tissues.

This selectivity premise is the unifying idea across SARM research: achieving androgen-receptor-driven anabolic effects in muscle while minimizing the prostate and other androgenic activity associated with steroids. RAD-140 is studied as a comparatively potent test of that premise rather than as an established therapy.

Within this library, RAD-140 sits alongside compounds that pursue muscle endpoints through different routes — the milder SARM MK-2866, the myostatin antagonist Follistatin-344, and the growth-hormone secretagogue MK-677 — making it a useful comparison point across anabolic-research strategies.

Neuroprotection and androgen-signaling research

Beyond muscle, RAD-140 has been examined for neuroprotective properties tied to androgen-receptor signaling in neurons. Preclinical work has explored whether AR activation by a selective ligand can support neuronal survival in injury and degeneration models, an avenue that distinguishes RAD-140 from SARMs studied purely for anabolic endpoints.

Androgen-receptor expression in certain hormone-responsive tissues has also placed RAD-140 in research examining AR-pathway modulation more broadly. These lines of investigation remain preclinical, and researchers treat the neuroprotective findings as early-stage observations rather than demonstrated effects.

Comparison: RAD-140 vs MK-2866 vs MK-677

RAD-140 is most often compared with MK-2866 (Ostarine), a milder SARM, and with MK-677 (Ibutamoren), which is not a SARM but a growth-hormone secretagogue commonly grouped with these compounds in muscle research. The three share research interest but act through distinct mechanisms.

The comparison shows that MK-2866 shares RAD-140's androgen-receptor mechanism at a milder reported profile, while MK-677 reaches muscle endpoints through the growth-hormone axis. Full entries for each are in the peptide database.

Half-life and pharmacokinetic considerations

RAD-140 is orally active, a consequence of its small non-steroidal structure, and is reported to have a half-life supporting once-daily dosing intervals in research settings — considerably longer than the minutes-to-hours typical of many peptides. This durability is part of what made it attractive as an oral research compound rather than an injectable.

Because it engages the androgen receptor centrally and with relatively high potency, the degree and duration of receptor engagement — and its potential to influence the body's own hormonal feedback — are primary interpretive variables researchers weigh when reading study outcomes.

Reconstitution and handling considerations

Unlike the lyophilized peptides in this library, RAD-140 is a small molecule that is poorly water-soluble, so it is generally prepared as a solution in a suitable organic co-solvent rather than reconstituted with bacteriostatic water. The aim is a clear, homogeneous solution at a known concentration for reproducible research use.

For peptides that are reconstituted in water, the reconstitution calculator and reconstitution guide describe the general method; RAD-140's handling differs because of its small-molecule chemistry.

• Prepare in a suitable organic co-solvent; not freely water-soluble.
• Confirm a clear, homogeneous solution before use.
• Record the precise working concentration for reproducibility.
• Protect from light and excess warmth.

Storage considerations

As a small molecule, RAD-140 is comparatively stable but is still kept cool, dry, and protected from light for long-term holding. Prepared solutions are refrigerated and protected from light, with concentration and preparation date recorded to support reproducible research.

Research limitations

RAD-140 is an investigational compound that has not been approved as a therapy, and much of its data come from preclinical models rather than large controlled human studies. Its relatively high potency makes central androgen-receptor engagement and endocrine-feedback considerations especially important, and it is a frequent subject of sports anti-doping attention. Reported effects are dose-, duration-, and model-dependent, and it is described here strictly for research reference.

• Most anabolic and neuroprotective data are preclinical.
• High potency makes central AR engagement and feedback important.
• Complete tissue selectivity remains a research premise, not a fact.
• Not an approved therapy; described solely for research reference.

Frequently Asked Questions

Related Research Profiles

References

1. Miller CP, et al. Design, Synthesis, and Preclinical Characterization of the Selective Androgen Receptor Modulator (SARM) RAD140. ACS Med Chem Lett. 2011.Source
2. Jayaraman A, et al. Selective androgen receptor modulator RAD140 is neuroprotective in cultured neurons and kainate-lesioned male rats. Endocrinology. 2014.Source
3. Bhasin S, Jasuja R. Selective androgen receptor modulators as function promoting therapies. Curr Opin Clin Nutr Metab Care. 2009.Source