RAD-140 (Testolone) Research Guide: 2026 Clinical Data, Pharmacokinetics & RUO Applications

RAD-140 (INN: Vosilasarm), commonly known as Testolone, is an investigational non-steroidal Selective Androgen Receptor Modulator (SARM) originally developed by Radius Health. It selectively binds androgen receptors in muscle and bone tissue without converting to estrogen via aromatization or to DHT via 5α-reduction, achieving anabolic effects without typical steroidal side effects. RAD-140 is strictly not for human consumption and is available for Research Use Only (RUO).

Chemical identity: PubChem CID 44200882 | IUPAC: 2-chloro-4-[(1R,2S)-1-[5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl]-2-hydroxypropyl]aniline | Molecular formula: C₂₀H₁₆ClN₅O₂ | MW: 393.83 g/mol | CAS: 1182367-47-0. Developed circa 2010 (Miller CP et al., ACS Med Chem Lett) as a non-steroidal tissue-selective androgen receptor modulator with favorable oral pharmacokinetics and high anabolic-to-androgenic ratio in preclinical models.

Now advanced by Ellipses Pharmaceuticals under the designation EP0062, Vosilasarm is the subject of active Phase I/II clinical investigations. Its unique combination of a long 44.7-hour elimination half-life, documented neuroprotective properties via MAPK pathway activation, and ongoing oncology trials (NCT05573126) makes it one of the most scientifically distinct SARMs in the current research landscape.

At Loti Labs, we recognize that the integrity of independent research depends entirely on the purity and transparency of the compounds used. As a premier provider of research-use-only (RUO) peptides and SARMs, we provide comprehensive analytical data, including COA transparency and ICP-MS testing, to ensure that laboratory models yield accurate, reproducible results. This guide serves as a technical compendium for researchers, detailing the 2026 clinical landscape, updated pharmacokinetic profiles, and the biochemical mechanisms defining RAD-140.

Disclaimer: RAD-140 (Testolone) is strictly for Research Use Only (RUO). It is not for human consumption, clinical use, or diagnostic purposes. Laboratory safety protocols must be strictly followed when handling this compound.

What Is RAD-140 (Vosilasarm)?

RAD-140 is a second-generation non-steroidal selective androgen receptor modulator (SARM). It was engineered to overcome the limitations of traditional anabolic-androgenic steroids (AAS), specifically the lack of tissue selectivity which often leads to adverse effects on the prostate, cardiovascular system, and skin. As of 2026, RAD-140 is recognized under the INN Vosilasarm, reflecting its progression through clinical trial phases for various therapeutic indications.

Chemical Structure and Radius Health Development History

The chemical identity of RAD-140 is defined by the IUPAC name: 2-chloro-4-[(1R,2S)-1-[5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl]-2-hydroxypropyl]aniline. Its molecular formula is C20H16ClN5O2, with a molecular weight (MW) of 393.83 g/mol and a CAS registry number of 1182367-47-0. Unlike many first-generation SARMs that utilized a propionamide structure, RAD-140 features a unique 1,3,4-oxadiazole ring, which contributes to its high binding affinity and stability.

The compound was initially discovered and developed by Radius Health, Inc. in the late 2000s. The goal was to create a compound that provided the anabolic benefits of testosterone in skeletal muscle and bone while acting as an antagonist or weak agonist in androgen-sensitive tissues like the prostate. Following successful preclinical models, the development rights for certain indications were later advanced by Ellipses Pharmaceuticals, where it was designated as EP0062 for ongoing oncology research.

SARM Classification and Tissue Selectivity

RAD-140 is classified as a SARM due to its ability to differentiate between anabolic and androgenic activities. In laboratory models, the selectivity index of RAD-140 is notably high. Research indicates that RAD-140 can stimulate muscle growth at a fraction of the dose required to stimulate the prostate. This selectivity is mediated through tissue-specific coregulator recruitment. When RAD-140 binds to the androgen receptor (AR), the resulting conformational change favors the recruitment of co-activators in myogenic (muscle-forming) cells, while potentially recruiting co-repressors or failing to recruit necessary co-activators in the prostate and sebaceous glands.

Mechanism of Action in Laboratory Models

The primary mechanism of RAD-140 involves the high-affinity, non-covalent binding to the ligand-binding domain (LBD) of the androgen receptor. Once bound, the AR-SARM complex translocates into the cell nucleus, where it binds to androgen response elements (AREs) on the DNA, initiating the transcription of genes associated with protein synthesis and cellular metabolism.

Androgen Receptor Binding Affinity (Ki ~7nM)

Binding affinity is a critical metric for determining the potency of a SARM. RAD-140 exhibits a remarkably high binding affinity for the androgen receptor, with a Ki (inhibition constant) of approximately 7nM. This indicates a strong and stable interaction with the receptor. For comparison, while LGD-4033 (Ligandrol) has an even higher affinity (Ki ~1nM), RAD-140 is often noted for its greater selectivity index in specific preclinical assays.

A critical distinction separating RAD-140 from classical androgens: it undergoes neither aromatization (conversion to estrogen via aromatase) nor 5α-reduction (conversion to dihydrotestosterone via 5α-reductase). This prevents the estrogenic and androgenic side effects associated with steroidal compounds in research models. The anabolic-to-androgenic ratio of RAD-140, measured via the levator ani muscle model — a standard preclinical benchmark comparing anabolic (levator ani) to androgenic (prostate/seminal vesicle) tissue response — exceeds 90:1, demonstrating its exceptional prostate-sparing selectivity index relative to testosterone.

The 7nM affinity ensures that RAD-140 can effectively compete with endogenous androgens, such as testosterone and dihydrotestosterone (DHT), for receptor occupancy. This is particularly relevant in research models where researchers aim to study the effects of AR modulation in the absence or presence of endogenous hormones.

Endocrine Feedback Loop and HPG Axis Modulation

Despite its tissue selectivity, RAD-140 is recognized by the hypothalamus and pituitary gland as an androgenic signal. In laboratory settings, administration of RAD-140 has been shown to modulate the Hypothalamic-Pituitary-Gonadal (HPG) axis. In male models, this typically results in a dose-dependent suppression of Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH), which subsequently reduces endogenous testosterone production.

This suppression is a critical area of study for researchers examining the long-term endocrine impact of SARMs. Investigating the degree of HPG axis suppression allows for a better understanding of the compound’s “androgenic footprint” versus its anabolic potential. It also necessitates the consideration of recovery protocols in animal models to restore homeostasis following the cessation of the study period.

Pharmacokinetics: The RAD-140 Half-Life Explained

Understanding the pharmacokinetics (PK) of RAD-140 is essential for designing accurate research protocols. For many years, anecdotal reports suggested a half-life of 20 hours. However, modern clinical data has corrected this misconception, significantly altering the dosing frequency considerations for laboratory investigation.

Phase 1 Clinical Data — The 44.7-Hour Half-Life

Recent Phase I clinical data, particularly those emerging from the development of EP0062 (Vosilasarm), have clarified the elimination half-life of RAD-140. In human clinical trials, RAD-140 demonstrated a mean terminal half-life of approximately 44.7 hours. This prolonged half-life means that the compound remains active in the system for much longer than previously thought, and steady-state plasma concentrations are reached only after several days of consistent administration.

This data is pivotal for researchers. A 44.7-hour half-life suggests that once-daily or even every-other-day administration in certain models may be sufficient to maintain therapeutic levels, reducing the volatility of plasma concentrations and the potential for “peaks and troughs” that could interfere with data collection.

Bioavailability, Tmax, and Dosing Implications for Research

RAD-140 exhibits high oral bioavailability, estimated between 70% and 80% in most mammal models. This high bioavailability makes it an ideal candidate for oral administration in research protocols, avoiding the complications associated with parenteral (injection) routes. The time to reach peak plasma concentration (Tmax) is typically observed between 1 and 4 hours post-administration.

For research purposes, the dosing implications are significant. Because of the 44.7-hour half-life, the cumulative effect of the compound must be accounted for. If a research model calls for a specific steady-state concentration, the initial “loading” period must be calculated based on this extended half-life. Failure to account for the actual half-life can lead to unintended accumulation and potential toxicity in test subjects.

Principal Areas of Scientific Investigation

RAD-140 is being investigated across several distinct therapeutic domains. Its unique profile as an AR agonist that can cross the blood-brain barrier makes it a versatile tool for various pathological models.

Skeletal Muscle Hypertrophy and Sarcopenia Research

The most common application of RAD-140 in research is the study of skeletal muscle hypertrophy and the mitigation of sarcopenia (age-related muscle wasting). In preclinical trials, RAD-140 has demonstrated the ability to increase lean body mass (LBM) without the significant increases in fat mass often seen with other anabolic agents. Researchers use RAD-140 to study the activation of satellite cells, the rate of myofibrillar protein synthesis, and the modulation of myostatin levels in murine and primate models.

Beyond sarcopenia (age-related muscle loss), RAD-140 has been investigated as a potential research tool in cachexia models — the severe muscle and weight loss syndrome associated with chronic illness, cancer, and advanced metabolic disease. Cachexia was among the original target applications identified during Radius Health’s compound development program. RAD-140’s tissue-selective AR agonism without HPG axis disruption (relative to testosterone) makes it a mechanistically relevant candidate in preclinical cachexia model research.

Bone Mineral Density and Osteogenesis Studies

Androgen receptors play a vital role in bone health by stimulating osteoblast activity and inhibiting osteoclast-mediated bone resorption. RAD-140 is a subject of research regarding its potential to increase Bone Mineral Density (BMD). This makes it a compound of interest for investigators studying osteoporosis and recovery from bone fractures. Laboratory models have shown that RAD-140 can increase bone strength and mineral content, suggesting a protective effect against skeletal degradation.

Neuroprotection via MAPK Pathway: Kainate-Lesioned Models

One of the most intriguing aspects of RAD-140 research is its potential neuroprotective properties. A landmark study by Jayaraman et al. (2014) demonstrated that RAD-140 could protect cultured hippocampal neurons against excitotoxicity induced by kainate. This protection is mediated through the MAPK (Mitogen-Activated Protein Kinase) pathway.

In kainate-lesioned models, RAD-140 was found to be as effective as testosterone in reducing cell death, but without the systemic androgenic side effects. This research suggests that SARMs like RAD-140 could eventually be investigated for neurodegenerative conditions such as Alzheimer’s disease, where androgen signaling is known to be protective but traditional testosterone therapy is limited by prostate risks.

ER+/HER2- Metastatic Breast Cancer: Phase I Clinical Trials (NCT03088527)

Perhaps the most advanced clinical application of RAD-140 is in oncology. Radius Health and subsequently Ellipses Pharmaceuticals have investigated RAD-140 (Vosilasarm) for the treatment of ER+/HER2- metastatic breast cancer. In these cancers, the androgen receptor often acts as a tumor suppressor.

The NCT03088527 clinical trial explored the safety and efficacy of RAD-140 in postmenopausal women with advanced breast cancer. The rationale is that RAD-140 can activate the AR in breast tissue, which inhibits the growth of estrogen-receptor-positive cancer cells. Research in this area is ongoing, with investigators looking at how EP0062 can be combined with other therapies, such as CDK4/6 inhibitors, to overcome endocrine resistance.

Phase 1/2 Combination Therapy Trial: NCT05573126

Building on the foundational Phase I oncology data, an active Phase 1/2 clinical trial (NCT05573126) is evaluating Vosilasarm (EP0062) in combination with targeted therapies — including CDK4/6 inhibitors — for advanced AR+/ER+/HER2- breast cancer. This combination approach targets both androgen receptor and estrogen receptor-driven tumor proliferation simultaneously. The trial, running through 2025–2026 under Ellipses Pharmaceuticals sponsorship, represents the most clinically advanced investigation of RAD-140 to date and may establish Vosilasarm as a precision oncology compound with a defined combination therapy regimen.

Comparative Analysis: RAD-140 vs. LGD-4033 (Ligandrol)

Researchers often compare RAD-140 with LGD-4033 (Ligandrol), as they are the two most prominent SARMs in contemporary research. While both are potent AR ligands, their profiles differ in ways that may influence study design.

Receptor Affinity and Anabolic Potency

As noted, LGD-4033 has a higher binding affinity (Ki ~1nM) compared to RAD-140 (Ki ~7nM). In many models, LGD-4033 is considered more potent on a milligram-for-milligram basis regarding weight gain and overall mass. However, RAD-140 is frequently described as providing “drier” gains in research subjects, likely due to its unique interaction with the AR and a potential lack of any estrogenic activity or mineralocorticoid receptor cross-reactivity.

Half-Life and Pharmacokinetic Differences

The pharmacokinetic profiles are distinct. LGD-4033 has a half-life of approximately 24–36 hours, whereas the 44.7-hour half-life of RAD-140 is significantly longer. This necessitates different clearance times and washout periods in comparative studies. For a detailed breakdown of LGD-4033’s PK data, researchers should refer to our dedicated LGD-4033 research guide.

HPG Axis Suppression Profile Comparison

Both compounds induce HPG axis suppression. Preliminary comparative data suggests that RAD-140 may be slightly more suppressive to total testosterone in some models, possibly due to its longer half-life and higher cumulative exposure. However, RAD-140 consistently shows a better prostate-to-muscle selectivity ratio than LGD-4033 in primate models, making it a preferred choice for studies where minimizing androgenic activity in the prostate is a priority.

Safety Profile and Preclinical Observations

While RAD-140 is widely used in laboratory settings, its safety profile in research models is characterized by several specific signals that investigators must monitor.

Testosterone and Hormonal Suppression

The primary side effect observed in research models is the suppression of endogenous testosterone. This is not “shutdown” in the same sense as seen with certain heavy steroids, but a significant reduction in natural hormone levels is expected. In animal models, this can lead to changes in libido (inferred via behavior) and reductions in the weight of androgen-dependent organs like the seminal vesicles if doses are sufficiently high.

Hepatotoxicity Signals and DILI Reports

In 2025 and 2026, an increasing number of case reports and preclinical studies have highlighted potential hepatotoxicity associated with RAD-140. While RAD-140 is not a 17-alpha-alkylated steroid, it has been linked to signals of Drug-Induced Liver Injury (DILI), specifically cholestatic liver injury. Researchers should monitor liver enzymes (ALT, AST, ALP) and bilirubin in their models to detect early signs of hepatic stress. This risk is often dose-dependent and may be exacerbated by prolonged exposure periods.

A critical April 2026 case report documented severe arterial thrombosis in a subject co-administering RAD-140 with exogenous testosterone, resulting in hospitalization. This represents a serious cardiovascular signal warranting careful monitoring in in-vivo research protocols involving RAD-140 alongside other androgenic compounds. LiverTox registry entries (2025–2026) additionally document cholestatic hepatitis cases with elevated bilirubin in subjects using unverified RAD-140 sources — consistent with the DILI pattern observed across multiple SARMs. Research protocols must include baseline and periodic hepatic function panels (AST, ALT, bilirubin) and cardiovascular biomarker monitoring.

Additionally, acute myocarditis — inflammation of the heart muscle — has been documented in case reports linking RAD-140 to cardiac adverse events, particularly in subjects using supraphysiological doses from unverified sources. The Naranjo Adverse Drug Reaction Probability Scale, used in clinical pharmacovigilance to assess causality of drug-induced adverse events, has been applied in several SARM hepatotoxicity case reports and yields “probable” causality scores for RAD-140-associated DILI and cardiac events. Institutional research protocols must include cardiovascular biomarker panels (troponin, CRP) in addition to hepatic function monitoring.

Post-Cycle Therapy (PCT) Considerations in Research Models

In the context of laboratory research, “Post-Cycle Therapy” refers to the period following the administration of the SARM where researchers attempt to restore the test subject’s hormonal baseline. This often involves the use of Selective Estrogen Receptor Modulators (SERMs) or other agents to stimulate the HPG axis. Understanding the timeline for hormonal recovery is essential for studies looking at the long-term sustainability of the muscle mass gained during the research phase.

RAD-140 Regulatory Status 2026: FDA, WADA, and RUO Compliance

The regulatory landscape for RAD-140 remains stringent. As of 2026, the compound is not approved for human use by any global regulatory body.

FDA Investigational Drug Status (Vosilasarm/Ellipses Pharmaceuticals)

The U.S. Food and Drug Administration (FDA) currently classifies RAD-140 (Vosilasarm/EP0062) as an Investigational New Drug (IND). It remains in clinical trial phases and has not been granted marketing authorization. The FDA continues to issue warnings regarding the off-label use of SARMs, emphasizing that they are not dietary supplements and can only be legally sold as research chemicals.

In late 2025, the FDA issued Warning Letters to multiple SARM vendors including Titan SARMs LLC and Atomix LLC for marketing RAD-140 and other SARMs as dietary supplements or for human consumption — a direct violation of the FD&C Act. These enforcement actions reinforce that any commercial sale of RAD-140 for anything other than legitimate laboratory research constitutes a regulatory violation. Institutional purchasers should ensure all procurement is documented as Research Use Only (RUO) with appropriate institutional affiliation, and that no marketing language implies therapeutic or dietary use.

WADA 2026 Prohibited List S1.2

The World Anti-Doping Agency (WADA) maintains RAD-140 on the 2026 Prohibited List under section S1.2 (Other Anabolic Agents). In 2026, WADA updated its detection methods to include the identification of long-term glucuronide conjugates, extending the detection window for RAD-140 significantly. This is a critical consideration for researchers studying the compound’s metabolism and its presence in biological fluids.

Laboratory Testing and Purity Standards for RAD-140

Research-grade RAD-140 must be verified through third-party analytical testing before institutional use. Standard quality control protocols require:

• HPLC (High-Performance Liquid Chromatography): Confirms compound purity ≥98% by verifying the retention time and peak area of RAD-140 against certified reference standards.
• NMR Spectroscopy (Nuclear Magnetic Resonance): Validates molecular structure by confirming the ¹H and ¹³C spectral fingerprint matches the expected Vosilasarm structure.
• Mass Spectrometry (LC-MS/MS): Identifies and quantifies the compound at molecular weight 393.83 g/mol while detecting any synthetic impurities or degradation products.
• ICP-MS (Inductively Coupled Plasma Mass Spectrometry): Screens for heavy metal contamination per USP <232>/<233> guidelines.

A valid Certificate of Analysis (COA) from an accredited third-party laboratory is the minimum documentation standard for institutional research procurement. Research institutions should request batch-specific COAs and verify results independently before initiating any in-vivo or in-vitro protocols.

Handling, Storage, and Formulation for Laboratory Use

To ensure the stability and efficacy of RAD-140 in a laboratory setting, proper handling and storage are required. RAD-140 is typically supplied as a lyophilized powder or a solution in a solvent like DMSO or PEG-400.

• Storage: Lyophilized powder should be stored at -20°C for long-term stability. Once reconstituted, the solution should be kept at 4°C and used within a short timeframe (typically 30 days) to prevent degradation.
• Light Sensitivity: RAD-140 is sensitive to UV light. It should be stored in amber vials and kept in a dark environment.
• Formulation: For oral administration in models, RAD-140 is often dissolved in a lipid-based carrier. Proper homogenization is necessary to ensure consistent dosing. For further information on general compound preservation, see our peptide and SARM storage guide.

In addition to traditional SARMs, many researchers are now investigating the synergistic effects of metabolic regulators. For insights into the current legal and research status of other high-interest compounds, such as GLP-1 agonists, see our report on compounded semaglutide research.

Frequently Asked Questions About RAD-140

What is the International Nonproprietary Name (INN) for RAD-140?

The International Nonproprietary Name (INN) for RAD-140 is Vosilasarm. In clinical research and pharmaceutical development contexts, it is also identified by the developmental designation EP0062. Vosilasarm was originally developed by Radius Health and is currently advanced through Phase I/II clinical trials by Ellipses Pharmaceuticals as an investigational oncology compound.

What is the actual half-life of RAD-140 — and why is the 20-hour figure inaccurate?

Contrary to widely circulated internet claims of a 20-hour half-life, Phase I clinical pharmacokinetic data from the NCT03088527 trial establishes that the elimination half-life of RAD-140 (Vosilasarm) is approximately 44.7 to 60 hours following oral administration. This extended half-life is attributable to high protein binding and lipophilicity, allowing stable plasma concentrations with infrequent dosing intervals in research protocols.

What is the neuroprotective mechanism of RAD-140?

In preclinical models, RAD-140 activates the MAPK (mitogen-activated protein kinase) signaling pathway, providing neuroprotection against apoptotic insults including kainate-induced excitotoxicity in cultured hippocampal neurons. The foundational Jayaraman et al. 2014 study demonstrated that RAD-140 protected hippocampal neurons from kainate lesion-induced cell death, opening a research avenue into androgen receptor modulation for neurodegenerative disease models.

How does RAD-140 compare to LGD-4033 (Ligandrol) in research settings?

While both are highly selective SARMs, key distinctions include AR binding affinity (RAD-140 Ki ~7nM vs LGD-4033 Ki ~1nM), making LGD-4033 more potent per milligram for lean mass studies. RAD-140 features a longer elimination half-life (~44.7–60h vs LGD-4033’s 24–36h), a superior prostate-sparing anabolic-to-androgenic ratio (>90:1 via levator ani model), and unique neuroprotective and oncology applications not documented for LGD-4033.

What is the FDA status of RAD-140 in 2026?

RAD-140 (Vosilasarm) remains an Investigational New Drug (IND) under active clinical development by Ellipses Pharmaceuticals (NCT05573126). It is not approved by the FDA for human consumption, therapeutic use, or dietary supplementation. FDA Warning Letters issued in late 2025 targeted vendors including Titan SARMs LLC and Atomix LLC for marketing SARMs as dietary supplements — a FD&C Act violation regardless of RUO status.

Is RAD-140 banned by WADA?

Yes. RAD-140 (Vosilasarm) is listed on WADA’s 2026 Prohibited List under Class S1.2 (Other Anabolic Agents), banned both in-competition and out-of-competition in all sports. WADA-accredited laboratories detect RAD-140 via LC-MS/MS targeting glucuronide conjugate metabolites, with detection windows extended beyond previously reported timelines due to updated 2026 methodology.

Does RAD-140 suppress testosterone in research models?

Yes. RAD-140 induces dose-dependent suppression of the hypothalamic-pituitary-gonadal (HPG) axis in all tested research models, resulting in reductions in endogenous testosterone, LH, FSH, and SHBG. Post-Cycle Therapy (PCT) using SERMs such as enclomiphene or tamoxifen is employed in in-vivo research protocols to facilitate HPG axis recovery following compound cessation.

What liver and cardiovascular risks are associated with RAD-140?

Drug-Induced Liver Injury (DILI) including cholestatic hepatitis has been documented in case reports involving off-label RAD-140 use from unverified sources. An April 2026 case report identified severe arterial thrombosis in a subject co-administering RAD-140 with exogenous testosterone. LiverTox registry entries (2025–2026) confirm elevated bilirubin and AST/ALT patterns consistent with SARM-induced hepatotoxicity. Research protocols should include hepatic and cardiovascular biomarker monitoring.

Does RAD-140 convert to estrogen or DHT?

No. As a non-steroidal compound, RAD-140 does not undergo aromatization (conversion to estrogen via aromatase) or 5α-reduction (conversion to dihydrotestosterone via 5α-reductase). This pharmacological property prevents the estrogenic and androgenic adverse effects associated with classical steroidal anabolic compounds, contributing to RAD-140’s distinct tissue-selectivity profile in research models.

Is RAD-140 legal for research procurement?

RAD-140 is legal to acquire and use strictly for laboratory and in vitro/in vivo research applications in jurisdictions without explicit prohibition. It is not a dietary supplement and may not be marketed for human consumption. Research procurement requires institutional affiliation documentation and must comply with applicable federal guidelines. FDA Warning Letters and WADA enforcement actions in 2025–2026 underscore the strict RUO-only framework governing this compound.

At Loti Labs, we remain dedicated to providing researchers with the highest quality RAD-140 for their investigative needs. Our commitment to purity and clinical transparency ensures that your laboratory data remains the focal point of your scientific contributions.