RAD-140 (Testolone)

Overview

RAD-140, also known as Testolone, is a non-steroidal selective androgen receptor modulator (SARM) developed by Radius Health, Inc. The compound was first described in a 2010 publication by Miller et al. in the journal Biochemical and Biophysical Research Communications, where it was characterized as a potent, orally bioavailable SARM with tissue-selective androgenic activity. The development program was initiated with the goal of creating a compound that could deliver the anabolic benefits of testosterone in muscle and bone while avoiding the androgenic side effects that limit the therapeutic utility of traditional androgens.

In preclinical studies, RAD-140 demonstrated an anabolic-to-androgenic ratio that substantially favored muscle tissue over prostate tissue, a finding that generated considerable excitement in the pharmaceutical and research communities. The compound also showed neuroprotective properties in cellular models, raising the possibility that it could serve as a therapeutic candidate for neurodegenerative conditions. While RAD-140 has advanced into early-phase clinical trials, it remains an investigational compound with no approved medical indications.

Mechanism of Action

RAD-140 binds to the androgen receptor (AR) with high affinity, competing with endogenous androgens like testosterone and dihydrotestosterone (DHT) for receptor occupancy. Upon binding, the RAD-140/AR complex undergoes a conformational change that is distinct from the conformational change induced by steroidal androgens. This difference in receptor conformation is central to the compound’s tissue selectivity.

The tissue-selective activity of SARMs is thought to arise from differential recruitment of coactivator and corepressor proteins in different tissue types. In skeletal muscle, RAD-140 activates the AR in a manner that promotes anabolic gene transcription, including genes involved in protein synthesis, satellite cell activation, and nitrogen retention. In the prostate and other androgen-sensitive tissues, the compound appears to recruit a different set of cofactors that limit its transcriptional activity, resulting in reduced androgenic stimulation.

Preclinical data from the Radius Health program showed that RAD-140 increased lean body mass in a dose-dependent manner in castrated rats without producing significant prostate growth. The compound also demonstrated activity in levator ani muscle bioassays that was comparable to testosterone propionate, while prostate stimulation was a fraction of what testosterone produced. This favorable separation of anabolic and androgenic effects defines the compound’s pharmacological identity.

RAD-140 also appears to suppress the HPG axis in a dose-dependent manner, reducing endogenous testosterone production through negative feedback at the hypothalamus and pituitary. This effect is consistent with other SARMs and represents a significant consideration for research protocols.

Research Summary

The foundational preclinical work by Miller et al. established RAD-140 as one of the most potent SARMs characterized to date, with an effective concentration for half-maximal AR activation (EC50) in the low nanomolar range. Oral bioavailability in rats was approximately 27%, and the compound showed a pharmacokinetic profile compatible with once-daily dosing.

Neuroprotective studies conducted at the University of Southern California demonstrated that RAD-140 protected cultured hippocampal neurons against cell death induced by apoptotic insults, with efficacy comparable to testosterone. The researchers also showed that RAD-140 reduced brain cell death in a kainate excitotoxicity model in vivo. These findings suggested potential applications in Alzheimer’s disease and other neurodegenerative conditions, though this line of research remains in early stages.

Radius Health advanced RAD-140 into a phase I clinical trial in postmenopausal women with hormone receptor-positive breast cancer (NCT03088527). Preliminary data presented at the 2020 San Antonio Breast Cancer Symposium showed that the compound was generally well tolerated, with some patients showing disease stabilization. The rationale for testing in breast cancer relates to evidence that AR activation can inhibit estrogen receptor signaling in certain breast cancer subtypes.

In the research community, RAD-140 has become one of the most widely studied SARMs, with reports from users and observational data suggesting significant increases in lean mass and strength at doses ranging from 10 to 30 mg daily over eight-to-twelve-week cycles. However, these reports lack the rigor of controlled clinical trials and must be interpreted with caution.

Dosing in Published Research

RAD-140 (testolone) is a selective androgen receptor modulator. It is not an approved medicine and has no labeled dose. Its only completed human study is a Phase 1 dose-escalation trial in postmenopausal women with hormone-receptor-positive breast cancer; no controlled trial has established a dose in healthy adults, and no long-term human safety data exist. Specific RAD-140 figures circulating in forums or vendor material are not derived from such research and are therefore not reported here.

Safety and Side Effects

The safety profile of RAD-140 is incompletely characterized due to limited clinical trial data. Preclinical toxicology studies showed no evidence of hepatotoxicity, genotoxicity, or significant organ damage at doses within the expected therapeutic range. However, post-marketing surveillance through case reports and adverse event databases has identified instances of drug-induced liver injury (DILI) associated with products marketed as containing RAD-140, though product adulteration and contamination complicate the interpretation of these reports.

Suppression of endogenous testosterone is a consistent finding across all reported experiences with RAD-140. Users have reported reductions in total testosterone, LH, FSH, and sex hormone-binding globulin (SHBG) during and after use. The degree of suppression appears dose- and duration-dependent. Recovery of endogenous hormone production after discontinuation has been reported to take four to eight weeks in most cases, though individual variation is considerable.

Other reported adverse effects include headache, nausea, aggression, and hair shedding. Effects on lipid profiles, including reductions in HDL cholesterol, have been observed in user-reported bloodwork, consistent with the known effects of androgens and other SARMs on hepatic lipase activity. Long-term safety data, including effects on cardiovascular health, liver function, and cancer risk, remain unavailable.

Current Research Status

RAD-140 remains an investigational compound. It has not been approved by the FDA or any other regulatory agency for medical use. It is prohibited by the World Anti-Doping Agency (WADA) in competitive athletics. Clinical development continues through the Radius Health breast cancer program, while academic researchers continue to investigate its neuroprotective and musculoskeletal effects. The compound is available through research chemical suppliers but is not approved for human consumption. Regulatory scrutiny of SARM sales has increased in recent years, with the FDA issuing warning letters to companies marketing SARMs as dietary supplements.

Further reading: RAD-140 vs LGD-4033: Comparing Two Researched SARMs compares the research on these two selective androgen receptor modulators.

Frequently Asked Questions