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LGD-3303 is a non-steroidal selective androgen receptor modulator (SARM) that stands out for its pronounced effects on bone as well as muscle. In rodent studies it raised bone mineral density, stimulated new bone formation, and increased muscle mass while keeping prostate stimulation low, and it even added to the benefit of a standard bone drug. Orally active and strongly tissue-selective, LGD-3303 has a distinctive physique-and-bone profile that keeps it firmly on the radar of SARM research.
- Builds lean muscle effectively
- Standout bone density and new bone formation
- Prostate sparing in animal research
- Orally active and strongly tissue selective
- Stacks well with standard bone drugs
- A physique and bone profile all its own
- HDL cholesterol may be reduced
- A mild rise in liver enzymes is possible
Overview
LGD-3303 is an orally bioavailable, non-steroidal selective androgen receptor modulator (SARM) developed by Ligand Pharmaceuticals, with the chemical identity 9-chloro-2-ethyl-1-methyl-3-(2,2,2-trifluoroethyl)-3H-pyrrolo[3,2-f]quinolin-7(6H)-one [1]. It belongs to the same tissue-selective androgen class as other SARMs but is particularly noted in the literature for its activity on the skeleton [2][4].
Preclinical characterization showed that LGD-3303 behaves as a potent agonist on muscle while acting only as a partial agonist on the prostate; in castrated-rat studies it increased the weight of the levator ani muscle above intact levels yet never drove ventral prostate weight above roughly half of normal, even at high exposures [1]. In female rat models of bone loss, it raised both cortical and cancellous bone mineral density and stimulated new bone formation on the periosteal surface, and combination treatment with the bisphosphonate alendronate produced additive skeletal benefit beyond either agent alone [2]. Studies also documented effects on androgen-sensitive behavior in rodents [3].
As with other members of its class, LGD-3303 has not been approved as a medicine and is used as a research compound; the strongest published evidence is preclinical, and no controlled human safety data are available. SARMs are prohibited in competitive sport and are widely sold as unregulated research chemicals [4]. The combination of substantial anabolic activity in muscle and bone with comparatively light prostate stimulation, plus oral dosing, is what gives LGD-3303 its notable research profile [1][2].
- In osteopenic rats, LGD-3303 combined with the bone drug alendronate produced added skeletal benefit beyond either agent alone, because one builds bone while the other blocks its breakdown.
- Even at high doses that maximized muscle growth, LGD-3303 never pushed prostate weight above roughly half of the normal intact level.
- Its selectivity comes from how it engages the androgen receptor rather than from being kept out of the prostate; tissue concentrations there were actually higher than in muscle.
Mechanism
LGD-3303 is a non-steroidal partial of the [1]. In common with the SARM class, it binds the same receptor as testosterone, but the way it occupies the -binding pocket alters which genes are switched on in which tissue, yielding strong anabolic signaling in muscle and bone alongside only weak partial- activity in the prostate; this is why prostate weight remained low even at doses that maximized the muscle response [1][4].
In bone, LGD-3303 does more than preserve mass: it stimulates periosteal bone formation, raising cortical and cancellous density, and its skeletal action is additive to that of a bisphosphonate rather than redundant with it, because the two work through different mechanisms, one anabolic and one antiresorptive [2]. This additivity is a meaningful pharmacological point, since combining bone therapies does not always yield extra benefit. On muscle, the compound increases lean mass through androgen-receptor-mediated anabolic signaling [1][2].
Because its effects are ultimately transmitted through the , LGD-3303 also engages androgen feedback on the brain and pituitary and, like other androgens, would be expected to suppress endogenous testosterone production and to shift lipid parameters such as HDL cholesterol with use [4]. Its documented ability to cross into the central nervous system and influence androgen-sensitive behavior in animal studies further reflects receptor-mediated activity beyond muscle and bone [3].
receptor fingerprint
(muscle)partial agonist
(bone)agonist
HPG axis (LH / FSH)suppresses
(prostate)weak partial agonist
Safetyrisks and cautions, not medical advice
There is no human safety data on LGD-3303 at all; the entire record is animal work. Expect the usual SARM downsides that show up across the class: suppression of your own testosterone, drops in HDL cholesterol, and the possibility of raised liver enzymes. It is not approved anywhere, it is banned by WADA and most sports bodies, and products sold as LGD-3303 are research chemicals with no guarantee of purity or dose. If someone is suppressed, recovery of the natural hormone axis is the main concern. Not intended for human use.
History
LGD-3303 was developed by Ligand Pharmaceuticals as part of its selective androgen receptor modulator program and characterized in a pair of influential studies published in 2008 and 2009. The first, by Vajda and colleagues in the Journal of Pharmacology and Experimental Therapeutics, detailed its pharmacokinetics and demonstrated that its tissue selectivity is a property of the androgen receptor itself rather than of drug distribution.
The second, in the Journal of Bone and Mineral Research, examined LGD-3303 in osteopenic female rats and showed it raised bone mineral density and stimulated new bone formation on the periosteal surface. A notable finding was that combining LGD-3303 with the bisphosphonate alendronate produced additive skeletal benefit, since the two agents work through separate anabolic and antiresorptive mechanisms. Together these reports positioned LGD-3303 as a compound with an unusually strong bone profile, and it was explicitly discussed as a potential future therapy for osteoporosis and frailty.
Reputation
LGD-3303 is regarded within the research literature as a standout for its pronounced effects on the skeleton, distinguishing it from SARMs valued mainly for muscle. Investigators highlighted that it increased levator ani muscle weight above intact levels while never driving prostate weight above about half of normal, a striking illustration of the partial-agonist tissue selectivity that defines the class.
Its demonstrated ability to add to the benefit of a standard bone drug is a genuinely interesting pharmacological point, since combination bone therapies do not always deliver extra gains. These qualities keep it a frequently referenced compound in discussions of anabolic bone strategies. In fairness, the evidence base is entirely preclinical, and LGD-3303 has not undergone the human clinical testing that would be required to establish its efficacy and safety in people, so its human profile remains uncharacterized.
Subjective profileweighing the evidence above
Strictly experimental. The bone-building data is the most interesting thing in the SARM class, but it is all rodents, there is no human safety record at all, and the class costs still apply: suppressed testosterone, lower HDL and possibly raised liver enzymes. Unapproved, banned in sport, and sold with no purity guarantee.
Resources
Don't even think about it.
Research
- 2009first citedPharmacokinetics and pharmacodynamics of LGD-3303 [9-chloro-2-ethyl-1-methyl-3-(2,2,2-trifluoro…
- 2019most recentHuman steroid biosynthesis, metabolism and excretion are differentially reflected by serum and…
- 1.Pharmacokinetics and pharmacodynamics of LGD-3303 [9-chloro-2-ethyl-1-methyl-3-(2,2,2-trifluoroethyl)-3H-pyrrolo-[3,2-f]quinolin-7(6H)-one], an orally available nonsteroidal-selective androgen receptor modulator
- 2.Combination treatment with a selective androgen receptor modulator q(SARM) and a bisphosphonate has additive effects in osteopenic female rats.
- 3.A selective androgen receptor modulator enhances male-directed sexual preference, proceptive behavior, and lordosis behavior in sexually experienced, but not sexually naive, female rats
- 4.Selective Androgen Receptor Modulators: Current Knowledge and Clinical Applications
- 5.A comparative study of the effect of the dose and exposure duration of anabolic androgenic steroids on behavior, cholinergic regulation, and oxidative stress in rats
- 6.Human steroid biosynthesis, metabolism and excretion are differentially reflected by serum and urine steroid metabolomes: A comprehensive review
- 7.Human hydroxysteroid dehydrogenases and pre-receptor regulation: insights into inhibitor design and evaluation
7 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
What is LGD-3303?
A nonsteroidal SARM developed by Ligand Pharmaceuticals, studied in animals for muscle and bone. It is not the same as LGD-4033 (Ligandrol), just a sibling from the same company.
What makes it interesting versus other SARMs?
Its bone effect. In rats it raised bone density strongly and even added to a bisphosphonate, while still sparing the prostate.
Is there human data?
No. It never went into human trials, so all claims rest on rodent studies. Anything about human results is guesswork.
Does it suppress testosterone?
Almost certainly, since it works through the androgen receptor. Every androgen that signals this way tends to feed back and lower your own production.
Is it legal or approved?
It is an unapproved research chemical, not a medicine, and it is banned in sport. It is sold for laboratory research only.
Limitations of the evidence
- No human safety data are available yet
Adverse effects
- HDL cholesterol may be reduced
- A mild rise in liver enzymes is possible
Notes and cautions
- Some suppression of natural testosterone is expected