RESEARCH MONOGRAPH · KDC-MN-272

Raloxifene

May 9, 2026 Kodiac biolabs Research Revised May 30, 2026 3 min read

Our opinion on this compound

81/100

Second-generation SERM optimized for bone with a cleaner endometrial profile than tamoxifen

Raloxifene is the SERM that fixed the worst feature of tamoxifen at the cost of some of its breast-cancer-treatment edge. Eli Lilly's benzothiophene scaffold (developed out of the same kind of structure-activity work that produced LY117018 and related compounds) gave a SERM with strong antagonist activity at endometrial ER, which solved the endometrial hyperplasia and cancer risk that tamoxifen carries. The trade-off is that raloxifene is less effective as a breast cancer treatment than tamoxifen, which is why the indications split: tamoxifen for breast cancer treatment and prevention, raloxifene primarily for postmenopausal osteoporosis with a secondary indication in breast cancer prevention.

The mechanism is the same core SERM story with different tissue weighting. Differential coactivator recruitment to the raloxifene-ER complex versus the estradiol-ER complex, with tissue-specific patterns that favor agonism in bone and antagonism in breast and endometrium. The benzothiophene scaffold produces a slightly different conformational change in ER than the triphenylethylenes, which is part of why the tissue profile differs.

The MORE and STAR trials are the relevant large clinical datasets. MORE established the bone density and fracture reduction effects in postmenopausal osteoporosis; STAR compared raloxifene head-to-head with tamoxifen in breast cancer prevention in postmenopausal women at elevated risk and showed raloxifene with somewhat lower efficacy but a substantially cleaner endometrial and thromboembolic profile.

What we like for research use is the cleaner tissue-selectivity profile. If you're studying SERM pharmacology and want a compound where the endometrial signal is minimal, raloxifene is the choice. The bone effects make it a useful tool for osteoporosis-relevant in vivo work.

What we dont like is the venous thromboembolism risk persists, even if it's no worse than tamoxifen, and the hot-flash adverse effect is real and dose-limiting in some studies. For male research contexts (and there's some interest in raloxifene for breast cancer prevention and gynecomastia in male populations) the data is much thinner.

Sourcing is good. Off-patent, multiple generic manufacturers, the hydrochloride salt is standard. Pharmacopoeial quality is widely available.

Established workhorse for postmenopausal bone health with reasonable data behind the breast cancer prevention claim. Mechanism is well-characterized, reliability is high. Underappreciated mostly as a research tool for tissue-selective ER pharmacology.

Evidence: 88
Mechanism: 85
Reliability: 82
Safety: 75
Sourcing: 88
Value: 80
Signal: 70
Staying power: 78

Plain-language summary Intrigue 60 / 100

Raloxifene (Evista) is a second-generation SERM approved in 1997 for postmenopausal osteoporosis, with a secondary indication for breast cancer prevention in high-risk women. Where tamoxifen is a partial activator in the uterus (creating an endometrial cancer risk), raloxifene is a blocker there as well as in the breast, eliminating that risk. It still acts as a partial activator in bone and liver, supporting the bone density and lipid-profile improvements. Trade-offs: more hot flashes than tamoxifen and increased risk of blood clots. The MORE and STAR trials established its osteoporosis and breast-cancer-prevention efficacy, respectively. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Second-generation SERM (benzothiophene)

A benzothiophene SERM; an osteoporosis drug with breast cancer prevention activity but no uterine partial agonism, distinguishing it from tamoxifen.

Abstract

Raloxifene ([6-hydroxy-2-(4-hydroxyphenyl)benzothiophen-3-yl]-[4-(2-piperidin-1-ylethoxy)phenyl]methanone; CAS 84449-90-1; molecular formula C28H27NO4S; molecular weight 473.58) is a benzothiophene second-generation SERM developed at Eli Lilly and approved by the FDA in 1997 under the trade name Evista. Distinct from tamoxifen by tissue selectivity profile: ER antagonism in breast and uterus, partial agonism in bone and liver. The absence of uterine partial agonism eliminates the endometrial cancer risk seen with tamoxifen and is the principal distinguishing clinical feature. Plasma half-life is approximately 27 hours; metabolism is via glucuronidation. Approved for postmenopausal osteoporosis treatment and prevention, and for breast cancer risk reduction in postmenopausal women at high risk. The MORE and STAR trials established the breast cancer prevention activity. Adverse events include thromboembolism (similar to tamoxifen), hot flashes, and leg cramps. Used as the canonical second-generation SERM with bone-selective profile.

Mechanism of action

Benzothiophene SERM; ER antagonist in breast and uterus, partial agonist in bone and liver. No uterine partial agonism distinguishes it from tamoxifen.

Reported research dose ranges

Clinical 60 mg in the published literature. Rodent studies 1 to 10 mg/kg.

References

Cummings SR, et al. The effect of raloxifene on risk of breast cancer in postmenopausal women: results from the MORE randomized trial. JAMA 1999.
Vogel VG, et al. Effects of tamoxifen vs raloxifene on the risk of developing invasive breast cancer (STAR P-2). JAMA 2006.
Riggs BL, Hartmann LC. Selective estrogen-receptor modulators: mechanisms of action and application to clinical practice. N Engl J Med 2003.

Read the full monograph

The full reference document is available as a research-use-only PDF download. Note: PDFs for newly added compounds may take a few hours to propagate after this article was published.

KDC-MN-272

The full reference document is provided strictly for research use only. It reports research dose ranges from the published literature, not instructions for use in humans or animals.

Download PDF →

FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

Kodiac sells research compounds for investigative use only.

Raloxifene

Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

Quick actions

Categories

Help and policies

Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

Adjacent monographs