S-23

Areas of active research — not promised effects

Each tag links to other compounds with research into that goal. Research use only: these are areas of study, not human-use claims.

Related by research scope · open each to compare

S-23 has no FDA-approved indication. It is not listed as a controlled substance under the Controlled Substances Act. However, marketing or selling it for human consumption — including as a dietary supplement or performance enhancer — is unlawful under the Food, Drug, and Cosmetic Act as an unapproved new drug. Research-use-only supply to qualified laboratories occupies a grey area but does not confer any authorisation for clinical or human use. The FDA has taken enforcement actions against SARM vendors.

Transparent blend · bci-1.0 · never paid-placement

Primary name

S-23

Origin

Synthetic small molecule developed by GTx, Inc. as part of a programme to create tissue-selective androgen receptor modulators for potential use in hormonal male contraception and muscle/bone conditions. S-23 is the S-enantiomer of a fluorinated, chlorinated aryl-propionamide scaffold derived from structure-activity-relationship optimisation of earlier GTx SARM series. The compound has remained entirely in preclinical investigation and has never entered clinical trials for any indication.

Registry IDs

PubChem CID

24892822

CAS

1010396-29-8

InChIKey

SSFVOEAXHZGTRJ-KRWDZBQOSA-N

DrugBank

DB07419

ChEMBL

CHEMBL512283

Molecular formula

C18H13ClF4N2O3

Molar mass

416.8 g/mol

Monoisotopic

416.0550826 Da

InChIKey

SSFVOEAXHZGTRJ-KRWDZBQOSA-N

Appearance

White to off-white crystalline powder

Solubility

Poorly water-soluble; soluble in DMSO (~10 mg/mL) and ethanol; oral bioavailabil…

Sequence not available in current seed.

Stability: Stable as a dry solid under recommended cold, dark, dry conditions. Fluorine and chlorine substituents confer metabolic stability relative to earlier SARM serie

Vial sizes

null mg

Purity grades

≥98% / ≥99%

Salt forms

Free base (primary)

• GHS hazard class on file
• PPE & spill response
• Disposal guidance
• Not-for-human-consumption posture

How much research exists, and of what maturity — never a verdict on whether it works.

Mechanism of action

• S-23 binds the androgen receptor (AR) with high affinity (Ki approximately 1.7 nM) and functions as a full agonist, recruiting AR-associated coactivators to promote androgen-responsive gene transcription in both anabolic tissues (skeletal muscle, bone) and androgenic tissues (prostate, seminal vesicles)
• Its fluorinated aryl-propionamide scaffold confers oral bioavailability (~96% in rat models) and metabolic stability superior to earlier SARM prototypes, enabling dose-dependent AR activation without the need for injectable delivery
• In intact and castrated male rat models, S-23 dose-dependently suppressed pituitary gonadotropins (LH and FSH) via hypothalamic-pituitary-gonadal axis feedback, thereby reducing intratesticular androgen levels and profoundly inhibiting spermatogenesis; this suppression was fully reversible upon cessation of treatment in those models
• Alongside its contraceptive signal, S-23 increased levator ani muscle weight and reduced fat mass in rodent studies, demonstrating anabolic and body-composition activity consistent with AR agonism in peripheral tissues

Pharmacokinetics (ADME)

Half-life

~11.9–12 hours (rat; oral pharmacokinetic studies)

Clearance

Not formally published in humans; rat data indicate adequate clearance to support twice-daily dosing in preclinical protocols

PK–PD note: Oral bioavailability approximately 96% and peak plasma concentration achieved at ~4 hours post-dose in rat studies. No human pharmacokinetic data have been published. The ~12-hour half-life in rodents…

Reading the evidence

• Evidence quality and gaps vary by application — see the cited grades above.
• Indexed-article counts span all evidence tiers, not only completed human trials.
• No first-party human-dosing, efficacy, or benefit claims are made here.

Key reviews & evidence-gap sources

• Solomon ZJ, Rivera Mirabal J, Mazur DJ, et al. Selective Androgen Receptor Modulators (SARMs) – Current Knowledge and Clinical Applications. Sex Med Rev. 2019;7(1):84-94. PMID 30503797 — Narrative review of SARMs; discusses S-23 preclinical contraceptive data (Jones et al. 2009) in rats. No human trials of S-23.
• Christiansen A. Selective androgen receptor modulators: the future of androgen therapy? Transl Androl Urol. 2020. (PubMed/Medline + ScienceDirect search yielded 764 SARM results total) — Broad SARM review; mentions S-23 and C-6 animal contraceptive studies. No S-23 human data.
• Wen Y, et al. Selective Androgen Receptor Modulators (SARMs) Effects on Physical Performance: A Systematic Review of RCTs. Clin Endocrinol. 2025. — PRISMA systematic review of SARM RCTs (PubMed/Embase/Cochrane, searched Nov 2023). S-23 not among SARMs with human RCT data.
• Jones A, Chen J, Hwang DJ, Miller DD, Dalton JT. Preclinical characterization of S-23: a SARM for hormonal male contraception. Endocrinology. 2009;150(1):385-95. PMID 18772237 — Primary preclinical/animal study — the anchoring mechanistic + in-vivo source for S-23 (Ki, ED50, spermatogenesis, BMD, lean mass in rats).
• Marhefka CA, Gao W, Chung K, et al. Design, synthesis, and biological characterization of metabolically stable SARMs. J Med Chem. 2004;47(4):993-8. PMID 14761201 — Original design/synthesis paper for S-23 and related aryl-propionamide SARMs. Cited via Wikipedia/Infogalactic; not directly retrieved from PubMed.

4 registered trials — 2 currently recruiting.

NA
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RECRUITING

Phase 2
NCT01262729
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TERMINATED

NA
NCT05750329
Liver Transplantation With Two-stage Liver Resection in Unresectable Liver Cancer , Metastases or Emd-stage Liver Disease (LTLR-LC)

NOT_YET_RECRUITING

NA
NCT07442721
Sacral ESPB vs. PENG Block for Hip Hemiarthroplasty Analgesia

RECRUITING

Summary (literature)

No controlled human safety studies for S-23 have been published. Safety inferences are drawn exclusively from preclinical rodent work and extrapolation from the broader SARM class. In animal models, the primary documented pharmacological safety concern is profound suppression of …

WADA status

Prohibited in-competition and out-of-competition under the WADA 2026 Prohibited List, Section S1.2 (Other Anabolic Agents — Selective Androgen Receptor Modulato…

Dominant research route: Oral (PO)

Oral gavage in castrated male rats (0.01–3 mg/day, 14 days) for anabolic/androgenic organ-weight endpoints; oral dosing in intact male rats (0.05–0.75 mg/day) combined with estradiol benzoate for contraception studies; oral microdose (1, 10, 50 µg) human excretion study; single ~8 mg oral human volunteer metabolism study

Bioavailability: Preclinical characterization reports ~96% oral bioavailability in rats without 17α-alkylation, attributed to para-cyano substitution; terminal half-life ~11.9 h in preclinical models. Human oral microdose study detected 18 metabolites with parent detectable up to 253 h (1 µg) and 544 h (50 µg).

Dominant research route. Animal PK (rat) and human doping-control excretion studies both use oral administration. No therapeutic human trial; human data limited to microdose excretion kinetics and a single-volunteer metabolism study.

Daily SC injections in castrated male rats for 14 days, doses 0.01–3 mg/day, assessing prostate, seminal vesicle, and levator ani muscle weights

Bioavailability: Used as the reference parenteral route for anabolic/androgenic potency profiling in the preclinical characterization; bioavailability not separately reported for SC.

SC was the route used in the foundational rat pharmacology bioassay (castrated male rat organ-weight model). No human SC data located.

Class-level statement only; no S-23-specific transdermal study identified

Bioavailability: Review states SARMs as a class exhibit 'excellent oral and transdermal bioavailability'; no S-23-specific transdermal PK data cited.

Transdermal bioavailability is asserted at the SARM class level in a narrative review; no primary S-23 transdermal study was located. Treat as class-level mechanistic inference, not compound-specific evidence.

Animal & human figures are kept visibly separate so studied animal doses are never misread as human guidance.

Sorted A–Z by vendor — never by price

Weekly median $/mg from the live vendor crawl.

Researched storefront prices, bucketed

p25 $0.070 · median $0.095 · p75 $0.108 · 6 researched vendors

Legit, COA-backed band: $0.067–$0.117/mg.

Value rule: don't just buy the cheapest — a price under $3/mg is a red flag. Pair price with COA and independent-test grade.

Estimated cost of research (10 mg)

Vial (best researched price)

$1

Bacteriostatic water (generic estimate)

$6

Syringes / supplies (generic estimate)

$12

What each test proves — general guidance, plus this compound's researched purity data

Purity on the current market (researched)

Gray-market vendor claims of '99%+ purity' for S-23 are common (e.g., PureRawz, Sports Technology Labs); independent aggregate testing by Janoshik (2024) found 43% of gray-market peptide samples failed label purity claims, with lower-tier vendors testing 71–91% despite 99%+ claims — S-23-specific independent purity data not published.

Independent labs cited for this compound

No FDA recall, market withdrawal, or safety alert specific to 'S-23' was found in the FDA Recalls/Safety Alerts database; SARMs are instead addressed via warning letters, import detention, and criminal prosecution rather than recall pathways (none found).

Buyer red-flag checklist

• S-23 has no FDA-approved drug application and cannot be legally marketed in the U.S. as a dietary supplement or drug (FDA, 2023).
• FDA warning letters (2023–2025) repeatedly name S-23 among SARMs sold as 'research compounds'/'not for human consumption' while bearing human-use claims.
• Bulk SARM ingredients are commonly imported from China with unverified safety/identity (DOJ SARMTECH case, 2023).
• Stealth shipping/misdeclaration of SARMs as vitamins/supplements to evade seizure is documented in federal prosecutions.
• Gray-market purity claims of '99%+' are frequently unverified; independent aggregate testing shows ~43% failure rate vs label (Janoshik 2024).
• S-23 is prohibited by WADA/USADA; any detected use is grounds for athletic sanction.
• No completed human clinical trials of S-23 exist; all human-effect claims are extrapolated from preclinical rodent data.

GMP vs research-grade: the chemistry (SPPS + HPLC + MS) is identical — the difference is the quality system.

Underdosing / mislabeling: Janoshik Analytical reported that 43% of gray-market peptide samples tested in 2024 failed to meet label purity claims (lower-tier vendors 71–91% vs claimed 99%+). This is a peptide/SARM gray-market aggregate, not an S-23-specific figure; no S-23-only underdosing prevalence has been published by Janoshik, MZ Biolabs, or Finnrick.

• Detention Without Physical Examination of Unapproved New Drugs Promoted In The U.S. SARMs (including S-23) marketed without an approved NDA/ANDA are subject to DWPE; firms on the Red List may be detained without physical examination.66-41
• An RUO label is not an import exemption — CBP judges actual intended use.
• Lyophilized powder is ambient-stable in transit; temperature control needed for > 7-day transit.
• US-warehouse vendors dodge import scrutiny — they cost more but ship more reliably.

Every item dated & sourced

Prohibited at all times under S1.2 (Other Anabolic Agents); S-23 named explicitly as a non-Specified Substance.

No granted patents identified in current seed. Composition-of-matter coverage is limited given the peptide's synthetic origin.

• IACUC / IRB research context
• RUO buyer responsibilities & documentation
• Veterinary / alternative-use where lawful
• Jurisdiction-aware "who may lawfully obtain"

What people discuss

Reported concerns — discussion, not established effects

Reading caveats

• Self-selection bias: posters are self-experimenters willing to use unapproved research chemicals
• Survivorship/engagement bias: extreme experiences (very positive or very negative) overrepresented
• Source-affiliation bias: some posters linked to SARMs vendors or affiliate blogs
• No controlled dosing: products of unknown purity/label accuracy discussed

Manually researched from reddit, youtube— theme weights are research estimates, not live counts; aggregated & de-identified. No individual posts, quotes, or usernames are ever shown.

Relative research / market volume — populated once the activity stream is wired

Inline tooltips for lyophilized, RUO, EU/mg, SPPS, 503A and more.

Toggle plain-language ↔ scientific in the header.

• How to read a COA
• Free base vs acetate
• Understanding evidence grades

Investigational aryl-propionamide SARM (Ki ~1.7 nM) studied preclinically for male contraception and muscle/bone anabolism; no human trials; sport-prohibited. Approximately 12 articles are indexed (literature last scanned 2026-05-29). US regulatory status: Not FDA-approved; not a scheduled controlled substance; sold only for research use. Research use only.

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