OPK-88004 (LY2452473)

Overview

OPK-88004 is a true nonsteroidal selective androgen receptor modulator (SARM) — a small-molecule drug that binds the androgen receptor (AR). It is not a peptide and not a steroid. Chemically it is a cyclopenta[b]indole isopropyl-carbamate (PubChem CID 24963749).

The most confusing thing about this compound is its name. One molecule carried three different code names as it moved between three companies:

• LY2452473 — the originator code from Eli Lilly
• TT-701 — after licensing to Transition Therapeutics
• OPK-88004 — after moving to OPKO Health

All three refer to the same chemical entity. Its defining feature is tissue selectivity: it behaves as an AR agonist in skeletal muscle and bone while acting as an AR antagonist in the prostate (lowering PSA). That prostate-antagonist behaviour is why OPKO tested it for benign prostatic hyperplasia (BPH), rather than as a muscle-building drug.

Development never progressed past Phase 2. OPK-88004 is not an approved medicine anywhere, for any indication.

[!WARNING] OPK-88004 is an investigational research chemical, not a human-use product. It is not a "milder", "safer", or "legal" alternative to anabolic steroids. It has never been approved by any regulator, its BPH trial was terminated, and — like all SARMs — it is banned in sport (WADA S1.2). Material sold online as "OPK-88004" is frequently mislabelled or contaminated (see Safety). This page is a factual summary for research context and is not medical or legal advice (as of 2026).

Chemistry and structure

Mechanism of action

• Nonsteroidal AR ligand. OPK-88004 binds the androgen receptor as a small-molecule ligand rather than as a steroid or peptide. Its structure is an isopropyl carbamate of a cyano-substituted cyclopenta[b]indole scaffold (PubChem CID 24963749). [In vitro]
• AR agonist in muscle and bone. In prostate-cancer survivors it produced dose-related increases in whole-body and appendicular lean mass and a greater fall in percent body fat versus placebo (PMID 34019661). [Human]
• AR antagonist in the prostate. It blocks AR-mediated prostate signalling and lowers PSA — the rationale for testing it in BPH, where the registered primary endpoint was change in serum PSA (NCT03297398). No PSA recurrence occurred in prostatectomy survivors (PMID 34019661). [Human]
• Anabolism did not translate into function. Despite lean-mass gains, the trial's primary sexual-activity endpoint was not met and physical performance did not improve versus placebo (NCT02499497). [Human]

Research and evidence

Human data on OPK-88004 come from a small number of Phase 2 trials. It has never advanced beyond Phase 2, and no active later-phase program has been located.

Honest read of the evidence. The one peer-reviewed Phase 2 (PMID 34019661) is a genuine positive on body composition but a failure on its registered primary endpoint (sexual activity), and it did not improve physical performance. The BPH Phase 2 was terminated by the sponsor without a public efficacy result. The larger TT-701 hypogonadism claims come from company communications, not peer review, and should be treated as unverified.

Status and regulation

• Not approved anywhere. OPK-88004 is not an approved drug in the United States, the EU, or elsewhere, for BPH, hypogonadism, body composition, or any other indication.
• Highest verified phase: Phase 2. After the 2010s Phase 2 program and the terminated BPH trial, no active later-phase development has been located.
• WADA status (separate axis). Like all SARMs, OPK-88004 is prohibited in sport at all times, in and out of competition, under WADA S1.2 (Anabolic Agents — Other Anabolic Agents).

Safety

Human safety data specific to OPK-88004 are limited to short (12-week) monitored trials. The signals below combine those trial observations with class-level SARM safety data.

• Class-level hepatotoxicity / drug-induced liver injury (DILI). The FDA has warned that products containing SARMs are linked to serious or life-threatening harms including liver injury and acute liver failure, heart attack and stroke. This is a warning for the SARM product class broadly — not a documented OPK-88004-specific event. [Human]
• HPTA / testosterone suppression. Suppression of the hypothalamic-pituitary-testicular axis and endogenous testosterone is an expected pharmacology of AR agonists across the SARM class. OPK-88004 was studied in already androgen-deficient men, so axis effects in eugonadal users are not characterized in the located sources. [Hypothesis]
• Reassuring within trial limits. In the completed prostate-cancer-survivor Phase 2, no PSA recurrence and no erythrocytosis were reported over 12 weeks, and alkaline phosphatase decreased versus placebo. This is short exposure in a monitored population and does not generalize to unmonitored, higher-dose consumer use. [Human]
• Not an approved medicine. Development stalled at Phase 2 and the BPH trial was terminated. Research-reagent framing only — not a milder/safer/legal alternative to steroids. [Human]

The contamination reality. In a landmark analysis, Van Wagoner et al. (JAMA 2017;318(20):2004-2010, PMID 29183075) chemically tested 44 products sold as SARMs: only 52% actually contained the labelled SARM, 39% contained a different unapproved drug, 9% contained no active compound at all, and only about 41% were accurately dosed. A "SARM" label is not a reliable statement of contents — the product a consumer buys as "OPK-88004" may not be OPK-88004.

[!WARNING] There is no established safe dose of OPK-88004 for human use. Beyond the drug's own uncharacterized long-term risks (unknown human half-life, unquantified liver and HPTA effects), a product sold as OPK-88004 may contain a different drug, no drug, or a wildly inaccurate dose. Do not treat any SARM as a benign supplement.

Legal status

The legal status of OPK-88004 is not assessed here and varies by jurisdiction. Across many countries SARMs are not approved for human consumption and are handled as unapproved investigational drugs or research chemicals; some markets restrict or prohibit their sale for human use. This page frames OPK-88004 only as a research reagent, makes no claim about the legality of human use anywhere, and does not constitute legal advice. Note that anti-doping status (WADA) is a separate axis from legality: a substance can be legal to possess yet still banned in sport.

How it compares

OPK-88004 sits in the same nonsteroidal SARM family as several better-known research compounds — all androgen receptor modulators, none an approved medicine, all prohibited under WADA S1.2:

• Ostarine (MK-2866) — the most-studied SARM, and the one most often found as a contaminant in mislabelled products.
• Testolone (RAD-140) — a potent nonsteroidal SARM with documented liver-injury case reports.
• Ligandrol (LGD-4033) — a nonsteroidal SARM with clear evidence of testosterone suppression in humans.

Unlike those muscle-targeted candidates, OPK-88004 was developed primarily for its prostate-antagonist property (a BPH drug), which distinguishes its intended use even though the underlying mechanism is shared.

Common misconceptions

• "It's a peptide." No. OPK-88004 is a small-molecule nonsteroidal SARM (a cyclopenta[b]indole carbamate), not a peptide.
• "It's a safer, legal steroid." No. It is an unapproved investigational drug, its development stalled at Phase 2, and its BPH trial was terminated. It is banned in sport (WADA S1.2).
• "It builds muscle and improves performance." It increased lean mass in one trial, but that did not translate into improved physical performance or sexual activity — the trial's primary endpoint failed.
• "A specific dose gives a specific lean-mass gain." Per-dose kilogram figures (e.g. a specific gain at 5 mg) are sometimes quoted but could not be confirmed from the open-access abstract of PMID 34019661, which reports a dose-related increase without publishing the per-dose kilogram values. Treat any exact number as reported-but-unverified.
• "The BPH trial was stopped because of liver enzymes / ultrasound problems." The public registry lists the reason only as "terminated by sponsor decision" and the primary endpoint as change in serum PSA. Any more specific termination rationale is not reflected in the located record.