Side-by-side · Research reference

ACE-031vsHCG

Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.

APhase 2HUMAN-REVIEWED10/44 cited

BFDA-ApprovedHUMAN-REVIEWED12/52 cited

ACE-031

ActRIIB-Fc Fusion · Phase 2 Halted

Phase 2Highest trial stage

2011Development halted

~58.4 kDaMolecular weightReichel 2025

SQ · Weekly dosing investigated

HCG

Glycoprotein Hormone · LH Mimetic

2,000 IUTypical dose (2×/wk)Konsam 2026 Zachariou 2026

70–90%Sperm induction rateHuijben 2026 Zachariou 2026

12–24 moTime to sperm appearanceHuijben 2026 Nariyoshi 2025

IM or SQ · 2–3×/week

01Mechanism of Action

Parameter

ACE-031

HCG

Primary target

Myostatin, GDF11, activin A — TGF-β superfamily ligands

LH receptors on testicular Leydig cellsSchröder-Lange 2025

Pathway

Soluble decoy receptor binds circulating myostatin/TGF-β ligands → prevents ActRIIB activation → SMAD2/3 pathway inhibition

hCG → Leydig cell LH receptor → Intracellular cAMP → Steroidogenesis pathway activation → Testosterone synthesis

Downstream effect

Disinhibition of myogenic signaling, increased skeletal muscle mass and strength

Elevated intratesticular testosterone, restored spermatogenesis, virilization, secondary sex characteristic developmentKonsam 2026 Zachariou 2026

Feedback intact?

—

No — exogenous hCG bypasses hypothalamic-pituitary axis; endogenous LH remains suppressed

Origin

Recombinant fusion protein: human ActRIIB extracellular domain + IgG1-Fc fragmentReichel 2025

Heterodimeric glycoprotein (alpha subunit shared with LH/FSH/TSH; beta subunit confers specificity). Available as urinary-derived or recombinant formulations.

Antibody development

—

Rare with recombinant; possible with urinary-derived formulations

02Dosage Protocols

Parameter

ACE-031

HCG

Clinical dosing

Weekly or biweekly SQ injections (exact doses undisclosed pre-halt)

Phase 2 DMD trial protocol not fully published.

—

Black market products

Variable purity; 12/14 tested products contained target protein plus contaminantsReichel 2025

SDS-PAGE revealed multiple protein bands; quality control absent.Reichel 2025

—

Evidence basis

Phase 2 trial discontinued — incomplete dataset

RCT / Meta-analysis / FDA-approvedKonsam 2026 Huijben 2026

Half-life

Days to weeks (Fc-fusion typical kinetics)

IgG1-Fc domain confers extended circulation time.

—

Duration investigated

12–24 weeks (trial cut short)

—

Hypogonadotropic hypogonadism (monotherapy)

—

2,000 IU IM/SQ 2–3×/weekKonsam 2026 Zachariou 2026

Titrate to normalize testosterone (300–1,000 ng/dL) or achieve target AMH ~7.4 ng/mL.

Combined therapy (hCG + FSH)

—

hCG 2,000 IU 2×/wk + rFSH 75 IU 3×/wkKonsam 2026 Nariyoshi 2025

Preferred for azoospermia; FSH added after initial hCG phase or from outset.

Triple therapy (experimental)

—

hCG 2,000 IU 2×/wk + rFSH 75 IU 3×/wk + testosterone 100 mg IM q2wkKonsam 2026

May accelerate virilization; reduces hCG requirements (~30% lower cumulative dose vs monotherapy).

Cryptorchidism (pediatric)

—

500–4,000 IU IM 2–3×/week for 3–6 weeks

Duration to sperm appearance

—

12–24 months (median ~18 mo)Huijben 2026 Zachariou 2026

Congenital HH may require longer treatment; acquired HH responds faster.

Route

—

Intramuscular or subcutaneousKonsam 2026

Monitoring

—

Serum testosterone, semen analysis q3–6mo, testicular ultrasound

Thickened seminiferous tubules (>300 μm) on ultrasound predict imminent sperm appearance.Nariyoshi 2025

04Side Effects & Safety

Parameter

ACE-031

HCG

Epistaxis (nosebleeds)

Significant incidence in Phase 2 DMD trial — primary safety signal

—

Telangiectasia

Dilated capillaries / spider veins observed

—

Vascular abnormalities

Mechanism: ActRIIB/ALK1 pathway disruption affects vascular homeostasis

—

Injection site reactions

Local erythema, induration (biologics class effect)

—

Antibody development

Potential for anti-drug antibodies (Fc-fusion proteins); incidence not reported

—

Black market contaminants

12/14 tested products contained multiple unidentified proteins alongside ACE-031Reichel 2025

—

Injection site reaction

—

Pain, erythema (mild, transient)

Gynecomastia

—

Aromatization of elevated testosterone to estradiol; dose-dependent

Testicular discomfort / Edema

—

Rapid testicular growth in hypogonadal males; usually self-limiting

Polycythemia

—

Elevated hematocrit from supraphysiological testosterone; monitor CBC

Mood / Libido changes

—

Variable; usually positive with normalization of testosterone

Acne / Oily skin

—

Androgen-mediated; dose-dependent

Prostate concerns

—

Monitor PSA in older males; hCG restores physiological testosterone (not supraphysiological)

Antibody formation

—

Rare with recombinant; possible with urinary-derived

Absolute Contraindications

ACE-031

·History of vascular disorders (epistaxis, telangiectasia, HHT)
·Pregnancy (TGF-β pathway critical for fetal development)
·Active malignancy (myostatin inhibition may affect tumour growth)
·Use of non-pharmaceutical grade ACE-031 (contamination risk)Reichel 2025

HCG

·Androgen-dependent malignancy (prostate, breast cancer)
·Hypersensitivity to hCG or excipients
·Precocious puberty

Relative Contraindications

ACE-031

·Coagulation disorders or anticoagulant use (epistaxis risk)
·Hereditary hemorrhagic telangiectasia (HHT) family history
·Cardiovascular disease (vascular remodeling effects unknown)

HCG

·Untreated obstructive sleep apnea
·Severe cardiovascular disease (polycythemia risk)
·History of thromboembolism

05Administration Protocol

Parameter

ACE-031

HCG

1. Pharmaceutical status

ACE-031 is not FDA-approved or commercially available. Phase 2 development was discontinued in 2011 due to safety concerns. Any ACE-031 on the black market is unregulated research chemical.

Add sterile water or bacteriostatic water per manufacturer instructions. Typically 1–2 mL per 5,000–10,000 IU vial. Roll gently — do not shake. Solution should be clear.

2. Black market quality

12 of 14 tested black market ACE-031 products contained the target protein but also carried multiple unidentified protein contaminants detectable by SDS-PAGE. Two products contained no ACVR2B-immunoreactive material.Reichel 2025

Intramuscular: ventrogluteal, vastus lateralis, or deltoid. Subcutaneous: abdomen, avoiding navel (2-inch radius). Rotate sites to prevent lipohypertrophy.

3. Detection in sport

ACE-031 is prohibited under WADA S4.3 (Myostatin Inhibitors). Gel electrophoresis and Western blotting using ACVR2B-specific antibodies can detect the ~58.4 kDa protein in biological samples.Reichel 2025

Administer 2–3 times per week. Consistent weekly schedule recommended (e.g., Monday/Thursday or Monday/Wednesday/Friday).

4. Clinical trial route

Phase 2 protocol used subcutaneous injections at weekly or biweekly intervals. Exact dosing protocols remain unpublished.

Lyophilized: room temperature, light-protected. Reconstituted: refrigerate 2–8 °C. Bacteriostatic water extends shelf life to ~30 days; sterile water use within 72 hours.

5. Needle selection

—

IM: 21–23G, 1–1.5 inch. SQ: 25–27G, 5/8 inch. Inject slowly (30–60 seconds for IM).