PinnyPeptide

ACE-031 vs B7-33

Side-by-side comparison: effects, dosing ranges, side effects, regulatory status, and reconstitution.

Peptide A

ACE-031

Muscle Growth

Soluble myostatin / activin trap — recombinant decoy of the activin IIB receptor.

Peptide B

B7-33

Muscle Growth

Single-chain relaxin peptide analog with anti-fibrotic and cardioprotective activity.

Typical vial

1 mg

Typical dose

Per kg dosing mcg

Half-life

~10-15 days (Fc-fusion)

FDA status

Not FDA approved. Clinical development halted in 2011 after …

Typical vial

2 mg

Typical dose

1000-2000 mcg

Half-life

~2-3 hours

FDA status

Not FDA approved.

ACE-031 effects

  • Inhibits myostatin and related TGF-β superfamily ligands
  • Rapid increases in lean muscle mass in clinical trials
  • Increased thigh muscle volume by MRI
  • Increased serum markers of muscle growth
  • Reduced fat mass in some trial subjects

B7-33 effects

  • Anti-fibrotic action in heart, lung, kidney tissue
  • Activates RXFP1 receptor via cGMP signaling arm
  • Vasodilatory effects
  • May support tissue remodeling and scar prevention
  • Reduces collagen deposition in injury models

ACE-031 side effects

  • Capillary leak (gum bleeds, nosebleeds, telangiectasias) — clinical trial finding
  • Injection-site reactions
  • Headache
  • Potential off-target effects on vasculature and bone
  • Limited long-term safety data

B7-33 side effects

  • Human safety data essentially absent
  • Theoretical: hypotension from vasodilation
  • Injection-site reactions
  • Possible effect on uterine / cervical tissue (relaxin family)

ACE-031 dosing ranges

Research / muscle volume increase

0.5-3 mg/kg · IV or SubQ every 2-4 weeks · Per protocol

B7-33 dosing ranges

Research / anti-fibrotic

1-2 mg · Daily (SubQ or IV in preclinical work) · Per research protocol

ACE-031 vs B7-33 — common questions

What is the difference between ACE-031 and B7-33?

ACE-031: Soluble myostatin / activin trap — recombinant decoy of the activin IIB receptor. Typical dose Per kg dosing mcg. B7-33: Single-chain relaxin peptide analog with anti-fibrotic and cardioprotective activity. Typical dose 1000-2000 mcg. Both fall under the Muscle Growth category.

Can you stack ACE-031 and B7-33?

Stacking ACE-031 with B7-33 is a protocol-design question best raised with a clinician — it depends on your goal, current bloodwork, and whether both peptides target overlapping mechanisms. Both peptides should be tracked independently with separate injection sites and timing. PinnyPeptide supports multi-peptide stacks with automatic injection site rotation.

Which is dosed more frequently, ACE-031 or B7-33?

ACE-031 is typically dosed: IV or SubQ every 2-4 weeks for Research / muscle volume increase. B7-33 is typically dosed: Daily (SubQ or IV in preclinical work) for Research / anti-fibrotic.

Are ACE-031 and B7-33 FDA approved?

ACE-031: Not FDA approved. Clinical development halted in 2011 after capillary leak observations. B7-33: Not FDA approved.

Tracking either of these?

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