PinnyPeptide

B7-33 vs GDF-8 95 (Myostatin Inhibitor)

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

Peptide A

B7-33

Muscle Growth

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

Peptide B

GDF-8 95 (Myostatin Inhibitor)

Muscle Growth

Short-peptide myostatin inhibitor targeting the GDF-8 / activin RIIB pathway.

Typical vial

2 mg

Typical dose

1000-2000 mcg

Half-life

~2-3 hours

FDA status

Not FDA approved.

Typical vial

1 mg

Typical dose

50-200 mcg

Half-life

Variable / poorly characterized for short-peptide formulations

FDA status

Not FDA approved.

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

GDF-8 95 (Myostatin Inhibitor) effects

  • Theoretical inhibition of myostatin signaling
  • Potential muscle hypertrophy via removal of myostatin brake
  • Limited direct evidence for short-peptide formulations in humans
  • Mechanistic rationale supported by pathway biology

B7-33 side effects

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

GDF-8 95 (Myostatin Inhibitor) side effects

  • Largely uncharacterized in humans
  • Theoretical: capillary leak if cross-reactivity with other TGF-β ligands occurs
  • Injection-site reactions
  • Possible immunogenicity (anti-drug antibody formation)

B7-33 dosing ranges

Research / anti-fibrotic

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

GDF-8 95 (Myostatin Inhibitor) dosing ranges

Research / muscle hypertrophy

50-200 mcg · Daily or twice-weekly (SubQ) · Per research protocol

Full B7-33 guide → Full GDF-8 95 (Myostatin Inhibitor) guide →

B7-33 vs GDF-8 95 (Myostatin Inhibitor) — common questions

What is the difference between B7-33 and GDF-8 95 (Myostatin Inhibitor)?

B7-33: Single-chain relaxin peptide analog with anti-fibrotic and cardioprotective activity. Typical dose 1000-2000 mcg. GDF-8 95 (Myostatin Inhibitor): Short-peptide myostatin inhibitor targeting the GDF-8 / activin RIIB pathway. Typical dose 50-200 mcg. Both fall under the Muscle Growth category.

Can you stack B7-33 and GDF-8 95 (Myostatin Inhibitor)?

Stacking B7-33 with GDF-8 95 (Myostatin Inhibitor) 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, B7-33 or GDF-8 95 (Myostatin Inhibitor)?

B7-33 is typically dosed: Daily (SubQ or IV in preclinical work) for Research / anti-fibrotic. GDF-8 95 (Myostatin Inhibitor) is typically dosed: Daily or twice-weekly (SubQ) for Research / muscle hypertrophy.

Are B7-33 and GDF-8 95 (Myostatin Inhibitor) FDA approved?

B7-33: Not FDA approved. GDF-8 95 (Myostatin Inhibitor): Not FDA approved.

Related peptide comparisons

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