B7-33: A Tracking Guide for a Single-Chain Relaxin Analog

B7-33 is a single-chain peptide analog of relaxin-2, designed to retain RXFP1 receptor signaling in a much smaller molecule. It is an early-stage research compound. There are no approved human indications, and the data set is dominated by in vitro and animal work in fibrosis, cardiac function, and tissue remodeling. Anything written about human protocols is, at this point, self-experimentation on top of a very thin evidence base.

What it is supposed to do

Relaxin signaling is associated with anti-fibrotic effects, vasodilation, and tissue remodeling. B7-33 was designed to preserve the bias toward ERK1/2 signaling that is associated with the anti-fibrotic effects, while being far simpler to produce than full-length relaxin. Most of the rationale for using it comes from preclinical work in cardiac, kidney, and lung fibrosis models.

Typical protocol shape

• Route: subcutaneous injection
• Frequency: once daily is most commonly reported
• Dose: there is no established human dose; self-reports vary widely and should be treated with caution
• Duration: short blocks of 4–8 weeks are most common

This is one of the compounds where "research only" is not a formality. The human safety profile is essentially uncharacterized.

What to track daily

• Resting heart rate
• Blood pressure, ideally morning and evening
• Subjective energy and exercise tolerance
• Any chest, breathing, or unusual cardiovascular symptoms
• Injection site reactions

What to track weekly

• Exercise capacity on a consistent test (steady-state cardio time, rower split)
• Recovery between sessions
• Sleep quality
• Any musculoskeletal changes — relaxin signaling affects connective tissue

Bloodwork worth doing

• Baseline and post-cycle CBC and CMP
• Kidney function (creatinine, eGFR)
• Liver enzymes
• If you have access, NT-proBNP and a baseline ECG are reasonable given the cardiac framing of the underlying biology

Realistic expectations

Honest self-reports on B7-33 are sparse and noisy. The compound's targets are systemic, the human evidence is essentially absent, and the most likely useful outcome of self-experimentation is data on tolerability, not efficacy. Anyone describing dramatic results should be treated with skepticism.

Common mistakes

• Treating preclinical fibrosis data as if it implies effects in healthy users
• Combining with other relaxin-pathway or cardiac-active compounds
• Skipping blood pressure tracking; vasodilation is a plausible effect
• Running long cycles without a defined endpoint

A tracking template

• Week 0: baseline bloodwork, blood pressure log for two weeks, exercise capacity test
• Weeks 1–4: daily injections, daily vitals and symptom log in Peptide IA
• Week 4: repeat bloodwork and exercise test
• Weeks 5–8: washout, repeat vitals to confirm return to baseline

Bottom line

B7-33 is genuinely early-stage. There is enough mechanistic interest to explain why it exists in self-experimenter conversations, and not enough human data to make confident claims about either safety or benefit. If you choose to use it, the most useful contribution you can make to your own understanding is a careful safety log: vitals, bloodwork, and any unusual symptoms.

Peptide IA is an educational and self-tracking tool. Nothing in this post is medical advice. Doses mentioned reflect what is commonly reported in research literature — they are not recommendations. Always consult a qualified physician before starting, changing, or stopping any protocol.