Important limitations
- Individual claims and source links have not yet completed editorial verification.
- Evidence level, applicable study model, formulation, route and population remain unassigned.
B7-33
B7-33 is a peptide currently undergoing active research, primarily due to its potent anti-fibrotic properties.
Dosing & scaling, explained
The moderated mass amounts below are retained for comparison. Near-duplicates, mix-dependent volumes and device markings are excluded. This is educational source context, not a protocol or recommendation.
Mass amounts available for comparison
- Lower range200 mcgDose
Recorded example with no verified study backing; shown for amount literacy only.
- Mid range800 mcgDose
Recorded example with no verified study backing; shown for amount literacy only.
Only mcg or mg amounts are retained. The calculator derives mL, syringe units or pen clicks from the current vial strength, water volume and device.
No independently verified schedule
Evidence context
No clinical amount or schedule is inferred from this material. Source verification is pending, and every displayed amount remains educational context rather than guidance.
Storage, handling and interpretation
Product identity
Verify the exact compound, formulation and amount against the product label or certificate before calculation.
Storage & handling
Follow the product label, certificate and validated laboratory SOP; no universal storage assumption is applied here.
Prepared solutions
Label concentration and preparation date, use sterile technique where applicable, and follow a validated stability protocol.
Reported protocols for B7-33
What published studies and recent community write-ups report about amounts, timing and course length. 7 preclinical and 5 community-reported rows, each linked to its source. These are descriptions of what others report, not instructions, and nothing here is medical advice.
| Context | Dose | Frequency | Route | Course | Source |
|---|---|---|---|---|---|
| Preclinical7 rows | |||||
| Rat heart failure after myocardial infarctionRats randomized 8 weeks after a myocardial infarction, with a saline and an H2 relaxin comparison group | 0.5 mg/kg per day | Continuous infusion | Intraperitoneal osmotic minipump | Weeks 8 to 12 after the infarctionNot applicable | Chemical Science (Royal Society of Chemistry)2016 |
| Left ventricular collagen fell significantly against saline-treated infarcted rats and end-diastolic pressure also fell, matching what H2 relaxin achieved at the same per-kilogram dose. The peptide was delivered by an implanted pump rather than by injection, which the paper does not frame as a schedule anyone could copy. | |||||
| Mouse isoprenaline cardiomyopathy7 to 8 week old male 129SV mice, 7 to 8 per group, injected with isoprenaline at 25 mg/kg daily for 5 days then left 9 days for fibrosis to develop | 0.25 mg/kg per day, chosen to be equimolar with 0.5 mg/kg per day of H2 relaxin | Continuous infusion | Subcutaneously implanted osmotic minipump | Through to day 14 after the injuryNot applicable | Chemical Science (Royal Society of Chemistry)2016 |
| Interstitial collagen staining fell by about 51% against isoprenaline alone, which matched native relaxin at the molar-equivalent dose. Group sizes were 7 to 8 animals, and blood pressure did not change. | |||||
| Mouse chronic allergic airways disease, intranasalFemale Balb/c mice with ovalbumin-induced chronic allergic airways disease | 0.4 mg/mL solution, equivalent to 0.25 mg/kg per day | Once daily | Intranasal | 14 days, from day 64 to day 77 of a 9-week modelNot applicable | Chemical Science (Royal Society of Chemistry)2016 |
| Airway epithelial thickening, total lung collagen and airway hyperresponsiveness all improved, to a similar extent as native relaxin given the same way. The 14-day treatment window was copied from earlier intranasal relaxin work rather than derived from this peptide's pharmacology. | |||||
| Mouse ischemia-reperfusion injuryAdult male CD1 mice: 38 given B7-33 and 34 given saline after 30 minutes of coronary artery occlusion, plus 9 sham animals | 0.25 mg/kg as a single dose for the 24-hour studies; 0.5 mg/kg per day in the 7-day studies | Once, 5 minutes before reperfusion, or daily for the 7-day arm | Intraperitoneal | Single dose assessed at 24 hours, or 7 days of dosingNot applicable | Journal of the American Heart Association (PubMed)2020 |
| Infarct size was 22.0% of the area at risk against 45.3% on vehicle, and fractional shortening was preserved at 24 hours and still better at 7 days. The authors picked 0.25 mg/kg specifically to match the molar exposure of the relaxin dose in the 2016 paper, since relaxin weighs roughly twice as much. | |||||
| Rat acute vascular function studyMale Wistar rats, with serelaxin and placebo comparison groups | 13.3 mcg/kg (compared against 26.6 mcg/kg of serelaxin, the molar equivalent) | Single bolus | Tail vein injection | Vascular function assessed 3 hours laterNot applicable | European Journal of Pharmacology (PubMed)2017 |
| A single low-dose injection enhanced bradykinin-driven relaxation in the mesenteric artery but did nothing measurable in the small renal artery or aorta. This is the lowest per-kilogram dose in the published record and the only one given as a plain injection rather than by pump. | |||||
| Mouse comparison against an ACE inhibitorAdult male 129sv mice with isoprenaline-induced cardiomyopathy, with relaxin and perindopril comparison arms | 0.25 mg/kg per day (against relaxin at 0.5 mg/kg per day and perindopril at 1 mg/kg per day) | Daily | Subcutaneous | Days 7 to 14 after the injuryNot applicable | Biomedicine and Pharmacotherapy (PubMed)2023 |
| B7-33 and relaxin both reduced left ventricular fibrosis, inflammation and cardiomyocyte hypertrophy and restored blood vessel density, while perindopril lowered blood pressure and inflammation but not fibrosis or hypertrophy. The treatment window was one week in mice, which says nothing about a course in a person. | |||||
| Serum stability work from the originating laboratoryIn vitro serum stability assays | Half-life of about 6 minutes in serum, extended to about 60 minutes by fatty-acid conjugation | Not applicable | In vitro | Not applicableNot applicable | International Journal of Molecular Sciences (PubMed)2023 |
| The Hossain group set out in 2023 to fix the peptide's short circulation time and reported that attaching a fatty acid with the right spacer length raised the in vitro half-life tenfold without losing activity. They describe the lipidated version as the one to take into animal pharmacokinetic work, which means plain B7-33 was not considered ready for that step. | |||||
| Community-reported5 rows | |||||
| Community reconstitution reference | 250 mcg, 500 mcg or 1,000 mcg per injection as illustrative figures | Twice daily, following the research pattern it describes | Subcutaneous from a 5 mg vial reconstituted in 2.0 mL of bacteriostatic water | Not specifiedNot specified | Community resource2026 |
| This 2026 page converts microgram amounts into insulin-syringe units at 2.5 mg/mL and states explicitly that B7-33 has never been tested in humans, has no validated human dose and is not approved by the FDA or EMA. It presents the figures as an educational measurement reference rather than a protocol. | |||||
| Community database dosing table | 100-250 mcg | Once daily | Subcutaneous | 4-8 weeks, described as extrapolated from preclinical workNot specified | Community resource2026 |
| This database lists a single anti-fibrotic protocol and labels the cycle length as a preclinical extrapolation rather than a validated figure. It states that dosing protocols rest on animal model data and have not been validated in human trials. | |||||
| Practitioner-reported range with a dose-translation warning | 100-500 mcg per injection; 200-400 mcg once daily as the commonly reported anti-fibrotic amount | Once or twice daily | Subcutaneous | 2-4 weeks for a short course, 6-8 weeks as the common duration, 12 weeks or more described anecdotallyNot specified | Community resource2026 |
| This 2026 guide marks its own figures as unverified and points out that the rodent dose of roughly 500 mcg/kg per day would scale to about 35 mg a day for a 70 kg adult, far above anything reported in practice. It says no dose-ranging human trial exists to validate any of it. | |||||
| Evidence review arguing against any injection schedule | No validated human dose; the rodent figures are 0.25-0.5 mg/kg per day | Continuous infusion or daily intranasal dosing in the published models | Osmotic minipump or intranasal in the research record | 14 days to 4 weeks in the animal studiesNot applicable | Community resource2026 |
| This review makes the pharmacokinetic argument directly: a peptide that clears from serum in about 6 minutes cannot hold a receptor effect on any schedule a person could follow, which is why the literature keeps engineering longer-acting versions rather than dosing the original. It also notes that human half-life, organ exposure and antibody response are all unmeasured. | |||||
| Evidence and risk summary | No established human dose; 0.25-0.5 mg/kg per day in rodents | Varies by animal model | Systemic infusion or intranasal in the published work | Not applicable to humansNot applicable | Community resource2026 |
| This page separates what the animal data show from what is claimed for the peptide online, noting that the kidney evidence is a dish of rat renal myofibroblasts rather than a kidney fibrosis model. It states that multiplying a mouse dose by body weight does not answer the missing pharmacokinetic questions. | |||||
How a course is commonly described
- Weeks 1-2Community-reported
Community pages describe starting at 100 to 200 mcg subcutaneously once daily and raising it over the following weeks based on tolerance. Nothing in the research record corresponds to this: the animal studies used implanted pumps, intranasal drops or single injections timed to an injury.
- Weeks 2-8Community-reported
A 4 to 8 week course at 100 to 250 mcg a day is the commonest structure described online, with the duration openly labelled as extrapolated from preclinical work. Community pages place expected changes in fibrosis markers in this window, again by analogy with animal timelines.
- Preclinical comparison, 14 daysPreclinical
The shortest effective courses in animals ran two weeks: 14 days of intranasal dosing in the airway model and days 7 to 14 after injury in the mouse heart models. Collagen and inflammation measures had already changed by the end of those windows.
- Preclinical comparison, 4 weeksPreclinical
The longest exposure in the record is four weeks of continuous intraperitoneal infusion in rats, from week 8 to week 12 after a heart attack, which reduced left ventricular collagen and filling pressure. Continuous delivery was the design choice, not a daily injection.
- No human has received B7-33 in a registered study. There is no human pharmacokinetic, safety or dose-finding data at all, so every figure in the community rows is an extrapolation from rodents.
- The measured in vitro serum half-life is about 6 minutes. Most animal studies used implanted osmotic minipumps for continuous delivery or timed a single dose to an injury, and the originating laboratory has since worked on lipidated and nanoparticle-bound versions specifically to lengthen exposure.
- Animal doses of 0.25 to 0.5 mg/kg per day do not scale down to the 100 to 500 mcg flat doses described online. One community guide works out that the rodent exposure would correspond to roughly 35 mg a day in a 70 kg adult.
- B7-33 is not approved by the FDA, the EMA or Health Canada, and no clinical trial has been registered for it. The one safety point the preclinical record does make is that it did not promote prostate tumor growth in mice, unlike full-length relaxin.
Sources for this section (12)
- A single-chain derivative of the relaxin hormone is a functionally selective agonist of the G protein-coupled receptor, RXFP1
- A single-chain derivative of the relaxin hormone is a functionally selective agonist of the G protein-coupled receptor, RXFP1 (PubMed record)
- B7-33 replicates the vasoprotective functions of human relaxin-2 (serelaxin)
- B7-33, a Functionally Selective Relaxin Receptor 1 Agonist, Attenuates Myocardial Infarction-Related Adverse Cardiac Remodeling in Mice
- The single-chain relaxin mimetic, B7-33, maintains the cardioprotective effects of relaxin and more rapidly reduces left ventricular fibrosis compared to perindopril in an experimental model of cardiomyopathy
- A Lipidated Single-B-Chain Derivative of Relaxin Exhibits Improved In Vitro Serum Stability without Altering Activity
Plus 6 community resources (dosing guides, forum threads and vendor write-ups), reported above but not linked.
Overview
B7-33 is a 27-residue single-chain peptide built from residues 7 to 33 of the B-chain of human relaxin-2, with the two cysteines swapped for serines so it cannot form the disulfide bonds of the native hormone and with four extra residues on the C-terminus. It came from Mohammed Akhter Hossain's group at the Florey Institute in Melbourne, published in 2016, and the point of the design was manufacturability: full-length relaxin needs two chains and three disulfide bridges, which makes it expensive, while a single chain does not. It is a biased agonist at the relaxin receptor RXFP1, preferring the pERK1/2 route over cAMP, and in rodent models of heart, lung and vascular disease it matched relaxin's anti-fibrotic effect without promoting prostate tumor growth the way relaxin did. No human has ever received it: there are no registered clinical trials, no human pharmacokinetics and no regulatory approval anywhere, and its measured serum half-life in vitro is about 6 minutes.
What researchers are exploring
These themes organize the educational information currently available. Individual claims remain under source review and are not treatment claims.
- 1
Ease of Production
Advantages of B7-33 production compared to native H2-relaxin
- 2
Research and the Heart
B7-33's effects on cardiovascular health and anti-fibrotic properties
- 3
Summary
Overview of B7-33's therapeutic potential and applications
What is known and what still needs verification
Available context is organized without assigning unsupported study models or evidence grades.
- Not graded
Ease of Production
Advantages of B7-33 production compared to native H2-relaxin
- Not graded
Research and the Heart
B7-33's effects on cardiovascular health and anti-fibrotic properties
Amounts recorded for B7-33
These amount records are independent from vial strength, reconstitution volume and measuring device. A recorded source is not the same as study backing, and these values are not recommendations.
- 1Dose · lower endpointSign in for schedule, duration and source context.200 mcg
- 2Dose · upper endpointSign in for schedule, duration and source context.800 mcg
Chemistry identifiers
Sequence, synonyms and registry identifiers as recorded in PubChem, the National Library of Medicine's open chemistry database. Formula, mass and CAS number are summarized at the top of the page.
Sequence
Val-Ile-Lys-Leu-Ser-Gly-Arg-Glu-Leu-Val-Arg-Ala-Gln-Ile-Ala-Ile-Ser-Gly-Met-Ser-Thr-Trp-Ser-Lys-Arg-Ser-Leu-NH2 (the two native cysteines are replaced by serine)
Also listed as
B7-33, (B7-33)H2, H-Val-Ile-Lys-Leu-Ser-Gly-Arg-Glu-Leu-Val-Arg-Ala-Gln-Ile-Ala-Ile-Ser-Gly-Met-Ser-Thr-Trp-Ser-Lys-Arg-Ser-Leu-NH2 (PubChem record title), CHEMBL4780098, GTPL9321, BDBM50563231
InChIKey
UAGASAJLEJWQIF-GARFIVTISA-N
IUPAC name
(4S)-5-[[(2S)-1-[[(2S)-1-[[(2S)-1-[[(2S)-1-[[(2S)-5-amino-1-[[(2S,3S)-1-[[(2S)-1-[[(2S,3S)-1-[[(2S)-1-[[2-[[(2S)-1-[[(2S)-1-[[(2S,3R)-1-[[(2S)-1-[[(2S)-1-[[(2S)-6-amino-1-[[(2S)-1-[[(2S)-1-[[(2S)-1-amino-4-methyl-1-oxopentan-2-yl]amino]-3-hydroxy-1-oxopropan-2-yl]amino]-5-carbamimidamido-1-oxopentan-2-yl]amino]-1-oxohexan-2-yl]amino]-3-hydroxy-1-oxopropan-2-yl]amino]-3-(1H-indol-3-yl)-1-oxopropan-2-yl]amino]-3-hydroxy-1-oxobutan-2-yl]amino]-3-hydroxy-1-oxopropan-2-yl]amino]-4-methylsulfanyl-1-oxobutan-2-yl]amino]-2-oxoethyl]amino]-3-hydroxy-1-oxopropan-2-yl]amino]-3-methyl-1-oxopentan-2-yl]amino]-1-oxopropan-2-yl]amino]-3-methyl-1-oxopentan-2-yl]amino]-1,5-dioxopentan-2-yl]amino]-1-oxopropan-2-yl]amino]-5-carbamimidamido-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-4-methyl-1-oxopentan-2-yl]amino]-4-[[(2S)-2-[[2-[[(2S)-2-[[(2S)-2-[[(2S)-6-amino-2-[[(2S,3S)-2-[[(2S)-2-amino-3-methylbutanoyl]amino]-3-methylpentanoyl]amino]hexanoyl]amino]-4-methylpentanoyl]amino]-3-hydroxypropanoyl]amino]acetyl]amino]-5-carbamimidamidopentanoyl]amino]-5-oxopentanoic acid
Limitations and unknowns
Sources
1 link carried over from the earlier page, awaiting verification.