B7-33

B7-33 Overview

B7-33 is a synthetic, single-chain peptidomimetic that acts as an agonist at the relaxin family peptide receptor 1 (RXFP1). It is derived from the B-chain of human gene-2 relaxin and was engineered to copy relaxin's protective effects on blood vessels and its anti-fibrotic activity, while being cheaper to manufacture and offering improved pharmacological characteristics. Like most peptides on the market, it is sold as a research chemical that must be reconstituted and injected subcutaneously, and both purity and storage conditions matter.

Editorial Verdict

The data here come almost entirely from animals and cell cultures. The receptor-targeting story is plausible and the preclinical results are consistent, but there is a hard ceiling on what we can claim: there is no human trial evidence at all. Anyone treating B7-33 as a proven cardiac or vascular therapy is getting ahead of the science.

Evidence Quality

We assign a research grade of C+. That sits on 12 peer-reviewed studies, broken down as 9 animal studies, 2 in vitro studies, and 1 review. Every one of the 12 classified findings was supportive, which looks impressive until you note the absence of any randomized controlled trials or meta-analyses in humans. A clean preclinical record is encouraging but is not a substitute for human data.

What the Research Shows

One mouse study reported that B7-33 reduced heart damage and scarring following a heart attack by switching on protective signaling without the downsides associated with conventional relaxin treatment. A separate in vitro investigation showed that B7-33 reproduces the vascular benefits of human relaxin, supporting blood-vessel health and lowering systemic vascular resistance. In animal models it has been described as highly effective at preventing adverse remodeling after myocardial infarction, and it appears to selectively engage RXFP1, which limits off-target signaling.

Dosage

There is no validated human protocol. Animal studies generally dose by body weight, and anecdotal human use falls roughly in the 1-5 mg daily range. Because it is a peptide, it is usually injected subcutaneously every day or every other day. Some users describe a brief high-dose loading period to reach steady state, but this practice has no clinical backing.

Who Should Be Cautious

The vasodilating action is potent enough that blood pressure can drop, so anyone already prone to low blood pressure should be wary. Injection-site redness, itching, or swelling is possible, and a small number of reports raise the possibility of effects on glucose metabolism in sensitive users.

Availability

B7-33 is currently sold as a research chemical and has not been approved by the FDA for human use. It is found mainly through specialized peptide suppliers and compounding pharmacies.

Bottom Line

The preclinical signal is consistent and the mechanism is reasonable, but with zero human trials the honest label here is experimental, not therapeutic.