Is Relaxin-2 legal in the United Kingdom?

The pregnancy hormone that opens the circulation. A 1,161 patient phase 3 trial reported 42 deaths against 65 on placebo at 180 days as an additional endpoint, and the 6,545 patient confirmatory trial found cardiovascular death of 8.7 percent against 8.9 percent, hazard ratio 0.98. Serelaxin was never approved and development for acute heart failure stopped.

Relaxin-2 is a two-chain peptide hormone of the insulin superfamily, made by the corpus luteum and the placenta, and it is the reason a pregnant woman's cardiac output rises and her blood vessels and kidneys relax. That physiology is not in question and it is a perfectly good reason to have wondered whether the same hormone could help a failing heart.

Mechanism: Relaxin-2 acts at RXFP1, a G protein-coupled receptor, and produces systemic vasodilation, increased cardiac output, increased renal blood flow and increased arterial compliance, largely through nitric oxide and cyclic AMP dependent pathways, together with anti-fibrotic signalling that has been the focus of most later work. It is a two-chain molecule held together by disulfide bonds, built like insulin, which is why it is hard and expensive to manufacture and why simplified single-chain analogues were designed.

Regulatory history: Relaxin-2 is an endogenous hormone. Serelaxin, its recombinant form, is not approved by the FDA or any other regulator. It received attention after the RELAX-AHF result but the confirmatory RELAX-AHF-2 trial failed both primary endpoints and development for acute heart failure was discontinued.

Licenses medicines for the UK market. A compound without a marketing authorisation is an unlicensed medicine, which can only lawfully be supplied for human use through a prescriber under the specials scheme, not sold as a research product.

The classification above is the The Longevity Archive reading of Medicines and Healthcare products Regulatory Agency listings for Relaxin-2 at the reviewed date, not a legal opinion. Rules change, and importing, prescribing and possessing a compound can each be treated differently. Check the regulator directly before acting on anything here.