Four peptides and their biological starting materials
The common thread is borrowed biology. The molecules, alterations and clinical questions are quite different.
Original signals and resulting medicines
| Medicine | Biological starting material and clinical setting |
|---|---|
| Tesamorelin | A protected analogue of GHRH; FDA-approved for excess abdominal fat in adults with HIV-associated lipodystrophy. |
| Semaglutide | An altered GLP-1 analogue with albumin binding and resistance to enzymatic breakdown; studied across metabolic, cardiovascular and kidney outcomes. |
| Thymalfasin | A synthetic copy of thymosin alpha-1; studied in immune-related disease, with international approvals and no U.S. FDA approval. |
| Bremelanotide, or PT-141 | A cyclic alpha-MSH analogue; FDA-approved for acquired, generalized HSDD in premenopausal women. |
My favourite contrast here is between modifying a signal and copying one. Thymalfasin shows that reproducing the sequence still leaves a large clinical problem to solve. Semaglutide shows how deliberately changing a sequence and its attachments can be central to making a medicine.
Clinical comparisons
The head-to-head comparison of tirzepatide and semaglutide tested weight change in adults with obesity. It can compare those treatments for that question. The tesamorelin fat trials, the TESTS sepsis trial and the RECONNECT desire trials asked different questions in different populations.
A league table spanning all four would obscure their clinical purposes, in my estimation. A kidney event, a visceral-fat measurement and a desire score express different kinds of benefit. Their risks also need their own accounts: semaglutide’s digestive effects, tesamorelin’s growth-factor cautions, thymosin alpha-1’s uncertain applications and PT-141’s tolerability.