The honest answer
The 'get the repair crew to the site' peptide.
Short answer
TB-4 (thymosin beta-4) is a peptide studied in preclinical research for cell migration — helping repair cells move into damaged tissue. In BPC Matrix it sits on top of the BPC-157 base to cover that step of the process. Studied, not proven; individual results vary.
If BPC-157 is about blood supply, TB-4 has been studied around getting repair cells to where the damage is. Different job, same goal.
One peptide covers one part of repair; the blend covers more of the chain. See why the blend.
Straight answers
They're closely related — TB-500 is a synthetic version discussed in similar contexts. BPC Matrix uses TB-4 as one of its four peptides.
No — it is not an FDA-approved drug and is physician-supervised.