What Is TB-500 (Thymosin Beta 4)?



TB-500 (a.k.a. thymosin beta-4 or TB-4) is a naturally occurring protein in the human body just like modified GRF 1-29. TB-500 is 43 amino acids in length and plays a critical role in the polymerization of actin, a filament found in most cells and on that is particularly important in muscle cells. TB-500 is currently being investigated for its potential role in reversing liver fibrosis and for its anti-aging effects.


How Does TB-500 Work?


Research suggests that TB-500 is an actin-binding protein. Actin is a primary constitute of the scaffolding (called microfilaments) that gives cells their shape and helps them to maintain the integrity of their membranes. It is also a major component of muscle sarcomeres where it provides the scaffolding against which another protein, myosin, acts. Without actin, there could be no muscle contraction.


Though the exact effects of TB-500 are not perfectly clear, it appears that TB-500 sequesters free actin and holds it within the cell, preventing it from being degraded or lost. TB-500 readily releases actin during polymerization, however. Polymerization is the process by which actin monomers are join to form actin polymers (microfilaments). Microfilaments are the functional form of actin.


TB-500 Effects


Interestingly, research indicates that thymosin beta 4 and most other thymosins play active roles in tissue regeneration. In other words, TB-500 appears to help cells recover after injury. As a result of its tissue-healing properties, TB-500 has been investigated for use in treating bed sores, skin ulcers, and severe conditions that lead to skin erosion. It has also been suggested the thymosin beta 4 may be useful in activating hepatic stellate cells, which are responsible for producing the extracellular structure of the liver. TB-500 may help to reverse or slow the course of liver fibrosis and protect against alcohol-induced liver disease by encouraging extracellular structure formation1,2 .


Thymosin beta 4 is a potent stimulator of muscle cell regrowth. Because muscle sarcomeres contain a great number of actin polymers, they benefit from having a ready supply of actin monomers with which to repair damage. Research in chicken embryos indicates that TB-500 promotes elongation of skeletal muscle cells, resulting in large muscles overall3 . It may be that thymosin beta 4 is capable of increasing muscle cell growth and repair rates.


TB-500 Summary


TB-500 is a natural protein found in the human body and in most vertebrates. Ongoing research suggests that it may be useful in encouraging tissue growth and healing. Current efforts are focusing on liver fibrosis and skeletal muscle repair. There is also some promise for the use of TB-4 in certain lung diseases.




  1. Kim, J. & Jung, Y. Potential role of thymosin Beta 4 in liver fibrosis. Int. J. Mol. Sci.16, 10624-10635 (2015).


  1. Lakshman, M. R. et al. Novel modulators of hepatosteatosis, inflammation and fibrogenesis. Hepatol. Int.8 Suppl 2, 413-420 (2014).


  1. Chankiewitz, V. et al. A thymosin beta15-like peptide promotes intersegmental myotome extension in the chicken embryo. Histochem. Cell Biol.141, 275-287 (2014).

What Is CJC-1295?



CJC-1295 is an analogue of growth hormone releasing factor (1-29) (GRF (1-29)) to which a moiety known as the Drug Affinity Complex has been attached. It is often abbreviated GRF-DAC or DACTM :GRF. CJC-1295 was created by ConjuChem Biotehcnologies in an effort to improve the plasma half-life of GRF (1-29).


Confusion with Modified GRF (1-29)


There is a great deal of confusion surrounding the relationship between CJC-1295 and modified GRF (1-29). The confusion arises due to the fact that modified GRF (1-29) is often sold under the name CJC-1295-No DAC. This is an inappropriate use of the CJC-1295 nomenclature.


CJC is short for ConjuChem Biotechnologies, the company that developed CJC-1295. Technically, CJC-1295 is GRF (1-29) to which the DAC (see below) complex has been added. Modified GRF (1-29) is GRF that has had four amino acids altered. Though CJC-1295-No DAC is used to refer to modified GRF (1-29) by a number of individuals, it is not accepted nomenclature. The best way to avoid confusion when dealing with these molecules and synthetic peptides is to look at their molecular structures and determine what each molecule is. Here are the structures of GRF (1-29), CJC-1295, and modified GRF (1-29). The differences between GRF (1-29) and the other two are in bold, italic, underlined text.


Structure of GRF (1-29):



Structure of CJC-1295-DAC:



Structure of Modified GRF (1-29) (a.k.a. CJC-1295-No DAC):



What Is DAC?


DAC is short for Drug Affinity Complex, a proprietary molecule developed by ConjuChem Biotechnologies to protect proteins that circulate in the bloodstream from metabolic degradation. DAC allows proteins to being to albumin, a normal blood protein. Once bound, the proteins are protected from enzymes in the blood that destroy peptides. DAC can extend the half-life of a peptide substantially. In the case GRF (1-29), DAC extends the half-life from 30 minutes to 30 hours.


What Does CJC-1295 Do?


Like GRF (1-29), CJC-1295 stimulates the release of growth hormone (GH) from the anterior pituitary gland. This, in turn, stimulates the release of insulin-like growth factor-1 (IGF-1) from the liver. The combined effects of GH and IGF-1 lead to cell hyperplasia (increase in number of cells) as well as cell hypertrophy (increase in size of cells). These combined effects increase muscle mass, increase bone density, lower blood sugar, improve fat metabolism and fat loss, increase protein synthesis, and improve myocardial (heart muscle cell) function.


Unlike GRF (1-29), CJC-1295 causes what is known as GH leak. GH leak refers to the fact that GH isn’t released in spurts, the standard physiologic release pattern, but rather is released at a high rate that tapers offer slowly over days. In other words, CJC-1295 causes a prolonged, non-physiologic release of growth hormone.


The tapering effect seen with GH that is released secondary to CJC-1295 is due to the fact that CJC-1295 has a far longer half-life than GRF (1-29) or growth hormone releasing hormone (the endogenous molecule from which GRF (1-29) is derived). Studies indicated that GH levels remain 2- to 10-fold higher for up to a week after CJC-1295 administration compared to GRF (1-29). IGF-1 levels remain elevated (1.5- to 3-fold) for roughly 11 days.


CJC-1295 Summary


CJC-1295 is a simply GRF (1-29) to which the Drug Affinity Complex has been bound. Its effects are identical to those of GRF (1-29), but last substantially longer (30 hours rather than 30 minutes). CJC-2195 is not the same molecule as modified GRF (1-29), though modified GRF (1-29) is sometimes incorrectly labeled as CJC-1295-No DAC.