How does a human-cell discovery platform find brown-fat-building compounds?

Finding the Right Lock and Key

To make a new medicine, we first need a drug target. Think of the target as a specific lock on or in a cell, and the drug as the key. When the key fits the lock, it triggers a specific reaction.

For Energesis, the goal was to find a lock that triggers human adult stem cells to turn into active brown fat cells.

Using Biologically Meaningful Cells

Cells grown in a lab can behave differently than cells inside a living body. This is especially true if the lab cells are altered or "immortalized" to make them live forever. These modified cells do not copy real life very well.

To solve this, Energesis’ founders discovered real human brown fat stem cells. These cells naturally live in the walls of blood vessels throughout the body in the muscle mass, and they are physiological precursor cells to brown/beige/brite fat cells [1]. They can also be found in mice and non-human primates. We can easily collect and grow them in our lab. Because these cells are completely natural and unaltered, they provide a highly accurate model of how these cells work inside the human body.

Monitoring Cell Changes

We can easily watch these stem cells change, over a few days, into active, energy-dissipating brown fat cells. We can do this by looking for physical changes under a microscope, like the appearance of tiny fat droplets, or by tracking specific active genes, including that of Uncoupling Protein-1 (UCP1), the key functional protein that allows brown fat cells to burn stored energy.

Testing Thousands of Options Fast

To find the right drug, we put these stem cells into contact with large collections of different agents (chemicals, proteins or peptides) one at a time for a few hours or days. This process is called a phenotypic screen [2].

This screening method is fast and highly efficient. It allows scientists to instantly see which agents successfully trigger the stem cells to become active brown fat cells. If an agent works, we directly know three things:

• The agent reached its target inside or outside the cells
• The agent modified the activity of the target in the appropriate way (activation, inhibition, modulation) to have the effect we’re seeking
• The agent is not toxic or harmful to the cells

Unlocking New Discoveries

Once the screening process revealed which agents were successful, Energesis had to figure out exactly which cellular "locks" those agents were opening. By using several approaches in parallel, we successfully identified the targets. In the process, we discovered two entirely new drug targets that no one knew could create brown fat.

Testing in Living Bodies

After finding active agents in cell culture, we then tested the most promising compounds in mice which had developed obesity and pre-diabetes by eating a high-fat diet. These compounds increased the amount of brown fat in living animals, raised their resting energy expenditure, and reduced their body weight and body fat. The compounds also improved the animals’ glucose metabolism.

Perfecting the Medicine

Finally, through medicinal chemistry, Energesis took the original successful agents from the lab screen and modified them to create drug candidates that are much stronger and more selective, as they are more likely to target only the exact disease locks they are supposed to open. It is these drug candidates that we intend to study further to determine if they have the potential to treat obesity in patients.

Sources

1. Crisan M, Casteilla L, Lehr L, Carmona M, Paoloni-Giacobino A, Yap S, Sun B, Leger B, Logar A, Penicaud L, Schrauwen P, Cameron-Smith D, Russell AP, Peault B, Giacobino JP. A reservoir of brown adipocyte progenitors in human skeletal muscle. Stem Cells. 2008 Sep;26(9):2425-33.
2. Vincent F, Nueda A, Lee J, Schenone M, Prunotto M, Mercola M. Phenotypic drug discovery: recent successes, lessons learned and new directions. Nat Rev Drug Discov. 2022 Dec;21(12):899-914. doi: 10.1038/s41573-022-00472-w.