Selank: The Peptide Built From a Piece of the Immune System

Your immune system and your mood seem like two very different worlds. Selank sits right between them. It started as a tiny piece of an antibody, one of the immune system's defenders.

Scientists in Moscow took that piece and added a short tail. The new peptide has been studied mainly for anxiety.

What it is

Amino acids are the building blocks of proteins. Think of them as beads. A peptide is a short string of beads, like a small bracelet. For the basics, see what a peptide is.

Selank is a lab-made chain of just seven beads. The first four are tuftsin. Tuftsin is a natural piece of the most common antibody in human blood. It was described in 1970 at Tufts University, which gave it its name. It helps immune cells swallow bacteria.

The last three beads are an added tail. Enzymes are the body's tiny scissors that cut peptides apart. The tail helps Selank resist those scissors.

Its sibling, Semax, has the same tail. Semax starts from a piece of a hormone instead.

What it does in the body

In lab and animal work, Selank touches a few systems at once. Think of a tuner, not an on-off switch.

The main one is GABA. GABA is the brain's main calming messenger. It works by fitting into receptors on nerve cells. A receptor is like a lock, and GABA is the key.

The second is enkephalins. These are the body's own small opioid-like peptides, tied to mood and stress.

What scientists have found

In cells: In a lab test with human blood, Selank slowed the enzymes that break enkephalins apart. It beat the usual lab test compounds by a wide margin. Shorter pieces of Selank did nothing, so the whole chain seems to matter.

On membranes taken from brain cells, Selank changed how well GABA binds to its receptor. It acted like a dimmer, not a light switch.

In human nerve-like cells in a dish, Selank alone did not change any of 69 GABA-related genes. But paired with another medicine, it changed more genes than that medicine did alone. So Selank may boost what other signals do.

In animals: In rats, one treatment with Selank shifted dozens of genes in the front of the brain an hour later. Genes are like recipe cards inside a cell. Some GABA receptor genes dropped sharply, then rose by the three-hour mark. The early pattern looked a lot like what GABA itself did. The team called the work exploratory.

In another study, rats faced ongoing mild, random stress. Then they were tested on a raised, cross-shaped maze. More time on its open arms is read as less anxious behavior. Rats given Selank together with diazepam, a calming medicine, kept their anxiety measures at pre-stress levels.

In people: Selank has some human studies, which is rare for a peptide like this. They are small and mostly published in Russian.

In a 2008 trial, 62 people with anxiety or long-lasting tiredness got either Selank or a benzodiazepine, a common calming medicine. Anxiety scores improved by similar amounts in both groups. The Selank group also had less fatigue, not more drowsiness. During Selank treatment, enkephalins lasted longer in the blood, mostly in those with anxiety.

In a 2015 study, 70 people with anxiety took another calming medicine. Forty of them also got Selank. That group improved sooner on a rating scale and reported fewer side effects from the first medicine.

Neither study compared Selank with a placebo, a dummy treatment.

Where it stands

Selank is an approved medicine in Russia, used for anxiety disorders. It is not approved by the FDA.

Most research still comes from a few Moscow labs. Scientists want to know exactly where Selank binds on the GABA receptor. They also want to know if the enkephalin effect seen in blood happens in the brain too.

The exciting next step is large, blinded trials in people with a placebo group. In a blinded trial, no one knows who got the real thing until the end. It is early days, and Selank is one to watch.

The bottom line

• Selank is a chain of seven amino acids: an antibody piece called tuftsin, plus a three-bead tail.
• In lab and rat studies, it acted like a tuner for GABA, the brain's calming messenger, and in lab tests it slowed enzymes that break down enkephalins.
• Two small Russian studies in people looked at anxiety. Neither one compared Selank with a placebo.