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Start-ups

Syndeio Biosciences launches with molecules to target the synapse

Company’s lead candidate is already in a Phase 2 trial for major depressive disorder

by Sarah Braner
May 29, 2025

 

A chemical structure of zelquistinel.
Zelquistinel, Syndeio Bioscience’s main drug candidate, is thought to “reset” a target synapse, enabling that synapse to reconnect with its neighbors.

With $90 million in funding, Syndeio Biosciences has launched to target synaptopathies. These diseases and disorders, such as Alzheimer’s disease and major depressive disorder, are thought to result from damaged neural networks.

In addition to cash, the company has several assets in hand, including a lead drug candidate, zelquistinel, that is currently in Phase 2 clinical trials to treat major depressive disorder. Derek Small, the company’s cofounder and CEO, says zelquistinel will soon also enter a “synaptic biomarker trial” for Alzheimer’s disease.

Zelquistinel was originally developed by Naurex, a biotech company that Small led until its acquisition by Allergan in 2015. Allergan was later acquired by AbbVie, which has since licensed zelquistinel to Syndeio. AbbVie is a strategic shareholder of the new company, along with Eli Lilly and Company.

Small says that zelquistinel “resets” the synaptic ability of a target neuron by making that neuron more susceptible to glutamate. Glutamate triggers synaptic formation and strengthening in the brain, so if major depressive disorder is caused by neurons being unable connect with other neurons, this reset should treat the disorder.

Syndeio, which was formed by the merging of Gate Neurosciences and Boost Neuroscience, also owns Boost’s platform for predicting clinical outcomes and dosing strategies for its synaptogenic molecules. Small says the platform will help Syndeio advance and fine-tune the dosage of its drug candidates.

CORRECTION

This story was updated on June 2, 2025, to correct the structure of zelquistinel. The original structure provided by the company was updated to reflect the molecule's correct stereochemistry and tautomeric form. The drug candidate is an amide, not an imino alcohol.

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