NAX-5055

Galanin is a powerful endogenous anticonvulsant whose receptors, GalR1 and GalR2, are concentrated in the hippocampus and other limbic structures that generate and propagate seizures. The therapeutic barrier has always been delivery: the native peptide neither survives in plasma nor crosses the blood-brain barrier. NAX-5055 was engineered to solve both problems. Starting from truncated galanin, non-essential residues were replaced with cationic and lipoamino-acid residues, and the analog that emerged, designated Gal-B2, carries a distinctive Lys-Lys-Lys(palmitoyl)-Lys amide motif that confers metabolic stability and membrane permeability while retaining high affinity for galanin receptors (Ki around 3.5 nanomolar at GalR1 and about 51 nanomolar at GalR2, a GalR1-preferring profile) ^[1].

In efficacy testing, NAX-5055 blocked seizures in the Frings audiogenic mouse, the corneal kindling model of partial epilepsy, and the 6 Hz model of pharmacoresistant epilepsy, where it retained potency across all three stimulation currents, a hallmark suggestive of activity against treatment-resistant seizures ^[2]. Notably it was inactive in the traditional maximal electroshock and subcutaneous pentylenetetrazol tests, giving it a screening profile distinct from most marketed antiepileptics. It was active after intravenous, intraperitoneal, and subcutaneous administration with a linear pharmacokinetic profile, supporting genuine systemic engagement of central receptors ^[2].

A key liability was uncovered when systemic NAX-5055 was found to raise blood glucose and impair insulin release through peripheral GalR1, an effect that persisted with repeated dosing and did not occur with a scrambled control analog, confirming it was mediated by galanin-receptor engagement rather than by the chemical modifications themselves ^[3]. This on-target hyperglycemia, together with the desire to separate central anticonvulsant effects from peripheral metabolic ones, motivated the design of GalR2-preferring successors such as NAX 810-2. NAX-5055 remains an important investigational lead and a validation that engineered neuropeptides can act centrally after peripheral dosing.

The principal identified liability of NAX-5055 is dose-dependent hyperglycemia and impaired insulin release driven by peripheral GalR1 activation, demonstrated in mice after both acute and repeated dosing. This metabolic effect is intrinsic to GalR1 agonism rather than to the analog's chemistry. Human safety has not been established, as development did not reach clinical trials in the public record. As an engineered peptide it also carries the general uncertainties of peptide therapeutics, including potential immunogenicity and injection-site effects, none of which have been formally studied in humans.

NAX-5055 was developed in the late 2000s by Grzegorz Bulaj, H. Steve White, and colleagues at the University of Utah, with the analog first reported in 2008 and its epilepsy profile detailed in 2009. The program applied a rational strategy of cationization plus lipidization to overcome galanin's delivery limitations, and the compound was advanced by the university spin-out NeuroAdjuvants. It became the flagship example of a systemically active galanin analog and the template from which GalR1-versus-GalR2 selectivity was subsequently engineered.

Among epilepsy researchers NAX-5055 is regarded as a landmark demonstration that a neuropeptide anticonvulsant could be delivered systemically, and it is frequently cited as a first-in-class concept for treatment-resistant epilepsy. Its metabolic liability tempered enthusiasm and redirected the field toward GalR2-preferring analogs. It has no presence in consumer or nootropic markets and remains an investigational research compound.