PAM at the NMDA glycine/D-Serine binding site (Lanza & Makovec, 1997). D-Serine is released regionally during learning events; Neboglamine amplifies its binding at those moments, not continuously. Same design principle as TAK-653 being a better AMPA agent than agonists: allosteric bias makes enhancement context-dependent rather than constant.
The cascade: AMPA activation triggers delayed NMDA firing (NMDA currents rise as a delayed response to AMPA (Watt et al., 2004); AMPA trafficking is required for NMDA to function at all (Malinow & Malenka, 2002)), then Neboglamine amplifies NR2B binding at that NMDA step (Duffy et al., 2008). TAK-653 and Neboglamine hit sequential nodes in the same pathway, not the same point twice. The combination could push TAK’s ~7pt IQ effect considerably higher. Also reverses NMDA antagonist-induced cognitive impairment, as do AMPA PAMs (Ranganathan et al., 2017) and D-Serine (Karasawa et al., 2008).
More potent than D-Serine: ~50mg HED improves learning acquisition in healthy rats (Garofalo et al., 1996). D-Serine now thought to require >8g for cognitive effects, making Neboglamine a large practical improvement. One head-to-head comparison showed twice the NMDA activation potency (Lanza & Makovec, 1997) (dose discrepancy makes direct extrapolation rough, but the direction is clear). Glycine-site PAMs improve cognition in healthy young adults (Levin et al., 2015) and the elderly (Avellar et al., 2016).
Safer than D-Serine: D-Serine causes oxidative stress even at small amounts, not reversed by L-Serine in vitro (Da Silva et al., 2009). The indirect PAM mechanism avoids this entirely. Phase 1 demonstrated safety and tolerability; 200mg selected for maximum effects and demonstrated ischemia prevention at that dose.
Only drug with this mechanism.
Stacks well with TAK-653 (primary synergy, sequential AMPA→NMDA pathway nodes), ACD-856 (BDNF downstream of NMDA/NR2B activation)