Compound description
What is TAK-653
TAK-653 (later assigned the international nonproprietary name Osavampator, Neurocrine Biosciences development code NBI-1065845) is a synthetic positive allosteric modulator of AMPA receptors developed by Takeda.
Why the AMPA receptor. Ketamine produces a rapid antidepressant effect in treatment-resistant depression, but comes with psychotomimetic side effects — dissociation, hallucinations. The mechanism behind this effect is indirect: ketamine blocks NMDA receptors on GABAergic interneurons, disinhibiting glutamatergic neurons; the released glutamate, with NMDA blocked, preferentially activates AMPA receptors and triggers a BDNF-mediated mTOR cascade — the basis of the rapid antidepressant effect. The logical next step is to reach that same cascade directly through AMPA, without first needing to block NMDA and without ketamine's side effects.
The dilemma of earlier attempts. AMPA potentiators have been in development since the 1990s, and no compound in the class has reached registration yet. The reason is an unresolved dilemma. "Low-impact" ampakines (CX516, CX717) proved safe but insufficiently potent: due to low activity and a short half-life, they showed no convincing effect in ADHD, dementia, or schizophrenia. More potent potentiators (CX691, Org26576, LY451395, S18986, S47445) gave a better efficacy signal — but had intrinsic agonist activity (the ability to activate AMPA-R on their own, without glutamate), which narrowed their safety margin against seizures.
TAK-653's solution. The molecule binds the AMPA receptor ligand-binding domain in a glutamate-dependent manner, enhancing Ca²⁺ current through a structural interaction with Ser743 on the GluA1 subunit — but has minimal intrinsic agonist activity of its own. This resolves the dilemma from both sides at once: a wider range of effective doses and a substantially lower seizure risk than any earlier compound in the class.
Preclinical evidence. In rats, TAK-653 improved both working and recognition memory (the reference compound LY451646 improved only recognition memory; AMPA improved neither). In primates, it improved accuracy on a delayed match-to-sample task. In a depression model (RSBM), it produced an antidepressant-like effect without the hyperlocomotion characteristic of ketamine.
Confirming target engagement in humans. Takeda/Neurocrine developed TMS as the first translational biomarker for AMPA potentiators: TAK-653 increased motor evoked potential amplitude in humans in the same way it increased mechanomyographic response in rats. The NeuroCart battery confirmed a psychostimulant-like profile — objectively measurable, but not subjectively felt on any scale.
Clinical efficacy. In the Phase 2 SAVITRI trial (183 adults with depression), the 1 mg/day dose produced a statistically significant reduction in MADRS: −4.3 points versus placebo on Day 28 (p=0.0159), −7.5 points on Day 56 (p=0.0016). The most common adverse effects were headache and nasopharyngitis, at placebo-level rates. In January 2025, Neurocrine initiated a Phase 3 registrational program.
Evidence base
All available research on TAK-653
Minimal agonist activity — the key mechanism
More effective than earlier PAMs
Binds the AMPA receptor ligand-binding domain in a glutamate-dependent manner, enhancing Ca²⁺ current via interaction with Ser743 on GluA1. Improved both working and recognition memory in rats (LY451646 improved only recognition memory, AMPA neither) and delayed match-to-sample accuracy in monkeys.
Antidepressant-like effect without hyperlocomotion
Without ketamine's side effects
Increased phosphorylated (active) mTOR, p70S6K, Akt and ERK and BDNF protein levels. Produced an antidepressant-like effect in the RSBM model — similar to ketamine. Unlike ketamine, did not cause hyperlocomotion, a behavioral marker linked to psychotomimetic side effects.
First translational biomarker for AMPA potentiation (TMS)
New biomarker
Increased both the mechanomyographic response to TMS in rats and motor evoked potential amplitude in humans, at doses with equivalent plasma concentrations. The first published translational biomarker for AMPA receptor potentiation.
Psychostimulant-like profile on the NeuroCart battery
No signs of abuse potential
6 mg improved adaptive tracking and increased saccadic peak velocity and smooth pursuit; 0.5 mg affected the Stroop task. Body sway and subjective visual analogue scale ratings were unchanged — an objectively measurable effect without a subjective "high".
Reversal of depressive-like behavior in primates
First confirmation in primates
After the stress protocol, monkeys showed reduced motivation, increased anxiety, and elevated cortisol and IL-6. After 2 weeks of treatment: improved motivation and activity, reduced cortisol and IL-6, increased BDNF.
First human study: safety and tolerability
Phase 1 · well tolerated
Single doses of 0.3–18 mg and repeated doses of 0.3–9 mg/day for 13 days, 66 vs 22 on placebo. Well tolerated at all doses; no serious adverse events, including seizures, were reported.
Does not induce CYP3A — safe alongside oral contraceptives
No drug interactions
Concentrations of midazolam (a sensitive CYP3A substrate) and oral contraceptive components were not significantly altered. Can be combined with oral contraceptives and other CYP3A substrates without dose adjustment.
Significant improvement in depression versus placebo
Phase 2 · positive result
The 1 mg dose produced a MADRS reduction versus placebo of −4.3 points (Day 28, p=0.0159) and −7.5 points (Day 56, p=0.0016). The 3 mg dose showed only a trend without statistical significance. The most common adverse events were headache and nasopharyngitis, at placebo-level rates.
Phase 3 registrational program initiated
Phase 3 · ongoing
Building on positive Phase 2 SAVITRI data, Neurocrine initiated a Phase 3 registrational program in January 2025 — five studies at once.
