Bitopertin
glutamatergic · negative symptoms (motivation, social engagement) class / glutamatergicspec sheet6 rows
Bitopertin was Roche's flagship glycine reuptake inhibitor and, for a while, the most closely watched drug in the whole NMDA-hypofunction theory of schizophrenia. By blocking the glycine transporter GlyT1, it raises synaptic glycine, which acts as a required co-agonist at the NMDA receptor's glycine site; the goal was to boost NMDA signaling from the outside rather than dosing glycine itself. A 2014 Phase II proof-of-concept study reported genuine improvement in the stubborn negative symptoms of schizophrenia (flat affect, social withdrawal, low motivation), a domain existing antipsychotics barely touch. Roche then ran an enormous six-trial Phase III program; two of the pivotal studies missed their primary endpoint and a third was stopped early for futility, and by 2016 the whole negative-symptoms indication was abandoned. It stands as one of the largest and most expensive schizophrenia trial failures on record.
- improved PANSS negative symptom factor scores in Phase II proof-of-concept
- novel mechanism distinct from dopamine-blocking antipsychotics
- well tolerated with a relatively clean side-effect profile in trials
- Roche's bitopertin Phase III program ran six separate pivotal trials at once, one of the largest simultaneous trial commitments ever made to a single schizophrenia drug candidate.
Mechanism
Selective GlyT1 (glycine transporter 1) inhibitor; raises extracellular glycine at glycine co- sites to enhance neurotransmission.
Dosingtypical ranges, not medical advice
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Safetyrisks and cautions, not medical advice
Glycine is a raw material for haem, so blocking its transport lowers haemoglobin; that is the one reproducible finding in bitopertin's safety record and it is dose-dependent. In a 52-week Japanese schizophrenia study haemoglobin drifted down with dose, though nobody fell below 10 g/dL or stopped because of it, while somnolence and insomnia also rose with dose. That same effect is now the therapeutic point, since bitopertin is in active development for erythropoietic protoporphyria. Anyone already anaemic or carrying a blood disorder is the group for whom the haemoglobin effect stops being a laboratory curiosity.
History
Developed by Roche; positive Phase II proof-of-concept in 2014 (Umbricht et al, JAMA Psychiatry) drove a large Phase III program (FlashLyte, DayLyte, SunLyte, and others); multiple pivotal trials failed to meet primary endpoints by 2016 and the schizophrenia program was discontinued.
Subjective profileweighing the evidence above
The best-tested version of the glycine/NMDA hypothesis for negative symptoms, and it still couldn't clear Phase III at scale.
Resources
This entry is here for reference.
Research
1 listed here; entry last updated July 2026
Reviews
My notesprivate to this device
FAQ
Why did bitopertin fail after such a promising start?
The Phase II signal on negative symptoms didn't hold up in the much larger Phase III program; several pivotal trials missed their primary endpoint and one was stopped early for futility.
Is bitopertin related to sarcosine?
They work on the same target. Sarcosine is a natural amino acid that weakly inhibits GlyT1; bitopertin is a purpose-built, far more potent synthetic GlyT1 inhibitor from the same drug class.
Limitations of the evidence
- no reliable benefit replicated in Phase III
Notes and cautions
- dose-response was inverted U-shaped, complicating dosing (lower doses outperformed higher ones)
- as an oral add-on drug, still required background antipsychotic treatment