Here is link to the phase II for bitopterin the roche drug however I also saw a report that suggests its not doing so well in phase III although they are not fully completed....there is a very high placebo rate like 40% efficacy so that's kind of hard to beat..

JAMA Network | JAMA Psychiatry | Effect of Bitopertin, a Glycine Reuptake Inhibitor, on Negative Symptoms of Schizophrenia: A Randomized, Double-Blind, Proof-of-Concept Study

Anyway same mechanism as for sarcosine...so it may or may not work and it may work better in some people than others..