The company carried out the trial at 12 sites in the US with 450 patients randomized to receive either ITI-007 60 mg or 40 mg or placebo once daily in the morning for four weeks.
Patients treated with 60 mg of ITI-007 drug showed improvement over placebo. However, the 40 mg dosage failed to achieve statistical significance.
ITI-007 60 mg once-daily met the primary and key secondary efficacy endpoints.
The company has also confirmed the pharmacology of ITI-007 in a separate positron emission tomography study.
It demonstrated antipsychotic effect at low striatal D2 receptor occupancy, lower than the occupancy range when compared to majority other antipsychotic drugs.
The company is also evaluating ITI-007 in another study to treat depression related with bipolar disorder.
Intra-Cellular Therapies chairman and CEO Sharon Mates said: "We are very encouraged by the positive results of our first Phase 3 trial. These data confirm the findings from our previous placebo- and risperidone active-controlled, randomized Phase 2 trial.
"The antipsychotic effect of 60 mg is confirmed and shows itself to be well-tolerated along with a safety profile similar to placebo.
"Patients deserve a treatment choice which gives them symptom relief without the associated movement disorders, metabolic disturbances or cardiovascular effects observed with many antipsychotics. We are excited about our progress towards delivering a novel treatment option for patients."
Intra-Cellular said schizophrenia is a disabling and chronic mental illness affecting more than 1% of population globally.