For a study, researchers sought to understand that ONC201 was a topic DRD2 antagonist that had demonstrated preclinical activity in desmoplastic small round cell tumors (DSRCT). This investigator-initiated trial treated 30 patients with neuroendocrine tumors (NCT03034200). ONC201 dose and schedule were 625 mg orally weekly in cohort A (PC-PG) + B (other neuroendocrine tumors) and 625 mg twice a week in cohort C (5 responding patients). The primary endpoint was RECIST-measured radiographic response. Progression-free survival, overall survival, and safety were all secondary endpoints. In arm A (n=10; all PC-PG), 50% (5/10) had a partial response (PR), and 2 additional patients had stable disease (SD) for more than 3 months. The median duration of therapy for arm A patient was 9 months (range: 1.5–33 months), with 5 patients receiving treatment for more than 1 year. There was 1 PR (DSRCT) and 2 SD (DSRCT; neuroblastoma) for more than 3 months in arm B (n=12). The median duration of therapy in arm A was 18 months (range: 1–33 months), and the median duration in arm B was 3 months (range: 1.5–33 months). At 3 months, Arm C PC-PG (N=8) showed 1 PR and 7 SD, with a median duration of therapy of more than 10 months. At week 12, there was no decline in Karnofsky’s performance status for 28 of 30 patients, and there was no dose modification due to treatment-related adverse events. Oral ONC201 was well tolerated in patients with metastatic neuroendocrine tumors and was associated with clinical benefits, including tumor responses, in some DSRCT patients and most PC-PG patients.