Background: Management of advanced gliomas including glioblastoma multiforme (GBM) remains as an unmet medical need. Here we report our clinical experience with ACT001, or dimethylamino micheliolide, a synthesized derivative from parthenolide (a natural product of sesquiterpene lactone class), in Han Chinese patients with advanced glioma. Methods: Adult patients were enrolled in a 3+3 dose escalation phase 1 study with the following pre-defined ACT001 cohorts: 100mg, 200mg, 400mg, 600mg and 900mg, twice a day (BID). Pharmacokinetics and adverse events were evaluated during the study. Imaging studies were performed using RANO criteria to assess the therapeutic afficacy. Results: 16 patients with advanced glioma were enrolled in this single agent dose escalation study including 8 primary GBM, 4 astrocytoma (grade 2-3) and 4 other advanced glioma. The median age was 49 years (range: 31-70). Safety evaluation was performed in five cohorts and 13 of the 16 subjecst were evaluable for drug tolerability analysis. ACT001 was tolerated very well and no DLT or MTD was identified. Other than grade 1 adverse reactions (AE) in most cases and grade 2 AEs in other clinical findings, no drug-related grade 3 AE was noted. Pharmacokinetic analysis indicates that there was approximately linear correlate between the drug exposure (C_max, AUC_0-t and AUC_0-inf) and study drug dosages evaluated. T_1/2 is 4 hours with mean Cmax increased from approximate 300ng/ml to 5000ng/ml in a dose dependent manner with no significant dose accumulation during repeated dosing challenge. Post baseline MRI scans were performed in 11 out of 16 subjects. Among these 11 subjects, 1 GBM patient had a partial response (PR) at end of cycle 2 but had disease progressed at end of cycle 4; two non-GBM patients had a stable disease (SD) lasting for 5 or 6 cycles respectively before being taken off study due to disease pregression (PD) and other 8 patients had a PD. Of note, 9 out of these 11 subjects had stable or even improved clinical performance by the time they were taken off study due to PD. Five other subjects withdrew their consents or were taken off study due to clinical disease progression. Of note, subject S12 with diffusive astrocytoma was taken off study due to PD while still with a stable clinilcal performance and stereotactic biopsies targeting the progressed lesion didn’t reveal viable tumor tissues other than presence of macrophage/microglia. This subject was still alive 666 days after being taken off study. The mode of ACT001 actions is proposed to be at least partially related to its effects on tumor immune microenvironment. Conclusions: ACT001 was safe and tolerated well in patients. Clinical response was observed including a pathologic response in a subset of patients dosed at lower dose cohorts. iRANO criteria will be used in future studies based on its impacts on tumor immune microenvitonment. Clinical trial information: ChiCTR-OIC-17013604.