Background: Glioblastoma (GBM) is the most common primary and aggressive malignant brain tumor in adults. Almost all patients with glioblastoma eventually have disease relapse and the median overall survival (OS) remains at only 30 weeks for those recurrent GBM patients. However, very few therapies had been approved over the past two decades, emphasizing the need for novel treatments. It is now wildly acknowledged that the immune microenvironment in brain offers adequate opportunities to implement immunotherapy for the treatment. Since most recurrent tumors had previously been exposed to the genotoxic stress of irradiation and/or chemotherapy, it is predicted to resulted in a higher mutational load and more immunogenic. However, The limited success of T cell immunomodulatory approach for advanced glioma has prompted a deeper understanding of the brain tumor and the immune microenvironment. GBM tumors are well-appreciated to be a immunosuppressive and a hallmark of GBM immunosuppression is the appearance of circulating myeloid-derived suppressor cells (MDSCs) at higher levels. Our preliminary data suggests that HF1K16, a liposome ATRA (all trans retinoic acid) suspension, is capable of relieving immune suppression induced by MDSCs. Further, we recently completed a phase I dose escalation study which showed that HF1K16 is safe, well-tolerated with preliminary efficacy in brain tumor. Thus, we hypothesized that HF1K16 may reverse GBM-associated immune suppression and leading to an increase in TILs and improved survival. Methods: This is an advanced glioma-specific expansion arm for adult patients with prior confirmed brain tumor and failed standard treatment. We plan to enroll 20~30 evaluable patients. Key eligibility criteria include candidates age ≥ 18 years, Karnofsky performance status ≥ 60 with and at least one measurable lesion. The primary endpoint is determination of overall response rate (ORR), duration of response (DOR), disease control rate (DCR) and progression-free survival (PFS) according to RANO criteria. Secondary endpoints include longitudinal assessment of the peripheral immune response by changes in MDSC and T cell subsets and numbers. HF1K16 infusions were administered in 21-day cycles (q.o.d days 1-14). Prior to and during treatment, peripheral blood mononuclear cells were collected and analyzed with flow cytometry to monitor the changes in myeloid cell phenotype and T cell composition. The recruitment of patients is anticipated completed in 2024. Clinical trial information: NCT05388487.