A first-in-human, open-label, dose-escalation and dose-expansion phase I study to evaluate the safety, tolerability, pharmacokinetics/pharmacodynamics, and antitumor activity of QL1604, a humanized anti-PD-1 mAb, in patients with advanced or metastatic solid tumors.

Background: QL1604 is a humanized immunoglobulin G4 monoclonal antibody against programmed cell death protein 1. This first-in-human, open-label phase I study aimed to investigate the safety and tolerability and to identify the recommended doses of QL1604 for future studies. Pharmacokinetics/pharmacodynamics (PK/PD) and preliminary antitumor activity were also assessed. Methods: Patients with advanced or metastatic solid tumors who failed or had no standard therapies available were recruited. In the dose-escalation phase, patients were treated with QL1604 at 0.3 mg/kg, 1 mg/kg, 3 mg/kg, and 10 mg/kg intravenously once every 2 weeks (Q2W) in an accelerated titration with a traditional 3 + 3 design, followed by a dose-expansion phase at 3 mg/kg Q2W, 3 mg/kg once every 3 weeks (Q3W), 10 mg/kg Q2W and a fixed dose of 200 mg Q3W. Dose-limiting toxicities (DLTs) were assessed during the first 28 days after the first dose of study drug. Adverse events (AEs) were graded per National Cancer Institute Common Terminology Criteria for Adverse Events version 5.0, and antitumor activity of QL1604 was evaluated by investigators on the basis of Response Evaluation Criteria in Solid Tumors version 1.1. Results: A total of 35 patients with advanced or metastatic solid tumors were enrolled. DLTs were reported in one patient at the dose level of 3 mg/kg Q2W (grade 3 immune-mediated myositis and myasthenia gravis), and maximum tolerated dose was not reached. The most frequent treatment-related AEs (≥10%) were fatigue (37.1%), anemia (22.9%), increased blood thyroid-stimulating hormone (17.1%), increased aspartate aminotransferase (AST) (17.1%), increased alanine aminotransferase (ALT) (14.3%), decreased white blood cell (WBC) count (11.4%), rash (14.3%), and pruritus (14.3%). AEs leading to discontinuation of QL1604 occurred in three of the 35 patients (8.6%). Partial responses (PRs) occurred in seven patients, resulting in an objective response rate of 20.0% (7/35). Single dose of QL1604 exhibited a dose-dependent increase in the exposure ranging from 0.3 mg/kg to 10 mg/kg. Mean receptor occupancy (RO) for QL1604 at the dose of 3 mg/kg (Q2W and Q3W) and 200 mg (Q3W) was greater than 80% during cycle 1 after one infusion. Conclusion: QL1604 monotherapy exhibited favorable safety, PK, and signal of antitumor activity in patients with advanced or metastatic solid tumors, and the results supported further clinical studies of QL1604. On the basis of the safety, PK, and RO data, the recommended dosage for further clinical trials is 3 mg/kg or a fixed dose of 200 mg given every 3 weeks. Clinical Trial Registration: https://classic.clinicaltrials.gov/ct2/show/NCT05649761?term=QL1604&draw=2&rank=1, identifier NCT05649761.

Simultaneous isolation of mesenchymal stem cells and endothelial progenitor cells derived from murine bone marrow.

Mesenchymal stem or stromal cells (MSCs) are identified as sources of pluripotent stem cells with varying degrees of plasticity. Endothelial progenitor cells (EPCs) originate from either bone marrow (BM) or peripheral blood and can mature into cells that line the lumen of blood vessels. MSC and EPC therapies exhibit promising results in a variety of diseases. The current study described the simultaneous isolation of EPCs and MSCs from murine BM using a straightforward approach. The method is based on differences in attachment time and trypsin sensitivity of MSCs and EPCs. The proposed method revealed characteristics of isolated cells. Isolated MSCs were positive for cell surface markers, cluster of differentiation (CD)29, CD44 and stem cell antigen-1 (Sca-1), and negative for hematopoietic surface markers, CD45 and CD11b. Isolated EPCs were positive for Sca-1 and vascular endothelial growth factor receptor 2 and CD133. The results indicate that the proposed method ensured simultaneous isolation of homogenous populations of MSCs and EPCs from murine BM.

[Endothelial progenitor cells promote osteogenic differentiation of marrow stromal cells in a paracrine manner].

OBJECTIVE: To explore the mechanisms of endothelial progenitor cells (EPCs)on promoting osteogenic differentiation of marrow stromal cells (MSCs). METHODS: EPCs and MSCs were isolated and cultured successfully from C57BL/7 murine bone marrow by in vitro amplification. EPC-conditioned medium (CM) was extracted to detect the concentrations of vascular endothelial growth factor (VEGF), transforming growth factor-beta 1 (TGFß1), platelet-derived growth factor (PDGF), insulin-like growth factor 1 (IGF-1), stromal cell-derived factor 1 (SDF-1) and basic fibroblast growth factor (bFGF) by enzyme-linked immunosorbent assay (ELISA). After 14 days of induction, alizarin red staining was used to detect every group's calcium salt deposition. And analyses were conducted for the effects of above mentioned antibodies of cytokines on osteogenic differentiation of MSCs. RESULTS: Positive rates of EPCs were 79.3%, 79.5%, 76.4% for VEGFR2, CD34 and CD133 respectively, and EPCs could form tube-like structure on matrigel. EPCs secreted VEGF, TGFß1, PDGF, IGF-1, SDF-1 and bFGF. MSC/EPC group formed more mineralized nodules than MSC group, and semi-quantitative results showed the optical density of MSC/EPC group was higher than that of MSC group (0.733 ± 0.032 vs 0.236 ± 0.020, P < 0.001). The number of formed mineralized nodules of 50% EPC-CM group were more than those of 25% EPC-CM group, and semi-quantitative results showed that the optical density of 50% EPC-CM group was higher than that of 25% EPC-CM group (0.637 ± 0.028 vs 0.336 ± 0.024, P < 0.001), the number of formed mineralized nodules of 25% EPC-CM group were more than those of 0 EPC-CM group, and semi-quantitative results showed that the optical density of 25% EPC-CM group was higher than that of 0 EPC-CM group (0.336 ± 0.024 vs 0.239 ± 0.013, P = 0.004). On the basis of 50% of EPC-CM, the number of formed mineralized nodules significantly declined in the presence of anti-VEGF antibody, anti-TGFß1 antibody, anti-IGF-1 antibody (P < 0.01). CONCLUSION: EPCs promote osteogenic differentiation of MSCs probably through the paracrine effects of VEGF, TGFß1 and IGF-1.

Endothelial progenitor cells as a possible component of stem cell niche to promote self-renewal of mesenchymal stem cells.

Stem cells dwell at the "stem cell niche" to accomplish a series of biological processes. The composition of the niche should be determined because the insufficient understanding of this feature limits the development in the study of stem cells. We showed in our study on mesenchymal stem cells (MSCs) that the MSCs first neighbored to CD31(+) cells, which proved to be endothelial progenitor cells (EPCs), and formed a group of cell colony before they exerted their biological functions. It was further proved that EPCs have close interactions with MSCs and promoted the self-renewal of the MSCs in vitro and in vivo. Together with these achievements, we hypothesized that EPCs may be a possible biological component of the MSC stem cell niche and affect the biological processes of MSCs.