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Cellular therapies offer a promising therapeutic strategy for the highly malignant brain tumor, glioblastoma (GBM). However, their clinical translation is limited by the lack of effective target identification and stringent testing in pre-clinical models that replicate standard treatment in GBM patients. In this study, we show the detection of cell surface death receptor (DR) target on CD146-enriched circulating tumor cells (CTC) captured from the blood of mice bearing GBM and patients diagnosed with GBM. Next, we developed allogeneic "off-the-shelf" clinical-grade bifunctional mesenchymal stem cells (MSC Bif ) expressing DR-targeted ligand and a safety kill switch. We show that biodegradable hydrogel encapsulated MSC Bif (EnMSC Bif ) has a profound therapeutic efficacy in mice bearing patient-derived invasive, primary and recurrent GBM tumors following surgical resection. Activation of the kill switch enhances the efficacy of MSC Bif and results in their elimination post-tumor treatment which can be tracked by positron emission tomography (PET) imaging. This study establishes a foundation towards a clinical trial of EnMSC Bif in primary and recurrent GBM patients., (© 2022. The Author(s).)

Background: Programmed cell death protein 1 (PD-1) antibody treatment is standard of care for melanoma and non-small-cell lung cancer (NSCLC). Accurately predicting which patients will benefit is currently not possible. Tumor uptake and biodistribution of the PD-1 antibody might play a role. Therefore, we carried out a positron emission tomography (PET) imaging study with zirconium-89 ( 89 Zr)-labeled pembrolizumab before PD-1 antibody treatment., Patients and Methods: Patients with advanced or metastatic melanoma or NSCLC received 37 MBq (1 mCi) 89 Zr-pembrolizumab (∼2.5 mg antibody) intravenously plus 2.5 or 7.5 mg unlabeled pembrolizumab. After that, up to three PET scans were carried out on days 2, 4, and 7. Next, PD-1 antibody treatment was initiated. 89 Zr-pembrolizumab tumor uptake was calculated as maximum standardized uptake value (SUV max ) and expressed as geometric mean. Normal organ uptake was calculated as SUV mean and expressed as a mean. Tumor response was assessed according to (i)RECIST v1.1., Results: Eighteen patients, 11 with melanoma and 7 with NSCLC, were included. The optimal dose was 5 mg pembrolizumab, and the optimal time point for PET scanning was day 7. The tumor SUV max did not differ between melanoma and NSCLC (4.9 and 6.5, P = 0.49). Tumor 89 Zr-pembrolizumab uptake correlated with tumor response (P trend = 0.014) and progression-free (P = 0.0025) and overall survival (P = 0.026). 89 Zr-pembrolizumab uptake at 5 mg was highest in the spleen with a mean SUV mean of 5.8 (standard deviation ±1.8). There was also 89 Zr-pembrolizumab uptake in Waldeyer's ring, in normal lymph nodes, and at sites of inflammation., Conclusion: 89 Zr-pembrolizumab uptake in tumor lesions correlated with treatment response and patient survival. 89 Zr-pembrolizumab also showed uptake in lymphoid tissues and at sites of inflammation., Competing Interests: Disclosure MJ reports consultancy fees from AstraZeneca (paid to UMCG). JBH reports consultancy roles for Achilles Therapeutics, BioNTech, BMS, GSK, Immunocore, Instil Bio, Molecular Partners, MSD, Merck Serono, Neogene Therapeutics, Novartis, Pfizer, PokeAcel, Roche/Genentech, Sanofi, T-Knife, and Third Rock Ventures and research grants from Amgen, Asher-Bio, BMS, BioNTech, MSD, Novartis, and Neogene Therapeutics (paid to the Netherlands Cancer Institute). WT reports fees from Merck, Sharp, Dohme, and Bristol-Myers-Squibb (paid to UMCG). EGEdV reports an advisory role at Daiichi Sankyo, NSABP, and Sanofi and research funding from Amgen, AstraZeneca, Bayer, Chugai Pharma, Crescendo, CytomX Therapeutics, G1 Therapeutics, Genentech, Nordic Nanovector, Radius Health, Regeneron, Roche, Servier, and Synthon (paid to UMCG). GAPH reports consulting and advisory role at Amgen, Roche, MSD, BMS, Pfizer, Novartis, and Pierre Fabry and research funding from BMS and Seerave (paid to UMCG). TJNH reports consultancy fees (paid to UMCG) from BMS, MSD, Merck, Boehringer, AstraZeneca, and Roche. AJvdW reports an advisory role at Janssen, Takeda, and Boehringer-Ingelheim (paid to UMCG) and research funding from AstraZeneca, Boehringer-Ingelheim, Pfizer, Roche, and Takeda. MNL-dH reports research funding from Merck, Bayer, and Amgen (paid to UMCG). HJMG reports an advisory role at Eli Lilly, MSD, BMS, and Novartis. All other authors have declared no conflicts of interest., (Copyright © 2021. Published by Elsevier Ltd.)