Murine-derived and patient-derived organotypic tumor spheroids (MDOTS/PDOTS) were prepared, cultured, and characterized as previously described (summarized in the Supplemental Material).[44 (link)] Immune cells were present from the initial tumor resection, and spheroid-collagen mixtures (10 μL, 2.5 mg/mL tumor spheroids) were injected into the center gel region of the AIM Dax-01 3D microfluidic culture device (AIM Biotech, Singapore). After incubation (30 minutes at 37°C) in sterile humidity chambers, collagen hydrogels containing MDOTS/PDOTS were hydrated with media (Dulbecco's modified Eagle's medium), with or without the indicated treatments. Treatments included the antibodies anti-human IFNγ (10 μg/mL), anti-mouse IFNγ (10 μg/mL) (both from Bio X Cell), anti-human PD-1 (pembrolizumab), and (S)-mepazine. Murine D4M.3A-derived tumor spheroids and MDOTS were cultured ex vivo with MPT-0308 (0.3-10 μM) for 4 days, and murine MC38-derived MDOTS were cultured with MPT-0308 (3 μM ± anti-mouse IFNγ) or anti-mouse IFNγ alone for 6 days. PDOTS established from patients with colorectal cancer (CRC) and melanoma were cultured ex vivo with MPT-0118 or MPT-0308 (3-5 μM [unless otherwise specified] ± anti-PD-1 [pembrolizumab]) for 5 to 7 days; one experiment additionally included each treatment plus or minus anti-human IFNγ.