1：Experimental Design and Method Selection:

The study involved the synthesis of PEG conjugates of the zirconium ligand desferroxamine B (DFB) of similar size and charge to PLX038, containing one or four DFB as well as one that contained three SN-38 moieties and one DFB. Uptake and associated kinetic parameters of the 89Zr-labeled nanocarriers were determined in tumor and normal tissues in mice using μPET/CT imaging. The data were fit to physiologically-based pharmacokinetic models to simulate the mass-time profiles of distribution of conjugates in the tissues of interest.

2：Sample Selection and Data Sources:

MX-1 and HT-29 xenografts were used in female NCr nude mice. MX-1 cells were cultured in RPMI-1640, 10% FBS and 1% 2 mM L-glutamine at 37 °C in 95% air/5% CO2 atmosphere. HT-29 cells were cultured in McCoys5A supplemented with 10% FBS and P/S.

3：List of Experimental Equipment and Materials:

PEG40kDa-[CO2Su]4, PEG40kda-[NH2]4, branched PEG40kDa-NH2, 89Zr oxalate, ITCBz-DFB, and other commercially available chemicals were used. A μPET/CT scanner (Inveon, Siemens Medical Solutions, Malvern, PA) was used for imaging.

4：Experimental Procedures and Operational Workflow:

Mice were injected with NCs via the tail vein. μPET/CT scans were acquired at 1, 24, 48, 72, 96 and 216 hr post-injection. Mice were euthanized at 216 hr post-injection for biodistribution studies.

5：Data Analysis Methods:

PET data were acquired in list-mode, histogrammed, and reconstructed using the 2D ordered subset expectation–maximization algorithm that includes CT-based attenuation correction. Tissue and blood data were fit using physiologically-based pharmacokinetic models.