This Study will first evaluate the safety and pharmacokinetics of a single intravenous dose of SEL-110, a nanoparticle containing rapamycin, in subjects with elevated blood uric acid levels. This will be followed, in separate subjects, by evaluation of the safety, pharmacokinetics, pharmacodynamics and immunogenicity of a single intravenous dose of SEL-212, SEL-037 (pegsiticase) plus SEL-110, in subjects with elevated blood uric acid levels. Uricase is an enzyme that converts uric acid to the readily soluble allantoin that is then excreted and SEL-110 is designed to prevent unwanted anti-drug-antibodies (ADAs) from forming. Cohorts of subjects in the SEL-110 only arms of the study will be given a single, ascending intravenous dose of SEL-110 and then monitored for safety and rapamycin levels (pharmacokinetics) over 30 days. Cohorts of subjects in the SEL-212 arms of the study will be given a single, ascending intravenous dose of SEL-110 with a fixed dose of SEL-037 and then monitored for safety, rapamycin levels, SEL-037 levels, uric acid levels and anti-drug-antibodies (ADAs) to SEL-037 for 30 days. One additional control group with receive a single intravenous infusion of SEL-037 at a fixed dose and then monitored for safety, SEL-037 levels, uric acid levels and anti-drug-antibodies (ADAs) to SEL-037 for 30 days
