Perhaps the most fundamental of these gaps is the inherent biocompatibility of the MOF. Preclinical information on proposed materialsin addition to efficacy studiesrequires stability, biodistribution, and biocompatibility data. The screening is usually performed in a pipeline, starting with in vitro tests (e.g. examination of cytotoxic effects and performance on human cells), followed by animal in vivo studies (e.g. distribution, efficacy, immune response in several animal models); for clinical translation, this will culminate with several stages of clinical trials. Most studies pertaining to MOFs are limited to an in vitro stage, with very few in vivo studies reported to date. The first study was reported by Horcajada et al. in 2010 where, upon intravenous (i.v.) administration of Fe-centered MOFs to Wistar rats, no immune or inflammatory reactions were detected, hinting that these MOFs are well-tolerated. A more in-depth history of in vivo studies on MOFs has been presented in an excellent review by Ettinger et al. While these results suggest applicability of MOFs for drug delivery, the translational gap between animal and human outcomeswith statistics indicating that only 1 in 9 human trials are approved for clinical usage implies that these studies need to be scaled up or accelerated.