Bridging the gap between findings in preclinical 2D cell culture models and in vivo tissue cultures has been challenging; the simple microenvironment of 2D monolayer culture systems may not capture the cellular response to drugs accurately. Three‐dimensional organotypic models have gained increasing interest due to their ability to recreate precise cellular organizations. These models facilitate investigation of the interactions between different sub‐tissue level components through providing physiologically relevant microenvironments for cells in vitro. The incorporation of human‐sourced tissues into these models further enables personalized prediction of drug responses. Integration of microfluidic units into the 3D models can be used to control their local environment, dynamic simulation of cell behaviors, and real‐time readout of drug testing data. Cancer and immune system related diseases are severe burdens to our health care system and have created an urgent need for high‐throughput, and effective drug development plans. This review focuses on recent progress in the development of “cancer‐on‐a‐chip” and “immune organs‐on‐a‐chip” systems designed to study disease progression and predict drug‐induced responses. Future challenges and opportunities are also discussed.

Transdermal delivery of water‐insoluble drugs via hydrogel‐based microneedle (MN) arrays is crucial for improving their therapeutic efficacies. However, direct loading of water‐insoluble drug into hydrophilic matrices remains challenging. Here, a biodegradable MN array patch that is fabricated from naturally derived polymer conjugates of gelatin methacryloyl and β‐cyclodextrin (GelMA‐β‐CD) is reported. When curcumin, an unstable and water‐insoluble anticancer drug, is loaded as a model drug, its stability and solubility are improved due to the formation of an inclusion complex. The polymer‐drug complex GelMA‐β‐CD/CUR can be formulated into MN arrays with sufficient mechanical strength for skin penetration and tunable drug release profile. Anticancer efficacy of released curcumin is observed in three‐dimensional B16F10 melanoma models. The GelMA‐β‐CD/CUR MN exhibits relatively higher therapeutic efficacy through more localized and deeper penetrated manner compared with a control nontransdermal patch. In vivo studies also verify biocompatibility and degradability of the GelMA‐β‐CD MN arrays patch.