Abstract: The development of a new, targeted drug delivery paradigm coupled to improved PI3K inhibitors (e.g., PI3K? inhibitors) represents a significant advance in cancer therapy. Provided herein are compounds, such as compounds of Formula (I) and (II), and pharmaceutically acceptable salts, hydrates, solvates, polymorphs, co-crystals, tautomers, stereoisomers, isotopically labeled derivatives, and prodrugs thereof. The compounds provided herein are PI3K (e.g., PI3K?) inhibitors and are therefore useful for the treatment and/or prevention of various diseases (e.g., proliferative diseases such as cancer). Also provided herein are nanoparticles and nanogels (e.g., P-selectin targeting nanoparticles) comprising PI3K inhibitors, such a compound described herein. In certain embodiments, a nanoparticle or nanogel described herein encapsulates a compound described herein for targeting delivery to cancer cells or tumors.