CRLX101 (formerly IT-101) is a novel cyclodextrin-based polymer that self-assembles into nanoparticles. CRLX101 is covalently conjugated to the hydrophobic topoisomerase 1 (TOP1)-inhibitor camptothecin (CPT) resulting in stabilized structure and increased water solubility. Extensive preclinical studies of CRLX101 demonstrated delayed renal clearance and a prolonged plasma half-life. The nanoparticle passively accumulates in tumour tissue through the enhanced permeability and retention effect and slowly releases active CPT leading to enhanced TOP1 inhibition, potential hypoxia inducible factor-1a (HIF-1a) effect, cancer stem cell targeting, and increased antitumour activity against multiple human tumour xenografts. More than 200 human cancer patients have been treated with CRLX101 in phase I/IIa and phase II clinical trials. In this chapter we explore a wide range of anti-cancer nanotherapeutic strategies to inhibit TOP1, HIF-1a and cancer stem cells. Moreover, we discuss the therapeutic value of combining HIF-1a inhibition with antiangiogenics. Finally, we return to CRLX101 and cover in detail the latest preclinical and clinical evaluations and discuss future directions.