In 2025, it will be 30 years since the initial clinical approval of pegylated liposomal doxorubicin (PLD) by the Food and Drug Administration. PLD predated the field of nanomedicine and became a model nanomedicine setting key pharmacological principles (prolonged circulation, slow drug release and the enhanced permeability and retention (EPR) effect) for clinical application of other nano-drugs in cancer therapy. The impressive reduction of cardiotoxicity conferred by PLD is the most valuable clinical asset. While PLD has gained a strong foothold in relapsed ovarian cancer and metastatic breast cancer, it has not been extensively tested in primary (neoadjuvant) and adjuvant therapy and has not fulfilled the expectations from the results in animal models efficacy-wise. This discrepancy may be due to the large dose gap between mice and humans and the apparent variability of the EPR effect in human cancer. PLD is a complex product and we are still in a learning curve regarding a number of factors such as its interaction with the complement system and its immune modulatory properties, as well as its integration in multimodality therapy that may potentiate its value and role in cancer therapy.

The development of stable and long-circulating liposomes provides protection of the drug cargo from degradation and increases tumor drug delivery, leading to the design of liposome formulations with great potential in cancer therapy. However, despite the sound pharmacologic basis, many liposomal as well as other nanoparticle-based drug formulations have failed to meet regulatory criteria for approval. The question that arises is whether we have missed key liposome-host interactions that can account for the gap between the major pharmacologic advantages in preclinical studies and the modest impact of the clinical effects in humans. We will discuss here the nanoparticle-immune system interactions that may undermine the antitumor effect of the nanodrug formulations and contribute to this gap. To overcome this challenge and increase clinical translation, new preclinical models need to be adopted along with comprehensive immunopharmacologic studies and strategies for patient selection in the clinical phase.