Albumin has shown remarkable promise as a natural drug carrier by improving pharmacokinetic (PK) profiles of anticancer drugs for tumor-targeted delivery. The exogenous or endogenous albumin enhances the circulatory half-lives of anticancer drugs and passively target the tumors by the enhanced permeability and retention (EPR) effect. Thus, the albumin-based drug delivery leads to a potent antitumor efficacy in various preclinical models, and several candidates have been evaluated clinically. The most successful example is Abraxane, an exogenous human serum albumin (HSA)-bound paclitaxel formulation approved by the FDA and used to treat locally advanced or metastatic tumors. However, additional clinical translation of exogenous albumin formulations has not been approved to date because of their unexpectedly low delivery efficiency, which can increase the risk of systemic toxicity. To overcome these limitations, several prodrugs binding endogenous albumin covalently have been investigated owing to distinct advantages for a safe and more effective drug delivery. In this review, we give account of the different albumin-based drug delivery systems, from laboratory investigations to clinical applications, and their potential challenges, and the outlook for clinical translation is discussed. In addition, recent advances and progress of albumin-binding drugs to move more closely to the clinical settings are outlined.

While proteolysis‐targeting chimeras (PROTACs) hold great potential for persistently reprogramming the immunosuppressive tumor microenvironment via targeted protein degradation, precisely activating them in tumor tissues and preventing uncontrolled proteolysis at off‐target sites remain challenging. Herein, a light‐triggered PROTAC nanoassembly (LPN) for photodynamic indoleamine 2,3‐dioxygenase (IDO) proteolysis is reported. The LPN is derived from the self‐assembly of prodrug conjugates, which comprise a PROTAC, cathepsin B‐specific cleavable peptide linker, and photosensitizer, without any additional carrier materials. In colon tumor models, intravenously injected LPNs initially silence the activity of PROTACs and accumulate significantly in targeted tumor tissues due to an enhanced permeability and retention effect. Subsequently, the cancer biomarker cathepsin B begins to trigger the release of active PROTACs from the LPNs through enzymatic cleavage of the linkers. Upon light irradiation, tumor cells undergo immunogenic cell death induced by photodynamic therapy to promote the activation of effector T cells, while the continuous IDO degradation of PROTAC simultaneously blocks tryptophan metabolite‐regulated regulatory‐T‐cell‐mediated immunosuppression. Such LPN‐mediated combinatorial photodynamic IDO proteolysis effectively inhibits tumor growth, metastasis, and recurrence. Collectively, this study presents a promising nanomedicine, designed to synergize PROTACs with other immunotherapeutic modalities, for more effective and safer cancer immunotherapy.

Proteolysis-targeting chimeras (PROTACs) are rapidly emerging as a potential therapeutic strategy for cancer therapy by inducing the degradation of tumor-overexpressing oncogenic proteins. They can specifically catalyze the degradation of target oncogenic proteins by recruiting E3 ligases and utilizing the ubiquitin-proteasome pathway. Since their mode of action is universal, irreversible, recyclable, long-lasting, and applicable to ‘undruggable’ proteins, PROTACs are gradually replacing the role of conventional small molecular inhibitors. Moreover, their application areas are being expanded to cancer immunotherapy as various types of oncogenic proteins that are involved in immunosuppressive tumor microenvironments. However, poor water solubility and low cell permeability considerably restrict the pharmacokinetic (PK) property, which necessitates the use of appropriate delivery systems for cancer immunotherapy. In this review, the general characteristics, developmental status, and PK of PROTACs are first briefly covered. Next, recent studies on the application of various types of passive or active targeting delivery systems for PROTACs are introduced, and their effects on the PK and tumor-targeting ability of PROTACs are described. Finally, recent drug delivery systems of PROTACs for cancer immunotherapy are summarized. The adoption of an adequate delivery system for PROTAC is expected to accelerate the clinical translation of PROTACs, as well as improve its efficacy for cancer therapy.

Photodynamic therapy (PDT) induces tumor cell pyroptosis, a form of programmed cell death that triggers antitumor immunity. However, high glucose metabolism and hypoxic conditions in the tumor microenvironment (TME) limit PDT efficiency and impair effector cell function. Here, we propose a cancer metabolic reprogramming-enabling photoresponsive nanoproteolysis-targeting chimera (Nano-PROTAC; NanoTAC), derived from the supramolecular self-assembly of drug conjugates that bridge a PROTAC targeting hexokinase II (HK2) and a photosensitizer via a biomarker-cleavable linker. In a triple-negative breast cancer (TNBC) model, NanoTAC initially silences PROTAC activity and accumulates in tumor regions, where it undergoes linker cleavage in response to enzymatic biomarkers. Upon photoirradiation, PDT-induced pyroptotic cell death promotes the release of tumor-associated antigens (TAAs) and damage-associated molecular patterns (DAMPs) to drive the cancer-immunity cycle. Concurrently, targeted protein degradation (TPD) via PROTACs counteracts glucose and oxygen consumption in the TME, ultimately potentiating pyroptosis-mediated photoimmunotherapy. This combination therapy achieves a high rate of complete regression in primary TNBC and confers adaptive immunity to prevent metastasis and recurrence. Our study presents a rationally designed nanomedicine that integrates PDT and PROTACs, shedding light on strategies for more effective cancer immunotherapy.

The mRNA-lipid nanoparticles (mRNA@LNPs) offer a novel opportunity to treat targets previously considered undruggable. Although antibody conjugation is crucial for enhancing the specificity, delivery efficiency, and minimizing the toxicity of mRNA therapeutics, current chemical conjugation methods are complex and produce heterogeneous particles with misoriented antibodies. In this work, we introduce a chemical-free approach to functionalize mRNA@LNPs with antibodies, mimicking protein corona formation for targeted mRNA delivery. By fusing apolipoprotein to the Fc domain of a targeting antibody, we enabled the antibody to spontaneously display on the surface of mRNA@LNPs without altering the existing LNP process or employing complex chemical conjugation techniques. We demonstrated precise protein expression using trastuzumab-bound mRNA@LNPs, facilitating specific mRNA expression in HER2-positive cancer cells. mRNA was efficiently delivered to the tumor site after intravenous administration. While the control LNPs lacking targeting antibodies caused acute liver toxicity, trastuzumab-displayed LNPs showed no systemic toxicity. The tumor-specific delivery of p53 tumor suppressor mRNA led to the complete regression of cancer cells. Thus, apolipoprotein fusion enables a straightforward and scalable production of antibody-functionalized mRNA@LNPs, offering significant therapeutic potential in gene therapy.

Background: Photodynamic therapy (PDT) is a promising strategy to promote antitumor immunity by inducing immunogenic cell death (ICD) in tumor cells. However, practical PDT uses an intense visible light owing to the shallow penetration depth of the light, resulting in immunosuppression at the tumor tissues. Methods: Herein, we propose an implantable micro-scale light-emitting diode device (micro-LED) guided PDT that enables the on-demand light activation of photosensitizers deep in the body to potentiate antitumor immunity with mild visible light. Results: The micro-LED is prepared by stacking one to four micro-scale LEDs (100 μm) on a needle-shape photonic device, which can be directly implanted into the core part of the tumor tissue. The photonic device with four LEDs efficiently elicits sufficient light output powers without thermal degradation and promotes reactive oxygen species (ROS) from a photosensitizer (verteporfin; VPF). After the intravenous injection of VPF in colon tumor-bearing mice, the tumor tissues are irradiated with optimal light intensity using an implanted micro-LED. While tumor tissues under intense visible light causes immunosuppression by severe inflammatory responses and regulatory T cell activation, mild visible light elicits potent ICD in tumor cells, which promotes dendritic cell (DC) maturation and T cell activation. The enhanced therapeutic efficacy and antitumor immunity by micro-LED guided PDT with mild visible light are assessed in colon tumor models. Finally, micro-LED guided PDT in combination with immune checkpoint blockade leads to 100% complete tumor regression and also establishes systemic immunological memory to prevent the recurrence of tumors. Conclusion: Collectively, this study demonstrates that micro-LED guided PDT with mild visible light is a promising strategy for cancer immunotherapy.