Assistant Professor Drexel University Cherry Hill, New Jersey, United States
Introduction: The immune system plays a central role in tissue homeostasis, disease progression, and healing processes. Macrophages (MF) are mediators of the immune microenvironment that span diverse behaviors, ranging broadly from inflammatory (M1-like) to pro-healing (M2-like) phenotypes. Small molecule drugs are readily available to treat inflammatory-mediated diseases by modulating MF behavior. Their therapeutic efficacy, however, remains limited by a poor understanding of which drugs can promote desirable MF cell-state transitions and inadequate drug pharmacokinetics (poor solubility, non-specific cell uptake, rapid blood clearance, and off-target effects). Biomaterial-based drug delivery systems enable cell-targeting strategies to overcome these challenges. Furthermore, the recognition of drugs by macrocyclic hosts provides a readily adaptable method to encapsulate a variety of therapeutics for delivery (Fig 1A), including within soluble nanoparticles for systemic cell-targeted therapies. Our objective has been to leverage these systems for cancer immunotherapy and to prevent ischemic heart failure, which results directly from a hyperinflammatory response to myocardial infarction.
Materials and
Methods: For drug delivery to MF, succinyl-β-cyclodextrin was crosslinked by lysine to develop cyclodextrin nanoparticles (CDNPs: 30nm, -10mV, >10%w/w drug loading) that encapsulate hydrophobic small molecule drugs with exceptional loading capacity through physical guest-host interactions. Through a combination of image-based high-content screening (Fig 1B) and qPCR analysis in primary murine and human cells, we identified a lead drug candidate (R848) that provoked robust M2M1 transition (IC50 7.2nM). Efficacy of the drug-loaded nanocarriers (CDNP-R848) against established solid tumors was assessed in multiple tumor models both as a monotherapy or as an adjuvant to frontline checkpoint therapies (i.e., anti-PD1). Separately, we have developed murine models of ischemia reperfusion (IR) injury to the myocardium, mimicking heart attack and subsequent clinical intervention. A novel two-step screening process was used to examine a library of small molecule drugs spanning a variety of drug classes to i) identify inhibitors of inflammatory macrophages in RAW-BlueTM reporter cell lines and ii) identify drugs that promote a reparatory phenotype. Through these and follow-up nanoString analysis in primary murine and human cells, we identified celastrol as a potent anti-inflammatory (IC50 < 100nM) that also promotes M1M2 transition. Prevention of ischemic heart failure was examined, with treatment applied two days post-IR; outcomes were assessed by flow cytometry, echocardiography, and histology. In both tumor and IR models, biodistribution of fluorescently-labeled CDNPs was examined, including by intravital confocal and longitudinal near-IR imaging.
Results, Conclusions, and Discussions: MF are abundant in solid cancers, assuming an immunosuppressive M2-like phenotype that supports tumor growth and immune escape. Recent methods have focused on identifying drugs that re-polarize MF to a tumor-destructive M1-like phenotype. However, targeting these drugs to MF to improve treatment efficacy and reduce systemic side effects has remained a challenge. The drug-laden nanoparticles (CDNP-R848) readily accumulated in tumors (4.1±1.15%ID) by MF-specific update, induced in situ cell reprogramming (>5-fold increase in IL12), and reduced tumor burden in multiple models (MC38, B16F10, Gl261). Treatment synergized with frontline anti-PD1 checkpoint therapy to eradicate tumors (Fig 1C,D).
Separately, we have explored the ability to inhibit inflammation-induced ischemic heart failure. Following IR injury in mice, we observed a marked increase in M1-like MF that peaked at day 1-2 post-IR (Fig 2A,B). CDNP delivery during this timeframe targeted delivery to the heart, persisting locally for >2 wks (Fig 2C). Accumulation was driven my MF-specific uptake (confocal microscopy) and enhanced post-IR (>2-fold) due to an increase in local MF populations. CDNP-celastrol treatment reduced M1 (Nos2+) and increased M2 (Arg1+) MF (Fig 2D,E), and reduced MF abundance – attributable to a >50% decrease in inflammatory monocyte recruitment. Treatment reduced fibrosis, prevented deleterious ventricular remodeling, and maintained ejection fraction (Fig 2F,G).
In sum, small-molecule therapeutics are potent modulators of immune system function, who’s capacity to functionally re-orient cell- and tissue-level behaviors for therapeutic benefit is enhanced by cell-targeted carriers.
