Solid tumors are often poorly vascularized, which impairs
oxygen
supply and drug delivery to the cells. This often leads to genetic
and translational adaptations that promote tumor progression, invasion,
metastasis, and resistance to conventional chemo-/radiotherapy and
immunotherapy. A hypoxia-directed nanosensitizer formulation of a
hypoxia-activated prodrug (HAP) was developed by encapsulating iodoazomycin
arabinofuranoside (IAZA), a 2-nitroimidazole nucleoside-based HAP,
in a functionally modified carbohydrate-based nanogel, facilitating
delivery and accrual selectively in the hypoxic head and neck and
prostate cancer cells. Although IAZA has been reported as a clinically
validated hypoxia diagnostic agent, recent studies have pointed to
its promising hypoxia-selective anti-tumor properties, which make
IAZA an excellent candidate for further exploration as a multimodal
theranostic of hypoxic tumors. The nanogels are composed of a galactose-based
shell with an inner core of thermoresponsive (di(ethylene glycol)
methyl ethyl methacrylate) (DEGMA). Optimization of the nanogels led
to high IAZA-loading capacity (≅80–88%) and a slow time-controlled
release over 50 h. Furthermore, nanoIAZA (encapsulated
IAZA) displayed superior in vitro hypoxia-selective
cytotoxicity and radiosensitization in comparison to free IAZA in
the head and neck (FaDu) and prostate (PC3) cancer cell lines. The
acute systemic toxicity profile of the nanogel (NG1)
was studied in immunocompromised mice, indicating no signs of toxicity.
Additionally, growth inhibition of subcutaneous FaDu xenograft tumors
was observed with nanoIAZA, demonstrating that this
nanoformulation offers a significant improvement in tumor regression
and overall survival compared to the control.