Letrozole-Loaded Nano-formulations as a Drug Delivery System for Cancer Therapy: Recent Developments

Letrozole (LTZ) is a powerful oral aromatase inhibitor in vitro, in vivo (in animals), and in people that are nonsteroidal and reversible. Other aromatase inhibitors (AIs), like anastrozole, exemestane, formestane, and aminoglutethimide, are less effective than letrozole of potency. LTZ also effectively suppresses intratumoral aromatase in vivo. It seems that aromatase is the target of letrozole's effect. Several animal models have revealed that LTZ has powerful antitumor properties. Low nanomolar quantities of letrozole successfully suppressed aromatase activity in mammary adipose tissue as well as breast cancer LTZ, which has been approved and is used as a treatment for postmenopausal women with hormone receptor-positive (HR+) primary breast cancer since it efficiently inhibits estrogen production. By encapsulating LTZ with polymer nanoparticles, liposomes, nanoemulsions, carbon-based nanoparticles (CBNs), solid lipid nanocarriers (SLNs), and nanostructured lipid carriers (NLCs), some issues have been resolved by increasing solubility and biostability. The targeted delivery and release of LTZ using some of the nanocarriers and several examples of co-delivery of different drugs like curcumin, quercetin, celecoxib, and cyclophosphamide with LTZ employing the nanoparticles mentioned above and their exhibited cytotoxicity against several cell lines like MCF-7, SK-BR-3, MDA-MB-231, and MDA-321 have also been examined in this review.