Lessons Learned from Gemcitabine: Impact of Therapeutic Carrier Systems and Gemcitabine's Drug Conjugates on Cancer Therapy.

Currently, drug delivery systems have a high impact in cancer therapy and are receiving more attention than conventional cancer treatment modalities. Compared with current cancer therapies, gemcitabine (2', 2'-difluoro-2'-deoxycytidine) has been proven to be an effective chemotherapeutic agent against pancreatic, colon, bladder, breast, ovarian, non-small-cell lung, and head and neck cancers in combination with other anticancer agents. To improve the safety and efficacy of cytotoxic drugs, several drug delivery systems have been explored. This review outlines the recent work directed toward gemcitabine delivery systems for cancer therapy, including aerosols, polymeric nanoparticles, liposomes, microparticles, carbon nanotubes, and multifunctional theranostic nanomedicines. It also provides insight into the design and development of gemcitabine conjugation for safe and effective cancer therapy. Despite the clinical promises of gemcitabine, many therapeutic challenges remain. Specifically, its therapeutic use in cancer chemotherapy is impeded by a short biological half-life, caused by its rapid metabolism, and resistance due to increased expression of ribonucleotide reductase. In our opinion, many research investigations have contributed to improve the selectivity and efficacy of gemcitabine. This combined approach of drug delivery systems and gemcitabine conjugates has shown promising efficacy in preclinical models and significant potential for future clinical cancer-therapeutic applications. Also, these strategies overcome most of the aforementioned limits of gemcitabine.