Camptothecins (CPTs) are a quinoline alkaloid isolated from camptothecaacuminata decne. As a natural inhibitor of topoisomerase I, Camptothecins have good therapeutic effects on malignant tumors (eg, liver cancer, breast cancer, lung cancer and ovarian cancer), viruses and skin diseases due to the cytotoxic activities. To increase the water solubility, targeting effect and antitumor activities of Camptothecins, researchers usually modified Camptothecin’s structure by introducing polar groups, hydrophilic polymer carriers or targeted molecules at the active sites. In addition, drug molecules can be delivered to specific cells by introducing a drug loading system with targeting function and using the specificity and targeting of the transmission system to realize active and passive targeting of tumor cells.
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The structure of Camptothecins (CPTs) includes four hexatomic rings (two quinoline rings, one pyridone ring and one α-hydroxylactone ring with S-configuration chiral carbon) and one five-membered ring (pyrrole ring). The S-configuration chiral carbon, α-hydroxylactone and hydropyridinone are essential activity structures of Camptothecins. Most of the structural modifications of Camptothecins are concentrated in two quinoline rings and α-hydroxylactone ring. The research shown that most derivatives have good inhibitory effects on tumor cell proliferation. For example, when -NO2 group was introduced into the specific carbon atom of Camptothecins, the 9-nitrocamptothecin derivative obtained was water-insoluble, which had excellent therapeutic effect on advanced pancreatic cancer.
In the S phase of tumor cell DNA replication, Camptothecins (CPTs) inhibits DNA synthesis and induces apoptosis by inhibiting the activities of topoisomerase I. When Camptothecins bonding with topoisomerase I-DNA to form a ternary complex, it can improve the stability of topo I -DNA complex. So, DNA strand breaks cannot be reconnected to prevent DNA replication and RNA synthesis. It has no effect on G0 phase cells and slight lethality on G1, G2 and M phase cells. Furthermore, Camptothecins can destroy DNA structure directly and has no cross resistance with common antitumor drugs.
Research have shown that Camptothecins and its derivatives have inhibitory effect on HepG2 cells and can induce apoptosis. It has therapeutic effect on lung cancer, esophageal cancer, lymphosarcoma, bladder cancer, cylindric adenocarcinoma, leukemia, malignant hydatidiform mole and choriocarcinoma. In the treatment of gastric cancer, colon cancer and rectal cancer, the symptoms of patients were improved after 15-30 days, such as increased appetite, weight gain, tumor or focal lesions of barium meal examination reduction. Furthermore, DNA topoisomerase I is very active in HIV replication, and low dose Camptothecins can block the replication of HIV-1 in infected cells (acute and chronic). Recent studies have shown that Camptothecins inhibits HIV replication of patients with acute HIV infection, reaching 89%-93%. It is a natural drug for the treatment of AIDS.