A highly sensitive and stable TiO 2 /graphene/chitosan (TiO 2 /GRP/CHIT) modified glassy carbon electrode was developed. The sensor exhibits excellent electrocatalytic activity with fast response and convenient determination of an anti-HIV drug Topotecan (TPT). Moreover, from the response characteristics of cyclic voltammetry(CV) and square wave voltammetry (SWV), it was observed that TPT could be effectively accumulated at TiO 2 /GRP/CHIT/GCE and resulted in a sensitive anodic peak current in Britton-Robinson buffer (pH 5.6). Under the optimized experimental conditions, electro-oxidation of TPT demonstrates linearity within a dynamic concentration of 100 to 1200 ng/mL, with a detection limit of 122.07 ng/mL (LOD) and a quantification limit of 369.9 ng/mL (LOQ). On the basis of the electrochemical measurements, electrode dynamics parameters have been evaluated and the sensor has been successfully employed for determination of TPT in pharmaceutical formulation. -ethyl-4,9-dihydroxy-1H-pyrano[3 ,4 :6,7]indolizino[1,2-b]quinoline-3,14(4H,12H)-dione (Scheme 1), is a derivative of the plant alkaloid camptothecin. It has been found to decrease replication and is a potent and selective inhibitor of both acute and chronic human immunodeficiency virus type-1 infections. 1,2 TPT works on topoisomerase, which is found in both proliferating and non-proliferating cells. Furthermore, TPT also possesses a wide range of biological and therapeutic properties. [3][4][5][6] Because drug analysis has an extensive impact on public health, the development of a quick and sensitive method for the analysis of the active ingredients to avoid inappropriate dosing which can cause adverse side reactions is important. Several techniques have been explored for the determination of TPT, including liquid chromatography-mass spectrometry (LC-MS), 7,8 LC, 9 HPLC, and RP-HPLC. 10-14 However, these techniques are extremely time intensive as they are coupled with complicated preconcentration steps due to the complexity of the real samples and the low concentration of the analyte and above all they require expensive equipment which is not always available. Electrochemical methods are now being explored because of their immense advantages over the conventional techniques, such as high sensitivity, selectivity, and fast detection, and above all their being quite inexpensive. Additional application of electrochemistry includes the determination of the redox properties of drugs which provides an insight into their metabolic fate and the in-vivo redox process which makes it easier to understand the pharmacological activities. [15][16][17][18][19][20][21][22][23][24] The development of electrochemical sensors for the analysis of pharmaceutically important compounds with respect to their sensitivity, accuracy, and simplicity have been of greater interest in recent years.Modified electrodes have recently received tremendous interest largely because they have a wide range of potential applications in electrochemical technology, energy conversion, and, particul...