Recently Shapiro TA et al [62] evaluated the activity of indenoisoquinolines (Figure 22) , originally known to have anti-cancer activity, against T. brucei and found that most of the compounds showed in vitro activity at submicromolar concentrations. The compound 12 ( Figure 23 ) with propylamino group at R 6 position and methoxy group at R 2 , R 3 and R 9 was the most active one with in vitro anti-trypanosomal activity of 0.05 µM. The compound also showed good in vivo activity as it delayed parasitemia and extended survival in infected mice. According to structure-activity analysis the compounds with enhanced potency included alkylamino substitutions on N-6, methoxy groups on C-2 and C-3, and a methylenedioxy bridge between C-8 and C-9. Testing of indenoisoquinolines with promising activity on L1210 mouse leukemia cells revealed all the compounds were more effective against trypanosomes than against mammalian cells. The indenoisoquinolines also showed appreciable water solubility indicating that these compounds have good quality for drug development. These compounds showed their anti-trypanosomal action by multiple mechanisms. The study indicated that they stabilize topoisomerase-DNA complexes in situ and may also impede topoisomerase binding to DNA. These agents markedly inhibited DNA synthesis by interfering with topoisomerase and possibly other DNA-metabolizing enzymes. concentrations in the range of 300 ng/ml up to 900 ng/ml. Some of the DuPont compounds, developed as anti-tumour drugs, were highly active but also showed high cytotoxicity on HT-29 cells. It was observed that the position R 1 and position R 2 in the quinolone core nucleus was not prerequisite for anti-trypanosomal activity and also substitution at R 8 position was not necessary for trypanocidal activity. Thus, based on the result obtained from SAR analysis special attention should be given to R 7 position and the tetracyclic derivatives. The in vivo results of these compounds were very poor, as none of the compounds evaluated produced cure of mice in dose escalation experiment up to 100mg/kg i.p. However no signs of toxicity were observed during the experiments. The in vivo ineffectiveness had not been explained and no drug level determination in the plasma of the treated mice was performed. 