You can make use of one-way ANOVA to determine the level of significance between the different experimental groups (drug-treated with different concentrations) and relevant controls (untreated cells). Good luck!
My doubt is that we have to compare two drugs i.e temozolomide and drug x which were performed with various concentrations (1,3,10,30,100,300,1000mM) so there is dependent variable - % of cell viability and two independent variable that is drugs and concentrations. So now if we perform one way ANOVA then we can choose only one independent variable. So do we have to perform two one way ANOVA tests for two different independent variable?