The present disclosure provides cytidine derivative dimers, salts and compositions of the cytidine derivative dimers, and methods of making and using the cytidine derivative dimers. The compounds that useful for treating a neoplasm in mammalian subjects. The cytidine derivative dimer has the following general formula (I): where R1 is C1-C10 alkyl, C1-C10 substituted alkyl, —(CH2)n-Ph, or substituted —(CH2)n-Ph; R2 is C1-C10 alkyl, C1-C10 substituted alkyl, —(CH2)n-Ph, or substituted —(CH2)n-Ph; R3 is hydrogen, alkoxycarbonyl or substituted alkoxycarbonyl; R4 is hydrogen, alkoxycarbonyl or substituted alkoxycarbonyl; and R5 is —(CH2)n—, substituted —(CH2)n—, or —(CH2)n—X1—X2—, X1 being O or S, and X2 being —(CH2)n-Ph, pyrimidyl, pyranyl, imidazolyl, pyrazinyl, or pyridyl. The disclosed cytidine derivative dimers/salts provide high anti-tumor activity with low toxicity and are useful for treating cancers.