Synthesis and antiproliferative activities of steroidal lactam conjugates bearing a new nitrogen mustard

Abstract

Alkylating agents are potent anticancer compounds that exert their anticancer properties through the inhibition of cell replication and transcription leading to cell death. Despite the numerous benefits, these agents also have serious drawbacks such as their high toxicity and low specificity towards cancer cells. As previously reported by our group, conjugation of alkylating agents with azasteroids can reduce their systemic toxicity and enhance their anticancer activity. In this work, novel steroidal alkylating agents bearing POPAM-OH were synthesized and their anticancer efficacy was evaluated in vitro and in vivo. All the novel hybrids demonstrated high antiproliferative effects against 5 different cancer cell lines in the low micromolar range. Treatment of SCID mice bearing SKOV-3 or PC-3 tumor xenografts with the most potent hybrid 19 led to significant reduction of tumor size (tumor inhibition TI = 95% in SKOV3 models and TI = 85.2% in PC3 models). Importantly, the acute toxicity of hybrid 19 (LD₁₀ = 36 μΜ, LD₅₀ = 62 μΜ) in CB17 SCID mice exhibited three-fold decrease compared to the acute toxicity of previously reported hybrids of POPAM-NH₂. This is an important finding since systemic cytotoxicity is a critical limitation of alkylating agents. Collectively, the steroidal conjugates of POPAM-OH displayed significant anticancer efficacy and reduced toxicity in vitro and in vivo rendering them as good candidates for cancer therapy.