Effect of luteinizing hormone-releasing hormone analogs containing cytotoxic radicals on growth of estrogen-independent MXT mouse mammary carcinoma in vivo.

Cytotoxic luteinizing hormone-releasing hormone (LH-RH) analogs, AJ-004 (agonist [D-Lys6]LH-RH linked to methotrexate (MTX)), T-98 ([D-Lys6]LH-RH coupled to glutaryl-2-(hydroxymethyl)anthraquinone) (G-HMAQ) and T-121/B (antagonist containing two residues of G-HMAQ) were tested in female BDF1 mice bearing MXT ((3.2)/Ovex) estrogen-independent mammary tumors. All three cytotoxic LH-RH analogs, administered from Alzet Osmotic Minipumps for 3 weeks, produced a significant inhibition of tumor growth. The effects of T-98 and T-121/B were superior to those obtained by treatment with equimolar doses of cytotoxic moiety anthraquinone or the LH-RH carrier alone. We assume that cytotoxic LH-RH analogs have a combined hormonal and cytotoxic activity with a reduced toxicity after administration in vivo. This is the first demonstration of in vivo tumor inhibition by targeted LH-RH analogs bearing cytotoxic radicals.