Two new adamantyl-peptides, D-(2-adamantyl)-glycyl-L-alanyl-D-isoglutamine hydro-chloride (Isomer-1) and L-(2-adamantyl)-glycyl-L-alanyl-D-isoglutamine hydrochloride (Isomer-2), were tested in the model of the MCa mammary carcinoma of the CBA mouse. These compounds, and particularly Isomer-2 showed to be more effective in reducing lung metastases than primary tumor growth and to be active in conditions in which a low number of metastases are formed, a condition that is seen when the tumor is implanted s.c. or when its growth is slowed down by a lower inoculum size. The apparent lack of any correlation between the effect of Isomer-2 on tumor growth and metastasis formation and that on the response to ConA of in vitro IL-2 selected spleen lymphocytes seems to suggest that the dose and treatment schedule chosen might not be the most appropriate. In fact, the immunopotentiation observed a 2nd drug injection is virtually lost at the end of treatment and this fact might explain the limited effect on tumor growth, and could probably account for the lack of macroscopical effects on lung metastases and on survival time.

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