Prenyl transferase inhibitors

A compound of the formula I or formula II ##STR4## wherein R.sub.1 is N(R.sub.10)(R.sub.11);

• R.sub.2 is thio lower alkyl;
• each of R.sub.3 and R.sub.5, independently, is CH.sub.2 or C(O);
• R.sub.4 is thio lower alkyl, wherein the free thio groups of R.sub.2 and R.sub.4 form a disulfide bond;
• R.sub.6 is a residue of a natural or synthetic .alpha.-amino acid
• R.sub.7 is a residue of a natural or synthetic .alpha.-amino acid;
• R.sub.8 is OH or lower alkoxy, or, together with R.sub.7, forms homoserinelactone;
• each of R.sub.9, R.sub.10, R.sub.11, independently, is H or lower alkyl;
• R.sub.12 is a substituted or unsubstituted moiety selected from cycloalkyl, cycloalkyl lower alkyl, aryl, aryl lower alkyl, heterocycle, and heterocycle lower alkyl, wherein the substituent is lower alkyl, aryl, halo, lower alkoxy, or C(O)--R.sub.7 --R.sub.8 ;
• R.sub.13 is lower alkyl, aryl, or aryl lower alkyl;
• R.sub.18 is H or, together with R.sub.9, forms --CH.sub.2 CH.sub.2 --;
• or a pharmaceutically acceptable salt thereof.