Abstract: The present invention relates to a novel antineoplastic agent, designated IMIC (Inhibitor of Mevalonate Incorporation Into Cholesterol) having the following characteristics:(a) is present in the retentate of dialyzed skim milk;(b) is non-dialyzable;(c) has general properties of pyrimidines;(d) is bound to a protein in the proteose-peptone fration of milk;(e) is soluble in water;(f) is insoluble in organic solvents;(g) is stable in acid;(h) is not bound or retained by a C.sub.18 or C.sub.8 reverse phase HPLC columns;(i) is not retained by a C.sub.18 or silica gel sep. pak;(j) has .lambda. maximum absorbance at 208 nm and 278 nm (UV) in neutral ad acidic solution and in a basic solution at 223 and 290 nm;(k) provides peaks with a retention time of 7.52 minutes upon fractionation by HFLC on a Biorad Aminex resin column (30 cm .times.7.9 nm) with 0.05 NH.sub.2 SO.sub.4 as the mobile phase and with a flow rate of 0.7 ml/minute;(l) provides peaks with a retention time of 9.

Abstract: To permit regeneration of an insoluble support for immobilized proteins, the protein is connected to the support by a spacer arm containing a diazo linkage and when the protein is denatured, the spacer arm is broken by reducing the diazo linkage to remove the denatured protein. New native protein of the same or of a different type is joined to the arm to permit reuse of the support. A preferred support containing a spacer arm is p-(N-acetyl-L-tyrosine azo)benzamidoethyl agarose. A protein is coupled to the carboxyl group of N-acetyl-L-tyrosine and when the protein is spent, the azo bond is reduced to remove the protein and leave p-aminobenzamido agarose which is diazotized and recoupled to N-acetyl-L-tyrosine which is then coupled to fresh protein.