Self-immolative prodrugs: candidates for antibody-directed enzyme prodrug therapy in conjunction with a nitroreductase enzyme.

The synthesis and properties of some prodrug candidates for antibody-directed enzyme prodrug therapy (ADEPT) are described. These compounds have been designed to generate the corresponding active drug upon interaction with a bacterial nitroreductase that can be conjugated to antibodies that recognize tumor-selective antigens. The active drugs included in the study are actinomycin D, mitomycin C, doxorubicin, 4-[bis(2-chloroethyl)amino]aniline and 4-[bis(2-chloroethyl)amino]phenol. The prodrugs were all 4-nitrobenzyloxycarbonyl derivatives of these drugs, which upon enzymatic reduction, generated the drug through self-immolation of the 4-(hydroxyamino)benzyloxycarbonyl group. In the case of actinomycin D, the ratio of the dose required between drug and prodrug to give the same cytotoxicity was greater than 100. The prodrug was also much less toxic (20-100x) than actinomycin D to mice in vivo. Therefore this self-immolative prodrug has a potential application in the treatment of cancer using an ADEPT-type approach.

Evidence against the formation of 2-amino-6-(2-formyl-5-hydroxymethyl-pyrrol-1-yl)-hexanoic acid ('pyrraline') as an early-stage product or advanced glycation end product in non-enzymic protein glycation.

1. It has been suggested that 2-amino-6-(2-formyl-5-hydroxymethyl-pyrrol-1-yl)-hexanoic acid ('pyrraline') is formed as an advanced glycation end product in the Maillard reaction under physiological conditions. Antibodies were raised to caproyl-pyrraline linked to keyhole-limpet haemocyanin and were used to develop an e.l.i.s.a. and Western blotting system for the specific detection of pyrraline in samples in vivo and in vitro. 2. Human serum albumin was isolated from the serum samples of diabetic and non-diabetic subjects. Pyrraline was not detected (< 1.2 pmol) in any of the samples, indicating that it was not a major advanced glycation end product in vivo. 3. BSA was incubated separately with D-glucose and a model fructosamine, N epsilon-(1-deoxy-D-fructos-1-yl)-hippuryl-lysine, under physiological conditions for 30 days. Aliquots removed from the incubations at 5 day intervals contained no detectable pyrraline, indicating that pyrraline was not an early-stage product of the Maillard reaction in vitro. 4. The model fructosamine, N epsilon-(1-deoxy-D-fructos-1-yl)-hippuryl-lysine, was incubated at pH 7.4 and 37 degrees C for 25 days during which it degraded to hippuryl-lysine and N epsilon-carboxymethyl-hippuryl-lysine. Aliquots were removed at 5 day intervals and assayed for pyrraline. None was detected (< 23 pmol/ml) in the course of the degradation of the fructosamine (400 nmol/ml degraded), indicating that pyrraline was not a major product of the degradation of fructosamine under physiological conditions in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)