Prodrugs of doxorubicin and melphalan and their activation by a monoclonal antibody-penicillin-G amidase conjugate.
The syntheses and cytotoxic activities of substituted N-phenylacetamido derivatives of doxorubicin and melphalan are described. The derivatives were designed as prodrugs which could be activated in a site-specific manner by monoclonal antibody-penicillin-G amidase (mAb-PGA) conjugates. N-(Phenylacetamido)doxorubicin (2) and N-(phenylacetyl)melphalan (6) were found to be 10- and 20-fold less cytotoxic against H2981 lung adenocarcinoma cells than doxorubicin and melphalan, respectively. When incubated with PGA, the cytotoxicity of 2 and 6 increased and became equivalent to that of the corresponding drugs from which they were made. The poor solubility characteristics of 2 in aqueous solutions provided the basis for the development of the more soluble doxorubicin derivatives, N-(4-aminophenylacetyl)doxorubicin (3) and N-(4-phosphonooxy)phenylacetyl)-doxorubicin (4). In vitro cytotoxicity assays indicated that 3 and 4 were at least 1000-fold less toxic than doxorubicin against H2981 cells. PGA and the mAb conjugate L6-PGA were able to effect the activation of 3 and 6 on H2981 cells (L6-antigen positive). Hydrolysis of the phosphate group of 4 was required prior to activation with PGA or L6-PGA. This was achieved using alkaline phosphatase, or by exposing 4 to phosphatases present in cell culture medium. The activation of 3, 4, and 6 on H2981 cells by L6-PGA occurred in an immunologically specific manner, since activation could be blocked by saturating cell surface antigens with L6 prior to treatment with L6-PGA. These results demonstrate that 3, 4, and 6 are prodrugs that can be specifically activated to release clinically approved anticancer agents by a mAb-PGA conjugate.
Vrudhula
V M
VM
Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, Washington 98121.
Senter
P D
PD
Fischer
K J
KJ
Wallace
P M
PM
D000230:Adenocarcinoma / Q000188:drug therapy; D000903:Antibiotics, Antineoplastic / Q000138:chemical synthesis* / Q000494:pharmacology; D004317:Doxorubicin / Q000031:analogs & derivatives*; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy; D008558:Melphalan / Q000031:analogs & derivatives*; D010399:Penicillin Amidase / Q000378:metabolism; D010648:Phenylacetates / Q000138:chemical synthesis* / Q000494:pharmacology; D011355:Prodrugs / Q000138:chemical synthesis* / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000903:Antibiotics, Antineoplastic; D010648:Phenylacetates; D011355:Prodrugs; D004317:Doxorubicin; D010399:Penicillin Amidase; D008558:Melphalan