Summary Safety of administration of a vindesine (VDS)-anti-CEA conjugate and its ability to localise after radiolabelling were investigated in patients with advanced metastatic carcinoma (4 colorectal and 4 ovarian).

The anticancer alkaloid vindesine (VDS) was conjugated to four mouse monoclonal antibodies recognizing human tumor-associated antigens. The antibodies were 96.5 (antimelanoma, IgG2a); 791T/36 (antiosteogenic sarcoma, IgG2b); 11.285.14, and 14.95.55 (anticarcinoembryonic antigen, IgG1 and IgG2a respectively). Conjugates VDS-96.5 and VDS-791T/36 were tested in vitro and shown to be specifically cytotoxic for target cells expressing the appropriate antigen. The in vivo effects of the antibodies and conjugates were tested against human tumor xenografts in athymic or immunodeprived mice using multiple treatments. Conjugate VDS-96.5 retarded the initial growth of a melanoma xenograft, whereas free antibody was without effect. Similarly, VDS-791T/36 but not free antibody retarded the growth of osteogenic sarcoma 791T. The most marked antitumor effects observed were those obtained with VDS conjugates of the anti-CEA antibodies against a colorectal tumor xenograft. Antibody 14.95.55 suppressed tumor growth both alone and as a VDS conjugate, whereas 11.285.14 produced only a slight effect alone but an almost complete and lasting suppression of tumor growth as a VDS conjugate. Free VDS had little effect at nontoxic levels. Acute studies showed that VDS-11.285.14 conjugate was considerably less toxic than free VDS in Balb/c mice.

The distribution of tritiated vindesine (3H-VDS) was studied in the tissues and tumours of athymic mice bearing a human colorectal tumour xenograft. Selective tumour localisation was obtained when 3H-VDS was injected as a conjugate with a monoclonal anti-CEA antibody (11.285.14) but not as a conjugate with a non-binding monoclonal IgGl (Ag8) or as free succinoyl-VDS. The amounts of VDS that localised in the tumour following injections of 3H-VDS-11.285.14 increased in proportion to the amount injected, over a wide dose range. Conjugates prepared using the Fab fragments of 11.285.14 showed no evidence of selective tumour uptake in comparison with normal tissues. Various dose levels of VDS-11.285.14 conjugate and free VDS were studied for effects on the growth of the tumour xenograft. A growth inhibition of 50% was obtained at 1.5 mg/kg with free VDS and at 2.5 mg/kg with conjugated VDS. The conjugate was, however, considerably less toxic.

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(R)-(-)-benoxaprofen is stereospecifically inverted to the (S)-(+)-enantiomer by rats and humans. The rate of inversion is much faster in rats (t 1/2 ca. 2.5 h) than in humans (t 1/2 108 h). Inversion in rats apparently does not occur in the liver, but can be brought about in vitro by an everted intestinal sac preparation, suggesting that the transformation takes place while passing through the gut wall.