DIVEMA

SOD is a major oxygen free radical scavenging enzyme, which may therefore have beneficial effects in liver fibrosis. Through mannosylation or coupling to the polyanion DIVEMA, SOD was made more liver specific. Both conjugates showed superior inhibition of intrahep-atic ROS production in fibrotic rats as compared to unmodified SOD. DIVEMA-SOD, however, exhibited the most potent inhibitory effects [112]. Although their mode of action is most probably extracellular free radical scavenging, Man-SOD and DIVEMA-SOD are likely to... 

DIVEMA (Hydrolyzed form of divinyl ether and maleic anhydride copolymer) Cyclophos- phamide Ester bond between drug derivative hydroxyl and polymer carboxyl None N/A N/T Anticancer activity of conjugate was comparable to free drug against L1210 leukemia bearing mice 58... 

MVE-2 (Divinyl ether-maleic anhydride DIVEMA copolymer) (Mw < 18000) Activity demonstrated against numerous tumor models through stimulation of host immune system. LI210 bearing mice treated with MVE-2 and 5-aza-2-deoxycytidine led to a number of cures 65... 

The DIVEMA copolymer has also been covalently linked to methotrexate (356). This polymer spontaneously released methotrexate from the polymer backbone by... 

Polymer (VI) has been shown to have antitumor activity against adenocarcinoma 755, Dunning ascites leukemia. Friend leukemia virus, and Lewis lung carcinoma. In the latter case, polymer (VI) showed activity about equal to that of cyclophosphamide (an alkylating agent) and was more effective than 6-mercaptopurine (an antimetabolite) ( ). The DIVEMA polymer (V) Is also active against some cancer causing viruses such as Friend leukemia, Moloney sarcoma and Rauscher leukemia ( ). 

There has been much speculation concerning the mechanism of tionor Inhibition by these polyanlonlc systems. Many polyanions Induce Interferon production (22) and this fact has also been suggested as the source of the activity. More recently, it has been observed that DIVEMA is not cytotoxic to tumor cells (23) and that only those polymers that activated macrophages showed antlneoplastlc activity (24). Inhibition via macrophages Is believed to be the mode of action for DIVEMA (V) if not for all polyanlonlc polymers (16). 

Maleic anhydride and vinyl ether undergo a radical-catalyzed cyclic alternating copolymerization in a 2 1 ratio. This copolymer, frequently designated in the literature as DIVEMA or as pyran copolymer, has shown unusual and exciting biological activity, and has therefore undergone intensive investigation. 

DIVEMA and some DIVEMA derivatives were synthesized and tested for toxicity and immunological behaviour. 

Toxicity can be varied by introducing different side groups into parent DIVEMA molecules by polymer analogous reactions. 

The compounds tested showed mitogenic effects,i.e. they stimulated lymphocyte proliferation. Astonishingly, a DIVEMA-DNP conjugate did not induce the production of DNP-specific antibodies. Our results suggest that this is due to the formation of DNP-specific active suppressor cells. Using serum free culture media, we could show for the first time that DIVEMA and derivatives stimulate macrophages to release cytotoxic factors into the supernatant. However, no significant release of lytic enzymes was detected. 

DIVEMA and the derivatives tested failed to stimulate endocytosis by macrophages of iZ5I-PVP and 198/ u (colloidal) higher mol. wt. DIVEMA inhibited pinocytosis. We conclude that the only effect of the compounds tested on macrophages is the release of cytotoxic factors into the supernatant. 

There are, however, many unsolved problems concerning toxicity, endocytic uptake and immunogenicity of DIVEMA. In order to learn more about the structure dependency of these properties, we sythesized some DIVEMA derivatives and investigated DIVEMA and the new derivatives with appropriate routine biological test systems. 

DIVEMA samples (1a - 1d) were kindly supplied by Dr.D. Breslow, HERCULES Inc. The synthesis of the derivatives (11) will be published elsewhere. The compounds investigated are listed in Table I-... 

One disadvantage of DIVEMA is its relatively high toxicity which is mainly caused by high molecular weight fractions ( 7). In an attempt to lower the toxicity of DIVEMA, derivatives (3) and (4) were synthesized. 

Table II. Acute toxicity of DIVEMA and some derivatives...

Effects of DIVEMA and DIVEMA Derivatives on the Immune System. 

DIVEMA is known to act upon different types of immune cells (J 3) such as the antibody producing B cells (bone marrow derived lymphocytes) on T-cells (thymus processed lymphocytes) and on macrophages (cells which phagocytose foreign material). The mechanisms of interaction between polymers and the immune system are very complex. In order to investigate them, many different experimental approaches can be used. 

Are the DIVEMA derivatives mitogenic, i.e. do they stimulate lymphocyte proliferation ... 

Mitogenic Activity of DIVEMA Derivatives. A first approach to the effects of a compound on the immune system is to test its ability to stimulate lymphocyte proliteration. An appropriate test is to measure the incorporation of 3H-thymidine into DNA of dividing cells ... 

These measurements show that small doses of DNP-DIVEMA (2)tgiven to the mice before the immune system is challenged with the potent antigen DNP-KLH, significantly suppress the formation of DNP-specific antibodies (2) induces tolerance against DNP-KLH. 

Taking into account that (2) is mitogenic but still has no antigenic effect, we suggest that induction of tolerance by this polymer is due to formation of DNP-specific suppressor cells. This would explain why DIVEMA is immune stimulating (induces proliferation of lymphocytes) without causing production of antibodies (2) induces active suppression and thus leads to the apparent lack of immunogenicity. 

Schultz eT"al. (21, 22) found that macrophages of DIVEMA-treated mice iFFibited tumour cell proliferation in vitro this means that DIVEMA activates macrophages. The authors did not find cytotoxic factors in the supernatant of these macrophage cultures. 

---