J. Med. Chem. 1984,27, 701-708
701
Mitomycin C Analogues with Aryl Substituents on the 7-Amino Group Salah M. Sami,? Bhashyam S. Iyengar,? Shirley E. Tarnow,? William A. Remew,*!+William T. Bradner,t and John E. Schurigl Department of Pharmaceutical Sciences, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, and Bristol-Myers Company, Syracuse, New York 13221. Received March 28, 1983 A series of 30 different N7-phenyl-substituted mitomycin C analogues, including 25 new compounds, was prepared from mitomycin A. Seven of these compounds were clearly superior to mitomycin C in activity against P-388 murine leukemia. The para- and the meta-substituted derivatives were subjected to Hansch analysis, which revealed that the lipid-water distribution coefficient 7~ was the only significant factor in determining antitumor potency (MED). The substituent electronegativity factor u was statistically insignificant in determining potency, despite the good correlation of up with the polarographic quinone-reduction potential, These results suggest that diffusion into the tumor cell or access to the receptor is more important than bioreductive activation in determining antitumor potency for this particular group of mitosanes. Fifteen new mitomycin C analogues with heterocycles on the 7-amino group also were prepared. Two of them, containing pyrazolyl and aminopyridyl substituents, were more active than mitomycin C against P-388 murine leukemia. No broad correlations could be made among the antitumor potencies and physicochemical properties for this type of analogue.
A preceding article in this series described mitomycin C analogues with substituted ethylamines a t position 7.l These compounds were chosen in part to permit the study of substituent effects at a site removed from the quinone ring. This study revealed no statistically significant correlation between physicochemical properties, such as hydrophilicity or substituent size, and activity against P-388 leukemia in mice. We had previously noted, in a rough correlation among a variety of 7-substituted mitosanes, that increasing the ease of quinone reduction enhanced potency against P-388 leukemias2 This correlation was not completely satisfactory because other factors, such as hydrophilicity, were ignored. Furthermore, other studies of mitomycin structure-activity relationships, wherein substituents varied at a number of positions on the molecule, had suggested an inverse correlation between antitumor activity and quinone reduction potential3 or the presumably related electronwithdrawing power of s ~ b s t i t u e n t s . ~In view of these factors, it seemed important to conduct a study in which the number and nature of structural changes were strictly limited. This approach would permit a Hansch-type analysis to be made with more confidence than when many structure factors were varied. The N7 para-substituted phenyl analogues of mitomycin C appeared especially valuable for this purpose. Substituent variation would be at a single position, yet it would influence both hydrophilicity and quinone reduction potential. Furthermore, suitable substituent constants are available from the investigations of Hansch. A final reason was that a previous, limited study on anilino analogues of mitomycin C revealed substantial activity against P-388 leukemia for certain compounds of this type, especially the p-hydroxyphenyl anal~gue.~ Preparation of N7-PhenylAnalogues. A series of 14 para-substituted analogues was prepared by treating a solution of mitomycin A in methanol with an excess of the aniline. The reaction progress was followed by thin-layer chromatography, and it was observed that the more nucleophilic anilines, such as p-phenylenediamine and p aminophenol, reacted at a moderate rate, whereas the less (1) Iyengar, B. S.; Sami, S. M.; Remers, W. A.; Bradner, W. T.; Schurig, J. E. J. Med. Chem. 1983, 26, 16. (2) Iyengar, B. S.; Lin, H. J.; Cheng, L.; Remers, W. A.; Bradner, W. T.J. Med. Chem. 1981,24, 975. (3) Matsui, M.; Yamada, Y.; Uzu, K.; Hirata, T. J.Antibiot. 1968, 21, 189. (4) Moriguchi, I.; Komatsu, K. Chem. Pharm. Bull. 1977,25,2800.
(5) Imai, R.; Ashizawa, T.; Urakawa, C.; Morimoto, M.; Nakamura, N. Gann 1980, 71, 560. 0022-2623/84/1827-0701$01.50/0
nucleophilic anilines, such as p-chloroaniline and paminobenzonitrile, reacted so slowly that solid potassium carbonate had to be added to promote the conversion. Even with this promoter, p-nitroaniline reacted very slowly and the yield was poor. The bifunctionality of pphenylenediamine presented a special case in that formation of the dimeric product 30 was possible. We found that when excess p-phenylenediamine was used, the product was the expected monomer 21. However, with 0.5 equiv of p-phenylenediamine, the dimer 30 could be isolated in good yield. The N-phenyl-substituted mitomycin C analogues are listed, along with their physical properties, in Table I. As in our previous preparations of mitomycin analogues, it was necessary to carefully purify the products by preparative-layer chromatography; otherwise, traces of the highly potent and toxic mitomycin A could influence the testing resu1ts.l Certain of the products adhered tenaciously to solvent, even under high vacuum, and they could not be heated because of instability. Thus, some of the elemental analyses must be corrected for the presence of solvent. Evidence for the solvates is given in Table I. A series of seven meta-substituted analogues also was prepared, along with five analogues that were disubstituted in the meta and para positions. Only two compounds with ortho substituents were prepared because substitution at this position appeared unfavorable in the previous s t ~ d y . ~ The preparation of these compounds closely resembled that of the corresponding para analogues. It was necessary to promote the reaction of anilines having electron-withdrawing substituents, and certain of the carefully chromatographed products retained solvents. These analogues also are listed in Table I. Antitumor Activity. The activities of the analogues against P-388 lymphocytic leukemia in mice are given in Table 11. The assays were not all run concurrently, but a mitomycin C standard was run in each assay. Therefore, compounds should not be compared directly with each other but compared on the basis of how each one relates to mitomycin C. This procedure is necessary because of the substantial variation in the maximum therapeutic effect to mitomycin C from one experiment to another. From Table I1 it is evident that seven compounds, 10-12, 15, 16,21, and 25, are clearly superior to mitomycin C. One of them, the p-hydroxy derivative 10, was previously found to have superior activity in this assay: and it is presently undergoing clinical trials in Japan. It also appears to be nonleukopenic.6 In contrast to the previous r e p ~ r twe ,~ (6) Kobayashi, T.; Inaba, M.; Tsukagoshi, S.; Sakurai, Y.; Imai, R.; Morimoto, M. Gann 1981, 72, 950. 0 1984 American Chemical Society
702 Journal of Medicinal Chemistry, 1984, Vol. 27, No. 5
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Table 11. Antitumor Activity and Leukopenia of N5-Aryl-SubstitutedMitomycin C Analoguesa -I___
_ _ _ l _ _ _ l _ _ _
P388 Leukemia ---__
leukopenia % change in TR WBC at opt OD/MED dose on day 3 8 32 -37 32 4 64 32 4 2 1 128 -27 > 64 16 -76 b4 128 64 -34 64 16 >16 16 128 > 64 -64 >8 -17 16 32 128 -40 128 32 16 >16 8 16 -33 32 -45 32 32 -22 16 0 128 2 64 1 82 16 -33 32 -32 32 -15 128 32 16 16 -42
_ _ I---x_________ _ I
max effect, % T/C _ I
compd 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 mit C
-_I____
compd 161 206 181 150 172 167 144 139 128 > 300 356 316 ( 3 ) 181 200 244 >333 (3) 161 167 131 225 >337 ( 3 ) 222 2 39 228 >333 (4) 2 31 322 ( 2 ) 194 172 161 211 211 277 194 172 188 150 144 128 169 178 222 333 ( 3 ) 206 161 178 144-325 (0-2)
I I _ -
Mit C 200 200 319 233 156 278 250 (1) 156 200 144 211 268 (1) 319 206 200 278 278 211 250 213 250 (1) 200 311 311 200 211 294 ( 2 ) 278 233 250 (1) 198 233 206 281 224 219 325 319 156 325 2 67 2 67 161 250 250 178
opt dose, mg/kg 12.8 25.6 12.8 3.2 12.8 12.8 25.6 12.8 25.6 25.6 12.8 12.8 12.8 25.6 25.6 12.8 6.4 3.2 25.6 25.6 12.8 1.6 25.6 6.4 25.6 25.6 25.6 25.6 3.2 25.6 3.2 6.4 12.8 6.4 6.4 25.6 25.6 25.6 25.6 25.6 25.6 25.6 25.6 25.6 12.8 6.4 3.2
MED, mg/kg 1.6 0.8 0.4 0.8 0.2 0.4 6.4 6.4 25.6 0.2
