CAleer
`
`TOUT
`
`reports
`
`PART 2
`
`(SUPPLEMENT)
`
`OCTOBER 1968
`
`Vol. 1, No. 1
`
`US. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE Public Health Service
`
`
`
`

`

`RELATION OF STRUCTURE OF PURINE AND PYRIMIDINE NUCLEOSIDES
`TO ANTITUMOR ACTIVITY *-*
`
`Abraham Goldin, Harry B. Wood, Jr., and Robert R. Engle ?:*
`
`SUMMARY
`
`The structure-activity relations have been reviewed for the purine and pyrimidine nucleoside derivatives
`din the screening program of the Cancer Chemotherapy National Service Center. Data are presented on
`teste
`mpounds in 36 structural groupings. The test systems include leukemia L1210, Walker carcinosarcoma
`648 co
`256, Adenocarcinoma 755, Sarcoma 180, and the Lewis lung tumor in mice, and the KB tissue culture screen.
`Also indicated is the clinical status of the nucleoside derivatives. Twenty-one nucleoside derivatives are in
`the clinical category; 16 of these have shown clinical activity or are being actively processed for the clinic
`and were active in the L1210 system, One of the compounds active in the clinic was inactive in the L1210
`system but was active against KB in tissue culture. One additional compound active in the clinic was inactive
`in the screening systems. Three compoundslisted as inactive in the clinic or too toxic for clinical use were
`active only in the KB system, One hundred twenty-nine additional compounds in which to date there has been
`no clinical interest were active in one or more of the experimental test systems.
`Included were 35 compounds
`active against L1210, one compound active against Walker 256, 69 compounds active against Carcinoma 755,
`one compound active against Lewis lung tumor, and 23 compounds active against KB cells in tissue culture.
`These compounds appeared in 20 of the 36 structural groupings, indicative of the wide range of activity of
`purine and pyrimidine nucleoside congeners. The structure-antitumor relations for the compounds in this re-
`port emphasize the desirability for the further investigation and possible introduction into the clinic of addi-
`tional active nucleoside derivatives. The analysis also indicates that simple structural alterations in this
`class of compounds may lead to wide alteration in biologic and antitumor activity, suggesting the importance
`of additional stress on the synthesis of new congeners.
`
`Since the inception of the screening program of the Cancer Chemotherapy National Service Center, a
`relatively large body of screening data has been accumulated for a wide variety of classes of compounds (1).
`Although in general compounds were introduced into the screening program on an empirical basis without regard
`to their structure, Compounds have been introduced into the program on the basis of the class to which they
`belonged and their specific structure,
`
`1 Received February 7, 1968.
`2 This material was presented in one of a series of meetings on the analysis of structure-activity relations being
`conducted by Chemotherapy, National Cancer Institute (NCI). The members present at the nucleoside meeting
`which was held on May 5, 1967, include the following: F. J. Ansfield, H. H. Baer, B. R. Baker, L. L. Ben-
`nett, Jr., R. W. Brockman, G. B. Brown, J. H. Burckhalter, E, E, Campaigne, P. Carbone, C. C. Cheng,
`L. R. Duvall, R. R. Ellison, R. R. Engle, H..G. Fletcher, Jr., J. J. Fox, E. Frei Ill, M. E. Friedkin, J. L.
`Glass, A. Goldin, L. Goodman, T. T. Grossnickle, C. Heidelberger, J. F. Henderson, R. W. Ihndris, R. B.
`Ing, L. V. Kedda, I. Kline, G. A. LePage, E. L. May, J. A. Montgomery, M. B. Naff, J. W. Newman, C. A.
`Nichol, G. R. Pettit, W. Prusoff, D. Rall, E. Reich, R. K. Robins, L. J. Sargent, S. A. Schepartz, A. W.
`Schrecker, S, M. Schwartz, E. M. Sloane, S. Takahashi, D. W. Visser, V. S. Waravdekar, F. R. White,’
`M. L. Wolfrom, H. B. Wood, and C. G. Zubrod. The authors wish to acknowledgethe interest of the members
`of this conference and the contributions that they have madein the synthesis and investigation of compounds
`listed in this report. The authors are also indebted to all who synthesized and submitted compoundsfor test-
`ing in this program.
`eo Chemotherapy National Service Center (CCNSC), Chemotherapy, NCI, Public Health Service, Bethesda,
`The authors wish to thank Dr. C. Gordon Zubrod, Scientific Director for Chemotherapy, NCI, for his kind in-
`terest in this study. The structure-activity studies of which this forms a part are a direct outgrowth of the
`activity of Acute Leukemia Task Force under the leadership of Dr. Zubrod, The authors wish to acknowledge
`the helpful collaboration of the staff of the CCNSC, including Dr. Schepartz, J. M. Venditti, B. Abbott,
`M. Macdonald, N. Greenberg, N. Ratner, R. Ing, R. Ihndris, M. B. Neff, and M. Flather. The authors wish
`to thank R. Lewis for his diligent assistance in the preparation of this manuscript; M. Gang for her assistance
`with the calculations; and B. Murray, A. Kalikow, and K. Corrado for editorial assistance. The authors would
`like to acknowledge the secretarial assistance of $, Bernstein and L. Foresman.
`
`CANCER CHEMOTHERAPY REPORTS PART 2, VOL. 1, OCTOBER 1968
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`

`

`Over a period of years, with the progress in cancer chemotherapy, there have emerged classes of com-
`pounds for which representatives have shown activity not only in experimental animals but also in the Clinic
`(2-17). These have included the folic acid antagonists, alkylating agents, purines and pyrimidines, and anti-
`biotics. Another important category which has shown potential for treating patients with cancer is the nucleo-
`sides, both purine and pyrimidine nucleosides, including antibiotic nucleosides.
`In view of the interest in
`the nucleosides it was decided to summarize the extant CCNSC data (as of May 1967) for these compounds and
`to examine the structure-activity relations.
`
`After the retrospective analysis by Goldin, Serpick, and Mantel (18) of the relation of CCNSC screening
`data to clinical activity, emphasis was placed on leukemia L1210 and Walker carcinosarcoma 256 as primary
`screens. The available data for the nucleosides in the L1210 and Walker systems were therefore summarized,
`In addition the data were collected for other systems, including Adenocarcinoma 755 (Ca755), Sarcoma 180
`(S180), Lewis lung carcinoma, and the KB tissue culture system.
`
`Prior to the shift in emphasis to the L1210 and Walker screens, new compounds were screened in one
`or more of a wide variety of tumor systems (1,19-22). The gaps in the data stem from either a lack of compound
`or a loss of interest in the compound as the result of the compound failing to pass the initial primary screen,
`
`The structure-activity studies, of which this report is one of a series, may be important to (1) the
`screening program in determining what additional testing ought to be done—it may identify the gaps in the
`data and indicate which of these gaps ought to be filled; (2) the chemist in helping him to decide what new
`structures might best be synthesized; (3) the biochemist in determining which structures are worthy of detailed
`studies of mechanism of action; (4) the pharmacologist in deciding which structures are worthy of additional
`pharmacologic investigation; and (5) the clinician in helping to decide which compounds are of greatest poten-
`tial interest,
`
`Structure-activity analyses are important in order to uncover new drugs and the structural character-
`istics which may lead to the improvement of drug effectiveness. The important progress in recent years in
`the treatment of acute leukemia and allied disorders (23-28) provides additional stimulus for the search for new
`types of agents and for structure-activity analyses in active groups.
`
`METHODS
`
`The methods are those used in the CCNSC screening program (19-21). The tumor systems are outlined
`in table 1. The L1210 system uses survival time of the animals as the index of drug effectiveness. A 30% in-
`crease in the survival time of the treated animals relative to the controls is indicative of a significant and re-
`producible chemotherapeutic effect against L1210. For the tumors Walker carcinosarcoma 256, Ca755, $180,
`and Lewis lung carcinoma, a 75% inhibition of tumor growth relative to the untreated controls was taken as the
`level of inhibition indicative of drug activity.
`(In the CCNSC protocols the level of activity required is more
`extensive, but for this analysis, as for the retrospective study by Goldin, Serpick, and Mantel [18] 75% in-
`hibition was considered to be satisfactory.) The KB system is in essence a cytotoxicity test which is indica-
`tive of biologic activity for a compound,
`In this system 50% inhibition of growth, as reflected by inhibition of
`protein production, at 1 ug/ml or less was taken as the level of activity. However, 50% inhibition in the KB
`system in the range of 1 to 10 pg/ml suggests that the compound may be of biologic interest.
`
`EXPERIMENTAL RESULTS
`
`The experimental results are summarized in table 2, in which the compounds are listed in 36 groups.
`
`1. Uracil Ribosides
`
`In addition to uracil there were 21 compounds in this group (entry Nos. 88551-88572), involving substi-
`tutions in both the ribose and the uracil moieties. Only one compound metthe criterion for activity in the
`L1210 system, 5-diazouridine (NSC-70390, entry No. 88566). Two additional compounds, though not definitely
`active in the L1210 system, did show sufficient activity to warrant interest: 1-8-py-ribofuranosyl isobarbituric
`acid (NSC-73376, entry No, 88560), which has an oxygen at position 5, and uridine 5'-pyrophosphate, gluco-
`pyranosyl ester (NSC-20269, entry No. 88570). The other compounds showedno activity in the in vivo systems
`in which they were tested, nor were they active against KB cells in tissue culture, The uracil ribosides as 4
`class were relatively nontoxic.
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`CANCER CHEMOTHERAPY REPORTS PART 2
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`2
`
`uracil 9'-Deoxyribosides
`In addition to the free base 5-fluorouracil there were 23 uracil 2'-deoxyribosides (entry Nos. 88573-
`9859 6). Most of them lacked test data in 2 or more of the systems. 5-Fluorouracil (NSC-19893, entry No.
`38573) was active against L1210, Ca755, S180, and KB cells in tissue culture, Although 2'-deoxyuridine
`NSC-23615, entry No, 88574) appeared to be inactive, halogenated derivatives of this compound were gener-
`ally effective in the various test systems.
`2'-Deoxy-5-fluorouridine (S-FUDR, NSC-27640, entry No. 88576) was a notably active compound in
`this series.
`It definitely increased the survival time of mice with L1210, and resulted in a marked inhibition
`of growth of the Ca755, $180, and Lewis lung tumors.
`It elicited borderline inhibition of growth of Walker 256,
`and was also active in the KB system,
`In contrast to 5-FUDR(the 2'-deoxy- 5-8-p-ribofuranoside), the 2'-deoxy-5-fluoro-e-p-ribofuranoside
`(NSC-66259, entry No. 88575) was inactive against L1210 and $180 in vivo, as well as against KB in tissue
`culture. No other data were available on the alpha riboside,
`2'~Deoxy-5-trifluoromethyluridine (FgTDR, NSC-75520, entry No. 88595) appeared to be even more ac-
`tive than 5-FUDRin the L1210 system. As with 5-FUDR, F,TDR exerted a partial inhibitory effect against
`Walker 256.
`It was almost as effective as 5-FUDR against Ca755 but less effective against 5180; however,
`F, TDR was tested at only one dose level in the $180 system. No test data were available in the Lewis lung
`or KB systems.
`
`A compound of possible interest was the 3'-acetate derivative of 5-FUDR (3'-acetate 5-FUDR, NSC-
`407335, entry No. 88577). There were no test data in the animal tumor systems, but the compound was active
`in KB tissue culture. Similarly, the 5-bromo-5,6-dihydro-6-methoxy derivative of 5-FUDR (5-bromo-5 , 6-di-
`hydro-6-methoxy-5~-FUDR; NSC-80870; entry No. 88584) was active in KB tissue culture; in addition it was ac-
`tive against the Lewis lung tumor. Both of these compounds warrant additional testing. Other fluorinated de-
`rivatives (entry Nos. 88578-88582) were less active against KB in tissue culture; in vivo data were not avail-
`able, The loss of activity in the L1210 system when the primary hydroxyl group is converted to a carboxyl
`group at the 5*' position of 5-FUDR (NSC-103704, entry No. 88583) is of interest and should besubstantiated.
`
`Substitution of bromine instead of fluorine in the 5 position as in 5-bromo-2'-deoxyuridine (5-BUDR, NSC-
`38297, entry No. 88585) resulted in a loss of activity against L1210 and the other tumors. However, the iodo
`derivative, 2'-deoxy-5-iodouridine (5-IUDR, NSC-39661, entry No. 88587) did retain effectiveness in the
`L1210 system.
`It was less active than 5-FUDR in Ca755 and $180. Both S-BUDR and 5-IUDR were considerably
`less toxic than 5-FUDR, as indicated by the marked increase in their optimal doses, They were also less toxic
`than 5-FUDR in the KB tissue culture system.
`
`In view of the significant activity and the clinical interest in 5-FUDR and 5-IUDR, it would be desirable
`to test more structural analogs of these compounds,
`
`3, Uracil Arabinosides and Uracil Lyxosides
`None of the 10 uracil arabinosides and uracil lyxosides (entry Nos. 88597-88606) showed definite evi-
`dence of activity, when tested in the in vivo tumor systems, or against KB in tissue culture, The lack of ac-
`tivity of uracil 1-8-p-arabinofuranoside (NSC-68928, entry No. 88597) was in marked contrast to the activity
`observed with cytosine 1-§-p-arabinofuranoside (NSC-63878, entry No. 88635), 5-Fluorouracil 1-8~-p -arabinofu-
`ranoside (NSC-406444, entry No. 88599) given as a single injection was inactive against L1210; in other studies
`(7,29), however, it was effective in the treatment of leukemia B82. 5-Bromouracil 1-p-p-arabinofuranoside
`(NSC-82222, entry No. 88600) and 5-iodouracil 1-f-p-arabinofuranoside (NSC-82221, entry No. 88601) were
`tested only in the KB system and were found to be nontoxic. Because of the general clinical interest in halo-
`genated derivatives, it is suggested that additional testing be done with the fluoro, bromo, and iodo derivatives.
`
`The two lyxofuranosyl derivatives (NSC-88790, entry No. 88605; and NSC-88791, entry No. 88606)
`were inactive in the L1210, $180, and Lewis lung systems and against KB. They were not tested against Walker
`256 and Ca755.
`
`4. Uracil Hexopyranosides
`Of the 23 uracil hexopyranosides (entry Nos. 88607-88629}, only the complex (2-p-p-glucopyranosyl)oxy
`derivative (NSC-100050, entry No. 88624) was tested in the L1210 system.
`It was inactive at the one dose
`level tested. No compounds were tested against the other in vivo screening systems, and none of them had
`
`VOL. 1, NO. 1, OCTOBER 1968
`~
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`definite activity in the in vitro KB tissue culture system, The 2',3',4',6'-tetraacetate, 4-methoxy derivative
`of a 1-B-p-glucopyranoside (NSC-401826, entry No. 88609) had a KB rating of 11 which was suggestive of bio-
`logic activity.
`
`In vivo test data would have to be obtained in order to evaluate this class of compounds.
`
`5. Uracil Miscellaneous
`
`The 4 compoundsin this category (entry Nos. 88630-88633) were inactive in the KB tissue culture sys-
`tem. All 4 were pyranyl derivatives of uracil. Two compounds (NSC-92707, entry No, 88631; and NSC-92709,
`entry No. 88632) were inactive against L1210 and against other tumor systems where tested. All compounds,
`however, were tested at only one dose level.
`
`6, Cytosine Furanosides
`
`In addition to cytosine itself, 17 cytosine furanosides were listed in this series (entry Nos. 88634-
`88651). The free base cytosine (NSC-27787, entry No. 88634) was tested against $180 and was inactive.
`Cytosine 1-B8-p-arabinofuranoside (Ara-C, NSC-63878, entry No. 88635), a drug of clinical interest, was highly
`active against L1210.
`It was inactive in the screen against Walker 256 and Lewis lung carcinoma, but was ac-
`tive against Ca755 and S180.
`It was also active in vitro against KB cells.
`
`The 2',3',5'-triacetate derivative of cytosine 1-B-p-arabinofuranoside (2',3',5'-triacetate Ara-C,
`NSC-93150, entry No. 88636) given orally was active against L1210.
`In other studies against advanced leu-
`kemia L1210° the 2',3',5'-triacetate derivative was less effective than cytosine 1-§-p-arabinofuranoside when
`administered subcutaneously, but the 2 agents had similar antileukemic activity when given orally.
`Thetri-
`acetate derivative was active in the KB system but showed reduced activity against S180. The 2',3',5'-triacetate
`derivative of V-acetylcytosine 1-f-pn-arabinofuranoside (2',3',5'-triacetate V-acetyl-Ara-C, NSC-92717,
`entry No. 88637) was also quite active in the L1210 system and active against KB cells. The increased opti-
`mal dose for leukemia L1210 (1350 mg/kg) was in decided contrast to the 20-mg/kg optimal dose for cytosine
`1-B-p-arabinofuranoside.
`
`The 5'-phosphate derivative of cytosine 1-8-p-arabinofuranoside (5'-phosphate Ara-C, NSC-99445,
`entry No. 88638) (30) produced a 250% increase in the survival time of mice with advanced L1210;® however,
`in the advanced L1210 study the phosphorylated derivative was approximately as effective as cytosine 1-p-p-
`arabinofuranoside.® No data were available for this compound in the primary screen against early L1210.
`
`the 5-fluoro derivative of cytosine
`One additional arabinofuranoside was active in the L1210 system:
`1-8-p~arabinofuranoside (5-fluoro-Ara-C, NSC-529180, entry No. 88639). Data were not available for this
`compound in the other screening systems.
`
`It should be noted that the 5-methyl derivative of cytosine 1-$-p-arabinofuranoside (NSC-96372, entry
`No. 88640) was inactive in the L1210 system andin the in vitro KB tissue culture system. However, the com-
`pound was tested at only one dose level in the L1210 system; it is suggested that a series of dose levels of
`this drug be studied,
`
`The 5-fluoro derivative of 2'-deoxycytidine (NSC-48006, entry No. 88649) was active in the L1210 sys-
`tem and against $180. 5-Bromo-2'-deoxycytidine (NSC-61765, entry No. 88650) was active against Ca755 but
`inactive in L1210 and in other in vivo systems.
`
`The other cytosine furanosides (entry Nos. 88641-88648 and 88651) were inactive in the systems in
`which they were tested; however, there were wide gaps in the data,
`
`7, Cytosine 2'=Deoxypyranosides
`
`There were only 2 compounds in this series (entry Nos. 88652-88653). Both were inactive in the KB
`system, and no data on in vivo studies were available.
`
`® Kline, I., Tyrer, D. D., Gang, M., Venditti, J. M., and Goldin, A. To be published.
`® Schrecker, A. W., and Goldin, A. To be published.
`
`CANCER CHEMOTHERAPY REPORTS PART 2
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`

`r g,
`
`cytosine Glucopyranosides
`It will be
`All 7 cytosine glucopyranosides (entry Nos. 88654-88660) were inactive in the KB system.
`ary to obtain data on in vivo tests in order to make anyfurther structure-activity analysis for this group
`necess
`if compounds.
`Cytosine 2 '-~Aminopyranosides
`There were 13 compounds in this series (entry Nos. 88661-88673). Twelve compounds were tested only
`he KB system, and none met the requirement for activity. Of these, 2'-acetamido-2'-deoxycytosine 1-£-
`de (NSC-401829, entry No. 88664) had a KB rating of 13, suggesting possible biologic activity.
`dnote
`p-glucopyranosi
`The other compound in this series (NSC-24832, entry No. 88667) was not tested against KB but was inactive in
`the Ca755 and:S180 systems.
`
`9.
`
`10, Cytosine Miscellaneous
`None of these 5 compounds (entry Nos. 88674-88678) showed activity in the systems in which they were
`tested. However, NSC-402189 (entry No. 88677) had a rating in the KB system (1.3) approaching the level of
`activity acceptance; there were no data for this compound in any of the in vivo tumor systems. Another com-
`nd (NSC-401861, entry No. 88676) had a rating of 9.5 in the KB system, suggesting possible biologic ac-
`ou
`r
`r, it was not active against L1210 and the other systems tested.
`tivity; howeve
`71. Hypoxanthine Ribosides
`
`Twelve hypoxanthine ribosides and the free base were tested (entry Nos. 88679-88691), The free base,
`hypoxanthine (NSC-14665, entry No. 88679), was inactive against L1210, Ca755, $180, and Lewis lung tu-
`mors, as well as against KB in tissue culture.
`
`Inosine (NSC-20262, entry No, 88680) was inactive against L1210, Ca755, and §180. One of the com-
`pounds in this series, a complex codehydrogenase I derivative (NSC-20271, entry No. 88687), was active in
`the L1210 system. The 10 additional hypoxanthine ribosides in this series were inactive in the systems in
`which they were tested.
`
`No data were available for the hypoxanthine ribosides in the Walker 256 system, and only 5 of the 13
`compounds were tested in the KB system. Where the substituents in this series were in the 6-hydroxy group
`(NSC-30606, entry No. 88688; NSC-88727, entry No. 88689; and NSC-31144, entry No. 88690) the available
`data were quite limited,
`
`12. Hypoxanthine Arabinosides
`
`There were 5 compoundsin this series (entry Nos. 88692-88696). Four of them, including hypoxanthine
`9-8-p-arabinofuranoside (NSC-405122, entry No. 88695) were tested at one dose level in the L1210 system
`and were inactive. The compounds were also inactive in the other systems in which they were tested. They were
`also relatively nontoxic as shown by the high dosage which could be used. Hypoxanthine 9-6-p-arabinofurano-
`side has been reported to be almost as lethal to purine-requiring #scherichta coll as adenine 9-§-p-arabino-
`furanoside (Ara-A, NSC-404241, entry No. 88930) (7) and should therefore undergo further testing.
`
`13, Hypoxanthine Miscellaneous
`
`The 15 compounds in this group (entry Nos. 88697-88711) have a wide variety of substituents in the
`sugar moiety, and in some cases substitution was made in the hypoxanthine base. Data were available for
`only 5 of the compounds in the L1210 system, and no compounds weretested in the Walker system. The com-
`pounds were ineffective in the systems in which they were tested, but there were wide gaps in the available
`data,
`
`14, 6-Mercaptopurine Ribosides
`
`There were 59 compoundsin this group (entry Nos. 88712-88770). The parent compound, 6-mercapto-
`purine (6-MP, NSC-755, entry No. 88712), was active against L1210, Walker 256, and Ca755.
`In addition,
`it was active in vitro in the KB system. 6-Mercaptopurine 9-§-p-ribofuranoside (6-MPR, NSC-4911, entry
`No. 88713) also was active in the L1210, Walker 256, and Ca755 systems.
`In addition it had definite anti-
`tumor activity in the $180 system, and like the free base it inhibited KB in tissue culture.
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`a
`
`A series of compoundsis listed (entry Nos. 88714-88744) in which substitutions were made in the sugar
`moiety. None of the compounds appeared to be more effective than 6-MP or 6-MPR. Compounds which were
`approximately as effective as 6-MP and 6-MPR against L1210 included the 2',3', 5'-triacetate derivative of
`6-mercaptopurine 9-8-p-ribofuranoside (2',3',5'-triacetate 6-MPR, NSC-66385, entry No. 88715), the 2' ,3',5'-
`trivalerate derivative (2',3',5'-trivalerate 6-MPR, NSC-77495, entry No. 88717), the 2',3',5'-tributyrate
`derivative (2',3',5'-tributyrate 6- MPR, NSC-76952, entry No. 88718), the 2',3',5'-tribenzoate derivative (2',-
`3',S'-tribenzoate 6-MPR, NSC-28416, entry No, 88722), the 2',3',5'-tris(p-nitrobenzoate) derivative [2',3',5'-
`tris(p-nitrobenzoate) 6-MPR, NSC-76126, entry No, 88725], the 5'-phosphate butyl ester (5'-butyl phosphate 6-
`MPR, NSC-45635, entry No. 88733), and the 5'-phosphate diethyl ester (5'-diethyl phosphate 6-MPR, NSC-
`40634, entry No. 88734), The 5'-phosphate diphenyl ester (S'-diphenyl phosphate 6-MPR, NSC-40632, entry
`No. 88739) had somewhat reduced activity. These compounds which were active in L1210 usually showed activ-
`ity in one or more of the Walker 256, Ca755, $180, and KB systems in which they were tested,
`A number of compounds not tested or not active against’ L1210 were active against Ca755, The 2',3'-
`diacetate derivative of 6-mercaptopurine 9-8-p-ribofuranoside (2',3'-diacetate 6-MPR, NSC-408371, entry
`No. 88714) was active against Ca755 and KB, but was not tested in the other systems. The activity of the
`2',3',5'-triisobutyrate derivative (2',3' ,9'-triisobutyrate 6- MPR, NSC-78308, entry No. 88716) in the Ca755,
`$180, and KB systems (despite the lack of activity against L1210) suggests that this compound is worthy of
`additional testing. The 2',3',5'-tri-p-anisate derivative (2',3',5'-tri-p-anisate 6-MPR, NSC-76519, entry
`No. 88723) was also active in the Ca755 system, but was inactive at the one dose level tested against L1210,
`The 2',3',5'-tris(p-chlorobenzoate) derivative (2',3' ,5'~tris(p-chlorobenzoate) 6-MPR, NSC-76520, entry No.
`88724) inhibited Ca755, but was ineffective at the one dose level tested against L1210. The 5'-phosphate
`derivative (5'-phosphate 6-MPR, NSC-46024, entry No. 88731), and the 5'-phosphate ethyl ester (5'-ethyl
`phosphate 6-MPR, NSC-45636, entry No. 88732) were active against Ca755 and also against KB; neither com-
`pound was tested in the other systems. The 5'-phosphate dibutyl ester (5'-dibutyl phosphate 6-MPR, NSC-
`40633, entry No. 88735), and the 5'-phosphate phenyl ester (5'-phenyl phosphate 6-MPR, NSC-45637, entry
`No. 88737), also active against Ca755, were not tested against L1210.
`
`A numberof other substitutions in the sugar moiety led to loss of antitumor effectiveness, as reflected
`in a failure to increase the survival time of mice with L1210 or failure to produce appreciableinhibition of
`solid tumor growth in the other tumor systems. Also with the exception of NSC-85389 (5'-(p-nitrophenyl) phos-
`phate 6-MPR, entry No, 88738) and NSC-405278 (2'-phosphate 6-MPR, entry No. 88744), no activity was noted
`in the KB system.
`
`Apparently, if the substitution in the sugar moiety is too cumbersome it may lead to a loss of activity:
`3 such compounds were the 2',3',5'-trilaurate derivative (NSC-76123, entry No. 88719), the 2' ,3',5'-trioleate
`derivative (NSC-76124, entry No. 88720), and the 2',3' ,9'-tristearate derivative (NSC-76949, entry No. 88721).
`With these compounds theloss of activity may be related to failure of penetration of the drugs into the tumor
`cells,
`
`The one 9-6-,-ribofuranosyl-6-mercaptopurine derivative listed (NSC-92428, entry No. 88745) was in-
`active against KB in tissue culture and was not tested in the other systems,
`
`Compounds NSC-76465 through NSC-91745 (entry Nos. 88746-88760) have alterations involving the
`6-sulfhydryl (SH) group. Substitution of a methyl group into the SH group of 6-MPR (6-methyl-MPR, NSC-
`40774, entry No. 88747) permitted retention of activity against L1210. The methyl derivative was also active
`in the KB system, However, there did appear to be a loss in activity against Walker 256, Ca755, and $180.
`A second compound involving the substitution of a methyl group into SH also involved the introduction of a
`5'-phosphate group (5'-phosphate 6-methyl-MPR, NSC-407746, entry No. 88748); with this compound there was
`activity in the KB system, but no other data were available. Substitution of an ethyl group for the hydrogen in
`the SH moiety (6-ethyl-MPR, NSC-39368, entry No. 88749) resulted in an apparent loss in activity against
`L1210, but only one dose level of the drug was tested. The compound was active against Ca755 and had bor-
`derline activity against the $180 tumor. The 6-propylthiopurine derivative (6-propyl-MPR, NSC- 39044, entry
`No. 88750) was not tested against L1210, but it too was active against Ca755. 6-Allylthiopurine 9-B-p-ribo-
`furanoside (6-allyl- MPR, NSC-39367, entry No. 88751) was possibly more active in the L1210 system than
`either 6-MP or 6-MPR; this compound was also active against the Ca755 and Walker 256 tumors. At the one
`dose level tested the 6-acetonylthio derivative (6-acetonyl-MPR, NSC-39045, entry No. 88757) was active
`against L1210 and against Ca755. The nitroimidazolylthio derivative [6-(1-methyl-4-nitroimidazol-5-yl) -MPR,
`NSC-91745, entry No. 88760] was not tested in vivo; it was active against KB cells,
`
`Other complex substitutions in SH may result in loss of L1210 activity. This was noted with NSC-27307
`(entry No. 88754), NSC-39043 (6-cinnamyl-MPR, entry No. 88756), and NSC-39848 (6-cyanomethyl-MPR, en-
`try No. 88759).
`
`CANCER CHEMOTHERAPY REPORTS PART 2
`
`

`

`Most of the analogs of 6-MPRthat have substitutions for the hydrogen in the SH group alone or accom-
`dditional substituents in the sugar moiety were active in the Ca755 system. Among those listed in
`anied by e C-40630 (6-cyclopentyl-MPR, entry No. 88752), NSC-26273 (6-benzyl- MPR, entry No. 88753),
`ee hae? [ 6-(2-methyl-1-naphthyl)methyl-MPR, entry No. 88755] and NSC-41847 [6-(2-thenyl)-MPR, entry
`NSC-
`No. 88758].
`of the remaining compounds in the 6-MPriboside series, NSC-46786 through NSC-76932 (entry Nos.
`-88770), only 2 were tested in any of the tumor systems, and they were negative. Five compounds, NSC-
`88761 r 6-MPRphosphate (5' + 5') 6-MPR, entry No. 88762], NSC 409841 [5-FUDR phosphate (3' > 5') 6-MPR,
`ee 38763], NSC-409289 [5-FUDR phosphate (5' ~ 5') 6-MPR, entry No. 88764], NSC- 407338 [thymidine
`entry el (5! + 5') 6-MPR, entry No, 88765], and NSC-45404 (1-[2-(6-MP)ethyl]-6-MPR, entry No. 88769)
`ene in the KB system, and it is suggested that further testing in the tumor systems be done. The pos-
`a, Ae of the phosphate in entry Nos. 88762-88765 in relation to KB activity awaits clarification.
`«Mercaptopurine (Nonribose) Nucleosides
`
`15.
`
`at onpo (entry Nos. 88771-88789) in this category included deoxy sugars, arabinofuranosides,
`Jyxofuranosides, xylofursnostdes glucofuranosides, glucopyranosides, galactofuranosides, allofuranosides ,
`and one 4'-thioribofuranoside.
`2'-Deoxy-6-mercaptopurine 9-8-y-ribofuranoside (2'-deoxy-6-MPR, NSC-409366, entry No. 88771)
`was active against L1210, Walker 256, and KB cells in tissue culture. 6-Mercaptopurine 9-§-p-arabinofurano-
`side (6-MPAra, NSC-406021, entry No. 88773) was possibly more active than 6-MP or 6-MPR against L1210.
`This compound was also very active against Ca755 but was inactive in the KB system. 6-Mercaptopurine
`9-w-p-arabinofuranoside (NSC-99193, entry No. 88774) appeared to be inactive against L1210; however it was
`tested at only one dose level. The other alpha derivative, the 2',3',5'-triacetate derivative of 6-mercapto-
`purine 9-g-p-arabinofuranoside (NSC-98668, entry No. 88775) was also inactive in the L1210 system and failed
`to inhibit tumor growth in the Walker 256 system.
`
`The 2',3'-diacetate derivative of 5'-deoxy-6-mercaptopurine 9-8-p-xylofuranoside (NSC-101586, entry
`No, 88782) was inactive against L1210, as was 6-mercaptopurine 9-B-p-galactofuranoside (NSC-84636, entry
`No. 88784).
`
`The tetraacetate derivative of 6-propylthiopurine 9-8-p-glucopyranoside (NSC-80919, entry No. 88789)
`was active against L1210 but inactive in both the $180 and KB systems. No other data on animal tests were
`available for the compounds in the 6-MP (nonribose) nucleoside series.
`
`One of the compounds, 6'-deoxy-6-mercaptopurine 9-§-p-allofuranoside (6'-deoxy-6-MPAllo, NSC-
`409352, entry No. 88787), was active in the KB system and should be tested in vivo against the animal tumors.
`The 9-B-p-lyxofuranosyl derivative (NSC-92429, entry No. 88777) hada rating of 3.0 in the KB system, sug-
`gesting that the compound is biologically active.
`
`16. 6-Mercaptopurine: Nonsugar Analogs
`
`There were 15 compounds listed in this category (entry Nos. 88790-88804) and all were 9-tetrahydro-
`pyranyl or 9-tetrahydrofuryl derivatives. One of these, a 9-tetrahydrofuryl derivative of 6-mercaptopurine
`[ 9-(tetrahydro-2-furyl)-6-MP, NSC-45153, entry No. 88790], was quite active in the L1210 system and was
`active against Ca755. Two tetrahydropyranyl derivatives [9-(tetrahydro-2-pyranyl)-6-MP, NSC-33186, entry
`No. 88794; and 9-(tetrahydro-2-pyranyl)-6-butyl-MP, NSC-38305, entry No. 88798] showed borderline ac-
`tivity against L1210 and were also active against Ca755. Nine other compounds were active in the Ca755 sys-
`tem. This type of structure appears to be worthy of additional testing.
`
`17, 6-Halopurine Nucleosides
`
`Including the free base 6-chloropurine, there were 23 compounds in this group (entry Nos. 88805-88827).
`The freé base, 6-chloropurine (6-CIP, NSC-744, entry No. 88805), was active against both L1210 and Ca755
`but was inactive in the Walker 256, $180 and KB systems.
`
`6-Chloropurine 9-8-p-ribofuranoside (6-ClPR, NSC-4910, entry No. 88806) and its 2',3',5'-tribenzoate
`derivative (NSC-88182, entry No. 88807) were inactive against L1210, 6-CIPR, however, retained its effective-
`ness against Ca755 and was active against KB cells. 6-Bromopurine 9-8-p-ribofuranoside (NSC-62630, entry No.
`88808) and 6-iodopurine 9-g-p-ribofuranoside (6-IPR, NSC-66384, entry No. 88809) were also inactive against
`
`VOL. 1, No. 1, OCTOBER 1968
`
`

`

`L1210 and did not meet the requirement for activity against Ca755. 6-Chloro-2'-deoxypurine 9-p-p-ribofuran-
`oside (NSC-409824,