Antitumor effect of a benzoylphenylurea derivative HO-221

HO-221, N-[4-(5-Bromo-2-pyrimidinyloxy)-3-chlorophenyl]-N'-(2-nitrobenzoyl ) urea is a novel benzoylphenylurea derivative. We had interested in various pharmacological actions of benzoylphenylurea compounds. Therefore, many compounds were synthetized and tested in various screening systems. In the process with these tests, we found HO-221 which showed an excellent antitumor activity. The antitumor activity of HO-221 was judged from the survival time and the tumor weight of experimented tumor-bearing animals. HO-221 preparation was orally administered. The compound exhibited significant effects against various animal tumors (P388, L1210, M5076, LLC, C38, S180, W256), and especially effective against the solid tumors. HO-221 was also markedly effective to MX-1 and LX-1 implanted into nude mice. However, the effect against mouse B16 melanoma was moderate. In addition, HO-221 showed a schedule dependency and once every 4 or 7 days treatments were most effective. The antitumor activities of the compound against advanced L1210 and Lewis lung tumors were examined. Tegafur and ara-C were used as reference drug for the study. Three agents showed the antitumor activities against L1210. Against Lewis lung carcinoma, HO-221 showed both the increase of life span and the tumor growth inhibition. On the other hand, tegafur and ara-C were ineffective for the increase of life span.     

Antimicrotubule effects of the novel antitumor benzoylphenylurea derivative HO-221

The antitumor action of HO-221, a novel benzoylphenylurea derivative, was studied. The in vitro cytotoxic strength of HO-221 was investigated, as measured by IC₅₀ values, compared with those of other drugs with different action mechanisms, using Chinese hamster lung (CHL) cells, mouse leukemia L1210 cells and human promyelocytic leukemia HL-60 cells. Morphological alterations following treatment were observed under a phase contrast microscope, and the mitotic index was determined at regular intervals to check for accumulation of metaphase cells. HO-221 was found to have a very strong toxic effect on all cell types, equal to that of the spindle poisons used as controls. HO-221 also produced the same specific morphological changes as the spindle poisons, with a significant accumulation of metaphase cells. A chromosome analysis of treated cells showed that HO-221 frequently induced polyploid and aneuploid cells, but without accompanying chromosome-breaking activity. An in vivo mouse bone marrow micronucleus assay was also carried out. The assay allowed the in vivo identification of a chromosome breaker or a spindle poison through the measurement of the relative sizes of micronuclei produced and erythrocytes. HO-221 was found frequently to induce relatively large micronuclei, an action regarded as specific to spindle poisons. It was thus demonstrated that HO-221 acts as a spindle poison both in vitro and in vivo. In order to investigate the mechanism of this action, a study of tubulin assembly using purified calf brain tubulin was carried out, which demonstrated clearly that HO-221 inhibits microtubule assembly. A detailed investigation of the action mechanism of HO-221 as a spindle poison is now called for.     

Mechanism of antitumor effect of a benzoylphenylurea derivative, HO-221

HO-221, N-[4-(5-Bromo-2-pyrimidinyloxy)-3-chlorophenyl]-N'-(2-nitrobenzoyl ) urea is a novel benzoylphenylurea derivative. We previously reported HO-221 showed significant antitumor activities against various experimental tumor models, and was especially effective against the solid tumor. In this report we studied the mechanism of action of the compound. The inhibitory activity of HO-221 and 6 kinds of antitumor agents on DNA polymerase alpha was examined in vitro. HO-221 inhibited DNA polymerase alpha activity strongly. From the comparison with IC50 values of individual agents, the inhibitory activity of HO-221 was almost equivalent to aphidicolin and ara-CTP. By double reciprocal plot analysis, the inhibition of HO-221 was found to be non-competitive with the dCTP unlike that of aphidicolin and ara-CTP. Furthermore, HO-221 showed almost no effect on RNA polymerase activity and the protein synthesis. The effect of HO-221 on cell cycle progression of HL-60 cells was examined by flow cytometry analysis. The compound accumulated cells at S phase at a low concentration. The compound showed accumulation of cells in G1, G1-S and G2 + M phases. At higher concentrations, HO-221 increased the G1 phase of tumor cells, stopping the cell cycle progression. Therefore, G1 and S phase accumulation by HO-221 was considered to be correlated with the inhibition of DNA polymerase alpha dependent DNA synthesis. These results suggest that HO-221 is a novel antitumor agent with different mechanism of action from the known antitumor agents.     

Antitumor activity of HO-221, a derivative of benzoylphenylurea against human cancer xenografts in nude mice

HO-221, a derivative of benzoylphenylurea, is a newly developed anticancer drug which was found to show an excellent antitumor effect against transplantable murine tumors by the novel mechanism of action. This study was designed to evaluate the antitumor effect of HO-221 and to establish the optimum regimen, using seven human gastrointestinal and breast cancers xenografted in nude mice. Better antitumor effect of HO-221 by oral administration was observed when it was suspended in larger volume of the vehicle. Moreover, the effect increased by the multiple intermittent administration compared to the single treatment. Best antitumor effect was observed by oral administration of 75 mg/kg (0.1 ml/10 g mouse body weight) repeated twice weekly for a total of eight times or 300 mg/kg (0.2 ml/10 g mouse body weight) repeated once weekly for a total of four times. The antitumor effects of these two regimens were approximately equal except against H-31, the former regimen being more effective. When the tumor growth inhibition rate (IR) over 58% was rated as "effective", the above two regimens were equally effective against 4 of 7 cancers, H-111, H-154, H-143 and H-31. While HO-221 was not effective to a gastric cancer line, H-81, which was most susceptible to the variety of existing anticancer agents, but effective to another gastric cancer line, H-111, which was relatively resistant to conventional cytocidal agents. From the aspect of chemosensitivity spectrum, this drug revealed a rather different pattern compared to other antimetabolites. Although oral administration volume is limited in small animal model, enhancing its antitumor effect may be possible in clinical application by contriving the method of administration. HO-221 is, thus, considered to be a promising drug for further study.     

Antitumor activity of a nitrosourea derivative,CNUA, on murine tumors

Summary The antitumor activity of a new derivative of nitrosourea, 3-[3-(2-chloroethyl)-3-nitrosoureido]-3-deoxy-d-allose (CNUA), against murine tumors was studied. CNUA showed significant antitumor activity against L1210 leukemia, Lewis lung carcinoma, B-16 melanoma and autochthonous lung tumor induced by 1-ethyl-1-nitrosourea. The effect of CNUA, chlorozotocin, and ACNU on the peripheral white blood cell count (WBC) in normal CDF₁ mice was examined. The lowest WBC count occurred 3 days after administration at the therapeutic dose level and the decreased value returned to the normal level 7–14 days following administration of CNUA and chlorozotocin. CNUA also exerted a depressive action on both humoral and cell-mediated immune response to sheep red blood cells determined by the serum hemagglutinin titer, plaque-forming cells in the spleen, and delayed-type hypersensitivity reaction, while the suppression was almost the same or less than that obtained with chlorozotocin when compared at the dose resulting in similar antitumor activity. These findings suggest that the antitumor activity of CNUA was not at all inferior to those of other nitrosoureas. The bone marrow toxicity was moderate and did not last long.     

Combination chemotherapy of HO-221, a derivative of benzoylphenylurea with various anticancer agents against human cancer xenografts in nude mice

Antitumor effect of HO-221, a derivative of benzoylphenylurea, has been previously studied against seven human cancer xenografts in nude mice established and maintained in our laboratory. In this study, the effect of combination chemotherapy was examined with six of the above seven human cancer cell lines. These consisted of four gastric cancers (H-55, H-111, H-81 and H-154), one breast cancer (H-31) and one pancreatic cancer (H-48). HO-221 was used in combination with one of the following widely used anticancer drugs; mitomycin (MMC), adriamycin (ADM), CDDP, VP-16 and 5-fluorouracil (5-FU). When the tumor growth inhibition rate (IR) by combination of two drugs (at 1/2 MTD for each drug) exceeded both of IR obtained separately with single drug at 1/2 MTD, the combination regimen was rated as showing an additive effect. When IR by combination of two drugs at the same dose level exceeded both of IR obtained separately by MTD of each single drug, the regimen was rated as showing a synergistic effect. Histological changes and side-effects were also taken into consideration for the evaluation of the drug. Combination of HO-221 and MMC produced an additive effect against H-55 and H-111, a synergistic effect against H-81. In the treatment of H-31 which was highly susceptible to these drugs, a remarkable effect was shown in both IR and cellular changes even by combination using 1/2 MTD and 1/4 MTD doses. Combination with ADM at 1/2 MTD for both produced an additive effect against H-111 and H-48. Combination at MTD produced a marked antitumor effect against H-111 and a strikingly remarkable combination effect was confirmed. Combination with CDDP produced an additive effect against H-81 and a synergistic effect against H-154. Moreover, the weight loss by this combination regimen was far less than that by single administration of CDDP at MTD. An additive effect was demonstrated by combination with VP-16. Combination with 5-FU produced minimal combination effect. HO-221 was thus found to have a high antitumor effect by combination with various anticancer agents that are at present widely used clinically. HO-221 is expected to be a promising anticancer drug in its clinical application.     

Antitumor activity of a new fluoropyrimidine derivative, 5'-deoxy-5-fluorouridine, against murine and human experimental tumors

5'-Deoxy-5-fluorouridine (5'-DFUR) was evaluated for antitumor activity against four murine tumors (L1210 leukemia, P388 leukemia, Lewis lung carcinoma, and B16 melanoma) and a human mammary carcinoma (MX-1) xenografted in athymic mice. Intraperitoneal administration of 5'-DFUR was ineffective against B16 melanoma implanted intraperitoneally and showed less marked antitumor activity against P388 and L1210 leukemias implanted intraperitoneally or intravenously as compared with that of 5-fluorouracil (5-FU) or 1-(2-tetrahydrofuryl)-5-fluorouracil (FT-207), while oral administration of 5'-DFUR showed a similar or superior antitumor activity to that of 5-FU or FT-207 against L1210 leukemia implanted subcutaneously. 5'-DFUR showed a marked antitumor activity against MX-1 implanted subcutaneously and also showed slight antitumor activity against Lewis lung carcinoma implanted subcutaneously, while 5-FU and FT-207 did not show any significant antitumor activity against these tumors. These results suggest that 5'-DFUR may be worthy of clinical trial against solid tumors, especially cancers of the breast.     

Antitumor activity of T-506, a novel synthetic FUDR derivative, on murine colon cancer and its hepatic metastasis]

T-506 is a novel synthetic FUDR derivative which releases FUDR slowly in vivo. We studied antitumor activity of T-506 by i.v. injection against mouse colon cancer, colon 26. When T-506 was administrated to mice daily, from day 1 through day 10, or every 3 days, on days 1, 4, 7, and 11, after s.c. inoculation of the tumor, the survival period was expanded significantly. The subcutaneous tumor growth was also inhibited according to the dose levels. Then, we compared the therapeutic effects on the experimental hepatic metastasis of colon 26 between T-506, 5'-DFUR and UFT at each maximal tolerable dose; that is, T-506 (0.074 m mole/kg/day; i.v. on days 1, 4, 7, and 10), 5'-DFUR (1.0 m mole/kg/day; P. O. from day 1 to 7), UFT (0.1 m mole/kg/day; P. O. from day 1 to 7). T-506 and 5'-DFUR suppressed completely the metastases of 5 of 6 (83.3%) mice and 6 of 7 (85.7%), respectively. UFT did not show a significant inhibitory effect. However, since the loss of body weight was more marked in T-506 than in the other two drugs, the side effect was thought to be a serious problem. These data suggested that if the side effect could be overcome, T-506 would be useful clinically for the treatment of gastrointestinal cancers or hepatic metastases.     

Preclinical antitumor activity of an alpha-picoline derivative, penclomedine (NSC 338720), on human and murine tumors

Penclomedine, a synthetic alpha-picoline derivative, was identified as a potential antitumor agent in the P388 leukemia prescreen of the National Cancer Institute. Upon further evaluation in the National Cancer Institute in vivo tumor panel, the compound demonstrated good activity against two breast tumors. A single i.p. dose or five daily doses caused partial regressions of advanced-stage s.c. implanted mouse CD8F1 mammary adenocarcinomas. Also, penclomedine administered i.p. on Days 1,5, and 9 caused regression of the human MX-1 mammary carcinoma implanted under the renal capsule of athymic mice. In contrast, penclomedine demonstrated only marginal to moderate activity against the i.p. implanted L1210 leukemia and M5076 sarcoma and was inactive in three additional non-breast tumor models (i.p. B16 melanoma, i.v. Lewis lung carcinoma, and s.c. colon adenocarcinoma 38). Penclomedine administered p.o. and i.p. was equally effective against the subrenal capsule MX-1. Doses given p.o. every fourth day caused complete regression of 39 of 40 advanced-stage s.c. implanted MX-1 tumors but were much less effective against human H82 small cell lung carcinomas (13 of 80 complete regressions). Penclomedine p.o. also inhibited growth of the human MCF-7 and mouse 16/C breast adenocarcinomas. Further studies to support the development of penclomedine to clinical trial are in progress.     

Antitumor activity of mitoxantrone against murine experimental tumors: Comparative analysis against various antitumor antibiotics

Summary 1,4-Dihydroxy-5,8-bis{{{{2-[(2-hydroxyethyl)amino]ethyl}amino}}-9,10-anthracenedione dihydrochloride (mitoxantrone) was tested for antitumor activity against experimental tumors in mice and the results were compared with those of seven antitumor antibiotics: adriamycin (ADM), daunomycin (DM), aclarubicin, mitomycin C (MMC), bleomycin, neocarzinostatin, and chromomycin A₃. The drugs were given IP or IV, in general on days 1,5, and 9 following tumor inoculation. Mitoxantrone given IP at the optimal dose (1.6 mg/kg/day; as a free base) produced a statistically significant number of 60-day survivors (curative effect) in mice with IP implanted L1210 leukemia. The curative effect was not observed with any of the other antibiotics. In the case of IV implanted L1210 leukemia, there was an increase in lifespan (ILS) by more than 100% in the mice following IV treatment with mitoxantrone or DM. In IP implanted P388 leukemia, the curative effect was elicited by IP treatment with mitoxantrone or MMC. In IP implanted B16 melanoma, both the curative effect and a more than 100% ILS in mice that did die were produced by IP treatment with mitoxantrone or ADM. In SC implanted Lewis lung carcinoma, mitoxantrone and ADM administered IV also showed effective antitumor activities and produced a 60% and a 45% ILS, respectively. In conclusion, mitoxantrone and ADM had a wider spectrum of antitumor activity against mouse tumors, including two leukemias and two solid tumors, than did the other drugs; however, mitoxantrone elicited higher antitumor effects than ADM on mouse leukemias, especially on L1210 leukemias. Moreover, mitoxantrone possessed much higher therapeutic indices than ADM against IP implanted P388 (optimal dose/ILS₄₀; >128 versus 15.2) and L1210 (optimal dose/ILS₂₅; 72.7 versus 4.8) leukemias. In addition, mitoxantrone showed moderate activity against DM-resistant L1210 leukemia.     

Antitumor activity of MST-16, a novel derivative of bis(2,6-dioxopiperazine), in murine tumor models

Summary We studied the antitumor activity of newly synthesized bis(1-acyloxymethyl) derivatives of 4,4′-(1,2-ethanediyl)bis(2,6-piperazinedione) using i.p.-i.p. models of P388 leukemia and B16 melanoma. As a result, we found 4,4′-(1,2-ethanediyl)bis(1-isobutoxycarbonyloxymethyl-2,6-piperazinedione) (MST-16) to possess considerable therapeutic activity. MST-16 showed not only marked life-prolonging effects in both P388 leukemia- and B16 melanoma-bearing mice but also a greater therapeutic ratio than did its parent compounds, ICRF-154 and ICRF-159. Further studies revealed that MST-16 has considerable therapeutic activity against a number of other tumors such as ascitic forms of L1210 leukemia, colon 26 adenocarcinoma, and MH-134 hepatoma and solid forms of B16 melanoma, Lewis lung carcinoma, colon 38 adenocarcinoma, and M5076 fibrosarcoma. These results suggest that MST-16 is very promising as an antitumor agent.     

TAT-59, a new triphenylethylene derivative with antitumor activity against hormone-dependent tumors

The antiestrogenic action of TAT-59 {(E)-4-[1-[4-[2-(dimethylamino)ethoxy]-phenyl]-2-(4-isopropyl)phenyl-1-butenyl] phenyl monophosphate} was characterized and compared with that of Tamoxifen (TAM). Its active metabolite, 4-OH-TAT-59, had a high binding affinity to estrogen receptor (ER), present in the cytosol of the uterus of immature rat, similar to estradiol. TAT-59 and 4-OH-TAT-59 inhibited in vitro estrogen-stimulated proliferation of MCF-7 cells at a lower concentration than TAM. In the absence of estradiol, TAT-59 and 4-OH-TAT-59 were effective at a lower concentration than that of 4-OH-Tamoxifen (4-OH-TAM), the active metabolite of TAM. In uterine growth inhibition, the effective dose of TAT-59 was about 3–6-fold lower than that of TAM, in various administration schedules. The minimum effective dose of TAT-59 against in vivo MCF-7 cells was about 3-fold lower than that of TAM. In DMBA-induced rat mammary tumors, TAT-59 inhibited the growth of existing tumors at about a 10-fold lower dose than TAM. Especially in the tumors with low ER levels (10–20 fmol/mg protein), TAT-59 showed a significantly stronger inhibitory effect than TAM. These experiments showed that TAT-59 was more effective in lower doses than TAM, even against the tumors with low ER content.     

Antitumor activity of a novel antitumor antibiotic, quinocarmycin citrate (KW2152)

A novel antitumor antibiotic, 2a,3,4,5,6,6a,7,11b-octahydro-11-methoxy-12-methyl-3,6-imino-1H-2-oxa-11 c- azanaphth(1,2,3-cd)azulene-5-carboxylic acid monocitrate (quinocarmycin citrate; KW2152) was selected for investigation in a number of experimental tumor systems because of its efficacy against P388 leukemia. In the initial studies with P388 leukemia (i.p.-i.p.), KW2152 gave an increase in life span of greater than 80%. The activity was schedule dependent and daily administration was the most effective. KW2152 caused marginal activity against L1210 leukemia, B16 melanoma, and M5076 sarcoma. The effect on cultured cells suggested that KW2152 was not cross-resistant to Adriamycin (ADM) but was cross-resistant to mitomycin C (MMC); however, KW2152 caused prolongation of life span against mice bearing P388/ADM or P388/MMC. In tests against human tumors xenografted s.c. in nude mice, KW2152 significantly inhibited the growth of MX-1 mammary carcinoma with all tumors cured at i.v. doses of 4.4 mg/kg/day and p.o. doses of 26.2 mg/kg/day given daily for 7 days. KW2152 also inhibited distinct human gastric carcinomas, St-4 and St-15 tumors, and colon carcinoma Co-3 by daily administration for 7 days. Against St-4, KW2152 gave a treated versus control percentage of 27, compared to 52 for cis-diamminedichloroplatinum. Against Co-3, KW2152 was at least as effective as MMC, ADM, cis-diamminedichloroplatinum, and bleomycin, giving a treated versus control percentage of 18 at a dose of 8.6 mg/kg/day given daily for 7 days. KW2152 showed growth inhibitory activity against cultured murine tumors and human cells. The order of in vitro efficacy of KW2152 against murine tumors, P388 leukemia greater than L1210 leukemia, B16 melanoma, correlated with the order of the sensitivity on the i.p.-i.p. systems of these tumors. The 50% inhibitory concentrations against P388 leukemia cells were 5.3 X 10(-6) and 1.1 X 10(-7) M after 1 and 72 h exposure, respectively. KW2152 caused significant inhibition of RNA synthesis after a short time exposure. In P388 leukemia cells exposed for 1 h with KW2152, the 50% inhibitory concentration for RNA synthesis was 10(-5) M, 30-fold less than that for DNA synthesis. White blood cell depression or platelet depression was not significant after administration of the i.v. 10% lethal dose given daily for 7 days. Because of its good activity against human mammary tumor MX-1 and some effectiveness against other gastric and colon carcinomas and its water solubility, a novel antitumor antibiotic, KW2152, is being developed as a Phase I anticancer agent.     

A novel combretastatin A-4 derivative, AC-7700, shows marked antitumor activity against advanced solid tumors and orthotopically transplanted tumors.

AC-7700, a novel combretastatin A-4 derivative, suppresses the growth of solid tumors by inhibiting tumor perfusion. We evaluated the antitumor activity of AC-7700 on solid tumors in two experimental models, an advanced tumor model (murine colon 26 (c26) adenocarcinoma, colon 38 (c38) adenocarcinoma, MethA fibrosarcoma, Sarcoma 180 (S180), Lewis lung carcinoma (3LL), human LS180 adenocarcinoma) and an orthotopically transplanted tumor model (c26), compared with that of cisplatin (CDDP). The maximum tolerable dose (MTD) of CDDP suppressed early-stage c26 and c38 tumor growth when treatment was started after the tumor volume (TV) reached 0.2-0.5 cm3, but it showed reduced activity against the same tumors at an advanced growth stage when TV exceeded 2 cm3. At its MTD, AC-7700 was active against all tumors tested except 3LL in both early and advanced growth stages, reducing the tumor mass and having a curative effect in advanced c38 tumors. AC-7700 was also effective on orthotopically transplanted c26 tumors, showing a comparable activity to that on subcutaneous tumors. Unlike flavon acetic acid, which damages tumor vasculature by inducing endogenous tumor necrosis factor-alpha production, AC-7700 potently suppressed the growth of advanced c26 tumors in athymic as well as euthymic mice. These results suggest that AC-7700 is a novel antivascular agent that may have potent activity against advanced-stage cancer in the clinical setting.     

Antitumor effects of gossypol on murine tumors

Summary Since the male antifertility drug, gossypol, was shown to be a specific inhibitor of DNA synthesis at moderately low doses in cultured cells, its antitumor potential has been evaluated in three murine tumor models. The effects of gossypol on tumor growth and the survival of 10-to 12-week-old BDF₁ mice bearing mouse mammary adenocarcinoma 755 (Ca 755) or P388 or L1210 leukemias, all injected IP, were measured. At an optimum dose of 0.5 mg/mouse given as a single injection at 2 days (48 h) after the inoculation of 10⁵ Ca 755 tumor cells, gossypol rendered 66% of the mice free of tumor cells, whereas the remaining 34% died of drug toxicity. The survival rate decreased sharply at doses on either side of the optimum. At suboptimal doses a major proportion of the tumor-bearing mice died of tumor, whereas at higher doses all the animals died of drug toxicity. In other words, the effective dose range of gossypol was rather narrow. The rapidly proliferating mouse leukemias, P388 and L1210, failed to respond to gossypol. Histopathological studies of various organs in the gossypol-treated mice revealed no consistent lesions that could give an indication of organ-specific toxicity of gossypol. The reduction in the myeloid series in the bone marrow of gossypol-treated mice may have been due to depletion rather than direct toxic effect. Further studies are essential to evaluate this compound with regard to its antitumor activity in other murine models.     

Antitumor activity of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxy-camptothec in, a novel water-soluble derivative of camptothecin, against murine tumors

The search for new water-soluble analogues of camptothecin (CPT) with higher activity and less toxicity has led to the development of a novel compound, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxy-camptothecin (CPT-11), which showed significant antitumor activity against a broad spectrum of experimental tumor models by i.p., i.v., or oral administration. When its activity against L1210 was compared with that of CPT and known derivatives, CPT-11 was most effective, giving the highest maximum increase in life span (ILS) and showing good activity over a wide dose range. The antitumor activity of CPT-11 was shown against tumors not only in the ascites form but also in the solid form. Included among the more susceptible murine tumors are S180, Meth A fibrosarcoma, Lewis lung carcinoma, Ehrlich carcinoma, MH134 hepatoma, mammary carcinoma of C3H/HeN mice, L1210, and P388 leukemia. Probable cures of these tumors were induced frequently by CPT-11. The antitumor activity of CPT-11 against i.p.-implanted L1210 was superior to that of Adriamycin in maximum ILS, the number of cured mice, and the therapeutic ratio. CPT-11 at a dose of 100 mg/kg produced an ILS in excess of 300% with five of six mice surviving tumor free, and effected 100% tumor regression at 200 mg/kg, whereas the optimum dose of Adriamycin, 12.5-25 mg/kg, brought about 114-129% ILS with one of six mice surviving. The acute toxicity of CPT-11 was extremely low, particularly in the case of oral administration. CPT-11 is expected to be clinically useful.     

Antitumor activity of a novel nucleoside, 2'-C-cyano-2'-deoxy-1-beta-D-arabinofuranosylcytosine (CNDAC) against murine and human tumors.

The antitumor effects of 2'-C-cyano-2'-deoxy-1-beta-D- arabinofuranosylcytosine (CN-DAC), a synthetic 1-beta-D-arabinofuranosyl-cytosine (ara-C) derivative, were examined and compared with that of ara-C in murine tumors and in various human tumors using three different chemosensitivity tests. CNDAC extended the life span of mice bearing P388 leukemia. CNDAC had a unique in vitro antitumor spectrum for human cancers different from that of ara-C. Compared with ara-C, CNDAC was more effective in 10 human tumors (2 lung, 4 stomach and 4 osteosarcoma), equal in 2 tumors (lung and fibrosarcoma) and less potent in 11 tumors (4 lung, 4 osteosarcoma, bladder, renal and epidermoid). Characteristically CNDAC showed excellent activities against tumors, refractory to ara-C, such as HT-1080 human fibrosarcoma implanted in chick embryos or athymic mice, although its cytotoxicity against HT-1080 was almost equal to that of ara-C. Thus, CNDAC is an interesting and promising agent that should be considered for further detailed preclinical evaluation.     

Cross-resistance of HO-221 and various antitumor agents in sublines of mouse leukemia

HO-221, N-[4-(5-bromo-2-pyrimidinyloxy)-3-chlorophenyl]-N'-(2- nitrobenzoyl) urea is a new benzoylphenylurea derivative. The compound exhibits significant antitumor effects against various animal tumors, and was especially effective against the solid tumors implanted subcutaneously. HO-221 inhibits DNA polymerase alpha activity strongly in vitro. In this study, we examined the cross-resistance of HO-221 to various antitumor agents using sublines of mouse leukemia. HO-221 showed antitumor effects in mice bearing L 1210 or P 388 leukemia resistant to 10 antitumor agents, DM (daunomycin), MMC (mitomycin C), CDDP (cisplatin), 5-FU (5-fluorouracil), Ara-C (cytosine arabinoside), MTX (methotrexate), CPA (cyclophosphamide), CQ (carboquone), ADM (adriamycin) and VCR (vincristine), respectively. These antitumor agents were also effective in P 388 leukemia resistant to HO-221 (P 388/HO-221). Furthermore, CDDP- and MMC-resistant sublines showed a collateral sensitivity to HO-221 in vivo. The grow the inhibitory effects were also noted in vitro in ADM-, CDDP- and MMC-resistant cells by HO-221. However, the in vitro experiments didn't show such collateral sensitivity on the resistant sublines. These results suggest that there is no cross-resistance between HO-221 and other known antitumor agents, and that HO-221 seemed to be worth for evaluating clinical usefulness.     

Combined effect of HO-221 with various antitumor agents against L 1210 leukemia

Combined effect of N-[4-(5-bromo-2-pyrimidinyloxy)-3-chlorophenyl]-N'-(2-nitrobenzoyl ) urea, HO-221, with various antitumor agents was studied using L 1210 leukemia in vivo and in vitro. Ten anticancer drugs were chosen from alkylating agents, antitumor antibiotics, antimetabolites and plant alkaloids each. The combined effect was assessed by comparing ILS (increase of life span) in the combined group with the sum of ILS of each single agent. Synergistic effect was considered to exist if ILS of the combination-treatment group exceeds the sum of those in 2 single-treatment groups. The two-drug combination of HO-221 with cyclophosphamide (CPA), adriamycin (ADM), mitomycin C (MMC), vindesine (VDS), vincristine (VCR) or etoposide showed remarkable synergistic effects with 60-days survivors. However, the combination chemotherapy with antimetabolites, 5-fluorouracil (5-FU) and methotrexate (MTX) showed competitive effects. Moreover, the synergistic cytocidal effect in vitro by the clonogenic assay was observed in combination of HO-221 with the same drug using in vivo test. The present results indicate that HO-221 seems to be a useful antitumor agent in combination chemotherapy.