Implanted L1210 Leukemia Research Articles

Preclinical efficacy evaluations of XK-469: dose schedule, route and cross-resistance behavior in tumor bearing mice.

XK-469 is advancing to Phase I clinical trials. Preclinical studies were carried out to assist in clinical applications. DOSE-SCHEDULE ROUTE TESTING: Single dose i.v. treatment with XK-469 produced lethality (LD20 to LD100) above 142 mg/kg. Optimum treatment required total dosages of 350 to 600 mg/kg. Furthermore, high individual i.v. dosages (100 to 142 mg/kg) were poorly tolerated, producing substantial weight loss (8 to 18% of body weight), poor appearance, and slow recovery (8 to 12 days). A 1-hour infusion of dosages more than 140 mg/kg, or BID injections 6 hrs apart, did not reduce lethality. However, lower individual dosages of 40 to 50 mg/kg/injection i.v. were well tolerated and could be given daily to reach an optimum total dose with minimal toxicities. Likewise, 75 mg/kg/injection i.v. could be used every other day to reach optimal treatment. The necropsy profiles of deaths from toxic dosages were essentially identical regardless of schedule (deaths 4 to 7 days post treatment). The profiles were: paralytic ileus or gastroparesis; GI epithelial damage; and marrow toxicity. Interestingly, the key lethal events were rapidly reversible and simple to overcome with lower dosages given daily or every other day. Based on these results, the high dose, Q21 day schedule should be avoided in clinical applications. Instead, a split dose regimen is recommended (e.g., daily, every other day, or twice weekly). XK-469 was also well tolerated by the oral route, requiring 35% higher dosages p.o. to reach the same efficacy and toxicity as produced i.v.. CROSS-RESISTANCE STUDIES: XK-469 resistance was produced by optimum treatments of i.v. implanted L1210 leukemia over seven passage generations. This leukemia subline (L1210/XK469) had reduced sensitivity to VP-16 (with a 4.0 log kill in i.v. implanted L1210/XK469 compared to an 8.0 log kill against i.v. implanted L1210/0). It also had a reduction in the sensitivity to 5-FU (with a 2.0 log kill in the implanted L1210/XK469 compared to a 4.0 log kill against i.v. implanted L1210/0). Other agents were approximately as active against the resistant tumor, including: Ara-C, Gemzar, Cytoxan, BCNU, DTIC, and CisDDPT. No case of collateral sensitivity was observed; i.e., no agent was markedly more active against the resistant subline L1210/XK-469 than against the parent tumor in mice.

Antitumor activity of halogen analogs of phosphoramide, isophosphoramide, and triphosphoramide mustards, the cytotoxic metabolites of cyclophosphamide, ifosfamide, and trofosfamide.

A series of halogen analogs of phosphoramide mustard, isophosphoramide mustard, and triphosphoramide mustard, the cytotoxic metabolites of the antitumor drugs cyclophosphamide, ifosfamide, and trofosfamide, respectively, was evaluated in vitro against human tumor cell lines and in vivo against experimental tumors to investigate the effect of replacement of chlorine with bromine or fluorine on the antitumor activity of the parent phosphoramide mustards. In the experimental tumors L1210 leukemia, B16 melanoma, mammary adenocarcinoma 16/C, and ovarian sarcoma M5076, the antitumor activity of the analogs was observed to be generally comparable with that of the parent mustards when chlorine was replaced by bromine but uniformly lower when chlorine was replaced by fluorine. Furthermore, the monobromo analog of isophosphoramide mustard displayed equal or somewhat greater activity in comparison with cyclophosphamide when evaluated against subcutaneously implanted L1210 leukemia with intraperitoneal drug treatment and against mammary adenocarcinoma 16/C.

Antitumor properties of 2(1H)-pyrimidinone riboside (zebularine) and its fluorinated analogs

2(1H)-Pyrimidinone riboside (zebularine, 1b) and its 5-fluoro (6b) and 2'-ara-fluoro (7b) analogues have been synthesized and evaluated in vivo as antitumor agents. Zebularine provides increase in life span (ILS) values of ca. 70% against intraperitoneal (ip) murine B16 melanoma and 50% against P388 leukemia. This compound is active when administered either ip or orally against ip or subcutaneously implanted L1210 leukemia, producing ILS values of about 100% at an optimum dose of 400 mg/kg. 1b is also active (60% ILS) against ara-C-resistant L1210. The analogous unsubstituted purine riboside nebularine (2) has modest activity against P388 leukemia (60% ILS). While 2'-ara-fluorozebularine (7b) is only marginally active (40% ILS) at high doses against L1210 leukemia, 5-fluoro analogue 6b is more active than zebularine and is ca. 100 times more potent. Although the activity of 6b is about the same as that of 1b against P388 leukemia, greater potency also is realized in this model. Zebularine is a strong inhibitor of cytidine deaminase, but in contrast to tetrahydrouridine, 1b is acid-stable. In an attempt to use this property to advantage in oral administration, 1b and ara-C have been orally coadministered to mice with ip L1210 leukemia. When zebularine is given in divided doses, up to a 2-fold increase in activity is realized, relative to treatment with the same dose of ara-C alone.

Synthesis, antitumor activity, and antiviral activity of 3-substituted 3-deazacytidines and 3-substituted 3-deazauridines

Novel 3-substituted analogues of 4-amino-1-beta-D-ribofuranosyl-2(1H)-pyridinone (3-deazacytidine, 3) and 4-hydroxy-1-beta-D-ribofuranosyl-2(1H)-pyridinone (3-deazauridine, 4) have been synthesized and tested for antitumor and antiviral activity. Thus the 3-chloro (9a), 3-bromo (9b), and 3-nitro (9c) analogues of 3 and the 3-chloro (9d), 3-bromo (9e), and 3-nitro (9f) analogues of 4 were prepared by standard glycosylating procedures. Novel requisite heterocycles 4-amino-3-chloro-2(1H)-pyridinone (7a) and 4-amino-3-bromo-2(1H)-pyridinone (7b) were prepared by halogenating 4-amino-2(1H)-pyridinone (5). Requisite heterocycles 4-amino-3-nitro-2(1H)-pyridinone (7c), 3-chloro-4-hydroxy-2(1H)-pyridinone (7d), 3-bromo-4-hydroxy-2(1H)-pyridinone (7e), and 4-hydroxy-3-nitro-2(1H)-pyridinone (7f) were synthesized by known procedures from 4-hydroxy-2(1H)-pyridinone (6). Structure proof of target nucleosides was provided by independent synthesis, 1H NMR, and UV. Compounds 9a-f were devoid of activity against intraperitoneally implanted L1210 leukemia in mice. Compound 9f displayed significant activity against rhinovirus type 34 grown in WISH cells. 4-Amino-3-fluoro-1-beta-D-ribofuranosyl-2(1H)-pyridinone (1) displayed good activity against intraperitoneally implanted P388 leukemia in mice, but it was devoid of activity against M5076 sarcoma, amelanotic (LOX) melanoma xenograft, and subrenal capsule human mammary carcinoma MX-1 xenograft in mice. Compound 1 also displayed significant activity against rhinovirus type 34.

Comparison of the activity of Arabinosyl-5-azacytosine, Arabinosyl cytosine, and 5-azacytidine against intracerebrally implanted L1210 leukemia

Arabinosyl-5-azacytosine (ara-AC) is a new compound which combines the structural characteristics of arabinosyl cytosine (ara-C) and 5-azacytidine (5-AC). These three compounds, injected intraperitoneally, were evaluated in direct comparison against the intracerebral L1210 leukemia model. 5-AC was active in a non-schedule dependent manner producing increase in life span (ILS) values of 70%. The effects of both ara-C and ara-AC were schedule-dependent with the best activity (ILS ca. 600%; multiple long term survivors) observed using an around-the-clock treatment schedule. In all experiments, ara-AC appeared to be more efficacious than ara-C. In some instances, ara-AC was as active as the positive control compound, BCNU. Excellent activity for ara-AC was also observed against the intracerebral P388 leukemia system.

Comparison of the properties of metabolites of CCNU

Properties of the six isomeric N-(2-chloroethyl- N′-(hydroxycyclohexyl- N-nitrosoureas, which have been identified by other investigators as metabolites of N-(2-chloroethyl- N′-cyclohexyl- N-nitrosourea (CCNU), have been compared with those of CCNU and 2-[[[(2-chloroethyl)nitrosoamino]-carbonyl]amino]-2-deoxy- D-glucose (chlorozotocin). There are significant differences in the physicochemical, chemical, and biological properties of these metabolites, and the properties of some of them are significantly different from those of CCNU and chlorozotocin. The position of the hydroxy group and the steric configuration of the compound markedly affect the alkylating and carbamoylating activities of the compounds. The metabolites having the higher alkylating activities and the lower carbamoylating activities produce lethal toxicity to mice at lower molar doses but have somewhat better therapeutic indexes. The data are consistent with the hypothesis that the biological effects observed following the administration of CCNU are due to a large extent to the major metabolites with lesser effects contributed by the minor metabolites. Some of the metabolites have slightly better therapeutic indexes against murine leukemia L1210 than CCNU and chlorozotocin, and they are more soluble in water than CCNU but are active against both intraperitoneally implanted and intracerebrally implanted L1210 leukemia. There might be some therapeutic advantage to administering one of the minor metabolites instead of CCNU or chlorozotocin to cancer-bearing animals.