Liposoluble platinum(II) complexes with antitumor activity

Seventeen liposoluble bis(carboxylato)-cyclohexane-1,2-diammineplatinum(II) and bis(carboxylato)-cis-diammineplatinum(II) complexes were synthesized and tested for antitumor activity against leukemia L1210 cells in mice. The former complexes had excellent antitumor activity without any toxicity to the host at the therapeutic dose when used with lipiodol as a carrier solvent. The latter complexes had neither antitumor activity nor toxicity in vivo. The former complexes were gradually released from lipiodol to saline in vitro; the latter were not. The activity depended on the chain length of the carboxylato residue and also on the molecular shape of the ligand part of the complexes.     

A case report of pulmonary adenocarcinoma responding to (glycolato-0,0') diammineplatinum (II), a new platinum complex

The first patient to respond to [(glycolato-0,0') diammineplatinum (II)] (254-S) in a clinical phase I study is reported. The patient was a 52-year-old man complaining of nausea and weight loss. A chest X-ray demonstrated a diffuse infiltrating shadow in the right lung. A transbronchoscopic brushing of the right upper lobe and a biopsy specimen from the right supraclavicular lymph node revealed adenocarcinoma of the lung. He was diagnosed as having primary lung cancer with distant lymph node metastasis. 254-S was administered by intravenous drip infusion to a dose of 100 mg/m2. Two weeks after the second 254-S treatment, a chest X-ray demonstrated a more than 50% reduction in the pulmonary shadow and met the WHO criteria for a partial response. Thrombocytopenia, leukocytopenia and moderate nausea were observed as adverse effects of 254-S but renal toxicity was not found. Pharmacokinetics of free platinum in this patient demonstrated biphasic decay with a peak plasma concentration of 8.09 micrograms/ml. A disease-oriented phase II study of 254-S against non-small cell lung cancer should be performed to establish the efficacy of this new platinum complex.     

In vivo potentiation of cis-diamminedichloroplatinum (II) antitumor activity by pretreatment with sparsomycin

The influence of protein synthesis inhibition by sparsomycin (Sm) on in vivo cisplatin activity has been studied on BALBc X DBA2: F1 mice bearing L1210 leukemia i.p. Sm alone at the dose range from 0.5 to 3.0 mg/kg did not significantly improve animal survival. Sm potentiated cisplatin activity only when given 3 or 6 h prior to cisplatin (P less than 0.001). Sm 0.5-1.5 mg/kg 3 h prior to cisplatin resulted in a significant prolongation of animal survival (P less than 0.001) and 66% cures in each group versus 0% due to cisplatin alone. Sm pretreatment decreased weight loss due to cisplatin suggesting that it probably is able to decrease cisplatin toxicity.     

Effect of treatment schedule of an antitumor platinum complex, DWA2114R, on the antitumor activity]

Effects of treatment schedule of (-)-(R)-2-aminomethylpyrrolidine (1,1-cyclobutanedicarboxylato) platinum (II) monohydrate, DWA2114R, on the antitumor activity against murine colon adenocarcinoma (Colon 26) and Lewis lung carcinoma (3LL) were examined. Colon 26 or 3LL tumors were transplanted s.c. into the flank and subsequently DW A2114R was given i.v. by single or multiple injections. The tumor weight was determined on days 14 or 25 and the antitumor effect was evaluated by GIR%. Although the total dose of DWA2114R was identical in both schedules, single injection was superior to multiple. Effect of treatment schedule of cis-dichlorodiammine-platinum (II), CDDP, and cis-diammine (1, 1-cyclobutanedicarboxylato) platinum (II), CBDCA, on the antitumor activities were the same as in case of DWA 2114R, i.e., single injection was superior to multiple.     

Synthesis and antitumor activity of a platinum (II)-doxorubicin complex

Summary A mixed platinum (II) complex with tert-butylamine and doxorubicin (cooordinated via the aminogroup) has been synthesized and tested for antitumor activity. The results indicate that the complex was active against doxorubibin-resistant P388 and cisplatin-resistant L1210 leukemias, while maintaining antitumor activity against sensitive parent lines.     

Influence of methylprednisolone on antitumor effect of cis-diamminedichloroplatinum (II)

To elucidate the influence of methylprednisolone (MPL) on the antitumor effect of cis-diamminedichloroplatinum (II) (CDDP), experimental chemotherapy of CDDP with or without MPL was performed. A human breast carcinoma, MX-1 serially transplanted into nude mice was treated with CDDP in doses of 1.5 and 3.0 mg/kg in schedule of q4d X 3 ip. KKN-1, a syngeneic fibrosarcoma of BALB/c transplanted into BALB/c +/+ or BALB/c nu/nu mice, was treated with CDDP in doses of 3 or 6 mg/kg in schedule of qd X 1 ip. In the combination of MPL, 20 mg of MPL per kg was administered ip three hours before CDDP treatment. Although some decrease of antitumor effect of CDDP was observed by combination with MPL, no statistically significant difference was noted between group given CDDP alone and those given CDDP plus MPL. It was concluded that the use of MPL is reasonable to prevent the severe emesis caused by CDDP when this adverse effect is resistant to other antiemetic agents.     

Ascorbato(1,2-diaminocyclohexane):platinum(II) complexes, a new series of water-soluble antitumor drugs

Dichloro-1,2-diaminocyclohexane (DACH):platinum(II), the prototype DACH:platinum complex, had good antitumor activity, was not cross-resistant with cis-dichlorodiammineplatinum(II) (DDP), but was, unfortunately, virtually insoluble in water and was, therefore, not evaluated clinically. This paper summarizes some of the chemical and biological attributes of a series of cis-bisascorbato-DACH:platinum(II) complexes (DAP). Although the primary emphasis has been placed on the DAP complex consisting of the isomeric mixture DACH, a series of complexes using the isomers of either DACH or ascorbic acid have also been synthesized. The synthetic procedure entailed reacting the water-soluble sulfato-DACH:platinum(II) with barium ascorbate, and the water-soluble product DAP was removed from the BaSO4 precipitate by filtration. Based upon elemental analysis, all the complexes had stoichiometric composition of one DACH:one platinum and two ascorbate monoanions. High-pressure liquid chromatography of cis-bisascorbato (mixed-isomer DACH):platinum revealed a series of platinum-containing, ultraviolet-absorbing peaks. All the DAP complexes had significant in vitro cytotoxicity against L1210 leukemia cells (L1210/0) with 50%-inhibitory dose values ranging from 2 to 5 micrograms/ml. None of the complexes was cross-resistant with DDP when tested in vitro against L1210 cells 50-fold resistant to DDP (L1210/DDP). The cis-bisascorbato (mixed-isomer DACH):platinum (DAP-1) was administered i.p. to C57BL X DBA/2 F1 mice inoculated i.p. with 10(6) L1210/0 cells. When administered on Days 1, 5, and 9, the DAP-1 complex consistently produced treated:control values in excess of 200% with several long-term survivors (alive 60 days after tumor inoculation). Further, the DAP-1 complex was totally non-cross-resistant with DDP when tested in vivo against a DDP-resistant L1210 line. Toxicological investigations revealed that DAP-1 was relatively nonnephrotoxic but did cause the expected bone marrow and gastrointestinal toxicity. In summary, the DAP complexes are highly water-soluble, nonnephrotoxic platinum complexes with sufficient antitumor activity to warrant further pharmacological, biochemical, and chemical investigations.     

The gingival platinum line: a new finding following cis-dichlorodiammine platinum (II) treatment.

Cis-dichlorodiammine platinum (II) (DDP) is the salt of a heavy metal with a wide spectrum of antineoplastic activity. Its toxicity is multisystem and similar to that of other heavy metals, including lead and thallium. A young man being treated with primary adjuvant Adriamycin and DDP for osteogenic sarcoma is described who developed a gingival line which temporally was related to DDP administration. Although not chemically or histologically analyzed, we believe this to be a new finding related to DDP which corresponds to the lead line of plumbism and other heavy metal intoxication.     

Effect of a new peptidyl-hypoxanthine derivative on natural killer cells and antitumor activity.

A new immunomodifier, [omega-(hypoxanthin-9-yl) pentoxy-carbonyl-leucyl-methionine] (RM06), was synthesized and its effect was evaluated on the activity of Natural Killer (NK) cells. Results indicate that RM06 is able to boost the NK activity of normal mice as well as to augment the regeneration of NK activity of lethally irradiated mice transplanted with syngeneic bone marrow (BM). This later effect also correlated with a significant increase in anti-tumor activity as evaluated by the resistance to metastasis in mice injected with syngeneic melanoma cells. These data indicate that RM06 is able to modulate the NK cell activity as well as the antitumor resistance.     

Antitumor activity of a new platinum complex, 2-aminomethyl-pyrrolidine (1, 1-cyclobutanedicarboxylato) platinum (II)

One hundred cis-diamminedichloroplatinum (II) (CDDP) analogs have been evaluated for antitumor activity in male CDF1 mice subcutaneously (s.c.) implanted with tumor fragments of Colon 26 carcinoma. Among the complexes tested, 2-aminomethyl-pyrrolidine (1, 1-cyclobutanedicarboxylato) platinum (II) (DWA 2114) had the best antitumor effect. The mice intraperitoneally (i.p.) injected with DWA 2114 at a dose of 40 mg/kg/day on days 4, 6 and 8 after inoculation showed a 97% growth inhibitory ratio (GIR) on day 14 compared to the non-treated control mice. We evaluated the inhibitory effects of DWA 2114 on other tumors, such as Colon 38 carcinoma, Ca 755 mammary adenocarcinoma and L1210 leukemia, and found that it also had antitumor effects on various kinds of tumors. The nephrotoxicity-inducing activity of DWA 2114 and CDDP was evaluated in normal BDF1 mice, as indicated by changes in blood urea nitrogen (BUN) at almost the maximum tolerated dose (MTD) (DWA 2114: 100 mg/kg, CDDP: 12 mg/kg). DWA 2114 had no effect on BUN levels, while CDDP elevated BUN levels. These results indicate that DWA 2114 represents a second generation platinum antitumor complex.     

CI-973, a new platinum derivative with potential antileukemic activity.

We examined the effects of CI-973 (supplied by Parke-Davis) on several human leukemia cell lines and a Chinese hamster ovary (CHO) line and their drug-resistant counterparts. The cell lines used were HL-60, HL-60/mAMSA, HL-60/DOX, KBM3, KBM3/mAMSA 6, KBM3/mAMSA 6(85), CHO, and CHO/AC-7. DOX, mAMSA, and AC-7 indicate resistance to doxorubicin, amsacrine, or 1-beta-D-arabinofuranosylcytosine, respectively. Cells were incubated with CI-973, and the effect was evaluated by two methods: growth inhibition assay and inhibition of colony formation. All cell lines examined were inhibited by CI-973; two of three amsacrine-resistant lines and the one cytarabine-resistant line demonstrated collateral sensitivity. At equivalent dosages, a 4-day exposure provided much greater cell kill than a 1-h exposure. Clonogenic assay showed exponential killing over 3 log units. Maximum CI-973 levels required to kill 50% of cells were 10-fold lower than the peak plasma levels achieved in a phase I solid tumor study. A continuous infusion phase I study in acute leukemia has been initiated.     

Pharmacokinetics of cis-diammine (glycolato) platinum (254-S), a new platinum antitumor agent, following an intravenous and intraperitoneal infusion bioactive platinum concentration profile

The pharmacokinetics of cis-diammine (glycolato) platinum (254-S) was investigated in cancer patients following intravenous and intraperitoneal infusion. The serum concentrations of total and unbound 254-S were determined by bioassay and chemical assay as platinum. Platinum detected by bioassay was thought to be active and unchanged 254-S. Almost all of platinum in plasma were found to be active and unbound to protein because of no differences in the concentrations determined by bioassay and chemical assay and in plasma and plasma filtrate. In abdominal ascites, platinum concentrations determined by bioassay corresponded with those determined by chemical assay, suggesting that 254-S was stable in abdominal ascites. The Cmax and AUC of active 254-S in plasma determined by bioassay following an intraperitoneal infusion were about 60% and 60-80% of those following an intravenous infusion, respectively. These results showed that 254-S was well absorbed into systemic circulation from abdominal ascites as an active form. It is concluded that antitumor effect may be obtained following an intraperitoneal infusion of 254-S as well as for the reduction of abdominal ascites.     

Effect of selenium in combination with cis-diamminedichloroplatinum(II) in the treatment of murine fibrosarcoma

cis-Diamminedichloroplatinum(II) (cis-DDP) is a well-known anticancer agent the use of which is limited by its toxicity. Since it has been demonstrated that selenium is able to combine with metals like cadmium and mercury and to reduce their toxicity, we decided to investigate whether it could reduce the toxicity of platinum. We treated fibrosarcoma-bearing mice with a combination of cis-DDP and selenium. The dose of 2 or 4 micrograms selenium/g animal weight had no effect on tumor growth. The i.p. injection of 16 micrograms cis-DDP/g led to early death of animals. The i.p. treatment of tumor-bearing animals with 2 or 4 micrograms of selenium reduced the early mortality induced by cis-DDP at a dose of 16 micrograms/g. Therefore, the addition of selenium allowed the administration of high doses of cis-DDP, which resulted in an improved antitumor effect. Clonogenic assays following drug exposure showed that selenium had no direct effect on tumor cells and did not modify the antitumor activity of cis-DDP. Electron microscopy showed reduced changes in renal cells when selenium was added to the cis-DDP treatment. Microanalysis showed no accumulation of either selenium or platinum within renal cells. These results suggest that the addition of selenium decreases the nephrotoxicity of cis-DDP.     

In vivo characterization of combination antitumor chemotherapy with calcium channel blockers and cis-diamminedichloroplatinum(II)

We have examined nifedipine, a dihydropyridine class calcium channel blocker, for ability to overcome cis-diamminedichloroplatinum(II) (cisplatin) resistance in a murine tumor line variant, B16a-Pt, which we developed for resistance to cisplatin. Nifedipine significantly enhanced the antitumor actions of cisplatin against primary subcutaneous B16a-Pt tumors and their spontaneous pulmonary metastases. We have characterized, in vivo, the pharmacokinetics and dose-response interactions between nifedipine and cisplatin. We now report our studies designed to compare, in vivo, the efficacy of nifedipine and other calcium active compounds including: (a) structurally similar calcium channel blockers (nimodipine, nicardipine) from the dihydropyridine class, (b) structurally different calcium channel blockers from the benzothiazepine (diltiazem) and the phenylalkylamine (verapamil) classes, and (c) calmodulin antagonists (trifluoperazine and calmidazolium) for ability to enhance the antitumor action of cisplatin. Nifedipine was included as the standard or reference compound. In these studies verapamil and diltiazem failed to enhance the antitumor actions of cisplatin as did both calmodulin antagonists. Our findings suggest that nifedipine has a greater degree of specificity for B16a-Pt cells than structurally different calcium channel blockers from other chemical classes (i.e., diltiazem and verapamil), or the two calmodulin antagonists (i.e., trifluoperazine and calmidazolium). We concluded that nifedipine interacts with specific target site(s) which are not accessible by verapamil, by diltiazem, or by the calmodulin antagonists. Surprisingly, the two dihydropyridine class calcium channel blockers, nimodipine and nicardipine, also failed to enhance cisplatin's antitumor actions despite the fact that their specificity and kinetics for binding to the dihydropyridine receptor component of the calcium channel favors them (nimodipine and nicardipine) over nifedipine. Therefore, we postulate that the synergism between cisplatin and nifedipine is independent of the latter's effect on the voltage sensitive, slow inward calcium channel. We suggest that cisplatin cytotoxicity is enhanced by nifedipine's interaction with an as yet unidentified specific "target site," as opposed to nonspecific interactions with the tumor cell plasma membrane or specific interactions with calmodulin or the P-glycoprotein (which is responsible for pleiotropic resistance).     

Effect of hyperthermia on cis-diamminedichloroplatinum(II) (rhodamine 123)2[tetrachloroplatinum(II)] in a human squamous cell carcinoma line and a cis-diamminedichloroplatinum(II)-resistant subline

The effect of concomitant hyperthermia on the cytotoxicities of cis-diamminedichloroplatinum(II) (CDDP), a newly synthesized drug, Pt(Rh-123)2, and its chemical components, K2PtCl4 and rhodamine 123, was examined in vitro in a squamous cell tumor line of human origin (SCC-25) and in a CDDP-resistant subline (SCC-25/CP). No difference in the cytotoxicity of hyperthermia alone was observed between these cell lines. The dose-dependent cytotoxicities of 1-h exposures to CDDP and Pt(Rh-123)2 were markedly increased at 42 degrees C and 43 degrees C in comparison to 37 degrees C, and this effect was of the same magnitude in both cell lines (enhancements of approximately 1.5 logs at 42 degrees C and 2.5 logs at 43 degrees C for CDDP and 1.5 logs at 42 degrees C and greater than 3 logs at 43 degrees C for Pt(Rh-123)2). The use of hyperthermia with CDDP, however, did not lower survivals in the SCC-25/CP cells even to the levels seen in the parent line at 37 degrees C. The cytotoxicities of K2PtCl4 and rhodamine 123 were essentially the same in the CDDP-sensitive and -resistant cells at all temperatures tested. The magnitude of the temperature effect was significantly greater for Pt(Rh-123)2 than for its chemical components. No significant effect on CDDP or Pt(Rh-123)2 accumulation was observed at 42, 43, 44 or 45 degrees C in either cell line. DNA lesions, measured by alkaline elution, were significantly enhanced for CDDP in the SCC-25 cells at 42 degrees C. These results suggest that treatment with hyperthermia and either CDDP or Pt(Rh-123)2 should result in supraadditive anti-tumor effects, although the efficacy of CDDP plus hyperthermia will be significantly less once resistance to CDDP has developed. Since resistance to CDDP does not imply cross-resistance to Pt(Rh-123)2, and since the effect of hyperthermia is somewhat greater for Pt(Rh-123)2 than for CDDP at 43 degrees C, Pt(Rh-123)2 may be more selectively toxic to tumor cells when used with local hyperthermia versus normal cells outside the treated area, especially if resistance to CDDP has already developed.     

Antitumor activity of a new platinum complex, (R)-(-)-2-aminomethylpyrrolidine (1, 1-cyclobutanedicarboxylato) platinum (II), against cisdiamminedichloroplatinum (II)-resistant murine leukemia cell line

Antitumor activity of a new platinum complex, (R)-(-)-2-aminomethylpyrrolidine (1, 1-cyclobutanedicarboxylato) platinum (II) (DWA 2114 R) against cisdiamminedichloroplatinum (II) (CDDP)-resistant tumor was examined in in vitro and in vivo experiments. CDDP-resistant line was established from L 1210 mouse leukemia cells by continuous exposure to CDDP in dose-escalation manner. Six clones were isolated from parental resistant line and one of these clones, clone f, which was found to be highly resistant (30-40 fold) to CDDP, was used in the following experiments. Clone f showed 4-7 fold cross-resistance to DWA 2114 R and 11-19 fold to cisdiammine-1, 1-cyclobutanedicarboxylatoplatinum (II) (CBDCA) in in vitro growth inhibition assay. DWA 2114 R showed the most effective antitumor activity against mice transplanted with the resistant cells in the increase of life span (ILS%). About 100% of ILS and cured mice were observed in the treatment with DWA 2114 R. On the other hand, CDDP or CBDCA showed a little increase in the survival time (less than 40% of ILS) and all mice died. These results suggest that DWA 2114 R seemed to be more effective against CDDP-resistant tumors clinically than CDDP and CBDCA.     

In vitro antitumor mechanism of a new platinum complex, (-)-(R)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato+ ++) platinum(II)

The antitumor mechanism of (-)-(R)-2- aminomethylpyrrolidine (1.1-cyclobutanedicarboxylato)platinum(II) (DWA2114R) was examined using cultured murine L1210 leukemia cells by estimating its effects on parameters such as proliferation, macromolecular synthesis, morphology and cell cycle progression. Each parameter was estimated in cells concomitantly exposed to the drug for 24-48 hr. More than 0.1 microM of DWA2114R markedly inhibited cell proliferation as well as DNA synthesis, and it decreased in mitotic index in a concentration-dependent manner. One microM of DWA2114R decreased DNA synthesis by 80% in the cells treated for 24 hr, while the inhibition of RNA synthesis was less than 40%. A significant inhibition of protein synthesis was caused only by treatment with a high concentration (100 microM) of the drug. Under complete cytostatic conditions (10 microM of DWA2114R), cell volume markedly increased and about 40% of the total cells were polynucleate. In addition, flow cytometrical analysis revealed that most of these cells were accumulated in the G2/M phase of the cell cycle, and a new peak located in the G2/M phase of tetraploid cells emerged. On the other hand, the cells treated with 100 microM of the drug did not increase in volume and their progress in the cell cycle was almost completely blocked.     

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.     

New antitumor platinum(II) complexes with both lipophilicity and water miscibility

Water-miscible platinum(II) complexes with 1,2-diaminocyclohexane as the carrier ligand and bile acids as the leaving ligands were synthesized and tested for antitumor activity against intraperitoneally implanted leukemia L1210 cells in mice. These complexes were water-miscible after appropriate sonication due to the presence of hydrophilic hydroxyl groups in the molecule, even though the complexes were essentially lipophilic. The complexes had high antitumor activity, but their optimal dose levels differed, and the administration route and form affected the antitumor activity. More lipophilic complexes showed higher activity when administered with Lipiodol than in water suspension, while the hydrophilic complexes showed significant activity when administered in water suspension. Intravenous administration of DACHP(cheno)2 in water suspension resulted in potent antitumor activity, while other complexes showed moderate activity via this route.