Antitumor benzothiazoles. 3. Synthesis of 2-(4-aminophenyl)benzothiazoles and evaluation of their activities against breast cancer cell lines in vitro and in vivo.

A new series of 2-(4-aminophenyl)benzothiazoles substituted in the phenyl ring and benzothiazole moiety has been synthesized by simple, high-yielding routes. The parent molecule 5a shows potent inhibitory activity in vitro in the nanomolar range against a panel of human breast cancer cell lines, but is inactive (IC50 > 30 microM) against other cell types: activity against the sensitive breast lines MCF-7 and MDA 468 is characterized by a biphasic dose-response relationship. Structure-activity relationships derived using these cell types has revealed that activity follows the heterocyclic sequence benzothiazole > benzoxazole >> benzimidazole and that 2-(4-aminophenyl)benzothiazoles bearing a 3'-methyl- 9a, 3'-bromo- 9c, 3'-iodo- 9f, and 3'-chloro-substituent 9i are especially potent and their activity extends to ovarian, lung, and renal cell lines. Four compounds have been evaluated in vivo against human mammary carcinoma models in nude mice. Compound 9a showed the most potent growth inhibition against the ER+ (MCF-7 and BO) and ER- (MT-1 and MT-3) tumors. Our efforts to identify a pharmacological mechanism of action for these intriguing compounds have not, as yet, been successful.

Structural studies on bioactive compounds. 23. Synthesis of polyhydroxylated 2-phenylbenzothiazoles and a comparison of their cytotoxicities and pharmacological properties with genistein and quercetin.

A series of polyhydroxylated 2-phenylbenzothiazoles 3 has been prepared by demethylation of the precursor methoxylated 2-phenylbenzothiazoles 9. The key step in the construction of the benzothiazole nucleus involves a Jacobson cyclization of methoxylated thiobenzanilides 8. The target compounds inhibit WiDr human colon tumor cells and MCF-7 human mammary tumor cells in vitro with IC50 values in the low micromolar range, but the activity against MCF-7 cells is not related to estrogen receptor-binding affinity. None of the compounds showed selective cytotoxicity against Abelson virus-transformed ANN-1 cells encoded with the pp120gag-abl tyrosine kinase compared with the parental 3T3 line. Compounds were only marginally inhibitory to the EGF receptor-associated protein tyrosine kinase from a membrane preparation of A431 cells. The most active compound was 4,6-dihydroxy-2-(4-hydroxyphenyl)benzothiazole (3b) which has the same overall hydroxyl substitution pattern as genistein (1a). The compounds were weakly cytotoxic for an EGF receptor, overexpressing cell line HN5, but when tested for differential toxicity against the EGF receptor tyrosine kinase or the PDGF receptor tyrosine kinase in a standard mitogenesis assay utilizing human fibroblasts, no discrimination was observed. In this assay, the compounds inhibited DNA synthesis when added to cells during S phase. This suggests that inhibition could not be interpreted in terms of tyrosine kinase inactivation but more likely as a relatively broad specificity for the ATP-binding domain of other kinases such as thymidine kinase.

In vitro antiproliferative activity of docetaxel (Taxotere), paclitaxel (Taxol) and cisplatin against human tumour and normal bone marrow cells.

The in vitro antiproliferative effect of docetaxel (Taxotere), paclitaxel (Taxol) and cisplatin was assessed in a range of human tumour types, including 25 tumour cell lines and 35 primary cultures. Additionally, 12 human normal bone marrow samples were analyzed. Seven laboratories, all members of the EORTC Preclinical Therapeutic Models Group (PTMG), have performed these tests, using their own individual assay procedures. In all comparisons docetaxel and paclitaxel were much more potent than cisplatin with IC50 values of the taxoids being in the nanomolar range. Docetaxel generally was two- to four-fold more cytotoxic than paclitaxel. The sensitivity profile of the cell lines, which was based on the IC50 values, indicated a certain degree of cross-sensitivity between paclitaxel and docetaxel (linear regression analysis; r = 0.73, p < 0.001). On the other hand, the sensitivity profile of cisplatin was different from the ones seen for docetaxel and paclitaxel, indicating that no cross-sensitivity exists between cisplatin and both taxoids.

Acetyldinaline: a new oral cytostatic drug with impressive differential activity against leukemic cells and normal stem cells--preclinical studies in a relevant rat model for human acute myelocytic leukemia.

Acetyldinaline [CI-994; GOE 5549; PD 123 654; 4-acetylamino-N-(2'-aminophenyl)-benzamide] is the acetylated derivative form of the original compound Dinaline (GOE 1734; PD 104 208). The efficacy and toxicity of Acetyldinaline for remission-induction treatment of leukemia were evaluated and compared with those observed in previous studies of Dinaline in the Brown Norway acute myelocytic leukemia, as a preclinical model for human acute myelocytic leukemia. There were three treatment groups. Leukemic animals received either 1 or 2 courses of 5 daily p.o. administrations of Acetyldinaline with a "full dose" of 23.7 mg/kg once daily (first group), a twice daily "half dose" of 11.85 mg/kg with an interval of 8 h (second group), or a "half dose" of 11.85 mg/kg once daily (third group). The drug-free interval between the 2 courses was 2 or 9 days. With repeated daily p.o. administrations of 23.7 mg/kg either in a single daily dose or a split daily dose of 2 x 11.85 mg/kg for 1 course, at least an 8-log leukemic cell kill was achieved. In contrast, with these treatment schedules, less than a 1-log cell kill of normal pluripotent hemopoietic stem cells (CFU-S) in the femoral bone marrow was found. Split daily dose treatment was more effective resulting in 37.5% cures, while no cures were observed with the single daily treatment for one course. Treatment with single daily dose of 23.7 mg/kg or a split daily dose of 2 x 11.85 mg/kg for 2 courses, with either a 2- or 9-day interval in between, resulted in lethal toxicity in most of rats. This result was comparable with that previously observed after equimolar doses of Dinaline (20 mg/kg). The half-dose once daily treatment with Acetyldinaline (11.85 mg/kg) for 1 or 2 cycles resulted in about a 4.5 or > 8-log leukemic cell kill, respectively. Toxic side effects, i.e., damage to the gastro-intestinal tract and hemorrhages in the lungs, were more pronounced with full dose either in the single or the split daily dose regimen. No significant toxicity was observed at the half-dose treatment once daily. In conclusion, the impressive differential activity against leukemic cells and normal stem cells observed in this relevant rat model for human acute myelocytic leukemia warrants the introduction of this compound in clinical phase I/II studies.

Cytotoxic activity of di-n-butyltin(IV)(X-A-B-Y) compounds related to salicylic acid against human tumour cells.

A series of di-n-butyltin(IV) compounds of the type di-n-butyltin(IV)(X-A-B-Y) with the (X-A-B-Y) being related to salicylic acid was tested in vitro for cytotoxic activity against tumour cells of the human A 204, MCF-7, T24, WiDr and IgR-37 cell lines using the PIT method. In each cell line the di-n-butyltin(IV) compounds displayed similar activity. As compared to cisplatin, the compounds were 4- to 10-fold more effective against A 204, MCF-7 and T24 tumour cells and slightly more effective against WiDr cells. The effectiveness against IgR-37 cells was similar for cisplatin and di-n-butyltin (IV) compounds.

Lipophilic analogues of sparsomycin as strong inhibitors of protein synthesis and tumor growth: a structure-activity relationship study.

Fourteen derivatives of sparsomycin (1) were synthesized. Six of them were prepared following a novel synthetic route starting from the L-amino acid alanine. Some physicochemical properties, viz. lipophilicity and water solubility, of selected derivatives were measured. The biological activity was tested in vitro in cell-free protein synthesis inhibition assays, in bacterial and tumor cell growth inhibition assays, and in the L1210 leukemia in vivo model in mice. Also for selected drugs the acute toxicity in mice was determined. Ribosomes from both an eukaryotic and a prokaryotic organism were used in the protein synthesis inhibition systems. A linear correlation between the lipophilicity parameters measured was observed. Water solubility and drug toxicity in mice were found to be linearly correlated with lipophilicity. All the derivatives studied are more lipophilic than 1. The deshydroxysparsomycin analogues (30-33) showed an interesting phenomenon: increase in hydrophobicity was accompanied by a considerable increase in water solubility. We found that an increase in hydrophobicity of the drug as a result of replacing the SMe group of 1 with larger alkylthio groups causes an increase in the biological activity of the drug. However, not only the hydrophobicity but also shape and size of the substituent are important; in the homologous series 1-9-10-11-12, 21-22-23-24, and 30-31-32-33, highest protein synthesis inhibitory and in vitro cytostatic activity is found with compounds 11, 23, and 32, respectively, and in comparison with the highly active n-butyl compound 10, the isomeric tert-butyl compound 13 is rather inactive. Polar substituents replacing the SMe group, i.e. Cl in 17 and 35, also render the molecule inactive. Substituting the bivalent sulfur atom for a methylene group decreases the drug's activity. This effect can be compensated for by increasing the length of the alkylsulfinyl side chain. The agreement between the results derived from cell-free and "in vivo" tests is good. The assays using ribosomes of bacterial and eukaryotic organisms give similar results although the latter seem to be more sensitive to changes in hydrophobicity of the drug. Our results confirm the presence of a hydrophobic region at the peptidyl transferase center of the ribosome; the interaction of sparsomycin with this region is more pronounced in the eukaryotic particles. The sparsomycin analogues 11, 23, and 30 show the highest antitumor activity against L1210 leukemia in mice, their median T/C values are 386, 330, and 216%, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Synthesis, mechanism of action, and biological evaluation of mitosenes.

Mitosenes of both the pyrrolo- and pyrido[1,2-a]indole type have been prepared via modification of these heterotricyclic compounds. Several mitosenes have been studied for their reactions with nucleophiles under reductive conditions. The results of these experiments show that the biological activity of mitosenes is based on the mechanism of bioreductive activation. When both leaving groups at C-1 and C-10 in the mitosene are the same, the nucleophile preferably adds to C-10 under reductive conditions. All mitosenes were studied for their biological activities in vitro against L1210, WiDr, and A204. On the basis of these results a selection of three mitosenes was made for a more detailed biological evaluation. Several tumor model systems were used, viz. P388, human tumor xenografts, MAC 13, and MAC 16. The results of these studies show that mitosenes have a more limited range of activities than mitomycin C. Surprisingly, the in vivo activities of mitosene diol 8b and mitosene diacetate 10b against the gastric human tumor xenograft GXF 97 were very high and comparable with that of mitomycin C.

In vivo antitumor activity of sparsomycin and its analogues in eight murine tumor models.

Sparsomycin (Sm) is a known inhibitor of ribosomal protein synthesis with an attractive anticancer potential. Recently, several analogues of Sm which are more active than the parent drug were selected for further study on the basis of in vitro investigations. Six analogues as well as the parent drug were tested for their antitumor activity in eight in vivo murine tumor models: P388 and L1210 leukemias, RC renal cell carcinoma, B16 melanoma, C38 colon carcinoma, LL Lewis lung carcinoma, C22LR osteosarcoma and M5076 sarcoma. Sm itself appeared to have only borderline activity on L1210 leukemia. The analogues that were most active in vitro showed also the highest in vivo activity. The most sensitive tumors were RC, L1210 and P388. Minimal activity was found on B16 and no activity on C22LR, M5076, C38 and LL. The most active compounds are deshydroxy-Sm, ethyl-deshydroxy-Sm and n-pentyl-Sm. There was a considerable loss of activity when L1210 leukemia was implanted sc while the drugs were administered iv. Only one drug, ethyl-deshydroxy-Sm appeared to be active in this assay. No single most effective compound could be found in this study. The overall activity of Sm and its analogues is moderate. The three analogues which show high activity in three ascitic tumors will be further investigated using human tumor xenograft models.

Pharmacokinetics and toxicity of mitomycin C in rodents, given alone, in combination, or after induction of microsomal drug metabolism.

The pharmacokinetics of mitomycin (MMC) was studied in Wistar rats. Up to five half-lives, the plasma concentration-time curve was biphasic. The AUC changed linearly with increasing doses between 0.5 and 7.5 mg/kg, which corresponds to 0.2 and 3 times the LD50 value in rats. Most of the drug was metabolized, and only 1%-2% and 10%-15% of the dose was eliminated unchanged by biliary and urinary excretion, respectively. The AUC of MMC at the LD50 is slightly less than that reported for the human MTD. Inoculation of MMC together with 5-fluorouracil and doxorubicin did not change the terminal half-life of MMC but decreased the total body clearance and the volume of distribution. The lack of significant influence of phenobarbital and 3-methylcholanthrene pretreatment on the terminal elimination half-life suggests that microsomal drug-metabolizing enzymes inducible by these compounds do not play a decisive role in the in vivo biotransformation of MMC.

Novel bioreductive mitosene and mitosane analogues of mitomycin C.

Mitosenes of both the pyrrolo- and pyrido[1,2-a]indole type have been prepared via a modified Madelung reaction of benzeneacetonitriles ortho-substituted with gamma- and delta-lactam moieties, respectively, followed by modification of the resulting heterotricyclic compounds. Some in vitro anti-tumour activity data of these novel compounds are rearrangement of 2-(1-pyrrolidinyl)-3-vinylquinone derivatives to 5,8-dioxo-1H-pyrrolo[1,2-a]indoles.

Structure-activity relationships of sparsomycin: modification at the hydroxyl group.

Ten analogues of the antibiotic sparsomycin were prepared and evaluated in several in vitro tests. Nine of them carry a modification at the hydroxymethylene group of the molecule, two have a disulfide bond instead of the S(O)-CH2-S moiety at the sulfur-containing side chain of the molecule. While the presence of the S-S group decreases the activity of the analogues in all the tests performed, the modification at the OH group has no deleterious effects on the activity when a polyphenylalanine synthesis assay is used in an Escherichia coli extract. The same modifications, however, diminish drastically the activity of the analogues when tested in a similar Saccharomyces cerevisiae extract. A polymerization system in the archaebacterium Halobacterium halobium extract behaves like the eukaryotic preparations. A discrepancy is also found between the results of the polymerization tests and those of the 'puromycin reaction' which is also less sensitive to the modified sparsomycin analogues. The results of cell growth inhibition tests in bacteria as well as in eukaryotic organisms agree only partially with the in vitro data.

Preclinical toxicology of platinum analogues in dogs.

A toxicology study of cis-diamminedichloroplatinum (II) (CDDP), aqua(1,1-bis-(aminomethyl)cyclohexane)sulfatoplatinum(II) (TNO-6), diammine(1,1-cyclobutanedicarboxylato)platinum(II) (CBDCA), cis-dichloro-trans-dihydroxo-cis-bis(isopropylamine)platinum-(IV) (CHIP) and ethylenediaminemalonatoplatinum(II) (JM-40) was carried out in dogs. The main purpose of the study was to compare the results with those obtained earlier in mice and rats and with the toxicology data in humans. Each platinum compound was tested in three dogs. Each dog received three intravenous bolus injections at intervals of 3 weeks. The compounds were administered in dosages of 1.2, 1.0, 12, 10 (or 6) and 10 mg/kg, respectively. Toxic death occurred for two dogs (both on day 54) from haematotoxicity (10 mg/kg CHIP) and renal toxicity (TNO-6), respectively. Serum urea nitrogen and creatinine concentrations were variable after TNO-6 and remained within normal values after treatment with the other compounds. Severe proteinuria was observed in all three dogs treated with TNO-6. Values returned to normal within 16 days. JM-40 did not cause significant proteinuria. CDDP, CBDCA and CHIP caused short-lasting and slight proteinuria. CHIP caused a severe reduction in the number of leukocytes and platelets, while the other drugs caused acceptable reductions. Except after the high dose CHIP regimen, haematotoxicity was of a transient nature. Vomiting in order of severity occurred after TNO-6, CHIP, CDDP and JM-40, while CBDCA did not cause any vomiting. The dogs were sacrificed 6 weeks after the last drug dose. Organs were fixed for histopathology to complete and support clinical-toxicological parameters. On the basis of the results from the single-dose study in dogs and those obtained earlier in mice and rats it can be concluded that the gain from the use of the dog as a prognosticator for organ toxicity in man was disappointing and limited to the prediction of vomiting.

Three tumor sensitivity tests evaluated with mouse tumors.

The predictive value of three types of tumor sensitivity tests was evaluated using mouse tumors. Sensitivities of osteosarcoma C22LR, Lewis lung and M2661 carcinoma were determined for the following drugs: DNA interacting or alkylating agent (doxorubicin, cisplatin, 1,3-bis(2-chloroethyl)-1-nitrosourea, melphalan), antimetabolite (5-fluorouracil, methotrexate) and microtubule inhibitor (vinblastine, vincristine). Volume measurements of the subcutaneously growing tumors after treatment with the same drugs were considered to be the traditional reference system with which the results of the in vitro clonogenic assay, the labeled precursor incorporation assay and the subrenal capsule assay were compared. Results obtained with the in vitro clonogenic assay were highly reproducible. With the 1-h drug exposure technique the predictive accuracy was 71%. This result is in the same range as those found by others for human tumors. Predictive accuracy after continuous drug exposure was only 25%. Vinblastine, vincristine and cisplatin caused no inhibition of labeled precursor incorporation. However, the assay is too unreliable to use, due to the extreme variability when used with the other drugs. From 31 consecutively performed duplicate tests in the subrenal capsule assay, nine showed opposite results. This degree of disagreement between duplicate test results was considered too high to make reliable predictions of tumor sensitivity with this assay.

Structure-activity relationships of sparsomycin and its analogues. Inhibition of peptide bond formation in cell-free systems and of L1210 and bacterial cell growth.

The biological activity of 14 analogues of sparsomycin (1) was studied in cell-free systems of Escherichia coli, Saccharomyces cerevisiae, and Sulfolobus solfataricus by measuring the inhibition of protein synthesis. The inhibition of L1210 colony formation in soft agar and bacterial cell growth in solid as well as in liquid medium was also examined. Each analogue possesses not more than two structural modifications of the sparsomycin molecule. This enabled us to determine unambiguously several structural and stereochemical features that are required for an optimal biological activity in these assays. Sparsomycin, having the SCRS chirality, is the most potent of the four possible stereoisomers. The results obtained with compounds 5-7 indicate that the presence of an oxygen atom on the S (alpha) atom is essential. Substitution of the bivalent sulfur atom by a CH2 group (10) or of the SCH3 moiety by a Cl atom (12) affects the activity of the molecule partially. Compound 12 is surprisingly active against intact cells. Substitution of the C(6)-CH3 group by a H(14) reduces the activity of the molecule. Isomerization of the trans double bond into the cis double bond yields cis-sparsomycin (15), which is inactive. The hydrophobic derivatives 8, 9, and 11 are considerably more active than sparsomycin; thus the ribosomal binding site for sparsomycin may have a hydrophobic character.

Reduction of cis-dichlorodiammineplatinum(II) caused nephrotoxicity by indazolone carboxylic acid.

To reduce the nephrotoxicity of cis-dichlorodiammineplatinum (cis-DDP) we have used tetrahydroindazolonedicarboxylic acid (HIDA) in doses of 200, 100 or 50 mg/kg 4, 2 and 1 h before or 1, 2 and 4 h after cis-DDP treatment (10 mg/kg). At any dose, given 2 or 1 h before or 1 h after cis-DDP, HIDA reduced the kidney damage as judged by the blood urea nitrogen (BUN) levels in blood. No protective effect was seen when HIDA was given 4 h before cis-DDP injection. Studies in vitro on L1210 cells have revealed that HIDA does not directly interact with cis-DDP.

The PIT method: an automated in vitro technique for drug toxicity testing.

An automated in vitro technique for drug toxicity testing is described. Human tumor cells were cultured for 2 days in 96-well microtiter plates before the addition of serial dilutions of drugs. At day 5 the cultures were terminated by the addition of a solution containing propidium iodide, ink and triton X-100 (PIT). Triton X-100 lysed all cells, which were subsequently stained by the DNA specific fluorescing propidium iodide. The ink effectively quenched all background fluorescence. The plates were read on a computer controlled automated microscope with a photomultiplier. The results showed a linear relationship between cell number and fluorescence intensity. Reproducible dose-response curves were obtained for 6 drugs tested. A computer program calculated ID50 values, making use of adequate growth and no-growth controls.

Toxicology and pharmacokinetics of (1,1-bis(aminomethyl)cyclohexane)oxalatoplatinum(II) (TNO-38).

Preclinical studies on toxicology and pharmacokinetics were performed for (1,1-bis(aminomethyl)cyclohexane)oxalatoplatinum(II) (TNO-38) in rats and a dog after LD10 and LD50 assessment in mice. In drug-treated rats, ura and creatinine concentrations were 1.4-1.9 times those in control rats. Histopathology showed necrosis of tubular epithelium of the kidneys, which was comparable to damage observed after treatment with cisplatin (CDDP), and extensive necrosis of crypt epithelium, especially in the ileum. Similar to CDDP, TNO-38 was emetic in the dog. Non-specific subacute inflammatory changes were observed in the ileum. Renal damage was much less pronounced. Half-lives of distribution and elimination were 6.2 min and 5.2 days, respectively. The cumulative excretion of Pt in urine over 1 and 7 days after drug treatment was 38.3 and 49.3% of the dose, respectively. Twelve weeks after drug administration, Pt concentrations were highest in kidneys and liver. TNO-38 is adequately water soluble. Its reported antitumour activity is consistently lower than that of CDDP. The drug's toxicity was, in general, comparable to that of CDDP. Its pharmacokinetic profile was very similar to that of CDDP. It is concluded that TNO-38 should probably not be further evaluated in clinical studies.

Isomer-dependent cytostatic activity of bis(1-aziridinyl)cyclophosphazenes.

A number of recently synthesized mono- and bis(1-aziridinyl) derivatives of the inorganic ring systems (NPCl2)3 and (NPCl2)4 was tested for their cytostatic activity in vitro (L1210 and L5178Y cells) and in vivo (intraperitoneal leukemia L1210 in CDF1 mice). Generally, the nongeminal bis(1-aziridinyl) isomers (either trans or cis) appear to be potent tumor growth inhibitors in contrast to their geminally substituted and mono(1-aziridinyl)-substituted analogues. A relationship between the biological activity and the number of alkylating centers (i.e., P atoms carrying one or two aziridinyl groups) is proposed.