Novel agents effective against solid tumors: the diarylsulfonylureas. Synthesis, activities, and analysis of quantitative structure-activity relationships.

A series of diarylsulfonylureas with exceptionally broad-spectrum activity against syngeneic rodent solid tumors in vivo is described. Their discovery resulted from a program dedicated to in vivo screening for novel oncolytics in solid tumor models, rather than traditional ascites leukemia models. The structures, oral efficacy, side-effect profile, and mechanism of action of these sulfonylureas appear to be distinct from previously known classes of oncolytics. An extensive series of analogues was prepared to probe structure-activity relationships (SAR), with particular focus on the substituent patterns of each aryl domain. Quantitative analysis of these substituent SARs, using the method of cluster significance analysis, showed the lipophilicity of the substituents to be the dominant determinant of activity. One compound from the series, LY186641 (104, sulofenur), has progressed to Phase I clinical trials as an antitumor drug.

Evaluation of the antitumor activity of gemcitabine (2',2'-difluoro-2'-deoxycytidine).

A new pyrimidine antimetabolite, 2',2'-difluorodeoxycytidine, Gemcitabine (LY188011, dFdCyd) has been synthesized and evaluated in experimental tumor models. dFdCyd is a very potent and specific deoxycytidine analogue. The concentration required for 50% inhibition of growth is 1 ng/ml in the CCRF-CEM human leukemia cell culture assay. Concurrent addition of deoxycytidine to the cell culture system provides about a 1000-fold decrease in biological activity. The inhibition of growth of human leukemia cells in culture led to the in vivo evaluation of this compound as a potential oncolytic agent. Maximal activity in vivo was seen with dFdCyd when administered on an every third day schedule. 1-beta-D-Arabinofuranosylcytosine, administered on a daily for 10-day schedule, was directly compared to dFdCyd in this evaluation. dFdCyd demonstrated good to excellent antitumor activity in eight of the eight murine tumor models evaluated. 1-beta-D-Arabinofuranosylcytosine was substantially less active or had no activity in these same tumor models. This in vivo activity against murine solid tumors supports the conclusion that dFdCyd is an excellent candidate for clinical trials in the treatment of cancer.

Studies of the antitumor activity of (2-alkoxyalkyl)- and (2-alkoxyalkenyl)phosphocholines.

Analogues of the synthetic antitumor phospholipid ALP (1-octadecyl-2-methyl-sn-glycero-3-phosphocholine; alkyl lysophospholipid) in which the 1-ether oxygen atom has been removed have been prepared and evaluated for in vitro and in vivo anticancer activity. Compounds are presented in which the saturated long chain varies in length from 8 to 25 carbon atoms. Sites of unsaturation are also incorporated into the framework in some examples. In particular, rac-(2-ethoxyeicosyl)phosphocholine (10) displays the best in vivo activity of the chemical series against a variety of transplanted tumors and activates murine peritoneal macrophages to express tumor cytotoxicity in vitro. However, 10 does not offer the wide spectrum of antitumor activity we feel necessary to warrant further study.

Selective targeting of magnetic albumin microspheres containing low-dose doxorubicin: total remission in Yoshida sarcoma-bearing rats.

Magnetically responsive albumin microspheres containing doxorubicin hydrochloride were selectively localized in Yoshida sarcoma tumors. Tumors were implanted subcutaneously in the tail of Holtzman rats and allowed to grow to at least 200 mm2 size before initiation of experimental treatment. Drug-bearing microspheres at a dose level of either 0.5 or 2.5 mg/kg were infused proximal to the tumor via the ventral caudal artery. A bipolar permanent magnet was placed adjacent to the tumor during the infusion to effect localization. Control animals were treated with free doxorubicin infused intra-arterially at 5.0 mg/kg or 0.5 mg/kg. In other test groups animals received placebo microspheres localized in the tumor via influence of the external magnetic field, or drug-containing microspheres were infused without utilization of the magnet to effect localization. Of the 22 animals receiving magnetically localized doxorubicin microspheres 17 had total histological remission of the tumor. The remaining animals demonstrated marked tumor regression representing as much as 500-600 mm2 decrease in tumor size. While no deaths or metastases occurred in the groups receiving localized drug, animals treated with free doxorubicin, placebo microspheres or non-localized doxorubicin microspheres exhibited a significant increase in tumor size with metastases and subsequent death in 90-100% of the animals. No significant differences were noted in tumor regression/remission data between the 0.5 and 2.5 mg/kg dose levels of magnetically localized doxorubicin spheres. These results represent a significant advance in targeted chemotherapy in that 77% of the animals in the magnetically localized doxorubicin microsphere treatment groups exhibited total remission after only one regimen of drug therapy.

Selective targeting of magnetic albumin microspheres to the Yoshida sarcoma: ultrastructural evaluation of microsphere disposition.

Magnetic albumin microspheres (1 micron average diameter) were selectively targeted to subcutaneous solid Yoshida sarcoma tumors (average size 450 mm2) in Holtzman rats. This was accomplished by placing an external magnet adjacent to the tumor while the microspheres were infused. Microspheres contained ultra-fine particles of Fe3O4 and no drug (placebo). Placebo microspheres were used due to the previously demonstrated rapid tumoricidal effect of targeted low-dose doxorubicin microspheres. Animals were killed 10 min, 60 min, 30 min, 24 hr and 72 hr after microsphere administration and tumors were examined by transmission electron microscopy to determine the in vivo disposition of the magnetically targeted microspheres. Using placebo microspheres, we have demonstrated microspheres endocytosed in endothelial cells as early as 10 min after infusion. By 30 min microspheres can be seen in the extravascular compartment, sitting adjacent to tumor cells and occasionally in tumor cells. By 24 hr the majority of microspheres have been endocytosed by tumor cells. Microspheres were still observed within tumor cells as late as 72 hr after administration. The rapid extravasation and cellular uptake of magnetically focused microspheres explains the extremely rapid tumoricidal effect previously observed when doxorubicin-containing microspheres were targeted to the tumor.

Structure-activity relationships of dimeric Catharanthus alkaloids. 2. Experimental antitumor activities of N-substituted deacetylvinblastine amide (vindesine) sulfates.

While structure-activity relationships for vinblastine (VLB), vincristine, deacetyl-VLB, and deacetyl-VLB amide (vindesine, VDS) in several tumor and leukemia models have been reported previously, the present study explores these relationships for a series of N-substituted vindesine analogues. These compounds were prepared from the reaction of deacetyl-VLB acid azide with the appropriate amines and were characterized by mass spectral analysis, 1H and 13C NMR spectra, electrometric titration, and infrared spectra. N-Alkylvindesines have reduced activity compared to that of VDS against the Gardner lymphosarcoma (GLS). N-beta-Hydroxyethyl-VDS surpasses vindesine in its activity against the Ridgway osteogenic sarcoma and the GLS, whereas against the B16 melanoma it is less active than VDS. N-beta-(4-Hydroxyphenethyl)-VDS, envisaged as a substrate for the enzyme tryosinase, was shown to be more active than VDS against the B16 melanoma but has only marginal activity against the GLS. In terms of collective antitumor activity against the model systems used, vindesine emerges as the congener with optimum qualities. Bis(N-ethylidenevindesine) disulfide, the first example of a bridged bisvindesine and comparable to VDS in its antitumor profile, shows evidence of activity against a P388/VCR leukemia strain known to be resistant to maytansine as well as to vincristine.

Structure-activity relationships of dimeric Catharanthus alkaloids. 1. Deacetylvinblastine amide (vindesine) sulfate.

Exploration of the effects of "minor" structural differences on the antitumor activity and toxicity of dimeric Catharanthus alkaloids resulted in the preparation of deacetylvinblastine amide (vindesine, VDS) from either vinblastine (VLB) or deacetylvinblastine. Adequate amounts of vindesine for biological testing were prepared by preferential hydrazinolysis of the C23-ester in the vindoline moiety of VLB, followed by hydrogenolysis of the resulting deacetylvinblastine hydrazide. Vindesine in its activity spectrum against rodent tumor systems resembles vincristine (VCR) rather than its parent VLB, while its neurotoxic potential appears to be less than that of VCR. The experimental models developed to estimate this potential include in vitro measurements of axoplasmic transport effects in the cat sciatic nerve and the estimation of neuromuscular disturbances in chickens and monkeys by vindesine in comparison with VCR. A radioimmunoassay for VLB, VCR, and VDS, developed by means of deacetylvinblastine acid azide, has been used to study the pharmacokinetics of vindesine in man. The clinical investigation of vindesine is in progress. Deacetylvinblastine, in contrast to earlier reports, showed activity against several murine tumor systems.

Alkaloids of Vinca rosea L. (Catharanthus roseus G. Don). 38. 4'-Dehydrated derivatives.

A series of 4'-dehydrated derivatives of various dimeric Vinca alkaloids has been synthesized to further define the structure-activity relationships of Vinca alkaloids with onolytic potency. The concentrated sulfuric acid dehydration in most cases gave mixtures of the 3',4'-and two isomeric 4',20'-alkenes, which were isolated and characterized primarily by proton and 13C NMR. Compound tested for antitumor activity include the three dehydro isomers of 4'-deacetylvinblastine, 4-deacetylvincristine, and 4-deacetylvinblastine-23-amide and some4'-dehydrated derivatives epimeric at C-18'. Generally, the decrease in toxicity imparted by the new double bond was accompained by a decrease in potency. An exception was 3',4'-dehydro-4-deacetylvincristine, which showed a decrease in toxicity and increase in potency against at least one tumor in which vincristine itself has little effect.

Activity of 6-methyl-8-substituted ergolines against the 7,12-dimethylbenz(a)anthracene-induced mammary carcinoma.

The ability of a series of 8-beta-carboxamido ergolines, 8-formamido ergolines, and 8-methyl ergolines to cause regressions of established dimethylbenz[a]anthracene-induced mammary carcinomas was compared to some ergot alkaloids. Although most of the ergoline derivatives depressed serum prolactin concentrations in rats, only a few had pronounced effects against the dimethylbenz[a]anthracene-induced mammary carcinoma in rats. Some derivatives from each of the three groups of substituted ergolines gave comparable activities against the dimethylbenz[a]anthracene-induced mammary carcinoma.