The Inhibition of Cysteine Proteases Rhodesain and TbCatB: A Valuable Approach to Treat Human African Trypanosomiasis.

Human African Trypanosomiasis (HAT) is an endemic parasitic disease of sub-Saharan Africa, caused by two subspecies of protozoa belonging to Trypanosoma genus: T. brucei gambiense and T. brucei rhodesiense. In this context the inhibition of the papain-family cysteine proteases rhodesain and TbCatB has to be considered a promising strategy for HAT treatment. Rhodesain, the major cathepsin L-like cysteine protease of T. brucei rhodesiense, is a lysosomal protease essential for parasite survival. It is involved in parasite invasivity, allowing it to cross the blood-brain barrier (BBB) of the human host, causing the second lethal stage of the disease. Moreover, it plays an important role in immunoevasion, being involved in the turnover of variant surface glycoproteins of the T. brucei coat and in the degradation of immunoglobulins, avoiding a specific immune response by the host cells. On the other hand TbCatB, a cathepsin B-like cysteine protease, present in minor abundance in T. brucei, showed a key role in the degradation of host transferrin, which is necessary for iron acquisition by the parasite. In this review article we now discuss the most active peptide, peptidomimetic and non-peptide rhodesain and TbCatB inhibitors as valuable strategy to treat HAT, due also to the complementary role of the two T. brucei proteases.

Noninvasive theranostic imaging of HSV1-sr39TK-NTR/GCV-CB1954 dual-prodrug therapy in metastatic lung lesions of MDA-MB-231 triple negative breast cancer in mice.

Metastatic breast cancer is an obdurate cancer type that is not amenable to chemotherapy regimens currently used in clinic. There is a desperate need for alternative therapies to treat this resistant cancer type. Gene-Directed Enzyme Prodrug Therapy (GDEPT) is a superior gene therapy method when compared to chemotherapy and radiotherapy procedures, proven to be effective against many types of cancer in pre-clinical evaluations and clinical trials. Gene therapy that utilizes a single enzyme/prodrug combination targeting a single cellular mechanism needs significant overexpression of delivered therapeutic gene in order to achieve therapy response. Hence, to overcome this obstacle we recently developed a dual therapeutic reporter gene fusion that uses two different prodrugs, targeting two distinct cellular mechanisms in order to achieve effective therapy with a limited expression of delivered transgenes. In addition, imaging therapeutic reporter genes offers additional information that indirectly correlates gene delivery, expression, and functional effectiveness as a theranostic approach. In the present study, we evaluate the therapeutic potential of HSV1-sr39TK-NTR fusion dual suicide gene therapy system that we recently developed, in MDA-MB-231 triple negative breast cancer lung-metastatic lesions in a mouse model. We compared the therapeutic potential of HSV1-sr39TK-NTR fusion with respective dual prodrugs GCV-CB1954 with HSV1-sr39TK/GCV and NTR/CB1954 single enzyme prodrug system in this highly resistant metastatic lesion of the lungs. In vitro optimization of dose and duration of exposure to GCV and CB1954 was performed in MDA-MB-231 cells. Drug combinations of 1 µg/ml GCV and 10 µM CB1954 for 3 days was found to be optimal regimen for induction of significant cell death, as assessed by FACS analysis. In vivo therapeutic evaluation in animal models showed a complete ablation of lung metastatic nodules of MDA-MB-231 triple negative breast cancer cells following two consecutive doses of a combination of GCV (40 mg/kg) and CB1954 (40 mg/kg) administered at 5 day intervals. In contrast, the respective treatment condition in animals expressing HSV1-sr39TK or NTR separately, showed minimal or no effect on tumor reduction as measured by bioluminescence (tumor mass) and [(18)F]-FHBG microPET (TK expression) imaging. These highlight the strong therapeutic effect of the dual fusion prodrug therapy and its use in theranostic imaging of tumor monitoring in living animals by multimodality molecular imaging.

E. coli NfsA: an alternative nitroreductase for prodrug activation gene therapy in combination with CB1954.

Prodrug activation gene therapy is a developing approach to cancer treatment, whereby prodrug-activating enzymes are expressed in tumour cells. After administration of a non-toxic prodrug, its conversion to cytotoxic metabolites directly kills tumour cells expressing the activating enzyme, whereas the local spread of activated metabolites can kill nearby cells lacking the enzyme (bystander cell killing). One promising combination that has entered clinical trials uses the nitroreductase NfsB from Escherichia coli to activate the prodrug, CB1954, to a potent bifunctional alkylating agent. NfsA, the major E. coli nitroreductase, has greater activity with nitrofuran antibiotics, but it has not been compared in the past with NfsB for the activation of CB1954. We show superior in vitro kinetics of CB1954 activation by NfsA using the NADPH cofactor, and show that the expression of NfsA in bacterial or human cells results in a 3.5- to 8-fold greater sensitivity to CB1954, relative to NfsB. Although NfsB reduces either the 2-NO(2) or 4-NO(2) positions of CB1954 in an equimolar ratio, we show that NfsA preferentially reduces the 2-NO(2) group, which leads to a greater bystander effect with cells expressing NfsA than with NfsB. NfsA is also more effective than NfsB for cell sensitisation to nitrofurans and to a selection of alternative, dinitrobenzamide mustard (DNBM) prodrugs.

Apaziquone for non-muscle invasive bladder cancer: a critical review.

OBJECTIVE: To describe clinical needs in non-muscle invasive bladder cancer (NMIBC) and review the potential of apaziquone in this respect. METHODS: Epidemiology and clinical practice in NMIBC, as well as new drugs and strategies are reviewed. RESULTS: Bladder cancer is a heterogeneous and frequent disease. Clinical risk factors help in determining additional therapy after initial resection. However, current treatments have clear limitations with regard to efficacy and/or toxicity. New drugs and strategies have been tested recently and are in (pre)clinical use. Intravesical apaziquone (EOquin) is a new drug. It has theoretical advantages for intravesical use, has proven safety and is presently under further clinical evaluation. CONCLUSION: Apaziquone is a promising drug for intravesical use in patients with NMIBC.

Complete remissions in chemotherapy of lung cancer models induced in mice by asbestos.

Chemotherapy trials were run with mice bearing transplants of carcinomas originally induced from fetal mouse lung cells by asbestos. After treatments with a nitrosourea (PCNU), mice bearing transplants of a large-cell carcinoma (ASB XIV) had complete remissions (CR) in 13 of 20 animals on a 15 mg/kg regimen, in 6 of 20 on an 8 mg/kg regimen, and in none of 10 on a 4 mg/kg regimen. With comparable total doses, treatment was most effective when PCNU was given in a few large doses. In groups where CRs occurred, continued PCNU treatment of animals without CRs prolonged survival but yielded no additional CRs. No CRs of ASB XIV occurred in 80 mice treated with eight other anticancer agents or in 50 controls injected with 0.9% NaCl solution. In mice bearing transplants of a squamous cell carcinoma (ASB XIII), treatments with PCNU were followed by CRs in 3 of 38 animals on 15 mg/kg regimens and in 3 of 28 animals on 8 mg/kg regimens. In groups of 6 mice fed a retinoid (Ro 10-9359) and treated with PCNU, CRs of ASB XIII occurred in 3 animals in each of two trials and in none in a third trial. Ro 10-9359 inhibited growth of transplants of squamous cell carcinoma LC 12 that had been induced from fetal mouse lung cells by a polycyclic hydrocarbon. In trials of four other anticancer agents vs. ASB XIII, CRs occurred only with cyclophosphamide (CPA). There were 7 CRs among 8 mice treated with CPA 100 mg/kg x 3, no CRs in 10 after 100 mg/kg x 2, one CR in 8 after 50 mg/kg x 3, and no CRs in 6 after 50 mg/kg x 4. With the 50 mg/kg x 4 regimen of CPA and 7.5 mg/kg PCNU on the same days, there were 5 CRs in 8 mice. As a single agent, aziridinylbenzoquinone (AZQ) increased life span but gave no CRs. There were CRs of ASB XIII in all of 8 mice after toxic combined therapy with PCNU and AZQ. There were no CRs in 66 control mice bearing ASB XIII.

Enhanced antitumor activity of irofulven in combination with thiotepa or mitomycin C.

PURPOSE: Irofulven (6-hydroxymethylacylfulvene, MGI 114, NSC 683863) is a semisynthetic derivative of illudin S, a toxin present in the Omphalotus mushroom. Irofulven has demonstrated activity against a broad range of solid tumors in both xenograft models and human trials. The potential application of administering irofulven in combination with aziridine-containing chemotherapeutic agents was evaluated in this study. METHODS: Human lung carcinoma MV522 cells and BALB/c athymic mice bearing the human lung carcinoma MV522 xenograft were used to evaluate the activity of irofulven in combination with aziridine-containing drugs. RESULTS: Irofulven in combination with either thiotepa or mitomycin C demonstrated a strong synergistic (supraadditive) activity both in vitro and in vivo, that exceeded results obtained with monotherapy at the same or higher doses of these agents. The majority of xenograft-bearing animals that received subtoxic doses of irofulven, and either thiotepa or mitomycin C, demonstrated a complete cure. In contrast, there was no detectable synergistic activity between irofulven and other aziridine-containing drugs, including AZQ and thiotepa metabolites such as TEPA or AZD. CONCLUSIONS: These results indicate that the therapeutic activity of irofulven is enhanced when combined with mitomycin C or thiotepa, and further evaluation of these combinations is therefore warranted.

EO9: a novel bioreductive alkylating indoloquinone with preferential solid tumour activity and lack of bone marrow toxicity in preclinical models.

EO9 is a novel and fully synthetic bioreductive alkylating indoloquinone. Although structurally-related to mitomycin C, EO9 exhibits a distinct preclinical antitumour profile and there are also differences in its biochemical activation. In this study, EO9 was found to demonstrate preferential cytotoxicity against solid tumours in vitro as compared to leukaemia cell lines both in the Corbett two-tumour assay and in the disease-oriented human tumour cell line panel of the U.S. National Cancer Institute. In the latter system activity was particularly apparent in colon, melanoma and central nervous system lines, together with some renal and non-small cell lung lines. Preferential cytotoxicity towards hypoxic versus aerobic EMT6 mouse mammary tumour cells was observed. In vivo, EO9 was inactive against the P388 murine leukaemia, while exerting significant antiproliferative effects against several murine and human solid tumours, including the generally resistant MAC mouse colon tumours and gastric, ovarian and breast xenografts. These results confirmed in vitro observations of preferential solid tumour activity. In animal toxicology studies, EO9 induced vascular congestion in the gastrointestinal tract, but no significant bone marrow toxicity. The LD10 value of EO9 after a single intravenous injection into mice was 9 mg/kg (27 mg/m2). A dose of one-tenth of the mouse equivalent LD10 (2.7 mg/m2), the recommended starting dose for clinical phase I studies, was found to be safe in rats. Considering its distinct mechanism of bioactivation as compared to mitomycin C, its preferential solid tumour activity, its excellent activity against hypoxic cells, and lack of significant bone marrow toxicity in animals studies, EO9 has been selected for clinical evaluation within the framework of the EORTC.

The antitumoral action of polyamine linked cyclophosphazenes on human malignant glioma heterografts in nu/nu mice.

Since the polyamine metabolism system is very active in proliferative glioma cells, polyamine linked drugs are to be considered as potential antineoplastic agents against malignant gliomas. This study reports the trial of a new compound lineage, the Polyamine Linked Cyclophosphazenes, on human glioblastoma heterografts in nu-nu mice. Two agents are tested: DIAM 3 and DIAM 4. Both show an important antineoplastic action either on a chronic treatment schedule or as single dose. Systemic tolerance is satisfactory.

Isolation, synthesis, and antitumor evaluation of spirohydantoin aziridine, a mutagenic metabolite of spirohydantoin mustard.

Spirohydantoin mustard (SHM), a central nervous system directed nitrogen mustard with anticancer activity, was metabolized in the presence of mouse liver postmitochondrial supernatant (9000g fraction) to a nonpolar alkylating metabolite. The metabolite was isolated by thin-layer chromatography of chloroform or ethyl acetate extracts of incubation mixtures, and its structure was established by mass spectral analysis, synthesis, and cochromatography. The metabolite, spirohydantoin aziridine, was mutagenic for Salmonella typhimurium TA1535 in the Ames assay but inactive as an antitumor agent against P388 leukemia in vivo.

Diaziquone as a potential agent for photoirradiation therapy: formation of the semiquinone and hydroxyl radicals by visible light.

When diaziquone was irradiated with 500 nm visible light, hydroxyl free radicals as well as the diaziquone semiquinone were produced. The diaziquone semiquinone is a stable free radical that exhibits a characteristic 5-line electron spin resonance (ESR) spectrum. Since hydroxyl free radicals are short lived, and not observable by conventional ESR, the nitrone spin trap 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) was used to convert hydroxyl radicals into longer lived ESR detectable spin adducts. The formation of hydroxyl radicals was further confirmed by investigating reactions in which hydroxyl radical scavangers, sodium formate and dimethylsulfoxide, compete with the spin traps DMPO or POBN (alpha-(4-Pyridyl-1-oxide)-N- tert-butylnitrone) for hydroxyl free radicals. The products of these scavenging reactions were also trapped with DMPO or POBN. If drug free radicals and hydroxyl free radicals are important in the activity of quinone-containing antitumor agents, AZQ may have a potential in photoirradiation therapy or photodynamic therapy.

[Antitumor activity and pharmacological properties of furizil]. / Protivoopukholevaia aktivnost' i farmakologicheskie svoistva furizila.

The paper discusses the biological properties of 2-(2-furyl)-5-oxymethyl-5-(2,4-diethyleneimino-1,3,5-triazine- 6-yl) amino-1,3-dioxane (furizil), synthesized by substituting ethyleneimine groups for chlorine atoms in individual stereoisomer of a dichlorotriazine derivative. Furizil was found to inhibit the growth of Ehrlich's tumor, Walker's carcinosarcoma, sarcoma 45 and rat ovarian tumors, the inhibition rate ranging 76-100%. Parenterally administered, LD50 appeared to be 6 mg/kg for rats and 15 mg/kg for mice. Studies of chronic toxicity established damaging effects of furizil on hematopoietic, gastrointestinal and reproductive organs. Toxic effects subsided 1-2 weeks after the drug withdrawal.

Diaziquone (AZQ).

Diaziquone is an aziridinylbenzoquinone with properties suggestive of an alkylating agent. The drug has shown broad antitumor activity against numerous transplantable murine tumors including curative activity against several intracerebrally implanted tumors. Parent diaziquone appears to have a t1/2 beta of approximately 30 min. The drug is rapidly and widely distributed to tissues as evidenced by a t1/2 alpha of approximately 1-3 min and a volume of distribution exceeding that of total body water. In addition, it rapidly penetrates the central nervous system, reaching peak concentrations (30-50%) of corresponding plasma levels) in approximately one hour. Diaziquone is rapidly and extensively metabolized by the liver. Diaziquone is a potent marrow suppressive agent inducing significant degrees of leukopenia, granulocytopenia, and thrombocytopenia in humans. Thrombocytopenia is often severe. Although myelosuppression is for the most part dose related, many patients had significant toxicity even at lower doses. Most investigators have attributed this to the extent of prior therapy. Diaziquone demonstrates a very steep dose-response relationship. Myelosuppression was the dose-limiting toxicity in all phase I trials. No nonhematologic dose-limiting toxicity has been identified to date. In phase I and preliminary phase II trials, diaziquone has demonstrated activity against primary brain tumors. Little activity has been seen in other tumor categories. It should be noted, however, that all studies to date have been carried out in heavily pretreated patients. Because of the broad spectrum of antitumor activity in experimental murine tumors, the lack of nonhematologic dose-limiting toxicity, the ability of this drug to attain significant levels in the central nervous system, and the activity of the drug in primary brain tumors, further studies examining its role in the management of patients with cancer are warranted. These studies should be conducted in patients who have had little or no prior therapy in order to better evaluate the efficacy of the drug.

[Quantitative aspects of the relationship of the antitumor activity and toxicity of diaziridinyl-sym. triazines to their physicochemical properties]. / Kolichestvennye aspekty sviazi protivoopukholevoi aktivnosti i toksichnosti diaziridinil-simm. triazinov s ikh fiziko-khimicheskimi svoistvami.

The experiments on rats have shown that there is a linear dependence of the logarithms of reciprocal molar toxic (LD50) and therapeutic (ED50) for sarcoma 45 doses of 6-oxyalkyl-amino-2,4-bis(I-aziridinyl)-sym-triazines and 6-(5-substituted-2,2-dimethyl-1,3-dioxan-5-yl)-amino-2,4-bis(I-aziridinyl)-sym-triazines upon the induction constants of substituents at tertiary carbon, the antitumor activity being more sensitive to the substituent effect compared with the toxicity. The dependence of the logarithms of reciprocal molar therapeutic (ED50 for sarcoma 45 and ED95 for Walker sarcoma) and toxic (LD50 and LD100) doses of the compounds, both synthesized by us and taken from the literature, upon the logarithms of their distribution coefficients in the octanol-water system (IgP) shows a parabolic character with the maximum effect at the extreme point of the parabola. The antitumor activity was more sensitive to a changed IgP than the toxicity.

Pharmacological prophylaxis in the kindling model of epilepsy.

Review of antiepileptic drug assessment to date by means of the kindling model of epilepsy suggests that it fills a gap that is evident in standard screening methods such as maximum electroshock or pentylenetetrazol screening tests. However, in order to obtain a comprehensive profile of antiepileptic drugs regarding prophylaxis of developing seizures and treatment of well-established seizures through the kindling preparation, it is desirable to have the following: (1) standardization of kindling techniques, (2) examination of drug effects on developing as opposed to developed seizures, (3) use of a variety of animal species, involving different functional brain sites, and (4) monitoring of plasma levels of the drug administered. It is envisaged that judicious use of the kindling preparation might also enable us to gain some insight into the mechanisms by which drugs produce their prophylactic or therapeutic effect.