Discovery of HN37 as a Potent and Chemically Stable Antiepileptic Drug Candidate.

We previously reported that P-retigabine (P-RTG), a retigabine (RTG) analogue bearing a propargyl group at the nitrogen atom in the linker of RTG, displayed moderate anticonvulsant efficacy. Recently, our further efforts led to the discovery of HN37 (pynegabine), which demonstrated satisfactory chemical stability upon deleting the ortho liable -NH2 group and installing two adjacent methyl groups to the carbamate motif. HN37 exhibited enhanced activation potency toward neuronal Kv7 channels and high in vivo efficacy in a range of pre-clinical seizure models, including the maximal electroshock test and a 6 Hz model of pharmacoresistant limbic seizures. With its improved chemical stability, strong efficacy, and better safety margin, HN37 has progressed to clinical trial in China for epilepsy treatment.

Antinociceptive Efficacy of Retigabine and Flupirtine for Gout Arthritis Pain.

INTRODUCTION: Gout arthritis is an inflammatory disease characterized by severe acute pain. The goal of pharmacological gout arthritis treatments is to reduce pain, and thereby increase the patient's quality of life. The Kv7/M channel activators retigabine and flupirtine show analgesic efficacy in animal models of osteoarthritic pain. We hypothesized that these drugs may also alleviate gout arthritis pain. OBJECTIVE: To determine the effects of retigabine and flupirtine on pain behavior associated with monosodium urate (MSU)-induced gout arthritis. METHODS: The gout arthritis model was established with an intra-articular injection of MSU into the right ankle joint, animals were treated with retigabine or flupirtine, and pain-related behaviors were assessed. RESULTS: Retigabine and flupirtine significantly increased the mechanical threshold and prolonged the paw withdrawal latency in a rat model of gout arthritis pain in a dose-dependent manner. The antinociceptive effects of retigabine and flupirtine were fully antagonized by the Kv7/M channel blocker XE991. CONCLUSION: Retigabine and flupirtine showed antinociceptive effects for MSU-induced gout pain at different times during pain development.

N,N'-Diacetyl-p-phenylenediamine restores microglial phagocytosis and improves cognitive defects in Alzheimer's disease transgenic mice.

As a central feature of neuroinflammation, microglial dysfunction has been increasingly considered a causative factor of neurodegeneration implicating an intertwined pathology with amyloidogenic proteins. Herein, we report the smallest synthetic molecule (N,N'-diacetyl-p-phenylenediamine [DAPPD]), simply composed of a benzene ring with 2 acetamide groups at the para position, known to date as a chemical reagent that is able to promote the phagocytic aptitude of microglia and subsequently ameliorate cognitive defects. Based on our mechanistic investigations in vitro and in vivo, 1) the capability of DAPPD to restore microglial phagocytosis is responsible for diminishing the accumulation of amyloid-ß (Aß) species and significantly improving cognitive function in the brains of 2 types of Alzheimer's disease (AD) transgenic mice, and 2) the rectification of microglial function by DAPPD is a result of its ability to suppress the expression of NLRP3 inflammasome-associated proteins through its impact on the NF-κB pathway. Overall, our in vitro and in vivo investigations on efficacies and molecular-level mechanisms demonstrate the ability of DAPPD to regulate microglial function, suppress neuroinflammation, foster cerebral Aß clearance, and attenuate cognitive deficits in AD transgenic mouse models. Discovery of such antineuroinflammatory compounds signifies the potential in discovering effective therapeutic molecules against AD-associated neurodegeneration.

Development and application of anthelminthic drugs in China.

China was once a country plagued by parasitic diseases. At the beginning of the founding of the People's Republic of China, nearly 80% of the population suffered from parasitic diseases because of poverty and poor sanitary conditions. After nearly 70 years of development, China has made remarkable achievements in the prevention and control of parasitic diseases, and the prevalence of parasitic diseases has been greatly reduced. In addition to organizational leadership from the government and various preventive measures, drug treatment and drug research & development are important and irreplaceable links in prevention and control work. Since the 1950s, China has begun to introduce, produce and imitate antiparasitic drugs from abroad, such as santonin, benzimidazole, and praziquantel. Chinese scientists have also contributed to the optimization of production techniques, improvements in drug formulation, the application in the clinic and the mechanisms of actions of generic drugs. At the same time, China has independently developed tribendimidine (TrBD, a broad spectrum anthelminthic), and its anthelminthic spectrum has been comprehensively studied. It is active against almost 20 parasites, is especially superior to benzimidazoles against Necator americanus, and surpasses the effectiveness of praziquantel against Clonorchis sinensis. In the treatment of tapeworm disease, the traditional Chinese medicines pumpkin seeds and betel nuts have good curative effects for taeniasis. Chinese scientists have explored the action modes and clinical administration methods of pumpkin seeds and betel nuts, which is still the main clinical regimen for the disease. This paper reviews the history and progress of the study of anthelmintics in intestinal helminth infections since the founding of the People's Republic of China and aiming to support clinicians and drug researchers in China and other countries.

Ancient and modern anticonvulsants act synergistically in a KCNQ potassium channel binding pocket.

Epilepsy has been treated for centuries with herbal remedies, including leaves of the African shrub Mallotus oppositifolius, yet the underlying molecular mechanisms have remained unclear. Voltage-gated potassium channel isoforms KCNQ2-5, predominantly KCNQ2/3 heteromers, underlie the neuronal M-current, which suppresses neuronal excitability, protecting against seizures. Here, in silico docking, mutagenesis and cellular electrophysiology reveal that two components of M. oppositifolius leaf extract, mallotoxin (MTX) and isovaleric acid (IVA), act synergistically to open neuronal KCNQs, including KCNQ2/3 channels. Correspondingly, MTX and IVA combine to suppress pentylene tetrazole-induced tonic seizures in mice, whereas individually they are ineffective. Co-administering MTX and IVA with the modern, synthetic anticonvulsant retigabine creates a further synergy that voltage independently locks KCNQ2/3 open. Leveraging this synergy, which harnesses ancient and modern medicines to exploit differential KCNQ isoform preferences, presents an approach to developing safe yet effective anticonvulsants.

Inhibition of HDAC3 prevents diabetic cardiomyopathy in OVE26 mice via epigenetic regulation of DUSP5-ERK1/2 pathway.

Inhibition of total histone deacetylases (HDACs) was phenomenally associated with the prevention of diabetic cardiomyopathy (DCM). However, which specific HDAC plays the key role in DCM remains unclear. The present study was designed to determine whether DCM can be prevented by specific inhibition of HDAC3 and to elucidate the mechanisms by which inhibition of HDAC3 prevents DCM. Type 1 diabetes OVE26 and age-matched wild-type (WT) mice were given the selective HDAC3 inhibitor RGFP966 or vehicle for 3 months. These mice were then killed immediately or 3 months later for cardiac function and pathological examination. HDAC3 activity was significantly increased in the heart of diabetic mice. Administration of RGFP966 significantly prevented DCM, as evidenced by improved diabetes-induced cardiac dysfunction, hypertrophy, and fibrosis, along with diminished cardiac oxidative stress, inflammation, and insulin resistance, not only in the mice killed immediately or 3 months later following the 3-month treatment. Furthermore, phosphorylated extracellular signal-regulated kinases (ERK) 1/2, a well-known initiator of cardiac hypertrophy, was significantly increased, while dual specificity phosphatase 5 (DUSP5), an ERK1/2 nuclear phosphatase, was substantially decreased in diabetic hearts. Both of these changes were prevented by RGFP966. Chromatin immunoprecipitation (ChIP) assay showed that HDAC3 inhibition elevated histone H3 acetylation on the DUSP5 gene promoter at both two time points. These findings suggest that diabetes-activated HDAC3 inhibits DUSP5 expression through deacetylating histone H3 on the primer region of DUSP5 gene, leading to the derepression of ERK1/2 and the initiation of DCM. The present study indicates the potential application of HDAC3 inhibitor for the prevention of DCM.

Activation of peripheral KCNQ channels attenuates inflammatory pain.

BACKGROUND: Refractory chronic pain dramatically reduces the quality of life of patients. Existing drugs cannot fully achieve effective chronic pain control because of their lower efficacy and/or accompanying side effects. Voltage-gated potassium channels (KCNQ) openers have demonstrated their analgesic effect in preclinical and clinical studies, and are thus considered to be a potential therapeutic target as analgesics. However, these drugs exhibit a narrow therapeutic window due to their imposed central nerve system (CNS) side effects. To clarify the analgesic effect by peripheral KCNQ channel activation, we investigated whether the analgesic effect of the KCNQ channel opener, retigabine, is inhibited by intracerebroventricular (i.c.v.) administration of the KCNQ channel blocker, 10, 10-bis (4-Pyridinylmethyl)-9(10H) -anthracenone dihydrochloride (XE-991) in rats. RESULTS: Oral administration (p.o.) of retigabine showed an anticonvulsant effect on maximal electronic seizures and an analgesic effect on complete Freund's adjuvant-induced thermal hyperalgesia. However, impaired motor coordination and reduced exploratory behavior were also observed at the analgesic doses of retigabine. Administration (i.c.v.) of XE-991 reversed the retigabine-induced anticonvulsant effect, impaired motor coordination and reduced exploratory behavior but not the analgesic effect. Moreover, intraplantar administration of retigabine or an additional KCNQ channel opener, N-(6-Chloro-pyridin-3-yl)-3,4-difluoro-benzamide (ICA-27243), inhibited formalin-induced nociceptive behavior. CONCLUSIONS: Our findings suggest that the peripheral sensory neuron is the main target for KCNQ channel openers to induce analgesia. Therefore, peripheral KCNQ channel openers that do not penetrate the CNS may be suitable analgesic drugs as they would prevent CNS side effects.

Safety profile of two novel antiepileptic agents approved for the treatment of refractory partial seizures: ezogabine (retigabine) and perampanel.

INTRODUCTION: Complex-partial seizures are frequently resistant to antiepileptic therapy. Two new medications with mechanisms of action novel within the antiepileptic class have recently received approval for the adjunctive treatment of partial (focal) seizures. AREAS COVERED: A Medline search was conducted to identify preclinical and clinical studies of ezogabine and perampanel. This was supplemented with additional articles obtained from online sources and information provided by the FDA and the manufacturers. The focus of this review is on the safety profiles of ezogabine (retigabine), a novel antiepileptic that targets voltage-gated potassium channels, and perampanel, a noncompetitive α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate glutamate receptor antagonist. EXPERT OPINION: Central nervous system effects are predominant within the adverse event profiles of both ezogabine and perampanel. In addition, ezogabine exerts its inhibitory effects on potassium channels in the urogenital tract potentially resulting in urinary retention and related outcomes. Recent reports of blue discoloration of the skin and in the retinas of long-term ezogabine users have surfaced. Both drugs have demonstrated the ability to induce neuropsychiatric symptoms. Though both are welcome additions to the antiepileptic drug class, additional monitoring, appropriate counseling, and careful selection of patients are warranted to minimize adverse events.

Activation of voltage-gated KCNQ/Kv7 channels by anticonvulsant retigabine attenuates mechanical allodynia of inflammatory temporomandibular joint in rats.

BACKGROUND: Temporomandibular disorders (TMDs) are characterized by persistent orofacial pain and have diverse etiologic factors that are not well understood. It is thought that central sensitization leads to neuronal hyperexcitability and contributes to hyperalgesia and spontaneous pain. Nonsteroidal anti-inflammatory drugs (NSAIDs) are currently the first choice of drug to relieve TMD pain. NSAIDS were shown to exhibit anticonvulsant properties and suppress cortical neuron activities by enhancing neuronal voltage-gated potassium KCNQ/Kv7 channels (M-current), suggesting that specific activation of M-current might be beneficial for TMD pain. RESULTS: In this study, we selected a new anticonvulsant drug retigabine that specifically activates M-current, and investigated the effect of retigabine on inflammation of the temporomandibular joint (TMJ) induced by complete Freund's adjuvant (CFA) in rats. The results show that the head withdrawal threshold for escape from mechanical stimulation applied to facial skin over the TMJ in inflamed rats was significantly lower than that in control rats. Administration of centrally acting M-channel opener retigabine (2.5 and 7.5 mg/kg) can dose-dependently raise the head withdrawal threshold of mechanical allodynia, and this analgesic effect can be reversed by the specific KCNQ channel blocker XE991 (3 mg/kg). Food intake is known to be negatively associated with TMJ inflammation. Food intake was increased significantly by the administration of retigabine (2.5 and 7.5 mg/kg), and this effect was reversed by XE991 (3 mg/kg). Furthermore, intracerebralventricular injection of retigabine further confirmed the analgesic effect of central retigabine on inflammatory TMJ. CONCLUSIONS: Our findings indicate that central sensitization is involved in inflammatory TMJ pain and pharmacological intervention for controlling central hyperexcitability by activation of neuronal KCNQ/M-channels may have therapeutic potential for TMDs.

The effect of tribendimidine and its metabolites against Necator americanus in golden hamsters and Nippostrongylus braziliensis in rats.

The antinematode effect of tribendimidine (TBD) and its metabolites has been studied. A total of 107 hamsters were each infected with 250 Necator americanus third stage infective larvae (NaL3) for 25 days. In the first test, 75 hamsters were divided equally into 15 groups for determination of ED(50) and ED(90.) Among them, five groups were treated orally with TBD or its metabolite, p-(1-dimethylamino ethylimino)aniline (aminoamidine, deacylated amidantel, BAY d 9216, dADT), at single doses of 1, 2, 4, 8, and 16 mg/kg. The remaining five groups were administered with acetylated dADT (AdADT) at single oral doses of 8, 12, 18, 24, and 30 mg/kg. In the second test, 20 hamsters were equally divided into four groups. Two groups were treated intramuscularly with TBD and dADT at a single dose of 16 mg/kg, while in the remaining two groups, single intramuscular dose of AdADT 15 or 30 mg/kg was administered. In the third test, two groups of six hamsters were treated orally with terephthalaldehyde (TPAL) and terephthalic acid (TPAC) at a single dose of 1,000 mg/kg. Other 85 rats, each infected with 300 Nippostrongylus braziliensis third stage infective larvae (NbL3), were used in three tests. For determination of ED(50) and ED(90) in the first test, five groups of five rats were treated orally with TBD or dADT at single doses of 3.0, 4.2, 5.9, 8.2, and 11.5 mg/kg or 2.0, 2.9, 4.2, 6.1, and 8.8 mg/kg, respectively. In the second test, three groups of eight to nine rats were treated orally with TBD at a single 8.4-mg/kg dose (ED(90)) and AdADT 100 or 200 mg/kg, respectively. In the third test, two groups of four rats were treated orally with TPAL and TPAC at a single dose of 1,000 mg/kg. Twenty-four to 48 h post-treatment, all the feces of each hamster and rat were collected for recovery of worms expelled from the feces. Following this period, all of the animals were sacrificed, and the adult hookworm or N. braziliensis from small intestine and large intestine were recovered and counted for calculation of worm burden reduction. The results showed that the ED(50) and ED(90) for TBD, dADT, and AdADT determined in treatment of N. americanus-infected hamsters were 1.849 and 13.598, 3.922 and 54.354, as well as 20.966 and 51.633 mg/kg, respectively. In intramuscular administration of TBD and dADT at single dose of 16 mg/kg or AdADT 30 mg/kg, similar worm burden reductions of 71.4-76.3% were observed. Two other metabolites, i.e., TPAL and TPAC, exhibited no effect against N. americanus. The ED(50) and ED(90) for TBD and dADT determined in treatment of rats infected with N. braziliensis were 3.234 and 8.435, as well as 2.345 and 5.104 mg/kg. Oral administration of AdADT at a higher single dose of 100 or 200 mg/kg resulted in worm burden reductions of 11.9-46.3%, which was significantly lower than 84.5% of worm burden reduction obtained from rats treated with TBD 8.4 mg/kg. The results indicate that in oral administration, TBD exhibits slightly better effect against N. americanus in hamsters than dADT, but AdADT possesses less effect; TBD, dADT, and AdADT show promising effect in intramuscular treatment of N. americanus-infected hamsters; the effect of oral dADT against N. braziliensis in rats is somewhat better than TBD, while AdADT endorses poor effect; and TPAL and TPAC are ineffective metabolites of TBD against both species of nematodes.

Small molecule modulators of copper-induced Abeta aggregation.

Our design of bifunctional metal chelators as chemical probes and potential therapeutics for Alzheimer's disease (AD) is based on the incorporation of a metal binding moiety into structural frameworks of Abeta aggregate-imaging agents. Using this strategy, two compounds 2-[4-(dimethylamino)phenyl]imidazo[1,2-a]pyridine-8-ol (1) and N(1),N(1)-dimethyl-N(4)-(pyridin-2-ylmethylene)benzene-1,4-diamine (2) were prepared and characterized. The bifunctionality for metal chelation and Abeta interaction of 1 and 2 was verified by spectroscopic methods. Furthermore, the reactivity of 1 and 2 with Cu(II)-associated Abeta aggregates was investigated. The modulation of Cu(II)-triggered Abeta aggregation by 1 and 2 was found to be more effective than that by the known metal chelating agents CQ, EDTA, and phen. These studies suggest a new class of multifunctional molecules for the development of chemical tools to unravel metal-associated events in AD and potential therapeutic agents for metal-ion chelation therapy.

The in vitro and in vivo effect of tribendimidine and its metabolites against Clonorchis sinensis.

The purpose of the study was to understand the in vitro and in vivo effect of tribendimidine (TBD) and its metabolites of p-(1-dimethylamino ethylimino)aniline (aminoamidine, deacylated amidantel, BAY d 9216, dADT), acetylated dADT (AdADT), terephthalaldehyde (TPAL), and terephthalic acid (TPAC) against adult Clonorchis sinensis. In in vitro test, the adults of C. sinensis were placed to each of the 24 wells of a Falcon plate and maintained in Hanks' balanced salt solution-20% calf serum. Besides observation on the direct in vitro effect of TBD and its metabolites, the worms exposed to TBD and its metabolites for 1-24 h were transferred to the medium without drug and incubated continually for another 72 h. The reversible effect of TBD and its metabolites was assessed by the recovery of worm motor activity and parasite survival. In in vivo test, 235 rats were divided into five batches for oral infection of each rat with 50 C. sinensis metacercariae. Five to 6 weeks post-infection, groups of rats were treated orally or intramuscularly with a single dose of TBD or its metabolites, while untreated but infected rats served as control. All treated rats were killed 2 weeks post-treatment for assessment of efficacy. When adult C. sinensis were exposed to TBD or dADT 0.5 microg/mL, they were paralyzed rapidly accompanied by dilatation of the gut. The in vitro effect of AdADT decreased significantly, which was at least lower than 20- to 40-fold compared with TBD and dADT. TPAL and TPAC at a high concentration of 100 microg/mL exhibited no effect against adult C. sinensis. In the worms exposed to TBD or dADT 1 microg/mL for 1 h, well recovery of the worm motor activity from paralysis was seen in the medium without drug. If exposure time extended to 4-24 h before transferred to the medium without drug, few worms were dead and most worms showed very poor recovery of their activity. When the worms exposed to TBD or dADT 10 microg/mL for 1, 4, and 24 h were transferred to the drug-free medium, recovery of poor motor activity of worms or worm death was seen. In the worms exposed to AdADT 20 and 40 microg/mL for 1-24 h, more worms recovered poor motor activity in the medium without drug. In rats infected with C. sinensis and treated orally with TBD or dADT, the ED(50) and ED(95) were 20.318 and 195.358 mg/kg or 18.969 and 268.882 mg/kg. Under the equal dosages used in the treatment of rats infected with C sinensis, the effects between TBD and dADT or TBD and AdADT were similar. Intramuscular TBD or dADT at a single dose of 12.5-75 mg/kg showed effect against adult C. sinensis harbored in rats. TPAL and TPAC exhibit no effect against C sinensis harbored in rats treated orally with a higher dose of 1 g/kg. The results indicate that TBD and dADT exhibit a strong in vitro effect to paralyze the adult C. sinensis, but less in vitro effect was seen in AdADT. TBD, dADT, and AdADT exhibit similar therapeutic effect in oral treatment of rats infected with C. sinensis, and intramuscular TBD and dADT also show promising effect against C. sinensis in rats. TPAL and TPAC are ineffective metabolites of TBD.

Ion channel targets - select biosciences' fourth annual conference.

Select Biosciences' Fourth Annual Ion Channel Targets conference brought together scientists from industry and academia who are interested in the discovery of therapeutics targeted to various ion channels implicated in human disease. Topics addressed included methodological aspects of screening for ion channel drugs, the discovery of novel inhibitors and activators of ion channels that are drug candidates, and suggestions of potential new ion channel targets.

[Development of novel antihelminthic therapies]. / Nouveautés thérapeutiques dans les traitements antihelminthiques.

Since existing medications are effective, easy-to-use and well tolerated, research in the treatment of helminthiasis in humans seems to be at a standstill. However this type of parasitic infection is still a major public-health concern and heavy socioeconomic burden in many countries. Despite observance of the first disturbing signs of resistance, release of new antihelminthics on the market (e.g. nitazoxanide and tribendimidine) remains slow. Treatment using drug combinations offers an alternative for therapeutic failure in some cases. Ongoing studies focusing on development of a vaccine, on adaptation of medications used in veterinary medicine or on the action of medicinal plants hold forth hope of finding effective new treatments.

Histogranin-like antinociceptive and anti-inflammatory derivatives of o-phenylenediamine and benzimidazole.

Histogranin (HN)-like nonpeptides were designed and synthesized using benzimidazole (compound 1) and o-phenylenediamine (compounds 2-7) as scaffolds for the attachment of phenolic hydroxyl and basic guanidino pharmacophoric elements present in HN. The benzimidazole derivative N-5-guanidinopentanamide-(2R)-yl-2-(p-hydroxybenzyl)-5-carboxybenzimidazole (1) and the o-phenylenediamine derivative N-5-guanidinopentanamide-(2S)-yl-2-N-(p-hydroxyphenylacetyl) phenylenediamine (2) were more potent analgesics than HN in both the mouse writhing (5.5 and 3.5 as potent as HN, respectively) and tail-flick (11.8 and 8.0 as potent as HN, respectively) pain assays. Improvements in the potencies and times of action of compound 2 in the mouse writhing test were obtained by attaching carboxyl (6)or p-Cl-benzoyl (7) groups at position 4 of the (2R) o-phenylenediamine derivative (5). In rats, compounds 2 (80 nmol i.t.), 6 (36 nmol i.t.), and 7 (18 nmol i.t.) were effective in blocking both persistent inflammatory pain in the formalin test and hyperalgesia in the complete Freund adjuvant assay. Compounds 2, 6, and 7, but not compound 1 at 10 nmol (i.c.v.) also mimicked the HN (60 nmol i.c.v.) blockade of N-methyl-D-aspartate (NMDA)-induced convulsions in mice. Finally, in primary cultures of rat alveolar macrophages, HN and compounds 1, 2, 6, and 7 (10(-8) M) significantly blocked lipopolysaccharide-induced cyclooxygenase-2 induction and prostaglandin E(2) secretion. These studies indicate that both derivatives of benzimidazole and o-phenylenediamine mimic the in vivo antinociceptive and in vitro anti-inflammatory effects of HN, but the HN protection of mice against NMDA-induced convulsions is mimicked only by the o-phenylenediamine derivatives.

Progress report on new antiepileptic drugs: a summary of the Third Eilat Conference.

The Third Eilat Conference on New Antiepileptic Drugs was held at the Royal Beach Hotel from May 27 to May 30, 1996. Epileptologists and scientists from 20 countries attended the conference, which was held to discuss critical issues in drug development, new antiepileptic drugs (AEDs) in development, progress reports and recent findings of newly marketed AEDs, the use of AEDs in special populations and their utilization in non-epileptic disorders. Over the last seven years, six new AEDs have been introduced worldwide and new information on their safety and efficacy has become available. These include felbamate, gabapentin, lamotrigine, oxcarbazepine, topiramate and vigabatrin. Drugs in development include those at an advanced stage, such as remacemide and tiagabine, as well as those just entering clinical trials, such as rufinamide (CGP 331010) and levetiracetam (ucb LO59). The following is a summary of the presentations for drugs in development and recent findings on newly marketed drugs.

Inhibitory effects of N,N'-diphenyl-p-phenylenediamine on the early stage of the enhanced hepatocarcinogenesis caused by coadministration of ethionine and a choline-deficient L-amino acid-defined diet in rats.

Effects of N,N'-diphenyl-p-phenylenediamine (DPPD), an antioxidant, on liver carcinogenesis caused by a choline-deficient L-amino acid-defined (CDAA) diet containing ethionine were studied in Fischer 344 rats. Male animals, 6 weeks old, were fed a CDAA diet, a choline-supplemented L-amino acid-defined (CSAA) diet or a CDAA diet containing 0.05% ethionine with or without 0.2% DPPD. Histological changes and lesions positive for gamma-glutamyltransferase (GGT) were analyzed 12 weeks after the beginning of the experiment. The levels of 8-hydroxyguanine (8-OHGua) in DNA and 2-thiobarbituric acid-reacting substances (TBARS) were measured as the parameters for cellular oxidative damage after 4 and 11 days of treatment. Expression of c-myc and c-Ha-ras was also investigated in relation to cell proliferation after 2, 4, 8 and 11 days. Histologically, development of diffuse fatty liver observed in rats fed a CDAA diet was inhibited, while massive oval cell proliferation and cholangiofibrosis resulted from the addition of ethionine with/without DPPD. The sizes but not numbers of GGT-positive lesions seen in the liver of rats fed a CDAA diet were increased and the levels of 8-OHGua formation and TBARS generation were also increased by the ethionine supplement. Both numbers and sizes of GGT-positive lesions were decreased and the level of TBARS, but not 8-OHGua, was decreased by adding DPPD. The increased expression of c-myc and c-Ha-ras detected in the liver of rats fed a CDAA diet was further increased by addition of ethionine and again reduced by DPPD. These results indicate that an antioxidant DPPD can inhibit the early stage of enhanced hepatocarcinogenesis caused by coadministration of ethionine and a CDAA diet, by blocking cellular oxidative damage as well as c-myc and c-Ha-ras expression.

Dinaline: a new oral drug against leukemia? Preclinical studies in a relevant rat model for human acute myelocytic leukemia (BNML).

The efficacy and toxicity of Dinaline (GOE 1734; PD 104 208; NSC 328786; 4-amino-N-(2'-aminophenyl)benzamide) was evaluated in the Brown Norway acute myelocytic leukemia, which is generally accepted as a relevant preclinical model for human acute myelocytic leukemia. Upon repeated daily oral administration at least an 8 log leukemic cell kill was achieved with only less than a 1 log kill for normal pluripotent hemopoietic stem cells. Daily split-dose treatment even proved to be more effective and resulted in 40-50% cures. However, toxicity was also more pronounced in particular in regard to the gastrointestinal tract. So far, the mode of action of Dinaline is unknown, but its striking therapeutic index warrants further clinical investigation.

Synthesis, toxicity, and therapeutic efficacy of 4-amino-N-(2'-aminophenyl)-benzamide: a new compound preferentially active in slowly growing tumors.

The present paper describes 4-amino-N-(2'-aminophenyl)benzamide (GOE1734) with regard to synthesis; toxicity in mice, rats, and dogs; and differential therapeutic efficacy in slowly and rapidly proliferating rat tumors. GOE1734, an analog of a group of compounds known for other than antitumor effects with relatively simple N-acyl-O-phenylenediamine structure, is characterized by a low bacterial mutagenic potential after in vitro metabolic activation and DNA-DNA crosslinking activity after in vivo treatment. Maximum tolerated doses in rats and dogs amount to 4 and 1 mg/kg, respectively. High growth-inhibiting efficacy was obtained in intratibially implanted osteosarcoma, in methylnitrosourea-induced primary mammary carcinoma, and in acetoxymethyl-methylnitrosamine-induced colorectal adenocarcinoma. GOE1734 proved to be ineffective in transplanted Yoshida sarcoma and Walker 256 carcinosarcoma when single or multiple doses were administered at dose levels that were moderately toxic or not toxic. Some antitumor effects were observed in L5222 leukemia after ip transplantation, but no effect could be observed after ic implantation or in vitro incubation and subsequent retransplantation of these cells. Since the latter three rat tumors are characterized by relatively short tumor volume doubling times (0.5-2 days), whereas the first three grow slower (tumor volume doubling time, 11-19 days), the remarkable differential antitumor activity of GOE1734 in fast and slowly growing malignancies is striking.