ABSTRACT
We report here the toxicity and therapeutic effects of 2'-alpha-bromohexadecanoyl paclitaxel (BrC16HT), a prodrug form of paclitaxel, in mice. Paclitaxel is the active ingredient of Taxol. The maximum tolerated dose, at a one dose per day for 5-day schedule, was 37.5 mg/kg for BrC16HT compared to 12.5 for Taxol administered IP, and was 12.5-25 mg/kg for either agent administered IV. Dose-dependent therapeutic effects were found for BrC16HT against a human ovarian tumor (OVCAR-3) grown in SCID mice. IP treatments with BrC16HT against early or established IP-implanted OVCAR-3 tumor increased mean survival times more than treatment with Taxol. Long-term survivors were found only in groups treated with BrC16HT. Intravenously administered BrC16HT was more effective than Taxol against SC OVCAR-3 tumor. Early treatment (25 mg/kg x 5) completely inhibited tumor growth through 120 days after tumor implantation. Pharmacokinetic studies suggest that BrC16HT is slowly hydrolyzed to paclitaxel and circulates longer than paclitaxel from Taxol. Thus, BrC16HT may provide sustained levels of paclitaxel, which may contribute to the increased efficacy of BrC16HT compared to Taxol.
Subject(s)
Antineoplastic Agents, Phytogenic/therapeutic use , Ovarian Neoplasms/drug therapy , Paclitaxel/analogs & derivatives , Paclitaxel/therapeutic use , Animals , Antineoplastic Agents, Phytogenic/pharmacokinetics , Cell Survival , Drug Screening Assays, Antitumor , Female , Humans , Mice , Mice, SCID , Paclitaxel/pharmacokineticsABSTRACT
We have explored the structure-activity relationship (SAR) surrounding the clinically efficacious antiepileptic drug topiramate (1), a unique sugar sulfamate anticonvulsant that was discovered in our laboratories. Systematic structural modification of the parent compound was directed to identifying potent anticonvulsants with a long duration of action and a favorable neurotoxicity index. In this context, we have probed the pharmacological importance of several molecular features: (1) the sulfamate group (6-8, 22-25, 27, 84), (2) the linker between the sulfamate group and the pyran ring (9, 10, 21a,b), (3) the substituents on the 2,3- (58-60, 85, 86) and 4, 5-fused (30-38, 43, 45-47, 52, 53) 1,3-dioxolane rings, (4) the constitution of the 4,5-fused 1,3-dioxolane ring (2, 54, 55, 63-68, 76, 77, 80, 83a-r, 84-87, 90a, 91a, 93a), (5) the ring oxygen atoms (95, 96, 100-102, 104, 105), and (6) the absolute stereochemistry (106 and 107). We established the C1 configuration as R for the predominant alcohol diastereomer from the highly selective addition of methylmagnesium bromide to aldehyde 15 (16:1 ratio) by single-crystal X-ray analysis of the major diastereomer of sulfamate 21a. Details for the stereoselective syntheses of the hydrindane carbocyclic analogues 95, 96, 100, and 104 are presented. We also report the synthesis of cyclic imidosulfites 90a and 93a, and imidosulfate 91a, which are rare examples in the class of such five-membered-ring sulfur species. Imidosulfite 93a required the preparation and use of the novel sulfur dichloride reagent, BocN=SCl2. Our SAR investigation led to the impressive 4,5-cyclic sulfate analogue 2 (RWJ-37947), which exhibits potent anticonvulsant activity in the maximal electroshock seizure (MES) test (ca. 8 times greater than 1 in mice at 4 h, ED50 = 6.3 mg/kg; ca. 15 times greater than 1 in rats at 8 h, ED50 = 1.0 mg/kg) with a long duration of action (>24 h in mice and rats, po) and very low neurotoxicity (TD50 value of >1000 mg/kg at 2 h, po in mice). Cyclic sulfate 2, like topiramate and phenytoin, did not interfere with seizures induced by pentylenetetrazole, bicucculine, picrotoxin, and strychnine; also, 2 was not active in diverse in vitro receptor binding and uptake assays. However, 2 turned out to be a potent inhibitor of carbonic anhydrase from different rat tissue sources (e. g., IC50 of 84 nM for the blood enzyme and 21 nM for the brain enzyme). An examination of several analogues of 2 (83a-r, 85-87, 90a, 91a, 93a) indicated that potent anticonvulsant activity is associated with relatively small alkyl substituents on nitrogen (Me/H, 83a; Me/Me, 83m; Et/H, 83b; allyl/H, 83e; c-Pr/H, 83j; c-Bu/H, 83k) and with limited changes in the cyclic sulfate group, such as 4,5-cyclic sulfite 87a/b. The potent anticonvulsants 83a and 83j had greatly diminished carbonic anhydrase inhibitory activity; thus, inhibition of this enzyme may not be a significant factor in the anticonvulsant activity. The alpha-L-sorbopyranoses 67, 68, and 80, which mainly possess a skew conformation (ref 29), were nearly twice as potent as topiramate (1). The L-fructose enantiomers of 1 (106) and 2 (107), synthesized from L-sorbose, were found to have moderate anticonvulsant activity, with eudysmic ratios (MES ED50 in mice at 4 h, po) of 1:106 = 1.5 and 2:107 = 3.5. The log P values for 1 and 2 were determined experimentally to be 0.53 and 0.42, respectively, which are less than the optimal 2.0 for CNS active agents. However, analogues with more favorable calculated log P (clogP) values, in conjunction with just minor steric perturbation according to the developed SAR profile, such as 47 (clogP = 2.09), 83m (1.93), and 86 (1.50), did not display improved potency: 47 is less potent than 1, 83m is equipotent with 2, and 86 is less potent than 2. Although the measured log P value for diethyl analogue 31 is 1.52, this did not translate into enhanced potency relative to 1. (ABSTRACT TRUNCATED)
Subject(s)
Anticonvulsants , Fructose/analogs & derivatives , Sulfonic Acids , Animals , Anticonvulsants/chemistry , Anticonvulsants/pharmacology , Anticonvulsants/toxicity , Carbonic Anhydrase Inhibitors/chemistry , Carbonic Anhydrase Inhibitors/pharmacology , Carbonic Anhydrase Inhibitors/toxicity , Crystallography, X-Ray , Electroshock , Fructose/chemistry , Fructose/pharmacology , Fructose/toxicity , Mice , Molecular Conformation , Rats , Seizures/prevention & control , Stereoisomerism , Structure-Activity Relationship , Sulfonic Acids/chemistry , Sulfonic Acids/pharmacology , Sulfonic Acids/toxicity , TopiramateABSTRACT
The ether-lipid 1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphocholine (ET-18-OCH3) has anticancer activity, but systemic toxicity has restricted its therapeutic use. In this report "free" ET-18-OCH3 and a stable, well-characterized, liposome-based formulation of ET-18-OCH3 (ELL-12) were compared for in vivo toxicity in normal mice and for therapeutic efficacy in three mouse tumor model systems. The entrapment of ET-18-OCH3 in liposomes decreased the acute toxicity of ET-18-OCH3 after i.v. administration. The maximum tolerated dose for a single i.v. dose of free ET-18-OCH3 was found to be approximately 25 mg/kg, whereas the maximum tolerated dose for ELL-12 was approximately 200 mg/kg. ELL-12 was much less hemolytic in vivo than ET-18-OCH3. The therapeutic efficacy of free ET-18-OCH3 and ELL-12 was investigated against i.p. P388 leukemia, Lewis lung cancer lung metastases, and B16/F10 melanoma (lung tumor nodules) in mice. Although ET-18-OCH3 had some anticancer activity, it was found that ELL-12 was more effective than ET-18-OCH3 in all three tumor models at lower and nontoxic dose schedules. These results suggest that association of ET-18-OCH3 in stable, well-characterized liposomes transforms it into an effective antitumor agent.
Subject(s)
Antineoplastic Agents/administration & dosage , Phospholipid Ethers/administration & dosage , Animals , Antineoplastic Agents/toxicity , Ascitic Fluid/pathology , Carcinoma, Lewis Lung/drug therapy , Carcinoma, Lewis Lung/pathology , Drug Screening Assays, Antitumor , Female , Hemolysis , Leukemia P388/drug therapy , Leukemia P388/pathology , Liposomes , Melanoma, Experimental/drug therapy , Melanoma, Experimental/pathology , Mice , Mice, Inbred BALB C , Necrosis , Phospholipid Ethers/toxicityABSTRACT
N-Oxides of centrally acting analgesics generally have minimal analgesic activity. However, the N-oxide of tramadol produced dose-related, long-lasting antinociception in the mouse abdominal irritant, 48 degrees C hot-plate, 55 degrees C hot-plate, and tail-flick tests (ED50 = 15.5, 84.7, 316.4 and 138.2 mg/kg, p.o., respectively). Tramadol N-oxide (T-N-O) (RWJ 38705) was also antinociceptive in the 51 degrees C hot-plate test in male (ED50 = 63.2 mg/kg, i.p.) and female (ED50 = 39.9 mg/kg, i.p.) rats. A characteristic feature of T-N-O was an extended duration of action in these tests (4-5 h). T-N-O had negligible affinity for opioid mu (Ki = 38.5 microM) delta. or kappa receptors (Ki > 100 microM) and, in contrast to tramadol, was essentially devoid of norepinephrine or serotonin neuronal reuptake inhibitory activity (Ki > 100 microM). However, T-N-O displayed tramadol-like characteristics in vivo. There were also significant amounts of tramadol in plasma after T-N-O administration, and the levels resulting from equal oral doses of T-N-O and tramadol were the same, suggesting that the conversion of T-N-O to tramadol was rapid and essentially quantitative. T-N-O was not readily metabolized to tramadol in rat hepatic S9 fraction (< 2%), implying that the conversion might occur in the gastrointestinal tract. Taken together, the results suggest that T-N-O acts as a prodrug for tramadol. T-N-O could offer the clinical benefits of an extended duration of action and a "blunted" plasma concentration spike, possibly leading to an enhanced side-effect profile.
Subject(s)
Analgesics/pharmacology , Tramadol/analogs & derivatives , Tramadol/pharmacology , Animals , Biological Transport , Dose-Response Relationship, Drug , Female , Liver/metabolism , Male , Mice , Naloxone/pharmacology , Radioligand Assay , Rats , Rats, Wistar , Receptors, Opioid, mu/metabolism , Tramadol/administration & dosage , Tramadol/metabolism , Tramadol/pharmacokineticsABSTRACT
The behavioral response elicited in mice by an i.p. injection of endothelin-1 (ET-1) (0.1 mg/kg) was differentiated from that elicited by standard agents such as acetylcholine (ACh) (5.5 mg/kg) or phenyl-p-quinone (PpQ) (1.25 mg/kg). First, there was lack of two-way "cross-tolerance' between test paradigms. That is, at equieffective doses, a 60-min prior i.p. injection of ET-1 blocked the behavioral response to a subsequent i.p. injection of ET-1 or PpQ, but not of ACh, whereas a 60-min prior injection of ACh or of PpQ had no effect on a subsequent i.p. injection of ACh, PpQ or ET-1. Second, differential antagonism of ET-1-, ACh- or PpQ-induced responses was observed in an examination of 36 test compounds. For example, cyclo-oxygenase inhibitors such as indomethacin and ibuprofen did not block the ET-1-induced response at > 10 times the doses that blocked ACh- or PpQ-induced responses, whereas other compounds (such as certain benzodiazepines) inhibited ET-1-induced, but not ACh- or PpQ-induced, responses. These findings suggest that ET-1 produces a novel nociceptive stimulus, mechanistically distinct from ACh and PpQ. Hence, the ET-1-induced behavioral response in mice serves as a rapid and convenient measure of in vivo endothelin activity. In addition, this test might be a model for clinical pains not adequately treated by present analgesic agents or adequately tested by preclinical antinociceptive screens using ACh or PpQ. As such, it is a potentially valuable model for the identification of novel analgesic and other agents.
Subject(s)
Analgesia , Endothelins/pharmacology , Models, Neurological , Pain Measurement , Acetylcholine/pharmacology , Animals , Dose-Response Relationship, Drug , Indomethacin/pharmacology , Male , Mice , Mice, Inbred ICR , Morphine/pharmacologyABSTRACT
Endothelins (ET-1, ET-2 or ET-3) or endothelin precursors (big-ET-1[1-38], big-ET-2[1-37] or big-ET-3[1-41]) injected i.p. in mice have previously been shown to elicit a characteristic nociceptive behavioral response. In this study, we investigated the endothelin receptor type (ETA or ETB) that mediates this behavioral response. Mice were injected i.p. with ET-1, ET-2, ET-3, big-ET-1[1-38], big-ET-2[1-37], big-ET-3[1-41], sarafotoxin S6a, sarafotoxin S6b, sarafotoxin S6c, ET-1 with Ala substitutions for Cys3 and Cys11 or His-Leu-Asp-Ile-Ile-Trp, and quantal dose-response curves were obtained for each of the compounds (except the latter). Co-administration of enzyme inhibitors with the big-endothelins was used to establish the requisite conversion to endothelins and big-ET-1[22-38], big-ET-2[22-37] and ET-3[22-41] amide, and the ETA-selective antagonist cyclo[-D-Asp-Pro-D-Val-Leu-D-Trp-] was used to determine receptor specificity. The ED50 values were 2.9, 3.3 and 23.9 micrograms/kg i.p. for ET-1, ET-2 and ET-3, respectively, 0.6, 0.6 and 13.1 micrograms/kg i.p. for sarafotoxin S6a, sarafotoxin S6b and sarafotoxin S6c, respectively, and 5.3 micrograms/kg i.p. for ET-1 with Ala substitutions for Cys3 and Cys11. Big-ET-1[22-38], big-ET-2[22-37], big-ET-3[22-41] amide and ET-C produced less than 25% effect up to 2000 micrograms/kg. The big-ET-1-induced effects were blocked by the enzyme inhibitors phosphoramidon and thiorphan (ID50 = 0.9 mg/kg) but not by ubenimex (bestatin), captopril or perindopril. Cyclo[-D-Asp-Pro-D-Val-Leu-D-Trp-] blocked ET-1- and ET-2-induced effects but not ET-3-, ACh- or phenyl-p-quinone-induced effects. These results suggest that endothelin-induced nociceptive behavioral response in mice can be mediated via both ET receptor types, ETA and ETB. Further, the ET-1 carboxy-terminal hexapeptide is insufficient to produce the effect, and the Cys3-Cys11 disulfide bridge of ET-1 is not required.
Subject(s)
Endothelins/pharmacology , Pain/chemically induced , Receptors, Endothelin/physiology , Animals , Male , Mice , Mice, Inbred ICR , Peptide Fragments/pharmacology , Peptides, Cyclic/pharmacology , Receptor, Endothelin A , Receptor, Endothelin B , Viper Venoms/pharmacologyABSTRACT
Although it is well established that the analgesic effects of morphine are mediated by opioid receptors, previous studies have shown that some opioids additionally inhibit the uptake of serotonin and norepinephrine. The present investigation of a diverse group of opioids revealed that structurally identifiable subgroups inhibited the neuronal reuptake of these monoamines. Phenanthrene opioids with an oxygen bridge between C4 and C5, such as morphine and naloxone (group I), did not block norepinephrine or serotonin uptake, whereas phenanthrene opioids without the oxygen bridge and the C6-OH moiety, such as levorphanol and levomethorphan (group II), did inhibit uptake, as did nonphenanthrene opioids, such as d-propoxyphene and methadone (group III). Affinity at the mu opioid receptor correlated with antinociceptive potency (r = 0.87, P < .05). Although the antinociceptive activity of the "active enantiomers" of group II and III compounds also correlated with their affinity at the mu opioid receptor (r = 0.85, P = .007), additional consideration of serotonin uptake inhibiting activity (but not of norepinephrine uptake inhibiting activity) significantly improved the correlation between antinociceptive potency and the in vitro activity of these compounds (r = 0.915, P = .0017). Additionally, for group II and III (but not group I) compounds, smaller differences between enantiomers in antinociceptive potency than in mu receptor affinity were noted, presumably because of the contribution of uptake inhibition to the antinociceptive activity of group II and III compounds. Evidence also is provided suggesting a broader role for the combination of mu opioid affinity and 5-hydroxytryptamine uptake inhibition in the activity of other antinociceptive agents.
Subject(s)
Analgesics, Opioid/pharmacology , Neurotransmitter Uptake Inhibitors/pharmacology , Selective Serotonin Reuptake Inhibitors/pharmacology , Analgesics, Opioid/antagonists & inhibitors , Analgesics, Opioid/chemistry , Analgesics, Opioid/metabolism , Animals , Male , Mice , Naloxone/pharmacology , Narcotic Antagonists/pharmacology , Neurotransmitter Uptake Inhibitors/metabolism , Protein Binding , Rats , Rats, Wistar , Receptors, Opioid/metabolism , Selective Serotonin Reuptake Inhibitors/metabolism , Stereoisomerism , Structure-Activity RelationshipABSTRACT
Topiramate [TPM, 2,3:4,5-bis-O-(1-methylethylidene)-beta-D-fructopyranose sulfamate] (RWJ-17021-000, formerly McN-4853) is a structurally novel antiepileptic drug (AED). The preclinical anticonvulsant profile suggests that TPM acts primarily by blocking the spread of seizures. TPM was highly effective in the maximal electroshock (MES) seizure test in rats and mice. Activity was evident < or = 0.5 h after oral administration and lasted at least 16 h. The ED50 values 4 h after oral dosing were 13.5 and 40.9 mg/kg in rats and mice, respectively. TPM blocked pentylenetetrazol (PTZ)-induced clonic seizures at high doses in mice (ED50 = 1,030 mg/kg orally, p.o.). With motor incoordination and loss of righting reflex used as indicators of neurologic impairment, the neuroprotective index (TD50/MES ED50) for TPM was equivalent or superior to that of several approved AEDs. In mice pretreated with SKF-525A (a P450 enzyme inhibitor), the anticonvulsant potency was either increased or unaffected when TPM was tested 0.5, 1, or 2 h after i.p. administration, suggesting that TPM rather than a metabolite was the active agent. In mice pretreated with reserpine or tetrabenazine, the activity of TPM in the MES test was markedly reduced. TPM was inactive in a variety of receptor binding, neurotransmitter uptake, and ion channel tests. TPM weakly inhibited erythrocyte carbonic anhydrase (CA) activity. However, the anticonvulsant activity of TPM appears to differ mechanistically from that of acetazolamide.
Subject(s)
Anticonvulsants/pharmacology , Fructose/analogs & derivatives , Seizures/prevention & control , Animals , Drug Interactions , Electroshock , Fructose/pharmacology , Male , Mice , Molecular Structure , Pentylenetetrazole , Picrotoxin , Rats , Rats, Wistar , Reserpine/pharmacology , Seizures/chemically induced , Seizures/etiology , Tetrabenazine/pharmacology , TopiramateABSTRACT
The prevailing view is that supraspinal mu opioid-mediated antinociception in mice is mediated via the mu 1 subtype. The purpose of the present study was to determine if the highly mu-selective compound etonitazene could produce supraspinal (intracerebroventricular; i.c.v.) antinociception in CXBK mice, which are deficient in brain mu1, but not mu2, opioid receptors. CXBK or normal Crl:CD-1 (ICR)BR mice were administered graded doses of etonitazene i.c.v. and 15 min later antinociception was assessed by a standard radiant-heat or 55 degrees C water tail-flick test. Etonitazene produced dose-related antinociception that was blocked by naloxone and by beta-FNA (demonstrating a mu opioid mechanism), but not by either ICI-174,864 or naltrindole (demonstrating the lack of involvement of delta opioid receptors). These findings suggest that mu2 opioid receptors are important contributors to opioid-induced supraspinal antinociception in mice.
Subject(s)
Benzimidazoles/pharmacology , Cerebral Ventricles/physiology , Pain/physiopathology , Receptors, Opioid, mu/deficiency , Receptors, Opioid, mu/physiology , Spinal Cord/physiology , Animals , Benzimidazoles/administration & dosage , Cerebral Ventricles/drug effects , Dose-Response Relationship, Drug , Enkephalin, Leucine/administration & dosage , Enkephalin, Leucine/analogs & derivatives , Enkephalin, Leucine/pharmacology , Hot Temperature , Injections, Intraventricular , Injections, Subcutaneous , Male , Mice , Mice, Inbred ICR , Mice, Mutant Strains , Naloxone/administration & dosage , Naloxone/pharmacology , Naltrexone/administration & dosage , Naltrexone/analogs & derivatives , Naltrexone/pharmacology , Narcotic Antagonists/pharmacology , Spinal Cord/drug effectsABSTRACT
Morphine was administered intracerebroventricularly to normal or recombinant inbred CXBK (mu-opioid receptor deficient) mice and antinociception was determined against two different stimuli. Morphine-induced antinociception against acetylcholine was strain-dependent, whereas against endothelin-1 it was not. The antinociception was mediated via opioid mu receptors (blocked by beta-FNA, but not naltrindole, ICI 174,864 or nor-BNI) through separate pathways, one naloxonazine-sensitive and the other naloxonazine-insensitive. Taken together, these results appear to demonstrate supraspinal morphine-induced antinociception through distinct subtypes of the mu opioid receptor, supporting the possibility of novel subtype-selective therapeutic agents with greater separation between analgesia and side-effects or physical dependence. Furthermore, the methodology described herein provides model systems for the in vivo screening of such agents.
Subject(s)
Endothelins/pharmacology , Morphine/pharmacology , Nociceptors/drug effects , Receptors, Opioid, mu/antagonists & inhibitors , Receptors, Opioid, mu/physiology , Animals , Male , Mice , Mice, Inbred ICR , Receptors, Opioid, mu/classificationABSTRACT
Intracerebroventricular (i.c.v.) or intrathecal (i.t.) administration of morphine to mice antagonized the abdominal constriction induced by an i.p. injection of endothelin-1 (ET-1; 0.1 mg/kg). The ED50 values (95% confidence intervals) were 39.3 (16.5-80.2) ng and 1.5 (0.8-4.9) ng, respectively. The antagonism of ET-1-induced abdominal constriction by morphine was blocked by naloxone (1.0 mg/kg, s.c.) or by 24 h pretreatment with beta-funaltrexamine (beta-FNA; 8.84 micrograms, i.c.v.). These results demonstrate for the first time that the stimulus resulting from an i.p. injection of ET-1 is transmitted via ascending (pain) pathways that are subject to attenuation by opioid (mu) receptor activation. Hence, ET-1-induced abdominal constriction is a new pain model which, given the other pharmacology of ET-1, might represent a unique model with potential specific utility for anginal or other visceral pain.
Subject(s)
Endothelins/pharmacology , Pain Measurement , Pain/drug therapy , Animals , Endothelins/therapeutic use , Male , Mice , Morphine/pharmacology , Naloxone/pharmacology , Naltrexone/analogs & derivatives , Naltrexone/pharmacologyABSTRACT
Suprofen is a new potent, orally effective non-narcotic analgesic agent having a potent inhibitory action on prostaglandin (PG) biosynthesis. Recent experiments have shown that suprofen inhibits uterine hyperactivity induced by the physiological substances, arachidonic acid, bradykinin (BK) and PGF2 alpha. The present study explores the possibility that the analgesic activity of suprofen may involve multiple mechanisms of interaction with PGs, inhibiting synthesis at low doses and with higher doses possibly directly interacting with PGs and other physiological mediators of nociception at a common site. Experiments in mice have shown that suprofen antagonizes abdominal stretching induced by the physiological precursor of PG release, arachidonic acid (ED50 = 0.07 mg/kg, p.o.), and by the nociceptive agents acetylcholine (ACh) (ED50 = 1.7 mg/kg, p.o.), BK (ED50 = 65 mg/kg, p.o.) acetic acid (HAC) (H+ ion; ED50 = 4.6 mg/kg, p.o.), and PGE2, itself (ED50 = 20.2 mg/kg, i.p.). In rabbits, i.a. administered suprofen (ED50 = 0.98 mg/kg) blocked the reflex discharge of spinal sensory neurons evoked by BK (2 to 8 micrograms, i.a.). The analgesic activity of suprofen may involve multiple mechanisms of interaction with PGs and other mediators, including BK; suprofen blocks the nociceptive actions of PGs by inhibiting their formation, via the cyclooxygenase pathway, and possibly at PG sites of action, probably at peripheral nerve endings.