Human beta3 adrenergic receptor agonists containing cyanoguanidine and nitroethylenediamine moieties.

Pyridineethanolamine derivatives containing cyanoguanidine or nitroethylenediamine moieties were examined as human beta3 adrenergic receptor (AR) agonists. Notably, indoline derivatives 6a and 11 were potent beta3 AR agonists (beta3 EC50 = 13 and 19 nM, respectively), which showed good selectivity over binding to and minimal activation of the beta1 and beta2 ARs.

Tetrahydroisoquinoline derivatives containing a benzenesulfonamide moiety as potent, selective human beta3 adrenergic receptor agonists.

Tetrahydroisoquinoline derivatives containing a 4-(hexylureido)benzenesulfonamide were examined as human beta3 adrenergic receptor (AR) agonists. Notably, 4,4-biphenyl derivative 9 was a 6 nM full agonist of the beta3 AR. Naphthyloxy compound 18 (beta3 EC50 = 78 nM) did not activate the beta1 and beta2 ARs at 10 microM, and showed >1000-fold selectivity over binding to the beta1 and beta2 ARs.

Human beta3-adrenergic receptor agonists containing 1,2,3-triazole-substituted benzenesulfonamides.

Compounds containing a 1,2,3-triazole-substituted benzenesulfonamide were prepared and found to be potent and selective human beta3-adrenergic receptor agonists. The most interesting compound, trifluoromethylbenzyl analogue 12e (beta3 EC50 = 3.1 nM with >1500-fold selectivity over binding to both beta1- and beta2 receptors), stimulates lipolysis in the rhesus monkey (ED50 = 0.36 mg/kg) and is 25% orally bioavailable in the dog.

Effects of a novel fentanyl derivative on drug discrimination and learning in rhesus monkeys.

Three monkeys discriminated 1.78 mg/kg of mirfentanil while responding under a fixed-ratio 5 schedule of stimulus-shock termination. Two mirfentanil derivatives, OHM3295 and OHM10579, substituted for mirfentanil in all subjects. However, other drugs produced variable effects among monkeys; for example, mu and kappa opioid agonists and clonidine substituted for mirfentanil on some occasions in two monkeys. Cocaine, amphetamine, and ketamine did not substitute in any subject. Opioid antagonists did not attenuate the effects of mirfentanil. In monkeys responding under a repeated acquisition and performance procedure, errors increased only during the acquisition phase at doses of mirfentanil that decreased response rates. Thus, unlike fentanyl, the discriminative stimulus effects of mirfentanil do not appear to be mediated exclusively through opioid receptors. Finally, mirfentanil does not appear to disrupt complex behavioral processes.

Human beta3 adrenergic receptor agonists containing imidazolidinone and imidazolone benzenesulfonamides.

The cyclopentylpropylimidazolidinone L-766,892 is a potent beta3 AR agonist (EC50 5.7 nM, 64% activation) with 420- and 130-fold selectivity over binding to the beta1 and beta2 ARs, respectively. In anesthetized rhesus monkeys, L-766,892 elicited dose-dependent hyperglycerolemia (ED50 0.1 mg/kg) with minimal effects on heart rate.

Daily mirfentanil induces (cross-) tolerance to the rate-decreasing effects of morphine and not mirfentanil.

The fentanyl derivative mirfentanil has a novel set of behavioral effects in non-humans including low-efficacy opioid actions and non-opioid antinociceptive actions. This study evaluated the rate-decreasing effects of mirfentanil, morphine, naltrexone and ketamine in pigeons both prior to and during a period of chronic treatment with mirfentanil (3.2-17.8 mg/kg/day). Daily treatment with mirfentanil did not modify the rate-decreasing effects of mirfentanil or ketamine; however, daily treatment decreased sensitivity to the rate-decreasing effects of morphine and increased sensitivity to naltrexone. These results demonstrate a lack of tolerance to an apparently non-opioid action (rate-decreasing effect) of mirfentanil, which might predict a lack of tolerance to the non-opioid antinociceptive actions of this compound. These results further indicate that cross-tolerance (to morphine) and dependence (increased sensitivity to naltrexone) can occur in the absence of tolerance (to mirfentanil).

Pharmacological profile of a deuterium-substituted mirfentanil derivative, OHM10579, in rhesus monkeys.

The discriminative-stimulus, respiratory, and antinociceptive effects of OHM10579, an isotopic isomer of mirfentanil, were characterized in rhesus monkeys. In monkeys discriminating nalbuphine, 0.32 mg/kg of OHM10579 partially substituted for nalbuphine. In monkeys treated daily with 3.2 mg/kg of morphine and discriminating 0.01 mg/kg of naltrexone, 0.32 mg/kg of OHM10579 substituted for naltrexone. In morphine-abstinent monkeys, morphine reversed naltrexone-lever responding, an effect attenuated by OHM10579. The shift to the right in the morphine dose-effect curve was greater 2 h after 0.32 mg/kg of OHM10579 compared to 0.32 mg/kg of mirfentanil, indicating that OHM10579 has a longer duration of action than mirfentanil. In a warm-water tail-withdrawal procedure, 10 and 17.8 mg/kg of OHM10579 had antinociceptive effects that were not antagonized by naltrexone. Morphine decreased breathing in air to 48%, whereas the maximal decrease with OHM10579 was to 75% of control. OHM10579 attenuated hyperventilation induced by 5% CO2 and partially antagonized the respiratory-depressant effects of morphine. OHM10579 can be classified as a low-efficacy mu-opioid agonist with some nonopioid actions. These results indicate that the pharmacology of the mirfentanil isotope OHM10579 is similar to that of mirfentanil, but that OHM10579 might have a longer duration of action.

The rate-decreasing effects of fentanyl derivatives in pigeons before, during and after chronic morphine treatment.

Mirfentanil is a fentanyl derivative with non-opioid actions, including non-opioid antinociceptive effects in rhesus monkeys. The current study examined the rate-altering effects of mirfentanil and several other compounds in pigeons to assess: 1) the opioid and non-opioid actions of acutely-administered fentanyl derivatives; and 2) the development of cross-tolerance between each of these compounds and morphine. Seven pigeons responded under a fixed-ratio 20 (FR20) schedule of food delivery. In untreated pigeons, fentanyl, morphine, naltrexone, ketamine and three fentanyl derivatives (mirfentanil, OHM3463 and OHM3295) decreased rates of key pecking in a dose-related manner. Naltrexone (0.1-1.0 mg/kg) attenuated the effects of OHM3463 and not mirfentanil or OHM3295, suggesting non-opioid mediation of the rate-decreasing effects for the latter two fentanyl derivatives. Subjects were treated daily with morphine for 9 weeks, up to a dose of 100 mg/kg per day, during which time the dose-effect curves for morphine, fentanyl and OHM3463 shifted rightward 6-, 10- and 2-fold, respectively, indicating the development of tolerance to morphine and cross-tolerance to fentanyl and OHM3463. Dose-effect curves for ketamine, OHM3295 and mirfentanil were not shifted to the right during morphine treatment, and the dose-effect curve for naltrexone was shifted leftward 180-fold. To the extent that rate-decreasing effects are predictive of antinociceptive effects, these data suggest that some fentanyl derivatives might be useful therapeutics under conditions where tolerance develops to morphine-like opioids.

Behavioral effects and binding affinities of the fentanyl derivative OHM3507.

Several fentanyl derivatives have been reported to have novel pharmacologies that might be exploited for developing alternate approaches to the treatment of pain. The purpose of the current series of studies was to evaluate OHM3507, a novel fentanyl derivative reported to have an unusual pharmacological profile in nonprimate species. Similar to several other fentanyl derivatives with clinical potential, OHM3507 had the highest affinity (IC50 = 10 nM) for mu ([3H]D-Ala2,N-Me-Phe4,Gly5-OH-labeled) receptors with 6- and 176-fold lower affinity for delta ([3H]D-Pen2-D-Pen5-labeled), and kappa ([3H]ethylketocyclazocine-labeled) receptors, respectively. In rhesus monkeys, OHM3507 shared discriminative stimulus effects with morphine, increased tail-withdrawal latencies in a warm-water procedure of antinociception, decreased ventilation in monkeys breathing normal air or 5% CO2, and failed to modify accuracy on acquisition and performance tasks up to doses that decreased rates of food-maintained responding. The opioid antagonists naltrexone and naltrindole antagonized the behavioral effects of OHM3507 in a manner that was consistent with mu-receptor mediation. Although OHM3507 appeared to have low efficacy opioid actions in nonprimate species, results from the current studies clearly show this compound to have strong, fentanyl-like mu agonist actions in rhesus monkeys. These results provide another example of the sometimes poor predictability in the behavioral pharmacology of fentanyl derivatives among species, in this case between monkeys and rats, mice and rabbits, and demonstrates the need for evaluating new drugs under a broad range of conditions to increase the probability of identifying novel compounds that can be used to treat pain.

Mirfentanil antagonizes morphine-induced suppression of splenic NK activity in mice.

Mirfentanil [N-(2-pyrazinyl)-N-(1-phenethyl-4-piperidinyl)-2-furamide] was studied for its antinociceptive and immunomodulatory effects in mice Mirfentanil (1.0-32.0 mg/kg) increased tail-flick latency to a thermal stimulus and this effect was antagonized (94 +/- 2%) by naltrexone (10.0 mg/kg). Unlike naltrexone, the delta opioid selective antagonist naltrindole (20.0 mg/kg) had no effect on mirfentanil-induced analgesia. In a dose-dependent fashion, the mu-selective antagonists beta-funaltrexamine (1.0-40.0 mg/kg) and naloxonazine (1.0-35.0 mg/kg) blocked mirfentanil (10.0 mg/kg)-induced analgesia up to 75% of the maximum analgesic effect. Norbinaltorphimine (10.0 mg/kg) partially blocked (35%) the maximum analgesic effect following mirfentanil (10.0 mg/kg) administration. Single doses of mirfentanil (0.1-32.0 mg/kg) had no effect on splenic NK activity. However, preadministration of mirfentanil (1.0-10.0 mg/kg) blocked morphine-induced suppression of splenic NK activity. Collectively, the results suggest that mirfentanil is a novel opioid that induces antinociception predominately through mu opioid receptors but, unlike morphine or fentanyl, does not suppress splenic NK activity.

Fentanyl-related 4-heteroanilido piperidine OHM3295 augments splenic natural killer activity and induces analgesia through opioid receptor pathways.

Recently, the fentanyl-related compound OHM3295 has been shown to induce a naltrexone-sensitive, dose-related analgesia in CD1 mice. However, unlike morphine or fentanyl, which are potent immunosuppressive drugs, OHM3295 has been found to augment splenic natural killer (NK) activity in a dose-related and naltrexone-reversible manner. The present study investigated the type (delta, kappa or mu) of opioid receptor involved in analgesia and immunomodulation after acute administration of OHM3295. CD1 mice pretreated with beta-funaltrexamine (beta-FNA, 40.0 mg/kg) showed an insignificant induction of analgesia (8.4 +/- 3.7%) after 3.2 mg/kg OHM3295, whereas mice pretreated with vehicle, norbinaltorphimine (10.0 mg/kg) or naltrindole (20.0 mg/kg) exhibited 43.6 +/- 12.6% of maximal analgesia, as determined by the tail-flick latency test. Consistent with previous results, acute administration of OHM3295 (3.2 mg/kg) augmented splenic NK activity (20.7 +/- 3.4 lytic units [LU]) relative to vehicle-treated mice (8.2 +/- 0.7 LU). Pretreatment with beta-FNA (40.0 mg/kg) completely blocked (9.0 +/- 1.9 LU) OHM3295-mediated augmentation of NK activity, whereas pretreatment with norbinaltorphimine (10.0 mg/kg) partially blocked (15.8 +/- 2.2 LU) the drug-induced effect. However, pretreatment with naltrindole (20.0 mg/kg) did not antagonize OHM3295-induced increases in splenic NK activity but rather further enhanced (32.3 +/- 4.2 LU) the effect. NK-enriched effector cells from OHM3295-treated mice displayed an increase in conjugation with YAC-1 target cells, an increase in the percent killing of target cells and a significant increase in the number of active killer cells compared with NK-enriched effector cells from vehicle-treated mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral effects and receptor binding affinities of fentanyl derivatives in rhesus monkeys.

These studies examined the opioid receptor binding affinities and behavioral effects of several fentanyl derivatives in rhesus monkeys. OHM3295, OHM3296, OHM3326 and OHM3463 displayed high affinity for mu (IC50 = 7-66 nM) as compared to kappa (IC50 = 263-3255 nM) or delta (IC50 = 480-4500 nM) receptors as measured by their ability to displace [3H](D-Ala2-Me-Phe4,Glyol5)enkephalin, [3H](5,7,8[beta])-N-[2- (1-pyrrolidinyl)1-oxaspiro[4,5]dec-8-yl]benzeneacetamide and [3H](D-Pen2-D-Pen5)enkephalin, respectively. All four compounds maintained i.v. self-administration responding at rates above those maintained by the mu agonist alfentanil. In drug discrimination studies, OHM3463, OHM3326 and OHM3296 substituted completely for nalbuphine whereas OHM3295, and a related compound, mirfentanil, substituted partially for nalbuphine. In morphine-treated monkeys, OHM3295 substituted for naltrexone; in monkeys acutely deprived of morphine, only OHM3463 reversed naltrexone-lever responding. All four compounds had antinociceptive effects, although the extent to which these effects were accompanied by respiratory depression or modified by naltrexone, as well as the interactions between antinociceptive effects of fentanyl derivatives and alfentanil, varied markedly among compounds. Thus, OHM3463 shared effects with mu agonists (e.g., alfentanil) under all conditions; the other three compounds had opioid agonist effects under only a subset of conditions. Moreover, one of these compounds (OHM3295) antagonized the discriminative stimulus and antinociceptive effects of other mu agonists. Collectively, these compounds appear to vary on two dimensions: opioid efficacy and the contribution of nonopioid actions to their antinociceptive effects. Together with results obtained with other fentanyl derivatives (mirfentanil) under similar conditions, results of the current study suggest this chemical class might be especially fertile for the development of novel analgesics that might have reduced toxicity and abuse liability as compared to fentanyl and related compounds that are currently used in medicine.

OHM3295: a fentanyl-related 4-heteroanilido piperidine with analgesic effects but not suppressive effects on splenic NK activity in mice.

The immunoregulatory effects of fentanyl and a fentanyl-related compound, OHM3295, were studied in mice. Male CD1 mice treated with a range of fentanyl doses (0.1-1.0 mg/kg, subcutaneously) showed suppression of splenic natural killer (NK) activity following 0.25-0.50 mg/kg fentanyl dose but not higher (0.75-1.0 mg/kg) or lower (0.1 mg/kg) doses. Fentanyl (0.01-32.0 mg/kg) also induced dose-related analgesia as measured by an increase in tail flick latency; these analgesic effects were antagonized by naltrexone (1.0-10.0 mg/kg). Pretreatment with naltrexone (1.0-3.2 mg/kg) resulted in significant suppression of splenic NK activity following fentanyl (10.0-32.0 mg/kg) administration. In comparison to fentanyl, OHM3295 (3.2-25.0 mg/kg) augmented splenic NK activity in a naltrexone-reversible manner. Similar to fentanyl, OHM3295 (1.0-32.0 mg/kg) also induced a naltrexone-sensitive, dose-related analgesia as measured by an increase in tail flick latency. These results with OHM3295 demonstrate a novel profile of effects which includes naltrexone-sensitive analgesic effects in the absence of immunosuppressive effects. In addition, this is the first reported case in which a compound with opioid analgesic effects has been shown to potentiate natural killer cytolytic activity following in vivo administration.