Patrick J. Little

Stereochemical effects of 11-OH-Δ8-THC-dimethylheptyl in mice and dogs ☆

Abstract The effects of the enantiomers of 11-hydroxy- Δ 8 -tetrahydrocannabinol-dimethylheptyl (11-OH- Δ 8 -THC-DMH) on spontaneous activity, rectal temperature, tail-flick latency, and catalepsy were studied in mice and in the dog static-ataxia model to determine the relative potency of each enantiomer. The (−)-enantiomer was active in all tests between 3–100 μg/kg, while the (+)-enantiomer was inactive at 30 mg/kg in the mouse and 1 mg/kg in the dog. The (−)-enantiomer was 100–800 times more potent than Δ 9 -THC in the mouse. The high degree of enantioselectivity and potency are suggestive of an interaction at a specific site such as a receptor.

Potent, Orally Bioavailable Delta Opioid Receptor Agonists for the Treatment of Pain : Discovery of N,N-Diethyl-4-(5-hydroxyspiro-[chromene-2,4'-piperidine]-4-yl)benzamide (ADL5859)

Selective delta opioid receptor agonists are promising potential therapeutic agents for the treatment of various types of pain conditions. A spirocyclic derivative was identified as a promising hit through screening. Subsequent lead optimization identified compound 20 (ADL5859) as a potent, selective, and orally bioavailable delta agonist. Compound 20 was selected as a clinical candidate for the treatment of pain.

Spirocyclic Delta Opioid Receptor Agonists for the Treatment of Pain: Discovery of N,N-Diethyl-3-hydroxy-4-(spiro[chromene-2,4'-piperidine]-4-yl) Benzamide (ADL5747)

Selective, nonpeptidic delta opioid receptor agonists have been the subject of great interest as potential novel analgesic agents. The discoveries of BW373U86 (1) and SNC80 (2) contributed to the rapid expansion of research in this field. However, poor drug-like properties and low therapeutic indices have prevented clinical evaluation of these agents. Doses of 1 and 2 similar to those required for analgesic activity produce convulsions in rodents and nonhuman primates. Recently, we described a novel series of potent, selective, and orally bioavailable delta opioid receptor agonists. The lead derivative, ADL5859 (4), is currently in phase II proof-of-concept studies for the management of pain. Further structure activity relationship exploration has led to the discovery of ADL5747 (36), which is approximately 50-fold more potent than 4 in an animal model of inflammatory pain. On the basis of its favorable efficacy, safety, and pharmacokinetic profile, 36 was selected as a clinical candidate for the treatment of pain.

Relationship between the biodisposition of [3H]soman and its pharmacological effects in mice.

The iv administration of soman (25 micrograms/kg) resulted in inhibition of cholinesterase activity in plasma, brain, and diaphragm, as well as depression of spontaneous activity and rectal temperature in mice. The motor activity and rectal temperature of these animals had returned to control levels within 24 hr, but cholinesterase activity was not fully recovered after 3 days. Following iv administration of [3H]soman (25 micrograms/kg), only trace quantities of [3H]soman were found in all tissues as early as 1 min after injection. Almost half of the injected material was present in the form of free [3H]pinacolylmethylphosphoric acid (PMPA) within 1 min of injection of [3H]soman. The concentrations of [3H]PMPA fell by more than 50% by 1 hr. High concentrations of covalently bound [3H]PMPA were present in all tissues immediately after [3H]soman treatment, particularly in lungs, heart, and kidneys. These concentrations declined slowly and after 8 hr, the quantities of bound [3H]PMPA in most tissues had fallen by less than 50%. The radioactivity in brain was identified as bound and free [3H]PMPA, nonextractable radioactivity (presumably [3H]methylphosphonic acid), and only traces of [3H]soman. It appears that phosphorylation of cholinesterase in the central nervous system is not solely responsible for depression of motor activity and rectal temperature.

The Effect of MDMA ("Ecstasy") and Its Optical Isomers on Schedule-Controlled Responding in Mice

Eleven mice were trained to respond under an FR 20 schedule of reinforcement and, after learning the schedule, were administered doses of saline and the following phenylisopropylamines: (+/-)-MDMA, S(+)-MDMA, R(-)-MDMA and (+)-amphetamine. Each of the phenylisopropylamines decreased rates of operant responding in a dose-dependent manner. S(+)-MDMA (ED50 = 3.1 mg/kg) was nearly equipotent with racemic MDMA and four times more potent than R(-)-MDMA (ED50 = 4.1 and 11.6 mg/kg, respectively), but less potent than (+)-amphetamine (ED50 = 0.74 mg/kg). The present study constitutes the first enantiomeric behavioral-potency comparison for the optical isomers of MDMA.

Tissue disposition of [3H]sarin and its metabolites in mice

The biodisposition and metabolic fate of [3H]sarin was investigated in mice after iv administration of a sublethal dose (80 micrograms/kg). Within 1 min of administration, all tissues contained substantial quantities of radioactivity of which less than 10% represented [3H]sarin. The major portion of radioactivity corresponded to free [3H]isopropyl methylphosphonic acid (IMPA), the pharmacologically inactive hydrolytic product of [3H]sarin. Somewhat lesser quantities were present as bound [3H]IMPA which resulted from phosphorylation of protein. Plasma contained high concentrations of bound [3H]IMPA, consistent with sarins very reactive nature, which were sustained throughout the time course. Plasma concentrations of free [3H]IMPA diminished rather quickly. The high concentrations of metabolites in kidneys implied that this organ played a major role in the detoxification and excretion of [3H]sarin. Large quantities of free and bound [3H]IMPA were also found in lung which suggested an important site for toxicity. Only trace quantities of [3H]sarin were found in brain after 15 min. The major portion of radioactivity was present as either free and bound [3H]IMPA or as nonextractable material which presumably was [3H]methylphosphonic acid. Examination of the time course of sarin-induced motor hypoactivity and hypothermia revealed an immediate onset of action that lasted for 24 hr. However, substantial quantities of bound [3H]IMPA remained in brain at 24 hr which suggested that only a small portion of phosphorylation in brain accounted for these pharmacological effects.

The effects of Δ9-tetrahydrocannabinol and other cannabinoids on cAMP accumulation in synaptosomes

The effects of delta 9-THC and other cannabinoids on cAMP levels in synaptosomes from mouse brains were investigated in order to determine whether cannabinoids produced their behavioral effects through alterations in adenylate cyclase. delta 9-THC (0.01-10 microM) did not significantly alter basal cAMP levels, whereas delta 9-THC and other cannabinoids were able to alter forskolin-stimulated cAMP levels in synaptosomes. In general, three kinds of responses were observed. Some cannabinoids displayed a modest, concentration-dependent decrease in cAMP levels, producing significant inhibition between 1-10 microM. Other cannabinoids, including delta 9-THC and delta 8-THC, appeared to produce a biphasic effect in that inhibition of cAMP was observed only at a single concentration. Finally, some analogs were unable to significantly alter forskolin-stimulated cAMP. There was not a clear relationship between the ability of the cannabinoids to alter cAMP levels in synaptosomes and the behavioral effects observed in mice. However, it was demonstrated that the analogs which are the most potent in producing cannabimimetic effects in mice were the analogs which inhibited cAMP in a concentration-dependent manner. While cannabinoids were able to alter cAMP levels in synaptosomes, the ability to alter cAMP levels does not appear to be absolutely necessary for the production of cannabinoid effects in mice.

Relationship between the pharmacological effects and the biodisposition of [3H]diisopropylfluorophosphate in mice after inhalation

The biodisposition of [3H]diisopropylfluorophosphate (DFP) and its metabolites was studied in mice after inhalation administration. In addition, the time course of DFP-induced cholinesterase inhibition in selected tissues, hypothermia, and motor coordination were studied to determine a possible correlation with [3H]DFP, or its metabolites. The time course of tissue concentrations of [3H]DFP showed that [3H]DFP rapidly penetrated all tissues and was quickly hydrolyzed to [3H]diisopropylphosphoric acid (free [3H]DIP) or was covalently bound to tissue (bound [3H]DIP). By 1 hr, the greater portion of the radioactivity was in the form of bound [3H]DIP. Cholinesterase inhibition in brain, lung, diaphragm, and plasma was temporally related to concentrations of bound [3H]DIP between 5 min and 1 day, except at early time points for the lung. Motor incoordination (rotarod test) produced by DFP exposure had a rapid onset, with complete recovery by 10 hr. DFP-induced hypothermia (rectal temperature) had a very similar time-course profile to that of motor incoordination. The time course of hypothermia and motor incoordination was correlated with neither free [3H]DFP nor bound [3H]DIP concentrations in the brain, nor with cholinesterase inhibition in brain. These findings suggest that non-cholinesterase bound [3H]DIP may contribute to the depression of these centrally mediated effects.

Synthesis and pharmacological evaluation of mercapto and thioacetyl analogues of cannabidiol and Δ8-tetrahydrocannabinol

Abstract A series of novel mercapto and thioacetyl derivatives of Δ 8 -tetrahydrocannabinol ( Δ 8 -THC, 5 ), and cannabidiol ( 1 ) were synthesized. Treatment of 10-hydroxy-cannabidiol ( 2 ) with thioacetic acid in the presence of a complex of diisopropylazodicarboxylate and triphenylphosphine in dry THF gave 10-thioacetyl-cannabidiol ( 3 ). Further treatment with LiAlH 4 converted 3 into 10-mercapto-cannabidiol ( 4 ). Using a similar sequence, 11-mercapto- Δ 8 -THC ( 8 ) was synthesized from the metabolite 11-hydroxy- Δ 8 -THC ( 6 ) via the corresponding thioacetyl derivative ( 7 ). Similarly, the 12β-thioacetyl derivative ( 10 ) of Δ 8 -THC was prepared. Although 8 is a derivative of a pharmacologically active cannabinoid ( 6 ), 8 proved to be inactive in 4 different pharmacological evaluations in the mouse. Similarly, 10 and 4 were also inactive. Additionally, 7 was inactive except for the production of hypothermia, but was more than 3-fold less potent than Δ 8 -THC. None of these cannabinoids was able to antagonize the effects of Δ 9 -THC. These data indicate that there are specific structural requirements for the production of cannabimimetic activity, which tends to suggest that activity is determined, in part, via specific molecular interactions such as those observed in receptor-, enzyme-, ion channel-, or other protein-mediated events.