1

SOFT DRUG APPROACH IN CANNABINOIDS

Thesis presented

By

Jimit Girish Raghav

To

The Bouve’ Graduate School of Health Sciences

In Partial Fulfilment of the Requirements for the Degree of Master of Science

In Pharmaceutical Sciences with specialization in Pharmacology

NORTHEASTERN UNIVERSITY

BOSTON, MASSACHUSETTS

14th, August, 2014

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Northeastern University

Bouve College of Health Sciences

Thesis Approval

Thesis Title: Soft drug approach in cannabinoids.

Author: Jimit Girish Raghav.

Program: Pharmacology.

Approval for thesis requirements for the Master of Science degree in: Pharmacology

Thesis Committee (Chairman): Dr. Torbjorn Jarbe Date: 08/ 14/2014.

Other Committee members

Dr. David Janero Date: 08/14 /2014.

Dr. Rajeev Desai Date: 08/14 /2014.

Dean of the Bouve College of Health Sciences:

Dr. Tom Olson DATE: .

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4 Table of Contents

Page

List of figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

ACKNOWLEDGEMENTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

ABSTARCT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

i. STATEMENT OF THE PROBLEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

ii. BACKGROUND AND SIGNIFICANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

MATERIALS AND METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

SUMMARY AND DISCUSSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

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List of figures:

Figure1: Chemical structures of all the drugs used in the project . . . . . . . . . 8

Figure 2: Classification of drugs used in this project . . . . . . . . . . . . . . . . . . . . . 8

Figure 3: Overview of metabolic pathway of drugs used in this project . . . . . . 9

Figure 4: Overview of tail-flick latency analgesia assay . . . . . . . . . . . . . . . . . . . . 13, 14

Figure 5 a& b: Tail-flick latency data for drug AM7410 and (-) - ∆8- THC DMH. 14, 15

Figure 6: Tail-flick latency data for drug AM7438 and AM7410 . . . . . . . . . . . . . 16

Figure 7: Dose response curve for drug AM7438 . . . . . . . . . . . . . . . . . . . . . . . . . . 17

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ACKNOWLEDGEMENTS

I would like to take this opportunity and thanks Dr Torbjorn Jarbe, who is my PI and the advisor for the current

thesis. Without your vital support and belief I would have never been able to complete this project. I also express

my deepest gratitude to Dr. David Janero and Dr. Rajeev Desai for being on my committee, your crucial

suggestions, corrections and comments on my project were invaluable. I would also like to offer special thanks to

Dr. Alexandros Makriyannis for his indispensable support he gave me on all my projects here at CDD. I will also

like to appreciate Dr. Spiros Nikas for providing me with all the test molecules without any hesitation for this

project. I would also like to thanks Dr. Kiran Vemuri for guiding me on my research. Last but not least I will like to

thanks Roger Gifford my colleague/supervisor in lab who trained me initially on all the assays and helped me

acclimatized with the lab environment. My heartfelt to thanks my parents; it was their support and nurture

which made me help accomplishing everything in life. A special appreciation to National Institute of Drug Abuse

(NIDA) for providing all the monetary requirements via grants to support all the research done in this project.

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Abstract: The only plant-derived cannabinoid (phytocannabinoid) agent currently used for medical purposes in

the USA is (-) - ∆9- tetrahydrocannabinol (THC). Here, I report the analgesic effects of two novel synthetic

cannabinergic agents, AM7410 and AM7438 which are designed to be “soft-drugs”. Both drugs have

metabolically labile ester groups strategically placed in their chemical structure. This ester group makes AM7410

and AM7438 susceptible to degradation to inactive metabolites by plasma esterases. Both compounds profiled in

this thesis are analogues of (-) - ∆8- THC DMH (AM 10808; DMH = dimethylheptyl). The in vivo data demonstrate

that both AM7410 and AM7438 produce maximal analgesia (1 mg/kg) in a tail-flick withdrawal assay. Both AM

7410 and AM7438 (0.3 mg/kg and 1 mg/kg) showed quick onset and offset of action when compared to (-) - ∆8 -

THC DMH (0.3mg/kg and 1mg.kg). Additionally, data also suggest that the effects induced by AM 7438 (0.3 mg/kg

and 1 mg/kg) have a faster offset when compared to AM7410 (0.3 mg/kg and 1 mg/kg) in the tail-flick assay.

Introduction:

A: Statement of Problem: The aim of this thesis is to evaluate the concept of the “soft-drug” approach in the

field of cannabinoid chemistry/synthesis. The “soft-drug” approach has not yet been extensively analysed in the

cannabinoid field whereas it is a well-established concept in other medicinal chemistry fields such as opioids and

anti-hypertensives.1 A compound is considered to be a “soft drug” if the compound is an analogue of an parent

compound and the analogue has a more predictable and controlled metabolism compared to its parent

compound. A compound can also be labelled as a “soft drug” if the given compound has minimal side effects

when compared with its parent compound.2 In the former case, the analog is synthesised to be a soft drug by

introducing a certain chemical group or certain chemical modification into the structure of the analog which will

make the drug more susceptible to metabolic degradation by enzyme(s).2 One of the most common chemical

modifications employed to generate a soft drug is the introduction of an ester moiety into the parent compound

in an attempt to make the parent compound susceptible to enzymatic inactivation by (plasma) esterases. The

work carried out and presented in this thesis will focus on exploring the above concept for two cannabimimetic

agents. In this current paper the concept of “depot effect” will be discussed along with the concept of “soft-

drug”. The depot effect is typically observed with lipophilic drugs. Drugs with high lipophilicity tend to sequester

into fat tissue before flowing into the systemic circulation and to produce their pharmacological effect. The

8 “depot effect” mainly depends on the log P and topological polar surface area (tPSA) values of the molecules.

Both logP and tPSA are indices of a drug’s lipophilicity and its cell membrane permeability.3 The higher the logP

value of a compound, the higher the lipophilicity. The higher the lipophilicity, the higher the chances that the

compound will get distributed into fat tissues and hence the more likely is the compound’s ability to produce the

depot effect.3 If one is to follow the Lipinski’s rule of five which is set of rules that determines the ability of a test

compound to be used as orally available drug for future consumption by humans.4 According to this rule, the

logP of the compound should be 5 or less to avoid the distribution or sequestration into fat tissues and qualify as

a lead compound for potential human consumption.4

By introducing an ester group in the structures of AM7410 and AM7438 (Fig 1) the polarity (clogP values for

AM7410 and AM7438 are 6.59 and 5.0, respectively) was markedly increased for these two chemical molecules as

compared to their parent analogue i.e. (-) - ∆8 - THC DMH (clogP=9.1). This enhanced polarity would be expected

to reduce the depot effect relative to the more lipophilic parent compound (Fig. 2). A more controlled

deactivation of both AM7410 and AM7438 compared to the parent compound ((-) - ∆8 - THC DMH) will be

achieved by plasma esterases which will lead to the production of inactive metabolites (Fig 3).

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Fig 1: Chemical structures of the three compounds used in this study.

Fig 2: (-) - ∆8 - THC DMH can be categorized here as type B drugs, which are highly lipophilic, and these types of

drugs carry a longer depot effect and are very slowly degraded by plasma esterases. AM7410 and AM7438 would

fall in the type A drug category, as these drugs are more polar and carry less depot effect because of increased

polarity and are quickly hydrolysed by plasma esterases. (Reproduced from Sharma et.al.)5

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Fig 3: The ester introduced in the design of cannabinoids makes this class of novel cannabinoids susceptible to

plasma esterases which convert these molecules into inactive acid metabolites. (Reproduced from Sharma et.al.)5

B: Background and Significance: Research concerning medical uses of marijuana and extracts thereof has

increased considerably over the last several decades. The legalization of marijuana for recreational use in two

states of the USA (Colorado and Washington) has further intensified the need to examine cannabinoid agents

both for their potential therapeutic as well as harmful properties.6 Cannabis sativa is the plant from which active

components of marijuana are extracted. The plant has been used in traditional medicines for several centuries

for conditions such as appetite stimulation, pain management and spasms. 7

The identification of cannabinoid receptors and endogenous cannabinoid-like ligands further helped our

understanding of the pharmacological working(s) of THC as well as other cannabimimetic agents. Two principal

cannabinoid receptors have been identified and named cannabinoid receptor 1 (CB1R), originally characterized by

Devane et al. in 1988,8 and cannabinoid receptor 2 (CB2R), originally described by Munro et.al. in 1991.9 CB1R is

primarily distributed in the CNS and likely is responsible for the major psychotropic activities of THC and other

cannabimimetic agents. CB2R is primarily concentrated in the periphery and especially on immune cells like

macrophages.10 Following these discoveries, two principal endogenous cannabinoid ligands were identified,

namely anandamide (AEA; arachidonoyl ethanolamide) and 2-arachidonoyl glycerol (2-AG).10 2-AG is found in

much higher concentrations in the brain as compared to anandamide, and thus it has been proposed that 2-AG is

the major neurotransmitter molecule in the endocannabinoid signalling system.10

Therapeutic areas: THC is mainly responsible for the psychotropic effects (“high”) of the cannabis plant. Some

therapeutic effects of the cannabis plant are contributed by another cannabinoid constituent in the plant,

cannabidiol (CBD). CBD may act as an anti-emetic, neuroprotective and anti-inflammatory agent.11 There are

11 very few prescription-based cannabinoid preparations available for medical use. Depending on the country,

cannabinoid preparations available in pharmacies are: 1) oral THC marketed as Dronabinol (Marinol®); 2)

Nabilone (brand name: Cisamet), a hexahydrocannabinol structurally related to THC and 3) Nabiximols (Sativex®),

which is marketed as a sublingual spray and contains THC and CBD in a 1:1 ratio.12,13

In the 1970’s and 80’s, several clinical trials were performed to test the efficacy of dronabinol for inhibition of

nausea and vomiting, side effects caused by chemotherapeutic agents.14 The results of the clinical trials

established that oral THC is effective as an anti-emetic to inhibit nausea and vomiting.14 With further studies, it

was found that twice-a-day dosing of 2.5 mg dronabinol results in an effective anti-emetic effect in cancer

patients.14 The orexigenic effect (increased appetite) induced by THC has been known for centuries, and this

effect of THC has been utilized for treating loss of appetite in patients suffering from HIV/AIDS. 15 In recent

decades, clinical trials have suggested efficiency of dronabinol for also treating anorexia.16 Dronabinol has also

been prescribed for the treatment of chronic neuropathic pain, eliciting analgesia in patients suffering from, e.g.,

multiple sclerosis.17 THC can be beneficial to HIV-infected people in treating their neuropathic pain sensations.18

Other small-scale studies have indicated that THC potentially can be used in various chronic pain-related diseases

like rheumatism and fibromyalgia.17

Pharmacokinetic issues with cannabinoids: THC is highly lipophilic and hence, in practical terms, not water

soluble. Its partition coefficient in n-octanol/water is around 6000, which is an experimentally calculated ratio

using a flask shake method.18 THC is also thermo- and photolabile. The pKa value for THC is about 10.6, and the

compound rapidly degrades in an acidic environment.18 For recreational purposes, the most common route of

THC administration is through smoking marijuana. For therapeutic purposes, THC is given by the oral route

(Dronabinol). When given orally, THC absorption is highly erratic and slow.18 Peak plasma concentration may

occur anytime between 60 min to 6 h after ingestion in different subjects. THC is rapidly degraded in the

stomach’s acidic environment. In the stomach, THC is converted into various substituted cannabidiol-like-

products as well as the minor ∆8-THC isomer. THC is also subject to an extensive first-pass metabolism, especially

when given orally. A dronabinol capsule of 10 mg resulted in the bioavailability of only 6 to 7 % THC in the

studied subjects, concomitant with high inter-subject variability.18

12 THC distribution in the body is also one of the issues with oral THC and smoked cannabis. Studies with

radiolabelled THC showed that after chronic THC administration, maximal concentration of THC is found in fat

tissues, and the concentration ratio of THC in fat tissues to brain was 27:1 after 7 days of administration and 64:1

after 27 days of administration.19 It has also been reported that only 1% of total administered THC is required for

its psychoactive effects.19

Given its high lipophilicity, THC rapidly partitions into tissues which are highly perfused, especially adipose tissues.

This sequestration of THC in fat tissue accounts for its appreciable volume of distribution along with a very slow

elimination rate and, especially in the case of oral ingestion, delayed pharmacological effects resulting from the

depot effect.19 The depot effect seen with THC may be attributed to the direct deposition of THC in adipose

tissues or, as several studies reported, THC’s active metabolite, namely 11-OH-THC. 11-OH THC forms conjugates

with fatty acid in adipose tissues. It is still unclear whether the depot effect seen with THC is because of THC itself

or because of the reactivity of11-0H THC with fatty acids in adipose tissues. Haggerty et.al20 reported that 11-OH

THC forms a conjugate with palmitic acid, and the resulting conjugate, 11-palmitoyl –delta-9-THC, is a psycho-

active compound in that it produces catalepsy (muscle rigidity) and hypothermia (lowered temperature) when

injected to rats.

Effect of THC in laboratory animals: In parallel with humans, laboratory animals also experience behavioural and

physiological effects of THC (e.g., catalepsy and hypothermia). Since the early 1980’s, the tetrad test has been

employed to evaluate the effects of novel cannabinoid agents.21 The tetrad test includes four characteristic

behaviours induced by cannabimimetic agents in laboratory animals: 1- decrease in spontaneous activity, or hypo

locomotion; 2- analgesia; 3- catalepsy; and 4- hypothermia.22 This tetrad test was developed primarily for

rodents. Mice display more profound hypothermia and analgesia compared to rats, which prompted me to use

mice in the reported studies.22 The analgesia test component was selected over other tetrad tests based on my

preliminary studies, which suggested that analgesia induced by cannabinoid agents and evaluated in the standard

tail-flick test parallels the proposed “soft-drug” profile of the drugs. Tail-flick latency increases with an increase in

drug level in the body, and latency decreases as the tested drug level deceases in body as it gets metabolized to

its respective inactive metabolite. Tail-flick withdrawal in a hot water bath was selected over other analgesia

assays because of its ease and efficiency.

13 The validity of the soft drug approach has already been demonstrated with drugs like esmolol (a class II anti-

arrhythmic β-blocker) and remifentanil (a potent opioid used during pre and post-operative analgesic), both of

which are now available as prescription medicines. Given the rise of interest of cannabinoids in the field of

medicine (especially as potential pain medications), it will be extremely helpful to examine cannabinoid agonists

designed to be potential soft drugs.

MATERIALS AND METHODS:

Animals: Young (aged 3-4 weeks) male CD-1 mice weighing between 25-35 grams were used. . Mice were

housed in groups of 4 in a single cage. Mice were kept in a 12-hour day, 12-hour night light cycle routine. All the

experiments were performed during the 12-hour light phase. All animals had free access to food and water. Mice

habituated to the new environment of the animal facility for at least one week before any handling or

experiments were performed. For each set of experiments, an experimentally naïve group of mice was used. All

the animals were purchased from a listed Northeastern University approved vendor (Charles River Breeding

Laboratories, Wilmington, MA, USA). All experiments performed were in accordance to the protocol no: 13-1134

R approved by Northeastern University’s Institutional Animal Care and Use Committee (NU-IACUC).

Drugs: AM7410, AM7438 and (-) - ∆8 - THC DMH were provided by the chemistry section of the Center for Drug

Discovery, Northeastern University, Boston, MA. All drugs were stored at -20˚C. For preparing the drug

suspensions, aliquots of thawed drug stock solutions were taken based upon dosing need. Total injection volume

delivered to each mouse was 10 ml/kg. The organics used to prepare injectable forms of all three drugs were

dimethyl sulfoxide (DMSO); Tween 80 and propylene glycol (PEG), in a final concentration of 2%, 4%, and 4%,

respectively, in saline.

Analgesia: A standard mouse tail-flick assay was used to profile the in vivo analgesic effect of the test

compounds. An effective analgesic agent increases the latency time before the animal withdraws its tail from a

warm-water bath. A cartoon representation of the experimental set-up is shown below (Fig 4). Three compounds

(-) - ∆8 - THC DMH, AM7410 and AM7438 were tested in the tail-flick assay at different doses. For each dose,

naïve mice (n=6) were used. Animals experienced 3 days of habituation followed by a testing session (day 4).

This assay was carried out at ambient room temperature (22-24°C). On any given day of testing or habituation

training, animals were acclimatized to the experimental room for 30 min prior to any handling. This

training condition included dipping the terminal 2

the third day, each animal received a saline injection to acclimatize

the test day, the water bath was increased and

min (the baseline reading). A cut-off period of 10 sec was

water. After 30 sec post-recording of the base

predetermined dose. Subsequent readings were recorded

injection. Along with the drug injections, one group (n=6) of mice was kept

this group only received the vehicle instead of drug.

which was timed in seconds and then converted into a Maximum Possible Effect (MPE) score. The formula for

converting raw analgesia data into a MPE score is:

% Maximum Possible Effect (MPE) = 100 * [(Test Response

Response)]

The MPE data are used to generate a dose

potencies, duration of action, onset and offset

acclimatized to the experimental room for 30 min prior to any handling. This

dipping the terminal 2-3 cm of tail in a water bath maintained at 38

a saline injection to acclimatize the animals to the injection procedure. On

creased and maintained at 52°C, and the first reading was taken and noted at

off period of 10 sec was used to prevent any injury to the tail because of the hot

recording of the baseline readings, each animal received the drug injection of

ubsequent readings were recorded at 20 min, 60 min, 180 min, and 360 min post

ns, one group (n=6) of mice was kept reserved for obtaining con

the vehicle instead of drug. The raw data included tail flick withdrawal by each mouse

converted into a Maximum Possible Effect (MPE) score. The formula for

MPE score is:

= 100 * [(Test Response- Baseline Response)/(Maximum Response

used to generate a dose-response curve for each of the three test compounds, from which

potencies, duration of action, onset and offset of action will be determined.

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acclimatized to the experimental room for 30 min prior to any handling. This acclimation

tained at 38˚C for 10 sec. On

the injection procedure. On

52°C, and the first reading was taken and noted at 0

used to prevent any injury to the tail because of the hot

d the drug injection of a

at 20 min, 60 min, 180 min, and 360 min post-drug

ed for obtaining control data;

The raw data included tail flick withdrawal by each mouse,

converted into a Maximum Possible Effect (MPE) score. The formula for

Baseline Response)/(Maximum Response-Baseline

response curve for each of the three test compounds, from which

15 Fig 4: Brief overview the tail-flick analgesia experiment. Only 2 to 3 cm of the distal end of the tail will be dipped

into the water bath.

Statistical Analysis: Statistical comparison of tail-flick latency data obtained from AM410 and (-) - ∆8 - THC DMH

studies will use two-way repeated measures ANOVA along with Bonferroni’s post-hoc test to assess the time-and

dose effect functions. The statistical analysis was performed using GraphPad Prism 5.03 (GraphPad Software, San

Diego, CA). To analyse and compare tail-flick latencies data from AM7438 and AM7410, a linear mixed model

repeated measures ANOVA (IBM® software package, SPSS, v.21) was applied.

RESULTS:

Analgesic effect of AM7410 and (-) - ∆8 - THC DMH: Tail-flick latency data experiments conducted in mice

demonstrated that AM7410 significantly differs from (-) - ∆-8 - THC DMH in terms of its duration of action. It is

evident from Fig. 5 that AM7410 has a quicker onset and quicker offset of action when compared to (-) - ∆8 - THC

DMH. The ANOVA analysis of the tail-flick data showed significant effects for dose (D) [F (2,120)=160.6; P<0.0001]

and time (T) [F(14,120)=4.5; P<0.0001] along with the D × T interaction for three doses (0.1,0.3, 1.0 mg/kg) of each

compound, i.e., AM7410 and (-) - ∆8 - THC DMH. .

5a 5b

Fig. 5 a&b: Tail-flick latencies of mice (n=6 for each dose) in a hot water bath (52˚C) post administration of

AM7410, an ester analog of (-) - ∆8 - THC DMH are shown in Fig. 5a. Tail-flick latencies of mice (n=6) administered

Time (min)

20 60 180 360

% M

PE

0

20

40

60

80

100

Time (min)

20 60 180 360

% M

PE

0

20

40

60

80

100

0.1 mg/kg0.3 mg/kg1.0 mg/kgVehicle

∆∆∆∆8-THC-DMH

AM7410

16 a lower dose (0.1mg/kg) of AM7410, (-) - ∆8 - THC DMH respectively and vehicle are shown in Fig 5b. Latencies

were converted into maximum possible effect (%MPE) displayed on the ordinate. MPE is expressed as the group

mean ±SEM.

Analgesic effect of AM7438: The chemical difference between AM7438 and AM7410 is slight, i.e., AM7438 (log

P=5) contains a cyano group (Fig. 2), which makes the compound more polar vs. AM7410 (log P= 6.59). The tail-

flick latency data is congruent with this difference (Fig. 6). AM 7438 has a shorter duration of action when

compared to AM7410 at the two doses (0.3 mg/kg and 1 mg/kg) examined. A mixed repeated measures ANOVA

applied to the tail-flick latency data with AM 7410 and AM7438 during 180-min and 360-min time points (offset

phase) revealed significant effects for drug (D) [F1,44=8.98; p<0.0004], dose level (L) [F1,44=40.95;p<0.001] and time

(T) [F1,44=28.46;p<0.001]. All the three parameters (D, L, and T) had significant differences when compared pair-

wise using Sidak multiple comparison t-test (p=0.005). This pair-wise comparison of three parameters provides

evidence of a faster off-set of AM7438 as compared to AM7410.

In both the experiments, tail-flick latency caused by vehicle is not compared using statistical analysis graphically

because MPE did not exceed 20% in any of the examined four time-points.

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Fig 6: Tail-flick latencies of mice (n=6 for each dose) in a hot water bath (52˚C) post administration of AM7438

and AM7410. Latencies are displayed as maximum possible effect (%MPE) and shown on the ordinate. %MPE is

expressed as the group mean ±SEM. The data for AM7410 is reproduced from Fig. 5.

The results generated from testing two lower doses of AM7438 are displayed in Fig.7. A two-way repeated

measures ANOVA indicated significance for Dose (D) [F3, 20 = 125.1], Time (T) [F3, 60 = 61.4] and the interaction

D x T [F9, 60 = 10.8].

Time (min)

20 60 180 360

%M

PE

0

20

40

60

80

100

0.3 mg/kg AM74381.0 mg/kg AM74380.3 mg/kg AM74101.0 mg/kg AM7410

Fig 7: Tail-flick latencies of mice (n=6 for each dose)

of AM7438. Latencies are displayed as maximum possible effect (%MPE)

expressed as the group mean ±SEM.

Summary and Discussion: The main aim of this thesis project was to evaluate the

potential cannabimimetic agents using an in

the analgesic effect in this mouse tail-flick model

pharmacological effect of each test agent.

Results from the tail-flick analgesia studies suggest that both of the novel agent

from their parent analogue (-) - ∆8 - THC DMH

AM7438 both have quicker onsets and offset

polar molecule of the three compounds evaluated

the compound more polar in comparison with AM7410 and

as displayed in Fig6. This increase in polarity

when compared to AM7410. Future studies with these two molecules will involve screening them

vivo and behavioural models to extend the characterization of

example, hypothermia studies with AM7410 and AM7438 along with the presence of a CB1R antagonist will be

of mice (n=6 for each dose) in a hot water bath (52˚C) post administration of four doses

maximum possible effect (%MPE) and shown on the ordinate. %MPE is

The main aim of this thesis project was to evaluate the analgesic effect

cannabimimetic agents using an in-vivo mouse model i.e. tail-flick latency assay. As a function of time,

flick model can be used as a surrogate indicator for the

t agent.

flick analgesia studies suggest that both of the novel agents AM7410 andAM7438

THC DMH in terms of their analgesic time course profile.

and offsets of action as compared to (-) - ∆8 - THC DMH. AM7438 is the mo

evaluated in this study. The cyano group in the AM7438

the compound more polar in comparison with AM7410 and (-) - ∆8 - THC DMH, as observed from clogP values and

his increase in polarity is a likely determinant of the reduced duration of action of AM7438

Future studies with these two molecules will involve screening them

extend the characterization of these two compounds as “soft drugs”.

studies with AM7410 and AM7438 along with the presence of a CB1R antagonist will be

18

˚C) post administration of four doses

on the ordinate. %MPE is

analgesic effect of two novel

As a function of time,

can be used as a surrogate indicator for the time course of the

s AM7410 andAM7438 differs

. Thus, AM7410 and

. AM7438 is the most

in this study. The cyano group in the AM7438 (Fig. 3) makes

as observed from clogP values and

duration of action of AM7438

Future studies with these two molecules will involve screening them using other in-

these two compounds as “soft drugs”. As a specific

studies with AM7410 and AM7438 along with the presence of a CB1R antagonist will be

19 helpful for characterizing the involvement of CB1R in the analgesic effect of these agents. It will also be a

significant step in the development of this project to evaluate these molecules in drug-discrimination models. If

the cannabinoid esters were found substitute for THC in drug discrimination, the esters might represent

potentially safer alternative analgesics with less risk of THC-induced psychobehavioral adverse events for

potential use as pre and post-operative analgesics and pain management in e.g. multiple sclerosis.

References:

1- Bodor, N; Buchwald P. Soft Drug Design: General Principles and Recent Applications, Medicinal Research

Reviews. Dec.1999, Volume 20, Issue1, pp.58-101.

2- Bodor, N; Buchwald, P. Designing Safer (Soft) Drugs by Avoiding the Formation of Toxic and Oxidative

Metabolites, Molecular Biotechnology. Feb.2004, Volume 26, Issue2, pp.123-132.

3- Ertl, P; Rohde, B; Selzer,P. Fast Calculation of Molecular Polar Surface Area as a Sum of Fragment-Based

Contributions and Its Application to the Prediction of Drug Transport Properties, 2000, Journal of

Medicinal Chemistry, Volume43, pp.3714-3717.

4- Lipinski, C.A; Lombardo; F, Dominy, B.W; Feeney, P. Experimental and Computational Approaches to

estimate solubility and permeability in drug discovery and development settings. Mar. 2001, Advanced

Drug Delivery Reviews, Vol 46, Issue 1-3, pp.3-26.

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