Main Research Findings

1) TAK-653 has the potential to treat major depressive disorder and treatment resistant depression with a lower risk of side effects compared to current pharmacological treatments.

2) TAK-653 improves cognitive functioning and synaptic responses through the strict regulation and activation of AMPA receptors.

 

Selected Data

1) The research team of Hara et al examined the efficacy of the AMPA receptor agonist TAK-653 versus the NMDA receptor antagonist, ketamine, in treating major depressive disorder and treatment resistant depression. For the purpose of the study, Sprague-Dawley rats were utilized and allowed to habituate to standard laboratory conditions for 1 week before experimental testing occurred. In order to administer the experimental drugs to the animals, TAK-653 was suspended in 0.5% methylcellulose in distilled water, ketamine was diluted in 0.9% saline and administered in combination with NBQX disodium salt dissolved in 0.9% saline, when appropriate [1].

The first behavioral assessment evaluated dominant-submissive behavior in the reduction of submissive behavior model (RSBM) test. The testing apparatus consisted of two identical chambers that were connected by a narrow passageway with a 10 mL beaker of 10% skim milk and 4% sucrose placed in the middle to allow enough space for only one animal to access the feeder. Before the first trial the animals were assigned to pairs and placed into the testing apparatus. During the first training period, the researcher recorded and scored the amount of time spent drinking the milk by each rat over 5 minutes. After 5 minutes the animals were removed and placed back into their cages where they were allowed to eat for 1 hour before being deprived until the next training session. Dominance level was determined based on the amount of time each rat spent at the feeder.

After 4 weeks of training, the pairs with daily dominance levels longer than 80 seconds for the previous 6 tests continued on for further testing. After 5 days of no testing the selected pairs were further evaluated following the same testing protocol for an additional 3 days. The pairs were then randomly assigned to treatment groups based on their dominance levels. The pairs included in the control group received the same dose of a vehicle compound, while the submissive rats in the ketamine group were intraperitoneally injected with 30 mg/kg of ketamine and their dominant counterparts were treated with a vehicle. When appropriate, 10 mg/kg of NBQX was intraperitoneally injected 10 minutes before administration of ketamine. Dominance levels were assessed the following day in order to subtract the dominance level of the rats on the day of drug administration to calculate the overall delta dominance level [1].

TAK-653 was administered to the rats at a different laboratory in order to evaluate its antidepressant effects through behavioral testing with some modifications made to the testing parameters and apparatus. The testing apparatus consisted of two identical chambers connected by a tunnel with a 10 mL beaker of milk and 9% sucrose placed in the middle of the tunnel. During the first week of testing the rats were paired together and placed into the apparatus in order to habituate to the chambers and feeder for 5 minutes at a time. During the second week of testing the research team recorded and scored the amount of time each rat spent drinking the milk over a 5 minute period. If the pairs met two pieces of criteria they were selected to continue to the next portion of the study, including: 1) a significant difference in the pair’s average drinking score, and 2) the score of the dominant animal was >/= 25% of the submissive animal [1].

Based on their dominance levels, the animals were randomly assigned to the control group or to an experimental group receiving either 0.1 mg/kg or 1 mg/kg doses of TAK-653. Administration of treatment took place 1 day after the animals were randomized into the treatment groups. Similar to the first portion of the study the animals in the control group both received a vehicle compound. In both TAK-653 groups, the submissive animal received an intraperitoneal injection of the experimental treatment while the dominant partner was administered a vehicle. The treatments were given to the animals 2 hours before 5 minutes of testing took place. After testing the rats returned to their cages and were given access to food for 1 hour before being deprived until the following day. Testing took place Monday through Friday, however, drugs were still administered daily and the animals were allowed free access to food and water on the weekends.

After the RSBM testing was complete the researchers continued to test locomotor activity in 8-9 week old Sprague-Dawley rats, using a SUPERMEX spontaneous motor analyzer. The animals were placed into an apparatus consisting of separate locomotion chambers and allowed to habituate for 1 hour prior to testing. After an hour they were removed and treated with either the experimental treatment or a vehicle compound and returned to the chamber. Over the 2 hour time frame following drug administration the researchers recorded the cumulative locomotor activity of the test subjects [1].

2) The research team of Suzuki et al assessed the pharmacological characteristics of the AMPA receptor TAK-653 in order to better understand the ability of the compound to improve synaptic connections and cognitive functioning. For the purpose of this study several different animals were utilized, including ICR and C57BL/6 J mice, Sprague-Dawley and Long-Evans rats, and male cynomolgus monkeys [2]. All animals were maintained under standard laboratory conditions in a light-controlled room and allowed to habituate for 1 week prior to experimentation.

The first behavioral test performed was the novel object recognition test using 6 week old male Long-Evans rats. On the first day of the experiment the rats individually habituated to the empty testing apparatus for 10 minutes and randomly assigned to an experimental treatment group. The initial acquisition trial occurred on day 2 where the rats were allowed to explore two identical objects denoted A1 and A2, for 3 minutes. 48 hours later the retention trial took place where the rats were allowed to explore a familiar object, A3, and a novel object, denoted as B, for 3 minutes. TAK-653 was administered orally and AMPA was administered intraperitoneally, either 2 hours or 0.5 hours prior to both the acquisition and retention trials [2].

The radial arm maze test was carried out using 9-week-old male Long-Evans rats. The maze apparatus was 10 cm wide, 40 cm high, and elevated 50 cm above the floor. Throughout the experimental period the rats had their food restricted to 85% of their free-feeding body weight and were trained to collect food pellets from the arms of the maze apparatus. The testing sessions began by placing each rat in the maze apparatus facing the fixed arm in order for the research team to record the entry of the rats into the different arms until all pellets were consumed or 5 minutes had passed. The test subjects were administered either TAK-653, LY451646, or AMPA 1.5 hours, 1 hour, or immediately prior to the delivery of a vehicle compound or MK-801 [2]. 30 minutes after the vehicle was administered the rats were placed on the maze for testing and recording to take place.

4-6 year old male cynomolgus monkeys weighing 4-6 kg were used to perform delayed match-to-sample tasks using a Cambridge Neuropsychological Test Automated Battery system. The researchers mentioned that throughout the experiment the animals were maintained at 80% of their free-feeding body weight. DMTS tasks were followed by the induction of maternal immune activation. The procedures included administering pregnant female C57BL/6J mice with 5 mg/kg of poly-I:C dissolved in sterile 0.9% NaCl solution on gestation day 15 [2]. The compound was administered intravenously through the tail vein in a volume of 5 ml/kg.

The social approach and avoidance test included a three-chamber apparatus and was conducted using C57BL/6J mice. The apparatus included clear dividing walls and transparent cylinders placed in the outer chambers to avoid direct physical contact between a target animal and test animal. The target animals were defined as mice of the same age as the test animals without having any previous contact with them. One hour prior to testing, TAK-653 or a vehicle compound was administered perorally in a 0.3 mg/kg dose. Each test animal was placed in the middle chamber of the apparatus and allowed to habituate for 3 minutes with all clear partitions closed. This was followed by the gradual removal of all partitions and allowing the animals to explore freely for 5 minutes while the research team calculated the sniffing index as a measure of sociability [2].

 

Discussion

1) The results of the RSBM test the animals were subjected to assess the antidepressive effects of ketamine and TAK-653 by exposing the subjects to daily competition for food reward and allowing a dominant/submissive relationship to develop over the training period. The development of this relationship was essential to the behavioral testing considering that the submissive animal that spends less time drinking the milk, represents the depressive behavior that the researchers are attempting to treat with the experimental compound. Previous research has found that typical antidepressants such as fluoxetine and imipramine did not significantly increase dominant behavior in the submissive rats. That being said, it was decided by the research that ketamine would be used in the first portion of the study to treat depressive behavior.

A single intraperitoneally injected 30 mg/kg dose of ketamine was found to significantly improve dominance levels in a manner similar to the group treated with a vehicle. The rats were then pretreated with the AMPA receptor antagonist NBQX prior to the injection of ketamine to determine if the anti-depressive effects were dependent on the involvement of AMPA receptor activation. Pretreatment with NBQX was found to inhibit the improvement of dominance levels in the animals elicited by treatment with ketamine alone. These findings indicate that the anti-depressant effects elicited by ketamine during the RSBM test are dependent on the activation of AMPA receptors [1].

The researchers followed a similar treatment protocol when administering TAK-653 to the animals. However, while ketamine was only administered in a dose of 30 mg/kg, TAK-653 was given to the animals in doses of 0.1 mg/kg and 1 mg/kg. Serum levels of TAK-653 were found to reach their peak levels between 1 and 2 hours after administration. That being said, behavioral testing began 2 hours after administration of the compound. The 1 mg/kg dose of TAK-653 was shown to significantly improve dominance levels starting on day 7 and remaining through the end of the study. Improved dominance levels were also noted with administration of a 0.1 mg/kg dose of TAK-653, however, the results were more significant after treatment with 1 mg/kg [1].

Figure 1: Changes in the average dominance levels over three weeks of experimental treatment with TAK-653.

A key side effect of antidepressant treatment with ketamine and other NMDA receptor antagonists is hyperlocomotion that acts as a marker of acute psychosis. The second behavioral test performed in this study consisted of observation and recording of the rats’ locomotor activity in an open chamber over the course of 2 hours, both before and after treatment with 30 mg/kg of ketamine or 0.1, 1, of 10 mg/kg of TAK-653. Hyperlocomotion, regarded as an indicator of acute psychosis, was observed in the rats treated with 30 mg/kg of ketamine, while 0.1, 1, and 10 mg/kg doses of TAK-653 did not affect locomotor activity in the animals [1].

2) As it was previously mentioned, the research team of Suzuki et al used the novel object recognition task in order to assess visual learning and memory in rats. Peroral administration of TAK-653 at doses of 0.03, 0.1, and 0.3 mg/kg were shown to significantly improved NDI scores. These findings suggested that the nootropic may have the potential to enhance visual learning and memory in doses greater than 0.03 mg/kg. Comparatively, when the rats were perorally treated with LY451646 at doses greater than 1 mg/kg visual learning and memory improved, however, the compound induced seizures when delivered in doses of 10 and 30 mg/kg. Similar findings were reported when the animals were given AMPA; 30 mg/kg doses administered intraperitoneally induced seizures while 10 mg/kg doses resulted in abnormal behavior like head turning. Administration of lower doses of AMPA did not result in any improvements in visual learning or memory [2].

Figure 2: Changes in the NDI assessed through the novel object recognition task in response to A) 0.01 mg/kg, 0.03 mg/kg, 0.1 mg/kg, and 0.3 mg/kg of TAK-653 administered perorally, in comparison to B) 0.3 mg/kg, 1 mg/kg, and 3 mg/kg of AMPA administered intraperitoneally.

The radial arm maze task was performed to evaluate the effects of TAK-653 on working memory in rats with a MK-801 induced memory deficit. MK-801 disrupted memory performance in trained rats when administered subcutaneously in doses of 0.08 mg/kg. TAK-654 delivered perorally in doses of 0.1 0.3, 3, and 10 mg/kg were all found to significantly reduce the induced deficits. These findings suggest that treatment with the nootropic enhances working memory in the presence of a broad range of hypoglutamatergic conditions. It is important to mention that the researchers also evaluated the effectiveness of AMPA receptor potentiator, PF-04958242. In rat hippocampal cells, this potentiator was shown to produce an increase in calcium in the absence of AMPA. In a manner similar to LY451646, doses of the compound greater than or equal to 0.1 mg/kg improved visual learning and memory measured by the novel object recognition test, however, working memory evaluated by the radial arm maze task remained unchanged [2].

Figure 3: Changes in the mean number of errors calculated during the radial arm maze task in response C) 0.1 mg/kg, 0.3 mg/kg, 3 mg/kg, and 10 mg/kg of TAK-653 administered perorally; in comparison to D) 0.03 mg/kg, 0.1 mg/kg, 0.3 mg/kg, and 1 mg/kg of LY451646 administered perorally; and E) 0.1 mg/kg, 0.3 mg/kg, 1 mg/kg, and 3 mg/kg of AMPA administered intraperitoneally, following a 0.08 mg/kg dose of MK-801 to induce memory deficits.

Changes in working memory induced by administration of TAK-653 was also assessed in monkeys through the delayed match-to-sample paradigm. While fasted, the monkeys were perorally administered 0.06 mg/kg of the nootropic. TAK-653 was found to increase delayed match-to-sample accuracy at a 16 second delay interval. In order to ensure the results were not attributable to a training effect, the monkeys were tested 48 hours later to find that the improvement in accuracy returned to baseline levels after 24 hours. These findings suggest that TAK-653 may have the potential to improve working memory in monkeys at concentrations similar to those observed in rats with both improved visual learning, working memory and recognition memory [2].

Figure 4: Changes in DMTS accuracy over 48 hours defined by the percent of trials correct in response to treatment with TAK-653 administered perorally in a dose of 0.06 mg/kg.

Next, the 5-choice serial reaction time task was performed to evaluate the effects of TAK-653 on attention in rats. The researchers determined that the poor performing animals could be included in a model of ADHD, thus resulting in sub-population analyses that included splitting the population into high and poor performing animals. When perorally administered 2 hours prior to the initiation of the trials, TAK-653 in a dose of 0.3 mg/kg did not elicit significant improvements in attention throughout the entire population. That being said, when looking specifically at the sub-population of poorly performing rats, the nootropic increased the number of correct responses and decreased the number of omissions, indicating that TAK-653 may enhance attention. Similarly, the social approach-avoidance test was conducted to assess the effects of TAK-63 on sociability deficits in the poly-I:C mouse, used as an animal model of schizophrenia. Social activity was measured by the sniffing index which was shown to significantly improve after peroral administration of a 0.3 mg/kg dose of TAK-653 [2].

Figure 5: Changes in sniffing index in response to a 0.3 mg/kg peroral dose of TAK-653 in poly I:C mice.

 

Disclaimer

**LAB USE ONLY**
*This information is for educational purposes only and does not constitute medical advice. THE PRODUCTS DESCRIBED HEREIN ARE FOR RESEARCH USE ONLY. All clinical research must be conducted with oversight from the appropriate Institutional Review Board (IRB). All preclinical research must be conducted with oversight from the appropriate Institutional Animal Care and Use Committee (IACUC) following the guidelines of the Animal Welfare Act (AWA).

 

Citations

[1] Hara H, Suzuki A, Kunugi A, Tajima Y, Yamada R, Kimura H. TAK-653, an AMPA receptor potentiator with minimal agonistic activity, produces an antidepressant-like effect with a favorable safety profile in rats. Pharmacol Biochem Behav. 2021 Dec;211:173289. doi: 10.1016/j.pbb.2021.173289. Epub 2021 Oct 14. PMID: 34655652.

[2] Suzuki A, Kunugi A, Tajima Y, Suzuki N, Suzuki M, Toyofuku M, Kuno H, Sogabe S, Kosugi Y, Awasaki Y, Kaku T, Kimura H. Strictly regulated agonist-dependent activation of AMPA-R is the key characteristic of TAK-653 for robust synaptic responses and cognitive improvement. Sci Rep. 2021 Jul 15;11(1):14532. doi: 10.1038/s41598-021-93888-0. Erratum in: Sci Rep. 2021 Jul 21;11(1):15255. doi: 10.1038/s41598-021-94772-7. PMID: 34267258; PMCID: PMC8282797.

 

TAK-653 is an AMPA receptor positive allosteric modulator that has shown promise in treating major depressive disorder and treatment-resistant depression in rodents. Researchers have long associated mood disorders with the effects of AMPA receptors and related compounds such as the neurotransmitters glutamate and brain derived neurotrophic factor (BDNF). Presently, ketamine, an antagonist to NMDA receptors, is being examined for its potent antidepressive effects. Studies have found that treatment with ketamine leads to a stimulatory effect on AMPA receptors. This results in increased levels of glutamate in the brain as well as the mechanistic target of rapamycin mTOR signaling. Glutamate is associated with the pathology of mood disorders and how they are related to synaptic plasticity and the secretion of BDNF. As ketamine stimulates the mechanisms of AMPA receptors, researchers hypothesize that they are potentially related to the treatment of depression (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9509332/).

While ketamine is capable of treating depression on its own, there are often psychotomimetic and dissociative side effects reported while this drug is being used for treatment. Research has found that the AMPA receptor antagonist, NBQX, blocks the majority of the antidepressive effects of ketamine. The effects of ketamine were also reduced depending on rates of BDNF secretion and mTOR signaling. AMPA receptor activators have been found to elicit quick and potent antidepressive effects, however they are not without limitations. That being said, researchers examined how the AMPA receptor potentiator TAK-653 is capable of effectively treating depression with almost no additional agonistic activity.

Researchers Hara et. Al conducted a study examining the antidepressant behavioral effects of TAK-653 in the rat reduction of submissive behavior model (RSBM) Additionally, the psychotomimetic side effects of TAK-653 were compared to those of ketamine. The experimentation period began with an initial evaluation of the rats in order to determine which of the test subjects would be considered dominant and which were submissive. The dominant rats would be receiving a dose of the vehicle while submissive ones would be receiving 30 mg/kg dose of ketamine. The same methods of evaluating dominance were used when determining the rats that would receive the active dose of TAK-653. Submissive rats were given varying doses of TAK-653 while the dominant animals received a vehicle.

The rats were administered the doses of TAK-653 approximately 2 hours before the test period. On each day the rats received the treatment and were subjected to 5 minutes of behavioral testing, followed by 1 hour of free access to food. Results of this study found that TAK-653 is capable of activating mTOR signaling and producing BDNF in a dose-dependent manner. The study also concluded that while antidepressant effects were seen when treating the rats with ketamine, the compound had a higher tendency to be blocked by antagonists like NBQX, and elicit abnormal behaviors such as hyperlocomotion. These findings allowed researchers to conclude that TAK-653 treats major depressive disorder and treatment-resistant depression more efficiently than ketamine due to the absence of side effects in subjects treated with TAK-653 (https://www.sciencedirect.com/science/article/pii/S009130572100188X).

AMPA Receptor Modulation

Further studies regarding the efficacy of TAK-653 evaluate how the compound modulates the activity of AMPA receptors by observing cortical excitability. Researchers O’Donnell et. Al used transcranial magnetic stimulation (TMS)-induced motor responses to identify these biomarkers as well as the various pharmacodynamic and pharmacokinetic qualities of TAK-653.

The study included 31 adult Sprague Dawley rats and each subject received doses varying from 0.3 to 50 mg/kg of TAK-653. TMS testing took place 75-135 minutes after TAK-653 administration, and at each time point 10 pulses at 80% power were applied to the subjects. Plasma and brain specimens were collected approximately 2-3 hours after TAK-653 administration. Results of the study found that all doses of TAK-653 increased the rate of cortical excitability at a greater degree than the vehicle. However, the most effective dose was 50 mg/kg which resulted in 264.2 ±81.9 ng/g of TAK-653 in the plasma.

Overall, the researchers were able to conclude that using noninvasive stimulation in the brain can lead to accurate identification and generation of neurocircuitry biomarkers, as well as modulate the resulting effects of AMPA receptor activity. As it was previously mentioned AMPA receptors are shown to regulate variables such as glutamate activity, mTOR signaling, and BDNF expression. That being said, this study primarily focused on glutamate activity and through the use of TMS, researchers were granted further insight on glutamate receptor-mediated effects and glutamate synaptic activity in relation to TAK-653 (https://www.nature.com/articles/s41398-021-01451-2).

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