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. 2025 Jun 20:16:1606976.
doi: 10.3389/fphar.2025.1606976. eCollection 2025.

KETAMIR-2, a new molecular entity and novel ketamine analog

Affiliations

KETAMIR-2, a new molecular entity and novel ketamine analog

Itzchak Angel et al. Front Pharmacol. .

Abstract

Ketamir-2 is a new molecular entity, and a novel ketamine analog designed to improve oral bioavailability, and offer a superior safety profile compared to existing ketamine treatments. It was found that Ketamir-2 is a low affinity NMDA receptor antagonist, that selectively binds to the PCP site. Its IC50 on this receptor site is ∼100 µM. Ketamine acts as an NMDA receptor antagonist (0.5-1 µM affinity) and influences opioid receptors, monoaminergic systems (such as serotonin and dopamine). The selectivity of Ketamir-2 was evaluated across a broad range of receptors, transporters, and binding sites, but no activity was detected. Ketamir-2 is a lower affinity and selective PCP-site NMDA antagonist, compared with ketamine. Upon oral administration, Ketamir-2 does not induce hyperlocomotion in mice. Thus, it is different from Ketamine, which induces marked hyperlocomotion, a behavior which is thought to mimic the psychomotor agitation and disorganized behavior seen in schizophrenia, often linked to disruptions in brain neurotransmitter systems. Ketamir-2 was also evaluated via several pharmacological tests in mice to evaluate its anti-depressive and anxiolytic effects. These tests included the Open Field test (OFT), Elevated Plus Maze (EPM), and Forced Swimming Test (FST); all of which are commonly employed behavioral assays used to evaluate the efficacy of anxiety and depression medications. While showing significant effects in these tests at variable doses, ketamine, which was used as a positive control, did not differ from vehicle treatment or showed an opposite response to Ketamir in the majority of the tests studied.

Keywords: NMDA; anti-depressant; hyperlocomotion; ketamine; ketamir-2; neuropathic pain.

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Conflict of interest statement

Authors IA and EA were employed by Mira Pharmaceuticals Inc. Authors RP and EP were employed by Pharmaseed Ltd. Author WD, FA were employed by Biotrial.

Figures

FIGURE 1
FIGURE 1
Structures of ketamir-2 and ketamine.
FIGURE 2
FIGURE 2
Comparative binding affinities towards the PCP-site on NMDA receptor. (A) Ketamir-2, (B) Nor-Ketamir. Inhibition of the PCP site is depicted in squares.
FIGURE 3
FIGURE 3
Effects of acute oral administration of Ketamir pamoate, ketamine HCl or vehicle on the spontaneous horizontal locomotor activity over a period of 1 h by 5 min intervals in male C57BL6/J mice. Results are expressed as mean ± SEM. * and ***: p < 0.05 and p < 0.001 for ketamir-2 (50 mg/kg, IP) vs. vehicle (IP) by two-way ANOVA test followed by a Dunnett’s multiple comparisons test. ***: p < 0.001 for ketamine (20 mg/kg, IP) vs. vehicle (IP) by two-way ANOVA test followed by a Sidak’s multiple comparisons test.
FIGURE 4
FIGURE 4
Effects of acute oral administration of Ketamir-2, ketamine or vehicle on the spontaneous horizontal locomotor activity over the entire recording period (1 h) in male C57BL6/J mice. Results are expressed as mean ± SEM. ***: p < 0.001 for Ketamir-2 (50 mg/kg, IP) vs. vehicle (IP) by one-way ANOVA test followed by a Dunnett’s multiple comparisons test. ###: p < 0.001 for ketamine (20 mg/kg, IP) vs. vehicle (IP) by two-tailed Student’s t-test for independent samples.
FIGURE 5
FIGURE 5
Open field parameters. In each group 8 mice were evaluated, (A) Total distance moved (cm); (B) mean velocity (cm/seconds) and (C) cumulative time spent in center (seconds). One-Way ANOVA compared to vehicle control: *p < 0.05 and ***p < 0.001, ****p < 0.0001.
FIGURE 6
FIGURE 6
Elevated plus maze (EPM) parameters. In each group 8 mice were evaluated. (A) Distance moved (cm); (B) mean velocity (cm/seconds), (C) Cumulative time spend in closed arms combined (s), (D) cumulative duration in the open arms, (E) Time spent in the center, (F) Cumulative time spent in the open arms (G) relative distance in closed arms and (H) relative distance in open arms. One-Way ANOVA compared to vehicle control: *p < 0.05, **p < 0.01 and ***p < 0.001.
FIGURE 7
FIGURE 7
Forced swimming test (FST) parameters. In each group 8 mice were evaluated. (A) Distance moved (cm); (B) mean velocity (cm/seconds), (C) highly mobile (seconds), (D) mobile, and (E) immobile (seconds). One-Way ANOVA compared to vehicle control: *p < 0.05.

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