Gilgamesh Pharmaceutical said its Phase IIa trial will investigate the candidate as both a monotherapy and on top of background therapy. Image credit: Shutterstock / shisu_ka.

US-based Gilgamesh Pharmaceuticals will initiate its Phase IIa trial investigating GM-2505, a novel 5-HT2A receptor agonist, in Q1 2024, chief scientific officer Andrew Kruegel told the Clinical Trials Arena.

The Phase IIa trial will be the first time the candidate is investigated in patients with MDD. The company is also investigating the candidate in treatment-resistant depression (TRD) but said it is currently focusing efforts on MDD.

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Half of the subjects will receive an initial low dose of GM-2505, which is considered to be a sub-perceptual dose, followed by a second full dose. The other half will receive a moderate dose followed by a second full dose. This will be the main control for placebo effects in the study.

Gilgamesh also plans to expand the study to include subjects on selective serotonin reuptake inhibitors (SSRI) background therapy after a protocol amendment is approved.

Kruegel added that the Phase IIb trial, which is due to begin in 2025, will have a larger patient population and will use the data from Phase IIa, especially from patients on SSRI background therapy as the company hopes GM-2505 will be used as a combination therapy.

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In contrast to other 5HT2A agonists such as psilocybin, a naturally occurring psychedelic compound found in certain mushrooms, GM-2505 has a fast-acting mechanism of action. According to Gilgamesh, the peak intensity was consistent with a full psychedelic experience, but the duration of those effects was limited to 60-90 minutes compared to psilocybin’s four to six hours.

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“We believe GM-2505 will be much better suited for delivery within the confines of the current healthcare system, which is going to be it’s going to make it very challenging to have six hours supervised psilocybin sessions at any kind of reasonable scale,” Kruegel says.

Positive Phase I data

Last month, the company announced positive results from its Phase I single ascending dose (SAD) trial of GM-2505. The candidate exhibited dose-proportional PK and dose-dependent effects on multiple pharmacodynamic measures, including subjective effects, electroencephalogram (EEG), and neuroendocrine markers.

A range of doses was investigated, with high doses of 15mg and 20mg manifesting a full psychedelic effect while minimal effects were observed below 10mg.

Phase I investigated the candidate in healthy volunteers.

Gilgamesh added that although they are not yet investigating GM-2505 in any other indications, it has the potential to be efficacious in other severe mental health disorders such as alcohol use, anxiety, and obsessive-compulsive disorders.