Incannex releases groundbreaking results from psilocybin trial to treat anxiety, moves to Phase 2b FDA trials

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By Imelda Cotton - 
Incannex Healthcare NASDAQ IXHL results psilocybin trial treat anxiety Phase 2 FDA

Cannabinoid and psychedelic medicine biotechnology company Incannex Healthcare (NASDAQ: IXHL) has announced positive top-line results from its Phase 2 Psi-GAD1 clinical trial of psilocybin for the treatment of generalised anxiety disorder (GAD).

The trial of the seven week treatment program was developed by Incannex in partnership with the Clinical Psychedelic Lab at Melbourne’s Monash University and led by globally recognised psychedelics expert Dr Paul Liknaitzky.

It is reported to have met its primary endpoint, demonstrating a large clinical effect in the psilocybin treatment group over the placebo group.

Participants were assessed using the Hamilton Anxiety Rating Scale (or HAM-A), one of the first rating scales developed to measure the severity of anxiety symptoms.

The scale consists of 14 items, each defined by a series of symptoms and measures psychic anxiety (mental agitation and psychological distress) and somatic anxiety (physical complaints related to anxiety).

The Psi-GAD1 trial showed a reduction in HAM-A score from baseline in the psilocybin group of 12.8 points, from 29.5 (out of 56) at baseline to 16.7 (out of 56) at week 11 (six weeks following the final dosing session), representing a decrease of 9.2 points over the placebo group.

Approximately 44% of patients in the psilocybin group showed a clinically meaningful improvement of at least 50% reduction in anxiety score from baseline — a ‘response rate’ more than four times higher than that of the placebo group.

27% of patients in the psilocybin group achieved full disease remission — a rate more than five times higher than that of psychotherapy with placebo.


Psilocybin within the context of Psi-GAD psychotherapy was observed to be well-tolerated, with only mild and moderate adverse events reported that are consistent with known effects of the drug.

No serious or severe adverse events were observed and only one out of 73 participants withdrew from the trial during the treatment period.

Encouraging results

Incannex chief executive officer Joel Latham said the company was encouraged by the results.

“This is the first time psilocybin has been investigated for the treatment of GAD and the reduction in HAM-A scores we have observed are far greater than those reported from trials on established medicines for the treatment of anxiety,” he said.

“The improvement in anxiety scores in this trial [is] of a similar magnitude to the change seen in studies investigating psilocybin for treatment of depression disorders.”

Focus on safety

Mr Latham was pleased that no serious or severe adverse patient events were observed, being testament to the focus on safety within the Psi-GAD treatment protocol.

“The safety and efficacy results implore us to continue the development of Psi-GAD through large-scale well-controlled trials because this treatment method has the potential to improve the quality of life for millions of people suffering from GAD,” he said.

Follow-up trial

Incannex has designed a follow-up phase 2B clinical trial to be conducted at multiple sites across the US and UK.

The trial will be designed with the help of UK-based contract research organisation Clerkenwell Health, which specialises in psychiatry and central nervous system treatments.

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