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Activating a stress circuit in the brain may improve ketamine treatment

New research shows that mice better respond to ketamine when the substance is administered by a male – findings that could help improve ketamine treatment.

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Psychedelics critical learning periods extend beyond mental health

New study findings have shown that mice respond more to the antidepressant effects of the drug ketamine when administered by men and not by women.

According to anecdotal reports and a small number of scientific reports, mice behave differently depending on which sex is handling them. The reports suggest that mice are more fearful and uptight around men and more relaxed and comfortable around women.

A team of researchers at the University of Maryland School of Medicine (UMSOM) has now shown that this behaviour does in fact impact the effects of ketamine on mice. 

In the study ‘Inconvenient truths and the usefulness of identifying unknown unknowns‘, published in the journal Nature Neuroscience, the team demonstrated that the response of mice detected in a specific region of their brain from handling by a man is essential for ketamine’s effect to work. They also identified the mechanism behind this response.

See also  Behavioural study to investigate ketamine for gambling disorder

Male vs female administration of ketamine

The researchers say that while the influence of the sex of the scientist administering ketamine is not directly relevant to the human response to ketamine, the brain mechanism underlying their findings could help determine why some people do not respond to ketamine anti-depressant therapy and suggest ways to potentially make this therapy work better for those patients who do not respond well.

Todd Gould, MD, Professor of Psychiatry at UMSOM, commented: “Our findings in mice suggests that activating a specific stress circuit in the brain may be a way to improve ketamine treatment. 

“Our thought is that you may be able to provide a more robust antidepressant effect if you combine the ketamine with activation of this brain region, either a drug that spurs this process in the brain or even some sort of specific stressor.”

Gould’s team anecdotally noticed that ketamine’s antidepressant-like effects only seemed to work consistently when male researchers administered the treatment to mice. 

The team reached out to other labs studying mouse responses to ketamine, who reported the same issues, but no one had yet systematically documented the phenomena and investigated the cause. 

At the time, most of Gould’s team members were women and so figuring out why the experiments did not work when women performed them was essential to the team getting workable data.

The team began observing mouse preference for being around t-shirts or cotton swabs rubbed on the wrists, elbow or behind the ear that came from men versus women, finding that the mice preferred spending more time around t-shirts and cotton swabs that came from women rather than men. 

When the researchers used a chemical to block the smell of the mice, they no longer preferred women’s t-shirts or cotton swabs over men’s.

“Compared to humans, mouse sense of smell and their sensitivity to pheromones (airborne hormones) are more keenly developed, so it’s not surprising that they respond differently to many smells, including those of men compared to women,” said Gould.

The team confirmed the original anecdotal findings with a systematic experiment using many researchers to verify that mice responded to ketamine when administered men, but not by women. 

Corticotropin-releasing factor

To understand the mechanism behind why the mice behave this way the researchers investigated several factors potentially involved in mediating ketamine’s response in mice – settling on corticotropin-releasing factor (CRF). 

CRF is located region of the brain, known as the hippocampus, which is responsible for learning and memory, and had previously been associated with depression. When the researchers had women administer the ketamine along with an injection of CRF, the mice finally responded to ketamine as if they were being treated with an antidepressant.

Polymnia Georgiou, PhD, a former postdoctoral fellow in Gould’s laboratory, who led the project, commented: “We think that some people may have higher or lower levels of CRF, and we believe that people do not respond well to ketamine antidepressant therapy might respond if we could administer the treatment with some CRF-related chemical that could induce ketamine’s effects,.

“Alternatively, we typically see the antidepressant effects of ketamine lasting one to three days, but with CRF administration, it is possible that we may be able to extend the effects to last longer with CRF.”

Mark Gladwin, MD, executive vice president for Medical Affairs, UM Baltimore, and the John Z. and Akiko K. Bowers Distinguished Professor and Dean at UMSOM, said: “These are exciting new findings that underscore the importance of basic research to lay the foundation for future clinical innovations. 

“Our investigators are leaders in the study of new approaches for the treatment for depression, such as ketamine.

“They also found an unexpected interaction between the sex of the mice studied and the sex of the scientist administering the drugs, highlighting the importance of evaluating unexpected effects of our experimental systems and approaches.”

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Compass, Transcend, and Usona Identified as Receivers of Priority Vouchers Following Psychedelics Executive Order

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Compass Pathways, Transcend Therapeutics, and the Usona Institute have been named the first recipients of FDA National Priority Vouchers following last week’s landmark executive order, for programs developing psilocybin and methylone, an MDMA analog.

“These medications have the potential to address the nation’s mental health crisis, including conditions like treatment-resistant depression, alcoholism and other serious mental health and substance abuse conditions,” said FDA Commissioner Marty Makary, M.D., M.P.H.

Issued by President Trump on April 18, the “Accelerating Medical Treatments for Serious Mental Illness” order directed the FDA to provide these high-value regulatory tools to designated breakthrough therapies. By securing these vouchers, the three organizations are now positioned to shave months off the typical regulatory review timeline, significantly shortening the path to commercialization for their lead candidates.

The vouchers, known as Priority Review Vouchers (PRVs), are powerful regulatory assets that grant the holder a fast-track review from the FDA by reducing the target review time from ten months to six. Originally designed to incentivize development in rare pediatric or tropical diseases, their application to psychedelics marks a strategic shift in federal policy. 

Compass Pathways appears to be the closest to utilizing this advantage. Recent Phase 3 data for its lead compound, COMP360 (synthetic psilocybin), demonstrated a “highly statistically significant” antidepressant effect in patients with treatment-resistant depression (TRD). 

The company was the first to confirm being a recipient of one of the three vouchers, via a press release published Friday.  

According to CEO Kabir Nath, the company is potentially the first to bring a classic psychedelic to market, with a rolling NDA submission already underway. Compass expects to complete its filing by the second half of 2026.

The remaining two organisations to receive the vouchers were not identified by the FDA on its release, but can be deducted from the information provided by the agency, as the only two working in late stage trials with the compounds targeted by the measure.

Transcend Therapeutics’ voucher comes at a pivotal moment in its corporate evolution. The New York-based firm was recently acquired by Japanese pharmaceutical giant Otsuka in a deal worth up to $1.2 billion, and is developing a pipeline for methylone, a non-hallucinogenic analog of MDMA. By focusing on neuroplasticity without the intense cognitive alterations associated with classic MDMA, Transcend is targeting a unique regulatory niche for PTSD. 

Finally, the Usona Institute—a non-profit medical research organization—continues its push for psilocybin as a treatment for Major Depressive Disorder (MDD). Unlike its commercial counterparts, Usona’s receipt of the voucher underscores the administration’s intent to support diverse research models, including non-profit institutes. Usona is currently conducting its “uAspire” Phase 3 trial, which evaluates a single 25mg dose of psilocybin. The voucher ensures that once Usona completes its trial work, the resulting data will receive the highest level of federal priority, ensuring that patient access is not delayed by administrative bottlenecks.

Interestingly, ibogaine was not targeted for the fast-track measure in spite of being a central protagonist of the executive order’s announcement last week by the White House.

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Europe’s Regulatory Body Signals Shift To ‘Weight of Evidence’ Model For Drug Approvals—How Does It Affect Psychedelic Medicines?

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The European Medicines Agency is taking steps to rethink how certain high-need medicines reach patients, with a new concept paper proposing a more flexible, evidence-based pathway for cancer therapies. While the focus is paediatric oncology, the implications may extend far beyond cancer, raising questions about whether similar approaches could eventually support the development of psychedelic treatments.

The “Weight of Evidence” Model

Published last month, the EMA’s concept paper outlines plans for a reflection paper on how “proof-of-concept” data should be used to guide early-stage drug development. At its core is a shift away from rigid data requirements toward a “weight of evidence” model, where regulators assess the totality of available data, including non-clinical studies, early clinical signals, and biological rationale.

This approach is already gaining traction in oncology, particularly in paediatric settings where patient populations are small and traditional large-scale trials are often unfeasible. In such cases, regulators are increasingly willing to rely on mechanistic understanding and preclinical evidence to justify moving into clinical trials earlier, provided there is a strong scientific rationale and unmet medical need.

The EMA’s concept paper emphasises that development decisions should be grounded in several key domains, including mechanism of action, disease biology, pharmacology, and safety, as well as the broader clinical context. Rather than requiring exhaustive datasets upfront, the agency is signalling openness to iterative development, where evidence is built progressively and regulatory decisions evolve alongside the data.

For the psychedelics field, this raises a clear question: could a similar framework accelerate the path to approval?

A shift toward mechanism-of-action–based regulation in psychedelics could, in theory, reduce the need to pursue separate approvals for each diagnostic category, such as depression or PTSD, by anchoring use to a shared underlying biology.

If regulators accept that psychedelic therapies exert their primary effect through defined pathways, for example 5-HT2A receptor activation leading to increased neuroplasticity and network-level brain changes, then the relevant treatment population could be framed around patients exhibiting that dysfunction rather than a specific DSM label. In this model, a single approval could cover multiple conditions where the same mechanism is implicated, provided there is sufficient evidence linking that pathway to clinical benefit across those populations.

This would shift development away from duplicative, indication-by-indication trials toward demonstrating consistent mechanistic effects and reproducible outcomes in biologically defined subgroups.

There are other parallels between the regulatory paths described in the paper and psychedelics. Psychedelic therapies are often being developed for conditions where unmet need remains high and patient populations can be difficult to study using conventional trial designs. Like paediatric oncology, these indications may benefit from more flexible approaches that incorporate multiple forms of evidence.

However, important differences remain.

Oncology drug development is underpinned by well-established biological models and biomarkers, allowing regulators to link mechanism of action to clinical outcomes with a relatively high degree of confidence. In contrast, the mechanisms underlying psychedelic therapies are still being defined, spanning pharmacological effects, neural network changes, and the subjective therapeutic experience itself.

The EMA’s framework places significant weight on the relevance and reliability of non-clinical models, an area where psychedelics currently face limitations. Translating findings from animal studies to complex psychiatric outcomes in humans remains a challenge, and there is no widely accepted biomarker that can serve as a proxy for therapeutic response.

Endpoints also differ. Cancer trials can rely on objective measures such as tumour progression or survival, whereas psychedelic studies typically depend on subjective scales and patient-reported outcomes. This makes it more difficult to integrate different sources of evidence into a unified regulatory decision.

Even so, the direction of travel is notable. By formalising a weight-of-evidence approach and emphasising mechanism-driven development, the EMA is signalling greater flexibility in how innovative therapies are assessed. If these principles are applied more broadly across therapeutic areas, they could eventually lower some of the structural barriers facing psychedelic drug development.

For now, the concept paper remains focused on oncology, and significant scientific and regulatory hurdles would need to be addressed before such a model could be extended to psychedelics. But as regulators continue to adapt to emerging forms of medicine, the boundaries between therapeutic areas may become less rigid.

In that context, the EMA’s latest move may not just reshape cancer drug development, but also offer an early glimpse of how the next generation of psychiatric treatments could be evaluated.

Picture: EMA headquarters in Amsterdam. Courtesy of EMA.

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Quit Smoking: Psilocybin Found To Be 6 Times More Effective Than Nicotine Patches

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A new clinical trial has found that psilocybin-assisted therapy may be better at helping people stop smoking than standard nicotine replacement treatment.

The results were published on March 10, 2026 in the journal JAMA Network Open. Researchers from Johns Hopkins University and University of Alabama at Birmingham conducted a randomized clinical trial comparing a single psilocybin session combined with therapy to nicotine patch treatment with the same therapy program.

Smoking remains one of the leading causes of preventable disease and death worldwide. While existing treatments such as nicotine replacement therapy can help some people quit, long term success rates are often limited. The study aimed to test whether a psychedelic assisted approach could improve those outcomes.

The Trial

The trial included 82 adults who smoked tobacco daily and wanted to quit. Participants were randomly assigned to one of two groups. One group received a program built around a single high dose of psilocybin alongside structured psychological support. The other group received nicotine patches together with the same therapy sessions.

Both groups took part in a 13 week cognitive behavioral therapy program designed to help people stop smoking. This allowed researchers to compare the effect of psilocybin directly against the standard nicotine patch treatment while keeping the psychological support constant.

Participants in the psilocybin group took one oral dose of the compound, calculated at 30 milligrams per 70 kilograms of body weight. The session took place in a controlled setting with trained guides present. The experience was integrated into the broader therapy program, which included preparation sessions before the dose and follow up meetings afterwards.

Six months after treatment, the difference between the two groups was clear: around 40.5 percent of people who received psilocybin were able to remain abstinent from smoking. In the nicotine patch group, 10 percent achieved the same result.

This means that the group receiving psilocybin treatment was six times more likely to not pick up smoking at six months from the initial treatment date.

Researchers used biological tests to confirm whether participants had stopped smoking. These tests measured markers in breath and blood that indicate tobacco use. This approach allowed the team to verify the results rather than relying only on self reported behavior.

The authors note that smoking cessation is a difficult challenge for many people, even when treatment is available. Relapse is common, and many smokers attempt to quit several times before succeeding. The study suggests that psychedelic assisted therapy may offer a new approach by combining psychological support with a single powerful therapeutic experience.

However, the researchers also describe the trial as a pilot study. The relatively small number of participants means that larger studies will be needed to confirm the findings and better understand how the treatment works.

Several psilocybin therapies are advancing through the clinical pipeline regulated by the U.S. Food and Drug Administration. The most advanced programs target treatment resistant depression and major depressive disorder in late stage trials. Earlier studies are exploring psilocybin for post traumatic stress disorder, alcohol use disorder and anxiety or depression associated with life threatening illnesses.

If the results of the nicotine trail are replicated in larger trials, psilocybin assisted therapy could also become part of a new generation of treatments for tobacco dependence. The approach differs from traditional medications by focusing on psychological change during a guided therapeutic session rather than daily drug use.

For now, the study provides early clinical evidence that psilocybin combined with therapy may significantly improve smoking cessation outcomes compared with one of the most widely used existing treatments.

Image made using AI tools.

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