Our pipeline

YSOPIA Bioscience’s game-changing strategy is built around developing living single-strain biotherapies based on carefully selected keystone bacteria.

> Discover our approach



Yso1 is a clinical-stage development program harnessing the potential of Christensenella gut bacteria to treat metabolically unhealthy obesity. Our flagship oral biotherapy Xla1 is based on a unique living bacterial strain naturally present in a healthy human gut microbiome: Christensenella minuta.

After demonstrating strong efficacy results in preclinical animal models, YSOPIA successfully completed the Phase 1 clinical study for its Xla1 biotherapy in July 2021 and demonstrated its excellent safety and tolerability profile, as well as first efficacy results.

Following this success, YSOPIA is preparing to launch a Phase 2 clinical trial to establish the first proof of concept for Christensenella’s efficacy in humans in treating obesity and its associated metabolic abnormalities.

This is built on our seminal work published in Cells (Mazier et al. 2021) demonstrating in vivo that our clinical candidate Xla1 limits body weight gain and normalizes several metabolic markers. 

  • Unmet needs in obesity
    Obesity is a growing pandemic affecting the entire population, including a disturbing proportion of children. By 2025, 1 billion people will be living with obesity and there is currently no cure. There is an urgent need to find a safe, effective treatment for obesity.


Yso2 is a preclinical program targeting Crohn’s disease. It aims to develop Christensenella gut bacteria as a safe, efficient and groundbreaking oral biotherapy.

YSOPIA has demonstrated the potent immunomodulatory properties of Christensenella both in vivo and in vitro, and underscored its potential for use in innovative microbiome-based IBD biotherapies.

Discover our work published in Scientific Reports (Kropp et al. 2021). Our team has selected from our proprietary strain library a lead candidate with strong in vitro and in vivo data package that makes it highly promising for human clinical studies.

  • Unmet needs in Crohn’s disease
    Crohn’s disease is a global burden affecting millions of patients, half of whom fail to achieve complete remission or face treatment failures and medical complications. Although no current treatments address the root causes of the disease, a growing body of scientific evidence points to the fundamental role of the gut microbiome in the development, progression, and treatment of IBD.


Yso3 is a preclinical drug development program aimed at treating asthma. Using a revolutionary form of living biotherapy targeting the lung, YSOPIA is pioneering the innovative field of the lung microbiome.

As part of this program, YSOPIA has selected a clinical candidate having demonstrated strong in vivo efficacy on inflammation and lung functions.

We have achieved the formulation feasibility and cleared the regulatory hurdles associated with developing this new biotherapy. Continue our development plan to the clinical phase is the further step for this program.

  • Unmet medical needs in asthma
    Asthma is one of the most common chronic diseases, with more than 339 million people living with asthma worldwide. Asthma is incurable, but manageable. The current standards of care do not resolve long-term disease and often have significant side effects. People with ongoing symptoms often need to take medication daily for their entire lives.


Yso4 is an exploratory program targeting the gut-brain axis for the treatment of mood disorders.

Over the last 5 years, there has been increasing evidence that the gut microbiome is associated with neurological and behavioral disorders, in what is known as the “gut-brain axis”.

Multiple complex mechanisms of action are at play in this relationship, and although there is still much to discover, there is strong evidence that the gut microbiome affects neurotransmitter metabolism and neuroinflammation.

YSOPIA Bioscience has therefore launched research in this exciting area to harness the potential of carefully selected bacteria strains of Christensenellaceae to treat mood disorders such as depression and anxiety.

  • Unmet needs in mood disorders
    According to the World Health Organization, depression affects 322 million people worldwide, while the total number of people living with anxiety disorders is estimated at 264 million.
    Only 50% of eligible patients receive some form of treatment​. 60% to 70% of these treated patients respond to antidepressant therapies, but many of them are associated with multiple side effects.


Yso5 is a discovery-stage program leveraging a specific keystone gut bacteria (undisclosed) to potentiate the effects of Immune Checkpoint Blockade (ICB) drugs.

The field of cancer therapy has been revolutionized by the use of immunotherapy. The microbiome breakthrough science today paves the way for innovative biotherapies to potentiate the effectiveness of these cancer immunotherapies.

YSOPIA is exploring the role of specific keystone bacteria with high therapeutic potential in the oncology field based on a strong understanding of their mechanisms of action.

  • Unmet needs in immuno-oncology
    Immune checkpoint blockade (ICB) drugs have revolutionized cancer care with durable responses in patients​. However, their wider use is hindered by an inability to predict efficacy and patient response.
Microbiome & us
Jan 20, 2022
Alliance Promotion Microbiote devient une Association et poursuit la structuration de la filière française du...
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Dec 2, 2021
YSOPIA Bioscience Announces First Signs of Biological Activity from Phase I Analysis of Xla1, its Biotherapy Targeting...
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Press / Media
Dec 3, 2021
Access the full article  
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Dec 3, 2021
YSOPIA Bioscience annonce des premiers signes d’activité biologique suite à l’analyse des résultats de l’étude...
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Nov 1, 2021
We are pleased to present our poster highlighting safety and first efficacy results of our Xla1 biotherapy targeting...
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Sep 1, 2021
Héloïse Tudela, Sandrine P. Claus and Maya Saleh Access the full paper The community of the diverse microorganisms...
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now on twitter
YSOPIA Bioscience

On January 26th - 1,50pm, our CSO Sandrine Claus will be presenting the results of our latest research on Christens… t.co/FD0xMEojxr

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