Addex's New Drug Offers Hope for Chronic Cough Without Side Effects

GENEVA, Switzerland – April 21, 2026 – Addex Therapeutics, a clinical-stage biopharmaceutical company, announced a significant step forward in the quest for a better treatment for chronic cough, a condition that affects millions worldwide. The company revealed that its novel drug candidate demonstrated robust effectiveness in a preclinical chronic cough model using non-human primates, a key step in predicting human outcomes.

The announcement brings a new contender into the race to solve a persistent medical problem, offering a potential alternative to existing off-label treatments that are often hampered by debilitating side effects.

A Persistent Problem in Search of a Solution

Chronic cough, defined as a cough lasting eight weeks or longer, is far more than a simple annoyance. It is a debilitating condition that severely impacts quality of life, leading to exhaustion, sleep deprivation, social isolation, and depression. As one of the most common reasons patients seek specialist medical care, it represents a significant burden on healthcare systems globally.

The market for chronic cough treatments is substantial, valued at over $6 billion and projected to grow to more than $9 billion by 2032. This market size reflects a vast unmet need. The global prevalence of chronic cough is estimated to be around 9.6%, with rates in Europe and the Americas exceeding 10%. Despite this, there are no FDA-approved treatments specifically for refractory chronic cough, leaving physicians and patients to rely on off-label options.

Current treatments are often ineffective or come with a heavy price in the form of side effects. This has created a pressing need for novel therapies that can provide relief without compromising a patient's ability to function day-to-day.

Moving Beyond Baclofen's Limitations

For years, a muscle relaxant called baclofen has been used off-label to treat severe chronic cough. It works by activating GABAB receptors, which are found throughout the neural pathways that control the cough reflex. While its effectiveness is clinically validated, baclofen's utility is severely limited.

The drug is notorious for causing significant central nervous system side effects, including drowsiness, dizziness, and fatigue. In one study, 35% of patients reported somnolence, leading many to discontinue treatment. Furthermore, baclofen has a short half-life, requiring multiple daily doses, and patients can develop a tolerance over time, leading to a gradual loss of efficacy.

This is the challenge Addex aims to solve. "Chronic cough is a difficult to treat disease in need of novel therapeutics with the efficacy of baclofen... but without the dose limiting side effects," said Tim Dyer, CEO of Addex, in a statement. "Based on the data generated to date, we believe our GABAB PAM drug candidate has this therapeutic profile."

The Promise of Allosteric Modulation

Addex’s drug candidate is a GABAB positive allosteric modulator (PAM). Instead of directly activating the GABAB receptor at its main "orthosteric" binding site like baclofen does, it binds to a secondary "allosteric" site. This acts like a dimmer switch rather than an on/off button, subtly enhancing the receptor's response to the body's natural neurotransmitter, GABA.

This mechanism is key to its potential advantages. By fine-tuning the receptor's activity rather than forcing it on, allosteric modulators can offer higher selectivity and a much better side-effect profile. The company believes this approach will avoid the development of tolerance seen with drugs like baclofen.

The latest data from the non-human primate model showed that Addex's GABAB PAM significantly reduced cough frequency, with efficacy similar to baclofen. This result in a higher-order animal model is a crucial validation. It builds on previous studies in guinea pigs where the drug candidate not only reduced cough frequency but appeared superior to baclofen, codeine, and even a P2X3 inhibitor, another class of emerging cough therapies. Importantly, the GABAB PAM showed a wider therapeutic margin and better tolerability than the older drugs.

Navigating a Competitive and Evolving Market

Addex is not alone in the pursuit of a blockbuster chronic cough drug. The field is highly competitive, dominated by a class of drugs known as P2X3 inhibitors. Merck’s gefapixant, a P2X3 inhibitor, is already approved in Europe and Japan, establishing a new standard of care. Bellus Health, recently acquired by GSK, is also a major player in this space.

However, the P2X3 inhibitor class is not without its own challenges, most notably taste-related side effects that can be bothersome for patients. This leaves the door open for alternative mechanisms of action, like Addex’s GABAB PAM, to carve out a significant share of the market, provided they can demonstrate a superior or differentiated profile. The market is large enough to support multiple successful drugs with different mechanisms, especially given the diverse underlying causes of chronic cough.

For Addex, a micro-cap company with a market capitalization of just over $8 million, the positive preclinical data is a vital lifeline. The company has seen its cash reserves shrink and its stock has languished over the past year. This robust anti-tussive data provides a much-needed potential catalyst and a clear path forward for one of its key independent programs.

The next step is to advance the drug candidate into IND-enabling studies, the final stage of preclinical work required before seeking regulatory permission to begin human trials. While the journey from a promising molecule to an approved medicine is long, expensive, and fraught with risk, this latest development marks a critical milestone. For the millions suffering from chronic cough, the progress of Addex's candidate from the lab to the pharmacy will be one to watch closely as the company prepares to navigate the rigorous path of clinical development.