Addex & Neurosterix Push NTX-253 Toward Phase 1 Readout

Addex & Neurosterix Push NTX-253 Toward Phase 1 Readout

By, Admin 27 April 2026

A quiet but important milestone is approaching in CNS drug development. Addex Therapeutics announced that its spin-out, Neurosterix, is on track to complete its Phase 1 clinical study of NTX-253 by Q2 2026.

This isn’t just another early-stage trial. The design signals a deliberate attempt to de-risk one of pharma’s hardest therapeutic areas.

Why This Matters?

Schizophrenia therapies still rely heavily on dopamine receptor antagonism. That works—but imperfectly:

  • Controls positive symptoms (hallucinations, delusions)
  • Triggers side effects:
    • Movement disorders
    • Metabolic issues
    • Cognitive dulling

NTX-253 is targeting a different pathway altogether.

The Mechanism Bet

NTX-253 is a positive allosteric modulator (PAM) of the muscarinic M4 receptor. Here’s the thesis:

  • M4 indirectly regulates dopamine signaling
  • Modulation (not direct activation) = finer control
  • Goal: antipsychotic effect without classic side effects

In theory, this could:

  • Reduce psychosis symptoms
  • Avoid motor and metabolic complications
  • Improve tolerability and adherence

That’s the upside.

The risk? This mechanism has looked promising in preclinical models before—but human translation remains the real test.

The Trial Design

Instead of a basic safety study, this trial is structured to extract maximum early insight.

Part 1: Single Ascending Dose (SAD)

  • Healthy volunteers receive escalating single doses
  • Includes:
    • Food-effect cohort (impact on drug absorption)
    • CSF cohort → measures brain penetration

That last point matters. Many CNS drugs fail because they don’t reach the brain effectively.

Part 2: Multiple Ascending Dose (MAD)

  • Daily dosing for 10 days
  • Sequential dose escalation
  • Evaluates:
    • Safety
    • Tolerability
    • Steady-state pharmacokinetics

But here’s the twist:

  • Includes patients with stable schizophrenia
  • Antipsychotics withdrawn for up to 8 days

This is unusually aggressive for Phase 1.

Why it matters:

  • Early signal in real patients
  • Faster transition into later-stage trials
  • Higher risk if safety signals emerge

A Built-In Acceleration Strategy

CEO Tim Dyer framed it clearly: Combine healthy volunteer and patient data in one program, compress timelines and reduce uncertainty

This is essentially:

  • Phase 1 + early proof-of-concept hybrid
  • Fewer blind spots going into Phase 2

Smart design—if it works.

The Spin-Out Strategy

Neurosterix isn’t just a side project.

  • Spun out in April 2024
  • Raised $65 million Series A
  • Backed by Perceptive Advisors
  • Addex retains ~20% equity

Translation:

  • Risk is partially externalized
  • Upside remains intact

Classic biotech capital strategy.

The Bigger Scientific Context

The M4 muscarinic receptor is increasingly seen as a viable target because:

  • It modulates dopamine indirectly
  • Avoids peripheral side effects of direct muscarinic agonists
  • Has shown strong antipsychotic-like activity in preclinical models

If validated in humans, this could reshape how schizophrenia is treated. But that “if” is doing heavy lifting.

What to Watch Next?

As Q2 2026 approaches, focus on:

  • Safety signals → any CNS or systemic red flags
  • PK data → does exposure match expectations?
  • CSF penetration → critical for CNS credibility
  • Patient cohort response → early efficacy hints

Because here’s the uncomfortable reality: Most CNS drugs fail not because the idea is bad—
but because biology doesn’t cooperate in humans.

Bottom Line

Addex and Neurosterix are making a calculated bet:

  • New mechanism (M4 PAM)
  • Aggressive Phase 1 design
  • Early patient inclusion

If NTX-253 delivers clean safety and strong brain exposure data, it could quickly become a high-interest CNS asset. If not, it joins a long list of promising neuroscience ideas that didn’t survive first contact with humans.

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