ABX-002 Phase 1 Cleared, But Undisclosed Mechanism Leaves MDD Differentiation Case Entirely Unbuilt

Autobahn Completes ABX-002 Phase 1 Dosing for MDD

Autobahn Therapeutics announced the completion of dosing in its Phase 1 study of ABX-002 for Major Depressive Disorder (MDD). The study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of ABX-002 in healthy volunteers, showing it was generally well-tolerated with a favorable exposure profile. Topline data is expected in Q4 2023, with plans to initiate a Phase 2 trial in MDD patients in H1 2024. The company also promoted Gudarz Davar, M.D., to Executive Vice President, Head of Research and Development, and is advancing ABX-101, a brain-penetrant S1P receptor modulator, toward Phase 1 development for neuroinflammatory disorders.

• Autobahn Therapeutics has successfully completed dosing in its Phase 1 single- and multiple-ascending dose study for ABX-002, a novel, orally administered, potent, and selective thyroid hormone beta (TRβ) agonist. The study in healthy volunteers demonstrated that ABX-002 was generally well-tolerated with a favorable exposure profile, supporting its continued development. Topline data from this Phase 1 study is anticipated in the fourth quarter of 2023, with an Investigational New Drug (IND) application planned for submission to the FDA to enable a Phase 2 clinical trial in Major Depressive Disorder patients in the first half of 2024.
• The company has declared ABX-101 as its third development candidate, a next-generation, brain-penetrant, oral sphingosine 1-phosphate (S1P) receptor modulator. Preclinical models have shown robust CNS exposure and effectiveness for ABX-101 in neuroinflammation. Autobahn plans to progress ABX-101 through IND-enabling studies in 2024, with the goal of advancing it into Phase 1 clinical development for a range of neuroinflammatory disorders, leveraging its FAAH-mediated brain-targeting prodrug platform.
• Autobahn Therapeutics has strengthened its senior leadership team with the promotion of Gudarz Davar, M.D., to Executive Vice President, Head of Research and Development. Dr. Davar, an accomplished neurologist and neuroscientist, will lead the charge in advancing the company's brain-targeting chemistry platform. This move underscores Autobahn's commitment to its mission of developing restorative treatments for CNS disorders, with two key assets (ABX-002 and ABX-101) progressing rapidly through clinical and preclinical stages.

The Unmet Need for New Options in Major Depressive Disorder

Current treatment approaches for Major Depressive Disorder face substantial efficacy and tolerability gaps that leave a significant proportion of patients without adequate relief. Approximately 60–70% of patients have shown a lack of effectiveness and tolerability with antidepressant therapy, and conventional treatments are characterised by a significant time to onset of therapeutic action of approximately 2 weeks, with one-third of subjects failing to achieve stable remission.

• High rates of treatment resistance: The STAR*D study demonstrated that remission rates decline progressively with each antidepressant failure — 37%, 31%, 14%, and 13%, respectively — with approximately 30% of patients treated for MDD developing treatment-resistant depression (TRD).

• Delayed onset of action: Monoaminergic antidepressants have a delayed onset of action, meaning patients may endure weeks of inadequate symptom control before a treatment's effectiveness — or lack thereof — can be determined, prolonging suffering and complicating clinical decision-making.

• Absence of reliable predictive biomarkers: Although DNA methylation levels of serotonin transporter (SLC6A4) and tryptophan hydroxylase 2 (TPH2) genes have been suggested to predict antidepressant clinical outcomes, findings indicate they are unlikely to prove useful as clinical predictor tools. EEG-based machine learning approaches have shown promise, predicting response to Sertraline or Placebo with more than 80% accuracy, but these remain investigational.

• No clear guidance on next-step strategies after initial failure: For patients failing initial antidepressant treatment, neither augmentation nor switching has demonstrated a clear superiority — likelihood of remission, response, and time to remission did not differ by treatment strategy in the STAR*D trial — leaving clinicians without definitive evidence-based direction.

• Safety and tolerability concerns with novel rapid-acting agents: Ketamine produces rapid antidepressant effects at sub-anesthetic doses via NMDA receptor blockade, but long-term safety must be taken into consideration, as it carries abuse potential and is associated with psychological side effects such as dissociative or psychotomimetic effects.

Advancing CNS Therapies: Autobahn's Strategic Push in MDD and Neuroinflammation

Autobahn Therapeutics is strategically advancing a dual-pronged pipeline, targeting two distinct yet equally challenging areas within central nervous system (CNS) disorders: Major Depressive Disorder (MDD) and neuroinflammatory conditions. The completion of Phase 1 dosing for ABX-002 in healthy volunteers for MDD represents a critical step forward. Given the limitations of current antidepressant therapies, which often have delayed onset and insufficient efficacy for many patients, the exploration of novel glutamatergic modulators like ABX-002 is paramount. Research indicates that dysfunction in the glutamatergic system plays a role in mood disorders, and agents targeting this pathway could offer rapid symptom reduction, a significant advantage over existing treatments.

Simultaneously, the company is pushing ABX-101, a brain-penetrant S1P receptor modulator, towards Phase 1 for neuroinflammatory disorders. The S1P receptor pathway is a well-validated target in autoimmune and neuroinflammatory diseases, with several S1P modulators already approved for conditions like multiple sclerosis. The strategic focus on a brain-penetrant and potentially selective S1P modulator suggests an aim to improve upon the safety and efficacy profiles of earlier, less selective agents, which have been associated with adverse events such as cardiac effects. This approach could lead to a more targeted therapeutic option with a better tolerability profile.

However, both development paths come with inherent risks:

• For ABX-002, while glutamatergic modulation is exciting, many novel agents in this class have demonstrated only modest effects compared to established rapid-acting antidepressants, setting a high bar for clinical success and differentiation.

• For ABX-101, despite the established mechanism, careful monitoring for potential S1P-related adverse events, particularly cardiac effects or rapid disease reactivation upon discontinuation, will be crucial.

The company's recent leadership promotion in R&D underscores a commitment to navigating these complex therapeutic landscapes. By pursuing both novel glutamatergic modulation for MDD and refined S1P modulation for neuroinflammation, Autobahn is positioning itself to address significant unmet needs, but success will hinge on demonstrating clear efficacy and a favorable safety profile as these candidates progress through clinical development.