Atara Therapeutics has released data from its Phase 1 open-label extension (OLE) trial of ATA188, a treatment for progressive multiple sclerosis (MS). This allogeneic T-cell immunotherapy targets B cells and plasma cells that have been infected with Epstein-Barr virus (EBV). It also addresses a severe unmet medical need, as patients with the progressive form of MS have minimal treatment options.

Updated Data

18 patients continued into the open-label extension portion of the trial, all of whom had previously been treated with ATA188 for 12 months. These participants were then followed for up to 39 more months. As of August, nine patients achieved sustained disability improvement (SDI). Further trial data includes:

• Seven of these nine patients experienced sustained improvement on the Expanded Disability Status Scale (EDSS)
• Higher dosages related to increasing clinical response
• Eight patients who achieved SDI in the initial 12-month trial went on to maintain SDI during all time points of the OLE
  • The media duration of this maintained response was 18 months
  • One patient chose to leave the study after experiencing a relapse unrelated to treatment
• No observed cytokine release syndrome, fatal adverse events, adverse events above grade three, graft vs. host disease, or dose-limiting toxicities

Alongside data from the OLE trial, Atara also released translational data that’s based on magnetization transfer ratio (MTR). MTR is a useful biomarker when studying the loss or repair of myelin. This data demonstrated that:

• Those who saw sustained EDSS improvement also saw a significant increase in MTR from baseline for non-enhancing T2 chronic brain lesions after one year
  • Those without sustained EDSS improvement saw no change in MTR from baseline
  • This correlation between sustained EDSS improvement and increases in MTR was observed throughout the trial
  • This could suggest remyelination

Looking Forward

For the next stage in development, Atara is enrolling participants for their Phase 2 EMBOLD trial. Progressive multiple sclerosis patients from America and Australia will take part in this randomized, placebo-controlled trial.

About MS

Multiple sclerosis is a rare neurological disorder that occurs when the myelin sheath, the protective covering of nerve cells, is damaged. This damage impacts communication between the brain and body, causing symptoms such as:

• Weakness
• Numbness
• Loss of balance
• Loss of coordination
• Issus with bladder control
• Vision problems
• Issues with speech

These symptoms can appear in episodes or remain consistent depending on the form of MS one has. The two major forms are relapsing/remitting and progressive, the first of which is characterized by episodes of active symptoms followed by periods of remission. The progressive form sees constant symptoms. ATA188 is intended to treat progressive MS. Currently, there is no cure for either form of MS, but relapsing/remitting MS has more treatment options than the progressive form.

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