Roche-backed AC Immune finds even mixed-bag Alzheimer's data are enough to make shares explode

When it comes to Alzheimer's disease, even a scrap of good news from a clinical trial can elevate a company at the markets. Roche-backed AC Immune is learning that lesson in real time today. 

Semorinemab has shown the first clinical evidence of a tau-targeting monoclonal antibody in patients with mild to moderate Alzheimer’s disease in a phase 2 study, Roche’s Genentech and AC Immune said Tuesday. The therapy reduced the rate of cognitive decline, meeting one of the co-primary endpoints of the study.

But it wasn't all good news; semorinemab failed to lower the rate of functional decline, which was the second co-primary goal. In fact, it flopped all of its secondary goals, which include an assessment of cognitive function based on orientation, attention, memory, language and visual-spatial skills as well as a ranking of dementia severity. Genentech said it plans to examine biomarker data from the study to better understand the results.

“Although we are encouraged by the positive outcome for one co-primary endpoint measuring cognitive performance, we will continue our analyses of these data and continue the open label portion of the study to better understand why semorinemab didn’t show an effect on the co-primary endpoint measuring functional decline in activities of daily living, or on the secondary endpoints,” said Rachelle Doody, M.D., Ph.D., Roche’s global head of neurodegeneration.

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Despite the mixed results, shares of AC Immune rose dramatically 73% in premarket trading to $12.15. This compares to a prior close of $6.99 the day before.

AC Immune CEO Andrea Pfeifer, Ph.D., called the results “remarkable” given they are a first for the anti-tau field. Many of the results from recent Alzheimer’s therapies have focused on the amyloid theory.

Alzheimer’s is not well understood, but the current thinking is that abnormal proteins called beta amyloid clump together in the brain and disrupt cell function. Another protein, called tau, strings together in the part of the brain involved in memory and forms tangles inside neurons, blocking the communication between the cells. When amyloid builds up into plaques, it pushes the tau throughout the brain.

Drug developers believe that if they can clear these plaques or the tau tangles, they could address the underlying cause of Alzheimer’s.

RELATED: 'Let the games begin': Reinvigorated Alzheimer's pipeline breaches the levee with planned Lilly filing, Bristol Myers opt-in

Pfeifer is rightfully cautious about what these initial results mean for the therapy.

“Despite these interesting results, we are still cautious about what this may mean for patients as there was not an impact on the rate of functional decline or other efficacy endpoints,” she said.

Pfeifer noted that the trial timeline was relatively short, so a longer time frame in the open-label extension could better showcase semorinemab’s potential.

“Scientifically, these data are encouraging for the therapeutic strategies targeting tau,” she said.

The top-line results will be submitted for presentation at the Clinical Trials on Alzheimer's Disease conference in November, AC Immune said.

RELATED: Lab named by Cassava to back up Alzheimer's data says it wasn't involved, sending biotech's shares into freefall again

AC Immune has multiple partnerships with major pharmaceutical companies including Roche, Eli Lilly and Johnson & Johnson’s Janssen unit worth up to $3 billion in potential milestones.

Not a lot of good news has come from the Alzheimer’s pipeline in recent weeks after the approval of Biogen’s Aduhelm reinvigorated the sector back in June. AC Immune's good news comes after a week of controversy from competitor Cassava Sciences, which has been accused of data manipulation in an Alzheimer's trial by a whistleblower petition. Last month, Annovis presented failed data from a small phase 2a study for the biotech's candidate Posiphen.

AC Immune's other partner Lilly, however, presented some encouraging biomarker data in July.