In late October, Biogen announced plans to revive its Alzheimer's program following a new analysis conducted by the company in consultation with the FDA. The analysis was based on a larger dataset from two Phase 3 studies dubbed EMERGE and ENGAGE, which the company had discontinued in March following failed futility analysis.
Biogen said it plans to make a regulatory submission by mid-2020. The October disclosure was short on details, and therefore investors sought more clarity from the CTAD presentation.
Similar Studies, Contrasting Outcomes
At Thursday's CTAD presentation, Biogen said only 29% of patients in EMERGE and 22% of patients in ENGAGE received the full possible 14 doses of 10mg/kg doses.
Larger dataset from the EMERGE trial at week 78, as well as the final dataset, showed statistically significant improvement in Clinical Dementia Rating-Sum of Boxes, or CDR-SB, which is the primary endpoint.
The study also met the secondary endpoints, as measured by Mini-Mental State Examination, or MMSE, Alzheimer's Disease Assessment Scale-Cognitive Subscale, or ADAS-Cog 13.
However, the ENGAGE trial did not show promising results in all these measures, giving rise to doubts as to why two identical studies are diverging in the efficacy outcomes.
On safety, the company said 34% of those received high dose experienced amyloid-related imaging abnormalities in the EMERGE study compared to 25.7% of those who received the low dose. The safety result was almost similar in the ENGAGE study.
Biogen apparently was projecting the mixed results as a corollary of the difference in dosing regimen.
Call For Confirmatory Trial Gets Louder
With the detailed results not throwing up any further negatives, the stock moved higher. That said, clinicians and researchers are calling for an additional trial to clarify things further. Dr. Adam Kline, an Alzheimer's researcher, said in a tweet a confirmatory trial is needed.
Two essentially identical studies. One showed efficacy, one did not. Sub-group analysis afterwards is suggestive but not conclusive. Another, confirmatory study needed surely?
— Dr. Adam D. Kline (@DrADKline) December 5, 2019
"We walk away from this presentation in about the same place as we were before. Perhaps we would like to see some more on safety and conduct checks to understand the clinical relevance or ARIA-events," Cantor Fitzgerald analyst Alethia Young wrote in a note.
The analyst said a potential FDA panel is going to be the key vetting point. The analyst assumes a 30% probability of success for aducanumab and $2.4 billion in unadjusted sales in 2026.
At least for the time being, Biogen seems to have appeased investors, as evidenced by the post-presentation rally in the stock. Biogen shares traded up 3.8% to $300.69 per share at time of publication.
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