Will Another Alzheimer's Disease Drug Bite the Dust After Lilly's Latest Results?

There's a pressing need for safe and effective treatments for Alzheimer's disease. However, there haven't been many successes after years of research and development. Eli Lilly (LLY -1.00%) recently became the latest to disappoint with mixed results from a phase 2 study of donanemab. In this Motley Fool Live video recorded on March 17, Motley Fool contributors Keith Speights and Brian Orelli discuss whether or not yet another Alzheimer's disease drug could bite the dust after Lilly's results.

Keith Speights: All right, so let's switch to a non-COVID-19 topic. So on Monday, Eli Lilly, ticker there is LLY. Lilly announced results from a phase 2 study of an experimental Alzheimer's disease drug called, I hope I pronounce this right, donanemab. So while the drug met its primary endpoint, which was improvement on a scale called the Integrated Alzheimer's Disease Rating Scale, or iADRS it didn't achieve the secondary endpoint on another scale, the Clinical Dementia Rating Scale Sum of Boxes, or CDR-SB.

So it's mixed results here, Brian. Met the primary endpoint, didn't meet the secondary endpoint. What do you think investors should make of Lilly's results?

Brian Orelli: This is the full data, and we got the top-line results in a press release in January. This is the old adage for drug companies, the devil's often in the details. On the iADRS scale that you mentioned, they had a 6.86 point decline for patients on the drug compared to 10.06 decline for patients on placebo. So that was statistically significant with a p-value of 0.04. That basically means that there is a 4% likelihood that the difference happened by chance alone and the FDA usually sets that at 5%. So they just barely missed making that level.

But of course, this is a pretty small phase 2 study, with a much larger phase 3 study, even with that difference, the statistics will go way down. If you can think of like flipping a coin, if you flipped it ten times and you ended up with seven heads, you might say, well, that's probably due to chance. If you flipped it 1,000 times and had 700 heads, now you're thinking, well maybe that there's something rigged about this coin or there's more likely to be heads than tails.

The big question here is, although it's statistically significant is it clinically meaningful? This iADRS combines two other scores, ADAS-Cog and ADCS-iADL but it hasn't been used enough from what I can gather, to know whether this is clinically meaningful.

The CDR sum of boxes is a much more validated study. But as you said, the drug didn't help on that scale. Eli Lilly's running another phase 2 that uses CDR sum of boxes as the primary endpoint with the iADRS as a secondary endpoint.

My head hurts just considering the possibility of how we're supposed to understand this based on the second data. If the sum of boxes hits on the second one then what does Lilly do for the phase 3? What do they use for the phase 3 because they got one that hit and one that didn't? Then if the iADRS hits, then Eli Lilly can use it or be convinced that maybe it'll work in phase 3, but they've got to convince the FDA that it's a valid endpoint.

Alzheimer's disease is an area that I avoid at all costs. Because I just feel like it's too hard to figure out whether drugs are going to work or not. I just avoid them at all costs. But even if you can't necessarily avoid them.

Even you would think a company like Eli Lilly is so large that maybe it wouldn't really affect them but they went down 9% on the news. I think that's mostly just because Alzheimer's is such a big opportunity. That even if it's not a 100% priced in, even if it's 10% priced in, then the loss of that 10% is enough to drive down the stock price.

Speights: You're exactly right on just the landscape is just littered with Alzheimer's disease drug failures, unfortunately. It reminds me of the Peanuts cartoon where Charlie Brown -- he wants to kick the football, Lucy holds it, and every single time she yanks it away. That seems to be the story with Alzheimer's disease drugs.

We have some big news on the way with Biogen -- ticker is BIIB -- hoping to win FDA approval for an Alzheimer's disease drug. I've learned not to even get my hopes up in this particular category.

Orelli: I think it's really just too hard to figure out. I mean, I'm rooting for all of them but I'm not going to invest in them.

Speights: Exactly. I had a grandparent who suffered from Alzheimer's disease. We really need an effective treatment for it. But just so far drugs just strike out left and right. Hopefully, if it's not Eli Lilly or Biogen, hopefully some company will succeed in the near future.