Trials in Alzheimer's Disease: The Long Road Ahead

Placebo Control is going purple today in support of Alzheimer’s Action Day.

A couple of clinical trial related thoughts on the ongoing struggle to find even one effective therapy (currently-approved drugs show some ability to slow the progression of AD, but not to effectively stop, much less reverse it):

• The headlines so far this year have been dominated by the high-profile and incredibly expensive failures of bapineuzumab and solanezumab. However, these two are just the most recent of a long series of failures: a recent industry report tallies 101 investigational drugs that that have failed clinical trials or been suspended in development since 1998, against only 3 successes, an astonishing and painful 34:1 failure rate.


• While we are big fans of the Alzhemier’s Association (just down the street from Placebo HQ here in Chicago) and the Alzheimer’s Foundation of America, it’s important to stress that the single most important contribution that patients and caregivers can make is to get involved in a clinical trial. That same report lists 93 new treatments currently being evaluated.  As of today, the US clinical trials registry lists 124 open trials for AD.  Many of these studies only require a few hundred participants, so each individual decision to enroll is important and immediately visible.


• While all research is important, I want to single out the phenomenal work being done by ADNI, the Alzheimer’s Disease Neuroimaging Initiative. This is a public/private partnership that is
  
  collecting a vast amount of data – blood, cerebrospinal fluid, MRIs, and PET scans – on hundreds of AD patients and matched controls. Best of all, all of the data collected is published in a free, public database hosted by UCLA. Additional funding has recently led to the development of the ADNI-2 study, which will enroll 550 more participants.

Without a doubt, finding and testing effective medications for Alzheimer's Disease is going to take many more years of hard, frustrating work. It will be a path littered with many more failures and therapeutic dead-ends. Today's a good day to stop and recognize that fact, and strengthen our resolve to work together to end this disease.

The Case against Randomized Trials is, Fittingly, Anecdotal

I have a lot of respect for Eric Topol, and am a huge fan of his ongoing work to bring new mobile technology to benefit patients.

The Trial of the Future

However, I am simply baffled by this short video he recently posted on his Medscape blog. In it, he argues against the continued use of randomized controlled trials (RCTs) to provide evidence for or against new drugs.

His argument for this is two anecdotes: one negative, one positive. The negative anecdote is about the recently approved drug for melanoma, Zelboraf:

Well, that's great if one can do [RCTs], but often we're talking about needing thousands, if not tens of thousands, of patients for these types of clinical trials. And things are changing so fast with respect to medicine and, for example, genomically guided interventions that it's going to become increasingly difficult to justify these very large clinical trials. 

For example, there was a drug trial for melanoma and the mutation of BRAF, which is the gene that is found in about 60% of people with malignant melanoma. When that trial was done, there was a placebo control, and there was a big ethical charge asking whether it is justifiable to have a body count. This was a matched drug for the biology underpinning metastatic melanoma, which is essentially a fatal condition within 1 year, and researchers were giving some individuals a placebo.

First and foremost, this is simply factually incorrect on a couple extremely important points.

1. Zelboraf was not approved based on any placebo-controlled trials. The phase 1 and phase 2 trials were both single-arm, open label studies. The only phase 3 trial run before FDA approval used dacarbazine in the comparator arm. In fact, of the 34 trials currently listed for Zelboraf on ClinicalTrials.gov, only one has a placebo control: it’s an adjuvant trial for patients whose melanoma has been completely resected, where no treatment may very well be the best option.
2. The Zelboraf trials are not an example of “needing thousands, if not tens of thousands, of patients” for approval. The phase 3 trial enrolled 675 patients. Even adding the phase 1 and 2 trials doesn’t get us to 1000 patients.

Correcting these details take a lot away from the power of this single drug to be a good example of why we should stop using “the sanctimonious [sic] randomized, placebo-controlled clinical trial”.

The second anecdote is about a novel Alzheimer’s Disease candidate:

A remarkable example of a trial of the future was announced in May. For this trial, the National Institutes of Health is working with [Banner Alzheimer's Institute] in Arizona, the University of Antioquia in Colombia, and Genentech to have a specific mutation studied in a large extended family living in the country of Colombia in South America. There is a family of 8000 individuals who have the so-called Paisa mutation, a presenilin gene mutation, which results in every member of this family developing dementia in their 40s. 

Researchers will be testing a drug that binds amyloid, a monoclonal antibody, in just 300 family members. They're not following these patients out to the point of where they get dementia. Instead, they are using surrogate markers to see whether or not the process of developing Alzheimer's can be blocked using this drug. This is an exciting way in which we can study treatments that can potentially prevent Alzheimer's in a very well-demarcated, very restricted population with a genetic defect, and then branch out to a much broader population of people who are at risk for Alzheimer's. These are the types of trials of the future. 

There are some additional disturbing factual errors here – the extended family numbers about 5,000, not 8,000. And estimates of the prevalence of the mutation within that family appear to vary from about one-third to one-half, so it’s simply wrong to state that “every member of this family” will develop dementia.

However, those errors are relatively minor, and are completely overshadowed by the massive irony that this is a randomized, placebo-controlled trial. Only 100 of the 300 trial participants will receive the active study drug, crenezumab. The other 200 will be on placebo.

And so, the “trial of the future” held up as a way to get us out of using randomized, placebo-controlled trials is actually a randomized, placebo-controlled trial itself. I hope you can understand why I’m completely baffled that Topol thinks this is evidence of anything.

Finally, I have to ask: how is this the trial of the future, anyway? It is a short-term study on a highly-selected patient population with a specific genetic profile, measuring surrogate markers to provide proof of concept for later, larger studies. Is it just me, or does that sound exactly like the early lovastatin trials of the mid-1980’s, which tested cholesterol reduction in a small population of patients with severe heterozygous familial hypercholesterolemia? Back to the Future, indeed.


[Image: time-travelling supercar courtesy of Flickr user JoshBerglund19.]