Chimerix’ drug brincidofovir should be viewed with skepticism


Chimerix [$CMRX] is testing the drug brincidofovir on patients who have received allogenic hemopoeitic cell transplants (HCT). In English, “allogenic hemopoeitic cell transplants” means “bone marrow cell transplants from another person.” Specifically, CMRX is testing their drug on HCT patients who have adenovirus infections.

The adenovirus is the virus that causes the common cold, but in patients with HCT, the adenovirus can be incredibly deadly. Patients who have received cell transplants are almost invariably on drugs to suppress their immune system so that their bodies accept the transplant. What’s worse, just like there’s no treatment for the common cold, there’s no real treatment for adenovirus infections, especially for patients with HCT. Chimerix is hoping to change that with their new drug.

The Problems

With all that in mind, brincidofovir seems to be a promising drug candidate — at least on the surface. I have a lot of issues with the research they’ve done so far. For me, the quality of the research tends to be the number one determining factor when investing in a biotech. It’s more than just a data thing, it’s an integrity thing.

With that said, here are the issues I have with CMRX:

The current trial of brincidofovir doesn’t have any sort of placebo control, and I haven’t found a good explanation why that might be. Previous trials were controlled, and for what’s ostensibly a Phase 3 trial I don’t see what the rationale for not controlling the data could be.

Second, the researchers compared the survival rates from their trials to historical survival rates for HCT patients with adenovirus infections and found no difference. CMRX mentioned that they think this is because they deliberately tested high-risk patients. This might be true, but it’s impossible to tell. Along the same lines, in the Phase 2 study (which was placebo-controlled) there was no difference in the primary endpoints between patients treated with placebo and patients treated with brincidofovir.

These adenovirus trials are not the first time brincidofovir has been tested. The last set of trials were on a different virus in the same clinical population. As you can probably guess, those trials were unsuccessful.  In addition, in some of the previous research I looked through, I saw methods that I really didn’t like. Chimerix did some things that I would generally consider “sketchy:”

If patients discontinued the study drug to start treatment for CMV infection or for other reasons, but the plasma CMV DNA level was 200 copies per milliliter or less and CMV disease was not confirmed, treatment with CMX001 was considered to be successful.

-Phase 2 Trial of brincidofovir

To provide some context, brincidofovir was supposed to prevent patients from getting a disease called CMV. What the researchers are saying here is that if people dropped out of the study to treat CMV, they were counted as “success” cases. In a lot of CMRX’s trials so far, we’ve seen what looks like a really potent effect on keeping virus counts down — but the patients are dying anyway. After seeing this kind of crap, I was a lot less surprised.

The Good

Chimerix has plenty of cash on hand – at the current burn rate, they can go about 3 more years before they run into trouble. That should be enough to either get them to success or conclusively determine that brincidofovir is not a viable drug.

As I mentioned above, CMRX’s drug seems to be doing something. The difference in virus counts for patients treated with brincidofovir is indisputable. The issue, of course, is that CMRX has yet to keep people from dying.


Chimerix plans to release the full set of data from the adenovirus trial in the first half of this year. After the data dump, I think it’s very possible that the drug will continue on to a comparative trial. Not because the results are that promising, but rather because the need for a safe treatment is so dire. And to be frank, I think CMRX is a bit desperate.

This is one of the cases where I would love to be wrong, because the adenovirus is killing a huge number of HCT patients. I would love it if brincidofovir ended up becoming a miracle drug — but I can’t in good conscience recommend investing in it.

Prediction: Phase 3 Failure

There are just too many issues with the data for me to feel good about Brincidofovir or Chimerix. I do not recommend investing. 

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