bluebird bio Inc (NASDAQ:BLUE) is up sharply pre market on Thursday, as the company put out fresh interim data from a phase I study of its multiple myeloma (MM) asset, bb2121. The drug is being developed in partnership with biotech giant Celgene Corporation (NASDAQ:CELG), and is essentially a last-ditch option for patients in this indication who have run out off potential treatments. While the data is demonstrated efficacy across the sample population, the safety and tolerability side of the treatment was very much under scrutiny (and still is) based on some pretty severe responses seen in trials investigating drugs that are not bluebird’s, but that rely on a similar mechanism of action – namely, CAR T. One of the primary drivers behind the pre-market gains is the difference seen between these latter mentioned CAR T alternatives, and bluebird’s bb2121. We will get to that in a little more detail shortly, but first, let’s look at the drug in question and the efficacy results as they stand.
As mentioned, the drug is called bb2121, and it targets a protein called BCMA. We don’t need to go into too much detail on the mechanism of action here, as we have discussed CAR T on a number of occasions in the past, but for those not familiar with this type of treatment, it essentially harnesses the immune system to attack cancer cells selectively. Specifically, the drugs in question train T cells to recognize cancer cells by – in turn – training them to recognize a protein that is only expressed by the cancer cells in question. In this instance, that protein is BCMA, and cancerous blood plasma cells (like those associated with MM) express the protein in abundance, while healthy plasma cells do not.
The data is interim, and as such, is representative of quite a small patient population, but from an efficacy perspective, we couldn’t really have asked for any more. There were nine evaluable patients (of a total 11 that had been enrolled up to the data cut off point of November 18), with three receiving a low dose, three receiving a medium dose, and three receiving a high dose. In the low-dose patients, one experienced a 50% reduction in signs of MM, which in itself is a decent return rate on treatment (bear in mind that these patients have received up to six previous lines of therapy to which they have not responded).
However, it was the medium and high dose patients that really stood out in this report.
All six (three medium, three high) showed a minimum 50% reduction in cancer visibility, with two demonstrating a minimum residual disease (MRD) level of zero. Minimum residual disease is basically a way of saying “can we detect cancer here, and if so, what is the minimum level at which it is detectable?”
Ergo sum, an MRD level of zero means the cancer was undetectable.
These sorts of results just don’t happen in MM late stage, so it looks as though bluebird and Celgene could be onto a winner with bb2121. As mentioned earlier, however, there’s another interesting element study, and that is the tolerability outcome. This type of treatment (CAR T) has been linked to some pretty severe side effects, with the most concerning being what’s called cytokine release syndrome (CRS). CRS can be severe enough in certain patients (especially those such as late stage MM patients) to pretty much negate the benefits of CAR T treatment altogether. That was one of the two companies’ primary concerns with this trial. However, as illustrated by this interim data, there were no CRS incidents across any of the doses. For us, that is almost as important as the efficacy readout.
Now, it is important to remember that these are very early data, and the population is small. However, the trial aims to enroll up to 50 patients, and we should see topline sometime late 2018, or early 2019. Estimated study completion date is December 2018. If the results across the 50 patient sample mirror those seen in this nine patient subsample, expect big things from the bluebird asset.
On the news, bluebird is sitting at its highest market cap in almost twelve months, while Celgene is up a couple of percentage points pre market.
