I'm keeping my expectations low for this upcoming readout which I expect to come closer to the end of March. No reason to rush it unless the data are just completely unexpected and way better than anticipated. On one hand it will be the first readout from a PII trial which is exciting and a step in the right direction but on the other hand it's interim data from the active group and as we all know the best data so far has come in the adjuvant setting.
The active group is a lot harder to treat as evidenced by the PI data. In 8 patients (technically 6 but 2 were dosed twice) there was only 1 complete response and 1 partial response. All of these patients failed multiple lines of therapy. I believe the lowest number of prior therapies failed was 4. These particular patients are clearly running out of options. The CR is obviously positive but this is such a small data set that it is hard to use it as an effective measure of how the PII is going to go. That being said I personally believe that if the PII results can match the PI results we should be ok.
I've touched on this in the past but will just recap a little since the data readout is closer now. This therapy needs to be compared to Donor Lymphocyte Infusions (DLIs). DLIs are given after relapse post stem cell transplant. So the same space Marker is running this PII trial in. They are typically only used for patients who are in very good shape, all else considered, but are very toxic and very expensive. The ORR for DLIs is anywhere between 5%-10%. The main issue with a DLI is Graft vs Host Disease (GvHD) where the donor cells attack the recipient’s healthy cells. The incidence of GvHD in these patients ranges from 40%-60% with 20%-35% being grade 3 or 4.
Even if MultiTAA can just match the response rates of DLIs, ~10% on the high end, it should be approvable based on the extremely favorable safety profile. Not only would it then be a better option for those that would be eligible for a DLI it should also be an option for those that would not have been eligible for a DLI.
The PI CR rate was ~12%. Again, this was based of of 8 patients so we can't really assume those results will carry forward into the PII. However, if they do we would expect to see at least 5 CRs out of the total 40 patients. The upcoming readout will be on 20 patients so it would be nice to see 2 or 3 CRs but I will hold judgement for the full data readout which could come in the middle of the year. I would guess beginning of Q3.
One last note. They are continuing to make manufacturing improvements. They cut the manufacturing time down 50% over the original BCM process and are working towards reducing it another 50% for a total of 75% reduction in manufacturing time. Along with the other improvements they made we should hopefully see improved results in the PII. They are also looking into developing an off the shelf therapy which could be a big step forward if they can manage it. I don't expect it to come soon but it's something to keep an eye out for.
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