Sofear,
I think that bluebird bio's final goal is the cure patients and the achieve the highest hemoglobin levels possible and the best quality of life possible. I believe their goal is to achieve hemoglobin levels near normal if possible.
From my understanding, both of the beta zero thalassemia patients had achieved hemoglobin levels of 9.6 at very early stages of their treatment. The Pakistani patient did not achieve engraftment until 29 days - so from the time of engraftment this level is very good. Perhaps with more experience and further tweaking it may be possible to achieve even better results.
For a beta zero patient - having no ability to produce adult hemoglobin at all - the only way to find out what the hemoglobin was before treatment would be to stop transfusing them - my son at the age of 3 months had a hemoglobin of 4.4 - had he not been tranfused he would have fallen even lower. To allow someone to dip that low would be unethical and dangerous. Personally, I think that for patients who have no ability to produce hemoglobin at all - being able to achieve a hemoglobin level of 9.6 is success. I would be very happy if my son would be able to maintain hemoglobin close to 1.0 on his own. Of course I would be even happier if his hemoglobin were 14.0 but I think this treatment has come as closer to a cure with little to no complications than any other procedure.
I think that eliminating the need for constant fluctuating hemoglobin levels, transfusions, iron overload and chelation - in itself will greatly improve the lives of thals. I am a thal minor and my hemoglobin at times is near 1.0 but I don't transfuse and my body has adapted to this level quite well.
Transplants have great chances of graft failure, rejection, gvhd and death. I think that this procedure offers nearly all of the benefits of a successful transplant, without the risks.
The patient that achieved a hemoglobin level of 8.6 had beta E thalassemia. Let us see what the results are when bluebird reveals their findings on June 13th in Europe and answers questions on June 15th.
I am sure that this procedure will continue to evolve and become better and better - but we have a cure. I hope the success continues and that it is available for everyone soon. It is so great to see that the process has been fast tracked.