Jay,
I have many urgent matters to deal with on a daily basis, so I must prioritize. Addressing situations that require immediate attention will always take precedence over questions that have no urgency. I hope you do realize that my efforts are volunteer and that I give an inordinate amount of time to thals. I have no appreciation for impatience. Excuse me if my time has been spent on helping people with urgent issues that should have been addressed by their own doctors long ago. I really will put the mother of a 36 year old woman whose life is not worth living above random questions that have absolutely no urgency. In addition to my public work here, I run three Facebook thal groups and am constantly inundated with emails and personal messages. It becomes quite frustrating when adults show a lack of patience. And I say all this while suffering for over two weeks from the flu, yet I have missed no work and have attended to some very urgent cases, in spite of feeling terrible.
To answer the questions, they are doing DNA testing of patients. This is seen in each patient being labeled HbE beta thal +, beta zero zero, beta + zero, etc. They can only know this through testing. The reason for doing this is to show that it works on all patients, regardless of the severity of their thalassemia. The original condition has no relevance in terms of the cure, though. Good beta globin genes are inserted into the body and what is already there has no relevance beyond its initial ability to produce hemoglobin, which in the end will be part of the whole. What trials will show is what has to be done in terms of preparation in terms of chemotherapy, and how dosing has to be adjusted for individual cases. The original genotype has no effect on this process. Unlike with BMT, you are not changing the patients genetically. It is simply insertion of working genes. Their function substitutes for what is already in the body and does not work properly. The old genes are still there and 'working" but a newly introduced beta globin gene will do the work. You can almost look at it as a recipe that needs something. Ah, salt! It's incomplete until salt is added and the blood making ability of thals is incomplete until you add the salt of a working gene and now the recipe works.