Thread by @Biotech2k1

@HassanAesthetic Profile for $GRPH

1/ This company uses CRISPR CAS9 in a whole new approach. They use a CAS9 enzyme along with the guide RNA to find the right place in the Genome and do a Double Stranded Break (DSB).

2/ Then they use a second AAV6 vector to deliver a template strand of DNA that the cell can use for Homology Directed Repair (HDR). I looked at this approach, and I see so many things that could go wrong.

3/ The first thing that jumped out at me was the really low sub 50% efficiency of insertions. This is related to the repair system. I am betting that most of these DSB's get repaired by Non Homologous End Joining (NHEJ) with not insertion being made.

4/ Just because you send in a template with a separate vector does not mean its getting used. Now you have the same CAS9 worries of off targeting of the guides, mutations of the DSB, and now you add in the extra risk of low efficiency of using 2 vectors and low efficiency.

5/ The template strand for the fix of the DNA using HDR uses homology arms to match about 40 bases on either side of the gene of insertion.

6/ My issue is the low efficiency make me think the insertion is not happening in all cells as the template strand doesn't get to that cell or its just not used.

7/ Their lead drug is for SCD. Yet another SCD program. Based on the level of efficiency they are getting, I don't think they will work in SCD. To block sickling, you need to have at least 60% of the Red Blood Cell expressing good Hemoglobin.

8/ With only 45% to 50% efficiency, they should not reach that level to stock the sickling. I am not sure if I should even value this program that I think will most certainly fail. They are a long way from showing any data either.

9/ The rest of their pipeline is very rare diseases like X linked SCIDs and Glaucher disease. When I look at his science and the indications. I just have to think its better to wait and see the data. It surely doesn't look as good as the SLEEK from $EDIT.