What response letter are you referring to? Here is imtesty's transcript on that topic. I don't see any reference to a letter.

"Now let’s discuss our breakthrough therapy designation and our exciting new relationship with the FDA. The breakthrough therapy designation was awarded to Resverlogix in February of this year, only four months ago. It is considered the highest endorsement that you can get from the FDA short of actual drug approval. As of last year, only 130 drugs had ever been given this designation. The FDA website states that, (I’ll quote), “A breakthrough therapy designation is for a drug that treats a serious or life-threatening condition, and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement on a clinically significant endpoint or endpoints over available therapies.” So a breakthrough therapy designation conveys all of the fast-track program’s features and more intensive FDA guidance in development. The program also involves an efficient drug development program and an organizational commitment involving senior managers from the FDA, eligibility enrolling reviews and priority reviews. On June 2, we had the first of these priority review meetings. It went exceptionally well. We are following up on this meeting’s advancements and recommendations as we speak, and upon written confirmation from the FDA, we will gladly inform the market and our ongoing potential pharma co-development partners of the content of the full plans of our BETonMACE2 registration trial."

Koo