Question-and-Answer Session
Operator
Thank you. (Operator instructions) We'll take our first question from the site of Brian Abrahams from Oppenheimer & Co. Please go ahead.
Brian Abrahams – Oppenheimer & Co.
Hi guys, thanks for taking my question and congratulations on getting 703 underway. Just a question on the DXA data, I'm wondering what results from the six months DXA scans would one look for such that you would not necessarily need to do long-term bone loss studies? I'm just wondering if there is kind of degrees of variability that are allowable or if there is a certain window around the difference from baseline?
Dr. Chris O'Brien
Right. Thanks, Brian. That's a really important question. Two points, if I may. The most important thing we get out of this 603 study is for the first time we get to link all of these moving pieces. So we have drug exposure, we have estradiol levels, we have n-telopeptide, which is the biomarker for bone resorption and DXA. So with all of those we can have a good understanding of what happens to populations of women with these things, and we can model and argue, we hope, to the FDA, that with the expected range of clinical response at a clinically useful dose that DXA scans are not needed long-term based on the mechanism of action.
To your point of how much change is too much, there is no document from the FDA that says, here is the line in the sand. This is something that always comes down to, after you submit your NDA and label discussions about – is there a black box, is there not? And how – what kind of warnings or restrictions and prescribing information, et cetera? So what we have had is discussions with them to-date about what they would consider clinically meaningful, but they will not commit to here is a specific amount. Now to put that in context, we know that with a drug like leuprolide depot that at six months – after six months of treatment you get anywhere from 5% to 7% bone loss if you don't use add-back, and then even if you stop treatment right then and there, the bone loss continues to mount for months after treatment.
Now, for our program we know that within days of discontinuation of elagolix, estradiol starts to come back up, and we would not anticipate any delayed secroli [ph] from this therapy. So at that point, even if there is a little bone loss, which we don't expect, but even if there were, you wouldn't need a pivotal program that required 6, 12, 24-months of follow-up DXA. So we hope at the time of the end of Phase II meeting we can negotiate our way out of these long-term follow-up studies.
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