Question-and-Answer Session
Operator
(Operator Instructions). It looks like first we'll go to the side of Thomas Wei from Piper Jaffray. Please go ahead.
Thomas Wei - Piper Jaffray
Thanks very much. I had a couple of questions on the 603 study for elagolix. In listening to your commentary, it sounds like we should be careful about some of the comparisons that might be drawn between the elagolix arms and the Depo-Provera arm.
Can you just help us understand a little bit better when we see the data how we should interpret that and to what degree we should be drawing bone mineral density comparisons and also efficacy comparisons?
Chris O'Brien
Thanks, Tom. I said its cycle questions, because Depo-Provera although it has a black box in large part due to bone loss. The bone loss that occurs with Depo-Provera is something that is typically associated with longer duration treatment at a year, or year and a half.
At six months, the amount of bone loss is relatively small. Now of course Lupron at six months, the amount of bone loss is substantial, and that reflects the fact that the mechanism for bone loss with these drugs are different, so Lupron as you know causes post-menopausal levels of estradiol and that appears to be the mechanism for bone loss.
Elagolix is designed to give a partial reduction in estradiol, and by kind of hitting that therapeutic window, avoid estradiol levels that would be associated with bone loss. DMPA is not a drug that is designed to suppress estradiol. So its mechanism for bone loss is more likely reflects the facts that this synthetic progesterone acts in some measure as a cortical steroid (inaudible) is associated with that kind of bone-thinning effect, if you will.
So if you go to the literature and you look at Depo-Provera bone loss data at six months, it's not very big. It's in the kind of the 2% range although the variability is quite broad. The pivotal trial with Depo-Provera for endometriosis showed a range from an 18% bone loss to a 10% bone mineral density gain.
So, it's a broad range reflecting a lot of variability among women. But overall, at six months the bone loss was only in that kind of the 2% range. It's only when you get out to 9 months and 12 months then it really starts to build. So, we didn't choose DMPA as an active competitor to show superiority here, we chose it as a positive control to detect subtle changes, to make sure that we were comfortable in our position with elagolix.
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