Question-and-Answer Session
Operator
(Operator Instructions). Your first question is from Michael Yee.
Michael Yee - RBC Capital Markets
Hi. Great. Quick questions for you guys. Congratulations on accomplishment so far. And thinking about the GERD study coming up at the end of the year, maybe Ron, can you talk a little bit about handicapping that study? I mean, you have to Phase 2a that was positive, just very significant on both the regulatory endpoint, and then that's the same endpoint in here you're using here. Can you talk about any of the changes in the trial or how you're thinking about this study?
Ron Barrett
Sure. I just want to make a clear that that study that we did previously was a study with a single dose where we measure objectively reflux events. We also monitored heartburn in that study and did see effects on both. But that was a single dose study and the study that we have ongoing is with much larger patient population, a 159 patients in total in this study. And also is administering the drug for four weeks.
With regard to handicapping general -- I don't get into that aspect of it. But I will talk about the results from the previous study that lead us to believe that the chances are good that we'll have a successful study. The first is that during the single dose study that we did with 986 in GERD patients, we actually monitor pharmacokinetic in that study and we have the blood levels that were associated with the efficacy in that study.
And then, we also have Phase I data with this formulation that we're using in the current study, which allowed us to know what the exposures would be at various doses and also know whether those exposures would be well tolerated.
So the doses that we've chosen for this Phase 2 GERD study, that's ongoing, are doses that produce exposures, that were effective in the single dose study, and also doses that were well-tolerated in the healthy subject study. So we look forward to getting those results by the end of the year.
Michael Yee - RBC Capital Markets
Okay. Great. Thanks.
Ron Barrett
You're welcome.
Operator
Your next question is from Rachel Mcminn with Cowen and Company.
Rachel Mcminn - Cowen and Company
Yeah. Thanks very much. A couple of questions. Just a quick on the migraine comment from GSKs. What really drove the change there, was there some specific commentary from FDA or was there revisiting from GSK internally?
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