Emil Kakkis
Analyst · Stifel
Thanks, Danielle, and good afternoon, everyone. Thank you for joining us.
First half of 2018 has been a transformational period for us with strong initial launch for both Crysvita and Mepsevii as well as the progress on development front across our programs.
I'll start first with the Crysvita program. We launched in the U.S. in April 27, which means that by June 30, we had only 2 months of commercial activity this quarter. [indiscernible] launch is going very well. At the end of the quarter, we had received approximately 300 completed patient start forms that [indiscernible] unique prescribers across 38 states. This shows broad adoption well above beyond the 10 U.S. [indiscernible] sites.
At this point, the majority [ of ] major metabolic centers have prescribed Crysvita and approximately 2/3 of patients with completed start forms have been naive to treatment with Crysvita. Among the completed start forms, we continue to see a 60-40 split among pediatric [indiscernible] , which indicates substantial interest amongst both adults and children with XLH.
We're also encouraged by the number of patients who have been converted to commercial therapy to date. We continue to work through the reimbursement process for the majority of patients with completed start forms. As anticipated, this takes about 30 to 90 days during this medical exception period with a newly approved therapy.
The payer mix as of the end of the quarter was approximately 70% private plans with the majority of the remaining plans from government payers. We've seen medical policies from a mix of national and regional payers covering about 100 million lives. And the policies have been consistent with the broad Crysvita label for the treatment of XLH in adult and pediatric patients 1 year of age and older. And the policies have not differentiated between children and adults.
In these early days of launch, we're continuing to see new start forms come in and new patients be identified by our Patient Diagnosis Liaison team. This reinforces our belief in our estimate of 3,000 pediatric patients and 9,000 adult patients in the United States. We regularly hear feedback [indiscernible] from XLH patients, and we look forward to the launch progress in the coming quarters.
As our launch continues, we've also succeeded in developing additional clinical data which support Crysvita's superiority to conventional therapy of oral phosphate and active vitamin D. Quarter to date, our pediatric Phase III randomized control study, the first study directly compared to conventional phosphate therapy. In this study, we showed that Crysvita had a rapid and profound effect on the underlying XLH disease with normalization or near-normalization serum phosphorous achieved on average with Crysvita that was not achieved with conventional therapy. The strong improvement in phosphorus levels led to significant improvement in bone disease of patients treated with Crysvita were 39x more likely to achieve substantial healing of rickets compared to patients treated with conventional therapy.
In addition to these new Phase III results, the New England Journal of Medicine recently published the results from the Phase II study of Crysvita in children age 5 to 12, a pivotal study for the pediatric indication.
In summary, the Crysvita launch is off to a strong start, and we also see continued strength in the clinical evidence base of Crysvita's encouraging new data.
Turning to Meps, this launch had been underway for 8 months and is progressing well. We continue to identify new patients with this extremely rare disease [indiscernible] we continue to receive start forms [indiscernible] give us confidence in our estimate of 200 patients worldwide. Following the U.S. approval, we are now refining requests for named patient programs in other countries. We will also be expanding our efforts [indiscernible] into Europe where the CHMP recently adopted a positive pending -- recommending the marketing authorization of Mepsevii under exceptional circumstances. This should be followed by a decision from European Commission in the third quarter of 2018 and reimbursement in Europe happens on a country-by-country basis and can take up to 24 months.
Also product update on UX007 in long-chain fatty acid oxidation defects, or LC-FAOD. For the past few months, we've been working with the FDA to determine the acceptability of an NDA based on data from the Phase II study as well as additional supportive data. In their review, the FDA noted that the effect on reducing hospitalization was substantial and important. However, the question was a result of [indiscernible] in dietary care of the patients during the study due to differences in [indiscernible] levels of UX007 and MCT oil. More specifically, the protocol specified UX007 [indiscernible] 30% is higher than the usual MCT dose that targets 20% but ranged from 0 to 30% in the study subject at baseline.
The change in target UXO subdoses predetermined in the protocol and was based on years of prior academic work and the range of change observed in individuals' MCT doses is very broad and not proportionally [indiscernible] with improvement. After reviewing the [indiscernible] information we provide, the FDA has maintained their concern regarding whether [indiscernible] the UX007 was confounded by diet. We, as well as many investigators and patients, believe the reduction events of this magnitude had to be the UX007 drug at that dose. As a result, we are continuing discussions with FDA. And when these discussion with FDA and further discussions with EMA conclude, we will determine if and what additional study may be needed.
Most importantly, we believe that the submitted data from the Phase II study, the retrospective medical record view, emergency IND cardiomyopathy and [indiscernible] that is showing an effective cardiac function, are together [indiscernible] support early filings. These data aren't [indiscernible] any other rare disease products filed and approved. We're rigorously pursuing a path forward to get this potential therapy to patients as soon as possible, realizing the importance of doing so. We expect to have an update on progress at FDA and EMA in half of 2018. I look [indiscernible] update [indiscernible] .
We also continue to make progress with our gene therapy program. In July, we dosed the first patient in our Phase II DTX401 study, an adeno-associated virus vector-based gene therapy for the treatment of glycogen storage in type Ia or GSDIa. The FDA also granted fast-track designation program to help us still facilitate the development and expedite the review of this therapy for patients with [indiscernible] debilitating disease that can lead to severe hypoglycemic seizures. The first [indiscernible] part of the study will enroll 3 patients, and we expect data the second half of this year.
[ Clinical ] pipeline is also progressing nicely and our plan continues to be generating new IND every March, years from this portfolio.
With that, I'll turn the call over to Shani to provide an overview of our financial results.