products to date. We have incurred significant annual net operating losses in every year since our inception and expect to continue to incur net operating losses for the foreseeable future. Our net operating losses were $38.5 million and $83.0 million for the years ended December 31, 2015 and 2016, respectively. As of June 30, 2017, we had an accumulated deficit of $229.3 million. We expect to continue to incur significant expenses and increasing operating losses for the next several years. Our net losses may fluctuate significantly from quarter to quarter and year to year. We anticipate that our expenses will increase significantly if and as we continue to develop and conduct clinical trials with respect to AVXS-101; develop our planned new programs for Rett syndrome and ALS; maintain, expand and protect our intellectual property portfolio; establish a commercial infrastructure to support the manufacture, marketing and sale of AVXS-101 if it receives regulatory approval; and hire additional personnel, such as clinical, regulatory, manufacturing, quality control and scientific personnel.
To date, we have entered into three license agreements relating to the development of AVXS-101.
Nationwide Children’s Hospital
In October 2013, we entered into an exclusive, worldwide license agreement with Nationwide Children’s Hospital, or NCH, under certain patent applications, and a non-exclusive license under certain technical information, for the use of its scAAV9 technology for the treatment of SMA, of all types, or the NCH SMA License. In January 2016, we amended and restated the NCH SMA License in its entirety. Under the NCH SMA License, we initially issued NCH and The Ohio State University, or OSU, 331,053 shares of common stock. Until May 2015, when we had reached a market capitalization of $100.0 million, we were obligated to issue additional shares to NCH and OSU from time to time to maintain a 3% ownership of the company on a fully-diluted basis. We issued an aggregate of 124,990 additional shares of common stock between October 2013 and May 2015 pursuant to these anti-dilution obligations. With certain exceptions, we are required to make up to $0.1 million in development milestone based payments to NCH. In addition, we are responsible for all clinical trial costs that are not covered by grants or certain other sources.
Following the first commercial sale of a NCH SMA licensed product we must begin paying NCH an aggregate low-single digit royalty on net sales of any products covered by the NCH SMA License, subject to reduction in specified circumstances and annual minimum royalties that increase over time. In addition, we must pay NCH a portion of sublicensing revenue received from our sublicense of the licensed technology at percentages between low-double digits and low-teens.
On November 6, 2015, the FDA approved our sponsorship of the IND and the transfer of the associated regulatory filing from NCH.
ReGenX Biosciences, LLC
In March 2014, we entered into an exclusive license agreement with ReGenX Biosciences, LLC, or ReGenX Biosciences, predecessor to REGENX, under certain patent rights owned by the Trustees of the University of Pennsylvania and licensed to ReGenX Biosciences, for the development and commercialization of products to treat spinal muscular atrophy by in vivo gene therapy using AAV9, or the ReGenX SMA License. Under the ReGenX SMA License, we paid ReGenX Biosciences an initial licensing fee of $2.0 million. We are also required to pay ReGenX Biosciences: annual maintenance fees, up to $12.25 million in milestone fees for all products covered by the ReGenX SMA License, or ReGenX SMA licensed products; mid-single to low-double digit royalty percentages on net sales of ReGenX SMA licensed products, subject to reduction in specified circumstances; and lower mid-double digit percentages of any sublicense fees we receive from sublicensees for the licensed patent rights. As of June 30, 2017, we have paid $2.4 million under the ReGenX SMA License, which includes $0.3 million in aggregate milestone payments.