investments, including expenses associated with clinical studies, regulatory activities, inventory and supplies for iDose and future iStent product candidates.
The above increase in R&D expenses for the six months ended June 30, 2021 primarily consisted of increased spending in earlier stage technology and related quality assurance activities, partially offset by reduced spending related to our above mentioned clinical studies as those studies reached full enrollment.
In-process Research and Development
IPR&D expenses for the six months ended June 30, 2021 were $5.0 million related to the amendment of our exclusive licensing agreement with Intratus, Inc. There were no IPR&D expenses for the three months ended June 30, 2020.
Non-Operating Expense, Net
We had non-operating expense, net of $7.4 million and $2.0 million for the six months ended June 30, 2021 and June 30, 2020, respectively. The increase in non-operating expense, net primarily relates to interest expense recognized related to the Convertible Notes and recognition of unrealized foreign currency losses due to higher intercompany loan balances denominated in, and impacted by, changes in foreign currency exchange rates.
Income Tax Provision
Our effective tax rate for the six months ended June 30, 2021 was (1.45)%. For the six months ended June 30, 2021 and June 30, 2020, we recorded a provision/(benefit) for income taxes of $0.5 million and ($7.8) million, respectively, which were primarily comprised of state and foreign income taxes for the first and second quarter of 2021, and U.S. federal, state and foreign income taxes for the first and second quarter of 2020, offset by a benefit related to the carryback of federal NOLs under the CARES Act.
Liquidity and Capital Resources
For the six months ended June 30, 2021, we incurred a net loss of $34.0 million and generated cash from operations of $11.6 million. As of June 30, 2021, we had an accumulated deficit of approximately $349.6 million. We have made and expect to continue to make significant investments in our global sales force, marketing programs, research and development activities, clinical studies and general and administrative infrastructure. FDA-approved IDE and IND studies and new product development programs in our industry are expensive. We also expect to incur additional construction costs related to our new facility in Aliso Viejo, California.
Our Convertible Notes may be converted at the option of the holders at the times and under the circumstances and at the conversion rate described in Note 9, Convertible Senior Notes. As of June 30, 2021, one of the conditions allowing holders of the Convertible Notes to convert had been met, as our trading price remained above 130% of the conversion price for at least 20 trading days during the 30 consecutive trading-day period ending on, and including, June 30, 2021. Consequently, holders of the Convertible Notes have the right to convert their Convertible Notes during the calendar quarter beginning July 1, 2021. Upon conversion, we will pay or deliver, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, in the manner and subject to the terms and conditions provided in the Indenture. Our current intent is to settle the principal amount of the Convertible Notes in cash upon conversion, with any remaining conversion value being delivered in shares of our common stock. Given satisfaction of the aforementioned condition, the Convertible Notes are classified within current liabilities on the condensed consolidated balance sheets.
We plan to fund our operations, capital funding and other liquidity needs using existing cash and investments and, to the extent available, cash generated from commercial operations. Our existing cash and investments include the remaining net proceeds from the Convertible Notes issued in June 2020 (after payment for the related capped call transactions), which we are using for working capital and general corporate purposes. Although we have been profitable for certain periods in our operating history, there can be no assurance that we will be profitable or generate cash from operations. We may seek to obtain additional financing in the future through other debt or equity financings. There can be no assurance that we will be able to obtain additional financing on terms acceptable to us, or at all. We believe that our available cash, cash equivalents, investment balances and interest we earn on these balances and any cash generated from commercial operations will be sufficient to fund our operations and satisfy our liquidity requirements for at least