Christiana Stamoulis
Executive Vice President and Chief Financial Officer at Incyte
Thank you, Steven, and good morning, everyone. Our fourth quarter results reflect continued strong revenue growth, with total product revenues of $764 million, representing an increase of 18% over the fourth quarter of 2021. Total product revenues are comprised of $647 million for Jakafi, $55 million for other hematology/oncology products and $61 million for Opzelura.
Net product revenue growth was primarily driven by increases in Jakafi and Opzelura net revenues. Other hematology/oncology revenues, which include revenues from parsaclisib, Pemazyre and Minjuvi were impacted by unfavorable changes in FX rates.
On a constant currency basis, other hematology/oncology net product revenues grew by 23% over the prior year period. Total royalty revenues for the quarter were $132 million and are comprised of royalties from Novartis of $91 million for Jakavi and $4 million for Tabrecta and royalties from Lilly of $36 million for Olumiant. Jakavi and Olumiant royalties for the quarter were negatively impacted by FX headwinds, while Olumiant royalties were also impacted by a decrease in net product sales of Olumiant for use as a treatment for COVID-19.
Excluding the impact of COVID-19 related sales and currency fluctuation, Olumiant royalties increased 23% compared to the prior year period. For the full year 2022, total net product revenues were $2.7 billion and total revenues were $3.4 billion, representing 18% and 14% year-over-year increase respectively.
Moving to Slide 25. Opzelura net product revenues for the quarter were $61 million, driven by robust demand and broadening payer access. As payers continue to add Opzelura to formularies and the share of covered claims increased, we continue to see improvement in the gross to net discount rate. The gross to net discount rate decreased from an average of 71% in the third quarter of 2022 to an average of 57% in the fourth quarter of this year and we exited 2022 at a gross to net discount rate of 50%.
While we will continue to work on reducing patient copay and in turn improving gross to net, an average gross to net of 50% is a good working assumption for 2023 with a gross net discount in the first quarter of the year expected to be higher than subsequent quarters as plants reset patient deductibles at the beginning of the year.
I would also like to take the opportunity to update you on the Opzelura prescriptions data provided by IQVIA. As you see on Slide 26, in Q4, we saw the gap between the actual number of total prescriptions and the number of prescriptions reported by IQVIA narrowing. While the IQVIA data continues to overstate demand, this overstatement has been reduced to a level of 5% to 10%, which is within expectations for a newly-launched product. In addition, it is important to note that IQVIA data reflects total demand, which includes both paid prescriptions and free drug. Going forward, free drug is expected to represent around 20% of total demand. When looking at IQVIA data, one would need to adjust for this overstatement, as well as for free drug in order to get a better sense of paid demand.
Moving on to Slide 27 and our operating expenses on a GAAP basis. Ongoing R&D expenses were $431 million for the fourth quarter and $1.5 billion for the full year 2022. Total R&D expenses, which include the upfront consideration of $70 million for our acquisition of Villaris were $501 million for the fourth quarter.
For the full year 2022, total R&D expenses, which in addition to the Villaris upfront payment also include $56 million in other milestone payments, were $1.6 billion, representing a 9% year-over-year increase. The increase was primarily due to the progression of our pipeline and was partially offset by lower upfront and milestone expenses in 2022.
Total SG&A expenses were $273 million for the fourth quarter and $1 billion for the full year 2022. The year-over-year increase was driven by investments related to the new dermatology commercial organization in the U.S. and the related activities to support the launch of Opzelura in atopic dermatitis and vitiligo.
Moving on to 2023. I will now discuss the key components of our guidance on a GAAP basis. For Jakafi, we expect net product revenues to be in the range of $2.53 billion to $2.63 billion, which at the midpoint represents an increase of approximately $170 million over 2022, driven by continued growth across all indications. We expect our gross to net adjustments for 2023 to be approximately 23%, reflecting expected continued growth in 340B volumes. As a reminder, the gross to net adjustment in the first quarter of the year is always higher relative to other quarter and previous quarter and subsequent quarters due to our share of the donut hole for Medicare participation.
For other hematology oncology products, which include Pemazyre in the U.S., EU and Japan and Iclusig and Minjuvi in Europe, we are expecting total net product revenues to be in the range of $215 million to $225 million.
Turning to operating expenses on a GAAP basis, we expect COGS in a range of 7% to 8% of net product revenues, which is in line with 2022. R&D expenses are expected to be in the range of $1.61 billion to $1.65 billion, representing 3% year-over-year growth at the midpoint. SG&A expenses are expected to be in the range of $1.05 billion to $1.15 billion, primarily reflecting continued investment in Opzelura and the full year impact of the investment in the vitiligo indication.
Operator, that concludes our prepared remarks. Please give your instructions and open the call for Q&A.