[5][6] In December 2001, a doctor named Hans Klingemann filed a patent application for a new method of treating cancer using natural killer cells.

[4][10] This is in contrast to the Federal Circuit, which as an appellate court can only consider evidence that was in the record reviewed by the Board of Patent Appeals.

Prior to discovery, USPTO filed a motion for summary judgment (essentially arguing that the court had enough agreed-upon facts on the record to rule on the case immediately without conducting further proceedings).

The District Court granted USPTO's motion for summary judgment, ruling in favor of the agency, that NantKwest's patent claims were invalid due to obviousness.

[11] Following the Federal Circuit's affirmation, USPTO then filed a motion for reimbursement in District Court of "the expenses of the proceedings", as permitted by section 145 of the Patent Act.

[12] The USPTO's position was that the language of section 145, which stated that the applicant had to pay "All the expenses of the proceedings", entitled it to collect attorneys' fees.

[13] Applying a precedent the United States Court of Appeals for the Fourth Circuit, the panel ruled that "expenses of the proceeding" include a pro rata share of the salaries of USPTO employees who worked on the case.

In her dissent, Judge Stoll argued that section 145 lacked the specificity needed to indicate that Congress had the intent to depart from the American Rule and allow for attorney fees to be awarded.

Writing for a unanimous court, Justice Sonia Sotomayor's opinion stated that the reference in section 145 to "expenses" did not include USPTO's in-house attorney fees.