A secret sale of a device may start the clock running for when patents must be filed. On January 22, 2019, in Helsinn Healthcare v. Teva Pharma USA, the Supreme Court ruled that a commercial sale -- even where the buyer is obligated to keep the invention confidential -- may place the invention “on sale” and thus invalidate a later filed patent for the invention. Subject to other requirements under the law, a patent applicant is entitled to a patent for an invention, unless the claimed invention was patented, described in a printed publication or in public use, on sale or otherwise available to the public before the filing date of the patent application. In Helsinn, patents directed to treatments for chemotherapy side effects were rendered invalid, because the patent holder had entered into confidential marketing and sales arrangements two years before filing its patent applications. Companies beginning to commercialize their inventions should be wary that early stage marketing and sales relationships can harm the patentability of their products, even when conducted under nondisclosure agreements.