Description of Business	9 Months Ended
Sep. 30, 2018
Description of Business
Description of Business	1. Description of Business TESARO, Inc., or the Company or TESARO, was incorporated in Delaware and commenced operations in 2010. Headquartered in Waltham, Massachusetts, TESARO is a commercial-stage biopharmaceutical company devoted to providing transformative therapies to people bravely facing cancer. TESARO’s primary focus is to develop and commercialize treatments for solid tumors using various approaches, including small molecules and immuno-oncology antibodies, as monotherapies and in combinations. The Company has in-licensed and is developing several oncology-related product candidates, and has entered into several research collaborations with third parties for the discovery of new candidates. The Company operates in one segment. The Company is subject to a number of risks, including dependence on key individuals, regulatory and manufacturing risks, the need to develop additional commercially viable products, risks associated with competitors, many of which are larger and better capitalized, risks related to intellectual property, and the need to obtain adequate additional financing to fund the development and potential commercialization of its product candidates and further its in-licensing and acquisition activities. The Company’s product ZEJULA® is approved in both the U.S. and the European Union, or EU, as a maintenance treatment for adults with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in a complete or partial response to platinum-based chemotherapy. In June 2018, the Company entered into an agreement with TerSera Therapeutics LLC, or TerSera, pursuant to which the Company sold to TerSera its rights to VARUBI® (rolapitant) in the United States and Canada, and the transaction closed in July 2018. See Note 13, “VARUBI Transaction”, for additional details. The Company is continuing to market and sell VARUBY in Europe. The Company has incurred significant operating losses since inception and has relied on its ability to fund its operations through private and public equity and debt financings and to a lesser extent through product sales and license and collaboration arrangements. Management expects operating losses and negative operating cash flows to continue for the foreseeable future. As the Company continues to incur losses, the transition to profitability is dependent upon the successful development, approval, and commercialization of its products and product candidates and the achievement of a level of revenues adequate to support its cost structure. The Company believes that its currently available funds, in addition to cash generated from sales of its products, will be sufficient to fund the Company’s operations through at least the next 12 months from the issuance of this Quarterly Report on Form 10-Q. Management’s belief with respect to its ability to fund operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management’s estimates, the Company may need to seek additional funding sooner than expected, or reduce or defer spending on future research and development.

1. Description of Business

TESARO, Inc., or the Company or TESARO, was incorporated in Delaware and commenced operations in 2010. Headquartered in Waltham, Massachusetts, TESARO is a commercial-stage biopharmaceutical company devoted to providing transformative therapies to people bravely facing cancer. TESARO’s primary focus is to develop and commercialize treatments for solid tumors using various approaches, including small molecules and immuno-oncology antibodies, as monotherapies and in combinations. The Company has in-licensed and is developing several oncology-related product candidates, and has entered into several research collaborations with third parties for the discovery of new candidates. The Company operates in one segment. The Company is subject to a number of risks, including dependence on key individuals, regulatory and manufacturing risks, the need to develop additional commercially viable products, risks associated with competitors, many of which are larger and better capitalized, risks related to intellectual property, and the need to obtain adequate additional financing to fund the development and potential commercialization of its product candidates and further its in-licensing and acquisition activities.

The Company’s product ZEJULA® is approved in both the U.S. and the European Union, or EU, as a maintenance treatment for adults with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in a complete or partial response to platinum-based chemotherapy. In June 2018, the Company entered into an agreement with TerSera Therapeutics LLC, or TerSera, pursuant to which the Company sold to TerSera its rights to VARUBI® (rolapitant) in the United States and Canada, and the transaction closed in July 2018. See Note 13, “VARUBI Transaction”, for additional details. The Company is continuing to market and sell VARUBY in Europe.

The Company has incurred significant operating losses since inception and has relied on its ability to fund its operations through private and public equity and debt financings and to a lesser extent through product sales and license and collaboration arrangements. Management expects operating losses and negative operating cash flows to continue for the foreseeable future. As the Company continues to incur losses, the transition to profitability is dependent upon the successful development, approval, and commercialization of its products and product candidates and the achievement of a level of revenues adequate to support its cost structure. The Company believes that its currently available funds, in addition to cash generated from sales of its products, will be sufficient to fund the Company’s operations through at least the next 12 months from the issuance of this Quarterly Report on Form 10-Q. Management’s belief with respect to its ability to fund operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management’s estimates, the Company may need to seek additional funding sooner than expected, or reduce or defer spending on future research and development.