TESARO Describes Initial Phase 1 Clinical Data for TSR-011 Presented at the European Cancer Congress 2013

• TSR-011 Identified as a Potent Dual Inhibitor of ALK and TRK Kinases
• Preliminary Clinical Activity Demonstrated in Patients with Several Tumors, Including ALK-Positive NSCLC Patients Previously Treated with Crizotinib
• Phase 2 Dose Selection and Cohort Expansion Into Patients With ALK-Positive or TRK-Mutated Tumors Anticipated to Occur by Year End
  

AMSTERDAM, Netherlands, Sept. 29, 2013 (GLOBE NEWSWIRE) -- TESARO, Inc. TSRO, an oncology-focused biopharmaceutical company, presented initial data from a Phase 1 trial of TSR-011 today at the European Cancer Congress in Amsterdam. TSR-011 is a potent inhibitor of both anaplastic lymphoma kinase (ALK) and tropomyosin-related kinases (TRK). Preliminary clinical activity has been observed in this study in one papillary thyroid carcinoma patient and one pancreatic cancer patient without ALK expression, and in three patients with ALK-positive non-small cell lung cancer (NCSLC) who progressed following prior treatment with crizotinib.

Of the three ALK-positive NSCLC patients who progressed on prior crizotinib treatment, one achieved a RECIST partial response after four weeks of treatment with TSR-011; one, with disease not evaluable by RECIST criteria, achieved an investigator-assessed partial response; and one has stable disease. Each of these three patients remains on study today. In addition, one patient with papillary thyroid carcinoma and one patient with pancreatic cancer each have long term stable disease following several cycles of TSR-011 treatment. Preliminary results after eight weeks of treatment with TSR-011 demonstrated disease control (partial responses plus stable disease) in 11 of 17 (65%) evaluable patients treated with TSR-011.

"We are very pleased with the emerging profile of TSR-011, including the adverse event profile and early demonstration of clinical activity," said Dr. Mary Lynne Hedley, President of TESARO. "We remain on track to move into Phase 2a by the end of this year, which will allow us to further evaluate the benefit/risk profile of TSR-011 in patients with cancers that are ALK-positive or have TRK rearrangements."

Pharmacokinetic data demonstrated rapid absorption, predictable, dose proportional plasma concentrations following oral administration and an elimination half-life of 12 to 24 hours. TSR-011 was well tolerated at therapeutic dose levels, and no drug related Grade 4 or Grade 5 adverse events have been observed to date. The most frequently occurring dose limiting toxicities included ECG changes and dysaethesia, both of which were reversible.

Phase 1/2a Trial Design

The ongoing Phase 1/2a trial is a sequential, open-label, two part study with dose escalation in Phase 1 followed by expansion into selected cohorts in Phase 2a. Following identification of a recommended Phase 2 dose and schedule, Phase 2a will be initiated to evaluate the safety and efficacy of TSR-011 in a variety of tumor settings that express ALK or TRK. The three expansion cohorts will include: (1) patients who have ALK-positive, ALK inhibitor naive non-small cell lung cancer (NSCLC); (2) ALK-positive NSCLC patients who have progressed following prior treatment with another ALK inhibitor; and (3) patients with other solid tumors or lymphomas that are either ALK-positive or have mutations of TRK genes.

About TSR-011

TSR-011 is an investigational, potent, small molecule inhibitor of ALK and TRK-A, -B and -C that is currently being evaluated in a Phase 1/2a study. TSR-011 has demonstrated potent inhibition of tumor growth in ALK-positive xenograft models and caused regression in ALK-positive NSCLC tumor graft derived from a patient who progressed on crizotinib. TSR-011 has also demonstrated potent growth inhibition of the TRKA-rearranged colorectal cancer cell line KM12.

About TESARO

TESARO is an oncology-focused biopharmaceutical company dedicated to improving the lives of cancer patients by acquiring, developing and commercializing safer and more effective therapeutics. For more information, visit www.tesarobio.com.

To the extent that statements contained in this press release are not descriptions of historical facts regarding TESARO, they are forward-looking statements reflecting the current beliefs and expectations of management made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Words such as "may," "will," "expect," "anticipate," "estimate," "intend," and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. Forward-looking statements involve substantial risks and uncertainties that could cause our clinical development programs, future results, performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the uncertainties inherent in the initiation of future clinical trials, availability of data from ongoing clinical trials, expectations for regulatory approvals, and other matters that could affect the availability or commercial potential of our drug candidates. TSR-011 is an investigational agent and, as such, has not been approved by any regulatory agencies. TESARO undertakes no obligation to update or revise any forward-looking statements. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to the business of the Company in general, see TESARO's Form 10-K for the year ended December 31, 2012.