Seagen Announces FDA Accelerated Approval of TUKYSA®

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Seagen Announces FDA Accelerated Approval of TUKYSA® (tucatinib) in Combination with Trastuzumab for People with Previously Treated RAS Wild-Type, HER2-Positive Metastatic Colorectal Cancer

– First FDA-approved treatment in HER2-positive metastatic colorectal cancer –

– Combination regimen is approved for use in the second-line treatment setting and beyond –

BOTHELL, Wash.–(BUSINESS WIRE)– Seagen Inc. (Nasdaq: SGEN) today announced that the U.S. Food and Drug Administration (FDA) has granted accelerated approval to TUKYSA® (tucatinib) in combination with trastuzumab for adult patients with RASwild-type, HER2-positive unresectable or metastatic colorectal cancer that has progressed following treatment with fluoropyrimidine-, oxaliplatin- and irinotecan-based chemotherapy. TUKYSA is approved under the FDA’s Accelerated Approval Program based on tumor response rate and durability of response from the phase 2 MOUNTAINEER clinical trial. Continued approval for this indication may be contingent upon verification and description of clinical benefit in confirmatory trials. This is the first FDA-approved treatment in HER2-positive metastatic colorectal cancer. The FDA previously granted Breakthrough Therapy Designation and Priority Review for TUKYSA in this setting.

“Historically, patients with HER2-positive metastatic colorectal cancer who have progressed following frontline therapy have had poor outcomes,” said John Strickler, M.D., associate professor of medicine, Duke University Medical Center, and lead investigator for the MOUNTAINEER trial. “The FDA approval of a chemotherapy-free combination regimen that specifically targets HER2 is great news for these patients.”

“Biomarker testing is bringing new hope to people living with some types of colorectal cancer by opening the door to targeted treatments like TUKYSA for those who have RAS wild-type, HER2-positive disease,” said Michael Sapienza, CEO, Colorectal Cancer Alliance. “It is critical that physicians and patients understand the importance of comprehensive biomarker testing at diagnosis because it can inform treatment decisions and help improve outcomes.”

Results from the MOUNTAINEER trial showed a 38% overall response rate (ORR) (95% Confidence Interval [CI]: 28, 49) per blinded independent central review (BICR) in the patients who received TUKYSA in combination with trastuzumab (N=84 with a median age of 55.0 years [range: 24 to 77]). Complete responses were observed in 3.6% of patients (n=3), and partial responses were observed in 35% of patients (n=29). The median duration of response (DOR) per BICR was 12.4 months (95% CI: 8.5, 20.5). At study entry, 64% and 70% of these patients had liver or lung metastases, respectively.

The Prescribing Information for TUKYSA includes warnings and precautions for diarrhea, hepatotoxicity and embryo-fetal toxicity, some of which may be severe or fatal. In MOUNTAINEER, serious adverse reactions occurred in 22% of patients; the most common (in ≥2% of patients) were intestinal obstruction (7%), urinary tract infection (3.5%), pneumonia, abdominal pain and rectal perforation (2.3% each). The most common adverse reactions (≥20%) in patients treated with TUKYSA and trastuzumab were diarrhea, fatigue, rash, nausea, abdominal pain, infusion-related reactions and pyrexia. Adverse reactions leading to permanent discontinuation of TUKYSA occurred in 6% of patients; the most common (in ≥2% of patients) was increased alanine aminotransferase (ALT) (2.3%). Please see additional Important Safety Information below.

“The accelerated approval of TUKYSA for RAS wild-type, HER2-positive metastatic colorectal cancer expands TUKYSA-based therapy to patients across two distinct types of cancer,” said Marjorie Green, M.D., Senior Vice President and Head of Late-Stage Development, Seagen. “We believe the efficacy and safety profile of the TUKYSA and trastuzumab-based regimen further establishes its role as an important backbone of dual HER2 inhibition in the treatment of adult patients with certain HER2-expressing breast and colorectal cancers.”

The FDA’s Accelerated Approval Program allows for approval of a medicine based on a surrogate endpoint that is reasonably likely to predict clinical benefit if the medicine fills an unmet medical need for a serious condition. A global, randomized phase 3 clinical trial (MOUNTAINEER-03) is ongoing and will compare TUKYSA in combination with trastuzumab and mFOLFOX6 with standard of care, which is intended to serve as a confirmatory trial and potentially support future global regulatory submissions. Merck, known as MSD outside of the U.S. and Canada, is commercializing TUKYSA in regions outside of the U.S., Canada and Europe and plans to discuss results from the MOUNTAINEER trial with certain health authorities as it continues to accelerate the filing of TUKYSA in its territories.

For more information, please see the full Prescribing Information for TUKYSA here .

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