[8] Common side effects include diarrhea, palmar-plantar erythrodysesthesia (burning or tingling discomfort in the hands and feet), nausea, fatigue, hepatotoxicity (liver damage), vomiting, stomatitis (inflammation of the mouth and lips), decreased appetite, abdominal pain, headache, anemia and rash.

[4] In January 2023, the US Food and Drug Administration (FDA) granted accelerated approval to tucatinib in combination with trastuzumab for RAS wild-type HER2-positive unresectable or metastatic colorectal cancer that has progressed following fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy.

[6][13][14][15][16] HER2CLIMB is a Phase 2 randomized, double-blinded, placebo-controlled study of tucatinib in combination with trastuzumab and capecitabine in patients with pretreated, unresectable locally advanced or metastatic HER2-positive breast cancer.

[9] The FDA approved tucatinib based on the results of the HER2CLIMB trial (NCT02614794) enrolling 612 subjects who had HER2-positive advanced unresectable or metastatic breast cancer and had prior treatment with trastuzumab, pertuzumab and ado-trastuzumab emtansine (T-DM1).

[10] The primary endpoint was progression-free survival (PFS), or the amount of time when there was no growth of the tumor, assessed by a blinded independent central review, evaluated in the initial 480 randomized patients.

[9][10][19] The FDA granted approval of Tukysa to Seattle Genetics, Inc.[9] Tucatinib was denied entry into the Australian Pharmaceutical Benefits Scheme in March 2021, as "the incremental cost effectiveness ratio was unacceptably high at the proposed price".