On February 12, 2021 Seagen Inc. (Nasdaq:SGEN) reported that the European Commission (EC) has granted marketing authorization for TUKYSA (tucatinib) in combination with trastuzumab and capecitabine for the treatment of adult patients with HER2-positive locally advanced or metastatic breast cancer who have received at least two prior anti-HER2 treatment regimens (Press release, Seagen, FEB 12, 2021, View Source [SID1234575035]). TUKYSA is an oral, small molecule tyrosine kinase inhibitor (TKI) of HER2, a protein that contributes to cancer cell growth.1,2
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"This approval is a significant advancement for patients in Europe, who will for the first time have an approved medicine demonstrating a survival benefit for HER2-positive metastatic breast cancer after disease progression following two standard anti-HER2 treatment regimens," said Prof. Dr. Med Volkmar Mueller, Deputy Director at the University Medical Center Hamburg-Eppendorf, Hamburg, Germany and investigator for the pivotal trial. "In the HER2CLIMB pivotal trial, the tucatinib combination regimen improved overall and progression-free survival compared to trastuzumab and capecitabine alone, including in patients with active, untreated or progressing brain metastases, a population with significant unmet need."
"The TUKYSA combination is a landmark therapy for patients with HER2-positive metastatic breast cancer with or without brain metastases, extending overall survival in these patients after two prior anti-HER2 treatment regimens," said Clay Siegall, Ph.D., Chief Executive Officer at Seagen. "We are pleased TUKYSA is now approved in Europe, and we look forward to further collaborating with individual countries to ensure it is available to patients."
The Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency adopted a positive opinion for TUKYSA in December 2020. The approval of TUKYSA is valid in all countries of the European Union, as well as Norway, Liechtenstein, Iceland and Northern Ireland.
HER2CLIMB Efficacy and Safety
Patients who received TUKYSA in combination with trastuzumab and capecitabine in the pivotal trial had a 46 percent reduction in the risk of cancer progression or death (PFS), the primary endpoint, compared to patients who received trastuzumab and capecitabine alone (hazard ratio (HR)=0.54 [95% Confidence Interval (CI): 0.42, 0.71]; p<0.00001) and improved overall survival with a reduction in the risk of death by 34 percent (HR=0.66 [95% CI: 0.50, 0.87]; p=0.0048). The most common adverse reactions occurring in 20 percent or more of patients who received TUKYSA were diarrhea, nausea, vomiting, stomatitis, AST increase, ALT increase, and rash.1
The pivotal trial, HER2CLIMB, is a randomized (2:1), double-blind, placebo-controlled, active comparator, global trial that enrolled 612 patients with HER2-positive unresectable locally advanced or metastatic breast cancer who had previously received, either separately or in combination, trastuzumab, pertuzumab, and trastuzumab emtansine (T-DM1 SmPC).
About HER2-Positive Breast Cancer
Patients with HER2-positive breast cancer have tumors with high levels of a protein called human epidermal growth factor receptor 2 (HER2), which promotes the growth of cancer cells. In 2020, more than two million new cases of breast cancer were diagnosed worldwide, including 531,086 in Europe.3 Between 15 and 20 percent of breast cancer cases are HER2-positive.4 HER2-positive breast cancer tends to be more aggressive and more likely to recur than HER2-negative breast cancer.4,5,6 Up to 50 percent of metastatic HER2-positive breast cancer patients develop brain metastases over time.7,8,9
About TUKYSA (tucatinib)
TUKYSA is an oral medicine that is a tyrosine kinase inhibitor of the HER2 protein. In vitro (in lab studies), TUKYSA inhibited phosphorylation of HER2 and HER3, resulting in inhibition of downstream MAPK and AKT signaling and cell growth (proliferation), and showed anti-tumor activity in HER2-expressing tumor cells. In vivo (in living organisms), TUKYSA inhibited the growth of HER2-expressing tumors. The combination of TUKYSA and the anti-HER2 antibody trastuzumab showed increased anti-tumor activity in vitro and in vivo compared to either medicine alone.
U.S. Important Safety Information
Warnings and Precautions
Diarrhea – TUKYSA can cause severe diarrhea including dehydration, hypotension, acute kidney injury, and death. In HER2CLIMB, 81% of patients who received TUKYSA experienced diarrhea, including 12% with Grade 3 diarrhea and 0.5% with Grade 4 diarrhea. Both patients who developed Grade 4 diarrhea subsequently died, with diarrhea as a contributor to death. The median time to onset of the first episode of diarrhea was 12 days and the median time to resolution was 8 days. Diarrhea led to dose reductions of TUKYSA in 6% of patients and discontinuation of TUKYSA in 1% of patients. Prophylactic use of antidiarrheal treatment was not required on HER2CLIMB.
If diarrhea occurs, administer antidiarrheal treatment as clinically indicated. Perform diagnostic tests as clinically indicated to exclude other causes of diarrhea. Based on the severity of the diarrhea, interrupt dose, then dose reduce or permanently discontinue TUKYSA.
Hepatotoxicity – TUKYSA can cause severe hepatotoxicity. In HER2CLIMB, 8% of patients who received TUKYSA had an ALT increase >5 × ULN, 6% had an AST increase >5 × ULN, and 1.5% had a bilirubin increase >3 × ULN (Grade ≥3). Hepatotoxicity led to dose reduction of TUKYSA in 8% of patients and discontinuation of TUKYSA in 1.5% of patients.
Monitor ALT, AST, and bilirubin prior to starting TUKYSA, every 3 weeks during treatment, and as clinically indicated. Based on the severity of hepatotoxicity, interrupt dose, then dose reduce or permanently discontinue TUKYSA.
Embryo-Fetal Toxicity – TUKYSA can cause fetal harm. Advise pregnant women and females of reproductive potential risk to a fetus. Advise females of reproductive potential, and male patients with female partners of reproductive potential, to use effective contraception during TUKYSA treatment and for at least 1 week after the last dose.
Adverse Reactions
Serious adverse reactions occurred in 26% of patients who received TUKYSA. Serious adverse reactions in ≥2% of patients who received TUKYSA were diarrhea (4%), vomiting (2.5%), nausea (2%), abdominal pain (2%), and seizure (2%). Fatal adverse reactions occurred in 2% of patients who received TUKYSA including sudden death, sepsis, dehydration, and cardiogenic shock.
Adverse reactions led to treatment discontinuation in 6% of patients who received TUKYSA; those occurring in ≥1% of patients were hepatotoxicity (1.5%) and diarrhea (1%). Adverse reactions led to dose reduction in 21% of patients who received TUKYSA; those occurring in ≥2% of patients were hepatotoxicity (8%) and diarrhea (6%).
The most common adverse reactions in patients who received TUKYSA (≥20%) were diarrhea, palmar-plantar erythrodysesthesia, nausea, fatigue, hepatotoxicity, vomiting, stomatitis, decreased appetite, abdominal pain, headache, anemia, and rash.
Lab Abnormalities
In HER2CLIMB, Grade ≥3 laboratory abnormalities reported in ≥5% of patients who received TUKYSA were: decreased phosphate, increased ALT, decreased potassium, and increased AST. The mean increase in serum creatinine was 32% within the first 21 days of treatment with TUKYSA. The serum creatinine increases persisted throughout treatment and were reversible upon treatment completion. Consider alternative markers of renal function if persistent elevations in serum creatinine are observed.
Drug Interactions
Strong CYP3A or Moderate CYP2C8 Inducers: Concomitant use may decrease TUKYSA activity. Avoid concomitant use of TUKYSA.
Strong or Moderate CYP2C8 Inhibitors: Concomitant use of TUKYSA with a strong CYP2C8 inhibitor may increase the risk of TUKYSA toxicity; avoid concomitant use. Increase monitoring for TUKYSA toxicity with moderate CYP2C8 inhibitors.
CYP3A Substrates: Concomitant use may increase the toxicity associated with a CYP3A substrate. Avoid concomitant use of TUKYSA where minimal concentration changes may lead to serious or life-threatening toxicities. If concomitant use is unavoidable, decrease the CYP3A substrate dosage.
P-gp Substrates: Concomitant use may increase the toxicity associated with a P-gp substrate. Consider reducing the dosage of P-gp substrates where minimal concentration changes may lead to serious or life-threatening toxicity.
Use in Specific Populations
Lactation: Advise women not to breastfeed while taking TUKYSA and for at least 1 week after the last dose.
Renal Impairment: Use of TUKYSA in combination with capecitabine and trastuzumab is not recommended in patients with severe renal impairment (CLcr < 30 mL/min), because capecitabine is contraindicated in patients with severe renal impairment.
Hepatic Impairment: Reduce the dose of TUKYSA for patients with severe (Child-Pugh C) hepatic impairment.