The HER2CLIMB-05 trial is a randomized, double-blind, phase 3 study assessing tucatinib versus placebo in combination with trastuzumab and pertuzumab as maintenance therapy for metastatic or locally advanced unresectable HER2-positive breast cancer. The trial, sponsored by Seagen (a Pfizer subsidiary), is currently active but no longer enrolling participants.
HER2CLIMB-05 (NCT05132582) is an ongoing randomized, double-blind, phase 3 trial investigating whether the addition of tucatinib—an oral, selective HER2-directed tyrosine kinase inhibitor—to a trastuzumab and pertuzumab backbone improves outcomes compared with dual HER2 antibody therapy alone as maintenance in metastatic HER2-positive breast cancer. The trial is sponsored by Seagen, a wholly owned subsidiary of Pfizer, and is currently active but no longer recruiting.
Eligible participants carry a diagnosis of HER2-positive breast cancer that is either metastatic or locally advanced and unresectable. Subjects are randomized to receive tucatinib or matched placebo alongside standard-of-care trastuzumab and pertuzumab, with both investigators and participants blinded to treatment assignment. The dual-antibody combination of trastuzumab and pertuzumab represents an established HER2-targeted regimen, and the trial aims to determine whether layering a small-molecule HER2 kinase inhibitor onto this backbone confers additional clinical benefit in the maintenance setting.
Tucatinib has previously demonstrated efficacy in heavily pretreated HER2-positive metastatic breast cancer—including cases with brain metastases—in the HER2CLIMB-01 trial. HER2CLIMB-05 extends this investigation to an earlier maintenance context, where the therapeutic goal shifts toward prolonging disease control following initial response. Safety profiling of the triplet regimen is a co-primary objective, given the potential for additive toxicity when combining a TKI with dual monoclonal antibody therapy.
Full efficacy and safety results from HER2CLIMB-05 have not yet been publicly reported. As the trial remains active without further enrollment, outcome data are anticipated in a future disclosure.
Key points
- HER2CLIMB-05 is a phase 3, randomized, double-blind trial evaluating tucatinib plus trastuzumab and pertuzumab versus placebo plus trastuzumab and pertuzumab as maintenance therapy in metastatic HER2-positive breast cancer.
- The trial targets patients with metastatic or locally advanced unresectable HER2-positive breast cancer and is sponsored by Seagen, a Pfizer subsidiary.
- Tucatinib is a selective oral HER2 tyrosine kinase inhibitor previously validated in the HER2CLIMB-01 trial for pretreated metastatic HER2-positive disease.
- The study is active but no longer recruiting; efficacy and safety results have not yet been publicly disclosed.
- Safety assessment of the tucatinib-trastuzumab-pertuzumab triplet combination is a co-objective, given the novel combination in the maintenance setting.
Why it matters
If tucatinib augments the efficacy of dual HER2 antibody maintenance therapy, HER2CLIMB-05 could redefine the standard maintenance approach for metastatic HER2-positive breast cancer and expand the clinical role of oral HER2-directed TKIs beyond later lines of therapy.