The FDA has approved Seattle Genetics' breast cancer drug Tukysa (tucatinib) four months ahead of schedule. This approval includes its use in certain patients whose disease has spread to the brain. Tukysa is approved in combination with Roche's Herceptin (trastuzumab) and capecitabine for adults with advanced unresectable or metastatic HER2-positive breast cancer. It specifically covers patients with brain metastases who have undergone one or more HER2-targeting therapy regimens for metastatic disease.
This marks Seattle Genetics' first approval in the field of breast cancer. The drug is priced at $18,500 for a 30-day supply, with the average treatment course costing around $111,000 per patient. Seattle Genetics already has two other cancer drugs on the market: Adcetris (brentuximab vedotin) for certain forms of lymphoma and Padcev (enfortumab vedotin) for advanced bladder cancer.
The FDA had previously granted Tukysa Breakthrough Therapy designation and a faster Priority Review, reducing the review time to six months from the standard ten. The approval process utilized the Real Time Oncology Review (RTOR) pilot program, enabling the FDA to access key data prior to the official filing. This approach allows the FDA's review team to start their evaluation earlier and engage in pre-submission communication with the applicant.
Approval of the Tukysa combination was based on the HER2CLIMB trial, a randomized, double-blind, placebo-controlled study involving 612 patients with HER2-positive unresectable locally advanced or metastatic breast cancer. Participants had previously received Roche's Herceptin, Perjeta (pertuzumab), or Kadcyla (ado-trastuzumab emtansine), either alone or in combination, with 48% of patients having a presence or history of brain metastases.
The primary efficacy endpoint was progression-free survival, assessed by blinded independent review in the first 480 randomized patients. Additional efficacy measures included overall survival and progression-free survival in patients with brain metastases or a history thereof. Results indicated a 46% reduction in the risk of cancer progression or death among patients treated with the Tukysa combination compared to those treated with Herceptin and capecitabine alone.
Serious adverse events were reported in 26% of patients treated with Tukysa, including diarrhea (4%) and vomiting (2.5%). Tukysa functions as a tyrosine kinase inhibitor targeting the HER2 protein, triggering a chain reaction that exerts anti-tumour activity in tumours expressing the protein, which is found in approximately 15%-20% of breast cancers.
