Oral paclitaxel plus encequidar shows superior tumor response in metastatic breast cancer
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Among patients with metastatic breast cancer, oral paclitaxel and encequidar demonstrated superior tumor response rate compared with IV paclitaxel, according to research presented at ASCO 2021.
“Paclitaxel cannot be administered orally, because it is a substrate of the P-glycoprotein (P-gp),” Gerardo Antonio Umanzor Funez, MD, of Liga Contra El Cáncer, San Pedro Sula, Honduras, said during the presentation. “The bioavailability of paclitaxel is improved when oral paclitaxel is administered with the highly specific, potent P-gp inhibitor encequidar. There is an unmet need for clinical active oral chemotherapies with improved tolerability profiles for the treatment of breast cancer in the metastatic setting.”
Funez and colleagues evaluated data from a phase 3, open label randomized study among women with histologically or cytologically confirmed metastatic breast cancer who were recommended IV paclitaxel. The investigators randomly assigned 402 patients 2:1 to receive oral paclitaxel at 205 mg/m2 daily for 3 consecutive days each plus encequidar at 12.9 mg an hour before each dose of paclitaxel, or to receive IV paclitaxel at 175 mg/m2 infused over a 3-hour period once every 3 weeks.
The researchers determined that oral paclitaxel plus encequidar had a confirmed tumor response rate of 35.8%, compared with 23.4% among those who received IV paclitaxel.
Funez and colleagues found that among those with HR-positive/HER2-negative disease, patients who received oral paclitaxel plus encequidar had a tumor response rate of 44.8%, compared with a rate of 21.4% among those who received IV paclitaxel. Those with triple-negative breast cancer also had a better tumor response with oral paclitaxel plus encequidar, with a rate of 30.5%, compared with 20.2% in those who received IV paclitaxel.
They found that the tumor response rates were similar with both treatment options among those with HER2-positive disease, with a rate of 49% in those who received oral paclitaxel plus encequidar and 47.4% in those who received IV paclitaxel.
Among patients with unknown HER2 status, the response rate was 58.8% in those who received oral paclitaxel plus encequidar and 14.3% in those who received IV paclitaxel.
Funez said oral paclitaxel plus encequidar “achieved the primary efficacy endpoint of the trial, superiority in the confirmed radiological response rate when confirmed to [IV paclitaxel] at the dose schedule approved for the treatment of patients with metastatic breast cancer.”
He added that oral paclitaxel plus encequidar demonstrated improved tumor response rates across subgroups, particularly in those with HER-negative/PR-positive disease.
“Oral paclitaxel and encequidar is the first world taxane to demonstrate superiority in radiologically confirmed tumor response rate, with reduced neuropathy and alopecia compared to IV paclitaxel in women with metastatic breast cancer,” Funez said.
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