Tesetaxel, an advanced-generation oral taxane, as first-line treatment in women with metastatic breast cancer.

Abstract

TPS123 Background: Taxanes such as docetaxel and paclitaxel are among the most active agents in metastatic breast cancer (MBC). Tesetaxel is an active novel taxoid that overcomes disadvantages of these standard agents. Among other features, the drug is taken by mouth as an oral capsule. Tesetaxel is not a substrate for P-glycoprotein, a major cause of taxane resistance. The drug is not associated with hypersensitivity reactions, thus obviating the need for both premedications and extended medical/nursing observation. Preclinical studies in human tumor xenografts show activity in taxane-resistant BC as well as reduced peripheral neuropathy. In dose-ranging studies, 8 of 13 evaluable patients (pts) (62%) with MBC achieved prolonged stable disease (SD) (i.e., up to 24 cycles) when the drug was administered once every 3 weeks (wks). A phase II trial of tesetaxel (27-35 mg/m2 p.o. Q3 wks) showed a 38% partial response (PR) rate among 34 pts who had progressed after an anthracycline-containing regimen. Based on these favorable data, we have initiated a multicenter study to assess the efficacy and safety of tesetaxel as 1st-line therapy in MBC. Methods: Eligible patients have: Stage IV, HER2-negative MBC; ECOG PS 0-1; adequate organ function; no prior chemotherapy for MBC, although 1 adjuvant regimen is allowed. Tesetaxel is administered Q3 wks at a starting dose of 27 mg/m2 p.o., which can be increased to 35 mg/m2 depending on tolerability. A Simon mini-max two-stage design is being used. Target accrual is 25 pts. Response rate, per RECIST 1.1 criteria, is the primary endpoint. Other objectives include progression-free survival and safety. Assuming initial results are favorable, we will examine a weekly dosing schedule in a second pt cohort.