Background: Chemotherapy treatments that offer improved quality of life are needed. Tesetaxel (T) is a novel, oral taxane that has potential advantages over currently available taxanes, including: oral administration with a low pill burden and Q3W dosing; no history of hypersensitivity reactions (HSRs); and improved activity against chemotherapy-resistant tumors (Shionoya 2003; Chan 2006). 555 pts have been treated with T in clinical studies. In MBC, T was shown to have robust single-agent activity in 2 multicenter, Phase 2 studies. In TOB203, 46 pts with HER2- MBC received single-agent T Q3W, including 38 pts with HR+ MBC, the population being enrolled in CONTESSA, an ongoing Phase 3 study. Methods: Pts eligible for TOB203 had HER2- MBC, ECOG PS 0-1, measurable disease and adequate organ function. Adjuvant chemotherapy (including taxanes) was allowed. T was administered orally as first-line chemotherapy at 27 mg/m² on Day 1 of a 21-day cycle, with escalation to 35 mg/m² in subsequent cycles depending on tolerability, without anti-allergy premedication. ORR was the primary endpoint. Final results are provided for all 38 HR+ pts who received T Q3W. Results: Median age: 58 (36-80 yrs); 74% received prior endocrine therapy; 68% received prior chemotherapy in the adjuvant setting (53% taxane-containing regimen; 50% anthracycline-containing regimen); median organ systems involved: 2 (1-4); 82% had visceral disease. The confirmed ORR per RECIST 1.1 in all 38 pts was 45% (95% CI: 29% - 62%); median duration of response was 8.7 mo (95% CI: 4.3 – 13.6 mo); median PFS was 5.7 mo (95% CI: 4.1 – 9.8 mo). In the 24 HR+ pts receiving 27 mg/m² without escalation, Grade ≥ 3 neutropenia, the most common Grade ≥ 3 AE, occurred in 29% of pts (febrile neutropenia 4%), there were no cases of Grade ≥ 3 peripheral neuropathy, and the incidence of Grade 1/2 alopecia was 29%/21%. There were no HSRs or study drug-related deaths. Conclusions: T, as a single agent, was well tolerated with significant activity in pts with HER2-, HR+ MBC. T is currently being investigated in CONTESSA, a multinational, multicenter, randomized, Phase 3 study in pts with HER2-, HR+ MBC (NCT03326674). Clinical trial information: NCT01221870