Background: Treatment of mTNBC is an unmet clinical need. First-line nab-P with gem or carbo/bevacizumab has demonstrated efficacy and safety in female patients (pts) with mTNBC. nab-P significantly improved pCR vs solvent based-paclitaxel in pts with early TNBC. The phase II/III tnAcity (triple-negative Albumin-bound paclitaxel combination international treatment study) trial will compare the efficacy and safety of 2 nab-P combination regimens (with gem orcarbo) vs gem/carbo as a control as first-line treatment for mTNBC. Methods: 790 female pts ≥ 18 yrs with measurable mTNBC will be enrolled at ≈150 sites globally per major eligibility criteria (Table 1). In phase II, 240 pts will be randomized 1:1:1 to receive nab-P 125 mg/m² + gem 1000 mg/m² (arm A), nab-P 125 mg/m² + carbo area under the curve (AUC) 2 (arm B), or gem 1000 mg/m² + carbo AUC 2 (arm C), given D 1 and 8 q3w. Pts will be treated until disease progression. Stratification factors are disease-free interval (≤ 1 yr vs > 1 yr) and prior taxane exposure (phase III only). A ranking algorithm of 5 efficacy and safety parameters will be used to identify the nab-P combination for the phase III portion in which 550 pts will be randomized 1:1 to receive the selected nab-P regimen (arm A or B) or gem/carbo. Pts in phase II will not be in the phase III population. The phase III primary endpoint is PFS by independent radiological assessment. Study design provides ≈ 90% power to detect an HR of 0.70 for PFS with a 2-sided 5% significance level. Secondary endpoints: ORR, OS, disease control rate, duration of response, and safety. Exploratory analyses include tumor biomarkers and circulating tumor cells analyses. Current enrollment as of submission: 128 pts. Clinical trial NCT01881230. Clinical trial information: NCT01881230