Background:Standard intravenous (IV) paclitaxel is associated with hypersensitivity/toxicity. Alternative IV formulations have improved tolerability but still require frequent hospital visits and IV infusion. DHP107 is a novel oral formulation of paclitaxel that is approved in South Korea for the treatment of gastric cancer.Methods:This multicenter, phase II study using a Simon’s two-stage design investigated the efficacy and safety of DHP107 200 mg/m²administered orally twice daily on days 1, 8, and 15 every 4 weeks for the first-line treatment of recurrent or metastatic HER2-negative breast cancer.Results:Thirty-six patients were enrolled and 31 were assessable for efficacy. Patient median age was 57 years (range = 34–81) and 11 (31%) had triple-negative disease. A median of seven cycles (range = 1–28) of DHP107 was administered. Objective response rate was 55% (17 patients), all partial responses, according to the investigator’s decision and independent central review (ICR), and 44% (4/9 patients) in those with triple-negative disease. Disease control rate (partial response and stable disease) was 74% (23 patients) according to the investigator’s decision and ICR. In the intention-to-treat (ITT) population of all enrolled participants, the objective response rate was 50% (18/36 patients). Median progression-free survival was 8.9 months [95% confidence interval [CI]: 5.2–12.3) and median time to treatment failure was 8.0 months (95% CI: 4.2–10.0). DHP107 had an acceptable toxicity profile. All patients experienced treatment-emergent adverse events; the most common adverse events were decreased neutrophil count (81% all grades and 78% grade ⩾ 3) followed by peripheral sensory neuropathy (61% all grades and 8% grade 3). However, there was no febrile neutropenia or sepsis.Conclusion:DHP107 showed promising efficacy and acceptable tolerability in this phase II study and is currently being investigated in the OPTIMAL phase III study (NCT03315364).Trial registration:This trial was registered with ClinicalTrials.gov identifier: NCT03315364.