Background: Cbz 25 mg/m² IV Q3W + P 10 mg PO QD has an established safety profile and significantly improves overall survival (OS) vs mitoxantrone + P in pts with mCRPC previously treated with a D-containing regimen (phase III TROPIC study; NCT00417079; median OS: 15.1 vs 12.7 mos; HR: 0.70; P < 0.0001). Pooled data on file suggest that lower Grade 3–4 neutropenia rates are observed with Cbz < 25 vs ≥ 25 mg/m² (61% vs 74%). In an attempt to further improve the therapeutic index of Cbz in the second-line treatment of mCRPC, PROSELICA (NCT01308580) was designed to assess whether Cbz 20 mg/m² is associated with lower hematologic toxicity and has non-inferior efficacy compared with the standard 25 mg/m²dose. Methods: PROSELICA is a randomized, open-label, multinational, phase III study comparing the efficacy and tolerability of IV Cbz 20 with 25 mg/m², Q3W. Pts with a life expectancy > 6 mos, ECOG PS ≤ 2, confirmed mCRPC and prior therapy with a D-containing regimen are eligible. Pts are randomized 1:1 to Cbz dosing arms; all pts receive P 10 mg PO QD and are treated until disease progression, unacceptable toxicity or consent withdrawal (max. 10 cycles). Pts are stratified by ECOG PS, measurable disease and region of the world. The primary endpoint is OS (non-inferiority). Secondary endpoints include safety, progression-free survival (PCWG2 criteria), PSA and pain progression and response, tumor response and health-related quality of life. Cbz PK and pharmacogenomics will be assessed in subgroups. Planned enrollment is 1200 pts. The study started in May 2011; by 31 Dec 2012, 851 pts had been enrolled. 158 sites are enrolling pts. Based on a review of safety and efficacy endpoints, the last Data Monitoring Committee meeting (Dec 2012) recommended continuing the study without change. Clinical trial information: NCT01308580.