A randomized, double-blind, placebo-controlled phase II study of maintenance therapy with tasquinimod in patients with metastatic castration-resistant prostate cancer responsive to or stabilized during first-line docetaxel chemotherapy

Background: This phase II study was conducted to assess clinical efficacy of tasquinimod maintenance therapy in patients with metastatic castrate-resistant prostate cancer not progressing during first-line docetaxel-based therapy. Patients and methods: Patients were randomly assigned (1: 1) to receive tasquinimod (0.25-1.0 mg/day orally) or placebo. The primary end point was radiologic progression-free survival (rPFS); secondary efficacy end points included: overall survival (OS); PFS on next-line therapy (PFS 2) and symptomatic PFS, assessed using the Brief Pain Inventory (BPI) questionnaire and analgesic use. Quality of life was measured by the Functional Assessment of Cancer Therapy-Prostate (FACT-P) questionnaire and by the EuroQol-5 Dimension Quality of Life Instrument (EQ-5D). Adverse events were recorded. Results: A total of 219 patients were screened and 144 patients randomized. The median duration of treatment was 18.7 weeks (range 0.6-102.7 weeks) for the tasquinimod arm and 19.2 weeks (range 0.4-80.0 weeks) for the placebo arm. Median (90% CI) rPFS was 31.7 (24.3-53.7) and 22.7 (16.1-25.9) weeks in the tasquinimod and placebo arms, respectively [HR (90% CI) 0.6 (0.4-0.9), P=0.0162]. The median OS was not reached because only 14 deaths occurred by the cut-off date. No statistically significant differences between treatment arms were noted for symptomatic PFS, PFS 2, BPI score, FACT-P score, or EQ-5D. The incidence of any treatment emergent adverse event (TEAE) was similar in the tasquinimod and placebo arms (97.2% versus 94.3%, respectively), whereas severe TEAEs (NCI-CTC Grade 3-5) incidence was higher in the tasquinimod group (50.7% versus 27.1%). Conclusions: Randomized trials testing new drugs as maintenance can be successfully conducted after chemotherapy in castrate-resistant prostate cancer. Maintenance tasquinimod therapy significantly reduced the risk of rPFS by 40%.