Recent Progress in the Treatment of Advanced Prostate Cancer With Intermittent Dose-Intense Calcitriol (DN-101)

Docetaxel is becoming standard therapy for androgen-independent prostate cancer (AIPC), and investigational agents are being added to docetaxel to assess potential additive effects and synergy. Although one of these agents, calcitriol, has repeatedly demonstrated antiproliferative properties against cancer of the prostate, breast, colon, and lung, the antineoplastic activity of calcitriol requires superphysiologic levels. Unfortunately, chronic exposure to superphysiologic levels of calcitriol causes hypercalcemia and resulting toxicity. Therefore, a host of analogues of calcitriol have been investigated for antineoplastic function, including intermittent dose-intense calcitriol, or DN-101. Because of encouraging results from phase II studies of DN-101 combined with docetaxel, the ASCENT (AIPC Study of Calcitriol Enhancement of Taxotere) phase II trial investigated docetaxel plus DN-101 versus docetaxel plus placebo in 250 men with metastatic AIPC and an abnormal baseline prostate-specific antigen (PSA) level. Although the ASCENT trial did not achieve its primary endpoint for increased PSA response, there was a significant trend in PSA response rate in the DN-101 arm. DN-101 in combination with docetaxel seems to improve overall survival and, interestingly, has a favorable safety profile compared with docetaxel alone. The DN-101/docetaxel combination is currently being studied in a much larger international trial, ASCENT-2.