There is currently limited evidence to support the use of Xtandi for patients who had not or cannot receive docetaxel, before the PREVAI results become available. Median time to radiographic progression in one phase II study by Scher, 2010, was 56 weeks for chemo-naive patients and 25 weeks for patients previously treated with chemotherapy.

Several studies, in addition to Prevail, are looking at Xtandi before docetaxel. There is a phase II trial began in March 2011 comparing MDV3100 with Casodex in patients  patients who have progressed while on LHRH analogue therapy (e,g., leuprorelin) or surgical castration. This ASPIRE trial is an an open-label study intended to evaluate the effects of enzalutamide in about 150 men who are theoretically eligible to receive chemotherapy but have chosen not to do this. Another phase II study, STRIVE trial is a randomized, double-blind, multi-center clinical study of the efficacy and safety study of enzalutamide (160 mg/day) compared to bicalutamide (50 mg/day) in men with recurrent prostate cancer who have serologic and/or radiographic disease progression subsequent to primary androgen deprivation therapy (ADT). The TERRAIN trial, is a randomized, double-blind, multi-center, Phase II trial designed to test the efficacy and safety of enzalutamide compared to bicalutamide (Casodex) in men with metastatic prostate cancer already controlled by either bilateral orchiectomy (surgical castration) or ongoing androgen deprivation therapy with an LHRH agonist or an LHRH antagonist at a stable dose. There are also combination trials.

The evolution of Zytiga(arbiterone) suggests that Xtandin will show itself very effective in non-docetaxel treated patients once trials are completed, but study results to confirm this widely shared opinon are not yet in. It has the advantage of not requiring steroids which Zytiga does require.

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MDV3100 is an androgen receptor antagonist drug developed with promise for hormone refractory prostate cancer, and it is in Phase 3 clinical trials and for breast cancer. MDV3100 has binds five times stronger to the androgen receptor (AR) than Casodex, a popular hormonal drug that is currently used. It also interacts with the cancer cels in other ways.

Median time to radiographic progression in a phase II study was 56 weeks for chemo-naive patients and 25 weeks for patients previously treated with chemotherapy. A phase III trial AFFIRM (NCT00974311), in men with metastatic castration-resistant prostate cancer (CRPC) who had progressed after treatment with docetaxel-based chemotherapy, was stopped in November 2011 after a planned interim analysis showed a 37% reduction in the risk for death with MDV3100 over.Based on this the drug was approved under teh name Xtandin in mid 2012.

Another phase III trial, PREVAIL(NCT012129  is ongoing in patients who are chemo naive. There is also a phase II trial began in March 2011 comparing MDV3100 with Casodex in patients who have progressed while on LHRH analogue therapy (e,g., leuprorelin) or surgical castration.

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