The FDA on August 31, 2012 approved XTANDI® (Enzalutamide) for the treatment of patients with metastatic castration-resistant prostate cancer who have previously received docetaxel. XTANDI® capsules are a product of Medivation, Inc. and Astellas Pharma US, Inc.
Tag: Prostate Cancer
XTANDI® (Enzalutamide) now approved for Late-Stage Prostate Cancer
SUMMARY:The US Food and Drug Administration (FDA) approved XTANDI® (Enzalutamide), an oral agent, formerly known as MDV3100, for men with metastatic castration-resistant prostate cancer who had progressed on TAXOTERE® (Docetaxel) based chemotherapy regimen. The approval was based on the results from the AFFIRM clinical trial. XTANDI® is an androgen receptor antagonist with a significantly higher binding affinity for the androgen receptor (AR) compared to the antiandrogen bicalutamide and there by competitively inhibits the binding of androgens to the androgen receptor. Majority of the patients with advanced prostate cancer become refractory to hormone therapy because of increased production of androgen receptors by the tumors as well as mutated androgen receptors. The superiority of this novel agent, XTANDI®, is based on the fact that the expression of androgen receptor dependent genes are downregulated with XTANDI® leading to cell death or apoptosis, whereas with bicalutamide the expression of these genes are upregulated. Further XTANDI® continues to antagonize mutated androgen receptors on the prostate tumor cells in contrast to bicalutamide which behaves as an agonist. It is thus an androgen receptor signaling inhibitor (ARSI). The AFFIRM clinical trial is a randomized, multinational phase III study in which patients who had received prior docetaxel-based chemotherapy regimens were randomized 2:1 to receive either XTANDI®, 160 mg/day or placebo. Patients treated with XTANDI® had a median survival of 18.4 months, compared with 13.6 months for men treated with placebo, with a median OS advantage of 4.8 months and a reduction in the risk of death by 37%. Scher HI, Fizazi K, Saad F, et al. J Clin Oncol 30, 2012 (suppl 5; abstr LBA1)
Radical Prostatectomy versus Observation for Localized Prostate Cancer
SUMMARY: In this study, 731 men with localized prostate cancer, diagnosed based on PSA testing, were randomly assigned to Radical Prostatectomy (RP) or Observation. The median age was 67 years, median PSA was 7.8ng/ml and median follow up was 10 years. This study concluded that RP did not significantly reduce all cause mortality or mortality related to prostate cancer. However on subset analysis, RP slightly decreased mortality among men with PSA greater than 10ng/ml and among those with intermediate and high D’Amico tumor risk score. As only 10% of the patients were less than 60 years of age, these data may not be applicable to this patient subset. Based on this study, it may be reasonable to avoid RP for those prostate cancer patients with PSA levels of 10ng/ml or less and for those with low risk tumors. Wilt TJ, Brawer MK, Jones KM, et al., for the Prostate Cancer Intervention versus Observation Trial (PIVOT) Study Group. N Engl J Med 2012; 367:203-213
Intermittent (IAD) versus continuous androgen deprivation (CAD) in hormone sensitive metastatic prostate cancer (HSM1PC) patients (pts) Results of S9346 (INT-0162), an international phase III trial
SUMMARY: Preclinical data had suggested that Intermittent Androgen Deprivation (IAD) could prolong response to therapy and alleviate side effects related to androgen deprivation. In this Phase III trial, 3040 enrolled patients with hormone sensitive metastatic prostate cancer, with PSA ≥ 5 ng/ml, were treated for 7 months with ZOLADEX® (Goserelin) plus CASODEX® (Bicalutamide). After 7 months of this combination therapy, 1535 eligible patients achieved a PSA of ≤4.0 ng/ml. These patients were then randomized to either continue ZOLADEX® plus CASODEX® (Continuous Androgen Deprivation -CAD) or receive this combination intermittently (Intermittent Androgen Deprivation – IAD). The primary endpoint was overall survival. The median Overall Survival from the time of randomization in the CAD group was 5.8 years versus 5.1 years for the IAD group. However, a subset analysis surprisingly revealed that patients with minimal metastatic disease had a statistically significant survival advantage with CAD whereas those with extensive metastatic disease had a better survival with IAD. Counter intuitive as it may be, this study has clearly suggested that the choice of CAD versus IAD should be based on the extent of metastatic disease, in patients with hormone sensitive prostate cancer. Hussain M, Tangen CM, Higano CS, et al. J Clin Oncol 2012; 30, 2012 (suppl; abstr 4)
Effect of neoadjuvant abiraterone acetate (AA) plus leuprolide acetate (LHRHa) on PSA, pathological complete response (pCR), and near pCR in localized high-risk prostate cancer (LHRPC) Results of a randomized phase II study
SUMMARY: Abiraterone acetate (ZYTIGA®) is a novel, targeted, oral androgen biosynthesis inhibitor that decreases androgen production in the adrenal glands, testes and prostate cancer cells by inhibiting a steroidal enzyme CYP17. This agent, was approved by the FDA in April, 2011 for use in combination with prednisone, for the treatment of patients with metastatic CRPC (Castrate Resistant Prostate Cancer), who have received prior chemotherapy containing docetaxel (TAXOTERE®). Patients with high risk localized prostate cancer do poorly in spite of aggressive local therapies. To improve outcomes in this patient population, the authors conducted a neoadjuvant trial in which patients with localized prostate cancer with high risk features were divided into two groups. The first group (n = 28) was treated with the LHRH analog, LUPRON® (Leuprolide acetate) for 12 weeks, followed by 12 weeks of combination treatment with LUPRON® and ZYTIGA® . The second group (n = 30) received neoadjuvant LUPRON® plus ZYTIGA® for the entire 24 week period. Patients had radical prostatectomies following their neoadjuvant therapy. Fifty eight patients were enrolled and the eligibility criteria included either T3 disease, a Gleason score of ≥7, a prostate-specific antigen (PSA) level ≥20, or a PSA velocity >2 ng/mL/year. Post prostatectomy specimen analysis revealed that patients treated with the combination of LUPRON® plus ZYTIGA® for the entire 24 week period has a complete pathologic response (pCR) or near complete pCR (≤ 5mm residual tumor) rate amounting to 34%. This benefit was seen without significant systemic toxicities. The authors concluded that neoadjuvant androgen deprivation therapy may significantly improve outcomes in high risk patients with localized disease and will need to be studied further. Taplin ME, Montgomery RB, Logothetis C, et al. J Clin Oncol 30, 2012 (suppl; abstr 4521)
Effect of MDV3100, an androgen receptor signaling inhibitor (ARSI), on overall survival in patients with prostate cancer post docetaxel Results from the phase III AFFIRM study
SUMMARY: MDV3100 is an androgen receptor antagonist with a significantly higher binding affinity for the androgen receptor (AR) compared to the antiandrogen bicalutamide and there by competitively inhibits the binding of androgens to the androgen receptor. Majority of the patients with advanced prostate cancer become refractory to hormone therapy because of increased production of androgen receptors by the tumors as well as mutated androgen receptors. The superiority of this novel agent, MDV3100, is based on the fact that the expression of androgen dependent genes are downregulated with MDV 3100 leading to cell death or apoptosis, whereas with bicalutamide the expression of these genes are upregulated. Further MDV3100 continues to antagonize mutated androgen receptors on the prostate tumor cells in contrast to bicalutamide which behaves as an agonist. It is thus an androgen receptor signaling inhibitor (ARSI). The AFFIRM clinical trial is a randomized, multinational phase III study in which patients who had received prior docetaxel-based chemotherapy regimens were randomized 2:1 to receive either MDV3100, 160 mg/day or placebo. Patients treated with MDV3100 had a median survival of 18.4 months, compared with 13.6 months for men treated with placebo, with a median OS advantage of 4.8 months and a reduction in the risk of death by 37%. Scher HI, Fizazi K, Saad F, et al. J Clin Oncol 30, 2012 (suppl 5; abstr LBA1)
ABIRATERONE ACETATE (AA) PLUS LOW DOSE PREDNISONE (P) IMPROVES OVERALL SURVIVAL (OS) IN PATIENTS (PTS) WITH METASTATIC CASTRATIONRESISTANT PROSTATE CANCER (MCRPC) WHO HAVE PROGRESSED AFTER DOCETAXEL-BASED CHEMOTHERAPY (CHEMO) RESULTS OF COU-AA-301, A RANDOMIZED DOUBLE-BLIND PLACEBO-CONTROLLED PHASE III STUDY
SUMMARY: Abiraterone acetate (ZYTIGA®) is a novel, targeted, oral androgen biosynthesis inhibitor that decreases androgen production in the adrenal glands, testes and prostate cancer cells by inhibiting a steroidal enzyme CYP17. This agent was approved by the FDA in April, 2011 for use in combination with prednisone for the treatment of patients with metastatic CRPC (Castrate Resistant Prostate Cancer), who have received prior chemotherapy containing docetaxel (TAXOTERE®). This approval was based on a randomized, placebo controlled phase III trial which included 1195 patients with metastatic CRPC, previously treated with one or two chemotherapy regimens, at least one of which contained TAXOTERE®. Patients were randomly assigned (2:1) to receive either ZYTIGA® plus low-dose prednisone (N=797) or placebo plus low dose prednisone (N=398). Treatment was continued until disease progression. The primary endpoint was overall survival. Results from a pre-specified interim analysis demonstrated that patients treated with ZYTIGA® plus low-dose prednisone showed a statistically significant improvement in overall survival as well secondary endpoints such as, time to PSA progression and radiographic progression-free survival. Treatment with ZYTIGA® resulted in a 35 percent reduction in the risk of death and a 36 percent increase in median survival compared with placebo. The most common adverse events were edema, hypertension, joint discomfort, diarrhea, hypokalemia, and hypophosphatemia. This novel therapeutic agent is a major and important medical advance in the management of patients with metastatic CRPC. With the availability of several new agents for the treatment of CRPC, it may be important to properly sequence these available drugs to get the best of each treatment intervention and thus improve overall survival. Annals of Oncology 21 (Supplement 8): viii1-viii12. 2010. Ref Type: Abstract
Prednisone plus cabazitaxel or mitoxantrone for metastatic castration-resistant prostate cancer progressing after docetaxel treatment a randomised open-label trial
SUMMARY: The TROPIC trial (Treatment of Hormone-Refractory Metastatic Prostate Cancer Previously Treated With a docetaxel (TAXOTERE®)- Containing Regimen) involved 755 men in 26 countries with metastatic prostate cancer who were castration resistant. Patients were randomized to receive either Cabazitaxel (JEVTANA®) 25 mg/m2 or Mitoxantrone 12 mg/m2 three times a week and both groups received prednisone 10 mg daily through out the course of their treatment. The combination of JEVTANA® and prednisone resulted in median overall survival of 15.1 months compared to 12.7 months for the Mitoxantrone group. There was a 30% reduction in the risk of death for the JEVTANA® group. This led to the approval of JEVTANA® for the treatment of hormone-refractory metastatic prostate cancer, previously treated with a TAXOTERE® containing regimen. Lancet 2010;376:1147-1154
Sipuleucel-T Immunotherapy for Castration-Resistant Prostate Cancer
SUMMARY: Sipuleucel-T (PROVENGE®) is a therapeutic cancer vaccine developed to boost the patients immune system to fight prostate cancer. In a double blind randomized phase III trial, 512 patients with metastatic castrate-resistant prostate cancer received PROVENGE® vaccine (341) or a placebo (171). There was a 4.1 month improvement in median survival for patients receiving the vaccine compared to those receiving a placebo (25.8 versus 21.7 months) and a 22% reduction in the risk of death in the vaccine group. Because of the slow onset of action of any vaccine therapy, this option may be appropriate for individuals with less aggressive disease. N Engl J Med 2010;363:411-422
Oncoprescribe Blog Prostate Cancer – Androgen Independent or Castrate Resistant
It is not semantics anymore. Prostate Cancer is a heterogeneous disease. It appears that in patients touted to have Hormone Refractory Prostate Cancer (HRPC), the cells continue to produce androgen receptor message even in the absence of androgens. The tumor cells are therefore not androgen independent. On the contrary, they continue to thrive, having access to androgens or androgen precursors, by various different mechanisms. It is for this reason imperative that one continue chemical castration with LHRH agonists concurrently with other lines of treatment including chemotherapy.
So the appropriate term should be Castrate Resistant Prostate Cancer rather than Androgen Independent Prostate Cancer.