Medivation and Astellas Announce Data From Phase 1-2 Trial of MDV3100 in Advanced Prostate Cancer Patients
Product News Mar 09, 2011
Medivation, Inc. and Astellas Pharma Inc. have announced positive, new, long-term follow-up data from the Phase 1-2 trial of MDV3100 in patients with advanced prostate cancer. MDV3100 is a novel, triple-acting, oral androgen receptor antagonist. These new results showed that MDV3100 continues to show durable antitumor activity as evaluated by median times to prostate-specific antigen (PSA) progression and radiographic progression.
These findings confirm the initial Phase 1-2 results published in The Lancet, in which MDV3100 consistently demonstrated anti-tumor activity in both chemotherapy-naïve and post-chemotherapy patients across endpoints, as evaluated by PSA levels, radiographic findings and circulating tumor cell (CTC) counts.
"We are very encouraged by these promising new, long-term efficacy findings, which continue to demonstrate the antitumor activity of MDV3100 and give us confidence that MDV3100 has the potential to benefit patients with advanced prostate cancer," said Lynn Seely, M.D., chief medical officer of Medivation.
Long-Term Follow-Up Results
A total of 140 men with progressive disease were enrolled in the Phase 1-2 trial between July 2007 and December 2008. Of those, 18 remained on active treatment (16 chemotherapy-naive and 2 post-chemotherapy) at the time of this analysis.
PSA progression data were calculated using three distinct reporting criteria: the criteria specified in the Phase 1-2 trial protocol; the most recent published PSA reporting consensus criteria (the Prostate Cancer Clinical Trials Working Group 2, or PCWG2, criteria)(1); and an older commonly used reporting method (the Prostate-Specific Antigen Working Group 1, or PSAWG1, criteria)(2).
The protocol-specified criteria define PSA progression as a 25% increase in PSA from starting baseline, provided that the increase is at least 5 ng/mL. This is the most liberal approach, and will produce the longest times to progression. The PCWG2 criteria define PSA progression as a 25% increase in PSA from nadir (i.e., from the lowest level of PSA attained by the patient on study), provided that the increase is at least 2 ng/mL.
Under the PSAWG1 criteria, PSA progression requires: a 50% increase in PSA above nadir for patients who experienced a PSA decline of 50% on treatment; a 25% increase in PSA above nadir for patients who experienced a PSA decline < 50% on treatment; and a 25% increase in PSA above starting baseline for patients who did not experience any PSA decline on treatment; provided in each case that the PSA increase was at least 5 ng/mL. This is an intermediate approach to defining PSA progression, producing times to progression between those produced using the other two approaches.
Circulating tumor cell counts were available for 128 of 140 patients. Of those, 70 of 77 (91%) who had favorable pre-treatment counts ( < 5 cells/7.5 mL blood) remained favorable post-treatment, and 25 of 51 patients (49%) converted from unfavorable pre-treatment counts to favorable post-treatment counts.
"These positive long-term findings in both chemotherapy-naïve and post-chemotherapy advanced prostate cancer patients provide further support for our expanded development program into earlier-stage prostate cancer patients," said Steven Ryder, M.D., president, Astellas Pharma Global Development. "In addition to the ongoing Phase 3 PREVAIL trial, which is currently enrolling men with advanced prostate cancer who are chemotherapy-naïve, we and our partner Medivation plan to initiate two Phase 2 trials in earlier-stage prostate cancer in the first half of this year."
The new long-term follow-up findings will be presented in a poster session at the American Society of Clinical Oncology's Genitourinary Cancers Symposium (ASCO-GU) in Orlando, Fla. on Thursday, February 17 (poster board #A71). The poster will include the most up-to-date data from the trial and will expand upon the results originally submitted in the abstract. The abstract (#177), titled "Antitumor activity of MDV3100 in pre- and post-docetaxel advanced prostate cancer: long-term follow-up of the Phase 1-2 study," is currently available on the ASCO website at www.ASCO.org.