ATLAB Pharma SAS announced that positive results of a phase II study of ATL101 (Lutetium-177 anti-PSMA antibody) on 47 patients with progressive metastatic castrate-resistant prostate cancer (mCRPC) have been presented at the ASCO 2013 Genitourinary cancer meeting.
Weill Cornell’s Dr. Scott Tagawa presented the results and the survival update. The study was performed at Weill Cornell Medical College/NewYork-Presbyterian Hospital and Memorial Sloan-Kettering Cancer Center.
ATL101 is a new targeted radiotherapy experimental drug for treating prostate cancer. ATL101 combines the humanized J591 monoclonal antibody targeting prostate-specific membrane antigen (PSMA) plus the Lutetium-177 radioisotope, creating the first tumor-specific delivery system able to target radiation to radio-sensitive prostate cancer cells wherever they are in the body.
In the study, ATL101 was administered as a single intravenous injection at 2 radioactivity dose levels, 65 or 70 mCi/m^2, in two consecutive cohorts of patients with metastatic castration-resistant prostate cancer (mCRPC). A third cohort was added at the 70mCi/m^2 dose. All patients had failed up to 4 hormonal therapies, and 55% of the patients had failed at least one docetaxel-containing chemotherapy regimen.
The results suggested a statistically significant relationship between injected dose and antitumor activity. The percentage of patients achieving PSA decline over 30% (30% PSA decline) increased from 13 % in Cohort (1) to 47 % in Cohort (2). The expansion Cohort 3 confirmed the rates of 30% PSA decline at 47% of patients. A treatment effect on the circulating tumor cells (CTC) count was also observed. Moreover, median overall survival (OS) significantly increased with the injected dose of radioactivity from 11.9 months in cohort (1) to 21.8 months in cohorts 2 and 3. The treatment was well tolerated with predictable, transient, and manageable dose-related changes in blood cell counts. Patients experienced no serious symptomatic side effects.
ATL101 is actively studied at Weill-Cornell Medical College/New York-Presbyterian Hospital in Phase I trials evaluating fractionated administration and combination with docetaxel. In addition, a randomized, multi-centre Phase II trial of ATL-101 in patients who have relapsed following surgery and/or radiation therapy and hormonal therapy but who do not yet have demonstrable metastatic disease is ongoing at several clinical sites in the USA. Click here to view the Phase II trial at clinicaltrials.gov.