A phase III trial studying Alpharadin (radium 223-chloride) in prostate cancer patients has been halted early based on positive survival results.
Bayer AG/Algeta ASA stopped the trial of their targeted radioactive drug for the treatment of symptomatic bone metastases in advanced prostate cancer patients based on interim analysis findings of a significant 2.8-month median survival benefit, the companies announced June 6. The positive data could speed a regulatory filing for the drug, which the companies had hoped to file in the second half of 2012.
"Now clearly we will be doing everything we can with our partner Bayer to accelerate that," Algeta CEO Andrew Kay said in an interview. Nonetheless, he said, the companies will need to discuss the results with the Food and Drug Administration and the European Medicines Agency before revising the timeline.
An independent data monitoring committee recommended halting the ALSYMPCA study so that patients on placebo can be offered treatment with Alpharadin. The double-blind study enrolled 922 patients with symptomatic castration-resistant hormone-refractory prostate cancer that had spread to the bone. Patients were randomized two to one to receive Alphradin plus standard of care compared with standard of care alone. The varying standard-of-care regimens included steroids, pain killers, ketoconazole, estrogen, and bone-strengthening agents like bisphosphonates.
Median overall survival – the primary end point – was 14 months for patients treated with Alpharadin versus 11.2 months for placebo. Secondary end points of the trial were time to occurrence of skeletal-related events, changes and time to progression in prostate-specific antigen tests and alkaline phosphatase tests, and safety and impact on quality of life. The full data will be presented at a future medical meeting, the companies said.
A Novel Drug Targeted to Patients With End-Stage Disease
If approved, Alpharadin would join a growing field of novel prostate cancer medicines. The drug is targeted to prostate cancer patients at the final stage of the disease when it has spread to the bones. It has flown under the radar compared with some higher-profile new launches in the prostate cancer space, like Dendreon Corp.’s cancer immunotherapy Provenge (sipuleucel-T) and Johnson & Johnson’s Zytiga (abiraterone). But it is expected to be used later in the course of treatment than those drugs, which have also demonstrated a significant survival benefit in prostate cancer patients.
Alpharadin also differs from Amgen Inc.’s bone drug Xgeva (denosumab), which was shown to delay time to symptomatic bone metastases in a post hoc analysis of a phase III trial in castration-resistant prostate cancer patients earlier this year.
Xgeva, a bone-strengthening drug, was approved for prevention of skeletal-related adverse events in patients with bone metastases from solid tumors last year, but the company is hoping to extend labeling to include the prevention of bone metastases. Nonetheless, Xgeva has not shown a benefit on overall survival. Alpharadin, in contrast, is a targeted tumor-cell killer that has a natural affinity for bone metastases. It travels directly to the bone metastases, where the alpha particles kill the cancer cells with minimal effect on surrounding normal cells.
"We believe that this is the mechanism of action that extends life and has delivered this survival benefit," Mr. Kay said.
"On all of these therapies, sadly, patients still progress and in the last year of their life, they develop symptoms of pain, and symptomatic bone metastases are diagnosed," Mr. Kay said. "That is the time for Alpharadin to be prescribed for a survival benefit." Chemotherapy is the current treatment for such patients. Nonetheless, some 50% of patients cannot tolerate chemotherapy or refuse treatment, according to Mr. Kay.
The primary competition would therefore be drugs like docetaxel (Sanofi-Aventis SA’s Taxotere and generics) or Sanofi’s newly launched follow-on chemotherapy Jevtana (cabazitaxel). Both drugs have also shown a survival benefit in prostate cancer patients in phase III clinical trials: 2.4 months for docetaxel in chemotherapy-naive patients and 2.4 months for cabazitaxel in patients already treated with Taxotere.
Nonetheless, Alpharadin has had a benign side effect profile in clinical trials, with similar tolerability to placebo in phase I and II clinical trials, with the exception of constipation. Thus, it could be positioned as a treatment of choice over chemotherapy. Tolerability in the phase III study held up to earlier trials, the company noted, though no details were released.
Although generic versions of Taxotere became available for the first time earlier this year, Mr. Kay told investors on a same-day conference call that the pricing environment remains "very encouraging" in the prostate cancer space. "It is difficult to think we may have a price reimbursement lower than cabazitaxel," he said, noting that the drug is priced at about $48,000 for treatment. Indeed, Jevtana has performed surprisingly well in its first months on the market, although it has significant toxicity. Jevtana generated €82 million in 2010 after launching in the United States in July.