According to their website, Discovery’s Edge is the Mayo Clinic’s online research magazine that is designed to communicate the story of scientists and researchers who are bringing treatments and improved care to patients and also reports on “works–in–progress.” Through this publication, Mayo investigators studying immunotherapy for aggressive prostate cancer reported over the past weekend that a combination therapy dramatically reduced tumor size to make surgery possible for two patients whose prostate cancer had been previously considered inoperable. While preliminary, Mayo reported that the results were significant enough for future research.
As noted in our recent articles, investors have been “irrationally exuberant” towards biotechnology companies working in the field of prostate cancer – even those in the early stages of development. In keeping with this theme, the Mayo news drove shares of Medarex, Inc. (MEDX) up more than 20% on Monday morning with significant volume, as the immunotherapy referenced in the investigator-sponsored study involved the company’s ipilimumab product candidate. Ipilimumab is a fully human antibody that binds to CTLA-4, a molecule on T-cells that plays a critical role in regulating natural immune responses.
Enough has been written about the fact that the positive results were demonstrated in a mere two prostate cancer patients and the lack of information provided in the Discovery’s Edge publication (see Associated Press article), so I won’t belabor the point.
It is interesting to note, however, that Medarex included a summary of the Mayo report from two patients under the news section of the company’s website, yet the company didn’t report Phase 2 study results with ipilimumab in aggressive prostate cancer that were reported by researchers at Memorial Sloan-Kettering Cancer Center (MSKCC) during the Annual Meeting of the American Society of Clinical Oncology (ASCO) held May 29-June 2, 2009. See abstract #5138 titled “Initial phase II experience of ipilimumab (IPI) alone and in combination with radiotherapy (XRT) in patients with metastatic castration-resistant prostate cancer (mCRPC).”
In the MSKCC study reported at ASCO, 45 patients with mCRPC received ipilimumab in 3 groups:
- ipilimumab alone, n=16
- ipilimumab + XRT, n=15, in chemotherapy naïve
- ipilimumab + XRT, n=14, in chemotherapy experienced patients
In the study, PSA declines ≥ 50% were seen in 10 of 45 (22%) patients. Only one patient from Group 1 (ipilimumab alone) demonstrated a PSA ≤ 0.05 ng/ml and complete resolution of bone, nodal and prostate lesions that continued for 54+ and 84+ weeks, respectively.
While Medarex issued a press release on May 31, 2009 summarizing the results from three Phase 2 studies of ipilimumab in metastatic melanoma at ASCO, there was no such communication regarding the Phase 2 results from MSKCC in prostate cancer that certainly don’t live up to the hype generated by the results from the Mayo Clinic report.