Washington Research Group
Too Preliminary to Tell for Geron’s Telomerase Vaccine
Gregory Frykman, M.D.
Cancer vaccines have held promise for several decades only to go on to disappoint patients, clinicians and
investors time and time again. Although our knowledge of the immune system continues to grow, our ability to
transform this into clinical utility remains limited. Tantalizing results in a few individual patients in virtually
every vaccine trial encourage new and "better" approaches, but in a population of patients, upon which the FDA
requires an investigational vaccine to be tested, bona fide clinical benefit has yet to be demonstrated. In fact,
miserable failures are much more common.
Geron Corporation’s (GERN 5.51)² announcement yesterday about early successes seen in prostate cancer for
its anti-telomerase vaccine is an example of a company announcing seductive but premature tumor vaccine
results. Indeed, at face value the results are interesting and may be eventually proven in large-scale randomized
controlled clinical trials. However, when yesterday's data are viewed against the backdrop of numerous small
tumor vaccine trials combined with the very early place that Geron’s program is in the conventional cancer
therapeutic development paradigm, what stands out is how little of importance was presented.
Briefly, results for only 50% of their 24-patient phase 1 trial were reported; conventional development requires
at least one phase 3 study involving several hundred to over 1000 patients and is unlikely to be completed at
least 2-3 years. The endpoint of such a trial would be either survival or symptomatic improvement, neither of
which were discussed in the conference call. Moreover, Geron essentially ignored the effect of its vaccine on
prostate specific antigen (PSA) even though PSA is generally regarded as a marker useful in early drug
development in prostate cancer. Lastly, the recent failure of atrasentan -- also intended to decrease and/or delay
the onset of metastatic prostate cancer -- should provide ample cause for concern. |
