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Dendreon Presents Additional Provenge Safety Data


This new presentation ought to help debunk arguments against the validity of Provenge trials.

In July 2010, shares in Dendreon (DNDN) started jumping around unexpectedly. It wasn't too long before the reason landed in my inbox: A 27-page pseudo-scientific screed attacking Dendreon's prostate cancer drug Provenge.

One of the intriguing things about this document is nobody claimed authorship. In fact, if you're enough of a Provenge obsessive to have read the Freedom of Information Act responses shared by the prostate cancer user group Care To Live, you'd see about a hundred pages of back and forth between the Centers for Medicare and Medicaid Services (CMS) and an attorney representing the authors. The authors were trying to figure out how to submit the article to CMS to derail Provenge reimbursement without losing their anonymity. (An odd footnote to the story is authorship of the paper was revealed during the CMS's hearing on Provenge. Authorship was claimed during oral public testimony by the research director of a small equities broker who was very bearish on Provenge approval and apparently still a little miffed they got it wrong.)

I'd never write about this absurd screed again except I keep running into investors who keep quoting its utterly false perspective on Provenge. In sum, the screed argues the survival benefit seen in three Phase III Provenge trials is not a survival advantage at all. It reflects a survival detriment to the control arm because the placebo process does not return all collected immune cells to the patient. It goes into great detail about how "robbing" men of these cells hastens their death.

This is ridiculous on many levels. First, the Provenge process removed less than 1% of immune cells from these men. One-third of those cells were returned to placebo patients on the same schedule as patients who received Provenge.

Second, some 65-75% of the men in the control arm got most of the rest of those cells back when they crossed over to the frozen version of Provenge. Data released in 2011 suggested this frozen form had its own survival advantage over placebo.

Third, chemotherapy drugs traditionally are very hard on patients' immune systems. With most chemotherapy drugs, doctors have to give supportive drugs to restore immune system cell to normal levels. Hospitalizations from infections and high fevers are common with chemotherapy treatment. Patients on chemo are additionally susceptible to fungal infections, colds, and viruses. If Provenge indeed represents dramatic harm to a patient's immune system, one would expect to see similar outcomes in its clinical trials. None of this was seen in the Provenge trials, again contradicting the screed's claim that the patients in the control arm were being harmed via significant depletion of their immune cells.

Finally, there exists no clinical data suggesting removing such small quantities (about 0.15% in each of the three aphereses, or less than 1% total) has any adverse effect. The screed cites some literature, but none of it contains comparable data or was successfully reproduced by other studies. Furthermore, even the elderly men in the Provenge trial are going to regenerate these immune cells quickly.

Dendreon presented data at this week's American Urological Association (AUA) meeting with additional information from the clinical trial pertinent to this issue. The key slide is shown below, used with permission:

As is common in prostate cancer trials, the Provenge Phase III trials collected immune system and blood component data. The graph on the left shows how patients' white blood cells ("WBCs") varied during the trial between Provenge (sipuleucel-T) and control patients. You can see by the graph there is no important difference. The chart on the right looks at lymphocytes, a more specific measure of immune system cells, and also indicates no important differences between the Provenge and control arms. Importantly, the values for WBCs and lymphocytes of patients in either the Provenge or control arms never go outside the blue bands on the chart corresponding to normal levels.

Hopefully, Dendreon's public presentation of these data will make this silly argument against the validity of the Provenge trials go away.
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