December 14, 2011

The Mod Squad

What did Dr. Jen meant by “modified PFS” when he wrote this in his equity research note of last month.

Recall his comments: Topics discussed included the applicable patient population and primary endpoints. Metastatic melanoma patients eligible for the PV-10 trial will likely be those with Stage IIIb, Stage IV M1a, and possibly some with Stage IV M1b. We believe that PV-10 would be more valuable in treating patients with local-regional disease and cutaneous, but not visceral, metastases. A modified PFS, instead of time to progression (TTP), could potentially be the primary endpoint since it is appropriate for demonstrating treatment efficacy. This proposed randomized study could possibly enroll 300 patients with dacarbazine (DTIC) or temozolomide (TMZ) as the comparator group.

PFS, of course, is “progression free survival.” So, it is a time to event endpoint, like overall survival (“OS”). PFS also could be referred to as disease free survival. The “modified” descriptor means the trial only is concerned with the spread of the disease beyond the local area – the local area of the injection site; that is, the local area of the lesion [that has been injected withPV-10]. If the patient had systemic or visceral disease by definition, the endpoint would be PFS or, most likely, OS. Since the patients that are contemplated for treatment in the Phase 3 trial would have local disease, the trial only measures the spread or, mostly in the case of PV-10, the lack of spread of the disease. Therefore, the disease of this patient population is, by definition, not systemic; thus, PFS is modified in the sense that it applies only to the local disease.

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