In a well-researched, recent post, Patrick O’Leary addresses the FDA’s efficacy requirements as applied to an old drug, Acthar (corticotropin), that was first approved in 1952 and granted an orphan designation in 2010 for the treatment of infantile spasms. The initial approval therefore occurred before the Drug Amendments of 1962, which instituted a “new” statutory requirement of efficacy (more on this below). O’Leary points out that Acthar’s “grandfather” status does not entirely exempt it from the FDA’s efficacy requirements, and that the drug did survive an efficacy evaluation under the DESI program. But how effective is Acthar?
Neither O’Leary nor the New York Times article on which his post is based dig very far into the clinical trial data accepted by the FDA as supporting the efficacy of the drug as a treatment for infantile spasms, and I was curious to know what the evidence says about Acthar in this regard. Clinical trial data is presented—or perhaps more accurately, “buried”—in Section 14 of a drug’s FDA-approved label; in the case of “H.P. Acthar Gel” (NDA 022432), that label can be found here. What does the clinical trial data reveal? The section is brief, just half a page, and notes that of “[t]hirteen of 15 patients (86.7%) responded to Acthar Gel as compared to 4 of 14 patients (28.6%) given prednisone (p<0.002).” Nonresponders were then given the other treatment, with the following results. “Seven of 8 patients (87.5%) responded to H.P Acthar Gel after not responding to prednisone,” while “[o]ne of the 2 patients (50%) responded to the prednisone treatment after not responding to Acthar.” As the p-value (0.002) indicates, the first figures, at least, are statistically significant. These figures were also better than I expected: 86.7% efficacy with Acthar does seem much better than 28.6% efficacy with prednisone. Continue reading