PRTX-100 (Staphylococcal Protein A)

E. Bernton et al. presented: "A Phase 1, Randomized, Double-Blind, Placebo-Controlled Multiple-Dose Study of Intravenous Staphylococcal Protein A in Patients with Active Rheumatoid Arthritis On Methotrexate: Safety, Pharmacokinetics and Efficacy" (Abstract No. 833). "Results of this pilot study support further clinical trials of PRTX-100 at doses of 1.5 _g/kg and higher." "The primary disease activity response endpoint was the number of patients with a DAS28-CRP _3.2 at Week 6" - and this endpoint was "met by 3/29 PRTX-100 and 0/8 placebo patients". "PRTX-100 elicited anti-drug antibodies (ADAs) in the majority of patients but the incidence or titer of ADAs was not dose-dependent."

As I had been part in testing immunoadsorption, I'm not too confident in PRTX-100. Anti-drug antibodies in the majority of patients and a small effect on 10% of the patients make it hard to believe that we'll see a working drug added to existing drugs. But maybe it's still too early for skepticism.