BioCryst Pharmaceuticals, Inc. (NASDAQ:BCRX) today announced long-term results from the extension phase of its randomized Phase 2b study of BCX4208 added to allopurinol in patients with gout who had failed to reach the serum uric acid (sUA) therapeutic goal of <6 mg/dL on allopurinol alone. The results of this 24-week, blinded safety extension confirm that BCX4208 was generally safe and well-tolerated, and sustained sUA control over time. Patients generated healthy immune responses to a vaccine challenge at 16 or 20 weeks of BCX4208 treatment. Following the successful outcome of this 24-week analysis, BioCryst is preparing for end of Phase 2 regulatory discussions to take place in the coming months. In the original 12-week study, 279 patients were randomized and 160 patients entered the extension phase. Patients continued their blinded, randomized therapy of BCX4208 at doses of 5 mg, 10 mg, 20 mg, 40 mg and placebo once-daily. Allopurinol 300 mg once-daily was administered in all study arms. This longer-term safety profile of BCX4208 is consistent with the 12-week primary analysis results originally reported in October 2011. BCX4208 added to allopurinol was generally safe and well-tolerated at all doses studied, and responses to vaccines indicated healthy immune function. The types and rates of adverse events through 24 weeks, including infections, were similar between the groups treated with BCX4208 and placebo. No opportunistic or unusual infections were observed. The previously observed lymphocyte plateau reached by 12 weeks of treatment remained unchanged in the 5 mg, 10 mg and 20 mg BCX4208 arms through 24 weeks. The 40 mg study arm met a protocol-defined cohort stopping rule based on the number of withdrawals for CD4+ cell counts, and this arm was discontinued after week 24. No patients from the placebo, 5 mg or 10 mg cohorts discontinued study drug for confirmed reductions of lymphocyte or CD4+ cell counts below certain protocol-specified thresholds; through 24 weeks, a total of four patients were discontinued from the 20 mg group and eleven patients from the 40 mg group for reductions in CD4+ cell counts.