Ardea Biosciences, Inc announced additional positive results from a recently completed phase-2a study of RDEA594, its lead product candidate for the treatment of hyperuricemia and gout, as well as additional positive results from the second panel of a phase-1 drug-drug interaction and pharmacodynamic study of RDEA594 in combination with febuxostat (Uloric, Takeda Pharmaceutical Company Limited; Adenuric, Ipsen and Menarini).

"The impressive reduction in serum urate observed when RDEA594 and febuxostat or allopurinol are co-administered indicate that these oral agents with complementary mechanisms may be able to produce reductions in serum urate previously achieved only with intravenous therapy," said Mark Genovese, professor of medicine and co-chief of the Division of Immunology and Rheumatology at Stanford University Medical Center and a member of Ardea's scientific advisory board. "I look forward to studying these combinations in patients with advanced disease."

The combination of RDEA594 and allopurinol reduced serum urate (sUA) levels an additional 24 per cent compared to allopurinol alone in the second cohort of a phase-2a proof-of-concept study evaluating the sUA lowering effect, safety and tolerability of combining RDEA594 and allopurinol in gout patients with hyperuricemia (sUA levels of at least 9 mg/dL). Patients in this cohort received 300 mg of allopurinol once daily (QD) for one week, followed by the addition of 200 mg of RDEA594 or placebo QD for the second week, and 400 mg of RDEA594 or placebo QD in addition to allopurinol for the third and final week.

After one week on allopurinol alone, sUA levels were reduced by 39 percent to a mean of 6.3 mg/dL, with 50 per cent of patients responding. Response was defined as achieving a target sUA level of less than 6.0 mg/dL. Adding 200 mg of RDEA594 QD to allopurinol for an additional week produced a 48 percent reduction in sUA from baseline with all patients responding. Increasing the dose to 400 mg of RDEA594 QD for an additional week resulted in a 54 per cent reduction of sUA from a baseline of 10.2 mg/dL to a mean of 4.6 mg/dL, which represents a 24 per cent reduction in sUA levels from levels achieved on allopurinol alone. All patients responded and 80 percent of patients achieved sUA levels below 5 mg/dL. The combination of RDEA594 and allopurinol was well tolerated and no significant laboratory abnormalities were reported. In the previously reported first cohort of this study, RDEA594 produced significant reductions in sUA levels, was effective in patients with mild to moderate renal impairment, and was well tolerated as a single agent in gout patients with hyperuricemia.

In the second panel of a drug-drug interaction and pharmacodynamic study of RDEA594 with febuxostat in healthy volunteers, 400 mg of RDEA594 QD and 40 mg of febuxostat QD reduced mean sUA levels by 49 and 45 per cent, respectively, when used alone. The combination of RDEA594 with febuxostat resulted in approximately a 70 per cent mean reduction in sUA levels compared to baseline, with intraday reductions of over 80 per cent, reaching mean sUA levels of 1.2 mg/dL. These results compare favourably to the mean serum urate reductions previously reported with the first dosing group of approximately 60 per cent from baseline when 200 mg of RDEA594 QD was administered in combination with 40 mg of febuxostat QD for 7 days. The combination of RDEA594 and febuxostat was well tolerated, with Grade 2 elevations of liver enzymes associated with febuxostat treatment as the only significant laboratory abnormalities.

"These results demonstrate the potential to use RDEA594 in combination with the most widely prescribed class of gout medications to achieve greater levels of serum urate reduction than can be achieved using a xanthine oxidase inhibitor alone," said Barry D Quart, Ardea's president and chief executive officer. "Given its complementary mechanism of action, we believe that RDEA594 is well positioned to meet a significant unmet medical need for patients who do not adequately respond to, or who are intolerant to, currently available gout medications."

Our most advanced product candidate, RDEA594, is a selective inhibitor of URAT1, a transporter in the kidney that regulates uric acid excretion from the body.

Ardea Biosciences, of San Diego, California, is a biotechnology company focused on the development of small-molecule therapeutics for the treatment of gout, cancer and human immunodeficiency virus (HIV).