Selecta Biosciences Inc. announced positive topline results from the Phase 3 DISSOLVE I & II placebo controlled randomized clinical trials to determine safety and efficacy of two different dose levels of SEL-212 in adult patients with chronic refractory gout. The DISSOLVE I (the "US Study") met its primary endpoint, with 56% of patients receiving monthly doses of SEL-212 at 0.15 mg/kg achieving a response (defined as achievement and maintenance of reduction in serum urate (SU) <6mg/dL for at least 80% of the time during month six). The DISSOLVE II (the "Global Study") also met its primary endpoint, with 47% receiving monthly doses of SEL-212 at 0.15 mg/kg achieving a response.

SEL-212 is a combination of Selecta's ImmTOR immune tolerance platform and a therapeutic uricase enzyme (pegadricase). DISSOLVE I had a statistically significant higher response rate of SEL-212 during month six: 56% and 48% of patients randomized to receive SEL-212 at the high dose of 0.15 mg/kg (p<0.0001) and the low dose of 0.1 mg/kg (p<0.0001) of ImmTOR, respectively, versus 4% of patients randomized to receive the placebo reached the primary endpoint. DISSOLVE II also had a statistically significant higher response rate of SEL-212 during month six: 47% and 41% of patients randomized to receive SEL-212 at high dose (p=0.0002) and low dose (p=0.0015) of ImmTOR, respectively, versus 12% of patients randomized to receive the placebo reached the primary endpoint.

Statistically significant higher response rate in patients 50 years and older at the high dose in DISSOLVE I and II: 65% and 47% of DISSOLVE I patients randomized to receive SEL-212 at the high dose (p<0.0001) and the low dose (p<0.0001) of ImmTOR, respectively, versus 5% of patients randomized to receive the placebo reached the primary endpoint; 48% and 45% of DISSOLVE II patients randomized to receive SEL-212 the high dose (p=0.0017) and low dose (p=0.0044) of ImmTOR, respectively, versus 14% of patients randomized to receive the placebo reached the primary endpoint. Significant and clinically meaningful overall reduction of 69% in mean SU levels in patients randomized to receive SEL-212 at 0.15mg/kg in DISSOLVE I, as compared with placebo: Serum urate levels were reduced by an average of 5.3 mg/dL (computed by subtracting baseline SU from mean SU during the treatment period 6) for patients treated with both doses of SEL-212 (p<0.001) compared to 0.3 mg/dL increase in patients receiving placebo. SEL-212 was observed to have a favorable safety profile and was well-tolerated across both doses of ImmTOR: The adverse events (AEs) identified in the trials were expected, including mild to moderate stomatitis which was seen in 3.4% of the low dose group and 9.2% of the high dose group versus 0% in placebo and a greater number of infusion reactions at 24 hours and 1 hour after drug administration in both treatment groups versus placebo.

Treatment-related serious AEs were observed in six patients, including two cases of anaphylaxis and one gout flare in both the high and low dose treatment groups. Only 4.5% of patients receiving the low dose of SEL-212 and 3.4% at the high dose of SEL-212 had infusion reactions, evaluated 1 h post dose. All infusion reactions occurred within the first three infusions, and each occurred during infusions and completely resolved with infusion halt and symptomatic treatment.

There was one death in the six-month extension phase of the trial, which was caused by a motor vehicle accident unrelated to the study drug. There was no difference in gout flares when both treatment groups were compared to placebo.