Horizon Therapeutics’ (HZNP) competitor Selecta Biosciences (SELB) reported results phase 2 of SEL-212 (pegadricase plus ImmTOR) which failed to beat Krystexxa in refractory gout patients. SEL-212 achieved a numerically better response rate at 3 and 6 months, but the results failed to reach statistical significance. SEL-212 results confirm its prior efficacy profile which is only moderately better than Krystexxa monotherapy and it does not represent an apples-to-apples comparison as SEL-212 has an unfair advantage of the addition of ImmTOR, Selecta’s immunomodulator, to pegadricase, which is the biologic candidate with the same mechanism of action as Krystexxa (pegloticase).

I believe SEL-212’s phase 2 results further solidify Krystexxa’s likely leading position in the refractory gout market given the emerging and very strong combination data of Krystexxa with approved immunomodulators (mainly methotrexate). I expect the combination to achieve much greater efficacy in the ongoing MIRROR study than SEL-212 will in its phase 3 study against placebo.

SEL-212 fails to significantly differentiate on efficacy and completely fails to differentiate on safety

Selecta’s initial pitch to investors on SEL-212 was not only that it should achieve better efficacy than Krystexxa, but that it will also have a better safety profile. In my article on Horizon last year, I noted this trial may not be relevant because of the MIRROR study where Horizon is studying Krystexxa and methotrexate combo. Not only was this trial not relevant, but it was also damaging to Selecta’s valuation given the primary endpoint failure, and it also turned out that there were no differences between SEL-212 and Krystexxa in the phase 2 study in treatment-related side effects, serious side effects, or infusion reactions.

On the efficacy side, Selecta once again resorted to per-protocol (‘PP’) assessments versus intent-to-treat (‘ITT’) assessments, though, granted, it did report ITT data as well. I will only